Week 4 Quiz

Describe the structure and function of an intervertebral disc.

An intervertebral disc fills in the space between adjacent vertebrae, where it provides padding and weight-bearing ability, and allows for movements between the vertebrae. It consists of an outer anulus fibrosus and an inner nucleus pulposus. The anulus fibrosus strongly anchors the adjacent vertebrae to each other, and the high water content of the nucleus pulposus resists compression for weight bearing and can change shape to allow for vertebral column movements.

View this video to review the two processes that give rise to the bones of the skull and body. What are the two mechanisms by which the bones of the body are formed and which bones are formed by each mechanism?

Bones on the top and sides of the skull develop when fibrous membrane areas ossify (convert) into bone. The bones of the limbs, ribs, and vertebrae develop when cartilage models of the bones ossify into bone.

Short

Cube-like shape, approximately equal in length, width, and thickness Provide stability, support, while allowing for some motion Carpals, tarsals

If the articular cartilage at the end of one of your long bones were to degenerate, what symptoms do you think you would experience? Why?

If the articular cartilage at the end of one of your long bones were to deteriorate, which is actually what happens in osteoarthritis, you would experience joint pain at the end of that bone and limitation of motion at that joint because there would be no cartilage to reduce friction between adjacent bones and there would be no cartilage to act as a shock absorber.

Bones also protect internal organs from injury by covering or surrounding them.

For example, your ribs protect your lungs and heart, the bones of your vertebral column (spine) protect your spinal cord, and the bones of your cranium (skull) protect your brain

Why are osteocytes spread out in bone tissue?

Formation of osteoid spreads out the osteoblasts that formed the ossification centers.

Define the classes of ribs.

Ribs are classified based on if and how their costal cartilages attach to the sternum. True (vertebrosternal) ribs are ribs 1-7. The costal cartilage for each of these attaches directly to the sternum. False (vertebrochondral) ribs, 8-12, are attached either indirectly or not at all to the sternum. Ribs 8-10 are attached indirectly to the sternum. For these ribs, the costal cartilage of each attaches to the cartilage of the next higher rib. The last false ribs (11-12) are also called floating (vertebral) ribs, because these ribs do not attach to the sternum at all. Instead, the ribs and their small costal cartilages terminate within the muscles of the lateral abdominal wall.

Watch this animation to see what it means to "slip" a disk. Watch this second animation to see one possible treatment for a herniated disc, removing and replacing the damaged disc with an artificial one that allows for movement between the adjacent certebrae. How could lifting a heavy object produce pain in a lower limb?

Lifting a heavy object can cause an intervertebral disc in the lower back to bulge and compress a spinal nerve as it exits through the intervertebral foramen, thus producing pain in those regions of the lower limb supplied by that nerve.

where does blood cell production take place?

Most of your blood cells are made in your bone marrow. The process by which blood cells are made is called haemopoiesis. As an infant, haemopoiesis takes place at the centre of all bones. In later life, it is limited to the hips, ribs and breastbone (sternum).

Osteoporosis is a common age-related bone disease in which bone density and strength is decreased. Watch this video to get a better understanding of how thoracic vertebrae may become weakened and may fractured due to this disease. How may vertebral osteoporosis contribute to kyphosis?

Osteoporosis causes thinning and weakening of the vertebral bodies. When this occurs in thoracic vertebrae, the bodies may collapse producing kyphosis, an enhanced anterior curvature of the thoracic vertebral column.

Describe the effects caused when the parathyroid gland fails to respond to calcium bound to its receptors.

Under "normal" conditions, receptors in the parathyroid glands bind blood calcium. When the receptors are full, the parathyroid gland stops secreting PTH. In the condition described, the parathyroid glands are not responding to the signal that there is sufficient calcium in the blood and they keep releasing PTH, which causes the bone to release more calcium into the blood. Ultimately, the bones become fragile and hypercalcemia can result.

posterior cranial fossa

deepest and most posterior cranial fossa; extends from the petrous ridge to the occipital bone It contains the cerebellum of the brain. The posterior fossa is bounded anteriorly by the petrous ridges, while the occipital bone forms the floor and posterior wall. It is divided at the midline by the large foramen magnum ("great aperture"), the opening that provides for passage of the spinal cord.

endosteum

delicate membranous lining of a bone's medullary cavity-(end- = "inside"; oste- = "bone"), where bone growth, repair, and remodeling occur.

compact bone

dense osseous tissue that can withstand compressive forces- The walls of the diaphysis are composed of dense and hard

Bone tissue can be described as ________.

dense, hard connective tissue

An individual with very low levels of vitamin D presents themselves to you complaining of seemingly fragile bones. Explain how these might be connected.

Vitamin D is required for calcium absorption by the gut. Low vitamin D could lead to insufficient levels of calcium in the blood so the calcium is being released from the bones. The reduction of calcium from the bones can make them weak and subject to fracture.

long bone has two parts

diaphysis and epiphysis

osteoporosis

disease characterized by a decrease in bone mass; occurs when the rate of bone resorption exceeds the rate of bone formation, a common occurrence as the body ages---Notice how this is different from Paget's disease. In Paget's disease, new bone is formed in an attempt to keep up with the resorption by the overactive osteoclasts, but that new bone is produced haphazardly. In fact, when a physician is evaluating a patient with thinning bone, he or she will test for osteoporosis and Paget's disease (as well as other diseases). Osteoporosis does not have the elevated blood levels of alkaline phosphatase found in Paget's disease.

fetal development

a framework is laid down that determines where bones will form. This framework is a flexible, semi-solid matrix produced by chondroblasts and consists of hyaluronic acid, chondroitin sulfate, collagen fibers, and water. As the matrix surrounds and isolates chondroblasts, they are called chondrocytes. Unlike most connective tissues, cartilage is avascular, meaning that it has no blood vessels supplying nutrients and removing metabolic wastes. All of these functions are carried on by diffusion through the matrix. This is why damaged cartilage does not repair itself as readily as most tissues dochildhood growth and development, bone forms on the cartilaginous matrix. By the time a fetus is born, most of the cartilage has been replaced with bone. Some additional cartilage will be replaced throughout childhood, and some cartilage remains in the adult skeleton.

The area of a bone where the nutrient foramen passes forms what kind of bone marking?

a hole

Wolff's law, which describes the effect of mechanical forces in bone modeling/remodeling, would predict that ________

a right-handed pitcher will have thicker bones in his right arm compared to his left.

A typical lumbar vertebra has ________.

a short, rounded spinous process

intramembranous ossification

begins in utero during fetal development and continues on into adolescence. At birth, the skull and clavicles are not fully ossified nor are the sutures of the skull closed. This allows the skull and shoulders to deform during passage through the birth canal. The last bones to ossify via intramembranous ossification are the flat bones of the face, which reach their adult size at the end of the adolescent growth spurt.

Bones grow in diameter due to bone formation ________.

beneath the periosteum

fracture hematoma

blood clot that forms at the site of a broken bone--six to eight hours after the fracture,---The disruption of blood flow to the bone results in the death of bone cells around the fracture

projection

bone markings where part of the surface sticks out above the rest of the surface, where tendons and ligaments an area of a bone that projects above the surface of the bone. These are the attachment points for tendons and ligaments. In general, their size and shape is an indication of the forces exerted through the attachment to the bone.

irregular bone

bone of complex shape; protects internal organs from compressive forces.These bones tend to have more complex shapes, like the vertebrae that support the spinal cord and protect it from compressive forces. Many facial bones, particularly the ones containing sinuses, are classified as irregular bones.

osseous tissue

bone tissue; a hard, dense connective tissue that forms the structural elements of the skeleton - structure of the body.supports the body facilitates movement protects internal organs produces blood cells stores and releases minerals and fat

skeleton

bones of the body

vertebral arch

bony arch formed by the posterior portion of each vertebra that surrounds and protects the spinal cord

dens

bony projection (odontoid process) that extends upward from the body of the C2 (axis) vertebra-- The dens joins with the inner aspect of the anterior arch of the atlas, where it is held in place by transverse ligament.

mylohyoid line

bony ridge located along the inner (medial) surface of the mandibular body -- muscle forms floor of oral cavity attaches to mylohyoid lines on both sides of mandible

hard palate

bony structure that forms the roof of the mouth and floor of the nasal cavity, formed by the palatine process of the maxillary bones and the horizontal plate of the palatine bones

maxillary sinus

air-filled space located with each maxillary bone; largest of the paranasal sinuses

sphenoid sinus

air-filled space located within the sphenoid bone; most posterior of the paranasal sinuses-a single, midline sinus. It is located within the body of the sphenoid bone, just anterior and inferior to the sella turcica, thus making it the most posterior of the paranasal sinuses.

frontal sinus

air-filled space within the frontal bone; most anterior of the paranasal sinuses- This irregular space may be divided at the midline into bilateral spaces, or these may be fused into a single sinus space. The frontal sinus is the most anterior of the paranasal sinuses.

The paranasal sinuses are ________.

air-filled spaces found within the frontal, maxilla, sphenoid, and ethmoid bones only

appendicular skeleton

all bones of the upper and lower limbs, plus the girdle bones that attach each limb to the axial skeleton -- 126 bones in appendicular skeleton of an adult, bones of appendicular skeleton covered

sacral promontory

anterior lip of the base (superior end) of the sacrum-Lateral to this is the roughened auricular surface, which joins with the ilium portion of the hipbone to form the immobile sacroiliac joints of the pelvis.

anterior arch

anterior portion of the ring-like C1 (atlas) vertebra

sacrococcygeal curve

anteriorly concave curvature formed by the sacrum and coccyx; a primary curve of the vertebral column

thoracic curve

anteriorly concave curvature of the thoracic vertebral column region; a primary curve of the vertebral column

In a compound fracture, ________.

broken bone pierces the skin

fracture

broken bone--It will heal whether or not a physician resets it in its anatomical position. If the bone is not reset correctly, the healing process will keep the bone in its deformed position.

The primary curvatures of the vertebral column ________.

are remnants of the original fetal curvature

True ribs are ________.

attached via their costal cartilage directly to the sternum

orthopedist

doctor who specializes in diagnosing and treating musculoskeletal disorders and injuries - treat w/ mediations, exercises, braces, and other devies, surgery ortho- straight, paed- child .--> orthopedics --- straightening of the child-- pediatric to geriatric-- orthopediists have performed prenantal surgery to correct spina bifieda- congenital defect- neural canal in the spine of the fetus fails to close completely during embryologic development

styloid process

downward projecting, elongated bony process located on the inferior aspect of the skull —Posterior to the mandibular fossa on the external base of the skull is an elongated, downward bony projection called the styloid process, so named because of its resemblance to a stylus (a pen or writing tool). This structure serves as an attachment site for several small muscles and for a ligament that supports the hyoid bone of the neck.

perpendicular plate of the ethmoid bone

downward, midline extension of the ethmoid bone that forms the superior portion of the nasal septum --- upper portion of the nasal septum

Which of the following represents the correct sequence of zones in the epiphyseal plate?

calcification, maturation, proliferation, reserved

Which of the following is most likely to be released when blood calcium levels are elevated?

calcitonin

With respect to their direct effects on osseous tissue, which pair of hormones has actions that oppose each other?

calcitonin and parathyroid hormone

(singular = canaliculus) channels within the bone matrix that house one of an osteocyte's many cytoplasmic extensions that it uses to communicate and receive nutrients

canaliculi

Which of the following can be found in areas of movement?

cartilage

semi-rigid connective tissue found on the skeleton in areas where flexibility and smooth surfaces support movement

cartilage

Bisphosphonates

drugs that decrease the activity of osteoclasts, are often used in the treatment of Paget's disease. However, in a small percentage of cases, bisphosphonates themselves have been linked to an increased risk of fractures because the old bone that is left after bisphosphonates are administered becomes worn out and brittle. Still, most doctors feel that the benefits of bisphosphonates more than outweigh the risk; the medical professional has to weigh the benefits and risks on a case-by-case basis. Bisphosphonate treatment can reduce the overall risk of deformities or fractures, which in turn reduces the risk of surgical repair and its associated risks and complications.

bones

dynamic and complex organs that serve a number of important functions, maintain homeostasis

Sesamoid

Small and round; embedded in tendons Protect tendons from compressive forces Patellae

curvatures of the vertebral column

The adult vertebral column does not form a straight line, but instead has four curvatures along its length (see Figure). These curves increase the vertebral column's strength, flexibility, and ability to absorb shock. When the load on the spine is increased, by carrying a heavy backpack for example, the curvatures increase in depth (become more curved) to accommodate the extra weight. They then spring back when the weight is removed. The four adult curvatures are classified as either primary or secondary curvatures. Primary curves are retained from the original fetal curvature, while secondary curvatures develop after birth.

Describe the anterior, middle, and posterior cranial fossae and their boundaries, and give the midline structure that divides each into right and left areas.

The anterior cranial fossa is the shallowest of the three cranial fossae. It extends from the frontal bone anteriorly to the lesser wing of the sphenoid bone posteriorly. It is divided at the midline by the crista galli and cribriform plates of the ethmoid bone. The middle cranial fossa is located in the central skull, and is deeper than the anterior fossa. The middle fossa extends from the lesser wing of the sphenoid bone anteriorly to the petrous ridge posteriorly. It is divided at the midline by the sella turcica. The posterior cranial fossa is the deepest fossa. It extends from the petrous ridge anteriorly to the occipital bone posteriorly. The large foramen magnum is located at the midline of the posterior fossa.

Define the ligaments of the vertebral column.

The anterior longitudinal ligament is attached to the vertebral bodies on the anterior side of the vertebral column. The supraspinous ligament is located on the posterior side, where it interconnects the thoracic and lumbar spinous processes. In the posterior neck, this ligament expands to become the nuchal ligament, which attaches to the cervical spinous processes and the base of the skull. The posterior longitudinal ligament and ligamentum flavum are located inside the vertebral canal. The posterior longitudinal ligament unites the posterior sides of the vertebral bodies. The ligamentum flavum unites the lamina of adjacent vertebrae.

Use this tool to identify the bones, intervertebral discs, and ligaments of the vertebral column. The thickest portions of the anterior longitudinal ligament and the supraspinous ligament are found in which regions of the vertebral column?

The anterior longitudinal ligament is thickest in the thoracic region of the vertebral column, while the supraspinous ligament is thickest in the lumbar region.

Define and list the bones that form the brain case or support the facial structures.

The brain case is that portion of the skull that surrounds and protects the brain. It is subdivided into the rounded top of the skull, called the calvaria, and the base of the skull. There are eight bones that form the brain case. These are the paired parietal and temporal bones, plus the unpaired frontal, occipital, sphenoid, and ethmoid bones. The facial bones support the facial structures, and form the upper and lower jaws, nasal cavity, nasal septum, and orbit. There are 14 facial bones. These are the paired maxillary, palatine, zygomatic, nasal, lacrimal, and inferior nasal conchae bones, and the unpaired vomer and mandible bones.

Discuss the processes by which the brain-case bones of the skull are formed and grow during skull enlargement.

The brain-case bones that form the top and sides of the skull are produced by intramembranous ossification. In this, mesenchyme from the sclerotome portion of the somites accumulates at the site of the future bone and differentiates into bone-producing cells. These generate areas of bone that are initially separated by wide regions of fibrous connective tissue called fontanelles. After birth, as the bones enlarge, the fontanelles disappear. However, the bones remain separated by the sutures, where bone and skull growth can continue until the adult size is obtained.

Identify the major sutures of the skull, their locations, and the bones united by each.

The coronal suture passes across the top of the anterior skull. It unites the frontal bone anteriorly with the right and left parietal bones. The sagittal suture runs at the midline on the top of the skull. It unites the right and left parietal bones with each other. The squamous suture is a curved suture located on the lateral side of the skull. It unites the squamous portion of the temporal bone to the parietal bone. The lambdoid suture is located on the posterior skull and has an inverted V-shape. It unites the occipital bone with the right and left parietal bones.

In terms of origin and composition, what are the differences between an internal callus and an external callus?

The internal callus is produced by cells in the endosteum and is composed of a fibrocartilaginous matrix. The external callus is produced by cells in the periosteum and consists of hyaline cartilage and bone.

paranasal sinuses

cavities within the skull that are connected to the conchae that serve to warm and humidify incoming air, produce mucus, and lighten the weight of the skull; consist of frontal, maxillary, sphenoidal, and ethmoidal sinuses-(paranasal = "next to nasal cavity") and are lined with nasal mucosa. They serve to reduce bone mass and thus lighten the skull, and they also add resonance to the voice. This second feature is most obvious when you have a cold or sinus congestion. These produce swelling of the mucosa and excess mucus production, which can obstruct the narrow passageways between the sinuses and the nasal cavity, causing your voice to sound different to yourself and others. This blockage can also allow the sinuses to fill with fluid, with the resulting pressure producing pain and discomfort.

osteoblast

cell responsible for forming new bone.nd is found in the growing portions of bone, including the periosteum and endosteum. Osteoblasts, which do not divide, synthesize and secrete the collagen matrix and calcium salts.

osteoclast

cell responsible for resorbing bone. new tissue is constantly formed,old, injured, or unnecesaary bone is dissolved for repair or for calcium release. Breakdone - found in bone surfaces are multinucleated and originate from monocytes and macrophages, two types of white blood cells not from osteogenic cells. Breaks down old bone while osteoblasts are continually forming new bone. Ongoing balance between osteoblasts and osteoclasts reponsible for contact but subtle rehspaing of the bone. bone cells,t ehri functions and loations.

axial skeleton

central, vertical axis of the body, including the skull, vertebral column, and thoracic cage

middle cranial fossa

centrally located cranial fossa that extends from the lesser wings of the sphenoid bone to the petrous ridge -

ossification center

cluster of osteoblasts found in the early stages of intramembranous ossification--The process begins when mesenchymal cells in the embryonic skeleton gather together and begin to differentiate into specialized cells (Figurea). Some of these cells will differentiate into capillaries, while others will become osteogenic cells and then osteoblasts. Although they will ultimately be spread out by the formation of bone tissue, early osteoblasts appear in a cluster

external callus

collar of hyaline cartilage and bone that forms around the outside of a fracture --espectively, around the outside of the break (Figureb). This stabilizes the fracture.

epiphyseal line

completely ossified remnant of the epiphyseal plate andBones continue to grow in length until early adulthood. The rate of growth is controlled by hormones, which will be discussed later. When the chondrocytes in the epiphyseal plate cease their proliferation and bone replaces the cartilage, longitudinal growth stops.

206 bones- skeleton

compose adult skeleton are divided into five categories based on their shapes. Their shapes and functions are related such that each categorical shape of bone has a distinct function

hypercalcemia

condition characterized by abnormally high levels of calcium---a condition characterized by abnormally high levels of calcium, the nervous system is underactive, which results in lethargy, sluggish reflexes, constipation and loss of appetite, confusion, and in severe cases, coma.

hypocalcemia

condition characterized by abnormally low levels of can have an adverse effect on a number of different body systems including circulation, muscles, nerves, and bone. Without adequate calcium, blood has difficulty coagulating, the heart may skip beats or stop beating altogether, muscles may have difficulty contracting, nerves may have difficulty functioning, and bones may become brittle. The causes of hypocalcemia can range from hormonal imbalances to an improper diet. Treatments vary according to the cause, but prognoses are generally good.

thickened upward projection from posterior margin of mandibular ramus

condylar process of the mandible

short bone

cube-shaped bone that is approximately equal in length, width, and thickness; provides limited motion; being approximately equal in length, width, and thickness. The only short bones in the human skeleton are in the carpals of the wrists and the tarsals of the ankles. Short bones provide stability and support as well as some limited motion.

nasal conchae

curved bony plates that project from the lateral walls of the nasal cavity; include the superior and middle nasal conchae, which are parts of the ethmoid bone, and the independent inferior nasal conchae bone---These are bony plates that curve downward as they project into the space of the nasal cavity. They serve to swirl the incoming air, which helps to warm and moisturize it before the air moves into the delicate air sacs of the lungs. This also allows mucus, secreted by the tissue lining the nasal cavity, to trap incoming dust, pollen, bacteria, and viruses. The largest of the conchae is the inferior nasal concha, which is an independent bone of the skull. T

alveolar process of the maxilla

curved, inferior margin of the maxilla that supports and anchors the upper teeth-- forms upper jaw

long bone

cylinder-shaped bone that is longer than it is wide; functions as a lever

Define the parts and functions of the thoracic cage.

The thoracic cage is formed by the 12 pairs of ribs with their costal cartilages and the sternum. The ribs are attached posteriorly to the 12 thoracic vertebrae and most are anchored anteriorly either directly or indirectly to the sternum. The thoracic cage functions to protect the heart and lungs.

Discuss the development of the vertebrae, ribs, and sternum.

The vertebrae, ribs, and sternum all develop via the process of endochondral ossification. Mesenchyme tissue from the sclerotome portion of the somites accumulates on either side of the notochord and produces hyaline cartilage models for each vertebra. In the thorax region, a portion of this cartilage model splits off to form the ribs. Similarly, mesenchyme forms cartilage models for the right and left halves of the sternum. The ribs then become attached anteriorly to the developing sternum, and the two halves of sternum fuse together. Ossification of the cartilage model into bone occurs within these structures over time. This process continues until each is converted into bone, except for the sternal ends of the ribs, which remain as the costal cartilages.

greater wings of sphenoid bone

lateral projections of the sphenoid bone that form the anterior wall of the middle cranial fossa and an area of the lateral skull--- extend laterally to either side away from the sella turcica, where they form the anterior floor of the middle cranial fossa. Greater wing is best seen on the outside of the lateral skull, forms a rectangular area immediately anterior to the squamous portion of the temporal bone.

diploë

layer of spongy bone, that is sandwiched between two the layers of compact bone found in flat bones. The two layers of compact bone and the interior spongy bone work together to protect the internal organs. If the outer layer of a cranial bone fractures, the brain is still protected by the intact inner layer.

Which one of the following foods is best for bone health?

leafy green vegetables

lateral extensions of the sphenoid bone that form the bony lip separating the anterior and middle cranial fossae --- resemble wings of a flying bird, form the lip of the proinent ridge that marks the boundary between anterior and middle cranial fossae

lesser wings of the sphenoid bone

Long bones enable body movement by acting as a ________.

lever

anterior longitudinal ligament

ligament that runs the length of the vertebral column, uniting the anterior aspects of the vertebral bodies--Protection against this movement is particularly important in the neck, where extreme posterior bending of the head and neck can stretch or tear this ligament, resulting in a painful whiplash injury. Prior to the mandatory installation of seat headrests, whiplash injuries were common for passengers involved in a rear-end automobile

posterior longitudinal ligament

ligament that runs the length of the vertebral column, uniting the posterior sides of the vertebral bodies- anterior to spinal cord

series of short ligaments that unite the lamina of adjacent vertebrae-- yellow ligament--This consists of a series of short, paired ligaments, each of which interconnects the lamina regions of adjacent vertebrae. The ligamentum flavum has large numbers of elastic fibers, which have a yellowish color, allowing it to stretch and then pull back. Both of these ligaments provide important support for the vertebral column when bending forward.

ligamentum flavum

bone

living tissue/ foissil made inert by a process of mineralization, a child's bones will continue to grow and develop while contributing to the support and function of other body systems

external acoustic meatus

ear canal opening located on the lateral side of the skull --This is the large opening on the lateral side of the skull that is associated with the ear.

three small bones located in the middle ear cavity that serve to transmit sound vibrations to the inner ear

ear ossicles

sella turcica

elevated area of sphenoid bone located at midline of the middle cranial fossa

zygomatic arch

elongated, free-standing arch on the lateral skull, formed anteriorly by the temporal process of the zygomatic bone and posteriorly by the zygomatic process of the temporal bone--bony arch on the side of skull that spans from the area of the cheek to just above the ear canal.

Embryonic development of the axial skeleton involves ________.

endochondral ossification, which forms the ribs and sternum

The diaphysis contains ________.

fat stores

internal callus

fibrocartilaginous matrix, in the endosteal region, between the two ends of a broken bone--- 48 hours after the fracture, chondrocytes from the endosteum --

periosteum

fibrous membrane covering the outer surface of bone and continuous with ligaments (peri- = "around" or "surrounding"). periosteum contains blood vessels, nerves, and lymphatic vessels that nourish compact bone. Tendons and ligaments also attach to bones at the periosteum. The periosteum covers the entire outer surface except where the epiphyses meet other bones to form joints

atlas

first cervical (C1) vertebra -- vertebra supports skull on top of vertebral column

lumbar vertebrae

five vertebrae numbered as L1-L5 that are located in lumbar region (lower back) of the vertebral column- carries greatest amount of body weight and are thus characterized by the large size and thickness of the vertebral body (Figure). They have short transverse processes and a short, blunt spinous process that projects posteriorly. The articular processes are large, with the superior process facing backward and the inferior facing forward.

septal cartilage

flat cartilage structure that forms the anterior portion of the nasal septum-- flexible plate that fills in the gap between the perpendicular plate of the ethmoid and vomer bones. This cartilage also extends outward into the nose where it separates the right and left nostrils. The septal cartilage is not found in the dry skull.

nasal septum

flat, midline structure that divides the nasal cavity into halves, formed by the perpendicular plate of the ethmoid bone, vomer bone, and septal cartilage

sternum

flattened bone located at the center of the anterior chest

coronoid process of the mandible

flattened upward projection from the anterior margin of the mandibular ramus --- biting muscle flattended --

irregular opening in the base of the skull, located inferior to the exit of carotid canalThis opening is an artifact of the dry skull, because in life it is completely filled with cartilage. All the openings of the skull that provide for passage of nerves or blood vessels have smooth margins; the word lacerum ("ragged" or "torn") tells us that this opening has ragged edges and thus nothing passes through it.

foramen lacerum

The axial skeleton ________.

forms the vertical axis of the body

facial bones

fourteen bones that support the facial structures and form the upper and lower jaws and the hard palate--The facial bones underlie the facial structures, form the nasal cavity, enclose the eyeballs, and support the teeth of the upper and lower jaws. The rounded brain case surrounds and protects the brain and houses the middle and inner ear structures.

nucleus pulposus

gel-like central region of an intervertebral disc; provides for padding, weight-bearing, and movement between adjacent vertebrae---It has a high water content that serves to resist compression and thus is important for weight bearing. With increasing age, the water content of the nucleus pulposus gradually declines. This causes the disc to become thinner, decreasing total body height somewhat, and reduces the flexibility and range of motion of the disc, making bending more difficult.

bones

good fossils- soft tissue once living organism will decay and fall away over time, bone tissue will, undergo process of mineralization, turning bone to stone. well-preserved fossil skeleton gives us sense of size ans shape of organism just as our skeleton helps to define your size and shape.

bone

hard, dense connective tissue that forms the structural elements of the skeleton-- replacement tissue- mineral matrix

The middle cranial fossa ________.

has the foramen rotundum, foramen ovale, and foramen spinosum

The sternum ________.

has the sternal angle located between the manubrium and body

Anterior Cranial Fossa

he anterior cranial fossa is the most anterior and the shallowest of the three cranial fossae. It overlies the orbits and contains the frontal lobes of the brain. Anteriorly, the anterior fossa is bounded by the frontal bone, which also forms the majority of the floor for this space. The lesser wings of the sphenoid bone form the prominent ledge that marks the boundary between the anterior and middle cranial fossae. Located in the floor of the anterior cranial fossa at the midline is a portion of the ethmoid bone, consisting of the upward projecting crista galli and to either side of this, the cribriform plates

Which of the following occurs in the spongy bone of the epiphysis?

hematopoiesis

medullary cavity

hollow region of the diaphysis; filled with yellow marrow

costal cartilage

hyaline cartilage structure attached to the anterior end of each rib that provides for either direct or indirect attachment of most ribs to the sternum

The bony openings of the skull include the ________.

hypoglossal canal, which is located in the posterior cranial fossa

vertebra

individual bone in the neck and back regions of the vertebral column

bony process that extends downward from the vertebral arch of a vertebra that articulates with the superior articular process of the next lower vertebra0 faces or pojects downard on each side of vertebrae

inferior articular process

mental protuberance

inferior margin of anterior mandible that forms the chin-- forward projection from inferior margin of anterior mandible that forms chin

sacral hiatus

inferior opening and termination of the sacral canal

cranial cavity

interior space of the skull that houses the brain-- completly occupied by the brain

Bones that surround the spinal cord are classified as ________ bones.

irregular

median sacral crest

irregular ridge running down the midline of the posterior sacrum that was formed from the fusion of the spinous processes of the five sacral vertebrae--bumpy ridge that is the remnant of the fused spinous processes (median = "midline"; while medial = "toward, but not necessarily at, the midline")

superior orbital fissure

irregularly shaped opening between the middle cranial fossa and the posterior orbit-anterior wall of the middle cranial fossa, lateral to the optic canal and under the projecting margin of the lesser wing of the sphenoid bone. Nerves to the eyeball and associated muscles, and sensory nerves to the forehead pass through this opening.

jugular foramen

irregularly shaped opening located in the lateral floor of the posterior cranial cavity Several cranial nerves from the brain exit the skull via this opening. It is also the exit point through the base of the skull for all the venous return blood leaving the brain. The venous structures that carry blood inside the skull form large, curved grooves on the inner walls of the posterior cranial fossa, which terminate at each jugular foramen.

coronal suture

joint that unites the frontal bone to the right and left parietal bones across the top of the skull-- runs from side to side across skull, within coronal place of section

squamous suture

joint that unites the parietal bone to the squamous portion of the temporal bone on the lateral side of the skull --

sagittal suture

joint that unites the right and left parietal bones at the midline along the top of the skull --

The sternal angle is the ________.

junction between the manubrium and body

suture

junction line at which adjacent bones of the skull are united by fibrous connective tissue-- adjacent bones of the skull- narrow gap between bones filled with dense, fibrous connective tissue unites the bones.The long sutures located between the bones of the brain case are not straight, but instead follow irregular, tightly twisting paths. These twisting lines serve to tightly interlock the adjacent bones, thus adding strength to the skull for brain protection.

sternal angle

junction line between manubrium and body of the sternum and the site for attachment of the second rib to the sternum--because the junction between these two components is not flat, but forms a slight bend. The second rib attaches to the sternum at the sternal angle. Since the first rib is hidden behind the clavicle, the second rib is the highest rib that can be identified by palpation. Thus, the sternal angle and second rib are important landmarks for the identification and counting of the lower ribs. Ribs 3-7 attach to the sternal body.

inverted V-shaped joint that unites the occipital bone to the right and left parietal bones on the posterior skull

lambdoid suture

Which of the following are found in compact bone and cancellous bone?

lamellae

A typical vertebra has ________.

lamina that spans between the transverse process and spinous process

mandibular notch

large U-shaped notch located between the condylar process and coronoid process of the mandible

foramen magnum

large opening in the occipital bone of the skull through which the spinal cord emerges and the vertebral arteries enter the cranium

sacral foramina

series of paired openings for nerve exit located on both the anterior (ventral) and posterior (dorsal) aspects of the sacrum

cervical vertebrae

seven vertebrae numbered as C1-C7 that are located in the neck region of the vertebral column---such as C4 or C5, have several characteristic features that differentiate them from thoracic or lumbar vertebrae (Figure). Cervical vertebrae have a small body, reflecting the fact that they carry the least amount of body weight. Cervical vertebrae usually have a bifid (Y-shaped) spinous process. The spinous processes of the C3-C6 vertebrae are short, but the spine of C7 is much longer. You can find these vertebrae by running your finger down the midline of the posterior neck until you encounter the prominent C7 spine located at the base of the neck. The transverse processes of the cervical vertebrae are sharply curved (U-shaped) to allow for passage of the cervical spinal nerves.

body of the rib

shaft portion of a rib

lacrimal fossa

shallow depression in the anterior-medial wall of the orbit, formed by the lacrimal bone that gives rise to the nasolacrimal canal

hypophyseal (pituitary) fossa

shallow depression on top of the sella turcica that houses the pituitary (hypophyseal) gland

costal groove

shallow groove along the inferior margin of a rib that provides passage for blood vessels and a nerve

jugular (suprasternal) notch

shallow notch located on superior surface of sternal manubrium

temporal fossa

shallow space on the lateral side of the skull, above the level of the zygomatic arch--- braine case- shallow space

anterior cranial fossa

shallowest and most anterior cranial fossa of the cranial base that extends from the frontal bone to the lesser wing of the sphenoid bone

Most of the bones of the arms and hands are long bones; however, the bones in the wrist are categorized as ________.

short bones

temporal process of the zygomatic bone

short extension from the zygomatic bone that forms the anterior portion of the zygomatic arch---(the cheekbone) and a longer posterior portio

sacrum

single bone located near the inferior end of the adult vertebral column that is formed by the fusion of five sacral vertebrae; forms the posterior portion of the pelvis

costal facet

site on the lateral sides of a thoracic vertebra for articulation with the head of a rib

cranium

skull - skeletal structure of the head that supports the face and protects the brain

glabella

slight depression of frontal bone, located at the midline between the eyebrows---t its anterior midline, between the eyebrows

external occipital protuberance

small bump located at the midline on the posterior skull--which serves as an attachment site for a ligament of the posterior neck.

tubercle of the rib

small bump on the posterior side of a rib for articulation with the transverse process of a thoracic vertebra

lingula

small flap of bone located on the inner (medial) surface of mandibular ramus, next to the mandibular foramen ---This small flap of bone is named for its shape (lingula = "little tongue"). It is located immediately next to the mandibular foramen, on the medial side of the ramus. A ligament that anchors the mandible during opening and closing of the mouth extends down from the base of the skull and attaches to the lingula.

foramen spinosum

small opening in the floor of the middle cranial fossa, located lateral to the foramen ovale This small opening, located posterior-lateral to the foramen ovale, is the entry point for an important artery that supplies the covering layers surrounding the brain. The branching pattern of this artery forms readily visible grooves on the internal surface of the skull and these grooves can be traced back to their origin at the foramen spinosum.

nutrient foramen

small opening in the middle of the external surface of the diaphysis, through which an artery enters the bone to provide nourishment

xiphoid process

small process that forms the inferior tip of the sternum--This small structure is cartilaginous early in life, but gradually becomes ossified starting during middle age.

crista galli

small upward projection located at the midline in the floor of the anterior cranial fossa; formed by the ethmoid bone -- roosters comb or crest- small upward bony projection located at midline

hyoid bone

small, U-shaped bone located in upper neck that does not contact any other bone - head are an additional seven bones and ear ossicles-The hyoid serves as the base for the tongue above, and is attached to the larynx below and the pharynx posteriorly. The hyoid is held in position by a series of small muscles that attach to it either from above or below. These muscles act to move the hyoid up/down or forward/back. Movements of the hyoid are coordinated with movements of the tongue, larynx, and pharynx during swallowing and speaking.

facet

small, flattened area on a bone for an articulation (joint) with another bone, or for muscle attachment

cribriform plate

small, flattened areas with numerous small openings, located to either side of the midline in the floor of the anterior cranial fossa; formed by the ethmoid bone -- sieve- small nerve branches from olfactory areas of the nasal cavity passs through these openingsd to enter the brain

sesamoid bone

small, round bone embedded in a tendon; protects the tendon from compressive forces; being longer than it is wide. Keep in mind, however, that the term describes the shape of a bone, not its size. Long bones are found in the arms (humerus, ulna, radius) and legs (femur, tibia, fibula), as well as in the fingers (metacarpals, phalanges) and toes (metatarsals, phalanges). Long bones function as levers; they move when muscles contract.These bones form in tendons (the sheaths of tissue that connect bones to muscles) where a great deal of pressure is generated in a joint. The sesamoid bones protect tendons by helping them overcome compressive forces. Sesamoid bones vary in number and placement from person to person but are typically found in tendons associated with the feet, hands, and knees. The patellae (singular = patella) are the only sesamoid bones found in common with every person. Table reviews bone classifications with their associated features, functions, and examples.

superior nasal concha

smallest and most superiorly located of the nasal conchae; formed by the ethmoid bone- -- smaller and out of sign, above micheel concha. lateral to the perpendicular plate, in upper nasal cavity

articular tubercle

smooth ridge located on the inferior skull, immediately anterior to the mandibular fossa---The smooth ridge located immediately anterior to the mandibular fossa. Both the articular tubercle and mandibular fossa contribute to the temporomandibular joint, the joint that provides for movements between the temporal bone of the skull and the mandible.

infratemporal fossa

space on lateral side of skull, below the level of the zygomatic arch and deep (medial) to the ramus of the mandible--- below the level of the zygomatic arch and deep to the vertical portion of the mandible is another space

The first type of bone to form during fracture repair is ________ bone.

spongy

intervertebral disc

structure located between the bodies of adjacent vertebrae that strongly joins the vertebrae; provides padding, weight bearing ability, and enables vertebral column movements

skeleton

structure of living tissue that grows, repairs and renews itself

bony process that extends upward from the vertebral arch of a vertebra that articulates with the inferior articular process of the next higher vertebra -- extendes upward faces

superior articular process

supraorbital margin

superior margin of the orbit

flat bone

thin and curved bone; serves as a point of attachment for muscles and protects internal organs Examples include the cranial (skull) bones, the scapulae (shoulder blades), the sternum (breastbone), and the ribs. Flat bones serve as points of attachment for muscles and often protect internal organs.

articular cartilage

thin layer of cartilage covering an epiphysis; reduces friction and acts as a shock absorber.a thin layer of cartilage that reduces friction and acts as a shock absorber.These surfaces tend to conform to one another, such as one being rounded and the other cupped, to facilitate the function of the articulation

All of the following play a role in calcium homeostasis except

thyroxine

anulus fibrosus

tough, fibrous outer portion of an intervertebral disc, which is strongly anchored to the bodies of the adjacent vertebrae- outer layer of disc- ring/circle- adjacent vertebral bodies

Which of the following are only found in cancellous bone?

trabeculae

The internal and external calli are replaced by ________.

trabecular bone

diaphysis

tubular shaft that runs between the proximal and distal ends of a long bone

vitamin K

supports bone mineralization and synergistic role with vitamin D in regulation of bone growth. Green leafy vegetables are good source of vitamin K -minerals magnesium and fluoride may also play a role in supporting bone health. While magnesium is only found in trace amounts in the human body, more than 60 percent of it is in the skeleton, suggesting it plays a role in the structure of bone. Fluoride can displace the hydroxyl group in bone's hydroxyapatite crystals and form fluorapatite. Similar to its effect on dental enamel, fluorapatite helps stabilize and strengthen bone mineral. Fluoride can also enter spaces within hydroxyapatite crystals, thus increasing their density. Omega-3 fatty acids have long been known to reduce inflammation in various parts of the body. Inflammation can interfere with the function of osteoblasts, so consuming omega-3 fatty acids, in the diet or in supplements, may also help enhance production of new osseous tissue. Table summarizes the role of nutrients in bone health.

open reduction

surgical exposure of a bone to reset a fracture---While some fractures can be minor, others are quite severe and result in grave complications. For example, a fractured diaphysis of the femur has the potential to release fat globules into the bloodstream. These can become lodged in the capillary beds of the lungs, leading to respiratory distress and if not treated quickly, death.

posteriorly concave curvature of the lumbar vertebral column region; a secondary curve of the vertebral column---of the lower back develops. In adults, the lumbar curve is generally deeper in females.

lumbar curve

Without red marrow, bones would not be able to ________.

make blood cells

closed reduction

manual manipulation of a broken bone to set it into its natural position without surgery

horizontal plate

medial extension from the palatine bone that forms the posterior quarter of the hard palate-- largest region of each palatine bone . the plates from right and left palatine bones joint ogther at the midline to form posterior quarter of hard palate

sclerotome

medial portion of a somite consisting of mesenchyme tissue that will give rise to bone, cartilage, and fibrous connective tissues

perichondrium

membrane that covers cartilage--In a long bone, for example, at about 6 to 8 weeks after conception, some of the mesenchymal cells differentiate into chondrocytes (cartilage cells) that form the cartilaginous skeletal precursor of the bones

Bone modeling and remodeling

modeling and remodeling require osteoclasts to resorb unneeded, damaged, or old bone, and osteoblasts to lay down new bone. Two hormones that affect the osteoclasts are parathyroid hormone (PTH) and calcitonin. PTH stimulates osteoclast proliferation and activity. As a result, calcium is released from the bones into the circulation, thus increasing the calcium ion concentration in the blood. PTH also promotes the reabsorption of calcium by the kidney tubules, which can affect calcium homeostasis (see below). The small intestine is also affected by PTH, albeit indirectly. Because another function of PTH is to stimulate the synthesis of vitamin D, and because vitamin D promotes intestinal absorption of calcium, PTH indirectly increases calcium uptake by the small intestine. Calcitonin, a hormone secreted by the thyroid gland, has some effects that counteract those of PTH. Calcitonin inhibits osteoclast activity and stimulates calcium uptake by the bones, thus reducing the concentration of calcium ions in the blood. As evidenced by their opposing functions in maintaining calcium homeostasis, PTH and calcitonin are generally not secreted at the same time. Table summarizes the hormones that influence the skeletal system.-- maintaining a blood calcium level of about 10 mg/dL, is critical for normal body functions. Hypocalcemia can result in problems with blood coagulation, muscle contraction, nerve functioning, and bone strength. Hypercalcemia can result in lethargy, sluggish reflexes, constipation and loss of appetite, confusion, and coma. Calcium homeostasis is controlled by PTH, vitamin D, and calcitonin and the interactions of the skeletal, endocrine, digestive, and urinary systems.

neck of the rib

narrowed region of a rib, next to the rib head

middle nasal concha

nasal concha formed by the ethmoid bone that is located between the superior and inferior conchae- independent bone of the skull- inferior concha-- part of ethmoid bone

When calcium levels are too high or too low, which body system is primarily affected?

nervous system

rod-like structure along dorsal side of the early embryo; largely disappears during later development but does contribute to formation of the intervertebral discs

notochord

Which is found only in the cervical region of the vertebral column?

nuchal ligament

expanded portion of the supraspinous ligament within the posterior neck; interconnects the spinous processes of the cervical vertebrae and attaches to the base of the skull

nuchal ligament

The lambdoid suture joins the parietal bone to the ________.

occipital bone

ethmoid air cell

one of several small, air-filled spaces located within the lateral sides of the ethmoid bone, between the orbit and upper nasal cavity

inferior nasal concha

one of the paired bones that project from the lateral walls of the nasal cavity to form the largest and most inferior of the nasal conchae-- independent bone of the skull

somite

one of the paired, repeating blocks of tissue located on either side of the notochord in the early embryo

anterior (ventral) sacral foramen

one of the series of paired openings located on the anterior (ventral) side of the sacrum

metabolic level

one tissue performs several critical functions

A fracture can be both ________.

open and transverse

vertebral foramen

opening associated with each vertebra defined by the vertebral arch that provides passage for the spinal cord

transverse foramen

opening found only in the transverse processes of cervical vertebrae--An important artery that supplies the brain ascends up the neck by passing through these openings. The superior and inferior articular processes of the cervical vertebrae are flattened and largely face upward or downward, respectively.

internal acoustic meatus

opening into petrous ridge, located on the lateral wall of the posterior cranial fossa---This opening is located inside the cranial cavity, on the medial side of the petrous ridge. It connects to the middle and inner ear cavities of the temporal bone

intervertebral foramen

opening located between adjacent vertebrae for exit of a spinal nerve

supraorbital foramen

opening located on anterior skull, at the superior margin of the passage of a sensory nerve to the skin of the forehead

infraorbital foramen

opening located on anterior skull, below the orbit-- below the orbit-which is the point of emergence for a sensory nerve that supplies the anterior face below the orbit.

stylomastoid foramen

opening located on inferior skull, between the styloid process and mastoid process ---This small opening is located between the styloid process and mastoid process. This is the point of exit for the cranial nerve that supplies the facial muscles.

mental foramen

opening located on the anterior-lateral side of the mandibular body- opening located on each side of the anterior-lateral mandible, exit site for a sensory nerve supplies chin

mandibular foramen

opening located on the inner (medial) surface of the mandibular ramus - opening leads into tunnel that runs down leganth of mandibular body. The sensory nerve and blood vessels supply lower teeth enter mandibular foramen and then follow this tunnel. Numb lower teeth prior to dental work, dentist must inject anesthesia into lateral wall of oral cavity at a point prior to where this sensory nerve enters mandibular foramen

hole

opening or depression in a bone.is an opening or groove in the bone that allows blood vessels and nerves to enter the bone. As with the other markings, their size and shape reflect the size of the vessels and nerves that penetrate the bone at these points.

Which of the following bones is (are) formed by intramembranous ossification?

the flat bones of the cranium

temporal bone

paired bones that form the lateral, inferior portions of the skull, with squamous, mastoid, and petrous portions--lower lateral side of the skull (see Figure). Common wisdom has it that the temporal bone (temporal = "time") is so named because this area of the head (the temple) is where hair typically first turns gray, indicating the passage of time.

palatine bone

paired bones that form the posterior quarter of the hard palate and a small area in floor of the orbit- irregularly shapes bones that contribute small areas to the lateral walls of nasal cavity and medial wall of each orbit

parietal bone

paired bones that form the upper, lateral sides of the skull--These are paired bones, with the right and left parietal bones joining together at the top of the skull. Each parietal bone is also bounded anteriorly by the frontal bone, inferiorly by the temporal bone, and posteriorly by the occipital bone.

superior nuchal line

paired bony lines on the posterior skull that extend laterally from the external occipital protuberance - lateral to either side of this bump -- nuchal- nape/ posterior neck

transverse process

paired bony processes that extends laterally from the vertebral arch of a vertebra-- projects laterally and arises from junction point between pedicle and lamina

lateral sacral crest

paired irregular ridges running down the lateral sides of the posterior sacrum that was formed by the fusion of the transverse processes from the five sacral vertebrae

clavicular notch

paired notches located on the superior-lateral sides of the sternal manubrium, for articulation with the clavicle--- is the shallow depression located on either side at the superior-lateral margins of the manubrium. This is the site of the sternoclavicular joint, between the sternum and clavicle. The first ribs also attach to the manubrium.

medial pterygoid (wing shaped) plate

paired, flattened bony projections of the sphenoid bone located on the inferior skull medial to the lateral pterygoid plate; form the posterior portion of the nasal cavity lateral wall

lateral pterygoid plate

paired, flattened bony projections of the sphenoid bone located on the inferior skull, lateral to the medial pterygoid plate

occipital condyle

paired, oval-shaped bony knobs located on the inferior skull, to either side of the foramen magnum-- joints with first cervical vertebra and support skull on top of vertebral column

The fibrous membrane covering the outer surface of the bone is the ________.

periosteum

petrous ridge

petrous portion of the temporal bone that forms a large, triangular ridge in the floor of the cranial cavity, separating the middle and posterior cranial fossae; houses the middle and inner ear structures ---

angle of the rib

portion of rib with greatest curvature; together, the rib angles form the most posterior extent of the thoracic cage

brain case (cranial vault)

portion of the skull that contains and protects the brain, consisting of the eight bones that form the cranial base and rounded upper skull

lamina

portion of the vertebral arch on each vertebra that extends between the transverse and spinous process

one of the series of paired openings located on the posterior (dorsal) side of the sacrum

posterior (dorsal) sacral foramen/ anterior (ventral) sacral foramen

head of the rib

posterior end of a rib that articulates with the bodies of thoracic vertebrae

cervical curve

posteriorly concave curvature of the cervical vertebral column region; a secondary curve of the vertebral column--neck region develops as the infant begins to hold their head upright when sitting.

secondary curve

posteriorly concave curvatures of the cervical and lumbar regions of the vertebral column that develop after the time of birth-child learns to sit upright, stand, and walk. Secondary curves are concave posteriorly, opposite in direction to the original fetal curvature

osteocyte

primary cell in mature bone; responsible for maintaining the matrix. As the secreted matrix surrounding the osteoblast calcifies, the osteoblast become trapped within it; as a result, it changes in structure

anteriorly concave curvatures of the thoracic and sacrococcygeal regions that are retained from the original fetal curvature of the vertebral column

primary curve

intramembranous ossification

process by which bone forms directly from mesenchymal tissue-compact and spongy bone develops directly from sheets of mesenchymal (undifferentiated) connective tissue. The flat bones of the face, most of the cranial bones, and the clavicles (collarbones) are formed via intramembranous ossification.

endochondral ossification

process in which bone forms by replacing hyaline cartilage---Cartilage does not become bone. Instead, cartilage serves as a template to be completely replaced by new bone. Endochondral ossification takes much longer than intramembranous ossification. Bones at the base of the skull and long bones form via endochondral ossification.

region of the epiphyseal plate that makes new chondrocytes to replace those that die at the diaphyseal end of the plate and contributes to longitudinal growth of the epiphyseal plate

proliferative zone

Which function of the skeletal system would be especially important if you were in a car accident?

protection of internal organs

primary ossification center

region, deep in the periosteal collar, where bone development starts during endochondral ossification--second or third month of fetal life, bone cell development and ossification ramps up and creates

process by which osteoclasts resorb old or damaged bone at the same time as and on the same surface where osteoblasts form new bone to replace that which is resorbed--in which resorption of old or damaged bone takes place on the same surface where osteoblasts lay new bone to replace that which is resorbed. Injury, exercise, and other activities lead to remodeling.

remodeling

thin, curved bones of the chest wall

ribs

foramen rotundum

round opening in the floor of the middle cranial fossa, located between the superior orbital fissure and foramen ovale- It is the exit point for a major sensory nerve that supplies the cheek, nose, and upper teeth.

angle of the mandible

rounded corner located at outside margin of the body and ramus junction -- comes togheer

bony tunnel that runs through the sacrum

sacral canal

abnormal lateral curvature of the vertebral column- severe enough to slip under shoulder blande (scapula) forcing it up as a hump.

scoliosis

axis

second cervical (C2) vertebra-because it serves as the axis for rotation when turning the head toward the right or left.

Parts of the sphenoid bone include the ________.

sella turcica

cartilage

semi-rigid form of connective tissue, provides flexibility and smooth surfaces for movement

thoracic vertebrae

twelve vertebrae numbered as T1-T12 that are located in the thoracic region (upper back) of the vertebral column --The characteristic feature for a typical midthoracic vertebra is the spinous process, which is long and has a pronounced downward angle that causes it to overlap the next inferior vertebra. The superior articular processes of thoracic vertebrae face anteriorly and the inferior processes face posteriorly. These orientations are important determinants for the type and range of movements available to the thoracic region of the vertebral column.

osteoid

uncalcified bone matrix secreted by osteoblasts

osteogenic cell

undifferentiated cell with high mitotic activity; the only bone cells that divide; they differentiate and develop into osteoblasts-- immature osteogenic cells are found in deep layers of periosteum and the mattow.

frontal bone

unpaired bone that forms forehead, roof of orbit, and floor of anterior cranial fossa

sphenoid bone

unpaired bone that forms the central base of skull-- single, complex bone of the central skull- keystone bone joins with almost every other bone of the skull -- exxtends laterally to contribtute to the sides of the skull

vomer bone

unpaired bone that forms the inferior and posterior portions of the nasal septum -lower portion

mandible

unpaired bone that forms the lower jaw bone; the only moveable bone of the skull-- skull consists of 22 indivudal bones, 21 of which are immobile and united into a single unit.-- mandible consists of paird right and left bones, fuse togerher during first year to form the single u-shaped mandible of adult skull

occipital bone

unpaired bone that forms the posterior portions of the brain case and base of the skull

ethmoid bone

unpaired bone that forms the roof and upper, lateral walls of the nasal cavity, portions of the floor of the anterior cranial fossa and medial wall of orbit, and the upper portion of the nasal septum -- single midline bone taht forms the roof and lateral walls of the upper nasal cavity, upper portion of nasal septume, contributes to the medial wall of the orbit .

spinous process

unpaired bony process that extends posteriorly from the vertebral arch of a vertebra - spine- midline of the back - series of bumps under skin down the middle back

alveolar process of the mandible

upper border of mandibular body that contains the lower teeth

bony passageway within the vertebral column for the spinal cord that is formed by the series of individual vertebral foramina

vertebral (spinal) canal

Which of the following is part of the axial skeleton?

vertebral column

floating ribs

vertebral ribs 11-12 that do not attach to the sternum or to the costal cartilage of another rib

false ribs

vertebrochondral ribs 8-12 whose costal cartilage either attaches indirectly to the sternum via the costal cartilage of the next higher rib or does not attach to the sternum at all

true ribs

vertebrosternal ribs 1-7 that attach via their costal cartilage directly to the sternum

ramus of the mandible

vertical portion of the mandible -- each side mandible consists of horizontal body and posteriorly -- branch

Calcium cannot be absorbed from the small intestine if ________ is lacking.

vitamin D

articulation

where two bone surfaces meet

Describe the vertebral column and define each region.

Answer: The adult vertebral column consists of 24 vertebrae, plus the sacrum and coccyx. The vertebrae are subdivided into cervical, thoracic, and lumbar regions. There are seven cervical vertebrae (C1-C7), 12 thoracic vertebrae (T1-T12), and five lumbar vertebrae (L1-L5). The sacrum is derived from the fusion of five sacral vertebrae and the coccyx is formed by the fusion of four small coccygeal vertebrae.

Long

Cylinder-like shape, longer than it is wide Leverage Femur, tibia, fibula, metatarsals, humerus, ulna, radius, metacarpals, phalanges

pterion

H-shaped suture junction region that unites the frontal, parietal, temporal, and sphenoid bones on the lateral side of the skull- weakest part of the skull-- two finger widths aboce zygomatic arch, thumbs width posterior to the upward portion of zygomatic bone

If you were a dietician who had a young female patient with a family history of osteoporosis, what foods would you suggest she include in her diet? Why?

Since maximum bone mass is achieved by age 30, I would want this patient to have adequate calcium and vitamin D in her diet. To do this, I would recommend ingesting milk and other dairy foods, green leafy vegetables, and intact canned sardines so she receives sufficient calcium. Intact salmon would be a good source for calcium and vitamin D. Other fatty fish would also be a good vitamin D source.

What are the structural and functional differences between a tarsal and a metatarsal?

Structurally, a tarsal is a short bone, meaning its length, width, and thickness are about equal, while a metatarsal is a long bone whose length is greater than its width. Functionally, the tarsal provides limited motion, while the metatarsal acts as a lever.

What are the structural and functional differences between the femur and the patella?

Structurally, the femur is a long bone, meaning its length is greater than its width, while the patella, a sesamoid bone, is small and round. Functionally, the femur acts as a lever, while the patella protects the patellar tendon from compressive forces.

Define the two divisions of the skeleton.

The axial skeleton forms the vertical axis of the body and includes the bones of the head, neck, back, and chest of the body. It consists of 80 bones that include the skull, vertebral column, and thoracic cage. The appendicular skeleton consists of 126 bones and includes all bones of the upper and lower limbs.

Discuss the functions of the axial skeleton.

The axial skeleton supports the head, neck, back, and chest of the body and allows for movements of these body regions. It also gives bony protections for the brain, spinal cord, heart, and lungs; stores fat and minerals; and houses the blood-cell producing tissue.

Flat

Thin and curved Points of attachment for muscles; protectors of internal organs Sternum, ribs, scapulae, cranial bones

Watch this video to view a rotating and exploded skull with color-coded bones. Which bone (yellow) is centrally located and joins with most of the other bones of the skull?

The sphenoid bone joins with most other bones of the skull. It is centrally located, where it forms portions of the rounded brain case and cranial base.

Describe the parts of the sternum.

The sternum consists of the manubrium, body, and xiphoid process. The manubrium forms the expanded, superior end of the sternum. It has a jugular (suprasternal) notch, a pair of clavicular notches for articulation with the clavicles, and receives the costal cartilage of the first rib. The manubrium is joined to the body of the sternum at the sternal angle, which is also the site for attachment of the second rib costal cartilages. The body receives the costal cartilage attachments for ribs 3-7. The small xiphoid process forms the inferior tip of the sternum.

Yellow marrow has been identified as ________.

an area of fat storage

Why is cartilage slow to heal?

because it does not have a blood supply

The skeletal system is made of ________.

bones and cartilage

orbit

bony socket that contains the eyeball and associated muscles that moves the eyeball or open the upper eyelid

skull

bony structure that forms the head, face, and jaws, and protects the brain; consists of 22 bones

If a bone breaks into many small parts, what kind of fracture is this?

comminuted

mastoid process

large bony prominence on the inferior, lateral skull, just behind the earlobe -- projecting inferiorly from this region is a large prominence-- serves as a muscle attachment side -- easily to be felt on the side of the head just berhind your earlobe

Which of the following is a function of the axial skeleton?

supports trunk of body

ligament that interconnects the spinous processes of the thoracic and lumbar vertebrae--where it interconnects the spinous processes of the thoracic and lumbar vertebrae. This strong ligament supports the vertebral column during forward bending motions.

supraspinous ligament

Sesamoid bones are found embedded in ________.

tendons

carotid canal

zig-zag tunnel providing passage through the base of the skull for the internal carotid artery to the brain; begins anteromedial to the styloid process and terminates in the middle cranial cavity, near the posterior-lateral base of the sella turcica-- Its entrance is located on the outside base of the skull, anteromedial to the styloid process. The canal then runs anteromedially within the bony base of the skull, and then turns upward to its exit in the floor of the middle cranial cavity, above the foramen lacerum.

cheekbone; paired bones that contribute to the lateral orbit and anterior zygomatic arch-- Each of the paired zygomatic bones forms much of the lateral wall of the orbit and the lateral-inferior margins of the anterior orbital opening (see Figure). The short temporal process of the zygomatic bone projects posteriorly, where it forms the anterior portion of the zygomatic arch

zygomatic bone

extension from the temporal bone that forms the posterior portion of the zygomatic arch---Thus the temporal process (anteriorly) and the zygomatic process (posteriorly) join together, like the two ends of a drawbridge, to form the zygomatic arch. One of the major muscles that pulls the mandible upward during biting and chewing arises from the zygomatic arch.

zygomatic process of the temporal bone

kyphosis

(also, humpback or hunchback) excessive posterior curvature of the thoracic vertebral column region--- spinal curvature excessive dorsoventrally -- preteens result of poor posture, abnormal growth, indeterminate causes. people also age, accumulate spinal column injuries and diseases like osteoporosis lead to curvatures of spine, stooping you see in elderly. Sports Medicine- simple injuries such as sprained ankle, complex injuries torn rotator cuff in shoulder. exercise to surgery as well.

maxillary bone

(also, maxilla) paired bones that form the upper jaw and anterior portion of the hard palate- together form upper jaw, hard palate, medial floor of the orbit, lateal base of the nose

ossification

(also, osteogenesis) bone formation--arly stages of embryonic development, the embryo's skeleton consists of fibrous membranes and hyaline cartilage. By the sixth or seventh week of embryonic life, the actual process of bone development,

calvaria

(also, skullcap) rounded top of the skull-- cavity is bounded superiorly by the rounded top of the skull, lateral and posterior sides of the skull. the bones that form the top and sides of the brain case are usally referred to as the "flat" bones of the skull

lordosis

(also, swayback) excessive anterior curvature of the lumbar vertebral column region

trabeculae

(singular = trabecula) spikes or sections of the lattice-like matrix in spongy bone- random network, each trabecula forms along lines of stress to provide strength to the bone. dense and heavy compact bone by making bones lighter so the muscles can move early

optic canal

opening spanning between middle cranial fossa and posterior orbit-which allows for passage of the optic nerve from the retina to the brain. Lateral to this is the elongated and irregularly shaped superior orbital fissure, which provides passage for the artery that supplies the eyeball, sensory nerves, and the nerves that supply the muscles involved in eye movementsThis opening is located at the anterior lateral corner of the sella turcica. It provides for passage of the optic nerve into the orbit.

nasal cavity

opening through skull for passage of air- inside the nasal area of the skull divided by nasal septum

skeletal system

organ system composed of bones and cartilage that provides for movement, support, and protection - supports the body, facilitates movement, protects internal organs, produces blood cells, stores and releases minerals and fats

Which of the following are incapable of undergoing mitosis?

osteoblasts and osteocytes

osteoid

osteoblasts secrete- uncalcified` matrix, which calcifies (hardens) within a few days as mineral salts are deposited on it, thereby entrapping the osteoblasts within----unmineralized bone matrix) secreted around the capillaries results in a trabecular matrix, while osteoblasts on the surface of the spongy bone become the periosteum (Figurec). The periosteum then creates a protective layer of compact bone superficial to the trabecular bone. The trabecular bone crowds nearby blood vessels, which eventually condense into red marrow

Which cells do not originate from osteogenic cells?

osteoprogenitor cells

mandibular fossa

oval depression located on the inferior surface of the skullThis is the deep, oval-shaped depression located on the external base of the skull, just in front of the external acoustic meatus. The mandible (lower jaw) joins with the skull at this site as part of the temporomandibular joint, which allows for movements of the mandible during opening and closing of the mouth

foramen ovale of the middle cranial fossa

oval-shaped opening in the floor of the middle cranial fossa This large, oval-shaped opening in the floor of the middle cranial fossa provides passage for a major sensory nerve to the lateral head, cheek, chin, and lower teeth.

condyle

oval-shaped process located at the top of the condylar process of the mandible

lacrimal bone

paired bones that contribute to the anterior-medial wall of each orbit--- small, rectangular bone that forms the anterior, medial wall of the orbit

nasal bone

paired bones that form the base of the nose-- is one of two small bones that articulate (join) with each other to form the bony base (bridge) of the nose. They also support the cartilages that form the lateral walls of the nose (see Figure). These are the bones that are damaged when the nose is broken.

hypoglossal canal

paired openings that pass anteriorly from the anterior-lateral margins of the foramen magnum deep to the occipital condylesThese emerge on the inferior aspect of the skull at the base of the occipital condyle and provide passage for an important nerve to the tongue.

superior articular process of the sacrum

paired processes that extend upward from the sacrum to articulate (join) with the inferior articular processes from the L5 vertebra

medial projection from the maxilla bone that forms the anterior three quarters of the hard palate-- inferior skull- point each maxillary bone can be seen joining together at the midline to form the aterior three-quarters of the hard palate

palatine process

Which of the following is a bone of the brain case?

parietal bone

nasolacrimal canal

passage for drainage of tears that extends downward from the medial-anterior orbit to the nasal cavity, terminating behind the inferior nasal conchae --The lacrimal fluid (tears of the eye), which serves to maintain the moist surface of the eye, drains at the medial corner of the eye into the nasolacrimal canal. This duct then extends downward to open into the nasal cavity, behind the inferior nasal concha. In the nasal cavity, the lacrimal fluid normally drains posteriorly, but with an increased flow of tears due to crying or eye irritation, some fluid will also drain anteriorly, thus causing a runny nose.

portion of the vertebral arch that extends from the vertebral body to the transverse process

pedicle

posterior arch

posterior portion of the ring-like C1 (atlas) vertebra

modeling

process, during bone growth, by which bone is resorbed on one surface of a bone and deposited on another---bones are increasing in length, they are also increasing in diameter; growth in diameter can continue even after longitudinal growth ceases. This is called appositional growth. Osteoclasts resorb old bone that lines the medullary cavity, while osteoblasts, via intramembranous ossification, produce new bone tissue beneath the periosteum. The erosion of old bone along the medullary cavity and the deposition of new bone beneath the periosteum not only increase the diameter of the diaphysis but also increase the diameter of the medullary cavity.

Which of the following is not a function of bones?

produce nerve cells

endocrine system

produces and secretes hormones, many of which interact with the skeletal system. These hormones are involved in controlling bone growth, maintaining bone once it is formed, and remodeling it.

hematopoiesis

production of blood cells, which occurs in the red marrow of the bones

secondary ossification center

region of bone development in the epiphyses--While these deep changes are occurring, chondrocytes and cartilage continue to grow at the ends of the bone (the future epiphyses), which increases the bone's length at the same time bone is replacing cartilage in the diaphyses. By the time the fetal skeleton is fully formed, cartilage only remains at the joint surface as articular cartilage and between the diaphysis and epiphysis as the epiphyseal plate, the latter of which is responsible for the longitudinal growth of bones. After birth, this same sequence of events (matrix mineralization, death of chondrocytes, invasion of blood vessels from the periosteum, and seeding with osteogenic cells that become osteoblasts) occurs in the epiphyseal regions, and each of these centers of activity is referred

zone of calcified matrix

region of the epiphyseal plate closest to the diaphyseal end; functions to connect the epiphyseal plate to the diaphysis---the zone closest to the diaphysis, are dead because the matrix around them has calcified. Capillaries and osteoblasts from the diaphysis penetrate this zone, and the osteoblasts secrete bone tissue on the remaining calcified cartilage. Thus, the zone of calcified matrix connects the epiphyseal plate to the diaphysis. A bone grows in length when osseous tissue is added to the diaphysis.

reserve zone

region of the epiphyseal plate that anchors the plate to the osseous tissue of the epiphysis and contains small chondrocytes within the matrix. These chondrocytes do not participate in bone growth but secure the epiphyseal plate to the osseous tissue of the epiphysis.

zone of maturation and hypertrophy

region of the epiphyseal plate where chondrocytes from the proliferative zone grow and mature and contribute to the longitudinal growth of the epiphyseal plate

The cervical region of the vertebral column consists of ________.

seven vertebrae

coccyx

small bone located at inferior end of the adult vertebral column that is formed by the fusion of four coccygeal vertebrae; also referred to as the "tailbone"

How many bones are in the adult's skull?

22

View this animation to see how a blow to the head may produce a contrecoup (counterblow) fracture of the basilar portion of the occipital bone on the base of the skull. Why may a basilar fracture be life threatening?

A basilar fracture may damage an artery entering the skull, causing bleeding in the brain.

Describe a typical vertebra.

A typical vertebra consists of an anterior body and a posterior vertebral arch. The body serves for weight bearing. The vertebral arch surrounds and protects the spinal cord. The vertebral arch is formed by the pedicles, which are attached to the posterior side of the vertebral body, and the lamina, which come together to form the top of the arch. A pair of transverse processes extends laterally from the vertebral arch, at the junction between each pedicle and lamina. The spinous process extends posteriorly from the top of the arch. A pair of superior articular processes project upward and a pair of inferior articular processes project downward. Together, the notches found in the margins of the pedicles of adjacent vertebrae form an intervertebral foramen.

Considering how a long bone develops, what are the similarities and differences between a primary and a secondary ossification center?

A single primary ossification center is present, during endochondral ossification, deep in the periosteal collar. Like the primary ossification center, secondary ossification centers are present during endochondral ossification, but they form later, and there are two of them, one in each epiphysis.

Discuss the parts of a typical rib.

A typical rib is a flattened, curved bone. The head of a rib is attached posteriorly to the costal facets of the thoracic vertebrae. The rib tubercle articulates with the transverse process of a thoracic vertebra. The angle is the area of greatest rib curvature and forms the largest portion of the thoracic cage. The body (shaft) of a rib extends anteriorly and terminates at the attachment to its costal cartilage. The shallow costal groove runs along the inferior margin of a rib and carries blood vessels and a nerve.

fontanelle

expanded area of fibrous connective tissue that separates the brain case bones of the skull prior to birth and during the first year after birth--As the brain case bones grow in the fetal skull, they remain separated from each other by large areas of dense connective tissue,---The fontanelles are the soft spots on an infant's head. They are important during birth because these areas allow the skull to change shape as it squeezes through the birth canal. After birth, the fontanelles allow for continued growth and expansion of the skull as the brain enlarges. The largest fontanelle is located on the anterior head, at the junction of the frontal and parietal bones. The fontanelles decrease in size and disappear by age 2. However, the skull bones remained separated from each other at the sutures, which contain dense fibrous connective tissue that unites the adjacent bones. The connective tissue of the sutures allows for continued growth of the skull bones as the brain enlarges during childhood growth.

manubrium

expanded, superior portion of the sternum

lacunae

(singular = lacuna) spaces in a bone that house an osteocyte-- surrounded by bone tissue

Irregular

Complex shape Protect internal organs Vertebrae, facial bones

spongy bone

(also, cancellous bone) trabeculated osseous tissue that supports shifts in weight distribution- contains osteocytes housed in lacunae, not arranged in concentric circle

epiphyseal plate

(also, growth plate) sheet of hyaline cartilage in the metaphysis of an immature bone; replaced by bone tissue as the organ grows in length --growth plate), a layer of hyaline (transparent) cartilage in a growing bone. When the bone stops growing in early adulthood (approximately 18-21 years), the cartilage is replaced by osseous tissue and the epiphyseal plate becomes an epiphyseal line.

perforating canal

(also, Volkmann's canal) channel that branches off from the central canal and houses vessels and nerves that extend to the periosteum and endosteum

osteon

(also, Haversian system) basic structural unit of compact bone; made of concentric layers of calcified matrix

During the early years of space exploration our astronauts, who had been floating in space, would return to earth showing significant bone loss dependent on how long they were in space. Discuss how this might happen and what could be done to alleviate this condition.

Astronauts floating in space were not exerting significant pressure on their bones; they were "weightless." Without the force of gravity exerting pressure on the bones, bone mass was lost. To alleviate this condition, astronauts now do resistive exercise designed to apply forces to the bones and thus help keep them healthy.--astronauts can lose approximately 1 to 2 percent of their bone mass per month. This loss of bone mass is thought to be caused by the lack of mechanical stress on astronauts' bones due to the low gravitational forces in space. Lack of mechanical stress causes bones to lose mineral salts and collagen fibers, and thus strength. Similarly, mechanical stress stimulates the deposition of mineral salts and collagen fibers. The internal and external structure of a bone will change as stress increases or decreases so that the bone is an ideal size and weight for the amount of activity it endures. That is why people who exercise regularly have thicker bones than people who are more sedentary. It is also why a broken bone in a cast atrophies while its contralateral mate maintains its concentration of mineral salts and collagen fibers. The bones undergo remodeling as a result of forces (or lack of forces) placed on them.

chiropractor

Chiropractors are health professionals who use nonsurgical techniques to help patients with musculoskeletal system problems that involve the bones, muscles, ligaments, tendons, or nervous system. They treat problems such as neck pain, back pain, joint pain, or headaches. Chiropractors focus on the patient's overall health and can also provide counseling related to lifestyle issues, such as diet, exercise, or sleep problems. If needed, they will refer the patient to other medical specialists. Chiropractors use a drug-free, hands-on approach for patient diagnosis and treatment. They will perform a physical exam, assess the patient's posture and spine, and may perform additional diagnostic tests, including taking X-ray images. They primarily use manual techniques, such as spinal manipulation, to adjust the patient's spine or other joints. They can recommend therapeutic or rehabilitative exercises, and some also include acupuncture, massage therapy, or ultrasound as part of the treatment program. In addition to those in general practice, some chiropractors specialize in sport injuries, neurology, orthopaedics, pediatrics, nutrition, internal disorders, or diagnostic imaging. To become a chiropractor, students must have 3-4 years of undergraduate education, attend an accredited, four-year Doctor of Chiropractic (D.C.) degree program, and pass a licensure examination to be licensed for practice in their state. With the aging of the baby-boom generation, employment for chiropractors is expected to increase.

Cleft Lip and Cleft Palate

During embryonic development, the right and left maxilla bones come together at the midline to form the upper jaw. At the same time, the muscle and skin overlying these bones join together to form the upper lip. Inside the mouth, the palatine processes of the maxilla bones, along with the horizontal plates of the right and left palatine bones, join together to form the hard palate. If an error occurs in these developmental processes, a birth defect of cleft lip or cleft palate may result. Cleft lip is a common development defect that affects approximately 1:1000 births, most of which are male. This defect involves a partial or complete failure of the right and left portions of the upper lip to fuse together, leaving a cleft (gap). A more severe developmental defect is cleft palate, which affects the hard palate. The hard palate is the bony structure that separates the nasal cavity from the oral cavity. It is formed during embryonic development by the midline fusion of the horizontal plates from the right and left palatine bones and the palatine processes of the maxilla bones. Cleft palate affects approximately 1:2500 births and is more common in females. It results from a failure of the two halves of the hard palate to completely come together and fuse at the midline, thus leaving a gap between them. This gap allows for communication between the nasal and oral cavities. In severe cases, the bony gap continues into the anterior upper jaw where the alveolar processes of the maxilla bones also do not properly join together above the front teeth. If this occurs, a cleft lip will also be seen. Because of the communication between the oral and nasal cavities, a cleft palate makes it very difficult for an infant to generate the suckling needed for nursing, thus leaving the infant at risk for malnutrition. Surgical repair is required to correct cleft palate defects.

What is the difference between closed reduction and open reduction? In what type of fracture would closed reduction most likely occur? In what type of fracture would open reduction most likely occur?

In closed reduction, the broken ends of a fractured bone can be reset without surgery. Open reduction requires surgery to return the broken ends of the bone to their correct anatomical position. A partial fracture would likely require closed reduction. A compound fracture would require open reduction.

In what ways do intramembranous and endochondral ossification differ?

In intramembranous ossification, bone develops directly from sheets of mesenchymal connective tissue, but in endochondral ossification, bone develops by replacing hyaline cartilage. Intramembranous ossification is complete by the end of the adolescent growth spurt, while endochondral ossification lasts into young adulthood. The flat bones of the face, most of the cranial bones, and a good deal of the clavicles (collarbones) are formed via intramembranous ossification, while bones at the base of the skull and the long bones form via endochondral ossification.

The skeletal system is composed of bone and cartilage and has many functions. Choose three of these functions and discuss what features of the skeletal system allow it to accomplish these functions.

It supports the body. The rigid, yet flexible skeleton acts as a framework to support the other organs of the body. It facilitates movement. The movable joints allow the skeleton to change shape and positions; that is, move. It protects internal organs. Parts of the skeleton enclose or partly enclose various organs of the body including our brain, ears, heart, and lungs. Any trauma to these organs has to be mediated through the skeletal system. It produces blood cells. The central cavity of long bones is filled with marrow. The red marrow is responsible for forming red and white blood cells. It stores and releases minerals and fat. The mineral component of bone, in addition to providing hardness to bone, provides a mineral reservoir that can be tapped as needed. Additionally, the yellow marrow, which is found in the central cavity of long bones along with red marrow, serves as a storage site for fat.

paget's disease

Paget's disease usually occurs in adults over age 40. It is a disorder of the bone remodeling process that begins with overactive osteoclasts. This means more bone is resorbed than is laid down. The osteoblasts try to compensate but the new bone they lay down is weak and brittle and therefore prone to fracture. While some people with Paget's disease have no symptoms, others experience pain, bone fractures, and bone deformities (Figure). Bones of the pelvis, skull, spine, and legs are the most commonly affected. When occurring in the skull, Paget's disease can cause headaches and hearing loss unknown, but hereditary factors seem to play a role. Some scientists believe Paget's disease is due to an as-yet-unidentified virus. Paget's disease is diagnosed via imaging studies and lab tests. X-rays may show bone deformities or areas of bone resorption. Bone scans are also useful. In these studies, a dye containing a radioactive ion is injected into the body. Areas of bone resorption have an affinity for the ion, so they will light up on the scan if the ions are absorbed. In addition, blood levels of an enzyme called alkaline phosphatase are typically elevated in people with Paget's disease.

Head and traumatic brain injuries are major causes of immediate death and disability, with bleeding and infections as possible additional complications. According to the Centers for Disease Control and Prevention (2010), approximately 30 percent of all injury-related deaths in the United States are caused by head injuries. The majority of head injuries involve falls. They are most common among young children (ages 0-4 years), adolescents (15-19 years), and the elderly (over 65 years). Additional causes vary, but prominent among these are automobile and motorcycle accidents.

Strong blows to the brain-case portion of the skull can produce fractures. These may result in bleeding inside the skull with subsequent injury to the brain. The most common is a linear skull fracture, in which fracture lines radiate from the point of impact. Other fracture types include a comminuted fracture, in which the bone is broken into several pieces at the point of impact, or a depressed fracture, in which the fractured bone is pushed inward. In a contrecoup (counterblow) fracture, the bone at the point of impact is not broken, but instead a fracture occurs on the opposite side of the skull. Fractures of the occipital bone at the base of the skull can occur in this manner, producing a basilar fracture that can damage the artery that passes through the carotid canal. A blow to the lateral side of the head may fracture the bones of the pterion. The pterion is an important clinical landmark because located immediately deep to it on the inside of the skull is a major branch of an artery that supplies the skull and covering layers of the brain. A strong blow to this region can fracture the bones around the pterion. If the underlying artery is damaged, bleeding can cause the formation of a hematoma (collection of blood) between the brain and interior of the skull. As blood accumulates, it will put pressure on the brain. Symptoms associated with a hematoma may not be apparent immediately following the injury, but if untreated, blood accumulation will exert increasing pressure on the brain and can result in death within a few hours.

In what ways is the structural makeup of compact and spongy bone well suited to their respective functions?

The densely packed concentric rings of matrix in compact bone are ideal for resisting compressive forces, which is the function of compact bone. The open spaces of the trabeculated network of spongy bone allow spongy bone to support shifts in weight distribution, which is the function of spongy bone.

Discuss the process that gives rise to the base and facial bones of the skull.

The facial bones and base of the skull arise via the process of endochondral ossification. This process begins with the localized accumulation of mesenchyme tissue at the sites of the future bones. The mesenchyme differentiates into hyaline cartilage, which forms a cartilage model of the future bone. The cartilage allows for growth and enlargement of the model. It is gradually converted into bone over time.

Middle Cranial Fossa

The middle cranial fossa is deeper and situated posterior to the anterior fossa. It extends from the lesser wings of the sphenoid bone anteriorly, to the petrous ridges (petrous portion of the temporal bones) posteriorly. The large, diagonally positioned petrous ridges give the middle cranial fossa a butterfly shape, making it narrow at the midline and broad laterally. The temporal lobes of the brain occupy this fossa. The middle cranial fossa is divided at the midline by the upward bony prominence of the sella turcica, a part of the sphenoid bone. The middle cranial fossa has several openings for the passage of blood vessels and cranial nerve

Craniosynostosis

The premature closure (fusion) of a suture line is a condition called craniosynostosis. This error in the normal developmental process results in abnormal growth of the skull and deformity of the head. It is produced either by defects in the ossification process of the skull bones or failure of the brain to properly enlarge. Genetic factors are involved, but the underlying cause is unknown. It is a relatively common condition, occurring in approximately 1:2000 births, with males being more commonly affected. Primary craniosynostosis involves the early fusion of one cranial suture, whereas complex craniosynostosis results from the premature fusion of several sutures. The early fusion of a suture in primary craniosynostosis prevents any additional enlargement of the cranial bones and skull along this line. Continued growth of the brain and skull is therefore diverted to other areas of the head, causing an abnormal enlargement of these regions. For example, the early disappearance of the anterior fontanelle and premature closure of the sagittal suture prevents growth across the top of the head. This is compensated by upward growth by the bones of the lateral skull, resulting in a long, narrow, wedge-shaped head. This condition, known as scaphocephaly, accounts for approximately 50 percent of craniosynostosis abnormalities. Although the skull is misshapen, the brain still has adequate room to grow and thus there is no accompanying abnormal neurological development. In cases of complex craniosynostosis, several sutures close prematurely. The amount and degree of skull deformity is determined by the location and extent of the sutures involved. This results in more severe constraints on skull growth, which can alter or impede proper brain growth and development. Cases of craniosynostosis are usually treated with surgery. A team of physicians will open the skull along the fused suture, which will then allow the skull bones to resume their growth in this area. In some cases, parts of the skull will be removed and replaced with an artificial plate. The earlier after birth that surgery is performed, the better the outcome. After treatment, most children continue to grow and develop normally and do not exhibit any neurological problems.

Describe the sacrum.

The sacrum is a single, triangular-shaped bone formed by the fusion of five sacral vertebrae. On the posterior sacrum, the median sacral crest is derived from the fused spinous processes, and the lateral sacral crest results from the fused transverse processes. The sacral canal contains the sacral spinal nerves, which exit via the anterior (ventral) and posterior (dorsal) sacral foramina. The sacral promontory is the anterior lip. The sacrum also forms the posterior portion of the pelvis.

regions of vertebral column

The vertebral column originally develops as a series of 33 vertebrae, but this number is eventually reduced to 24 vertebrae, plus the sacrum and coccyx. The vertebral column is subdivided into five regions, with the vertebrae in each area named for that region and numbered in descending order. In the neck, there are seven cervical vertebrae, each designated with the letter "C" followed by its number. Superiorly, the C1 vertebra articulates (forms a joint) with the occipital condyles of the skull. Inferiorly, C1 articulates with the C2 vertebra, and so on. Below these are the 12 thoracic vertebrae, designated T1-T12. The lower back contains the L1-L5 lumbar vertebrae. The single sacrum, which is also part of the pelvis, is formed by the fusion of five sacral vertebrae. Similarly, the coccyx, or tailbone, results from the fusion of four small coccygeal vertebrae. However, the sacral and coccygeal fusions do not start until age 20 and are not completed until middle age. An interesting anatomical fact is that almost all mammals have seven cervical vertebrae, regardless of body size. This means that there are large variations in the size of cervical vertebrae, ranging from the very small cervical vertebrae of a shrew to the greatly elongated vertebrae in the neck of a giraffe. In a full-grown giraffe, each cervical vertebra is 11 inches tall.

How can a fractured diaphysis release fat globules into the bloodstream?

The yellow marrow in the diaphysis is exposed and damaged.

Describe the parts of the nasal septum in both the dry and living skull.

There are two bony parts of the nasal septum in the dry skull. The perpendicular plate of the ethmoid bone forms the superior part of the septum. The vomer bone forms the inferior and posterior parts of the septum. In the living skull, the septal cartilage completes the septum by filling in the anterior area between the bony components and extending outward into the nose.

In endochondral ossification, what happens to the chondrocytes?

They die in the calcified matrix that surrounds them and form the medullary cavity.

yellow marrow

connective tissue in the interior cavity of a bone where fat is stored - contains adipose tissue; the triglycerides stored in the adipocytes of the tissue can serve as a source of energ

red marrow

connective tissue in the interior cavity of a bone where hematopoiesis takes place- the production of blood cells—takes place. Red blood cells, white blood cells, and platelets are all produced in the red marrow.

thoracic cage

consists of 12 pairs of ribs and sternum (flattened bone)

vertebral column

entire sequence of bones that extend from the skull to the tailbone

Bones grow in length due to activity in the ________.

epiphyseal plate

Which of the following hormones are responsible for the adolescent growth spurt?

estrogen and testosterone

osteogenesis imperfecta

is a genetic disease in which bones do not form properly and therefore are fragile and break easily. It is also called brittle bone disease. The disease is present from birth and affects a person throughout life. The genetic mutation that causes OI affects the body's production of collagen, one of the critical components of bone matrix. The severity of the disease can range from mild to severe. Those with the most severe forms of the disease sustain many more fractures than those with a mild form. Frequent and multiple fractures typically lead to bone deformities and short stature. Bowing of the long bones and curvature of the spine are also common in people afflicted with OI. Curvature of the spine makes breathing difficult because the lungs are compressed. Because collagen is such an important structural protein in many parts of the body, people with OI may also experience fragile skin, weak muscles, loose joints, easy bruising, frequent nosebleeds, brittle teeth, blue sclera, and hearing loss. There is no known cure for OI. Treatment focuses on helping the person retain as much independence as possible while minimizing fractures and maximizing mobility. Toward that end, safe exercises, like swimming, in which the body is less likely to experience collisions or compressive forces, are recommended. Braces to support legs, ankles, knees, and wrists are used as needed. Canes, walkers, or wheelchairs can also help compensate for weaknesses. When bones do break, casts, splints, or wraps are used. In some cases, metal rods may be surgically implanted into the long bones of the arms and legs. Research is currently being conducted on using bisphosphonates to treat OI. Smoking and being overweight are especially risky in people with OI, since smoking is known to weaken bones, and extra body weight puts additional stress on the bones.

The tubercle of a rib ________.

is for articulation with the transverse process of a thoracic vertebra

A fontanelle ________.

is the area of fibrous connective tissue found at birth between the brain case bones

Which category of bone is among the most numerous in the skeleton?

long bone

central canal

longitudinal channel in the center of each osteon; contains blood vessels, nerves, and lymphatic vessels; also known as the Haversian canal

pituitary gland secretes growth hormone (GH),

which, as its name implies, controls bone growth in several ways. It triggers chondrocyte proliferation in epiphyseal plates, resulting in the increasing length of long bones. GH also increases calcium retention, which enhances mineralization, and stimulates osteoblastic activity, which improves bone density. GH is not alone in stimulating bone growth and maintaining osseous tissue. Thyroxine, a hormone secreted by the thyroid gland promotes osteoblastic activity and the synthesis of bone matrix. During puberty, the sex hormones (estrogen in girls, testosterone in boys) also come into play. They too promote osteoblastic activity and production of bone matrix, and in addition, are responsible for the growth spurt that often occurs during adolescence. They also promote the conversion of the epiphyseal plate to the epiphyseal line (i.e., cartilage to its bony remnant), thus bringing an end to the longitudinal growth of bones. Additionally, calcitriol, the active form of vitamin D, is produced by the kidneys and stimulates the absorption of calcium and phosphate from the digestive tract.

epiphysis

wide section at each end of a long bone; filled with spongy bone and red marrow