BONES AND JOINTS Basic Anatomy

The Skeleton The average human adult skeleton has 206 bones joined to ligaments and tendons Forms a protective and supportive framework for the attached muscles and the soft tissues which underlie it. Minor differences between male and female skeletons: men's bones tend to be larger and heavier than corresponding women's bones, and a woman's pelvic cavity is wider to accommodate childbirth.

SKELETAL FUNCTION The skeleton plays an important part in movement by providing a series of independently movable levers, which the muscles can pull to move different parts of the body It supports and protects the internal body organs It is an efficient factory which produces red blood cells from the bone marrow of certain bones and white cells from the marrow of other bones The bones are also a storehouse for minerals - calcium, for example - which can be supplied to other parts of the body

JOINTS Joints permit bodily movement and are held together by fibres called "ligaments". Some joints, like those in the skull, allow no movement. Others may permit only limited movement: for example the joints in the spine allow some movement in several directions. Moveable joints are continuously lubricated to prevent friction. These joints have a variable range of movement, and these are called "synovial" joints.

JOINTS Joints are sturdy enough to hold the skeleton together while permitting a range of motions. Joints are lubricated by "synovial" fluid. The ends of these joints are coated with articular (or hyaline) cartilage, which reduces friction and cushions against jolts. Between the bones, in a narrow space, is the joint "cavity," which gives us freedom of movement. Ligaments then bind these bones to prevent dislocations and limit the joint's movements.

Joint Types 1: Ball and Socket The greatest range of joint movement is provided by a "ball-and- socket" joint, in which the spherical head of one bone lodges in the spherical cavity of another                  

Joint Types 2: Hinge The simplest type of joint is the "hinge," as found in the elbows and the joints of the fingers and toes. Hinge joints allow movement in only one direction.                 Elbow

Joint Types 3: Pivot A pivot joint allows two bones to move in a rotational motion by twisting against each other The radio-ulnar joint in the elbow, or atlas/axis in the neck do this

Joint Types 4: Gliding Gliding" joints permit a wide range of mostly sideways movements - as well as movements in one direction The bones in the wrists and ankles slide against each other in a gliding motion The spine is a series of gliding joints                     

Joint movement: Extension When two bones move away from each other, the action is known as EXTENSION This would occur for example with straightening of the elbow or knee

Joint movement: Abduction When a joint moves away from the vertical centreline of the body, it is known as abduction. This movement occurs when the arm is raised to one side

Joint movement: Adduction When a joint moves towards the vertical centreline of the body, it is known as adduction. This movement occurs when the arm is lowered

Joint movement: Rotation This occurs when a bone rotates, either in a socket or relative to another bone. It can occur at ball & socket or gliding type joints Lowering (blue arrow) is internal rotation. Raising is external

Joint movement: General For all joints except the knee and elbow Forward movement is flexion Rearward movement is extension