Joints Articulations of bones Functions of joints
Hold bones together Allow for mobility
Various kinds of joints. Fibrous: A, syndesmosis (tibiofibular); B, suture (skull). Cartilaginous: C, symphysis (vertebral bodies); D, synchondrosis (first rib and sternum). Synovial: E, condyloid (wrist); F, gliding (radioulnar); G, hinge or ginglymus (elbow); H, ball and socket (hip); I, saddle (carpometacarpal of thumb); J, pivot (atlantoaxial). Classification of Joints
Functional Structural
Synarthroses Fibrous joints
Immovable joints Generally immovable Amphiarthroses Cartilaginous joints
Slightly moveable Immovable or slightly joints moveable Diarthroses Synovial joints
Freely moveable joints Freely moveable Fibrous Joints: Synarthrosis
Syndesmoses Bones joined by fibrous bands (ligaments) Allows more movement than sutures Bones united by fibrous Example: Distal end of tissue tibia/fibula; radius/ ulna Bones fit tightly together Gomphosis Example: Fibrous tissue between tooth root and alveolar Sutures process of mandible or maxilla Teethlike projections of 2 bones interlock with thin No movement layer of fibrous tissue between them No movement Only in skull Cartilaginous Joints
Bones connected by cartilage Example: Synchondrosis Hyaline cartilage between bones Slight movement Examples First rib and sternum Growth plate between epiphysis and diaphysis Symphysis Pad of fibrocartilage Slight movement Usually located along the midline of the body Pubic symphysis Between bodies of adjacent vertebrae Synovial Joints
Articulating bones are separated by a joint cavity Small spaces between articulating bones that allow for free movement Synovial fluid is found in the joint cavity Features of Synovial Joints
Joint capsule Extension of periosteum of each bone Forms complete casing around ends Synovial membrane lines joint cavity Slippery membrane inside capsule Attaches to margins of articular cartilage Secretes synovial fluid Articular cartilage Hyaline cartilage covers the ends of bones Cushions articular surfaces Features of Synovial Joints
Joint cavity Small spaces between articular surfaces of bones Allows free movement between bones Articular disks: menisci Pads of fibrocartilage between articulating ends of bones in some diarthroses Ligaments reinforce the joint Strong cords of dense, white fibrous tissue Grow between bones, binding together more firmly Structures Associated with the Synovial Joint Bursae Closed, pillow like flattened fibrous sacs Lined with synovial membranes Filled with synovial fluid Function to cushion joint Facilitate moment of tendons Not actually part of the joint Tendon sheath Elongated bursa that wraps around a tendon Types of Synovial Joints
Figure 5.30a–c Types of Synovial Joints
Figure 5.30d–f Types of Synovial Joints
Ends of bones form hinge shaped unit Examples
Elbow: humerus- ulna
Knee: femur- tibia
Fingers: interphalangeal Movement
Uniaxial: only move in one plane
Flexion/ extension Types of Synovial Joints
Projection of one bone articulates with a ring or notch of another bone Examples
Atlas- axis
Head of radius- ulna (proximal end) Movement
Uniaxial: only move in one plane
Rotation Types of Synovial Joints
Saddle Joint Articulating ends resemble reciprocally shaped saddles Example Metacarpal of thumb with carpal (trapezium) Only 2 in body Movement Biaxial: allows movement in two planes Flexion/ extension Abduction/ adduction Opposes thumb to fingers Types of Synovial Joints
Condyloid (Ellipsoidal) Joint Condyle fits into ellipsoidal socket Example Condyles of occipital bone with ellipsoidal sockets of atlas Distal end of radius with depression of carpals Metacarpal with proximal phalange Movement Biaxial: allows movement in two planes Flexion/ extension Abduction/ adduction Types of Synovial Joints Ball and Socket Joint Ball shaped head fits into concave depression of other bone Most movable joints Example Shoulder: humerus- scapula Hip: femur- pelvis Movement Multiaxial: allows movement in all planes Flexion/ extension Abduction/ adduction Circumduction Rotation Types of Synovial Joints
Plane (gliding) joint
Relatively flat articulating surface Examples
Articular surface of successive vertebrae
Carpals
Tarsals Movement
Nonaxial
Gliding without any angular or circular movements Angular Movements
Flexion: decreases Extension: increases angle angle between between bones. Returns bones from flexed position to
Bending anatomical position
Folding Straightening
Withdrawing Stretching Hyperextension: stretching part beyond anatomical position Angular Movements
Abduction: moves Adduction: moves part part away from toward median plane of median plane of body body Angular Movements
Plantarflexion Dorsiflexion
Foot stretched down Foot tilted upward and back Decreases angle Increases angle between top of foot between top of foot and front of leg and front of leg Circular Movements
Rotation Circumduction
Pivoting bone on its Moves part so its distal own axis end moves in a circle Circular Movements
Supination Pronation
Turns palm up Turns palm down Gliding Movements
Articular surface of one bone moves over articular surface of another without angular or circular movement
Between carpal, tarsal bones Between articular facets of spinal vertebrae Special Movements
Inversion: turns sole Eversion: turns sole inward outward Special Movements
Protraction: moves Retraction: moves part forward part backward Special Movements
Elevation: moves part Depression: lowers up part Inflammatory Conditions Associated with Joints Bursitis—inflammation of a bursa usually caused by a blow or friction Tendonitis—inflammation of tendon sheaths Arthritis—inflammatory or degenerative diseases of joints
Over 100 different types The most widespread crippling disease in the United States Clinical Forms of Arthritis
Osteoarthritis
Most common chronic arthritis Probably related to normal aging processes Rheumatoid arthritis An autoimmune disease—the immune system attacks the joints Symptoms begin with bilateral inflammation of certain joints Often leads to deformities Clinical Forms of Arthritis
Gouty arthritis
Inflammation of joints is caused by a deposition of uric acid crystals from the blood Can usually be controlled with diet Developmental Aspects of the Skeletal System At birth, the skull bones are incomplete Bones are joined by fibrous membranes called fontanels Fontanels are completely replaced with bone within two years after birth Ossification Centers in a 12-week- old Fetus
Figure 5.32 Skeletal Changes Throughout Life
Fetus
Long bones are formed of hyaline cartilage Flat bones begin as fibrous membranes Flat and long bone models are converted to bone Birth
Fontanels remain until around age 2 Skeletal Changes Throughout Life
Adolescence
Epiphyseal plates become ossified and long bone growth ends Size of cranium in relationship to body 2 years old—skull is larger in proportion to the body compared to that of an adult 8 or 9 years old—skull is near adult size and proportion Between ages 6 and 11, the face grows out from the skull Skeletal Changes Throughout Life
Figure 5.33a Skeletal Changes Throughout Life
Figure 5.33b Skeletal Changes Throughout Life
Curvatures of the spine
Primary curvatures are present at birth and are convex posteriorly Secondary curvatures are associated with a child’s later development and are convex anteriorly Abnormal spinal curvatures (scoliosis and lordosis) are often congenital Skeletal Changes Throughout Life
Figure 5.16 Skeletal Changes Throughout Life
Osteoporosis Bone-thinning disease afflicting 50% of women over age 65 20% of men over age 70 Disease makes bones fragile and bones can easily fracture Vertebral collapse results in kyphosis (also known as dowager’s hump) Estrogen aids in health and normal density of a female skeleton Skeletal Changes Throughout Life
Figure 5.34 Skeletal Changes Throughout Life
Figure 5.35