The Skeleton

Facts It consists of 206 bones, held together at joints by strong fibres called ligaments.

Your Skeleton

Functions Of The Skeleton The skeleton has four main roles: Support Protect Movement Blood Production

Support It forms a framework to support your body and give it strength. It performs a similar role to steel girders in a tall building.

Protection Some parts of your body are delicate and can get easily damaged. Your cranium protects your brain. Your ribs and sternum protect your heart and lungs.

Movement Your muscles are firmly attached to your skeleton. Muscles work by contracting or getting shorter. When they contract they pull on bones. This makes the bones move.

Blood Production Some bones contain red bone marrow. This makes red cells, white cells and platelets for blood. The ribs, vertebrae, humerus and femur all have some red bone marrow.

Types of bones Four types of bones in your skeleton. Your bones are different shapes and sizes because they have different jobs to do. They are divided into four groups: Long Short Flat Irregular

Long Bones They have a diaphysis, epiphyses and a hollow centre. Your height, shoe size and glove size depend on long bones. Examples: Upper and lower arm, collar bone, ribs, metacarpals and phalanges.

Short Bones These are small and squat. These are spongy bones covered with a thin layer of compact bone. They are light and very strong. Examples: Carpals and tarsals.

Flat Bones These are also spongy bones between two layers of compact bone. They have a large surface area. Examples: Scapula, pelvis and cranium.

Irregular Bone These are spongy bones inside and compact outside. They are specially shaped to suit the job they have to do. Examples: Patella and the vertebrae.

The Vertebral Column Down the back of your skeleton is the backbone or vertebral column. It has several jobs to do. It must be able to bend and twist. So it is made up of 34 small bones instead of one long one called vertebrae. It must be strong, to support your body parts. So it is curved. Therefore it is stronger. (Think of arches in bridges) It must protect the spinal cord, the bundles of nerves running down from your brain. They have a hole for this in their design.

Parts of the vertebral column The vertebrae are divided into five groups, each with a different job. Cervical Thoracic Lumbar Sacrum Coccyx

Cervical Vertebrae This supports the neck and the head. It allows the most movement. It allows you to bend and tilt your head and look over your shoulder. There are 7 bones in this part of the spine.

Thoracic Vertebrae Your ribs are connected to these. They do not move much. This is because its main job is to protect your heart and lungs and stop them from getting squashed. There are 12 bones in this part of the spine.

Lumbar Vertebrae These are big bones. Their job is to support the rest of the spinal column. Its design allows plenty of twisting and turning. Powerful back muscles attach to the wings at each side. There are 5 bones in this part of the spine.

Sacrum The bones in this part are fused together to make one. It is then fused to the pelvic girdle. This makes a solid base for the trunk and legs. There are 5 bones in this part of the spine.

Coccyx Once again all the bones are fused together to make one. It is the remains of a tail that you we once had when we were apes. There are 5 bones in this part of the spine.

Other Bones of the Skeleton The cranium or brain case is made of 8 flat bones. The lower jaw bone is hinged so you can chew. You have 12 pairs of ribs. All are joined to your vertebrae at the back. Ten pairs are joined to your sternum at the front and the bottom two do not attach at the front and are called floating ribs. The patella is not attached to any other bone.