The Skeletal System: The Appendicular Skeleton

1. The Skeletal System: The Appendicular Skeleton

2. Divisions of the Skeletal System • Axial skeleton—protects and supports the internal organs • Appendicular skeleton—facilitates movement • The appendicular skeleton consists of 126 bones; it includes bones of the limbs and the girdles

3. Pectoral (Shoulder) Girdles • Attach the bones of the upper limbs to the axial skeleton • Each consists of 2 bones: clavicle and scapula

4. Clavicle • Collarbone • An s-shaped bone that articulates with the manubrium of the sternum and with the scapula • One of the most frequently fractured bones of the body

5. Fig. 08.02

6. Scapula • Shoulder blade • A triangular-shaped flat bone that articulates with the clavicle • The acromion is a process of the scapula that can be felt as the high point of the shoulder • The glenoid cavity is a depression of the scapula that articulates with the humerus to form the shoulder joint

7. Upper Limbs • Each upper limb has 30 bones: • Humerus (1) • Radius (1) • Ulna (1) • Carpals (8) • Metacarpals (5) • Phalanges (14)

8. Humerus • Upper arm bone • The longest and largest bone of the upper limb • Articulates proximally with the scapula and distally at the elbow with the radius and ulna of the forearm • The head articulates with the glenoid cavity of the scapula • The capitulum articulates with the head of the radius; the trochlea articulates with the ulna

9. Radius and Ulna • Long bones of the forearm • The ulna is longer than the radius and is located on the “little-finger” side of the forearm • The olecranonof the ulna forms the prominence of the elbow • The radius is located on the thumb side of the forearm • The elbow joint is formed by 2 articulations: • The trochlear notch of the ulna with the trochlea of the humerus • The head of the radius with the capitulum of the humerus

10. Carpals • The wrist consists of 8 small bones called carpals • These bones are arranged in two rows of four bones each • In most carpal fractures, only the scaphoid carpal bone is broken

11. Metacarpals • The palm of the hand consists of 5 long bones called metacarpals • Each of these bones consists of a base, shaft, and head • The metacarpals are numbered 1 through 5, starting with the thumb • The “knuckles” are the heads of the metacarpals

12. Phalanges • The long bones of the fingers (digits) • There are 14 phalanges in each hand • Each phalanx consists of a base, shaft, and head • There are 2 phalanges in the thumb, or pollex, and 3 phalanges in each of the other four digits

13. Pelvic (Hip) Girdles • Consist of 2 hip bones, called coxal bones • These 2 bones unite anteriorly at a joint called the pubic symphysis and posteriorly with the sacrum at the sacroiliac joints • The 2 coxal bones and the sacrum form the pelvis; the pelvis supports the vertebral column and pelvic organs and attaches the lower limbs to the axial skeleton • In an adult, each coxal bone consists of three bones that fused together after birth: • Ilium • Ischium • Pubis

14. Pelvic (Hip) Girdles (continued) • The ilium is the largest and most superior of the three hip bone components; it articulates with the sacrum to form the sacroiliac joint • The ischium is located inferior and posterior; the pubis is located inferior and anterior; together, they surround the obturator foramen, the largest foramen of the skeleton • All three of these bones make up the acetabulum, a deep fossa that accepts the round head of the femur • The two coxal bones meet anteriorly at a joint called the pubic symphysis; this joint contains a cartilage disc that gives the joint flexibility • The pelvis of a female is wider and shallower than that of a male to allow for childbirth

15. Lower Limbs • Each lower limb has 30 bones: • Femur (1) • Patella (1) • Tibia (1) • Fibula (1) • Tarsals (7) • Metatarsals (5) • Phalanges (14)

16. Femur • Thigh bone • Longest, heaviest, and strongest bone in the body • Its proximal end consists of a head that articulates with the hip bone at the acetabulum; its distal end articulates with the tibia and patella

17. Patella • Kneecap • A small, triangular bone located anterior to the knee joint • It is a sesamoid bone, which develops in the tendon of the “quadriceps” muscle • Articulates with the femur

18. Tibia and Fibula • The tibia is the shinbone • It is the larger, medial, weight-bearing bone of the lower leg • At is proximal end, the tibia articulates with the femur and fibula; at its distal end, it articulates with the fibula and the talus bone of the ankle • The fibula is the smaller bone of the lower leg • It lies parallel and lateral to the tibia

19. Tarsals • The ankle consists of 7 bones called tarsals • The calcaneus is the largest and strongest tarsal bone; it is located in the posterior heel part of the foot • The talus is the uppermost tarsal bone; it articulates with the fibula and tibia

20. Metatarsals • The main part of the foot consists of 5 long bones called metatarsals • Each of these bones consists of a base, shaft, and head • The metatarsals are numbered 1 through 5, from the medial to lateral position

21. Phalanges • The long bones of the toes • There are 14 phalanges on each foot • Each phalanx consists of a base, shaft, and head • There are 2 phalanges in the big toe, or hallux, and 3 phalanges in each of the other four digits