Anatomy and Physiology I BIOL 2401 Chapter 9 Articulations

Articulations A point where two skeletal elements meet. Skeletal elements: bone, cartilage, teeth Arthrology: study of joints Kinesiology: study of movement Classified on basis of structure or function 2

Classification Based on Function Synarthrosis: immovable (syn= together) Amphiarthosis: slightly moveable (amphi= on both sides) Diarthrosis: freely moveable (diarthro= double joint; very moveable) 3

Classification Based on Structure Types Fibrous: No joint cavity; bones held together by fibrous connective tissue. Cartilaginous: No joint cavity; bones held together by cartilaginous connective tissue. Synovial: Presence of joint cavity, allows free movement 4

Classification Based on Structure Fibrous Joints No joint cavity; bones held together by fibrous connective tissue. Synarthoses or amphiarthroses. Suture = seam; bones joined by thin layer of dense fibrous connective tissue. Synarthosis – immovable joint. When replaced by bone in an adult- synostosis Syndesmosis = Fibrous interosseous membrane or ligament. Amphiarthrosis – some movement. Gomphosis = Cone-shaped peg (tooth) fits into a socket (alveolar process of maxilla or mandible). Synarthrosis 5

Classification Based on Structure Cartilaginous Joints No joint cavity Bones held together by cartilage Examples: epiphyseal plate, pubic symphysis Types Synchondrosis Symphysis 6

Classification Based on Structure Cartilaginous Joints Synchondrosis: Bones connected by hyaline cartilage Synarthosis – Immovable joint. Epiphyseal plate of growing long bones; joints between ribs and sternum Symphysis: growing together Intervertebral discs and symphysis pubis. Amphiarthrosis – partial movement. 7

Classification Based on Structure Synovial Joints Cavity in the joint. Bones held together by a capsule and ligaments. Diarthrosis. Examples: knee, TMJ, shoulder, hip, elbow, interphalangeal joints. 8

Classification Based on Structure Synovial Joints Diarthrosis = freely movable. Synovial cavity with synovial membrane separates articulating bones: Articular capsule: encloses the synovial cavity, unites the articulating bones. Has two parts: fibrous capsule and synovial membrane (see next slide). Fibrous capsule: outer, dense irregular connective tissue; attaches to periosteum of articulating bones. Synovial membrane: Inner, areolar connective tissue with elastic fibers and some adipose. 9

Classification Based on Structure Synovial Joints Articular cartilages: hyaline cartilage; cover articular surface of bones to protect the ends of the bones. Synovial fluid: fluid secreted by synovial membrane of the articular capsule - Fills cavity - Lubricates joint - Nourishes articular cartilages - Contains phagocytes 10

Classification Based on Structure Synovial Joints – Accessory Structures Accessory ligaments Extracapsular ligaments lie outside the articular capsule. Intracapsular ligaments occur within the articular capsule. Articular discs (menisci) Pads of fibrocartilage within the synovial joint. Attached at their margins to the fibrous capsule. Make a better fit for the bones; add to stability. Bursae Sac-like structures. Reduce friction between bones, skin, tendons, muscles or ligaments Bursitis: Inflammation of the bursae. 11

Types of Movements Gliding: Surface of one bone moves back and forth and side to side over a flat surface. Angular: Increase or decrease in the angle between bones Flexion/extension Hyperextension Abduction/adduction Circumduction Rotation: Bone revolves around its own longitudinal axis Special: occurring only at particular joints Inversion/eversion Dorsiflexion/plantar flexion Protraction/retraction Supination/pronation Elevation/depression 12

Gliding Types of Movements at Synovial Joints Surface of one bone moves back and forth and side to side over a flat surface. No angular or rotational motion. Occurs at wrist and ankle joints. 13

Angular Types of Movements at Synovial Joints Increase or decrease the angle between the bones. Flexion: decrease in the angle between articulating bones. Extension: increase in the angle between two articulating bones Hyperextension: continuation of extension beyond the anatomical position. Prevented at some joints by the shape of the articulating bones and the ligaments associated with the joint. 14

Angular Types of Movements at Synovial Joints Abduction: movement of a bone away from the midline. Adduction: movement of a bone toward the midline. Circumduction: movement of the distal end of a part of the body in a circle. Results as a continuous sequence of flexion, abduction, extension, and adduction. 15

Rotation Types of Movements at Synovial Joints A bone rotates around its own long axis. Medial rotation: anterior surface of a bone or a limb is turned toward the midline. Lateral rotation: anterior surface of a bone or a limb is turned away from the midline. 16

Special Movements Types of Movements at Synovial Joints Elevation/Depression: upward/downward movement of a body part. Protraction/Retraction: movement anteriorly in transverse plane/return to anatomical position of a body part. The jaw and the shoulders. 17

Special Movements Types of Movements at Synovial Joints Inversion: movement of the soles medially at the intertarsal joints so that they face each other. Eversion: movement of the soles laterally at the intertarsal joints so that they face away from each other. Dorsiflexion: bending the foot superiorly at the ankle. Plantar flexion: bending the foot at the ankle toward the plantar surface. 18

Special Movements Types of Movements at Synovial Joints Supination: movement of the forearm at the proximal and distal radioulnar joints so that the palm is turned anteriorly (when the arm is straight) or superiorly (when the arm is flexed at the elbow). Pronation: movement at the same joints as in supination, but so that the distal end of the radius crosses over the distal end of the ulna and the palm is turned posteriorly (when the arm is straight) or inferiorly (when the arm is extended at the elbow). Opposition: movement of the thumb so that it touches the fingers. 19

Condyloid (Ellipsoid) Types of Synovial Joints Planar Hinge Pivot Condyloid (Ellipsoid) Saddle Ball and socket 20

Types of Synovial Joints Gliding (Planar) Joint Side-to-side and back-and-forth gliding movements. Monaxial Rotation prevented by ligaments Examples Intercarpal/intertarsal joints Sternoclavicular joints Vertebrocostal joints Between patella and femur 21

Types of Synovial Joints Hinge Joint Concave surface of one bone articulates with and fits into the convex surface of another bone. Monaxial. Flexion or extension Examples: Knee, elbow, ankle, interphalangeal joints. 22

Types of Synovial Joints Pivot Joint Round or pointed surface of one bone fits into a ring formed by another bone and a ligament. Rotation Monaxial Proximal radioulnar joint (supination and pronation); atlanto-axial joint (“no” movement of head). 23

Types of Synovial Joints Condyloid Joint (Ellipsoid) Oval-shaped condyle of a bone fits into an elliptical cavity of another bone Flexion, extension, adduction, abduction, circumduction Biaxial movement Wrist, metacarpophalangeal joints for digits 2 through 5 24

Types of Synovial Joints Saddle Joint Articular bones are shaped like saddle and rider Flexion, extension, abduction, adduction, circumduction Biaxial Trapezium of carpus and metacarpal of the thumb 25

Types of Synovial Joints Ball and Socket Joint Ball-shaped surface of a bone fits into the cup-like depression of the second bone. Flexion, extension, abduction, adduction, rotation, circumduction. Triaxial Shoulder and hip joints 26

Arthritis Osteoarthritis Degenerative disease caused by aging and wear and tear. Degeneration of cartilage, no involvement of synovial membrane Can cause production of bone spurs that restrict movement After joint is stationary for a time, pain at first movement that diminishes with continued movement Gouty Arthitis Urate crystals, a waste product of DNA and RNA metabolism, build up in joints causing pain. Crystals are deposited in cartilage causing inflammation and swelling Bones can fuse Occurs in middle-aged men with an abnormal gene Rheumatoid Arthritis Autoimmune disorder where white blood cells attack articular cartilages Inflammation, swelling , severe pain Deformation of extremities Eventual fusion of the joints 27

Other Disorders Lyme disease Bacterial infection transmitted by deer ticks. Joint stiffness, fevers, chills, headache, stiff neck. First associated with Lyme, Connecticut Ankylosing spondylitis Syndrome of unknown cause that affects joints between the vertebrae and between the sacrum and hip bone. Ankle sprains Most common joint to be sprained or fractured. Treatment includes “RICE”: rest, ice, compression, elevation. 28

Aging and Joints Decreased production of synovial fluid Thinning of articular cartilages Loss of ligament length and flexibility Arthroscopy: joint examination using instruments the size of a pencil that allows the use of tiny instruments and a tiny microscope. Small incision through which repairs can be made including removal of torn cartilages of the knee. Arthroplasty: replacement of a joint. Hip, knee and shoulder are commonly replaced. Articular elements are replaced by plastic/stainless steel. 29