The Skeleton: Structure and Functions
The Framework of Movement
The human skeleton is a living structure made of 206 bones that provides the framework for every movement you make in sport. Without it, muscles would have nothing to pull against. The skeleton works in partnership with the muscular system: muscles contract and pull on bones, which act as levers, creating movement at joints. Understanding which bones are where — and what they do — underpins everything else in PE.
Bones of the Skeleton: Head to Toe
Working from the top of the body downwards, the cranium sits at the very top of the head, curving down around the brain. Below it, the vertebrae form a column of 33 bones running from the base of the skull to the pelvis — protecting the spinal cord and giving the trunk both stability and a controlled range of movement.
At the shoulder, two bones are key. The scapula (shoulder blade) is a flat, triangular bone that sits across the upper back, providing attachment points for the muscles that control the shoulder. The humerus is the long bone of the upper arm, running from the shoulder joint down to the elbow. Together, the scapula and humerus form the shoulder joint — a ball-and-socket joint that allows the greatest range of movement in the body.
At the elbow, three bones meet. The humerus comes down from the shoulder. The radius runs along the thumb side of the forearm, and the ulna runs along the little-finger side. The elbow joint between the humerus and the ulna is a hinge joint allowing flexion and extension. The radius also rotates around the ulna to allow the forearm to turn palm-up or palm-down, a movement essential in racket sports.
Ball-and-socket joints are found at the hip (pelvis and femur) and shoulder (scapula and humerus). Hinge joints are found at the elbow (humerus, radius, ulna), knee (femur and tibia) and ankle (tibia, fibula and talus).
Moving to the lower body, the pelvis is a large basin-shaped structure of fused bones at the base of the spine. It forms the hip joint with the head of the femur — a ball-and-socket joint that allows the greatest range of movement in the lower limb. At the knee, the femur articulates with the tibia (the large shin bone), forming a hinge joint. The patella sits in front of the knee joint, protecting it and improving the mechanical advantage of the quadriceps muscle. The fibula runs alongside the tibia on the outer side of the lower leg, providing a point of attachment for muscles but bearing very little weight. Finally, the talus links the lower leg to the foot, sitting between the tibia and fibula above to form the ankle joint.
The Six Functions of the Skeleton
The skeleton does far more than hold the body upright. It serves six distinct functions, each of which can be applied directly to sport and physical activity.
Support — the skeleton holds the body upright against gravity. A sprinter’s lower limbs support their entire body weight as they drive off the blocks. Without a rigid skeletal frame, the muscular system would have nothing to act on.
Protection — flat bones protect vital organs. The cranium shields the brain; the ribs and sternum form a cage around the heart and lungs. In contact sports such as rugby, the ribcage absorbs impact forces that would otherwise damage the heart and lungs directly.
Movement — bones act as levers. When the biceps contracts during a bicep curl, the forearm bones (radius and ulna) pivot at the elbow to lift the load. In kicking a football, the femur swings at the hip and the tibia swings at the knee, producing explosive leg extension.
The spec distinguishes between long bones and short bones in terms of movement. Long bones such as the femur, tibia, humerus, radius and ulna enable gross movements — the large, powerful movements used in sprinting, jumping and throwing. Short bones, such as those in the wrist and ankle, enable finer, more controlled movements. Flat bones such as the cranium, ribs and scapula serve a protective function and provide broad surfaces for muscle attachment.
The shape and design of each bone directly determines how much movement it allows. The rounded head of the femur fits into the cup-shaped socket of the pelvis, allowing movement in all directions at the hip. The pulley-shaped end of the humerus fits into the groove of the ulna at the elbow, restricting movement to a single plane (flexion and extension only).
Attachment for muscles — the skeleton provides attachment points for muscles. Tendons connect muscles to bones at these points. When a muscle contracts, it pulls on its attachment point and the bone moves. Without firm attachment points, muscular contractions would produce no movement at all.
Mineral storage — bones store calcium and phosphorus. These minerals are released into the bloodstream when the body needs them, and exercise that loads the skeleton — such as weight training or running — stimulates the bones to increase their mineral density, making them stronger over time.
Blood cell production — red bone marrow inside flat and irregular bones produces red blood cells, white blood cells and platelets. Red blood cells carry oxygen to the working muscles during exercise via haemoglobin. This function links directly to cardiovascular performance: a well-functioning skeletal system supports oxygen delivery to muscles.
The six functions of the skeleton are: support, protection, movement, attachment for muscles, mineral storage and blood cell production. Each one can be applied to sport — for example, the femur acts as a lever during kicking (movement) and the ribs protect the lungs during a tackle (protection).
A common mistake is to write only about support and movement when asked for skeletal functions. All six functions are on the specification, so always aim for a wider range. Remember that flat bones protect organs (ribs protect the heart and lungs) and that the skeleton is a living structure involved in mineral storage and blood cell production. In a 6-mark analyse question, link blood cell production to oxygen delivery for aerobic exercise to show the depth a full answer needs.