Anatomy ch. 8

The APPENDICULAR SKELETON...

-the bones of the upper and lower limbs and the pectoral and pelvic girdles that attach them to the actual skeleton.

Abnormalities occur in every...

2 out of 1,000 live births.

The _____is a slender lateral strut...

FIBULA; that helps to stabilize the ankle. It does not bear any of the body's weight (it is actually used to replace other bones). Somewhat thicker and broader at its proximal end, the HEAD. The point of the head is called the APEX. The fibula is joined to the tibia by a ligament called the INTEROSSEOUS MEMBRANE.

Syndactyly

Fusion of digits(webbed) Cutaneous syndactyly is the presence of a skin web between the digits. Osseous syndactyly is fusion of the bones of the digits (failure of notches to form between the embryonic digital rays) Usually hereditary but can be induced by teratogens.

The ________has a hemispherical...

HUMERUS; HEAD that articulates with the glenoid cavity of the scapula. The smooth surface of the head (covered with articular cartilage in life) is bordered by a groove called the ANATOMICAL NECK. Other prominent features of the proximal end are muscle attachments called the GREATER and LESSER TUBERCLES and an INTERTUBERCULAR SULCUS(groove) between them that accommodates a tendon of the biceps muscle. The SURGICAL NECK, a common fracture site, is a narrowing of the bone just distal to the tubercles, at the transition from the head to the shaft. The shaft has a rough area called the DELTOID TUBEROSITY on its lateral surface. The distal end is the humerus has two smooth condyles. The lateral one, called the CAPITULUM(us shaped like a flat wheel and articulates with the radius. The medial one called the TROCHLEA(is pulley like and articulates with the ulna. Immediately proximal to these condyles, the humerus the humerus flares out to form two bony processes, the LATERAL and MEDIAL EPICONDYLES. ( the medial condyle protects the ulnar nerve, which passes close to the surface across the back of the elbow. Medial epicondyle is popularly known as the "funny bone " bc a sharp blow to the elbow at this point stimulates the ulna nerve and produces an intense tingling sensation. Immediately proximal to the epicondyles, the margins of the humerus are sharply angular and form the LATERAL and MEDIAL SUPRACONDYLAR RIDGES. (These are attachments for certain forearm muscles) The distal end of the humerus also shows three deep pits- two anterior and one posterior. The posterior pit called the OLECRANON FOSSA(accommodates a process of the ulna called the olecranon when the elbow is extended. On the anterior surface, a medial pit called the CORONOID FOSSA accommodates the coronoid process of the ulna when the elbow is flexed. The lateral pit is the RADIUL FOSSA(named for the nearby head of the radius)

The _______is only weight bearing bone...

TIBIA; of the crural region. It has two fairly flat articular surfaces, the MEDIAL and LATERAL CONDYLES, separated by a ridge called the INTERCONDYLAR EMINENCE. These condyles articulate with those of the femur. The TIBIAL TUBEROSITY can be palpated just below the patella. Distal to this, the shaft has a sharply angular ANTERIOR BORDER (felt in the shin region) At the ankle you can palpate a prominent bony knob on each side. These are the MEDIAL and LATERAL MALLEOLI(the medial malleolus is on the tibia and the lateral malleoli is on the fibula.

With few exceptions, the bones of the limbs and their girdle's arise by...

endochondral ossification. Exceptions include the clavicle, which forms primarily by intramembranous ossification and sesamoid bones.

Meromelia

partial absence of a limb. Typically absence of long bones, with rudimentary hands and feet attached to the trunk directly.

The carpal bones are...

still cartilaginous at birth.

The _________extends from elbow...

to wrist on the lateral side of the forearm, ending just proximal to the base of the thumb. It has a distinctive discoidal HEAD at its proximal end. Immediately distal to the head, the radius has a narrower NECK and then widened to a rough prominence, the RADIAL TUBEROSITY, on its medial surface. The distal end of the radius has the following features, from lateral to medial. 1. A bony point the STYLOID PROCESS, can be 2. Two shallow depressions (articular facets, articulates with the scaphoid and lunate bones of the wrist) 3. The ULNAR NOTCH articulates with the end of the ulna.

The pelvis is the most ...

SEXUALLY DIMIRPHIC part of the skeleton-that is , the one whose anatomy most differs between the sexes. Forensics focus most heavily on the pelvis to identity skeletal remains. Females pelvis is wider and shallower , for childbirth.

The______, which essentially extends from heel to...

MEDIAL LONGITUDINAL ARCH; hallux, and is formed from the calcaneus, talus, navicular, cuneiforms, and metatarsals I through III (normally well above the ground, as evidenced by a wet footprint) The LATERAL LONGITUDINAL ARCH extends from heel to little toe and includes the calcaneus, cuboid, and metatarsals IV and V. The TRANSVERSE ARCH includes the cuboid, cuneiforms , and proximal heads of the metatarsals. These arches are held together by short, strong ligaments. Excessive weight or stress can cause weakness of these ligaments-resulting in PES PLANUS (flat feet)

Bones of the palm are called...

METACARPALS. Metacarpal I is located proximal to the thumb and metacarpal V is proximal to the little finger. The proximal end of a metacarpal bone is called the BASE, the shaft is called the BODY, and the distal end is called the HEAD. (the heads of the metacarpals form the knuckles when you clench your fist)

The _______, is a roughly triangular...

PATELLA; sesamoid bone embedded in the tendon of the knee. It is cartilaginous at birth and ossifies at 3-6. It has a broad superior BASE, a pointed inferior APEX, and a pair of shallow ARTICULAR FACETS in its posterior surface where it articulates with the femur. The lateral facet is usually larger than the medial.

The _________supports the arm and links it to the axial skeleton....

PECTORAL GIRDLE(shoulder girdle); It consists of two bones on each side of the body: the CLAVICLE(collarbone) and SCAPULA(shoulder blade).

The_______is the medial bone of the...

ULNA; forearm. Its proximal end has a wrench like shape, with a deep, C shaped TROCHLEAR NOTCH that wraps around the trochlea of the humerus. The posterior side of this bitch is formed by a OLECRANON(the bony part where you rest your elbow on a table). The anterior side is formed by a less prominent CORONOID PROCESS. Laterally the head of the ulna has a less conspicuous RADIAL NOTCH(which accommodates the edge of the head of the radius). At the distal end of the ulna is a medial STYLOID PROCESS. The radius and ulna are attached along their shafts by a ligament called the INTEROSSEOUS MEMBRANE(which is attached to an angular ridge called the INTEROSSEOUS BORDER on the facing margins of each bone.) most fibers are oriented obliquely, slanting upward from the ulna to the radius) If you lean forward on a table with your hands 80% of the force is borne by the radius. This tense the IM which pulls the upward and transfers some of this force through the ulna to the humerus. The IM also serves as an attachment for several forearm muscles.

The clavicles...

brace the shoulders, keeping the upper limbs away from the midline of the body. It is thickened in people who do manual labor, and is stronger and shorter on a persons dominant side.

The median end of the _______articulates with the sternum at the .....

clavicle; STERNOCLAVICULAR JOINT and its lateral end articulates with the scapula at the ACROMIOCLAVICULAR JOINT. The scapula also articulates with the humerus at the GLENOHUNERAL (shoulder) JOINT. (these are loose attachments that result in a shoulder far more flexible than that of most other mammals, but also make the shoulder joint easy to dislocate)

Amelia

congenital absence of one or more limbs

We will follow the practice of Grays Anatomy in...

considering the PELVIC GIRDLE to consist of a complete ring composed of three bones-two HIP(coxal) BONES and the sacrum (which is of course apart of the vertebral column). The hip bones are frequently called the OSSA COXAE and sometimes INNOMINATE bones (the bones with no name). The PELVIS is a bowl-shaped structure composed of these bones as well as their ligaments and the muscles that line the pelvic cavity and form its floor. The pelvic girdle supports the trunk on the lower limbs and encloses and protects the viscera of the pelvic cavity(lower colon, urinary bladder, and internal reproductive organs.) Each hip bone is joined to the vertebral column at one point, the SACROILIAC (SI) JOINT, where its AURICULAR SURFACE matches the aricular surface of the sacrum. The two hip bones articulate with each other on the anterior side of the pelvis, where they are joined by a pad of fibrocartilage called the INTERPUBIC DISC. The interpubic disc and the adjacent region of pubic bone on each side constitute the PUBIC SYMPHYSIS Pelvis is bowl-shaped with the broad GREATER (false) PELVIS {forms the walls of the lower abdominal cavity} between the flare of the hips and the narrow LESSER(true) PELVIS {encloses the pelvic cavity} below. The two are separated by a somewhat round margin called the PELVIC BRIM. The opening circumscribed by the brim is called the PELVIC INLET (an entry into the lesser pelvis through which an infants head passes during birth. The lower margin of the lesser pelvis is called the PELVIC OUTLET The hip bones have three distinctive features that will serve as landmarks: 1. ILIAC CREST (superior crest of the hip) 2. ACETABULUM(the hip socket-resemblance to vinegar cups in Roman dining tables) 3. OBTURATOR FORAMEN (large round to triangular hole below the acetabulum{closed in life by a ligament called the obturator membrane}. The adult hip bone forms by the fusion of three childhood bones called the ILIUM, ISCHIUM and the PUBIS

The lower limb is...

divided into four regions containing a total of 30 bones per limb: 1. The FEMORAL REGION, our thigh, exerts from hip to knees and contains the FEMUR, the PLATELLA(knee cap) is a sesamoid bone at the junction of the femoral and crural regions. 2. The CRURAL REGION, or leg proper, extends from knee to ankle and contains two bones, the medial TIBIA and lateral FIBULA 3. The TARSAL REGION(TARSUS) , or angle, is the union of the crural region with the foot. The tartan bones are treated as part of the foot. 4. The PEDAL REGION (PES), or foot, is composed of 7 TARSAL BONES, 5 METATARSAL BONES, and 14! PHALANGES in the toes.

Polydactyly

extra fingers or toes

club foot (talipes equinovarus)

fixed foot in inversion with no flexibility no ankle dorsiflexion M>F, pacific islanders associated with DDH, myelomeningocele, myotonic dystrophy, some skeletal dysplasias tx: casting within 1st week of life. may need surgery if no improvement after 3mo or severe goodprognosis Soles turned medially. Relatively common. Cause is unknown.

Evolutionary changes in the...

pelvis and associated muscles account for the smooth, efficient stride of a human in comparison to a gorillas awkward shuffling when standing bipedal.

A complete cartilaginous limb skeleton is...

present by week 6.

The leg has...

two bones-a thick strong tibia on the medial side and a slender fibula on the lateral side.

The_________are arranged in two rows of....

CARPAL BONES; four bones each. Although they are commonly called the wrist bones, they are located in the base of the hand. The narrow point where one might where a watch or bracelet is at the distal ends of the radius and ulna The short carpal bones allow movements of the wrist from side to side and anterior to posterior. The carpal bones of the proximal row, starting at the lateral (thumb) side, are the SCAPHOID(boat), LUNATE(moon), TRIQUERTRUM(triangle), and PISIFORM(peashaped). Unlike the other carpal bones, the pisiform is sesamoid bone; it is not present at birth but develops around the age of 9-12 years within the tendon of the FLEXOR CARPI ULNARIS MUSCLE. The bones of the distal row , again starting on the lateral side, are the TRAPEZIUM, TRAPEZOID, CAPITATE, HAMATE(the hamster can be recognized by a prominent hook, or HAMULUS, on the palmar side. It is an attachment for the FLEXOR NACULUM, a fibrous sheet in the wrist that covers the carpal bone.

The _______is a slightly S-shaped bone...

CLAVICLE: somewhat flattened from the upper to lower surface. The medial STERNAL END has a rounded, hammer-like head, and the lateral ACROMIAL END is markedly flattened. Near the acromial end is a rough tuberosity called the CONOID TUBERCLE(a ligament attachment)

The ________is the longest and strongest bone of the body...

FEMUR; has a hemispherical head that articulates with the acetabulum of the pelvis, forming a quintessential BALL-AND-SOCKET JOINT. A ligament extends from the acetabulum to a pit, the FOVEA CAPITIS(in the head of the femur). Distal to the head is the constricted NECK, a common site of femoral fractures. Just beyond the neck are two massive, rough processes called the GREATER and LESSER TROCHANTERS(which are insertions for the powerful muscles of the hip). The trochanters are connected on the posterior side by a thick oblique ridge of bone, the INTERTROCHANTERIC CREST, and on the anterior side by a more delicate INTERTROCHANTERIC LINE. The primary feature of the shaft is a posterior ridge called the LINEA ASPERA. At its upper end, the linea aspera fork's into a medial SPIRAL LINE and a lateral GLUTEAL TUBEROSITY(a rough ridge {sometimes depression} that serves attachment of the gluteus maximus muscle. At its lower end, the linea aspea forks into MEDIAL and LATERAL SUPRACONDYLAR LINES, which continue down to the respective epicondyles. The distal end of the femur flares into MEDIAL and LATERAL EPICONDYLES, the widest points of the femur at the knee. Distal to these are two smooth round surfaces of the knee joint, the MEDIAL and LATERAL CONDYLES, separated by a groove called the INTERCONDYLAR FOSSA. (during knee flexion and extension, the condyles rock on the superior surface of the tibia. On the anterior side of the femur, a smooth medial depression called the PATELLAR SURFACE articulates with the patella. On the posterior side is a flat or slightly depressed area called the POPLITEAL SURFACE. We lock our knees when standing, allowing us to maintain an erect posture with little muscular effort. Femurs are angled medially.

The bones of the fingers are called...

PHALANGES; in the singular phalanx. There are two phalanges in the phalanges in the POLLEX(thumb) and three in each of the other digits. Phalanges are identified by Roman numerals preceded by PROXIMAL, MIDDLE and DISTAL. (e. g. proximal phalanx I is in the basal segment of the thumb; the left proximal phalanx IV is where people where wedding rings) The three parts of a phalanx are the same as the metacarpal: BASE, BODY, HEAD.

The _______is a triangular...

SCAPULA; plate that overlies ribs 2-7. It's only direct attachment to the thoracic cage is by muscles, it glides over the rib cage as the arm and shoulder move. The three sides of the scapular triangle are called the SUPERIOR, MEDIAL (vertebral), and LATERAL(axillary) BORDERS It's three angles are the SUPERIOR, INFERIOR, and LATERAL ANGLES. SUPRASCAPULAR NOTCH in the superior border provides passage for the nerve. Broad anterior surface is called the SUBSCAPULAR FOSSA. (slightly concave and relatively featureless) The posterior surface has a transverse shelf-like ridge called the SPINE, a deep indentation superior to the spine called the SUPRASINOUS FOSSA and a broad surface inferior to it called the INFRASPINOUS FOSSA. The lateral angle has three main features. The ACROMION-plate like extension of the scapular spine that forms the apex of the shoulder. It articulates with the clavicle, which forms the sole bridge from the appendicular to the axial skeleton The CORACOID PROCESS-is shaped like a bent finger but named for a vague resemblance to a crows beak; it provides attachment for tensions of the BICEP BRACHII and other muscles of the arm. The GLENOID CAVITY is a shallow socket that articulates with the head of the humerus, forming the glenohuneral joint.

The _______of the ankle are arranged in proximal and distal...

TARSAL BONES; groups somewhat like the carpal bones of the wrist. The largest tarsal bone is the CALCANEUS(which forms the heel). Its posterior end is the point of attachment for the CALCANEAL(ACHILLES) TENDON from the calf muscles. The second-largest tarsal bone, and the most superior, is the TALUS(it has three articular surfaces; inferiorposterior one that articulates with calcaneus, a superior TROCHLEAR SURFACE that articulates with the tibia, and an anterior surface that articulates with a short, wide tarsal bone called the NAVICULAR. The talus, calcaneus, and navicular are considered the proximal row of tarsal bones. The distal group forms a row of four bones. Proceeding from medial side to lateral, these are the MEDIAL, INTERMEDIATE, and LATERAL CUNEIFORMS and the cuboid. (the cuboid is the largest). The proximal METATARSALS are similar to the metacarpals. They are METATARTALS I through V from medial to lateral (metatartals I through III articulate with the three cuneiforms; metatarsals IV and V articulate with the cuboid. The bones of the toe, like the fingers are called phalanges. The great toe is the HALLUX and contains only two bones, the proximal and distal phalanx I. The other toes each contain a proximal, middle, and distal phalanx. The metatarsals and phalanges each have a base, body and head.

Curious how the largest digits are lateral in the hand and medial in the foot, and that the elbows and knees flex in opposite directions, this is result from...

a rotation of the limbs that occurs in week 7. Limbs extend anteriorly early that week 7. The future thumb and toe are both directed superiorly, and the future palms and soles face each other medially. Then the limbs rotate about 90degrees in opposite directions. Initially hands and feet faced each other, then Palms Up-Soles Down the

The human forelimbs are...

adapted primarily for reaching out, exploring the environment, and manipulating objects. They are shorter than the hindlimbs and far less muscular than the forelimbs of apes. Although the forelimbs have the same basic bone and muscle pattern as the hindlimbs, the joints of the shoulders and hands, especially, give the forelimbs far greater mobility.

The adult hip bone forms by the...

fusion of three childhood bones called the ILIUM, ISCHIUM and PUBIS. The ILIUM is the largest which extends from the iliac crest to the center of the acetabulum. The iliac crest extends from an anterior point or angle called the ANTERIOR SUPERIOR ILIAC SPINE to a sharp posterior angle called the POSTERIOR SUPERIOR ILIAC SPINE. Below the superior spines are the ANTERIOR and POSTERIOR INTERIOR ILIAC SPINES. Below those is a deep GREATER SCIATIC NOTCH(named for the sciatic nerve that passes through it and continues down the posterior side of the thigh) The anteromedial surface is the smooth, slightly concave ILIAC FOSSA (covered in life by the iliacus muscle). Medially the ilium exhibits an aricular surface that matches the one on the sacrum, so the two bones form the sacroiliac joint. The ISCHIUM forms the inferoposterior portion of the hip bone. It's heavy body is marked with a prominent SPINE. Inferior to the spine is a slight indentation, the LESSER SCIATIC NOTCH and then the thick, rough-surfaced ISCHIAL TUBEROSITY (which supports your body when you're sitting) The RAMUS of the ischium joins the inferior ramus of the pubis anteriorly. The PUBIS(PUBIC BONE) is the most anterior portion of the hip bone; it is nearly horizontal. It has a SUPERIOR and INFERIOR RAMUS and a triangular BODY.

The first sign of limb development is the appearance of...

upper LIMB BUDS around day 26 to 27 and lower limb buds 1-2 days later. Limbs buds consist of a core of mesenchyme covered with ectoderm, and elongate as mesenchyme proliferates. The distal end of the limb buds flatten into paddle-like HAND and FOOT PLATES. By day 38 in the hand and day 44 in the foot, these plates show parallel ridge called DIGITAL RAYS(future fingers and toes). Mesenchyme between digital rays break down by week 8

The _______is divided into three segments containing a total of...

upper limb; 30 bones per limb. 1.The BRACHIUM, or proper arm, extends from shoulder to elbow. It contains only one bone the humerus 2.The ANTEBRACIUM, or forearm, extends from elbow to wrist and contains two bones- the radius and ulna. In anatomical position these bones are parallel and the radius is lateral to the ulna. 3.The MANUS, or hand, contains 27 bones in three groups-8 carpal bones in the base of the hand, 5 metacarpals in the palm, 14 phalanges in three digits.