Circulation
Large vein which returns blood from the upper body to the right
atrium of the heart.
superior vena cava
The main blood vessel leaving the heart and carrying oxygenated
blood to the tissues of the body.
aorta
A very small artery (less than 0.3mm in diameter).
arteriole
Thick-walled blood vessel that carries blood away from heart rapidly
at high pressure. Blood flows in pulses. They have no valves. They
have a small lumen and a three-layered wall:
 outer layer: non-elastic fibres – collagen
 middle layer: elastic fibres and muscles (thick layer)
 inner layer: endothelium – one cell thick.
artery
Relaxation of the atria, during which the chambers (atria or auricles)
fill up with blood. This occurs in the heart during the cardiac cycle.
atrial diastole
Contraction of the atria, during which the chambers (atria or
auricles) discharge the blood. This occurs in the heart during the
cardiac cycle.
Fatty substance synthesised in the liver from certain animal fats.
High levels of this substance are associated with thickening of blood
vessels (arteriosclerosis) and may lead to a heart attack or stroke.
Involved in hardening of the arteries.
atrial systole
cholesterol
Refers to a transport system that confines the blood to or maintains
it in a collection of tubules.
closed circulation
A hollow muscular organ that contracts rhythmically to pump blood
around the body
heart
Pulsation of heart, controlled by pacemaker (found in wall of right
atrium).
heartbeat
The sequence of events that produce one heartbeat.
1. Tricuspid and bicuspid valves closed so both atria fill. When atria
are full, blood flow to heart stops.
2. The atria contract (atrial systole) and force blood into ventricles.
3. Then ventricles contract (ventricular systole) and atria relax
(atrial diastole) forcing blood out the pulmonary artery and
aorta, and closing the tricuspid and bicuspid valves with a lub
sound.
4. Ventricles relax (ventricular diastole) closing the semi-lunar
valves with a dub sound.
cardiac cycle
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Number of times the heart beats per minute.
Heart/pulse rate
Blood vessel carrying blood from the heart (aorta) to the liver.
hepatic artery
Large vein that drains the digestive system and carries blood
containing absorbed food (glucose, amino acids, minerals and
vitamins) from the villi of the small intestine to the liver.
hepatic portal vein
Blood vessel carrying blood from the liver towards the heart (vena
cava).
hepatic vein
Large vein which returns blood from the lower body to the right
atrium of the heart.
inferior vena cava
A passageway or cavity within a tube, tubule or cell.
lumen
Refers to a transport system that does not confine the blood to a
collection of tubules, e.g. insects. The blood leaves the tubules and
flows among the body cells.
open circulation
A circulatory system in which capillaries drain into a vein that opens
into another capillary network, i.e. it begins and ends in capillaries.
portal blood
system
Blood vessel that brings blood from the heart to the lungs. It is the
only artery to carry deoxygenated blood.
pulmonary artery
The pathway of the blood from the heart to the lungs and back to
the heart again.
pulmonary
circulation
Blood vessel that brings blood to the heart from the lungs. It is the
only vein to carry oxygenated blood.
pulmonary vein
Branch of the aorta bringing blood from the heart to the kidney.
renal artery
Blood vessel bringing blood from the kidney to the inferior vena cava
renal vein
towards the heart.
Large vein which returns blood from the upper body to the right
atrium of the heart.
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superior vena cava