The function of the cardiovascular system is to transport oxygen and nutrients around the body to the cells that need it. At the same time it also removes carbon dioxide and other waste products from the body.
Components of Blood
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.
Components of Blood
The table below provides more details on each of the separate components of blood.
Red Blood Cells (Erythrocytes)
Make up 40-50% of the total blood volume
Made in the bone marrow
Function
Carry oxygen from lungs to all cells of the body
Carry carbon dioxide away from cells
Properties
Contain oxygen carrying molecule called haemoglobin which combines with oxygen to give oxyhaemoglobin.
Haemoglobin + Oxygen => Oxyhaemoglobin
Haemoglobin also responsible for the red colour of blood
Biconcave shape providing a large surface area to volume ratio to absorb the maximum amount of oxygen.
Have no nucleus, therefore more surface area to carry haemoglobin and hence oxygen
Small and flexible so can pass easily through blood vessels
White Blood Cells (Leukocytes)
Make up 1% of the blood volume
Made in the bone marrow
Form part of the immune system
Two main types: Lymphocytes and Phagocytes
Function
Defend the body against infection and disease
Lypmhocytes: Recognise virus or bacteria as being foreign and make antibodies to attack and destroy them
Phagocytes: Destroy virus and bacteria by engulfing them in a process known as phagocytosis. They take the germ into the cell then digest and destroy it.
Properties
Have a large nucleus
Larger than red blood cells
Shape varies depending on which type of cell
Have a flexible shape so that they can engulf microorganisms
Platelets (Thrombocytes)
Fragments of larger cells
Made in the bone marrow
Function
Help blood to clot by clumping together and forming a plug. (Therefore you do not bleed to death if you cut yourself).
Protect the body by stopping bleeding
Properties
No nucleus
Plasma
Makes up 55% of the blood volume
Function
Transports dissolved substances e.g. Carbon dioxide, glucose, salts, urea, hormones, antibodies, plasma proteins around the body
Brings nourishment to cells and removes waste products
Prevents blood vessels from collapsing
Properties
Yellow liquid part of the blood in which red and white blood cells as well as platelets are suspended
95% of it consists of water with many substances dissolved in it
Arteries, Veins and Capillaries
The next major components of the cardiovascular system are the blood vessels. These are a network of tubes that transport the blood around the body. There are three types of blood vessels which all carry out different functions:
Arteries carry blood away from the heart and veins carry blood back to the heart. When an artery reaches an organ it branches out into capillaries. It is in the capillaries where substances such as oxygen, food and carbon dioxide are exchanged between the blood and organ cells. The capillaries then join up to form veins. Capillaries are the links between arteries and veins
