Body Systems
Session 1 - The Skeletal System

This resource is suitable to support Level 2 Agriculture courses.

The Skeleton

The functions of the skeleton are:

Protection of vital organs (e.g. brain, lungs, heart)
Maintaining the shape or form of the body
Allowing the animal to move
Production of blood cells
Storage of minerals

Structure of the Skeleton

The basic structure of bones and joints are similar for most mammals, although they have specific adaptations to their environment.

Bones

Bones are made up of living material and contain minerals (calcium, phosphorus and magnesium) to make them hard and strong.

Long bones such as the femur contain bone marrow in the centre of the bone.

Bones have a good blood supply. In addition to this, red blood cells are produced within bones in a site known as the red bone marrow.

Bone Marrow

Calcium

Calcium is needed in the diet of young animals for growth to ensure their bones are strong and healthy.

Lack of calcium can lead to rickets (a deficiency disease which will prevent correct bone development).
Adult animals with a calcium deficiency in their diets may be able to move calcium from the bones into the bloodstream e.g. lactating dairy cows.
As animals become older they can find it harder to release the calcium and this can lead to milk fever (hypocalcaemia)

Joints

Definition: A joint exists where two bones meet.

The structure of joints governs the directions and the amount of movement of the joint.

What are the component parts of a joint?

A joint is made up of the following tissues:

Ligaments – tough fibres that link bones together.
Tendons –fibres that attach muscles to bones.
Cartilage – a smooth slippery layer that covers the ends of the bones and reduces friction.
Synovial fluid – the liquid that lubricates the joint.

How does the skeleton help movement?

Types of Joints

There are 3 main types of joints:

Fixed joints
Cartilaginous joints
Synovial joints

Fixed Joints

The bones interlock so that no movement can take place.

E.g. the skull.

Cartilaginous joints

The are joints that move slightly.

Here the bones are joined together by cartilage so there is a limited amount of movement.
These joints occur in the spine, between the vertebrae.

Synovial joints

These are freely moveable.

These joints have a capsule of synovial fluid and cartilage at the ends of the bones.
Examples of these types of joints include ball and socket joints (e.g. hips, and shoulders) and hinge joints (e.g. elbows).

Skeletal Health Problems

Joint ill

This is also known as polyarthritis, which means arthritis or inflammation in the joints.

This is caused when bacteria enter the navel of a newborn lamb or calf and travels to the joints.

There, it settles in the joint and causes extreme pain and deformity.

Body Systems Session 1 - The Skeletal System