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- cellular components
There are three types of blood cells:
- erythrocytes (red blood cell)
- leucocytes (white blood cell)
Erythrocyte (Red blood cells)
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- Biconcave disc-shaped. Can move quickly in blood capillaries and increases the TSA/V ratio to facilitate the exchange of gases.
- Carry large amount of haemoglobin.
- Haemoglobin is responsible for the transport of oxygen in the form of oxyhaemoglobin and carbon dioxide in the form of carbaminohaemoglobin.
- No nucleus when matured. This enables it to contain more haemoglobin to carry more oxygen.
- Produced in the bone marrow.
- Life span about 120 days. After that they are destroyed in the spleen and liver.
- Has no fixed shape.
- Less than the erythrocytes, but bigger in size.
- Has a nucleus
- The function is to protect the body from diseases.
- There are two types of leucocytes:
- With granules in the cytoplasm.
- With lobed nucleus.
- Formed in red bone marrow.
- There are three types of granulocytes
- neutrophil (carry out phagocytosis to engulf invading bacteria)
- eosinophil (involve in regulating the allergic responses)
- basophil (produce heparin to prevent the blood clotting）
- Have no granules in the cytoplasm.
- There are two types of agranulocytes:
- lymphocytes (responsible for producing antibodies to protect the body against diseases.)
- monocytes (carry out phagocytosis to engulf invading bacteria)
- Platelets, or thrombocytes , are cell fragments (i.e. cells that do not have a nucleus) of larger cells in the bone marrow called megacaryocytes.
- The average lifespan of a platelet is normally just 5 to 9 days.
- Platelets circulate in the blood of mammals and are involved in hemostasis, leading to the formation of blood clots.
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- Plasma is the liquid part of the blood.
- Plasma is a pale yellowish liquid consisting of water, plasma protein and other dissolved substances.
- Plasma without plasma protein is called blood serum.
- The plasma protein consist of
- immunoglobulins and
- The albumin controls osmitic pressure of blood and acts as buffer against pH changes.
- Immunoglobulins are antibodies involve in body’s defense mechanism.
- Fibrinogen is a substance important in blood clotting.
Water and Dissolved Substances
- Other than plasma protein, the dissolved substances in plasma include
- products of digestion
- excretory products
- dissolved gases such as carbon dioxide, oxygen and nitrogen.