2What is a Joint in the Anatomical Body? A joint (articulation) is where two or more bones come into contact or articulate with each other. Their main function is to increase mobility of the body and limbs.
3Classification of the Joints Joints are classified according to a number of features. The most basic classification relies on the presence or absence of a joint cavity. In other words….if there is a gap between articulating bones. Further classification is based on: *Shape of the articulating bones *Type of tissue that connects the bones together
4Classification of the Joints The shape of the bones and subsequently the amount of movement allowed varies between joints, therefore the structure and function of the joints are highly interrelated. Some joints allow little or no movement, others allow movement in one direction only, while others allow a wide range of movements in several directions. Can you think of some joints that describe the above statement?
5Joint Movement and Stability *Movement is linked to stability*More movement a joint has the less stable*The less stable the greater risk for injury
6Joint Movement and Stability Factors that affect stability around the joints include:*The shape of the bones and whether they interlock with each other or not.*The area over which the bones are in contact*The flexibility of the ligaments*The influence of the other soft tissue structures such as the muscles, tendons, joint capsules
7Joint StabilityDepending on the joint, there can be numerous ligaments around it for support.A ligament is – a strong, flexible tissue that connects bone to bone.
8Joint Stability *They provide stability. Ligaments can be:*In the form of strap-like bands or round cords that generally pass over joints.*They provide stability.*Help to maintain the bony arrangement.*Restrain joint movement once they reached normal limits
9Joint Stability*Resist movement that the joint was not designed for. *Not very elastic and can be torn if suddenly and violently stretched. *Long time to heal – may never return to normal length
10Example: ElbowIn the anatomical position, there are ligaments on the medial and lateral side of the elbow to resist movement sideways.
11Types of Joints1. Fibrous2. Cartilaginous3. Synovial
12Example: Between the sutures of the skull Types of JointsFibrous – have a thin layer of fibrous tissue connecting the edges of the two bones. This is a continuous with the periosteum (Remember what this is?) and no movement is allowed at these joints.Example: Between the sutures of the skull
13Types of JointsCartilaginous joints – the bone can be separated by a fibrocartilage disc (ex: the intervertebral disc located between vertebrae), or by a thick layer of hyaline cartilage (ex: connecting the ribs to the sternum).There is limited amount of movement allowed at these joints.
14Types of Joints3. Synovial Joints – most common occurring joints in the body and are the most important for joint mobility. They have several distinctive features.
15Features of the Synovial Joint Articular Cavity – space between the bonesArticular Capsule – is a sleeve like structure that surrounds the joint. It is flexible enough to allow joint movement, but tensile strength protects the joint from dislocation.3. Synovial membrane – lines the inside of the capsule. It secretes fluid which lubricates the joint cavity, reducing friction and provides nutrients to the cartilage.
16Features of the Synovial Joint 4. Articular cartilage (Hyaline) – smooth, white layer that covers the bone. Its main function is to reduce friction, absorb shock and protect the bones. It varies in thickness depending on the amount of stress that it is exposed to .
17Types of Synovial Joint GlidingHingePivotCondyloidSaddleBall and Socket
18Types of Synovial Joint Gliding – have the least amount of movement. The surfaces of the bones are flat or slightly curved and they glide back and forth form side to side across each other. Gliding joints are found between the tarsal bones and between the carpal bones.
19Types of Synovial Joint Hinge Joints – bend (flex) or straighten (extend) in one direction only. Example: the elbow joint.
20Types of Synovial Joint Pivot Joint – one bone forms a ring in which the other bone rolls or pivots allowing the rotation of the joint. Example: ulna and radius
21Types of Synovial Joint Condyloid Joint – are formed where an oval or egg-shaped convex surface fits into a reciprocally shaped concave shape. Example: Between the radius and the carpal bones of the wrist…you can move your wrist up and down and side to side.
22Types of Synovial Joint Saddle Joint – the bones are shaped like a saddle and rider sitting in the saddle. Example: Found between the metacarpal of the thumb and the carpal bone next to it. These two joints can move in two directions (side to side and up and down).
23Types of Synovial Joint Ball and Socket Joints – can move in all directions and therefore have the greatest amount of movement. They are formed when the sphere shaped head of one bone fits into a rounded cavity on the other bone. Example: Shoulder and Hip joints