#48 Summary of The mammalian heart

 1 The human heart, like that of all mammals, has two atria and two ventricles. Blood enters the heart by the atria and leaves from the ventricles. A septum separates the right side of the heart, which contains deoxygenated blood, from the left side, which contains oxygenated blood.

 2 Semilunar valves at the entrances to the blood vessels that leave the heart (aorta and pulmonary
artery) prevent back flow of blood into the heart, and atrioventricular valves prevent backflow of blood from ventricles into the atria.

#47 Summary of The mammalian transport system

 1. Blood is carried away from the heart in arteries, passes through tissues in capillaries, and is returned to the heart in veins. Blood pressure drops gradually as it passes along this system.

2. Arteries have thick, elastic walls, to allow them to withstand high blood pressures and to smooth out the pulsed blood flow. Capillaries are only just wide enough to allow the passage of red blood cells, and have very thin walls to allow effi cient and rapid transfer of materials between blood and cells. Veins have thinner walls than arteries and possess valves to help blood at low pressure flow back to the heart.

#46 The Heart

The mammalian heart is a double pump:

 - The right side pumps deoxygenated blood at low pressure to the lungs.

 - The oxygenated blood then returns to the left side of the heart in the pulmonary vein.

- The left side pumps oxygenated blood at high pressure to the rest  of the body in the aorta.

- The blood then returns to the right side of the heart in the vena cava to start the cycle again.

#45 The components of blood, O2 and CO2 transport

The body contains approximately 5 litres of blood and this is a mixture made up of red blood cells, white blood cells and platelets all suspended in a liquid called plasma.

# 44 The circulatory system - blood vessels

The mammalian circulatory system is a closed double circulation, consisting of a heart, blood vessels and blood.

The heart produces high pressure --> blood moves through the vessels by mass flow.

#43.2 Transport in mammals - Syllabus 2016 - 2018

8.1    The circulatory system
8.2    The heart

#43.1 Transport in mammals - Syllabus 2015

• The need for, and functioning of, a transport system in mammals
• Structure and functioning of the mammalian heart