3.0     INTRODUCTION TO TRANSPORT SYSTEM

Transport systems in living organisms are essential for moving substances throughout the body, ensuring that cells receive the necessary nutrients, gases, and signals while removing waste products.

Transport systems deliver oxygen, nutrients, and hormones to cells and remove carbon dioxide and metabolic waste, maintaining the body’s internal balance (homeostasis).

In animals, the circulatory system performs this role. It includes the heart, blood, and blood vessels, which work together to pump and distribute blood.

Plants use a vascular system comprised of xylem and phloem. Xylem carries water and minerals from roots to other parts, while phloem distributes sugars and nutrients produced through photosynthesis.

An efficient transport system is crucial for growth, energy production, and the overall health and functioning of an organism.

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          3.1     COMPONENTS OF THE CIRCULATORY SYSTEM

• Heart – The muscular organ that pumps blood.
• Blood Vessels
• Arteries – Carry oxygenated blood away from the heart (except pulmonary arteries).
• Veins – Carry deoxygenated blood back to the heart (except pulmonary veins).
• Capillaries – Microscopic vessels where exchange of gases and nutrients occurs.
• Blood – The fluid that transports substances; consists of plasma, red blood cells, white blood cells, and platelets.

TYPES OF BLOOD CELLS

• Red Blood Cells (Erythrocytes)
• Transport oxygen to tissues and carbon dioxide to lungs.
• Biconcave shape.
• No nucleus, contains haemoglobin.
• Its Lifespan is about 120 days.
• White Blood Cells (Leucocytes)
• Defend against infections and foreign invaders.e.g:
•  Phagocytes – Fight infections.
•  Lymphocytes – B cells (antibodies) and T cells (destroy infected cells) produce antibodies, their lifespan varies from days to years.
• Platelets (Thrombocytes)
• Blood clotting to prevent bleeding.
• Small cell fragments.
• No nucleus.
• Its lifespan is about 7-10 days.

          3.2    STRUCTURE OF THE HEART

• Atrium – Two upper chambers (right atrium and left atrium) that receive blood.
• Ventricles – Two lower chambers (right ventricle and left ventricle) that pump blood out of the heart.
• Tricuspid Valve – Between the right atrium and right ventricle.
• Mitral (Bicuspid) Valve – Between the left atrium and left ventricle.
• Pulmonary Valve – Between the right ventricle and pulmonary artery.
• Aortic Valve – Between the left ventricle and aorta.
• Myocardium – Thick muscular layer responsible for contraction.
• Endocardium – Inner lining of the heart chambers.
• Pericardium – Protective sac surrounding the heart.

          3.3      PHASES OF HEARTBEAT

• Systole – Contraction phase where the heart pumps blood out.
• Diastole – Relaxation phase where the heart fills with blood.

          3.4      TYPES OF CIRCULATORY SYSTEMS

• Open Circulatory System – Found in insects; blood is not always contained within vessels.
• Closed Circulatory System  – Found in vertebrates; blood is contained within vessels.

          3.5     TRANSPORT MECHANISMS

• Diffusion – Movement of molecules from an area of higher concentration to an area of lower concentration.
• Active Transport – Movement of substances against their concentration gradient, requiring energy (ATP).
• Osmosis – Diffusion of water across a selectively permeable membrane.
• Turgidity – Turgidity is the state of a plant cell when it is swollen and firm due to the uptake of water, resulting in high turgor pressure against the cell wall.
• Haemolysis – Haemolysis is the rupture or destruction of red blood cells (erythrocytes) due to the movement of water into the cells in a hypotonic solution.
• Plasmolysis – Plasmolysis is the process in which plant cells lose water in a hypertonic solution, causing the cell membrane to pull away from the cell wall.
• Flaccidity – Flaccidity refers to the state of a plant cell when it is not turgid, meaning it has lost some water and the cell is limp.

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          3.6     TRANSPORT IN PLANTS

FUNCTION – Transports water, mineralsand nutrients from the soil to various parts of the plant.

COMPONENTS – Xylem and Phloem;

• Xylem – Vessels that transport water and dissolved minerals from roots to leaves.
• Phloem – Vessels that transport organic nutrients (sugars) from leaves to other parts of the plant.

          3.7     MECHANISMS OF TRANSPORT

• Transpiration – The process of water vapour loss from the leaves, creating a negative pressure that pulls water up through the xylem.
• Root Pressure – The pressure generated in the roots due to the accumulation of water, aiding in upward transport.
• Photosynthesis – Produces sugars in the leaves, which are then transported through the phloem to other parts of the plant.
• Translocation – The process of moving sugars through the phloem, which can occur in any direction depending on the plant’s needs.

           3.8     IMPORTANCE OF THE TRANSPORT SYSTEM

• Maintains homeostasis by regulating the internal environment.
• Facilitates the distribution of nutrients and removal of waste products.
• Supports growth and development by ensuring that all parts of the organism receive necessary substances.