Anatomy Chp. 8

The Upper Limb

30 bones form each upper limb Grouped into bones of the: Arm, Forearm, Hand

Carpal bones

Are arranged in two irregular rows Proximal row from lateral to medial: Scaphoid, lunate, triquetral, and pisiform Distal row from lateral to medial: Trapezium, trapezoid, capitate, and hamate A mnemonic to help remember carpals: "Sally left the party to take Carmen home"

Upper/lower body ratio changes with age

At birth, head and trunk are 1.5 times as long as lower limbs Lower limbs grow faster than the trunk Upper/lower body ratio of 1 to 1 by age 10

Pelvic Girdle

Attaches lower limbs to the spine Supports visceral organs Attaches to the axial skeleton by strong ligaments Acetabulum

Disorders of the Appendicular Skeleton

Bone fractures Hip dysplasia: Head of the femur slips out of acetabulum Clubfoot: Soles of the feet turn medially Osteonecrosis

Autograft

Bone from the same person is typically harvested from intra-oral sources as the chin or extra-oral sources as the iliac crest, the fibula, the ribs, the mandible and even parts of the skull. (fibula bears minimal weight. Its primary purpose is to act as a strut for muscle attachment)

Hand

Carpus—wrist Metacarpals—palm Phalanges—fingers

The Lower Limb

Carries the entire weight of the erect body Bones of lower limb are thicker and stronger than those of upper limb Divided into three segments: Thigh, leg, and foot

Metatarsus

Consists of five small long bones called metatarsals Numbered I-V beginning with the hallux (great toe) First metatarsal supports body weight They form the sole of the foot

The Pectoral Girdle

Consists of the clavicle and the scapula Pectoral girdles do not quite encircle the body completely Mobility: Only clavicle articulates with the axial skeleton (Scapula can move freely) Socket of the shoulder joint (glenoid cavity) is shallow: Good for flexibility, bad for stability

Clavicles

Extend horizontally across the superior thorax Sternal end articulates with the manubrium Acromial end articulates with scapula

Major differences between male and female pelves

Female pelvis is adapted for childbearing Pelvis is lighter, wider, and shallower than in the male Provides more room in the true pelvis

Stabilizes the ankle joint

Fibula does not contribute to the knee joint

Metacarpus

Five metacarpals radiate distally from the wrist Form the palm: Numbered I-V, beginning with the pollex (thumb), Bases articulate proximally with the distal row of carpals, and Heads articulate distally with the proximal phalanges

The Foot

Foot is composed of: Tarsus, metatarsus, and the phalanges Important functions: Supports body weight, Acts as a lever to propel body forward when walking, Segmentation makes foot pliable and adapted to uneven ground

Forearm

Formed from the radius and ulna Proximal ends articulate with the humerus Distal ends articulate with carpals

Carpus

Forms the true wrist (The proximal region of the hand) Gliding movements occur between carpals Composed of eight marble-sized bones Carpal bones

Major landmarks of the radius:

Head Neck Radial tuberosity Radial styloid process

Sesamoids on the toe

In the foot - the first metatarsal bone usually has two sesamoid bones at its connection to the big toe (both within the tendon of flexor hallucis brevis). In some people, only a single sesamoid is developed.

Growth of the appendicular skeleton

Increases height Changes body proportions

Interosseous membrane

Interconnects radius and ulna Connects the tibia and fibula

Arches are maintained by

Interlocking shapes of tarsals Ligaments and tendons "Keystone" bones of arches Talus—medial longitudinal arch Cuboid—lateral longitudinal arch

Pisiform

Is a sesamoid bone (within the tendon of flexor carpi ulnaris). It is not present at birth and generally develops in children ages 9-12

Scapulae

Lie on the dorsal surface of the rib cage Located between ribs 2-7 Have three borders: Superior, Medial (vertebral), Lateral (axillary) Have three angles: Lateral, superior, and inferior

Ulna

Main bone responsible for forming the elbow joint with the humerus Hinge joint allows forearm to bend on arm Distal end is separated from carpals by fibrocartilage Plays little to no role in hand movement

Tarsus

Makes up the posterior half of the foot Contains seven bones called tarsals Body weight is borne primarily by the talus (ankle) and calcaneus (heel) Trochlea of the talus Other tarsals: Cuboid and navicular

Pectoral girdles

Medial end of each clavicle articulates with the manubrium and first rib Laterally—the ends of the clavicles join the scapulae Scapulae do not join each other or the axial skeleton

Foot has three important arches

Medial longitudinal arch and lateral longitudinal arch Transverse arch

Phalanges

Numbered I-V, beginning with the pollex (thumb) Except for the thumb, each finger has three phalanges (Proximal, middle, and distal)

Major landmarks of the ulna

Olecranon Radial notch Trochlear notch Coronoid process Ulnar styloid process

The Appendicular Skeleton

Pectoral girdle (Attaches the upper limbs to the trunk) Pelvic girdle (Attaches the lower limbs to the trunk) Upper and lower limbs differ in function (Share the same structural plan)

Forearm

Radius and ulna articulate with each other At the proximal and distal radioulnar joints The interosseous membrane In anatomical position; the radius is lateral and the ulna is medial

Leg

Refers to the region of the lower limb between the knee and the ankle Composed of the tibia and fibula Interosseous membrane

Arm

Region of the upper limb between the shoulder and elbow Humerus

Trochlea of the talus

Site of articulation with the tibia

Few changes occur in adult skeleton until middle age, when

Skeleton loses mass Osteoporosis and limb fractures become more common

14 phalanges of the toes

Smaller and less nimble than those of the fingers Structure and arrangement are similar to phalanges of fingers Each toe has proximal, middle, and distal phalanges (Exception: great toe has only two phalanges, proximal and distal) The great toe is the hallux (hal′ŭks; hallex = great toe), and it has only two phalanges (proximal and distal); each of the other four toes has three phalanges (

Radius

Superior surface of the head of the radius articulates with the capitulum Medially—the head of the radius articulates with the radial notch of the ulna Contributes heavily to the wrist joint: Distal radius articulates with carpal bones and When radius moves, the hand moves with it

Humerus

The only bone of the arm Longest and strongest bone of the upper limb Articulates with the scapula at the shoulder Articulates with the radius and ulna at the elbow

Thigh

The region of the lower limb between the hip and the knee Femur

Femur

The single bone of the thigh Longest and strongest bone of the body Ball-shaped head of the femur articulates with the acetabulum

Forms the knee joint

Tibia articulates with femur at superior end

Forms the ankle joint

Tibia articulates with talus at the inferior end

Patella

Triangular sesamoid bone Embedded in the tendon that secures the quadriceps muscles Protects the knee anteriorly Improves leverage of the thigh muscles across the knee

Sesamoid bone

a bone formed after birth in a tendon where it passes over a joint, for example, the patella

Osteonecrosis

bone dies after losing its blood supply. Every year, between 10,000 to 20,000 Americans develop osteonecrosis; most are between the ages of 20 and 50 years, and most are men.

Acetabulum

is a deep cup that holds the head of the femur (Lower limbs have less freedom of movement and Are more stable than the arm) Consists of paired hip bones (coxal bones or pelvic bone) and the sacrum Coxal bones unite anteriorly with each other and articulate posteriorly with the sacrum

Tibia

more massive medial bone of the leg Receives weight of the body from the femur

Fibula

sticklike lateral bone of the leg. Does not bear or transfer weight, its distal tip, called the lateral malleolus, extends laterally to the ankle joint, where it provides lateral stability

capitulum

(caput = head) is located laterally and articulates with the head of the radius.