Bones

Bones

The Main bones in the body

Ossification and Composition

The bones of embryos are made largely of cartilage. They are soft.

The process of ossification uses calcium to create bone as the child grows and matures.

The skeleton has over 200 bones.

Bone Growth Bones gradually become hard and

strong. With age bones lose their density and

strength. When severe this is called osteoporosis.

Eating foods containing calcium and exercising regularly helps bones to develop and stay stronger for longer.

Different Bones

Joints and their function A joint is where two or more bones meet.Synovial joints Cartilage reduces friction. Acts as a shock

absorber. Synovial fluid lubricates the joint. Synovial membrane produces synovial fluid. Tendon joins muscle to bone enabling

movement. Ligament joins bone to bone, stabilising the

joint.

Joint actions Abduction Movement away from the

mid-line of the body Adduction Movement towards the mid-

line of the body Extension Straightening limbs at a joint –

moving bones apart Flexion Bending the limbs at a joint. –

moving bones towards each other Rotation A circular movement around a

fixed point

Types of Joint Hinge Elbow, knee, fingers; Movement=Flexion, extension

Ball and Socket Shoulder, hip MovementFlexion, extension, abduction,

adduction, rotation

Pivot Between the atlas and axis in the neck

General Functions of the Human Skeleton

Protection - the cranium and ribs protect the brain and vital organs in the chest.

Shape - gives shape to the body and makes you tall or short.

Support - holds your vital organs in place when playing sport. The vertebral column holds the body upright.

Movement - muscle are attached to bones, which are jointed. When the muscles contract the bones move.

Blood production - red blood cells (to carry oxygen) and white blood cells (to protect against infection) are produced in the bone marrow of some bones.

Vertebrae Cervical Vertebrae – supports the head and the

neck and allows it to nod and rotate Thoracic Vertebrae – ribs are attached making a

protective cage. It allows some movement bending forward and backward and side to side

Lumbar Vertebrae - allows much flexibility; bending forward and backward and side to side but is prone to injury

Sacral Vertebrae – these are fused together and make a strong base. Transmit force from legs to upper body

Coccyx – fused vertebrae with no special use

Importance of diet and exercise

Bone can change in strength, density and shape. The body does most of its bone building during the first 30 years of life. Bone is constantly being broken down and replaced, however, bone loss begins to outpace bone growth between the ages of 30 and 35.

You can maintain bone strength by increasing intake of calcium, vitamin D and fibre. Also doing weight bearing exercise e.g. walking, jogging, bicycling, tennis, basketball, soccer and dancing.

Importance of bones in terms of body size

Heavier people have stronger bones as the bones respond to the weight that they have to carry. Therefore they tend to be better at sports like rugby or wrestling.

People with smaller bones tend to be better at flexible sports e.g. gymnastics or dance.

Your bone structure is most influenced by your genes

Homework