Function and components of blood
- Blood has both cellular and fluid components
- Cellular components makes up 45% of volume
- Liquid component makes up 55%
Plasma
- Plasma if the liquid component
- Normal pH is 7.35 - 7.45
- 90% is water
- 10% is solutes
- Solutes include:
- Albumin - 60%
- Globulins - 35%
- Fibrinogen
- Thrombin
- Hormones
- Cholesterol
- Nitrogenous wastes - urea, lactic acid, creatinine
- Nutrients
- Electrolytes
Cellular elements
Erythrocytes
- Red blood cells are biconcave discs
- Approximately 7.5um in diameter
- Formed in the bone marrow
- Removed from circulation in spleen and liver
- Have no nuclei or mitochondria
- Have life span of about 120 days
- Normal red cell production requires
- Iron
- Amino acids
- Vitamins - B12 and B6
- Hormones - erythropoietin
- Reticulocytes are immature red blood cells
- Account for 1-2% of circulating red blood cells
- Red cell production is stimulated by:
- Haemorrhage
- Anaemia
- Hypoxia
- Increased oxygen requirement
Leukocytes
- White cells account for 1% of blood volume
- Have both nuclei and mitochondria
- Made up of granulocytes
- Neutrophils 40-70%
- Basophils 1%
- Eosinophils
- Other elements are
- Lymphocytes 20--40%
- Monocytes 4-8%
- Leukocytes have life span of 1-2 days
- Neutrophils are responsible for phagocytosis of bacteria
- Eosinophils are involved in defence against parasites and in immune
complex destruction
- Basophils release histamine and produce chemotactic agents
- Monocytes are the precursors of tissue macrophages
- Lymphocytes are produce in lymph nodes and spleen
- B lymphocytes produce antibodies
- T lymphocytes are involved in cell mediated immunity
- NK cells are involved in immune surveillance
Platelets
- Not true cells
- Are fragments of cells known as megakaryocytes
- Formed in bone marrow
- Have a life span of about 10 days
- Have granules that contain
- Calcium
- ADP
- Serotonin
- Platelet derived growth factor
- Have important role in blood coagulation
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