Biology A&P Chapter 6

There are three general classes of bone markings

(1) articulations: -where two bone surfaces come together. -These surfaces tend to conform to one another, such as one being rounded and the other cupped, to facilitate the function of the articulation. (2) projections: - an area of a bone that projects above the surface of the bone. - attachment points for tendons and ligaments. - their size and shape is an indication of the forces exerted through the attachment to the bone. (3) holes: - an opening or groove in the bone that allows blood vessels and nerves to enter the bone. - their size and shape reflect the size of the vessels and nerves that penetrate the bone at these points.

Describe a fracture

a broken bone. It will heal whether or not a physician resets it in its anatomical position.

What are Calcium ions essential for?

muscle contractions and controlling the flow of other ions involved in the transmission of nerve impulses

Irregular bones tend to have what?

more complex shapes, like the vertebrae that support the spinal cord and protect it from compressive forces.

How do, early osteoblasts appear?

In a cluster called an ossification center, Although they will ultimately be spread out by the formation of bone tissue

Describe the rate of bone growth

- Bones continue to grow in length until early adulthood. - The rate of growth is controlled by hormones - When the chondrocytes in the epiphyseal plate stop their proliferation and bone replaces the cartilage, longitudinal growth stops. - All that remains of the epiphyseal plate is the epiphyseal line

How are the endocrine system the skeletal system interconnected?

- Endocrine system hormones are involved in controlling bone growth, maintaining bone once it is formed, and remodeling it.

What are some sources of calcium?

- Milk and other dairy foods - green leafy vegetables - broccoli - intact salmon - canned sardines with their soft bones. provide calcium in smaller quantities: - Nuts - beans -seeds - shellfish

What is produced in the red marrow.

- Red blood cells - white blood cells - platelets

What is the osteoblast Each osteocyte is located in a space called a lacuna and is surrounded by bone tissue. Osteocytes maintain the mineral concentration of the matrix via the secretion of enzymes. Like osteoblasts, osteocytes lack mitotic activity. They can communicate with each other and receive nutrients via long cytoplasmic processes that extend through canaliculi (singular = canaliculus), channels within the bone matrix.

- The bone cell responsible for forming new bone - Found in the growing portions of bone, including the periosteum and endosteum. - Do not divide, synthesize and secrete the collagen matrix and calcium salts.

Describe what modeling is and the process behind it.

- The matrix is resorbed on one surface of a bone and deposited on another - Modeling primarily takes place during a bone's growth.

Describe chondrocytes in the next layer, the zone of maturation and hypertrophy

- They are older and larger than those in the proliferative zone. - The more mature cells are situated closer to the diaphysial end of the plate.

Describe hypercalcemia

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

Describe Hypocalcemia

- a condition characterized by abnormally low levels of calcium - can have an adverse effect on a number of different body systems including circulation, muscles, nerves, and bone. - causes can range from hormonal imbalances to an improper diet.

Describe the importance of calcium in the body

- a critical component of bone, especially in the form of calcium phosphate and calcium carbonate. -Since the body cannot make calcium, it must be obtained from the diet.

What is 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.

Where are Long bones found?

- arms (humerus, ulna, radius) - legs (femur, tibia, fibula) - fingers (metacarpals, phalanges) - toes (metatarsals, phalanges)

What happens 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 - bones may become brittle.

What are the short bones in the human skeleton?

- carpals of the wrists - tarsals of the ankles.

Calcium ions are needed for what?

- for bone mineralization - for tooth health - regulation of the heart rate and strength of contraction - blood coagulation - contraction of smooth and skeletal muscle cells - regulation of nerve impulse conduction.

How is the small intestine affected by PTH?

- 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.

After birth, what same sequence of events occurs? Where does this sequence occur? What is it referred to as

- matrix mineralization - death of chondrocytes - invasion of blood vessels from the periosteum - seeding with osteogenic cells that become osteoblasts occurs in the epiphyseal regions secondary ossification cents

After a bone fracture, what occurs over the next several weeks?

- osteoclasts resorb the dead bone - osteogenic cells become active, divide, and differentiate into osteoblasts. - The cartilage in the call is replaced by trabecular bone via endochondral ossification

What do the nerves do?

- sense pain - play roles in regulating blood supplies - play a role in bone growth, hence their concentrations in metabolically active sites of the bone.

What happens as more matrix is produced?

- the chondrocytes in the center of the cartilaginous model grow in size. - As the matrix calcifies, nutrients can no longer reach the chondrocytes. - This results in their death and the disintegration of the surrounding cartilage. -Blood vessels invade the resulting spaces, not only enlarging the cavities but also carrying osteogenic cells with them, many of which will become osteoblasts. - These enlarging spaces eventually combine to become the medullary cavity.

What are Examples of flat bones

- the cranial (skull) bones - the scapulae (shoulder blades) - the sternum (breastbone) - the ribs

Describe the layout of spongy bone?

- the lacunae and osteocytes are found in a lattice-like network of matrix spikes called trabecular - The trabecular may appear to be a random network, but each trabecular forms along lines of stress to provide strength to the bone. - The spaces of the trabeculated network provide balance to the dense and heavy compact bone by making bones lighter so that muscles can move them more easily.

What is the proliferative zone

- the next layer toward the diaphysis - contains stacks of slightly larger chondrocytes. - It makes new chondrocytes (via mitosis) to replace those that die at the diaphysial end of the plate.

On a metabolic level, bone tissue performs what critical functions?

-the bone matrix acts as a reservoir for a number of minerals important to the functioning of the body especially calcium, and phosphorus.

What are examples of bones protecting internal organs?

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

What does PTH do?

1.) 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. 2.) Promotes the reabsorption of calcium by the kidney tubules, which can affect calcium homeostasis

Which hormones are necessary for controlling bone growth and maintaining the bone matrix. Explain how.

1.) The pituitary gland secretes growth hormone (GH) 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.

How are the cells of the parathyroid gland involved with calcium?

1.) They have plasma membrane receptors for calcium. 2.) When calcium is not binding to these receptors, the cells release PTH, which stimulates osteoclast proliferation and resorption of bone by osteoclasts. 3.) This demineralization process releases calcium into the blood. 4.) PTH promotes reabsorption of calcium from the urine by the kidneys, so that the calcium returns to the blood. 5.)Finally, PTH stimulates the synthesis of vitamin D, which in turn, stimulates calcium absorption from any digested food in the small intestine. 6.) When all these processes return blood calcium levels to normal, there is enough calcium to bind with the receptors on the surface of the cells of the parathyroid glands, and this cycle of events is turned off

Describe what occurs when a bone breaks.

1.) blood flows from any vessel torn by the fracture. - These vessels could be in the periosteum, osteons, and/or medullary cavity. 2.) The blood begins to clot, and about six to eight hours after the fracture, the clotting blood has formed a fracture hematoma 3.) The disruption of blood flow to the bone results in the death of bone cells around the fracture.

The minerals ______ and _________ may also play a role in supporting bone health.

1.) magnesium: - 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. 2.)fluoride: - can displace the hydroxyl group in bone's hydroxyapatite crystals and form fluorapatite.(helps stabilize and strengthen bone mineral.) - Fluoride can also enter spaces within hydroxyapatite crystals, thus increasing their density.

What happens when blood levels of calcium get too high?

1.) the thyroid gland is stimulated to release calcitonin 2.) which inhibits osteoclast activity and stimulates calcium uptake by the bones, but also decreases reabsorption of calcium by the kidneys. 3.) All of these actions lower blood levels of calcium. 4.) When blood calcium levels return to normal, the thyroid gland stops secreting calcitonin.

How many bones compose the adult skeleton? How are they divided?

206 into five categories based on their shapes

Describe the following bone fracture Open (or compound)

A fracture in which at least one end of the broken bone tears through the skin; carries a high risk of infection

Describe the following bone fracture Closed (or simple)

A fracture in which the skin remains intact

Describe the following bone fracture Greenstick

A partial fracture in which only one side of the bone is broken

After complete healing What may remain?

A slight swelling may remain on the outer surface of the bone, but quite often, that region undergoes remodeling, and no external evidence of the fracture remains.

Describe the following bone fracture Spiral

Bone segments are pulled apart as a result of a twisting motion

What happens after the chondrocytes death?

Blood vessels invade the resulting spaces, enlarging the cavities and also carrying osteogenic cells with them (many of which will become osteoblasts.)

The osteocytes in spongy bone are nourished by what? How?

Blood vessels of the periosteum that penetrate spongy bone and blood that circulates in the marrow cavities. As the blood passes through the marrow cavities, it is collected by veins, which then pass out of the bone through the foramina.

How does bone tissue (osseous tissue) differ greatly from other tissues in the body

Bone is hard and many of its functions depend on that characteristic hardness.

How do bones protect internal organs from injury

By covering or surrounding them.

How does bone develop in endochondral ossification?.

By replacing hyaline cartilage. Cartilage does not become bone. Instead, cartilage serves as a template to be completely replaced by new bone

How do bones facilitate movement in the human body?

By serving as points of attachment for your muscles. - Some bones only serve as a support for the muscles - others also transmit the forces produced when your muscles contract.

______ is not only the most abundant mineral in bone, it is also the most abundant mineral in the human body.

Calcium

_______ is a chemical element that cannot be produced by any biological processes. The only way it can enter the body is through the _____.

Calcium diet

Within about 48 hours after the fracture what is happening?

Chondrocytes from the endosteum have created an internal callus which stabilizes the fracture. HOW: by secreting a fibrocartilaginous matrix between the two ends of the broken bone, while the periosteal chondrocytes and osteoblasts create an external callus of hyaline cartilage and bone, respectively, around the outside of the break.

When is it evident that healing of a fracture is complete.

Eventually, the internal and external calli unite, compact bone replaces spongy bone at the outer margins of the fracture

When does Intramembranous ossification begin?

In utero during fetal development and continues on into adolescence.

Omega-3 fatty acids have long been known to reduce what? what do they help produce

Inflammation in various parts of the body. may also help enhance production of new osseous tissue.

What leads to remodeling?

Injury, exercise, and other activities but even without injury or exercise, about 5 to 10 percent of the skeleton is remodeled annually just by destroying old bone and renewing it with fresh bone

What occurs with lack of mechanical stress?

It causes bones to lose mineral salts and collagen fibers, and thus strength. It 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.

Describe the epiphyseal plate The epiphyseal plate is composed of four zones of cells and activity (Figure 6.18). The reserve zone is the region closest to the epiphyseal end of the plate 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.

It is a layer of hyaline cartilage where ossification occurs in immature bones.

Vitamin ____ also supports bone mineralization and may have a synergistic role with vitamin D in the regulation of bone growth. What is a good source for this vitamin?

K Green leafy vegetables

compare and contrast compact bone and spongy bone

Like compact bone, spongy bone (also known as cancellous bone) contains osteocytes housed in lacunae, but they are not arranged in concentric circles.

What do longs bones function as?

Long bones function as levers; they move when muscles contract.

What explains why people who exercise regularly have thicker bones than people who are more sedentary? Or why a broken bone in a cast atrophies while its contralateral mate maintains its concentration of mineral salts and collagen fibers.

Mechanical stress

Describe the following bone fracture Oblique

Occurs at an angle that is not 90 degrees

Describe the following bone fracture Transverse

Occurs straight across the long axis of the bone

Describe the following bone fracture Impacted

One fragment is driven into the other, usually as a result of compression

________ are continually breaking down old bone while _________ are continually forming new bone.

Osteoclasts osteoblasts

________ fills the spaces in the spongy bone.

Red marrow

Describe the following bone fracture Comminuted

Several breaks result in many small pieces between two large segments

What does the dynamic nature of bone mean?

That new tissue is constantly formed, and old, injured, or unnecessary bone is dissolved for repair or for calcium release.

Typically, vitamin D is not found naturally in many foods (Except for fatty fish like salmon and tuna, or fortified milk or cereal).......So how is it produced?

The action of sunlight on the skin triggers the body to produce its own vitamin D. In cases of deficiency, a doctor can prescribe a vitamin D supplement.

If osteoblasts and osteocytes are incapable of mitosis, then how are they replenished when old ones die?

The answer lies in the properties of a third category of bone cells—the osteogenic cell. These are undifferentiated with high mitotic activity and they are the only bone cells that divide. Immature osteogenic cells are found in the deep layers of the periosteum and the marrow. They differentiate and develop into osteoblasts.

How do Bones act as a storage site for calcium? what is it regulated by?

The body deposits calcium in the bones when blood levels get too high, and it releases calcium when blood levels drop too low. This process is regulated by PTH, vitamin D, and calcitonin.

what are the 2 parts of a long bone

The diaphysis: is the tubular shaft that runs between the proximal and distal ends of the bone. epiphysis:

How is the skeletal system interdependent with other organs systems?

The food you take in via your digestive system and the hormones secreted by your endocrine system affect your bones. Even using your muscles to engage in exercise has an impact on your bones.

What is the medullary cavity

The hollow region in the diaphysis which is filled with yellow marrow.

what is the only sesamoid bone found in common with every person.

The patellae (singular = patella)

Describe whats contained in/around the periosteum

The periosteum contains blood vessels, nerves, and lymphatic vessels that nourish compact bone. Tendons and ligaments also attach to bones at the periosteum.

Besides calcium, what other vitamin is important for bones? Why?

Therefore, intake of vitamin D is also critical to bone health. - calcium cannot be absorbed from the small intestine without vitamin D. - it also plays a role, in bone remodeling.

What are PTH and calcitonin generally not secreted at the same time?

They have opposing functions in maintaining calcium homeostasis

As the matrix calcifies, nutrients can no longer reach the chondrocytes. What does this results in?

This results in their death and the disintegration of the surrounding cartilage.

True or False? bone is the same regardless of the pathway that produces it.

True

True or False? Some fractures may be described using more than one term because it may have the features of more than one type

True

A bone is not going to move, unless what happens?

Unless a muscle spans a joint and contracts

What is a closed reduction.

When a broken bone is manipulated and set into its natural position without surgery

when do the salt crystals in bone form

When calcium phosphate and calcium carbonate combine to create hydroxyapatite, which incorporates other inorganic salts like magnesium hydroxide, fluoride, and sulfate as it crystallizes, or calcifies, on the collagen fibers.

What are the two types of bone marrow?

Yellow marrow: -contains adipose tissue; the triglycerides stored in the adipocytes of the tissue can serve as a source of energy. Red marrow: - where hematopoiesis—the production of blood cells—takes place.

The outer surface of the bone is covered with what?

a fibrous membrane called the periosteum

Describe the framework for bone thats laid down during fetal development

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.

Describe what Bone, or osseous tissue is

a hard, dense connective tissue that forms most of the adult skeleton, the support structure of the body.

What is Thyroxine?

a hormone secreted by the thyroid gland promotes osteoblastic activity and the synthesis of bone matrix.

Flat bones, like those of the cranium, consist of what

a layer of diploë (spongy bone), lined on either side by a layer of compact bone

Without the skeletal system, you would be....

a limp mass of organs, muscle, and skin.

What does bone contain

a relatively small number of cells entrenched in a matrix of collagen fibers that provide a surface for inorganic salt crystals to adhere.

What type of tissue is bone?

a replacement tissue: it uses a model tissue on which to lay down its mineral matrix.

What is Cartilage

a semi-rigid form of connective tissue

Osteoid (unmineralized bone matrix) secreted around the capillaries results in What? while osteoblasts on the surface of the spongy bone become the ________.

a trabecular matrix periosteum

What is the normal level of calcium in the blood what happens if it varies from this

about 10 mg/dL. When the body cannot maintain this level, a person will experience hypo- or hypercalcemia.

The microscopic structural unit of compact bone is called...

an osteon, or Haversian system

What provides flexibility and smooth surfaces for movement in the areas of the skeleton where bones move (for example, the ribcage and joints)

cartilage

where do The spongy bone and medullary cavity receive nourishment from

arteries that pass through the compact bone. The arteries enter through the nutrient foramen (small openings in the diaphysis)

In the periosteum region, the epiphyses are covered with In this region, the epiphyses are covered with what?

articular cartilage, a thin layer of cartilage that reduces friction and acts as a shock absorber.

chondrocytes and cartilage continue to grow where? which increases what?

at the ends of the bone (the future epiphyses) the bone's length at the same time bone is replacing cartilage in the diaphyses.

By the time a fetus is born, most of the cartilage has been replaced with _________. Some additional cartilage will be replaced throughout childhood, and some __________ remains in the adult skeleton.

bone cartilage

The softer connective tissue that fills the interior of most bone is referred to as what?

bone marrow

During long space missions, astronauts can lose approximately 1 to 2 percent of their________ per month. Why?

bone mass 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.

Capillaries and osteoblasts from the diaphysis penetrate this zone, and the osteoblasts secrete what?

bone tissue on the remaining calcified cartilage

The skeletal system is the body system composed of what?

bones and cartilage

What type of effect does inflammation have on the body?

can interfere with the function of osteoblasts,

As the cartilage grows, ________ penetrate it. What does this penetration initiate?

capillaries the transformation of the perichondrium into the bone-producing periosteum.

On the epiphyseal side of the epiphyseal plate, what is formed. On the diaphysial side, cartilage is ________, and the diaphysis .....

cartilage - ossified - grows in length

How is cartilage different from 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.

For skeletal development, the most common template is _____.

cartilage.

The longitudinal growth of bone is a result of what

cellular division in the proliferative zone the maturation of cells in the zone of maturation and hypertrophy.

Running down the center of each osteon is the _____________ which contains what?

central canal, or Haversian canal blood vessels, nerves, and lymphatic vessels. -These vessels and nerves branch off at right angles through a perforating canal, also known as Volkmann's canals, to extend to the periosteum and endosteum.

Most bones contain what 2 types of osseous tissue?

compact and spongy but their distribution and concentration vary based on the bone's overall function.

The periosteum creates a protective layer of what?

compact bone superficial to the trabecular bone.

Each osteon is composed of what?

concentric rings of calcified matrix called lamellae (singular = lamella).

calcium homeostasis is _______. Which body systems work together to maintain a normal calcium level in the blood

critical The skeletal, endocrine, and digestive systems play a role in this, but the kidneys do, too. These body systems work together to maintain a normal calcium level in the blood

A short bone is one that is....

cube-like in shape, being approximately equal in length, width, and thickness.

A long bone is one that is....

cylindrical in shape, being longer than it is wide.

Most of the chondrocytes in the zone of calcified matrix, the zone closest to the diaphysis, are...

dead because the matrix around them has calcified.

The walls of the diaphysis are composed of what

dense and hard compact bone.

While bones are increasing in length, they are also increasing in _________.

diameter

An irregular bone is one that...

does not have any easily characterized shape and therefore does not fit any other classification.

How are bone shapes and functions related?

each categorical shape of bone has a distinct function.

Bones at the base of the skull and long bones form via endochondral ossification

endochondral ossification

The medullary cavity has a delicate membranous lining called the _________. What occurs here?

endosteum bone growth, repair, and remodeling occur.

The ________ is the area of growth in a long bone.

epiphyseal plate

The wider section at each end of the bone is called the what

epiphysis (plural = epiphyses), which is filled with spongy bone.

How long can growth in diameter continue?

even after longitudinal growth ceases. This is called appositional growth.

Bone also serves as a site for.....

fat storage and blood cell production.

In the early stages of embryonic development, what does the embryo consist of?

fibrous membranes and hyaline cartilage

The bones undergo remodeling as a result of ______ (or lack of forces) placed on them.

forces

The most apparent functions of the skeletal system are the...

gross functions—those visible by observation.

Where do sesamoid bones form?

in tendons (the sheaths of tissue that connect bones to muscles) where a great deal of pressure is generated in a joint.

In addition to the blood vessels, nerves follow the same paths into the bone where they tend to concentrate where?

in the more metabolically active regions of the bone.

Where are the osteocytes located?

inside spaces called lacunae (singular = lacuna) found at the borders of adjacent lamellae.

All of the organ systems of your body are ___________

interdependent

Endochondral ossification takes much longer than ____________. Bones at the base of the skull and long bones form via endochondral ossification

intramembranous ossification

What are the two osteogenic pathways?

intramembranous ossification and endochondral ossification

The flat bones of the face, most of the cranial bones, and the clavicles (collarbones) are formed via ____________________.

intramembranous ossification.

Many facial bones, particularly the ones containing sinuses, are classified as what

irregular bones

What does the erosion of old bone along the medullary cavity and the deposition of new bone beneath the periosteum do?

not only increase the diameter of the diaphysis but also increase the diameter of the medullary cavity. This process is called modeling.

Throughout fetal development and into childhood growth and development, where does bone form?

on the cartilaginous matrix.

By the time the fetal skeleton is fully formed, where does cartilage remains

only at the joint surface as articular cartilage and between the diaphysis and epiphysis as the epiphyseal plate

What are the four types of cells found within bone tissue?

osteoblasts, osteocytes, osteogenic cells, and osteoclasts

The cell responsible for bone resorption, or breakdown, is the ______, Describe these.

osteoclast - They are found on bone surfaces - are multinucleate - originate from monocytes and macrophages two types of white blood cells - not from osteogenic cells.

Bone modeling and remodeling require what?

osteoclasts to resorb unneeded, damaged, or old bone, and osteoblasts to lay down new bone.

Once entrapped, the osteoblasts become ________. What do osteogenic cells in the surrounding connective tissue do as osteoblasts transform into osteocytes, differentiate into new osteoblasts?

osteocytes osteogenic cells in the surrounding connective tissue

What do the osteoblasts secrete?

osteoid, uncalcified matrix, which calcifies within a few days as mineral salts are deposited on it, trapping the osteoblasts within.

What are the two hormones that affect the osteoclasts

parathyroid hormone (PTH) and calcitonin.

What do flat bones serve as

points of attachment for muscles and often protect internal organs.

The two layers of compact bone and the interior spongy bone work together to do what?

protect the internal organs. ex: If the outer layer of a cranial bone fractures, the brain is still protected by the intact inner layer.

While some fractures can be minor, others are.... give an example

quite severe and result in grave complications. EX: 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.

Describe bone cell development and ossification by the second or third month of fetal life

ramps up and creates the primary ossification center, a region deep in the periosteal collar where ossification begins

The trabecular bone crowds nearby blood vessels, which eventually condense into __________

red marrow

the spaces in some spongy bones contain what?.

red marrow, protected by the trabeculae, where hematopoiesis occurs

Osteoclasts resorb old bone that lines what?

the medullary cavity

Describe bone remodeling in adult life.

resorption of old or damaged bone takes place on the same surface where osteoblasts lay new bone to replace that which is resorbed.

During intramembranous ossification, compact and spongy bone develops directly from.....

sheets of mesenchymal (undifferentiated) connective tissue.

the chondrocytes in the center of the cartilaginous model eventually increase in ________

size

A sesamoid bone is a....

small, round bone that, as the name suggests, is shaped like a sesame seed.

What happens in a long bone 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 Soon after, the perichondrium, a membrane that covers the cartilage appears

What do short bones provide for the body?

stability and support as well as some limited motion.

Compact bone is..... spongy (cancellous) bone.....

stringer more and more dense so that it can withstand compressive forces has open spaces and supports shifts in weight distribution

What does open reduction require

surgery to expose the fracture and reset the bone.

what do the sesamoid bones protect

tendons by helping them overcome compressive forces.

What is calcitriol?

the active form of vitamin D - is produced by the kidneys - stimulates the absorption of calcium and phosphate from the digestive tract.

What happens in the sixth or seventh week of embryonic life?

the actual process of bone development, ossification (osteogenesis), begins.

Describe how the bones support the human body.

the bones and cartilage of your skeletal system compose the scaffold that supports the rest of your body.

What will these enlarging spaces created by chondrocyte death eventually combine to become?

the medullary cavity.

What do canaliculi connect with? what does this allow for?

the canaliculi of other lacunae and eventually with the central canal. This system allows nutrients to be transported to the osteocytes and wastes to be removed from them.

What happens 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.

The ongoing balance between osteoblasts and osteoclasts is responsible for what?

the constant but subtle reshaping of bone.

What else is promoted by the sex hormones

the conversion of the epiphyseal plate to the epiphyseal line: bringing an end to the longitudinal growth of bones.

Any type of exercise will stimulate what? What type of exercise has a greater effect than cardiovascular activities.

the deposition of more bone tissue resistance training

Where does each epiphysis meet?

the diaphysis at the metaphysics, the narrow area that contains the epiphyseal plate (growth plate), a layer of hyaline (transparent) cartilage in a growing bone.

What does the periosteum cover?

the entire outer surface except where the epiphyses meet other bones to form joints.

the zone of calcified matrix connects what two things?

the epiphyseal plate to the diaphysis

What explains why damaged cartilage does not repair itself as readily as most tissues do?

the fact that it is avascular

What are the last bones to ossify via intramembranous ossification

the flat bones of the face, which reach their adult size at the end of the adolescent growth spurt.

The surface features of bones vary considerably, depending on what

the function and location in the body.

What happens if a bone isn't reset correctly after a fracture

the healing process will keep the bone in its deformed position.

What happens as the secreted matrix surrounding the osteoblast calcifies

the osteoblast become trapped within it: as a result, it changes in structure and becomes an osteocyte, the primary cell of mature bone and the most common type of bone cell.

What other hormones promote osteoblastic activity and production of bone matrix, and in addition, are responsible for the growth spurt that often occurs during adolescence.

the sex hormones (estrogen in girls, testosterone in boys)

Fractures are classified by what?

their complexity, location, and other features

What does hydroxyapatite crystals give bones?

their hardness and strength, while the collagen fibers give them flexibility so that they are not brittle.

Describe the skull and clavicles At birth.

they 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.

What happens to minerals incorporated into bone tissue

they can be released back into the bloodstream to maintain levels needed to support physiological processes.

a flat bone is typically

thin, but it is also often curved.

What is resistance training especially important for?

to slow down the eventual bone loss due to aging and for preventing osteoporosis.

Where can compact bone be found

under the periosteum and in the diaphyses of long bones, where it provides support and protection.

Describe the location of sesamoid bones

vary in number and placement from person to person but are typically found in tendons associated with the feet, hands, and knees.

How do osteoblasts produce new bone tissue beneath the periosteum?

via intramembranous ossification,

many people, especially those of darker complexion and those living in northern latitudes where the sun's rays are not as strong, are deficient in which vitamin

vitamin D

When does intramembranous ossification begin?

when mesenchymal cells in the embryonic skeleton gather together and begin to differentiate into specialized cells Some of these cells will differentiate into capillaries, while others will become osteogenic cells and then osteoblasts.

When does a bone grow in length?

when osseous tissue is added to the diaphysis.

During fetal development, what does the framework which is laid down determine?

where bones will form.

Where do the, the osteoblasts form a periosteal collar of compact bone around the cartilage of the diaphysis.

where the capillaries penetrate the cartilage during growth

The skeletal system performs what critical functions for the human body

• supports the body • facilitates movement • protects internal organs • produces blood cells • stores and releases minerals and fat