skeletal system

Sagittal Sectional View of the skull

Cutting the skull along a sagittal sectional plane reveals bones that form the cranial cavity and the nasal cavity. The cranial cavity is formed from a complex articulation of the frontal, parietal, temporal, occipital, ethmoid, and sphenoid bones.

Explain bone markings

Distinctive bone markings are the surface features that characterize each bone in the body. Articulating surfaces between adjacent bones tend to be smooth areas. Depressions on a bone provide space for a bony articulation, muscular structure, or other body component (e.g., lobes of brain). Projections from the bone surface mark the points where muscles, tendons, and ligaments attach. Openings and spaces through bones indicate sites for passageways for blood vessels and nerves.

facial bones

Facial bones form the face. They also protect the entrances to the digestive and respiratory systems. Touch your cheeks, your jaws, and the bridge of your nose; these bones are facial bones. The facial bones give shape and individuality to the face, form part of the orbit and nasal cavities, support the teeth, and provide for the attachment of muscles involved in facial expression and mastication (chewing). There are 14 facial bones, including the paired zygomatic bones, lacrimal bones, nasal bones, inferior nasal conchae, palatine bones, maxillae, and unpaired vomer and mandible.

The radius and ulna form the forearm

In anatomic position, these bones are parallel, and the radius is located more laterally. The proximal end of the radius has a distinctive disc-shaped head that articulates with the capitulum of the humerus. A narrow neck extends from the radial head to the radial tuberosity. The radial tuberosity is an attachment site for the biceps brachii muscle.

sutures of the vertebrae

Most vertebrae share some common structural features. The anterior region of each vertebra is a thick, cylindrical body, or centrum, which is the weight-bearing structure of each vertebra. Posterior to the vertebral body is the vertebral arch, also called the neural arch. The body together with the vertebral arch enclose an opening called the vertebral foramen. All the stacked vertebral foramina collectively form a superior-to-inferior directed vertebral canal that contains the spinal cord. Lateral openings between adjacent vertebrae are the intervertebral foramina. The intervertebral foramina provide a horizontally directed passageway through which spinal nerves extend to various parts of the body.

Explain sutures

Sutures are immovable fibrous joints that form the boundaries between the cranial bones. Dense regular connective tissue connects cranial bones firmly together at a suture. The sutures often have intricate, interlocking forms resembling puzzle pieces.

the pelvis

The adult pelvis is composed of four bones: the sacrum, the coccyx, and the right and left ossa coxae, also known simply as the hip bones. The pelvis protects and supports the viscera in the inferior part of the ventral body cavity

Explain the appendicular skeleton

The appendicular skeleton includes the bones of the upper and lower limbs, and the girdles of bones that attach the upper and lower limbs to the axial skeleton. The pectoral girdle consists of bones that hold the upper limbs in place, whereas the pelvic girdle consists of bones that hold the lower limbs in place.

Identify and describe the auditory ossicles.

The auditory ossicles and the hyoid bone are bones of the axial skeleton associated with the skull. Auditory ossicles are three tiny ear bones housed within the petrous part of each temporal bone. These bones—the malleus, the incus, and the stapes

Explain axial skeleton

The axial skeleton is so named because it is composed of the bones along the central axis of the body, which include the bones of the skull, vertebral column, sternum, and ribs. The main function of the axial skeleton is to form a framework that supports and protects the organs. Additionally, the spongy bone of most of the axial skeleton contains hematopoietic tissue that is responsible for blood cell formation

the tarsals, metatarsals, and phalanges of the lower limb.

The bones that form the ankle and foot are the tarsals, metatarsals, and phalanges. The seven tarsals of the ankle and proximal foot are similar to the eight carpal bones of the wrist in some respects, although their shapes and arrangement are different from those of their carpal bone counterparts.

the carpals, metacarpals, and phalanges of the upper limb.

The bones that form the wrist and hand are the carpals, metacarpals, and phalanges. The carpals are small, short bones that form the wrist. They are arranged in two rows of four bones each and allow for the multiple movements possible at the wrist.

The orbital complex

The bony cavities called orbits enclose and protect the eyes and the muscles that move them. The orbital complex consists of seven bones that form each orbit: the sphenoid, frontal, zygomatic, maxilla, palatine, ethmoid and lacrimal bones

Bones of the Thoracic Cage

The bony framework of the chest is called the thoracic cage and consists of the thoracic vertebrae posteriorly, the ribs laterally, and the sternum anteriorly. The thoracic cage acts as a protective enclosure around the thoracic organs and provides attachment points for many muscles.

Identify and describe the clavicle and its landmarks.

The clavicle, commonly known as the collarbone, is an elongated, S-shaped bone that extends between the manubrium of the sternum and the acromion of the scapula. Its sternal end (medial end) is roughly pyramidal in shape and articulates with the manubrium of the sternum, forming the sternoclavicular joint. The acromial end (lateral end) of the clavicle is broad and flattened. The acromial end articulates with the acromion of the scapula, forming the acromioclavicular joint. You can palpate your own clavicle by first locating the superior aspect of your sternum and then moving your hand laterally. The curved bone you feel under your skin, and close to the neck opening of your shirt, is your clavicle.

Identify and describe the scapula and its features.

The scapula is a broad, flat, triangular bone that forms the shoulder blade. The spine of the scapula is a ridge of bone on the posterior aspect of the scapula. It is easily palpated under the skin. The spine is continuous with a larger, flattened, posterior process called the acromion, which forms the bony tip of the shoulder. The acromion of the scapula articulates with the acromial end of the clavicle. The coracoid process is the smaller, more anterior, hook-shaped projection that is a site for muscle attachment.

How is the skeleton divided?

The skeletal system is organized into two divisions: the axial skeleton and the appendicular skeleton

the tibia and fibula and their features.

The skeleton of the leg has two parallel bones: the thick, strong tibia and the slender fibula. Like the radius and ulna, these two bones are connected by an interosseous membrane that extends between their interosseous borders. The interosseous membrane stabilizes the relative positions of the tibia and fibula and provides a pivot of minimal rotation for the two bones.

the skull

The skull is composed of both cranial and facial bones. Cranial bones form the rounded cranium, which completely surrounds and encloses the brain. The cranium consists of eight bones that form a roof and a base. The roof of the cranium, called the calvaria, is composed of the superior part of the frontal bone, the parietal bones, and a small part of the occipital bone. The base of the cranium is composed of portions of the frontal, ethmoid, sphenoid, occipital, and temporal bones

superior view of skull

The superior view of the skull primarily shows four of the cranial bones: the frontal bone, both parietal bones, and the occipital bone. The articulation between the frontal and parietal bones is the coronal suture, so named because it runs along a coronal plane. The sagittal suture, so named because it runs along a sagittal plane, connects the left and right parietal bones along the midline of the skull.

pelvic girdle

The term pelvic girdle refers to both the left and right ossa coxae only. The pelvic girdle articulates with the trunk and provides an attachment point for each lower limb

Bones of the Upper Limb

The upper limb consists of the brachium (arm), antebrachium (forearm), and hand. The complex structure of the hand in particular gives humans' capabilities beyond those of most other vertebrates. Each upper limb contains a total of 30 bones: 1 humerus, located in the brachium region 1 radius and 1 ulna, located in the antebrachium region 8 carpal bones, which form the wrist 5 metacarpal bones, which form the palm of the hand 14 phalanges, which form the fingers

vertebral column (spine)

The vertebral column provides vertical support for the body and supports the weight of the head. It helps maintain an upright body position. Most important, it houses and protects the delicate spinal cord.

Inferior (Basal) View

When the top of the skull is cut and removed, the internal view of the cranial base is revealed. Here we see the frontal bone surrounding the delicate cribriform plate of the ethmoid bone. The plate has numerous perforations called the cribriform foramina, which provide passageways for the olfactory nerves into the superior portion of the nasal cavity. The anteromedial part of the cribriform plate exhibits a midsagittal elevation called the crista galli , to which the cranial dural septa of the brain attach

Paranasal Sinuses

air-filled cavities lined with mucous membrane, located in the bones of the skull

Cranial Fossae

anterior, middle, posterior

Articulation between lumbar vertebrae, posterior view.

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Patella

kneecap The patella is a sesamoid bone located within the tendon of the quadriceps femoris muscle.

the atlas and axis C2

posterior-superior view

Superior view of a thoracic vertebra.

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Anterior View of Skull (sagittal cut)

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the axis C2

second cervical vertebrae

\ Transverse arch as seen in cross-sectional view

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Sacrum and coccyx posterior view

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Articulation between lumbar vertebrae, lateral view.

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Lateral View of Skull

A lateral view of the skull shows one parietal bone, temporal bone, and zygomatic bone. This view also shows part of the maxilla, mandible, frontal bone, and occipital bone. The superior and inferior temporal lines arc across the surface of the parietal and frontal bones and mark the attachment sites for the temporalis muscle. The small lacrimal bone articulates with the maxilla anteriorly and with the ethmoid bone posteriorly. A portion of the sphenoid bone articulates with the frontal, parietal, and temporal bones. This region is called the pterion and is circled. The pterion includes the H-shaped set of sutures of these four articulating bones.

Anterior View of Skull

An anterior view shows several major bones of the skull. The frontal bone forms the forehead. The left and right orbit are formed from a complex articulation of multiple skull bones. There are two large openings within each orbit called the superior orbital fissure and the inferior orbital fissure. Superior to the orbits on the anterior surface of the frontal bone are the superciliary arches, otherwise known as the brow ridges. The left and right nasal bones form the bony bridge of the nose. Superior to the nasal bones and between the orbits is a landmark area called the glabella.

(b) Lateral longitudinal arch.

Arch extending from the heel to the little toe

the largest sutures

The coronal suture extends laterally across the superior surface of the skull along a coronal plane. It represents the articulation between the frontal bone and the parietal bones. The lambdoid suture extends like an arc across the posterior surface of the skull. This suture is the site where the parietal bones and the occipital bone articulate. It is named for the Greek letter lambda, which its shape resembles. The sagittal suture extends between the coronal and lambdoid sutures along the midsagittal plane. It is the site where the right and left parietal bones articulate. A squamous suture on each side of the skull is the site where the temporal bone and the parietal bone of that side articulate. The squamous part of the temporal bone typically overlaps the parietal bone.

The femur

The femur is the longest bone in the body as well as the strongest and heaviest. The nearly spherical head of the femur articulates with the os coxae at the acetabulum. There is a small depression within the head of the femur, called the fovea, or fovea capitis. Here a small ligament connects the head of the femur to the acetabulum. Distal to the head, an elongated, constricted neck joins the shaft of the femur at an angle. This results in a medial angling of the femur, which brings the knees closer to the midline.

the atlas C1

The first cervical vertebra, called the atlas, supports the head through its articulation with the occipital condyles of the occipital bone. The atlas is readily distinguished from the other vertebrae because it lacks both a body and a spinous process. Instead, the atlas has lateral masses that are connected by semicircular anterior and posterior arches, each containing slight protuberances, the anterior and posterior tubercles. The atlas has depressed, oval superior and inferior articular facets that articulate with the occipital condyles and the axis (C2), respectively. Finally, the atlas has an articular facet for dens on its anterior arch.

Medial longitudinal arch.

The highest of the three arches of the foot; composed of the calcaneus, talus, navicular, cuneiforms, and the first three metatarsals.

the humerus and its features

The humerus is the longest and largest upper limb bone. Its proximal end has a hemispherical head that articulates with the glenoid cavity of the scapula. The prominent greater tubercle is positioned lateral to the head and helps form the rounded contour of the shoulder. The lesser tubercle is smaller and located more medial to the head. Between the two tubercles is the intertubercular sulcus (also called bicipital sulcus or bicipital groove), a depression that contains the tendon of the long head of the biceps brachii muscle.

Describe the structure and function of the hyoid bone.

The hyoid bone is a slender, U-shaped bone located inferior to the skull between the mandible and the larynx It does not articulate with any other bone in the skeleton. The hyoid has a medial body and two paired, hornlike processes, the greater cornua and the lesser cornua. The cornua and body serve as attachment sites for tongue and anterior neck muscles and ligaments

The lower limb

The lower limb is made up of the thigh, leg, and foot. The structure of the foot enables it to support the body during bipedal walking and running. The arrangement and numbers of bones in the lower limb are similar to those of the upper limb. Each lower limb contains a total of 30 bones: 1 femur, located in the femoral region 1 patella (kneecap), located in the patellar region 1 tibia and 1 fibula, located in the crural region 7 tarsal bones, which form the bones of the ankle and proximal foot 5 metatarsal bones, which form the arched part of the foot 14 phalanges, which form the toes

The nasal complex

The nasal complex is composed of bones and cartilage that enclose the nasal cavity and the paranasal sinuses

The os coxae

The os coxae is commonly referred to as the hip bone. Each os coxae is formed from three separate bones: the ilium, ischium, and pubis

The pelvic brim

The pelvic brim is a continuous, oval ridge that extends from the pubic crest, pectineal line, and arcuate line to the rounded inferior edges of the sacral ala and promontory. This pelvic brim helps subdivide the entire pelvis into a true pelvis and a false pelvis. The true pelvis, also known as the lesser pelvis, lies inferior to the pelvic brim. It encloses the pelvic cavity and forms a deep bowl that contains the pelvic organs. The false pelvis, also known as the greater pelvis, lies superior to the pelvic brim. It is enclosed by the alae of the ilia. It forms the inferior region of the abdominal cavity and houses the inferior abdominal organs.

superior view of skull posterior position

The posterior view of the skull shows a portion of the occipital, parietal, and temporal bones, as well as the entire lambdoid suture between the occipital and parietal bones. Within the lambdoid suture, there may be one or more sutural bones, which are bones completely within a suture. The external occipital protuberance is a prominence on the posterior aspect of the skull. Palpate the back of your head; males tend to have a prominent, pointed external occipital protuberance, whereas females have a more subtle, rounded protuberance. Intersecting the external occipital protuberance are two horizontal ridges, the superior and inferior nuchal lines

Describe how ribs are categorized and identify the features found on all ribs.

The ribs are elongated, curved, flattened bones that extend from the thoracic vertebrae to the anterior thoracic wall. Both males and females have 12 pairs of ribs. Ribs 1-7 are called true ribs. True ribs articulate directly and individually to the sternum by separate cartilaginous extensions called costal cartilages. The smallest true rib is the first.

sacrum and coccyx

The sacrum is an anteriorly curved, somewhat triangular bone that forms the posterior wall of the pelvic cavity. The apex of the sacrum is a narrow, pointed portion of the bone that projects inferiorly, whereas the bone's broad superior surface forms the base.