Essentials of Anatomy and Physiology

128 The Skeletal System

Table 6–4 BONES OF THE HIP AND LEG—IMPORTANT PARTS

Bone Part Description

Pelvic (2 hip bones)

Femur

Tibia

Fibula

Tarsals (7)

• Ilium


• Iliac crest


• Posterior superior iliac spine


• Ischium


• Pubis


• Pubic symphysis


• Acetabulum


• Head


• Neck


• Greater trochanter


• Lesser trochanter


• Condyles


• Condyles


• Tibial tuberosity


• Anterior crest


• Medial malleolus


• Head


• Lateral malleolus


• Calcaneus


• Talus


• Cuboid, navicular


• Cuneiform: 1st, 2nd, 3rd
  
  
  • Flared, upper portion
  
  
  • Upper edge of ilium
  
  
  • Posterior continuation of iliac crest
  
  
  • Lower, posterior portion
  
  
  • Anterior, medial portion
  
  
  • Joint between the 2 pubic bones
  
  
  • Deep depression that articulates with femur
  
  
  • Round process that articulates with hip bone
  
  
  • Constricted portion distal to head
  
  
  • Large lateral process for muscle attachment
  
  
  • Medial process for muscle attachment
  
  
  • Rounded processes that articulate with tibia
  
  
  • Articulate with the femur
  
  
  • Round process for the patellar ligament
  
  
  • Vertical ridge
  
  
  • Distal process; medial “ankle bone”
  
  
  • Articulates with tibia
  
  
  • Distal process; lateral “ankle bone”
  
  
  • Heel bone
  
  
  • Articulates with calcaneus and tibia
    —
    —
  
  
  
  

JOINTS—ARTICULATIONS

A joint is where two bones meet, or articulate.

THE CLASSIFICATION OF JOINTS

The classification of joints is based on the amount
of movement possible. A synarthrosis is an immovable
joint, such as a suture between two cranial bones.
An amphiarthrosis is a slightly movable joint, such
as the symphysis joint between adjacent vertebrae. A
diarthrosis is a freely movable joint. This is the largest
category of joints and includes the ball-and-socket
joint, the pivot, hinge, and others. Examples of each
type of joint are described in Table 6–5, and many of
these are illustrated in Fig. 6–15.

SYNOVIAL JOINTS

All diarthroses, or freely movable joints, are synovial
joints because they share similarities of structure. A
typical synovial joint is shown in Fig. 6–16. On the
joint surface of each bone is the articular cartilage,
which provides a smooth surface. The joint capsule,
made of fibrous connective tissue, encloses the joint in

a strong sheath, like a sleeve. Lining the joint capsule

is the synovial membrane, which secretes synovial

fluid into the joint cavity. Synovial fluid is thick and

slippery and prevents friction as the bones move.

Many synovial joints also have bursae(or bursas),

which are small sacs of synovial fluid between the joint

and the tendons that cross over the joint. Bursae per-

mit the tendons to slide easily as the bones are moved.

If a joint is used excessively, the bursae may become

inflamed and painful; this condition is called bursitis.

Some other disorders of joints are described in Box

6–5: Arthritis.

AGING AND THE SKELETAL SYSTEM

With age, bone tissue tends to lose more calcium than

is replaced. Bone matrix becomes thinner, the bones

themselves more brittle, and fractures are more likely

to occur with mild trauma.

Erosion of the articular cartilages of joints is also a

common consequence of aging. Joints affected include

weight-bearing joints such as the knees, and active,

small joints such as those of the fingers.

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