1. IB SEHS
Joints
Chapter One

2. What 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.

3. Classification 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

4. Classification 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?

5. Joint Movement and Stability
*Movement is linked to stability
*More movement a joint has the less stable
*The less stable the greater risk for injury

6. Joint 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

7. Joint Stability
Depending on the joint, there can be numerous ligaments around it for support.
A ligament is – a strong, flexible tissue that connects bone to bone.

8. Joint 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

9. Joint 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

10. Example: Elbow
In the anatomical position, there are ligaments on the medial and lateral side of the elbow to resist movement sideways.

11. Types of Joints
1. Fibrous
2. Cartilaginous
3. Synovial

12. Example: Between the sutures of the skull
Types of Joints
Fibrous – 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

13. Types of Joints
Cartilaginous 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.

14. Types of Joints
3. Synovial Joints – most common occurring joints in the body and are the most important for joint mobility. They have several distinctive features.

15. Features of the Synovial Joint
Articular Cavity – space between the bones
Articular 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.

16. Features 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 .

17. Types of Synovial Joint
Gliding
Hinge
Pivot
Condyloid
Saddle
Ball and Socket

18. Types 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.

19. Types of Synovial Joint
Hinge Joints – bend (flex) or straighten (extend) in one direction only. Example: the elbow joint.

20. Types 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

21. Types 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.

22. Types 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).

23. Types 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