Functions of Blood System

Transport: to and from tissue cells

• Nutrients to tissue cells: amino acids, glucose, vitamins, minerals in solution in the plasma; lipids as lipoproteins.
• Oxygen: by red blood corpuscles.
• Wastes: urea, uric acid and some CO₂ in solution in the plasma. Most CO₂ is carried in the red blood corpuscles.

Temperature Regulation: by altering the blood flow through the skin.

Immunity: protection against pathogens — blood clotting; phagocytes, lymphocytes and antibodies distributed in blood.

Communication: hormones distributed to all parts of the body in the blood.

Composition of Blood

Plasma: pale yellow sticky liquid; 55% of blood volume.

Components: water 92%, dissolved protein 8%, glucose, amino acids, vitamins, minerals, urea, uric acid, CO₂, hormones, antibodies.

Suspended Solids

Textbook Diagram: structure of suspended solids of blood.

Red Blood Cells

• Tiny biconcave disc-shaped cells.
• Do not have a nucleus.
• Do not have mitochondria.
• Their cytoplasm is rich in haemoglobin.
• O₂ binds to the iron in haemoglobin.
• Made in the bone marrow.
• Survive for about four months.
• Destroyed and recycled by the liver and spleen.

White Blood Cells (leucocytes)

• These are colourless cells and possess a nucleus.
• They function in defending the body against pathogens.
• Some ‘feed’ on pathogens by phagocytosis.
• Others produce antibodies, the specific defence proteins.
• Made by the bone marrow and lymphatic tissue.

Platelets

• These are tiny fragments of large bone marrow cells.
• They carry specialised blood clotting chemicals.
• The clotting chemicals are released where blood and lymph vessels are injured.
• A nucleus is not present in platelets.

Specialist White Blood Cells

Monocytes: largest white blood cells – engulf viruses, cancer cells, damaged and dead tissue cells.

T Lymphocytes (T cells) – made in the bone marrow, mature in the thymus.

• Helper T Cells: stimulate the multiplication of other lymphocytes.
• Killer T Cells: inject lethal chemicals into pathogenic cells.
• Suppressor T Cells: halt the immune response when the infection has been overcome.
• Memory T Cells: give immediate future protection against the same pathogen.

B Lymphocytes (B cells): specific antibody producing cells.

Blood Grouping

ABO Blood Grouping System

Four groups. The blood group depends on the presence or absence of antigen A and antigen on the surface of red blood cells.

• Group A: antigen A only.
• Group B: antigen B only.
• Group AB: antigen A and antigen B are both present.
• Group O: antigen A is not present and antigen is not present.

Дата добавления: 2015-11-14