6 & 7

what four bones make up the pectoral girdle? which of these bones attach to the axial skeleton?

The pectoral girdle, or shoulder girdle, consists of a clavicle anteriorly and a scapula posteriorly. The paired pectoral girdles and their associated muscles form the shoulders. The term girdle implies a belt completely circling the body, but these girdles do not quite satisfy this description: Anteriorly, the medial end of each clavicle joins to the sternum and first rib, and the lateral ends of the clavicles join to the scapulae at the shoulder. However, the two scapulae fail to complete the ring posteriorly, because their medial borders do not join each other or the axial skeleton.

what are the special features of the axis (C2)? What is the dens? What is its function?

The axis, which has a body, a spinous process, and the other typical vertebral processes, is not as specialized as the atlas. It's only unusual feature is the knoblike dens projecting superiorly from its body. The dens is actually the "missing" body of the atlas that fuses with the axis during embryonic development. Cradled in the anterior arch of the atlas, the dens acts as a pivot for the rotation of the atlas and skull. Hence, this joint participates in rotating the head from side to side to indicate "no." Axis is a good name for the second cervical vertebra because its dens allows the head to rotate on the neck's axis.

what are the regions that form the thoracic cage? what is its function?

The bony framework of the chest (thorax), called the thoracic cage, is roughly barrel-shaped and includes the thoracic vertebrae posteriorly, the ribs laterally, and the sternum and costal cartilages anteriorly. The thoracic cage forms a protective cage around the heart, lungs, and other organs. It also supports the shoulder girdles and upper limbs and provides attachment points for many muscles of the back, neck, chest, and shoulders. In addition, the intercostal spaces are occupied by the intercostal muscles, which lift and depress the thorax during breathing.

Name the bones that make up the axial skeleton?

It has 80 named bones arranged into three major regions: the skull, vertebral column, and thoracic cage. This axial division of the skeleton supports the head, neck, and trunk, and protects the brain, spinal cord, and the organs in the thorax.

How are the vertebrae held together vertically by ligaments?

Like a tremulous telecommunication transmitting tower, the vertebral column cannot stand upright by itself. It must be held in place by an elaborate system of supports. Serving this role are the strap like ligaments of the back and the muscles of the trunk. The major supporting ligaments are the anterior and posterior longitudinal ligaments that run vertically along the anterior and posterior surfaces of the bodies of the vertebrae, from the beck to the sacrum.

inferior angle

Like all triangles, the scapula has three corners, or angles. The glenoid cavity lies at the scapula's lateral angle

what are the major parts of the appendicular skeleton?

Limb bones and their girdles are appended, or attached, to the axial skeleton. Thus, they are collectively called the appendicular skeleton. The pectoral girdles attach the upper limbs to the trunk, whereas the pelvic girdle secures the lower limbs. Although the bones of the upper and lower limbs differ in their functions, they share the same basic structural plan. That is, each limb is composed of three basic segments, from proximal to distal: the arm, forearm, and hand in the upper limb; and the thigh, leg, and foot in the lower limb.

ischial spine and ischial tuberosity

The ischium forms the posteroinferior region of the hip bone. Shaped like an arc, it has a thicker, superior body and a thinner, inferior ramus. Anteriorly, the ischial ramus joins the pubis. The triangular ischial spine lies posterior to the acetabulum and projects medially. It is an attachment point for a ligament from the sacrum and coccyx, the sacrospinous ligament. The interior surface of the ischial body is the rough and thickened ischial tuberosity, the strongest part of the hip bone. When you sit, your weight is borne entirely by the ischial tuberosities. A massive sacrotuberous ligament runs from the sacrum to each ischial tuberosity and helps hold the pelvis together. The ischial tuberosity is also an area of attachment of the hamstring muscles.

glenoid cavity

A cavity that articulates with the humerus and forms the shoulder joint

describe the structure and location of the humerus, including what bones it articulates with.

Anatomists use the term arm or brachium to designate the part of the upper limb between the shoulder and elbow only. The humerus is the only bone of the arm. The largest and longest bone in the upper limb, it articulates with the scapula at the shoulder and with the radius and ulna (forearm bones) at the elbow.

what two bones make up the forearm? how are they connected to one another along their length? how are they arranged in the anatomical position? when the palms are facing posteriorly how are they arranged?

Forming the skeleton of the forearm, or antebrachium, are two parallel long bones, the radius and ulna, that articulate with the humerus proximally and the bones of the wrist distally. The radius and ulna also articulate with each other both proximally and distally at the small radioulnar joints. Furthermore, they are interconnected along their entire length by a flat ligament called the interosseous membrane. In the anatomical position, the radius lies laterally (on the thumb side), and the ulna medically. However, when the palm faces posteriorly, the distal end of the radius crosses over the ulna, and the two bones form an X.

medial malleolus

Forms the medial bulge of the ankle

How does this affect the function of the vertebral column?

From a lateral view, four curvatures that give the vertebral column an S shape are visible. The cervical and lumbar curvatures are concave posteriorly, whereas the thoracic and sacral curvatures are convex posteriorly. These curvatures increase the resilience of the spine, allowing it to function like a spring rather than a straight, rigid rod.

vertebral foramen

- hole in the vertebra that allows the spinal cord to pass through • The large hole encircled by the body and vertebral arch is the vertebral foramen. Successive vertebral foramina of the articulated vertebrae form the long vertebral canal, through which the spinal cord and spinal nerve roots pass.

What is the hyoid bone? Where is it located? Why is it unique? What is its function?

- located inferior to the mandible, anterior to the neck - does not articulate with any bone - acts as a movable base for the tongue

Describe the regional characteristics of cervical vertebrae (C3-C7)

-body: small, wide side to side -spinous process: forked and projects posteriorly -vertebral foramen: triangular -transverse process: contains foramina -superior articulating process is directed superioposteriorly -cervical is the spine region with maximum movement

what are these bones called (in the vertebral column) and how are they separated?

1. cervical (7 vertebrae) 2. thoracic curvature (12 vertebrae) 3. lumbar curvature (5 vertebrae) 4. sacral curvature (5 fused vertebrae sacrum) 5. coccyx (4 fused vertebrae)

talus

articulates with the fibula and the tibia

trochlea of the talus

articulates with tibia

head

at proximal end of the humerus, hemispherical shape, articulates with the glenoid cavity if the scapula.

trochlea

at the distal end of the humerus, the medial of two condyles, articulates with the trochlear notch of the ulna

what is the difference between the true pelvis and the false pelvis? what organs are housed in each one?

false (greater) pelvis is superior to the pelvic brim and holds abdominal organs includes the area within the ilium. true (lesser) pelvis is blow the arcuate line, inferior to the false pelvis, and contain pelvic organs

tibial tuberosity

inferior to the condyles, on the tibia's anterior surface, is the tibial tuberosity, which is the attachment site of the patellar ligament.

lateral condyle

lateral of two condyles of the tibia, proximal end, articulates with the lateral condyle of the femur

medial condyle

medial of two condyles of the tibia, proximal end, articulates with the medial condyle of the femur

what are the metatarsals? how are they named? what do they articulate with?

metatarsals are numbered I-V, medial to lateral. The first metatarsal at the base of the big toe is the largest, and it plays an important role in supporting the weight of the body. The metatarsals are more nearly parallel to one another than are the metacarpals in the palm. Distally, where the metatarsals articulate with the proximal phalanges of the toes, the enlarged head of the first metatarsal forms the "ball" of the foot.

head of the femur

proximal ball-like end of the femur, articulates with the acetabulum of the coxa

pisiform

proximal row, most medial (away from thumb). the pisiform can only be seen anteriorly in anatomical positioning.

body of the sternum

the body, or mid portion, makes up the bulk of the sternum. It is formed from four separate bones, one inferior to the other, that fused after puberty. The sides of the sternum body are notched where it articulates with the costal cartilages of the second to seventh ribs

what parts of a rib articulate with what parts of a vertebrae?

the head of rib 4 articulates with the inferior costal facet of T3 and the superior costal facet of T4. The tubercle articulates with the transverse facet of T4

what are the three regions of the coxa (hip bones)? what is the acetabulum?

three regions are the ilium, ischium, and pubis. the acetabulum is the socket on the lateral pelvis that holds the head of the femur. all three regions of the coxa are part of the acetabulum.

transverse process

• A transverse process projects laterally from each pedicle-lamina junction. As with the spinous process, the transverse processes are attachment sites for muscles and ligaments.

inferior articular process and facet superior articular process and facet

• Articular processes protrude superiorly and inferiorly from the pedicle-lamina junctions and form movable joints between successive vertebrae: The inferior articular processes of each vertebra joins with the superior articular processes of the vertebra immediately inferior. Successive vertebrae are joined by both intervertebral discs and by these articular processes. The smooth joint surfaces of these processes are facets.

intervertebral foramina

• Notches on the superior and inferior borders of the pedicles form lateral openings between adjacent vertebrae, the intervertebral foramina. Spinal nerves from the spinal cord pass through these foramina.

spinous process

• The spinous process is the median, posterior projection arising at the junction of the two laminae. It is an attachment site for muscles and ligaments that move and stabilize the vertebral column.

vertebral arch (composed of pedicles and laminae)

• The vertebral arch forms the posterior portion of the vertebra. It is composed of two pedicles and two laminae. The pedicles are short, bony walls that project posteriorly from the vertebral body and form the sides of the arch. The two laminae are flat, bony plates that complete the arch posteriorly, extending from the transverse processes to the spinous process. The vertebral arch protects the spinal cord and spinal nerves located in the vertebral foramen.

body of the spinal column

• the anterior portion of the vertebra is the disc-shaped body. The body is the weight-bearing region of the vertebra.

greater tubercle, lesser tubercle, intertubercular sulcus, deltoid tuberosity, capitulum, and olecranon fossa

Inferior to the anatomical neck is the lateral greater tubercle and the more medial lesser tubercle are separated by the intertubercular sulcus, or bicipital groove. The tubercles are sites of attachment for the rotator cuff muscles. The intertubercular sulcus guides a tendon of the biceps muscle to its attachment point at the rim of the glenoid cavity (the supraglenoid tubercle). About midway down the shaft, on the lateral side, is the deltoid tuberosity. This V-shaped, roughened area is an attachment site for the deltoid muscle of the shoulder. The lateral capitulum articulates with the radius. On the posterior surface of the humerus directly proximal to the trochlea is the deep olecranon fossa.

clavicular notches

It's clavicular notches articulate with the clavicles (collarbones) superolaterally. Just below this, the manubrium articulates with the first and second ribs.

sternal angle

Just inferior is the sternum angle, a horizontal ridge across the anterior surface of the sternum where the manubrium joins the body. This fibrocartilage joint acts like a hinge, allowing the sternum body to swing anteriorly when we inhale. The sternum angle is in line with the disc between the fourth and fifth thoracic vertebrae. Anteriorly, it lies at the level of the second ribs. It is a handy reference point for finding the second rib. Once the second rib is located, you can count down to identify all the other ribs (except the first and sometimes the twelfth, which are top deep to palpated). By locating the individual ribs, you attain a series of horizontal lines of "latitude" by which to locate the underlying visceral organs of the thoracic cavity

What are the special features of the atlas (C1)? What is its function?

The atlas lacks a body and a spinous process. Essentially, it is a ring of bone consisting of anterior and posterior arches, plus a lateral mass on each side. Each lateral mass has articular facets on both its superior and inferior surfaces. The superior articular facets receive the occipital condyles of the skull. Thus, they "carry" the skull, just as the giant Atlas supported the heavens in Greek mythology. These joints participate in flexion and extension of the head on the neck, as when you nod "yes." The inferior articular facets form joints with the axis.

describe the clavicles and their location, noting the acromial end and sternal end. what are the functions of the clavicles?

The clavicles, or collarbones, are slender, S-shaped bones that extend horizontally across the superior thorax pm the anterior surface. The cone-shaped sterna end attaches to the manubrium medically, and the flatted acromegaly end articulates with the scapula laterally. The medial two-thirds of the clavicle is convex anteriorly; you can feel this anterior projection on yourself when you palpate the clavicle. The lateral third is concave anteriorly. The superior surface is almost smooth, but the inferior surface is ridged and grooved for the ligaments and muscles that attach the clavicle to the rib cage and scapula. The thick trapezoid line and the conoid tubercle near the acromial end provide attachment for a ligament that runs to the scapula's coracoid process, and a roughened area near the sternum end is the attachment site of the costoclavicular ligament, a ligament that connects the clavicle to the first rub. The clavicles perform several functions. Besides providing attachments for muscles, they act as braces that hold the scapulae and arms out laterally from the thorax. This function becomes obvious when a clavicle is fractured: The entire shoulder region collapses medically. The clavicles also transmit compression forces from the upper limbs to the axial skeleton, as when someone puts both arms forward and pushes a car to a gas station.

Describe the structure and function of the coccyx.

The coccyx, or tailbone, is small and triangular. The name coccyx is from a Greek word for "cuckoo," and the bone was so named because of a fancied resemblance to a bird's beak. The coccyx consists of three to five vertebrae fused together. Except for the slight support it affords the pelvic organs, it is an almost useless bone. Injury to the coccyx, such as from an abrupt fall, is extremely painful. Occasionally, a baby is born with an unusually long coccyx. In most cases, this bony "tail" is discreetly snipped off by a physician.

coracoid process

The coracoid process projects anteriorly from the lateral part of the superior scapular border. The root corac means "like a crow's beak," but this process looks more like a bent finger. It is an attachment point for the biceps muscle of the arm. Strong ligaments also bind the coracoid process to the clavicle.

what are the three segments of the lower limb?

The lower limbs carry the entire weight of the erect body and experience strong forces when we jump or run. Thus, the bones of the lower limbs are thicker and stronger than the comparable bones of the upper limbs. The three segments of the lower limb are the thigh, the leg, and the foot.

describe the scapulae (shoulder blades) and their location, noting the following features. what is the function of the scapulae?

The scapulae, or shoulder blades, are thin, triangular flat bones located on the dorsal surface of the rib cage, between rib 2 superiorly and rib 7 inferiorly. Each scapula has three borders. The superior border is the shortest and sharpest. The medial border, or vertebral border, parallels the vertebral column. The thick lateral border, or axillary border, abuts the axilla (armpit) and ends superiorly in a shallow fossa, the glenoid cavity. This cavity articulates with the humerus, forming the shoulder joint.

acromion

The spine ends laterally in a flat projection, the acromion, which articulates with the acromial end of the clavicle

What is the vertebra prominens?

The spinous process of C7 is not forked and is much larger than those of the other cervical vertebrae. Because its large spinous process can be seen and felt through the skin, C7 is called the vertebrae prominens and is used as a landmark for counting the vertebrae in living people. To locate this landmark, run your fingers inferiorly along the back of your neck, in the posterior midline, where you can feel the spinous processes of the cervical vertebrae. The spine of C7 is especially prominent.

describe the structure and functions of the sternum.

The sternum lies in the anterior midline of the thorax. Resembling a dagger, it is a flat bone about 15 cm long consisting of three sections: the manubrium, body, and diploid process.

what is the difference between true, false, and floating ribs?

The superior seven pairs, which attach directly to the sternum by their costal cartilages, are the true ribs, or vertebrosternal ribs. The inferior five pairs, ribs 8-12, are called false ribs because they attach to the sternum either indirectly or not at all. Ribs 8-10 attach to the sternum indirectly, as each joins the costal cartilage above it; these are called vertebrochondral ribs. Ribs 11 and 12 are called floating ribs, or vertebral ribs, because they have no anterior attachments. Instead, their costal cartilages lie embedded in the muscles of the lateral body wall.

how many pairs of ribs are there? with what vertebrae do they articulate?

Twelve pairs of ribs form the flaring sides of the thoracic cage. All ribs attach to the thoracic vertebrae posteriorly and run anteroinferiorly to reach the front of the chest.

transverse costal facet

With the exception of T11 and T12, the transverse processes have facets that articulate with the tubercles of the ribs called transverse costal facets

manubrium

The manubrium, the superior section, is shaped like the knot in a necktie

describe the typical structure of a rib using the terms head, neck, tubercle, and shaft (body)

A typical rib is a bowed flat bone. The bulk of a rib is simply called the shaft or body. It's superior border is smooth, but its inferior border is sharp and thin and has a costal groove on its inner face. The intercostal nerves and vessels are located in the costal groove. In addition to the shaft, each rib has a head, neck, and tubercle. The wedge-shaped head articulates with the vertebral bodies by two facets: One facet joins the body of the thoracic vertebra of the same number; the other joins the body of the vertebra immediately superior. The neck of a rib is the short, constricted region just lateral to the head. Just lateral to the neck on the posterior surface, the knoblike tubercle articulates with the transverse process of the thoracic vertebra of the same number. Lateral to the tubercle at the angle of the rib, the shaft curves sharply anteriorly and extends to the costal cartilage anteriorly. The costal cartilages provide secure but flexible attachments of ribs to the sternum and contribute to the elasticity of the thoracic cage.

scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate, hamate

A wristwatch is actually worn on the distal forearm, not on the wrist at all. The true wrist, or carpus, is the proximal region of the hand, just distal to the wrist joint. The carpus contains eight marble-sized short bones, or carpals, closely united by ligaments. Gliding movements occur between the carpals, making the wrist rather flexible. The carpals are arranged in two irregular rows of four bones each. In the proximal row, from lateral (thumb side) to medial, are the scaphoid, lunate, triquetrum, and pisiform bones. Only the scaphoid and lunate bones articulate with the radius to form the wrist joint. The carpals of the distal row, again from lateral to medial, are the trapezium, trapezoid, capitate, and hamate bones. The scaphoid is the most frequently fractured carpal bone, which often results from falling on an outstretched hand. The impact bends the scaphoid, which then breaks at its narrow midregion.

what two bones make up the anatomical leg? what are their locations relative to each other? what connects them along their lengths?

Anatomists use the term leg to refer to the part of the lower limb between the knee and the ankle. Two parallel bones, the tibia and fibula, form the skeleton of the leg. The tibia, located medially, is more massive than the sticklike fibula. These two bones articulate with each other both superiorly and inferiorly. However, unlike the joints between the radius and ulna of the forearm, the tibiofibular joints allow almost no movement. An interosseous membrane connects the tibia and fibula along their entire length. The tibia articulates with the femur to form the knee joint, and with the talus bone of the foot at the ankle joint. The fibula does not contribute to the knee joint and merely helps stabilize the ankle joint.

greater trochanter, lesser trochanter, lateral condyle, medial condyle, and patellar surface

At this junction of the shaft and neck are the lateral greater trochanter and posteromedial lesser trochanter, sites of muscle attachment. The two trochanter are interconnected by the intertrochanter line anteriorly and by the prominent intertrochanteric chest posteriorly. Inferior to the intertrochanteric crest on the posterior surface of the shaft is the gluteal tuberosity. The inferior part of this tuberosity blends into a long vertical ridge, the linea aspera. these areas are also sites of muscle attachment. Distally, the femur broadens to end in lateral and medial condyles shaped like wide wheels. These are the joint surfaces that articulate with the tibia. The most raised points on the sides of these condyles are the lateral and medial epicondyles, to which muscles and ligaments attach. Anteriorly, the two condyles are separated by a smooth patellar surface, which articulates with the kneecap, or patella. Posteriorly, the condyles are separated by a deep intercondylar fossa. Extending superiorly from the respective condyles to the linea aspera are the lateral and medial supracondylar lines.

why is there great motility in the pectoral girdle?

Besides attaching the upper limb to the trunk, the pectoral girdle provides attachment for many muscles that move that limb. This girdle is light and allows the upper limbs to be quite mobile. This mobility results from two factors: 1. Because only the clavicle attaches to the axial skeleton, the scapula can move quite freely across the thorax, allowing the arm to move with it. 2. The socket of the shoulder joint—the scapula's glenoid cavity—is shallow, so it does not restrict the movement of the humerus (arm bone). Although this arrangement is good for flexibility, it is bad for stability: Shoulder dislocations are fairly common.

what is an intervertebral disc? what is its function?

Each intervertebral disc is a cushionlike pad composed of an inner sphere, the nucleus pulposus, and an outer collar of about 12 concentric rings, the anulus fibrosus. Each nucleus pulposus is a gelatinous and acts like a rubber ball, enabling the spine to absorb compressive stress. In the anulus fibrosus, the outer rings consist of ligament and the inner ones consist of fibrocartilage. The main function of these rings is to contain the nucleus pulposus, limiting its expansion when the spine is compressed. However, the rings also function like a woven strap, binding the successive vertebrae together, resisting tension on the spine, and absorbing compressive forces. Collagen fibers in adjacent rings in the anulus cross like an X, allowing the spine to withstand twisting. This arrangement creates the same antitwisting design provided by bone lamellae in osteons. The intervertebral discs acts as shock absorbers during walking, jumping, and running. At points of compression, the discs flatten and bulge out a bit between the vertebrae. The discs are thickest in the lumbar (lower back) and cervical (neck) regions of the vertebral column. Collectively, the intervertebral discs make up about 25% of the height of the vertebral column. As a result of compression and loss of fluid from the gelatinous nucleus pulposus, they flatten somewhat by the end of each day. So, you are probably 1 to 2 cm shorter at night than when you awake in the morning.

what are the metacarpals? how are they named? what do they articulate with?

Five metacarpals radiate distally from the wrist to form the metacarpus, or the palm of the hand. These small long bones are not named individually but instead are numbered I to V, from thumb to little finger. The buses of the metacarpals articulate with the carpals proximally and with each other on their lateral and medial sides. Distally, the bulbous heads of the metacarpals articulate with the proximal phalanges of the fingers to form knuckles. Metacarpal I, associated with the thumb, is the shortest and most mobile.

Describe the regional characteristics of thoracic vertebrae (T1-T12) What is the function of the superior, inferior, and transverse costal facets of thoracic vertebrae?

The 12 thoracic vertebrae, T1-T12, all articulate with ribs. The distinctive features of thoracic vertebrae are as follows: • From a superior view, the vertebral body is roughly heart-shaped • Laterally, each side of the vertebral body has two facets, commonly referred to as demifacets: The superior costal facet lies at the superior edge, and the inferior costal facet lies at the inferior edge. The heads of the ribs articulate with these facets. For most ribs, the head of the rib is attached to the bodies of two vertebrae, the inferior costal facet of the superior vertebra and the superior costal facet of the inferior vertebra. Vertebra T1 differs from this general pattern in that its body bears a full facet for the first rib and a demifacet for the second rib; furthermore, the bodies of T10-T12 have only single facets to receive their respective ribs. • The spinous process is long and points inferiorly • The vertebral foramen is circular • With the exception of T11 and T12 the transverse processes have facets that articulate with the tubercles of the ribs called transverse costal facets • The superior and inferior articular facets, which join adjacent vertebrae, lie mainly in the frontal plane; that is, the superior articular facets face posteriorly, whereas the inferior articular facets face anteriorly. Such articulations limit flexion and extension, but they allow rotation between successive vertebrae. Much of the ability to rotate the trunk comes from the thoracic region of the vertebral column. Lateral flexion is also possible but is restricted by the ribs.

what are the phalanges of the toes? how are they named? what do they articulate with?

The 14 phalanges of the toes are smaller than those of the fingers and thus are less nimble. Still, their general structure and arrangement are the same: There are three phalanges in each digit except the great toe (the hallux), which has only two phalanges. As in the hand, these toe bones are named proximal, middle, and distal phalanges.

anterior longitudinal ligament

The anterior longitudinal ligament is wide and attaches strongly to both the bony vertebrae and the intervertebral discs. Along with its supporting role, this thick anterior ligament prevents hyperextension of the back (bending too far backward)

Describe the structure and function of the sacrum, sacral promontory, transverse ridges, sacral canal, and median sacral crest.

The curved, triangular sacrum shapes the posterior wall of the pelvis. It is formed by five fused vertebrae (S1-S5); thus, most sacral features are modifications of the typical vertebral features. Superiorly, the sacrum articulates with L5 through a pair of superior articular processes and an intervertebral disc. Inferiorly, it joints the coccyx. The anterosuperior margin of the first sacral vertebra bulges anteriorly into the pelvic cavity as the sacral promontory. The human body's center of gravity lies about 1 cm posterior to this landmark. Four transverse ridges cross the anterior surface of the sacrum, marking the lines of fusion of the sacral vertebrae. The anterior sacral foramina transmit the ventral divisions (ventral rami) of the sacral spinal nerves. The large region lateral to these foramina is simply called the lateral part. This part expands superiorly into the flaring ala, which develops from fused rib elements of (S1-S5. (Embryonic rib elements form in association with all vertebrae; although they only become true ribs in the thorax. Elsewhere, they fuse into the ventral surfaces of the transverse processes.) The alarm articulate at the auricular surface with the two hip bones to form the sacroiliac joints of the pelvis. On the posterior surface, in the midline, is the bumpy median sacral crest, which represents the fused spinous processes of the sacral vertebrae. Lateral to it are the posterior sacral foramina, which transmit the dorsal rami of the sacral spinal nerves. Just lateral to these is the lateral sacral crest, representing the tips of the transverse processes of the sacral vertebrae. The vertebral canal continues within the sacrum as the sacral canal. The laminae of the fifth (and sometimes the fourth) sacral vertebrae fail to fuse medially, leaving an enlarged external opening called the sacral hiatus at the inferior end of the sacral canal.

what are the phalanges? how are they named? what subunits are they made of?

The digits, or fingers, are numbered I to V beginning with the thumb, or pollex. The fingers contain miniature long bones called phalanges. The singular of this term is phalanx. In most people, the third finger is the longest. With the exception of the thumb, each finger has three phalanges: proximal, middle, and distal. The thumb has no middle phalanx.

femur

The femur is the single bone of the thigh. It is the largest, longest, strongest bone in the body. It's durable structure reflects the fact that the stress on this bone can reach 280 kg per cm2, or 2 tones per square inch. The femur courses medially as it descends towards the knee. Such a medial course places the knee joints closer to the body's center of gravity in the midline and thus provides for better balance. The medial course of the femur is more pronounced in women because of their wider pelvis. Thus, there is a greater angle between the femur and the tibia (shinbone), which is vertical. This may contribute to the greater incidence of knee problems in female athletes.

head and lateral malleolus

The fibula, located lateral to the tibia, is a thin long bone with two expanded ends. It's superior end is its head, and its inferior end is the lateral malleolus. This malleolus forms the lateral bulge of the ankle and articulates with the talus bone of the foot. the shaft of the fibula is heavily ridged; the fibula does not bear weight, but several muscles originate from it.

How do ribs 1, 10, 11, and 12 differ from the other ribs?

The first rib is atypical because it is flattened from superior to inferior and is quite broad. The subclavian vessels, the large artery and vein servicing the upper limb, run in a groove along its superior surface. There are other exceptions to the typical rib pattern: rib 1 and ribs 10-12 articulate with only one vertebral body, and ribs 11 and 12 do not articulate with a vertebral transverse process

jugular notch

The jugular notch, also called the suprasternal notch, is the central indentation in the superior border of the manubrium. If you slide your finger down the anterior surface of your neck, it will land in the jugular notch. The jugular notch generally lies in the same horizontal plane as the disc between the second and third thoracic vertebrae.

iliac crest, anterior superior iliac spine, posterior superior iliac spine, and greater sciatic notch

The ilium is a large, flaring bone that forms the superior region of the hip bone. It consists of an inferior body and a superior winglike ala. The thickened superior margin of the ala is the iliac crest. Many muscles attach to this crest, which is thickest at the tubercle of the iliac crest. Each iliac crest ends anteriorly in a blunt anterior superior iliac spine and posteriorly in a sharp posterior superior iliac spine. The anterior superior iliac spine is an especially prominent anatomical landmark and is easily felt through the skin. The position of the posterior superior iliac spines is indicated by dimples in the skin that lie approximately 5 cm lateral to the midline of the back at the junction of the lumber and gluteal regions. Located inferior to the superior iliac spines are the anterior and posterior inferior iliac spines. Posteriorly, just inferior to the posterior inferior iliac spine, the ilium is deeply indented to form the greater sciatic notch. The sciatic nerve, the largest nerve in the body, passes through this notch to enter the posterior thigh.

Describe the regional characteristics of lumbar vertebrae (L1-L5). Why are the lumbar vertebrae the largest vertebrae?

The lumbar region of the vertebral column, the area commonly referred to as the small of the back, receives the most stress. The enhanced weight-bearing function of the five lumbar vertebrae (L1-L5) is reflected in their sturdy structure. The distinctive features of lumbar vertebrae are as follows: • The body is massive and appears kidney-shaped when viewed superiorly • The pedicles and laminae are shorter and thicker than those of other vertebrae • The spinous processes are short, flat, and hatchet-shaped, and they project straight posteriorly. These processes are robust for the attachment of large back muscles • The vertebral foramen is triangular • The superior articular facets face posteromedially (or medically), whereas the inferior articular facets face anterolaterally (or laterally), oriented approximately in the sagittal plane. Such articulations provide stability by preventing rotation between the lumbar vertebrae while allowing flexion and extension. The lumbar region flexes, for example, when you do sit-ups or bend forward to pick up a coin from the ground. Additionally, lateral flexion is allowed by this spinal region.

what is the patella? what type of bone is it and where is it found? what is its function?

The patella is a triangular sesamoid bone enclosed in the tendon that secures the quadriceps muscles of the anterior thigh to the tibia. It protects the knee joint anteriorly and improves the leverage of the quadriceps muscles acting across the knee.

what is the function of the pelvic girdle? how does it attach to the axial skeleton? what bones make up the pelvic girdle?

The pelvic girdle attaches to the lower limbs to the spine and supports the visceral organs of the pelvis. The full weight of the upper body passes through this girdle to the lower limbs. Whereas the pectoral girdle barley attaches to the thoracic cage, the pelvic girdle attaches to the axial skeleton by some of the strongest ligaments in the body. Furthermore, whereas the glenoid cavity of the scapula is shallow, the corresponding socket in the pelvic girdle is a deep cup that firmly secures the head of the femur (thigh bone). Consequently, the lower limbs have less freedom of movement than the upper limbs but are much more stable. The pelvic girdle consists of the paired hip bones and the sacrum (part of the axial skeleton). Each hip bone, also called a coxal or pelvic bone, unites with its partner anteriorly and with the sacrum posteriorly. The deep, basinlike structure formed by the hip bones, sacrum, and coccyx is the pelvis.

posterior longitudinal ligament

The posterior longitudinal ligament, which is narrow and relatively weak, attaches only to the intervertebral discs. This ligament helps prevent hyperflexion (bending the vertebral column too sharply forward). Several other posterior ligaments connect each vertebra to those immediately superior and inferior. Among these is the ligamentum flavum, which connects the lamina of adjacent vertebrae. It contains elastic connective tissue and is especially strong: It stretches as we bend forward, then recoils as we straighten to an erect position.

spine

The posterior surface bears a prominent spine that is easily felt through the skin.

superior ramus, inferior ramus, pubic tubercle, obturator foramen, and pubic symphysis

The pubis forms the anterior region of the hip bone. In the anatomical position, it lies nearly horizontally, and the bladder rests upon it. The pubis is V-shaped, with superior and inferior rami extending from a flat body. The body of the pubis lies medially, and its anterior border is thickened to form a pubic crest. At the lateral end of the pubic crest is the knoblike pubic tubercle, an attachment point for the inguinal ligament. The two rami of the pubic bone extends laterally: The inferior pubic ramus joins to the ischial ramus, and the superior pubic ramus joins with the bodies of the ischium and ilium. A thin ridge called the pectineal line lies along the superior pubic ramus, forming the anterior portion of the pelvic brim. A large hole, the obturator foramen, occurs between the pubis and ischium. Although a few vessels and nerves do pass through it, the obturator foramen is almost completely closed by a fibrous membrane, the obturator membrane. In fact, obturator means "closed up" In the midline, the bodies of the two public bones are joined by a disc of fibrocartilage. This joint is the pubic symphysis.

radial head, radial tuberosity, and radial styloid process

The radius is thin at its proximal end and widened at its distal end—the opposite of the ulna. The proximal head of the radius is shaped like the end of a spool of thread. It's superior surface is concave, and it articulates with the capitulum of the humerus. Medially, the head of the radius articulates with the radial notch of the ulna, forming the proximal radioulnar joint. Just distal to the head, on the anterior surface is anatomical position, is a rough bump, the radial tuberosity, a site of attachment of the biceps muscle. On the distal end of the radius, the medial ulnar notch articulates with the head of the ulna, forming the distal radioulnar joint, and the lateral radial styloid process anchors a ligament that runs to the wrist. The distal articular surface is concave and articulates with carpal bones of the wrist. Whereas the ulna contributes heavily to the elbow joint, the radius is the primary forearm bone contributing to the wrist joint. When the radius rotates, the hand moves with it.

talus, trochlea, calcaneus, calcaneal tuberosity, cuboid, navicular, medial, intermediate, and lateral cuneiforms

The tarsus makes up the posterior half of the foot and contains seven bones called tarsals. It is comparable to the carpus of the hand. The weight of the body is carried primarily by the two largest, most posterior tarsal bones: the talus, which articulates with the tibia and fibula superiorly, and the strong calcaneus, which forms the heel of the foot. The tibia articulates with the talus at the trochlea of the talus. Inferiorly, the talus articulates with the calcaneus. The thick tendon of the calf muscles attaches to the posterior surface of the calcaneus. The part of the calcaneus that touches the ground is the calcaneal tuberosity, and the medial, shelflike projection is the sustentaculum tail or talar shelf. The remaining tarsal bones are the lateral cuboid, the medial navicular, and the anterior medial, intermediate, and lateral cuneiform.

tibia

The tibia receives the weight of the body from the femur and transmits it to the foot. It is second only to the femur in size and strength.

What is the function of the transverse foramen in cervical vertebrae (C3-C7)?

The typical cervical vertebral, C3-C7, have the following distinguishing features • the body is wider laterally than in the anteroposterior dimension • Except in C7, the spinous process is short, projects directly posteriorly, and is bifid or forked; that is, it is split at its tip. • The vertebral foramen is large and generally triangular • Each transverse process contains a hole, a transverse foramen, through which the vertebral blood vessels pass. These vessels ascend and descend through the neck to help serve the brain • The superior articular facets face superoposteriorly, whereas the inferior articular facets face infernoanteriorly. Thus these articulations lie in an oblique plane. The orientation of these articulations allows the neck to carry out an extremely wide range of movements: flexion and extension, lateral flexion, and rotation.

what are the main differences between the male and female pelvis?

The typical male and female pelvis exhibit several differences. So consistent are these differences that an anatomist can determine the sex of a skeleton with 90% certainty merely by examining the pelvis. The female pelvis is adapted for childbearing: it tends to be wider, shallower, and lighter than that of a male. These features provide more room in the true pelvis, which must be wide enough for an infant's head to pass during birth.

olecranon process, coronoid process, ulnar head, and ulnar styloid process

The ulna, which is slightly longer than the radius, is the main bone forming the elbow joint with the humerus. It looks much like a monkey wrench. At the proximal end are two prominent projections, the olecranon and coronoid process, separated by a deep concavity, the trochlear notch. Together, these two processes grip the trochlea of the humerus, forming a hinge joint that allows the forearm to bend upon the arm (flex), then straighten again (extend). When the forearm is fully extended, the olecranon process "locks" into the olecranon fossa of the humerus. When the forearm is flexed, the coronoid process of the ulna fits into the coronoid fossa of the humerus. Distally, the shaft of the ulna narrows and ends in a knoblike head that articulates with the radius. Medial to this is the ulnar styloid process, from which a ligament runs to the wrist. The head of the ulna is separated from the bones of the wrist by a disc of fibrocartilage and plays little or no role in hand movements.

What are the functions of the vertebral column? How many bones are found in it?

The vertebral column, also called the spinal column or spine, consists of 26 bones connected into a flexible, curved structure. The main support of the body axis, the vertebral column extends from the skull to the pelvis, where it transmits the weight of the trunk to the lower limbs. It also surrounds and protects the delicate spinal cord and provides attachment points for the ribs and muscles of the beck and back. In the fetus and infant, the vertebral column consists of 33 separate bones, or vertebrae. Inferiorly, nine of these eventually fuse to form two composite bones, the sacrum and the tiny coccyx (tailbone). The remaining 24 bones persist as individual vertebrae separated by intervertebral discs.

What are the five major regions of the vertebral column (spinal column or spine)?

The vertebral column, also called the spinal column or spine, which is about 70 cm (28 inches) long in an average adult, has five major regions. The 7 vertebrae of the neck are the cervical vertebrae, the next 12 are the thoracic vertebrae, and the 5 that support the lower back are the lumbar vertebrae. Inferior to the lumbar vertebrae is the sacrum, which articulates with the hip bones of the pelvis. The most inferior part of the vertebral column is the tiny coccyx.

xiphisternal joint

The xiphisternal joint is where the sternum body and xiphoid process fuse. It lies at the level of the ninth thoracic vertebra. Deep to this joint, the heart lies on the diaphragm.

xiphoid process

The xiphoid process forms the inferior end of the sternum. This tongue-shaped process is a plate of hyaline cartilage in youth, and it does not fully ossify until about age 40. In some people, the xiphoid process projects posteriorly. Blows to the chest can push such a xiphoid into the underlying heart or liver, causing massive hemorrhage