Summary
Plasma, red cells, white cells and platelets carry out transport, defence and clotting.
In depth
Plasma (55 percent) carries nutrients, hormones and CO2; red blood cells carry oxygen with haemoglobin; white blood cells defend; platelets help clotting. Red cells are biconcave with no nucleus and live about 120 days.
Blood makes up about 8 percent of body weight. Haematocrit is the red cell proportion. Blood types depend on surface antigens.
Remember: red cells have no nucleus, so can't divide.
Blood makes up about 7 to 8 percent of body weight (5 litres in adults). Haematocrit, the proportion of red cells, is about 45 percent in men and 40 percent in women. Red cells are biconcave discs without nuclei, living about 120 days, with 2 million made every second in bone marrow, stimulated by erythropoietin from the kidney. Platelets are cell fragments from megakaryocytes. Plasma contains water, albumin, globulins, fibrinogen, electrolytes, hormones and waste.
Blood tests show disease: anaemia (low haemoglobin), leukaemia (abnormal white cells), clotting disorders and infections. Blood types and Rh factor matter for transfusions. Blood transports, regulates temperature and pH, and defends. Serum is plasma without clotting factors.
Example: living at altitude increases red cell count through erythropoietin.
Frequently asked questions
What is Blood Components?
Plasma, red cells, white cells and platelets carry out transport, defence and clotting.
Which area of biology covers Blood Components, and how advanced is it?
Blood Components is one of the 51 topics in Human Physiology. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Excretory System, Haemoglobin and Oxygen Transport, Skin.
Can you give an example of Blood Components?
Anaemia is low haemoglobin.
What should I learn before Blood Components?
Blood Components is a Beginner topic, so no earlier topic is required. Other Beginner topics in Human Physiology that pair well with it include Homeostasis, Tissues and Organs, Skeletal System.
What topics are related to Blood Components?
The closest topics to Blood Components are Excretory System, Haemoglobin and Oxygen Transport, Skin, Blood Clotting. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Blood Components?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Blood Components. To practise the whole of Human Physiology, use the Human Physiology quiz.
How is Blood Components different from Excretory System?
Blood Components: Plasma, red cells, white cells and platelets carry out transport, defence and clotting. Excretory System: Kidneys, ureters, bladder and urethra remove metabolic waste and balance water. Read both side by side and note what each one explains.
How should I study Blood Components step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Excretory System and explain the difference aloud. Finally, take the Human Physiology quiz and come back to this page for any question you miss.