Physical Properties of Blood and Plasma
- The Average adult has a blood volume of approximately 5 liters, which composes about 8% of the body's weight.
- Osmolality of blood is 275-295 milliosmoles per kg.
- Plasma constitutes approximately 55% of blood's volume.
- Plasma Composition:
- 90% Water
- 8% Protein
- 0.9% Inorganic Salts
- Sodium 135-146 mM
- Potassium 3.5-5.2 mM
- Calcium 2.1-2.7 mM
- Carbonate 23-31 mM
- Phosphate 0.7-1.4 mM
- 1.1% organic substances
- It is estimated that plasma may contain as many as 40,000 different proteins from about 500 gene products. Approximately 1,000 proteins have been detected.
- Plasma contains 50-70 mg of protein per ml.
- Approx. 70% Albumin (35-50 mg/ml)
- Approx. 10% IgG (5-7 mg/ml)
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Blood Composition on the Cellular Level
For every 600 red blood cells, there are approximately 40 platelets and one white cell.
Red Blood Cells (Erythrocytes)
- Typically 4-8 x 106 cells per µl
- Composed approx 90% hemoglobin
- RBCs have a life-span of approx. 120 days before they are removed by the spleen
- Typically 150,000-350,000 per µl
- Produced by megakaryocytes stimulated by thrombopoietin.
- Platelets circulate for an average of 9-10 days before removal by the spleen.
- Participate in hemostasis/coagulation
White Blood Cells (Leukocytes)
– Neutrophils (polymorphonuclear leucocytes)
- Compose approximately 56% of the white blood count
- Chemotactic-directed phagocytic action in response to interleukin-1 from macrophages, histamine from basophils, mast cells and platelets and complement proteins C3a and C5a in the plasma.
- Phagocytic & Cytotoxic
- Compose approximately 4% of the white blood count.
- Bind via C3b receptors resulting from parasitic alternative pathway complement activation.
- Granules release proteins cytoxic to parasites: MBP, peroxidase, arylsulphatase B, phospholipase D and histaminase.
- Smallest granulocytes
- Compose approximately 3% of the white blood count.
- Involved in Type I hypersensitivity
- Binding of IgE to the Fc receptors on basophils stimulate release of histamine and heparin
- Upon stimulation, basophils release TNF- and IL-4, that modulate endothelial adhesion molecules.
- Basophils express integrins as receptors to the endothelial membrane proteins ICAM-1,ELAM-1and VCAM-1
- Compose approximately 25% of the white blood count
- Produced by bone marrow.
- Termed B cells when they achieve immune-competence within marrow
- Termed T cells when they achieve immune-competence within thymus
- B Cells respond to antigens by the production of antibodies, B and T cells produce lymphokines that control immune response
- Within approximately one day from being produced in the marrow, monocytes are transported to various organs where they become tissue macrophages via the influence of cytokines.
- kidney - mesangial cells
- bone - osteoclasts
- liver - Kupfer cells
brain - microglia
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