8.1.28 · Transport in Mammals

The Main Blood Vessels — Cambridge AS & A Level Biology 9700 Revision Notes & Topical Questions

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📚 Cambridge AS & A Level Biology 9700 Hub / Topical Revision

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8.1.2 The Main Blood Vessels — CAMBRIDGE AS & A LEVEL BIOLOGY 9700 — REVISION NOTES notes: Name the major blood vessels associated with the mammalian heart, lungs, liver and kidneys and state what each one carries.

Pulmonary circulation
Systemic circulation
Oxygen diffusion
Coronary arteries
Renal artery
Renal vein

Part 1 of 8Pulmonary and systemic circulation

Pulmonary and systemic circulation

Pulmonary circulation

Pulmonary circulation it transports deoxygenated blood to the lungs for gas exchange.

Systemic circulation

Systemic circulation it transports oxygenated blood to the rest of the body.

Oxygen diffusion

Oxygen diffusion it relies on the gradient between alveolar air and blood,
- and between red blood cells and respiring tissues.
  - (net diffusion into the mitochondria of cells)
- (net diffusion into red blood cells)

Part 2 of 8Vessels of the heart and lungs

Vessel	From	To	Blood
Vena cava (superior and inferior)	Body	Right atrium	Deoxygenated
Pulmonary artery	Right ventricle	Lungs	Deoxygenated
Pulmonary vein	Lungs	Left atrium	Oxygenated
Aorta	Left ventricle	Body	Oxygenated
Coronary arteries	Aorta, just above the valve	Cardiac muscle	Oxygenated

Coronary arteries

Coronary arteries heart muscle has its own blood supply because blood passing through the chambers cannot supply the thick walls with enough oxygen quickly enough.

Blockage

Blockage atheroma or a blood clot in a coronary artery deprives heart muscle of oxygen and causes a myocardial infarction (heart attack).

Part 3 of 8Vessels of the kidney

Renal artery

Renal artery carries oxygenated blood from the aorta into each kidney, with a high concentration of urea.

Renal vein

Renal vein carries blood from the kidney to the inferior vena cava, with less urea, less salt, variable water and slightly less oxygen than the renal artery.

Part 4 of 8Vessels of the liver

Hepatic artery

Hepatic artery carries oxygenated blood from the aorta to the liver cells.

Hepatic portal vein

Hepatic portal vein carries deoxygenated blood rich in absorbed digestive products from the small intestine to the liver,
- and is a portal vein because it begins and ends in capillaries.

Hepatic vein

Hepatic vein carries blood from the liver to the inferior vena cava.

Two capillary beds

Two capillary beds blood from the intestine passes through the villi and then the liver,
- so the liver processes nutrients and toxins before they reach the body.

Part 5 of 8Blood supply to organs in parallel

Blood supply to organs in parallel

Arrangement

Arrangement the aorta gives arteries that branch to the head, arms, digestive system, kidneys and legs,
so each organ receives fully oxygenated blood at high pressure directly from the aorta.

Control

Control muscles in the artery walls control the supply to each organ independently.

Liver exception

Liver exception it receives blood from two sources, the hepatic artery (oxygenated) and the hepatic portal vein (nutrient-rich).

Digestive system

Digestive system a mesenteric artery supplies the intestines.

Part 6 of 8Changes in blood composition across organs

Organ	Increases in the vein	Decreases in the vein
Lungs	Oxygen	Carbon dioxide
Active muscle	Carbon dioxide, lactate, heat	Oxygen, glucose
Kidney	Nothing in particular	Urea, excess salts and water
Small intestine	Glucose, amino acids (after a meal)	Oxygen
Liver	Urea, glucose (if blood sugar low)	Amino acids, glucose (after a meal)

Portal vein and hepatic vein
- after a meal the hepatic portal vein has high glucose, whereas hepatic vein glucose stays near normal because the liver regulates it.

Part 7 of 8Naming vessels and tracing routes

1Rule

Rule arteries carry blood away from the heart and veins carry blood towards it, regardless of oxygen content.

2Naming

Naming name a vessel by where it connects, for example the vessel from the left ventricle is the aorta and the vessel to the left atrium is the pulmonary vein.

3Route from the small intestine

Route from the small intestine hepatic portal vein, liver, hepatic vein, vena cava, right atrium, right ventricle, then lungs.

4Route of oxygen to an organ

Route of oxygen to an organ alveolus, capillary, pulmonary vein, left atrium, left ventricle, aorta, then the artery to that organ.

Part 8 of 8More from the specification

Structural Adaptations of Arteries

Arteries have a thick tunica media composed of smooth muscle and elastic fibers, surrounded by an outer tunica adventitia of collagen, with a relatively narrow lumen that sustains high blood pressure and damps systolic pulses.

Veins and Prevention of Backflow

Veins have a wider lumen and thinner walls containing less smooth muscle and elastic tissue than arteries, operating under low pressure and utilizing semilunar pocket valves to ensure unidirectional flow back to the heart.

Capillary Permeability and Tissue Fluid Formation

Capillaries are microscopic vessels composed of a single layer of squamous endothelium,
allowing blood plasma and dissolved substances to filter through fenestrations under hydrostatic pressure to form tissue fluid.

Elastic Recoil in Arterial Blood Pressure Maintenance

During ventricular diastole, elastic fibers within artery walls recoil, maintaining blood pressure and ensuring continuous forward movement of blood throughout the vascular circuit.

Structural Adaptations of Arteries

Arteries have a thick tunica media composed of smooth muscle and elastic fibers, surrounded by an outer tunica adventitia of collagen, with a relatively narrow lumen that sustains high blood pressure and damps systolic pulses.

Veins and Prevention of Backflow

Veins have a wider lumen and thinner walls containing less smooth muscle and elastic tissue than arteries, operating under low pressure and utilizing semilunar pocket valves to ensure unidirectional flow back to the heart.

Capillary Permeability and Tissue Fluid Formation

Capillaries are microscopic vessels composed of a single layer of squamous endothelium,
allowing blood plasma and dissolved substances to filter through fenestrations under hydrostatic pressure to form tissue fluid.

Elastic Recoil in Arterial Blood Pressure Maintenance

During ventricular diastole, elastic fibers within artery walls recoil, maintaining blood pressure and ensuring continuous forward movement of blood throughout the vascular circuit.

Collagen

A protein in skin, gums and bones that needs vitamin C to form.

Plasma

The liquid part of blood.

Tissue fluid

Plasma that has leaked out of capillaries and surrounds the cells.

Smooth muscle

Involuntary muscle that narrows or widens airways.

Tunica media

The middle layer of the wall of a blood vessel containing muscle and elastic fibres.

Hydrostatic pressure

The pressure a fluid exerts on the walls of its container.

Water potential

A measure of the tendency of water to move; pure water has the highest.

Key terms

Term	Meaning
Aorta	The main artery carrying oxygenated blood from the left ventricle.
Vena cava	The large vein returning deoxygenated blood to the right atrium.
Pulmonary artery	Vessel carrying deoxygenated blood from the right ventricle to the lungs.
Pulmonary vein	Vessel carrying oxygenated blood from the lungs to the left atrium.
Coronary artery	An artery supplying the heart muscle.
Renal vein	Vessel carrying blood away from the kidney.
Hepatic portal vein	Vein carrying blood from the intestine to the liver.

Avoid these mistakes

Defining arteries as vessels carrying oxygenated blood.

Saying the pulmonary vein carries deoxygenated blood.

Confusing the hepatic artery and the hepatic portal vein.

Forgetting that the coronary arteries supply the heart muscle itself.

Saying the renal vein carries blood to the kidney.

Last updated: 15 October 2026