Year 9 Bio

1. Circulatory System

  • Function: Transports oxygen, nutrients, and waste throughout the body.

  • Main Components:

    • Heart: Pumps blood around the body.

    • Blood Vessels:

      • Arteries: Carry oxygenated blood away from the heart (except pulmonary artery).

      • Veins: Carry deoxygenated blood back to the heart (except pulmonary vein).

      • Capillaries: Tiny blood vessels where exchange of gases and nutrients happens.

    • Blood:

      • Red Blood Cells: Carry oxygen using hemoglobin.

      • White Blood Cells: Fight infections.

      • Platelets: Help in clotting.

      • Plasma: Liquid part of blood carrying nutrients, hormones, and waste.

2. Respiratory System

  • Function: Supplies oxygen to the body and removes carbon dioxide.

  • Main Components:

    • Nose & Mouth: Air entry.

    • Trachea: Windpipe leading to lungs.

    • Bronchi & Bronchioles: Airways that lead to alveoli.

    • Alveoli: Tiny air sacs for gas exchange (oxygen in, CO₂ out).

  • Breathing Process:

    • Inhalation: Diaphragm contracts, lungs expand, air enters.

    • Exhalation: Diaphragm relaxes, lungs deflate, air is expelled.

3. Digestive System

  • Function: Breaks down food into nutrients the body can absorb.

  • Main Components:

    • Mouth: Chewing and saliva start digestion.

    • Esophagus: Transports food to stomach.

    • Stomach: Acid and enzymes break down food.

    • Small Intestine: Nutrients absorbed into blood.

    • Large Intestine: Water absorbed; waste forms.

    • Liver: Produces bile for fat digestion.

    • Pancreas: Produces digestive enzymes.

4. Nervous System

  • Function: Sends and receives signals throughout the body.

  • Main Components:

    • Brain: Controls body functions.

    • Spinal Cord: Sends signals between brain and body.

    • Nerves: Carry electrical signals.

  • Types of Responses:

    • Voluntary: Actions you control (e.g., moving your hand).

    • Reflexes: Fast, automatic responses (e.g., pulling hand from a hot surface).