Unit Overview
Transport in Mammals
CIE A-Level BiologyΒ· 5 min read π n/a
1. Unit at a Glance
This unit follows a logical learning arc, starting from the transport fluid (blood) moving through the vessels that carry it, the pump that drives circulation (the heart), and ending with how the system adjusts to meet changing body demands. A core theme throughout is how structure is specifically adapted to function at every level of organization.
Below are all sub-topics included in this unit:
Blood composition
Covers plasma and formed elements (RBC, WBC, platelets) and their core functions.
β β± 3 min
Blood clotting
Explains the clotting cascade that prevents blood loss and blocks pathogen entry after injury.
β β β± 3 min
Heart structure
Explores the internal and external structure of the mammalian heart and associated blood vessels.
β β β± 4 min
Cardiac cycle
Covers the sequence of systole and diastole, pressure changes, and valve movement.
β β β β± 5 min
Blood vessels structure and function
Compares the structure and function of arteries, veins, and capillaries.
β β β± 4 min
Gas transport in blood
Explains how oxygen and carbon dioxide are transported, including the role of haemoglobin.
β β β β± 4 min
Regulation of heart rate
Covers nervous and hormonal control of heart rate in response to changing activity levels.
β β β β± 4 min
2. Common Pitfalls
Wrong move:
Confusing systole and diastole when describing the cardiac cycle
Why:
This leads to incorrect conclusions about pressure changes and which valves are open/closed
Correct move:
Remember: systole = contraction, diastole = relaxation; always link chamber state to pressure
Wrong move:
Stating all carbon dioxide is carried as bicarbonate ions in blood
Why:
Students often forget the other two methods of carbon dioxide transport
Correct move:
Recall: ~70% as bicarbonate, ~23% bound to haemoglobin, ~7% dissolved in plasma
Wrong move:
Mixing up the structural adaptations of arteries and veins
Why:
Students often memorize labels instead of linking structure to function
Correct move:
Arteries have thick elastic/muscle walls to withstand high pressure; veins have valves to prevent backflow
3. Quick Reference Cheatsheet
Key Concept | Unit-Level Summary |
|---|---|
Blood composition | 55% plasma, 45% formed elements (erythrocytes, leukocytes, platelets) |
Clotting cascade | Thromboplastin β prothrombin β thrombin β fibrinogen β fibrin mesh clot |
Heart structure | Right side pumps deoxygenated blood to lungs; left side pumps oxygenated blood to the body |
Cardiac cycle order | Atrial systole β Ventricular systole β Complete diastole |
Vessel structure comparison | Arteries: thick elastic/muscle; Capillaries: 1-cell thick endothelium; Veins: valves, thin walls |
Oxygen-haemoglobin binding | |
Heart rate regulation | Medulla oblongata: sympathetic = increase rate, parasympathetic = decrease rate |
What's Next
Begin your study of this unit by opening the first sub-topic on blood composition to get started. Once you complete all sub-topics in this unit, you will move on to the next unit covering transport in plants, which explores similar core themes of exchange and bulk transport in multicellular organisms.