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 Joints are articulations : ◦ where two or more bones meet  Functions: ◦ Hold bones together ◦ Allow for mobility © 2015 Pearson Education, Inc.

 Fibrous joints: = Generally immovable; joint by fibrous tissue ◦ Ex: sutures  Cartilaginous joints: = Immovable or slightly movable; joint by fibrocartilage ◦ Ex: intervertebral joints, pubic symphysis  Synovial joints: = Freely movable; joint by hyaline cartilage and presence of cavity w/ synovial fluid © 2015 Pearson Education, Inc.

 Four distinguishing features of synovial joints 1.Articular cartilage 2.Articular capsule 3.Joint cavity 4.Reinforcing ligaments © 2015 Pearson Education, Inc.

Figure 5.30f Types of joints. (f) Multiaxial joint Humerus Articular (hyaline) cartilage (shoulder joint) Scapula Articular capsule Synovial joints

Figure 5.30g Types of joints. (g) Uniaxial joint Ulna Radius Articular capsule Articular (hyaline) cartilage Humerus (elbow joint) Synovial joints

Figure 5.30h Types of joints. Synovial joints (h) Biaxial joint (intercarpal joints of hand) Carpals Ulna Radius Articular capsule

Bursae—flattened fibrous sacs – Lined with synovial membranes – Filled with synovial fluid Tendon sheath – Elongated bursa that wraps around a tendon The cells of these structures secrete synovial fluid that lubricates the joint © 2015 Pearson Education, Inc.

 Types of synovial joints based on shape: ◦ Plane joint- gliding movements (wrist) ◦ Hinge joint- elbow, ankle, knee ◦ Pivot joint- C1/C2, proximal radius and ulna ◦ Condylar joint- metacarpals to phalanges ◦ Saddle joint- metacarpals to carpal at pollex ◦ Ball-and-socket joint- shoulder, hip © 2015 Pearson Education, Inc.

 Bursitis—inflammation of a bursa  Tendonitis—inflammation of tendon sheaths  Arthritis—inflammatory or degenerative diseases of joints ◦ The most widespread crippling disease in the United States © 2015 Pearson Education, Inc.

 Osteoarthritis (OA) ◦ Most common; related to normal aging processes ◦ Due to wear/tear, bone spurs  Rheumatoid arthritis (RA) ◦ autoimmune disease—the immune system attacks the joints  Unknown cause; pathogenic cause probable © 2015 Pearson Education, Inc.

 Fetal skeleton ◦ hyaline cartilage and fibrous membranes  Cranium size vs. body ◦ 2 years old—skull is larger in proportion to body ◦ 8 or 9 years old—skull near adult size ◦ cranium growth after birth relates to brain growth  Adolescence ◦ Epiphyseal plates ossify; long bone growth ends © 2015 Pearson Education, Inc.

Figure 5.34 Ossification centers in the skeleton of a 12-week-old fetus are indicated by the darker areas. Lighter regions are still fibrous or cartilaginous. Frontal bone of skull Parietal bone Occipital bone Clavicle Scapula Mandible Radius Ulna Humerus Femur Tibia Ribs Vertebra Hip bone

Figure 5.35a Differences in the growth rates for some parts of the body compared to others determine body proportions. Human newborn Human adult (a)

Figure 5.35b Differences in the growth rates for some parts of the body compared to others determine body proportions. (b) Newborn2 yrs.5 yrs. 15 yrs.Adult