Joints and Movement

Articulations = Joints Functional junctions between bones Bind parts of the skeletal system Make bone growth possible Permit skeletal change during childbirth Enable movement in response to muscle contraction Skeleton Review Video

3 Types of Cartilage

Classification of Joints Classification based on the type of tissue that binds the bones: Fibrous joints Cartilaginous joints Synovial joints Classification according to degree of movement possible: Immovable (synarthrotic) Slightly movable (amphiarthrotic) Freely movable (diarthrotic)

Fibrous Joints Dense CT with many collagenous fibers Lie between bones that are in close contact 3 types: Syndesmosis – bones bound by long fibers of CT (interosseous ligament); may be twisted amphiarthrotic Suture – only between flat bones of the skull Synarthrotic Gomphosis – joint between tooth and socket; periodontal ligament

Fibrous Joints

Cartilaginous Joints (Amphiarthrotic) Consist of hyaline or fibrocartilage 2 types: Synchondrosis – bands of hyaline cartilage Epiphyseal plate Costal cartilage Symphysis – pad of fibrocartilage that allows limited movement Intervertebral disks Symphysis pubis Slightly movable (amphiarthrotic)

Cartilaginous Joints (amphiarthrotic)

Synovial Joints (Diarthrotic) Articular cartilage (hyaline cartilage) covers the ends of bones A fibrous articular capsule encloses joint surfaces A joint cavity is filled with synovial fluid Ligaments reinforce the joint Most joints in the body are synovial

Synovial Joint Structure (Diarthrotic) Articular cartilage – hyaline cartilage; resists wear and minimizes friction Subchondral plate – somewhat elastic bone located under the articular cartilage Absorbs shocks and helps protect joint from stresses May fracture from excessive stress from obesity or athletic activities

Synovial Joint Structure continued… Joint capsule – has 2 distinct layers: Outer layer consists of dense CT whose fibers attach to the periosteum Flexible enough to allow movement but strong enough to hold the joint together Ligaments – bundles of strong, tough cartilaginous fibers that reinforce the joint capsule Synovial membrane – inner layer of the joint capsule Shiny, vascular lining of loose CT only a few cells thick Covers all surfaces within the the joint capsule except the articular cartilage

Synovial Joint Structure continued… Synovial cavity – area enclosed by the joint capsule Synovial fluid – clear fluid secreted by the synovial membrane that moistens and lubricates the joint cavity and supplies nutrients to the cartilage

Synovial Joint Structure continued… Menisci – fibrocartilage disks that partially or completely divide the joint into compartments between the articular surfaces Bursae – flattened fibrous sacs lined with synovial membrane and containing a thin film of synovial fluid. Common where ligaments, muscles, skin, tendons, or bones rub together. Knee Replacement Surgery

Ball-and-Socket Joints Bone with a globular head articulates with the cup-shaped cavity of another bone Widest range of motion and rotation Examples – hip, shoulder

Condyloid Joints Ovoid condyle fits elliptical cavity Wide range of motion, but no rotation Examples – metacarpals and phalanges

Gliding (plane) Joints Nearly flat or slightly curved articulating surfaces Allow sliding (back and forth) and twisting movements Examples – within the wrist and ankle, between vertebrae, sacroiliac joint, between ribs and sternum

Hinge Joints Convex surface of one bone joins concave surface of another bone Movement in one plane only Examples – elbow, phalanges

Pivot Joints Cylindrical surface of one bone rotates within a ring of bone Allows rotation only Examples – proximal radius and ulna, atlas and axis

Saddle Joints Bones with concave and convex regions on articulating surfaces Allows movement in 2 planes Example – trapezium and metacarpal 1 (thumb)

Joints Review (8:11)

Types of Ordinary Body Movements Flexion Decreases the angle of the joint Brings two bones closer together Typical of hinge joints like knee and elbow Extension Opposite of flexion Increases angle between two bones

Types of Ordinary Body Movements Rotation Movement of a bone around its longitudinal axis Common in ball-and-socket joints Example is when you move atlas around the dens of axis (shake your head “no”)

Types of Ordinary Body Movements Abduction Movement of a limb away from the midline Adduction Opposite of abduction Movement of a limb toward the midline

Types of Ordinary Body Movements Circumduction Combination of flexion, extension, abduction, and adduction Common in ball-and-socket joints

Special Movements Dorsiflexion Plantar flexion Lifting the foot so that the superior surface approaches the shin Plantar flexion Depressing the foot (pointing the toes)

Special Movements Inversion Eversion Turn sole of foot medially Turn sole of foot laterally

Special Movements Supination Pronation Forearm rotates laterally so palm faces anteriorly Pronation Forearm rotates medially so palm faces posteriorly

Special Movements Opposition Move thumb to touch the tips of other fingers on the same hand

Joint Movements Protraction Retraction Elevation Depression moving a part forward Retraction moving a part backward Elevation raising a part, shrug the shoulder Depression lowering a part, droop the shoulder

Shoulder Joint Ball and socket joint made up of the rounded head of the humerus and the glenoid cavity of the scapula. The joint capsule is loose. Muscles and tendons reinforce the joint. Shoulder joint is capable of a wide range of movements including flexion, extension, abduction, adduction, rotation, and circumduction.

Shoulder Joint Ligaments: coracohumeral ligament, glenohumeral ligaments, transverse humeral ligament, and glenoid labrum Bursae: subscapular, subdeltoid, subacromial, subcorocoid bursae

Coracoacromial Ligament Coracoclavicular Ligament

Knee Joint The knee is the largest and most complex synovial joint. It consists of the medial and lateral condyles at the proximal end of the tibia. The femur articulates with the patella. The joint capsule is thin and strengthened by muscles and tendons.

Knee Joint Ligaments of the knee joint: patella, oblique popliteal, arcuate popliteal, tibial collateral (MCL), fibular collateral ligament (LCL), anterior cruciate ligament (ACL) strengthen the joint capsule. Cruciate ligaments prevent displacement of articulating surfaces. Two fibrocartilaginous menisci separate the articulating surfaces.

Life-Span Changes Joint stiffness occurs due to a change in collagen structure. Fibrous joints strengthen over a lifetime.

Life-Span Changes Synchondrosis disappear over time as part of skeletal growth and development. Symphysis joints may lose water and flexibility may decrease.