- A long bone in the arm or forelimb that runs from the shoulder to the elbow;
- Connects the scapula and the lower arm bones; the radius and ulna.
- The bone of the forearm that extends from the side of the elbow to the thumb side of the wrist;
- Exceeds the ulna in length and size.
3. Ulna (elbow bone):
- Placed at the middle side of the forearm, parallel with the radius;
- Articulates the humerus, at the right side elbow as a hinge joint.
4. Scapula (shoulder bone):
- The bone that connects the humerus (arm bone) with the clavicle (collar bone);
- Forms part of the shoulder girdle.
5. Functions of the skeleton:
- I. Support:
- Holds the body off the ground;
- Keeps its shape even when muscles are contracting to produce movement.
- II. Protection:
- The Brain is protected by the skull;
- The Vertebrae protect the spinal cord;
- The ribs and breastbone (sternum) protect the lungs and heart;
- The pelvis shields the reproductive organs.
- III. Movement:
- The skeleton works with muscles which are attached to it to produce movements and many bones of the skeleton act as levers.
- IV. Production of blood cells:
- Red and white blood cells are made inside certain bones.
- A location at which two or more bones make contact;
- Constructed to allow movement and mechanical support.
2. The joints may be:
- Fixed joint (fused joint);
- Movable joint (synovial joint).
3. Fixed joint:
- A joint between bones that do not move;
- e.g. skull.
4. Two important types of movable joint:
- Hinge joint;
- Ball and socket joint.
5. Hinge joint:
- Allows bones to move back and forth;
- Found in the elbow and the knee;
- Allow bones to move like a hinge in a door.
6. Ball-and-socket joint:
- Found in the hip-hone and the shoulder;
- Allows the most movement of all the joints;
- e.g. one bone (like the femur) has a ball-like knob at the end of it, and the knob fits into a cup-like space on the other side.
- Fibrous tissues that connects bones to other bones;
- Keep the bones together but do not stop their various movements.
8. Tendons and ligaments:
- Consist of tough collagen fibres – makes the flexible but very strong and resistant to stretching.
9. The type of cartilage covering the surfaces of bones in a joint is firm but softer than bone. It contains fibres but no mineral salts. It forms a smooth, slippery surface.
10. Functions of the cartilage:
- As a shock absorber;
- Reduce friction;
- Make bone flexible.
13.3 Antagonistic muscles
1. Antagonistic muscles:
- Are limb muscles which are usually arranged in pairs having opposite effects;
- When one of the pair of the muscle (biceps) contract, it has to be pulled by other muscles (triceps) which work in the opposite direction to get back into their elongated shape in order to relax.