Chapter 9 Articulations Articulations joints where two bones interconnect. Two classification methods are used to categorize joints:

Size: px

Start display at page:

Download "Chapter 9 Articulations Articulations joints where two bones interconnect. Two classification methods are used to categorize joints:"

Hilary Morgan
6 years ago
Views:

1 Chapter 9 Articulations Articulations joints where two bones interconnect Two classification methods are used to categorize joints: Functional classification Structural classification Functional classification A. Synarthroses (Immovable Joints) Four types of synarthrotic joints: 1. Suture 2. Gomphosis 3. Synchondroses 4. Synostoses B. Amphiarthroses (Slightly Movable Joints) Two major types: 1. syndesmosis 2. symphysis C. Diarthroses (Freely Moving Joints) Synovial Joints A synovial joint is surrounded by a fibrous articular capsule and a synovial membrane that lines the walls of the articular cavity. The membrane does not cover the articulating surfaces within the joint. Major features of synovial joints: 1. Articular cartilages 2. Synovial Fluid A clear, viscous solution with the consistency of heavy molasses Usually less than 3 ml at any one joint Three primary functions: a. articular cartilages behave like sponges filled with synovial fluid. When the cartilage is compressed, some of the synovial fluid is squeezed out of the cartilage into the space between the opposing surfaces. This reduces friction. b. The synovial fluid in a joint must circulate continuously to provide nutrients and a waste disposal route for the chondrocytes of the articular cartilages. It circulates whenever the joints move. c. - Synovial fluid cushions shocks in joints that are subjected to compression. 3. Accessory Structures Includes pads of cartilage or fat, ligaments, tendons, and bursae. a. cartilage o o meniscus (pad of fibrocartilage) and fat pads lie between the opposing articular surfaces. A meniscus can subdivide a synovial cavity, channel the flow of synovial fluid, or allow for variations in the shapes of the articular surfaces. b. fat pads o Fat pads act as packing material to fill in the spaces created as the joint cavity change shape when you move.

c. ligaments d. tendons Sprain e. bursae Factors that stabilize a joint A joint cannot be both highly mobile and very strong. The greater the range of motion at a joint, the weaker it becomes.

ligaments o The shapes of the articulating surfaces and menisci, which may prevent movement in specific directions o The presence of other bones, skeletal muscles, or fat pads around the joint o

2 c. ligaments d. tendons Sprain e. bursae Factors that stabilize a joint A joint cannot be both highly mobile and very strong. The greater the range of motion at a joint, the weaker it becomes. Several factors are responsible for limiting the range of motion, stabilizing the joint, and reducing the change of injury: o The collagen fibers of the joint capsule and any accessory or extrinsic ligaments o The shapes of the articulating surfaces and menisci, which may prevent movement in specific directions o The presence of other bones, skeletal muscles, or fat pads around the joint o Tension in tendons attached to the articulating bones Injuries Dislocation Subluxation - Movements of Synovial Joints 1. Linear motion 2. Angular motion Types of angular motion: a. flexion b. extension c. hyperextension d. abduction e. adduction f. circumduction

3 3. Rotation Medial rotation Lateral rotation Two types of rotation: Pronation - Supination - Special Movements Several special terms apply to specific articulations or unusual types of movement. 1. Inversion 2. Eversion 3. Dorsiflexion 4. Plantar flexion 5. Opposition 6. Protraction 7. Retraction 8. Elevation 9. Depression 10. Lateral flexion A Structural Classification of Synovial Joints Synovial joints are described as gliding, hinge, pivot, ellipsoidal, saddle, or ball-and-socket joints on the basis of the shapes of the articulating surfaces. Each type of joint permits a different type and range of motion. This includes: 1. Gliding joints 2. Hinge joints 3. Pivot joints 4. Ellipsoidal joint 5. Saddle joint 6. Ball-and-socket joint A joint cannot be both mobile and strong The greater the mobility, the weaker the joint Mobile joints are supported by muscles and ligaments, not bone-to-bone connections

4 Intervertebral Articulations The articulations between the superior and inferior articular processes of adjacent vertebrae are gliding joints that permit small movements associated with flexion and rotation of the vertebral column. Little gliding occurs between adjacent vertebral bodies. From axis to sacrum, the vertebrae are separated and cushioned by intervertebral discs (pads of fibrocartilage). They are not found in sacrum, coccyx, or between the first and second cervical vertebrae. The Intervertebral Discs Annulus fibrosus- Nucleus pulposus Movement of the vertebral column compresses the nucleus pulposus and displaces it in the opposite direction which allows for smooth gliding movements between vertebrae. Intervertebral Ligaments Function- Ligaments interconnecting adjacent vertebrae include the following: a. anterior longitudinal ligament connects the anterior surfaces of adjacent vertebral bodies b. posterior longitudinal ligament parallels the anterior longitudinal ligament and connects the posterior surfaces of adjacent vertebral bodies c. ligamentum flavum connects the laminae of adjacent vertebrae d. interspinous ligament connects the spinous processes of adjacent vertebrae e. supraspinous ligament interconnects the tips of the spinous processes from C7 to the sacrum f. ligamentum nuchae extends from C7 to the base of the skull. Damage to Intervertebral Discs Slipped disc Herniated disc The Shoulder Joint Joint is a ball-and-socket diarthrosis formed by the articulation of the head of the humerus with the glenoid cavity of the scapula A fibrocartilaginous glenoid labrum increases the extent of the glenoid cavity and deepens the socket The major ligaments that help stabilize the shoulder joint are the glenohumeral, coracohumeral, coracoacromial, coracoclavicular, and the acromioclavicular ligaments The Elbow Joint The elbow joint is extremely stable because: 1. the bony surfaces of the humerus and ulna interlock 2. a single, thick articular capsule surrounds both the humeroulnar and proximal radioulnar joints 3. the articular capsule is reinforced by strong ligaments The Hip Joint A projecting rim of fibrocartilage (acetabular labrum) increases the depth of the joint cavity.

The Knee Joint Menisci of the knee Medial and lateral menisci Fibrous cartilage pads At femur tibia articulations Cushion and stabilize joint Give lateral support Locking knees Standing with legs

the tendons of associated muscles. A pair of fibrocartilage pads, the medial and lateral menisci, lie between the femoral and tibial surfaces.

5 The Knee Joint Menisci of the knee Medial and lateral menisci Fibrous cartilage pads At femur tibia articulations Cushion and stabilize joint Give lateral support Locking knees Standing with legs straight: locks knees by jamming lateral meniscus between tibia and femur The articular capsule at the knee joint is thin and in some areas incomplete, but it is strengthened by various ligaments and the tendons of associated muscles. A pair of fibrocartilage pads, the medial and lateral menisci, lie between the femoral and tibial surfaces. The menisci have three functions: Seven Ligaments of the Knee Joint Patellar ligament (anterior) Two popliteal ligaments (posterior) Anterior and posterior cruciate ligaments (inside joint capsule) Tibial collateral ligament (medial) Fibular collateral ligament (lateral)

Skeletal System Joints, Relationship with other systems

Skeletal System Joints, Relationship with other systems Review the Types of Bones Articulations Classification of Joints (Articulations) Joint Where two bones interact Three functional classes of joint