Anatomy Study Guide 4 - The Joints PDF

STUDY GUIDE Faculty of Medicine Lecture 4 Joints ILOS: student will be able to Determine types of joints (fibrous, cartilaginous & synovial)....

STUDY GUIDE Faculty of Medicine Lecture 4 Joints ILOS: student will be able to Determine types of joints (fibrous, cartilaginous & synovial). Describe the structure of synovial joint Joints: The site of meeting between 2 or more bones. According to their structure and mobility, they are classified into fibrous, cartilaginous and synovial joints. [A] Fibrous Joints (Synarthroses): The articular surfaces are connected together by strong fibrous tissue and no movements are permitted for protection and fixation. Fibrous joints include: a- Sutures of the skull: The connecting fibrous tissue is thin and frequently they ossifies with age. b- Syndesmosis: It is represented by the inferior tibio-fibular joint where the 2 bones are connected together by very strong fibrous tissue (the interosseous ligament) which does not ossify. c- Gomphosis: Fibrous joints between the teeth and the jaws. They do not ossify. [B] Cartilaginous Joints (Amphiarthroses): The bones are connected by cartilage. The cartilaginous joints are subdivided into: a- Primary Cartilaginous Joints (Synchondroses): The bones are connected by hyaline cartilage which does not permit movement and ossifies with age. It is seen in:. The epiphyseal cartilage (between epiphysis and metaphysis).. First costal cartilage (between first rib and sternum). The rest of the sterno-costal joints are plane synovial joints.. Base of the skull. b- Secondary Cartilaginous Joints (Symphysis): The articular surfaces of bones are covered by thin plates of hyaline cartilage and the opposing plates are connected together by a disc of dense white fibrocartilage which only permits limited movement. It ossifies rarely. It is seen in joints which lie in the midline of the body:. The intervertebral discs.. Symphysis pubis (between the 2 hip bones).. Joints between the pieces of the sternum. [C] Synovial Joints (Diarthrosis): - They are freely movable joints. Construction of a synovial joint:. The articular surfaces are covered by a thin plate of hyaline cartilage.. The joint is enveloped by a fibrous capsule which surrounds the joint cavity. The capsule is pierced by the articular vessels and sometimes by bursae. 1. Outside the capsule, a group of inextensible extracapsular ligaments are found. They support the joint and prevent its over movements.. The inside of the capsule is lined by a thin synovial membrane but leaves the articular surfaces uncovered. As a result, a completely closed space is formed by the synovial membrane and the articular surfaces. This space contains a synovial fluid which acts as a lubricant. According to the axes around which the movements occur and the shape of the articular surfaces, synovial joints are classified into: 1- Uniaxial Joints: Movements occur around one axis only: a- Hinge Joints: Movements occur around a transverse axis, allowing only flexion and extension, e.g., elbow joint. b- Pivot Joints: Movements occur around a vertical axis allowing rotation only, e.g., radioulnar joints. 2- Biaxial Joints: Movements occur around 2 axes: a- Ellipsoid (condyloid) Joints: One articular surface is oval and convex, the other is oval and concave. This type permits flexion and extension to occur around one axis while adduction and abduction are permitted around the other axis, e.g., the wrist joint. Rotation is not allowed in this type. b- Saddle Joints: Both articular surfaces are concavo- convex e.g., the carpo-metacarpal joint of the thumb. This type of joint permits flexion, extension, adduction or abduction, circumduction but no rotation. c- Condylar Joints: They are considered as double ellipsoid e.g., the knee joint. This type of joints permits flexion, extension and rotation but no adduction or abduction. 3- Multi axial Joints: Also called ball and socket joints. A rounded head of one bone is received into a cup-shaped depression in the other bone. All types of movements are allowed, e.g., shoulder and hip joints. 4- Plane Joints: The articular surfaces are flat and smooth. This shape allows only slight gliding movements, e.g., the acromio-clavicular joint. 2