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

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 olecranon of 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