6.9Chapter 6: Nutrition, Health and Movement

The human skeleton — Alhussan Biology - Stage 8 Revision Notes & Topical Questions

5 min read 6 parts Lesson 9 of 12 2 quizzes

📚 Alhussan Biology - Stage 8 Hub / Topical Revision

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Lesson summary

Biology 6.9 The human skeleton — Bones, Joints and Support — Alhussan International Academy — Biology (Stages 7–9) notes: Describe the functions of the skeleton, the structure of bone and the main joints.Skeleton = all the bones of the body together, and humans are vertebrates bu…

Importance
Living tissue
Protection
Making blood cells
Mineral store
Compact bone

Part 1 of 4The skeleton

Skeleton

Skeleton all the bones of the body together, and humans are vertebrates built around bones of different sizes and shapes.

Number

Number the average adult has 206 bones.

Importance

Importance without a skeleton a person would be like a giant jellyfish and moving would be very difficult.

Living tissue

Living tissue a museum skeleton is dry, white and dead, but bone in the body is a strong, slightly flexible, living tissue with a good blood supply.
It grows and changes all the time, responding to what you do, and can repair itself when damaged.
It is hard because of calcium phosphate and slightly flexible because of the protein collagen.

Diet

Diet plenty of calcium and vitamin D in a balanced diet is needed to grow healthy bone.

Part 2 of 4Functions of the skeleton

Functions of the skeleton

Support

Support it supports the weight of the body against gravity, is the framework to which muscles are attached and holds internal organs in place.
The vertebral column (backbone) is made of many small bones called vertebrae and holds the body upright.

Protection

Protection hard, strong bones protect vital organs.
The skull protects the brain, and bony eye sockets protect the eyes.
The ribs protect the heart and lungs and move during breathing.
The backbone protects the spinal cord, the large bundle of nerves carrying messages to and from the brain.
The pelvis supports the lower body and protects organs in the abdomen.

Movement

Movement individual bones are hard but the skeleton is not rigid, with joints wherever two bones meet,
- and muscles pulling on bones move them at joints.

Making blood cells

Making blood cells some bones have a space filled with soft bone marrow.
Bone marrow makes red blood cells, which carry oxygen, and white blood cells, which protect against infection.
The long bones of the arms and legs contain a lot of marrow.

Mineral store

Mineral store bones store calcium and phosphate.

Part 3 of 4Structure of a long bone

Structure of a long bone

Compact bone

Compact bone strong, rigid bone on the outside.

Spongy bone

Spongy bone it is on the inside so the bone is not too heavy.

Marrow

Marrow soft tissue in the central space.

Part 4 of 4Joints

Joint

Joint a structure where two or more bones meet, giving flexibility and movement.

Fixed joints

Fixed joints such as those between the bones of the skull, which allow no movement.

Synovial joints

Synovial joints they allow free movement and have several parts:
cartilage covers the bone ends, reducing friction and absorbing shock;
synovial fluid lubricates the joint so bones slide easily, made by the synovial membrane;
ligaments join bone to bone, hold the joint together and stop it dislocating;
tendons join muscle to bone and transmit the muscle's pull.

Joint type	Movement	Example
Ball and socket	Rotation and movement in all directions	Shoulder, hip
Hinge	Back and forth in one plane only	Elbow, knee

Comparison

Comparison the shoulder has a greater range of movement than the elbow, but a hinge joint is more stable.

Levers

Levers the skeleton works as a system of levers, with muscles supplying the force, the joint the pivot and the bone the lever.

Key terms

Term	Meaning
Skeleton	All the bones of the body together.
Joint	A place where two or more bones meet.
Ligament	Strong, slightly stretchy tissue that connects bone to bone.
Tendon	Tough tissue that connects muscle to bone and does not stretch.
Cartilage	Smooth, rubbery tissue that covers bone ends and reduces friction.
Synovial fluid	Liquid in a joint that acts as a lubricant.
Bone marrow	Soft tissue inside some bones that makes blood cells.

Avoid these mistakes

Confusing ligaments and tendons — ligaments join bone to bone and tendons join muscle to bone.

Saying bones are dead and non-living — bone is living tissue with blood vessels and cells.

Saying a hinge joint allows rotation — it allows movement in one plane only.

Thinking the skeleton only gives support — it also protects organs, makes blood cells and stores minerals.

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Last updated: 13 October 2026