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.
