Mass Transport: Heart & Blood — A-Level Biology Revision

Topic has curated content entry with explanation, mistakes, and worked example. [auto-gate:promote; score=75.25]

What is Mass Transport: Heart & Blood?

Mass transport is the movement of substances over long distances in multicellular organisms, via a transport system. In mammals, the circulatory system, consisting of the heart, blood vessels, and blood, is responsible for transporting oxygen, nutrients, hormones, and waste products. The double circulatory system ensures that blood is pumped to the lungs to be oxygenated before being circulated to the rest of the body.

Board notes: The structure and function of the heart, blood vessels, and the process of blood clotting are covered by all A-Level Biology boards (AQA, Edexcel, OCR). The interpretation of ECGs (electrocardiograms) and the formation of tissue fluid are also key areas, with some variation in the level of detail required.

Worked example

Common mistakes

• 1Confusing the roles of arteries, veins, and capillaries. Arteries carry high-pressure blood away from the heart, have thick muscular walls, and a narrow lumen. Veins carry low-pressure blood towards the heart, have thinner walls, a wider lumen, and valves to prevent backflow. Capillaries are the site of exchange and have walls that are one cell thick.
• 2Not understanding the cardiac cycle. The cardiac cycle consists of systole (contraction) and diastole (relaxation) of the atria and ventricles. The sequence is atrial systole, ventricular systole, and then diastole of both.
• 3Forgetting the role of tissue fluid. Tissue fluid is the fluid that surrounds the cells in tissues. It is formed from blood plasma that leaks from capillaries and is where the exchange of substances between the blood and cells takes place.

Mass Transport: Heart & Blood exam questions

Exam-style questions for Mass Transport: Heart & Blood with mark-scheme style solutions and timing practice. Aligned to AQA, Edexcel and OCR specifications.

Frequently asked questions

• What is the function of the coronary arteries?

  The coronary arteries are the blood vessels that supply the heart muscle itself with oxygenated blood. Blockage of these arteries can lead to a heart attack.

• How is blood pressure measured?

  Blood pressure is measured in millimetres of mercury (mmHg) and is given as two figures: systolic pressure (the pressure when the heart beats) over diastolic pressure (the pressure when the heart rests between beats).