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Cambridge IGCSE Biology · 0610

Chapter 9: Transport in animals (Part 2)

Coronary heart disease (CHD)

Cause
A buildup of cholesterol in the coronary artery which narrows and eventually blocks it, limiting blood flow to the heart.
Risk factors
  • Diet: Too much saturated fat increases cholesterol.
  • Lack of exercise: Increases the risk of high blood pressure.
  • Other factors: Stress, smoking, genetic predisposition, age, and gender.
Prevention
Eating a healthy diet and engaging in regular exercise to lower blood pressure.

Adaptations of blood vessels

  1. Arteries: Carry blood away from the heart at high pressure.
    • Structure: Small lumen, thick elastic layer, and thick muscle layer to maintain pressure and control blood volume by dilating and constricting.
  2. Veins: Carry blood back to the heart at low pressure.
    • Structure: Larger lumen, thin elastic and muscle layers, and contain valves to prevent backflow.
  3. Capillaries: Tiny vessels used for exchange of substances (oxygen, CO2, nutrients) with tissues.
    • Structure: Branched for a large surface area, narrow lumen to decrease diffusion distance, and a slow rate of blood flow to allow time for exchange.
Transverse sections of an artery, vein, and capillary comparing wall thickness and lumen size
Diagram 1: Comparison of blood vessel structures. Transverse sections of an artery, a vein, and a capillary show differences in wall thickness and lumen size. The muscle/elastic layers are labelled and the valve in the vein is indicated.

Exam Traps

  • Do not say veins have thicker muscular walls than arteries — arteries need more muscle and elastic tissue.
  • Avoid claiming capillaries have valves or a wide lumen for rapid blood flow.

Major blood vessels of the body

You must be able to identify the vessels connecting the heart to important organs:

Heart
Vena cava (vein in), aorta (artery out).
Lungs
Pulmonary artery (to lungs), pulmonary vein (from lungs).
Liver
Hepatic artery (to liver), hepatic veins (from liver), and the hepatic portal vein (from the digestive system to the liver).
Kidney
Renal artery (to kidney), renal vein (from kidney).

Exam Traps

  • Do not confuse hepatic portal vein (gut to liver) with hepatic vein (liver to vena cava).

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