Joints of the Human Body
Joints Joints are the points of contact (or articulations) between two connected bones. Joints hold bones together and many allow for flexibility and movement.
3 Types of Joints 1. Synarthrosis 2. Amphiarthrosis 3. Diarthrosis
Synarthrosis - immovable joints Fibrous Joints – Two bones grow together with only a thin layer of fibrous periosteum between them Example : sutures of the skull, teeth in their sockets
Amphiarthrosis – semi-movable joints a. Ligamentous - Slight movement permitted by meager elasticity of a ligament joining two bones, which may be distinctly separated. Example : distal articulation of tibia to fibula b. Cartilaginous - Connected to bone by cartilage tissue. Bones are coated with hyaline cartilage, separated by a fibrocartilage disc and joined by ligaments. Example : between vertebra (intervertebral discs), symphysis pubis
Diarthrosis – freely movable joints Synovial - bony surfaces are separated by lubricating fluid. They are also joined by ligaments, tough bands of elastic tissue that enclose the ends of articulating bones and form the capsule containing the synovial fluid.
Synovial Joints 1.Gliding (arthrodial) Allows gliding or twisting Example: between carpals or tarsals 2. Hinge (ginglymus) A concave surface glides around a convex surface allowing flexion and extension Example: humerus to ulna, phalanges
3. Pivot (trochoid) Rotation around a vertical axis is allowed. Movement in one plane Example : atlanto-axial joint 4.Ellipsoid An oval ball and socket joint allowing flexion, extension, abduction, adduction and circumduction but not rotation. One articular surface slightly concave and the other slightly convex. Example : radius and carpals
5. Saddle Both bones have a saddle shaped surface (fit into each other) Allows flexion, extension, abduction, adduction, and slight circumduction but NO rotation. Example : carpo-metacarpal articulation of thumb 6. Ball & Socket Spherical ball and socket. Allows flexion, extension, abduction, adduction, circumduction and medial and lateral rotation. Example : femur and acetabulum, humerus and glenoid cavity.
Work List the 6 MAJOR characteristics of synovial joints. (page 70) Label the diagram: The Characteristics of a Synovial Joint (page 70).
Textbook Work List the characteristics found in synovial joints. What are the two joints are found in the pectoral girdle? Briefly explain how each are important. Sternoclavicular Joint – joint must absorb all forces transmitted to the upper limb (lots of sports) Acromioclavicular Joint – shoulder separations can occur in many sports What are three joints found in the elbow? Humero-radial joint – flexion and extension, humero-ulnar joint – flexion and extension, and radioulnar joint – pronation and supination
Textbook Work Briefly describe the two joints of the pelvic girdle. Symphysis pubis – unites two pubic bones, softens before child birth Sacroiliac joint – unites the sacrum with the paired ilia
Related Joint Structures Ligaments Strong connective tissues that run from bone to bone and help to maintain stability in a joint They are not elastic and can lose their ability to perform correctly when stretched Fibrocartilage Occupies the space between certain bones to form the articluar surface and can take on many sizes and shapes Is round and are know as disks (e.g. those between the vertebrae of the spine), while others are flat or circular in shape (e.g. knee) Is resilient and functions as the shock absorber Not blood supply of its own and relies on synovial fluid for nourishment
Synovial Membrane Joint Capsule Bursae A thin tissue that surrounds most freely moving joints Membrane secretes synovial fluid which provides nourishment for cartilaginous disks, lubrication, and hydrostatic cushioning Joint Capsule A tough fibrous sheet that surrounds many joints and functions to protect them and to provide stability Bursae A liquid filled membrane that protects soft tissues as they pass by bony projections Others (found in some joints): articular discs, fibrocartilaginous labra, meniscus and intracapsular tendons