Skeletal System
Skeletal system
The skeleton is the central structure of the body and is made up of bones, joints and cartilage. The skeleton provides the framework for muscles and gives the body its defined human shape.
bones in the arm and leg
The bones in the arm and leg support a number of sporting movements. They are labelled below, the leg on the left and the arm on the right.
Ensure you can label these correctly e.g. the Tibia is the Thicker bone on the lower leg.
Functions of the skeletal system
The skeleton has five main functions:
Movement – the skeleton allows movement of the body as a whole and its individual parts. The bones act as levers and also form joints that allow muscles to pull on them and produce joint movements.
Support and protection – the bones of the skeleton provide support for the body and also protect the organs found within it. For example, the cranium protects the brain, the ribs offer protection to the heart and lungs, the vertebrae protect the spinal cord and the pelvis offers protection to the sensitive reproductive organs.
Production of blood cells – certain bones in the skeleton contain red bone marrow and the bone marrow produces red blood cells, white blood cells and platelets. Examples of bones that contain marrow are the pelvis, sternum, vertebrae and clavicle.
Storage of minerals – the bones themselves are made of minerals and act as a mineral store for calcium and phosphorous, which can be given up if the body requires the minerals for other functions.
Attachment of muscles – the bones of the skeleton provide surfaces for the attachment of muscles. This is why bones are often irregular shapes and have bony points and grooves to provide attachment points.
Role of joints and connective tissue
A joint is a place where two or more bones meet and is also called an articulation.
Connective tissues consist of ligaments, cartilage and tendons.
A joint is held together by ligaments which give the joints their stability.
Cartilage is found at the ends of bones and where joints meet.
Tendons attach muscles to the skeleton.
Synovial joints
These joints allow a wide range of movement and all have a similar joint structure.
Articular capsule – keeps the contents of the synovial joint in place.
Synovial membrane – releases synovial fluid into the joint.
Synovial fluid – a solution which lubricates the joint and allows free movement.
Articular cartilage – prevents wear and tear on the bones.
Types of synovial joints
Different types of synovial joints allow varying degrees of movement, these include:
Hinge – these types of joint can be found in the elbow and knee. Hinge joints are like the hinges on a door, and allow you to move the elbow and knee in only one direction. They allow flexion and extension of a joint.
Ball and socket – these types of joint can be found in the shoulder and hip and allow movement in almost every direction. A ball-and-socket joint is made up of a round end of one bone that fits into a small, cup-like area of another bone.
Pivot – this joint can be found in the neck, between the top two vertebrae. It allows only rotational movement, such as moving your head from side to side as if you were saying ‘no’
Types of joint movement
The different types of movement that are permitted at each joint are given specific terms.
Flexion – bending a joint. This occurs when the angle of a joint decreases. For example, the elbow flexes when performing a bicep curl.
Extension – straightening a joint. This occurs when the angle of a joint increases, for example, when throwing a shot put.
Abduction – movement away from the midline of the body. This occurs in the hip and shoulder joints during a jumping jack movement.
Adduction – movement towards the midline of the body. This occurs in the hip and shoulder joints, returning the arms and legs back to their original position from a jumping jack movement.
Circumduction – this is where the limb moves in a circle. This occurs in the shoulder joint during an overarm tennis serve.
Rotation – this is where the limb moves in a circular movement around a fixed joint, towards or away from the midline of the body. This occurs in the hip joint in golf, while performing a drive shot.
TYPE OF JOINTBODY LOCATIONTYPES OF MOVEMENT
Muscular-skeletal system
The muscular system works in conjunction with the skeleton to produce movement of the limbs and body.
Ligaments and tendons are two main types of connective tissue that help the muscular-skeletal system produce movements.
Ligaments:
attach bone to bone
act to give stability to joints
are tough, white and inelastic
Tendons:
attach muscle to bone
carry the force from muscle contraction to the bone
are tough, greyish and inelastic