All terms in this list:

blood: It transports: Oxygen from the lungs all other parts of the body. -Carbon dioxide from all parts of the body to the lungs. -Nutrients from all parts of the body to the lungs. -Urea from the liver to the kidneys.

Single Circulatory System: Blood is pumped from the heart to the gas exchange system organ and then directly to the rest of the body.

Double Circulatory System: Blood is pumped from the heart to the gas exchange organ, back to the heart and then to the rest of the body.

Pulmonary Circulation: Blood is circulated through the lungs where it is oxygenated.

Systematic Circulation: Blood is circulated through all parts of the body, where it unloads its oxygen.

Blood Vessels: Carry blood around the body.

Arteries: Carry blood away from the heart and towards other organs.

Veins: Carry blood towards the heart and away from other organs.

Capillaries: Carry blood through organs.

Systole: Rhythmic contraction of a chamber of the heart.

Diastole: The relaxation and dilation of the heart chambers, between contractions, during which they fill with blood.

watch-pocket valve: Valves which prevent the backflow of blood inside veins.

Arterioles: Small arteries, similar in structure to the larger ones, but have a high proportion of muscle fibres in their walls. They carry blood into organs from arteries.

Plasma: It carries dissolved nutrients, blood cells, hormones, carbon dioxide and urea, also distributes heat around the body.

red blood cells: Biconcave disc-like cells with no nucleus. Contain haemoglobin, which loads oxygen in the lungs and unloads it in other parts of the body.

lymphocytes: Same size as red blood cells but have a large spherical nucleus. Produce antibodies to destroy microorganisms.

phagocytes: Large cell with a large spherical or lobed nucleus which engulf bacteria and other microorganisms.

platelets: Small cells which are fragments of other cells that release chemicals to make blood clot in open wounds.

erythrocytes: Red blood cells.

Surface Area to Volume ratio: It can be written as: surface area/volume

Cardiac Muscle: It moves blood by a series of contractions and relaxations of its chambers.

Heart Rate: The number of heart beats per unit of time, usually expressed as beats per minute. Normally 70 times a minute. It increases with exercise, stress, and the secretion of adrenaline. It decreases when we sleep.

Medulla: Part of the brain which controls heart rate, detecting the nerve impulses sent by the aorta and the carotid artery.

Accelerator Nerve: Increases the heart rate, causes the heart to beat with more force and increases blood pressure.

Decelerator Nerve: Decreases heart rate, reduces force of the contractions, and causes blood pressure to return to normal.

Tricuspid Valve: A heart valve with three cusps which prevents backflow of blood from the right ventricle into the right atrium.

Pulmonary Vein: Vein which returns the blood to the heart after it has circulated through the lungs.

Pulmonary Artery: The artery that connects the right ventricle of the heart to the lungs, and carries blood from the heart to the lungs.

Vena Cava: Vein that takes oxygen depleted blood away from the organs and returns it to the right atrium of the heart.

Mitral Valve: Bicuspid valve that lies between the left atrium and the left ventricle.

Aorta: The great artery which carries the blood from the heart to all parts of the body except the lungs; the main trunk of the arterial system.

Cardiac Centre: Region of the medulla that controls heart functions.