ANATOMY AND PHYSIOLOGY

The Skeleton, Bones and Joints

The Skeleton, Bones and Joints

skeleton

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Your skeleton is composed of more than 200 bones. It has a number of vital functions including support, protection and movement. It’s also the region in which blood is produced. Joints are also important because they allow you to move freely. However, as you get older they harden and so movement gets more difficult

Skeleton functions

There are five main functions of the skeleton:

  • Protection: for instance, the ribs protect the vital organs located in the chest while the cranium protects the brain.
  • Shape: it controls the shape of your body and your height.
  • Support: it makes sure that your vital organs stay where they’re meant to and your vertebral column keeps the body upright.
  • Movement: the bones are connected to the muscles and when the muscles contract and relax the bones move accordingly.
  • Blood production: in the bone marrow of certain bones red blood cells and white blood cells are produced.

For your exam you should learn all the major bones of the body.

The vertebral column

The vertebral column is important in a number of ways for exercising or playing sport. It’s composed of vertebrae and between each vertebra are discs which act as shock absorbers.

The vertebral column can be split up into five sections, each of which plays a different role.

The cervical vertebrae are the smallest vertebrae in the vertebral column and its role is to:

  • support the head and neck
  • the top vertebrae, the atlas, lets the head nod
  • the second vertebrae, the axis, lets the head rotate

The thoracic vertebrae are attached to the ribs which forms a protective cage. They also allows for some movement: bending forwards, being backwards and moving from side to side.

The largest of the vertebrate are the lumbar vertebrate and they allow for a lot more flexibility, allowing the body to bend forwards, backwards and from side to side. They’re more prone to injury than the other sections.

The scaral vertebrae, which make up the sacrum, are different from the others in that they’re fused together. This allows them to form a strong and solid base so that force can be transmitted from the legs to the upper body.

The coccyx vertebrate are also fused together however they’re of no special use.

Joints

Joints are where two bones meet. There are three types of joint in the body:

  • Fibrous joints: these are fixed or immovable joints, for example the joints in skull bones.
  • Cartilaginous joints: these joints are slightly moveable and the bones are separated by cartilage, for instance the joints between vertebrates.
  • Synovial joints: these are able to move freely, for example the elbow joint. They contain a fluid called synovial fluid inside a synovial membrane surrounding the joint.

Synovial joints are made up of five main components:

  • Cartilage: this reduces friction and also acts as a shock absorber.
  • Tendon: this connects the muscles and bone together thereby allowing movement.
  • Ligament: this connects bone to bone which stabilises the joint.
  • Synovial fluid: this gives lubrication to the joint.
  • Synovial membrane: this makes the synovial fluid.

Limbs are able to move in a number of directions. They achieve this by using joint actions. Limb movements can be described in a number of ways:

Movement Description
FlexionExtension

Adduction

Abduction

Rotation

The angle at the joint is reduced, like bending the knee or the elbow.The angle at the joint is increased, for instance when the knee or elbow is straightened.A body part is moved towards the centre of the body, like one leg is brought in towards the other leg

This is where the body part is moved away from the centre of the body, for example when one leg is moved away from the other.

This involves turning or twisting a body part either clockwise (lateral or external) or anti-clockwise (medial or internal). An example would be turning the legs so the toes point outwards.

Bone formation

Bones are actually formed from cartilage. The process by which cartilage turns into bone is called ossification. When you were born your bones would have originally been made from cartilage and ossification would have matured the bones and made them hard and strong. As people get older, however, bones begin to lose their density. Sometimes this can be very severe and is known as osteoporosis. To help slow down this process it’s important to take regular exercise and consume plenty of calcium.

Bones are classified in four groups

Type Description Example Sport function
Long bones

Short bones

Flat bones

Irregular bones

The body of these bones is longer than their width and they have a hard casing with centre composed of spongy bone.In general they’re as wide as they are long. They’re composed of a lot of bone marrow.

These bones are flat and strong. Their main roles are to protect and for muscles attachment.

They have their own category because they don’t fit into the other three due to their unusual shapes.

FemurHumerusMetatarsals

Tarsals

Carpals

Cranium (skull)

Scapula (shoulder blade)

Vertebrae

Mandible

Sacrum

Movement, strength and speed

Shock absorption

Protection and movement

Shape and protection

Long bone composition

Long bone is composed of a number of parts:

Part Function
EpiphysisHyaline cartilage

Cancellous bone

Epiphyseal plate

Diaphysis

Periosteum

Compact bone

Marrow cavity

This is the ‘head’ of the bone.This covers both ends of the bone to prevent them from rubbing together and work as a shock absorber.This is spongy bone which contains red bone marrow where red blood cells are formed.

This is the section where the bone grows.

This is the middle section of the bone known as the shaft.

This is where the ligament s and tendons attach to the bone. It also forms a protective layer where there isn’t any hyaline cartilage.

This is hard bone which gives strength to the hollow section of the bone.

Also known as the medullary cavity, this contains yellow bone marrow where white blood cells are formed.

Muscles and movement

REMEMBER IT

  • Voluntary muscles can be controlled whereas involuntary muscles function independently.
  • Slow twitching muscles only use a little force so don’t tire as quickly as fast twitching muscles which use more force.
  • Muscles can contract isometrically, in which the muscle length stays the same, or isotonically, where the muscle length changes leading to movement.
  • The muscles come in pairs and work antagonistically: when one contracts the other relaxes.
  • When muscles are toned they become larger (hypertrophy).
  • Toning is good for developing a good posture.