BIOLOGY · Stage 8 · Chapter 6: Nutrition, Health and Movement
Biology 6.9 The human skeleton — Bones, Joints and Support
5 min read 4 parts Lesson 9 of 12
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
Section 1 of 4The skeleton
- Skeleton = all the bones of the body together, and humans are vertebrates built around bones of different sizes and shapes.
- Number
- the average adult has 206 bones.
- Importance
- without a skeleton a person would be like a giant jellyfish and moving would be very difficult.
- 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
- plenty of calcium and vitamin D in a balanced diet is needed to grow healthy bone.
Section 2 of 4Functions of the skeleton
- 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
- 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
- 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
- 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
- bones store calcium and phosphate.
Section 3 of 4Structure of a long bone
- Compact bone
- strong, rigid bone on the outside.
- Spongy bone
- it is on the inside so the bone is not too heavy.
- Marrow
- soft tissue in the central space.
Section 4 of 4Joints
- Joint = a structure where two or more bones meet, giving flexibility and movement.
- Fixed joints
- such as those between the bones of the skull, which allow no movement.
- 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
- the shoulder has a greater range of movement than the elbow, but a hinge joint is more stable.
- Levers
- the skeleton works as a system of levers, with muscles supplying the force, the joint the pivot and the bone the lever.
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