Biology • Year 11 • Module 2 • Lesson 14
The Cardiovascular System: Structure and Function
Lock in the four-chamber heart, valve names, the double circulatory pathway, and the structural comparison of the three vessel types.
1. Heart chambers, fill the table
Complete the table using information from the lesson. Each row describes one of the four heart chambers. 8 marks
| Chamber | Side | Blood type carried | Wall thickness | Where it pumps blood to |
|---|---|---|---|---|
| Right atrium | ||||
| Right ventricle | ||||
| Left atrium | ||||
| Left ventricle |
2. Valve identification
Match each valve name in the left column to the correct location and function description on the right. Write the letter next to the valve name. 8 marks (2 each)
| Valve name | Letter |
|---|---|
| Tricuspid valve | |
| Bicuspid (mitral) valve | |
| Pulmonary valve | |
| Aortic valve |
| Letter | Location and function |
|---|---|
| A | Between left atrium and left ventricle; prevents backflow into left atrium when the ventricle contracts. |
| B | Between left ventricle and aorta; opens when left ventricle contracts; closes to prevent back-flow into ventricle. |
| C | Between right atrium and right ventricle; prevents backflow into right atrium. |
| D | Between right ventricle and pulmonary artery; opens when right ventricle contracts. |
3. Order the circuit, one complete loop
The steps below describe a red blood cell completing one full circuit, but they are out of order. Write the numbers 1–10 in the “Order” column to show the correct sequence, starting from the right atrium. 10 marks
| Order | Step |
|---|---|
| Blood travels through the pulmonary artery to the lungs, where gas exchange occurs (O₂ loaded, CO₂ unloaded). | |
| Oxygenated blood flows through the pulmonary veins into the left atrium. | |
| Blood passes through the tricuspid valve into the right ventricle. | |
| Blood exits the left ventricle through the aortic valve into the aorta. | |
| Blood delivers O₂ and glucose to body tissues at capillaries; CO₂ and waste enter the blood. | |
| Deoxygenated blood returns via the superior and inferior vena cava to the right atrium. ← Start here | |
| Blood passes through the bicuspid (mitral) valve into the left ventricle. | |
| The right ventricle contracts, pushing blood through the pulmonary valve. | |
| Blood travels through systemic arteries, arterioles and capillaries to all body organs. | |
| Deoxygenated blood drains from capillaries into venules and systemic veins, then into the vena cava. |
4. Three vessel types, complete the comparison table
Complete the table. Write the feature that applies to each vessel type. Where a feature does not apply, write “none” or “n/a”. 12 marks
| Feature | Arteries | Capillaries | Veins |
|---|---|---|---|
| Wall thickness | |||
| Lumen size (relative to wall) | |||
| Presence of valves | |||
| Blood pressure carried | |||
| Direction of blood flow (relative to heart) | |||
| Primary function |
5. Key term definitions
Define each term in 1–2 sentences using precise biological language. 10 marks (2 each)
5.1 Double circulation
5.2 Septum
5.3 Pulmonary circuit
5.4 Systemic circuit
5.5 Capillary
Q1, Heart chambers table
Right atrium: Right side • Deoxygenated • Thin wall • Pumps to right ventricle via tricuspid valve.
Right ventricle: Right side • Deoxygenated • Thinner than left ventricle (lower pressure, ~25 mmHg) • Pumps to pulmonary artery (lungs).
Left atrium: Left side • Oxygenated • Thin wall • Pumps to left ventricle via bicuspid (mitral) valve.
Left ventricle: Left side • Oxygenated • Thick wall (~3× right ventricle, ~120 mmHg) • Pumps to aorta and entire systemic circuit.
Marking criteria: 2 marks per chamber (1 for blood type, 1 for wall thickness/destination). Total 8 marks.
Q2, Valve match
Tricuspid valve: C (right atrium to right ventricle).
Bicuspid (mitral) valve: A (left atrium to left ventricle).
Pulmonary valve: D (right ventricle to pulmonary artery).
Aortic valve: B (left ventricle to aorta).
Marking criteria: 2 marks per correct match (1 for correct letter, 1 for identifying the correct anatomical position). Award 1 mark if letter is correct but no written justification of position. Total 8 marks.
Q3, Circuit ordering
Correct sequence starting from right atrium: 6 (start: right atrium) → 3 (tricuspid → right ventricle) → 8 (right ventricle contracts, pulmonary valve) → 1 (pulmonary artery → lungs) → 2 (pulmonary veins → left atrium) → 7 (bicuspid → left ventricle) → 4 (aortic valve → aorta) → 9 (systemic arteries → capillaries) → 5 (O₂ and glucose delivered at capillaries) → 10 (venules → veins → vena cava).
Marking criteria: 1 mark per correctly placed step (all 10 steps must be in correct relative order). Accept minor variation in where steps 9 and 5 are split. Total 10 marks.
Q4, Vessel comparison table
Wall thickness: Arteries, thick (3 layers: connective tissue, smooth muscle, endothelium); Capillaries, one cell thick (endothelium only); Veins, thinner than arteries.
Lumen size: Arteries, small relative to wall; Capillaries, ~5–10 μm, RBCs single file; Veins, wide bore (large relative to wall).
Valves: Arteries, none; Capillaries, none; Veins, pocket valves throughout.
Blood pressure: Arteries, high (~120/80 mmHg); Capillaries, low; Veins, low (~5–10 mmHg).
Direction: Arteries, away from heart; Capillaries, from arterial to venous side; Veins, toward heart.
Primary function: Arteries, high-pressure delivery to organs; Capillaries, gas/nutrient/waste exchange; Veins, low-pressure return to heart.
Marking criteria: 2 marks per feature row across all three vessels (award 1 if only one or two vessels are correct for that row). Total 12 marks.
Q5, Key term definitions
5.1 Double circulation: A circulatory arrangement in which blood passes through the heart twice per complete circuit, once through the pulmonary circuit (heart to lungs and back) and once through the systemic circuit (heart to body and back). This re-pressurises blood after it loses pressure in the lung capillaries, ensuring high systemic delivery pressure.
5.2 Septum: The muscular wall dividing the left and right sides of the heart, ensuring complete separation of oxygenated and deoxygenated blood so the two circuits never mix.
5.3 Pulmonary circuit: The loop of the cardiovascular system that carries deoxygenated blood from the right ventricle via the pulmonary artery to the lungs for gas exchange, returning oxygenated blood via the pulmonary veins to the left atrium.
5.4 Systemic circuit: The loop of the cardiovascular system that carries oxygenated blood from the left ventricle via the aorta to all body tissues and organs, returning deoxygenated blood via the vena cava to the right atrium.
5.5 Capillary: A microscopic blood vessel one cell thick (endothelium only, ~0.5–1 μm), forming networks throughout body tissues. It is the only site where oxygen, nutrients and waste products are exchanged between the blood and tissue cells by diffusion, facilitated by a minimal diffusion distance.
Marking criteria: 2 marks each: 1 for an accurate core definition, 1 for linking structure to function or context. Total 10 marks.