1. Components of the blood
Circulatory system
Components of the blood
Blood accounts for about 8% of our total body weight. Healthy males have around 5-6 litres of blood and females about 4-5 litres
Blood is a fluid tissue and performs a number of important specialised functions.
Transports nutrients, oxygen, carbon dioxide, waster products and hormones to cells and organs around the body
Protects us from bleeding to death via clotting and protects us from disease and toxic substances
Acts as a regulator of temperature and the water content in cells.
The material between the cells of the blood is called plasma which makes up about 55% of the blood volume. Of that 55% (90% water, 10% dissolved substances), The other 45% of cellular component contains red cells (Erythrocytes), white cells (Leucocytes) and platelets (Thrombocytes).
Red blood cells carry the protein haemoglobin, which gives blood its colour and can combine with oxygen, which enables the blood to carry oxygen from the lungs to the tissues.
White blood cells protect the body against bacteria.
Platelets are tiny cell fragments which aid in the clotting of blood in the event of a cut or injury.

2. In one day pumps 12000 litres of blood
Circulatory system
Structure and function of the heart, arteries, veins and capillaries.
Atria: the upper thin-walled chambers that receive blood coming back to the heart
Ventricles: the lower, thick-walled chambers that pump blood from the heart to the body.
Beats 70 times per minute at rest
In one day pumps litres of blood

3. circulatory system Action of the heart
The heart is able to receive and pump blood through a process called the cardiac cycle. The cardiac cycle consists of the:
Diastole (relaxation of filling) phase: Muscles of both atria and ventricles relax. Blood returning from lungs and body, flows in to fill both atria and ventricles in preparation for systole (contraction)
Systole (contraction or pumping) phase: The atria contracts to further fill ventricles. The ventricles then contract and push blood under pressure to the lungs and all parts of the body. As they contract, the rising pressure in the ventricles closes the atrioventricular valves (between atrium and ventricle) and opens the valves in the arteries leaving the heart (aorta and pulmonary artery).

4. circulatory system Blood Vessels
Arteries: are blood vessels that carry blood away from the heart
Capillaries: are the smallest blood vessels. They function to exchange oxygen and nutrients for waste.

5. circulatory system Blood Vessels
Veins: carry deoxygenated blood from the body tissues back to the right atrium. Pulmonary veins from the lungs differ in that they carry oxygenated blood to the left atrium.

6. circulatory system Pulmonary and systemic circulation
Pulmonary Circulation: is the flow of blood from the heart to the lungs and back to the heart. The right side receives venous blood that is low in oxygen content (deoxygenated) from all parts of the body and pumps it to the lungs.
Systemic circulation: is the flow of blood from the heart to the body tissue and back to the heart. The left side of the heart reives blood high in oxygen content (oxygenated) from the lungs and pumps it around the body

7. What is blood pressure?
Blood pressure is the force exerted by the blood on the walls of the arteries. It is measured at two points during the beating of the heart.
Systolic Pressure: is the highest (peak) pressure recorded when blood is forced into the arteries during contraction of the left ventricle (systole)
Diastolic Pressure: is the minimum or lowest pressure recorded when the heart is relaxing and filling (diastole)
Blood pressure is measured in millimetres of mercury by an inflatable cuff wrapped around your upper arm. This is called a Sphygmomanometer.
The “normal” blood pressure range is 120/ is the systolic pressure (contraction) and the 80 is the diastolic pressure (relaxing & filling)

8. What impacts blood pressure?
Blood pressure generally reflects the quality of blood being pushed out of the heart (cardiac output) and the ease of difficulty that blood encounters passing through arteries (resistance to flow). It can be affected by:
Cardiac output: increase in cardiac output = increase in blood pressure
Volume of blood in circulation: water retention (salt intake is high) increases BP; blood loss decreases blood pressure.
Resistance to blood flow: viscosity (stickiness) of blood increases BP as resistance increases, such as during dehydration. Narrowing of blood vessels due to fatty deposits affect blood flow.
Venous return as it impacts cardiac output, it similarly impacts blood pressure.
How to measure blood pressure?