Blood and Plasma

Prof. K. Sivapalan

June 2013 Blood and plasma 2

Composition of the blood.

• Plasma:– Serum + fibrinogen.

• Cells– Red blood cells

(erythrocytes)– White blood cells

(leucocytes).• Neurtophil, eosinophil,

basophil, monocyte, lymphocyte.

– Platelets.

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Physical properties.

• Color- red. [hemoglobin]• Osmolality: 290 – 300 m osmol/L.• Osmotic pressure: 5000 mm Hg. [≈7 Atm]• Colloid osmotic pressure [oncotic

pressure] : 25 mm. Hg.• Viscosity: 3 – 4 times that of water.• Specific gravity: 1.050 – 1.060.

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Functions of Blood

• Transport of,• Water.• Oxygen.• Nutrients:

• Glucose, amino acids, fatty acids, iron, calcium, etc.

• Wastes:– Urea, carbon dioxide, bilirubin, heat, acid.

• Hormones:– Water soluble, – fat soluble.

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FUNCTIONS OF BLOOD-ctd..

• Microcirculation.• Hemostasis.

– Platelets, fibrinogen and clotting factors.• Immunity.

– Antibodies, white blood cells.

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BLOOD VOLUME.

• Blood : 8 % of the body weight.• 80 ml / Kg ± 10 %• Plasma: 5 % of the body weight.•Males 5-6, females 4-5 liters.

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Control of Blood Volume.

• Circulatory mechanism• Volume receptor mechanism.• Renin - Angiotensin – Aldesterone

mechanism.• Atrial Natriuretic Peptide.

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Circulatory Mechanism

• Blood volume determines cardiac output.• Cardiac output determines blood pressure.• Blood pressure determines Urine

production.• Urine production determines ECF volume

and blood volume.

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Volume Receptor Mechanism.Volume receptors in RA and IVC.

[stimulated by stretch which represents blood volume]

Post. Pituitary through Hypothalamus.

Anti Diuretic Hormone. Collecting ducts in Kidney.

Decreased blood volume.

+ [ ↑ impulses in afferents with volume]

- [ ↓secretion.]

- [Reabsorption of water ↓, ↑Urine out put ]

-

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Renin - Angiotensin – Aldesterone Mechanism.

• Renin is secreted by the Juxta Glomerular Cells in response to low sodium in tubule and low blood pressure in afferent arterioles.

• It converts angeotensinogen into angeotensin I which in turn gets converted to angeotensin II.

• Angeotensin stimulates secretion of Aldesteron.• Aldesteron stimulates sodium re-absorption in

distal tubule.• Keeps blood volume due to osmotic force.

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Atrial Natriuretic Peptide.

• Stretch of the right atrium is determined by venus return which mainly depends on blood volume.

• ANP is secreted by Right Atrium in response to stretch.

• ANP causes Sodium and water loss in urine.

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Properties of plasma.

• Straw color.• Volume - 3.5 liters.• High Viscosity.• Osmolality- 290 m Osmols/L• Specific gravity- 1.025.• Coagulability.

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Composition of PLASMA.

• Proteins- 7.5 g/100 ml. (dL)– Albumin. 4.5

g.– Globulin. 2.5

g.– Fibrinogen. 0.3 g.– [source: liver, plasma cells.]

• Electrolytes.• Nutrients.• Hormones.• Waste products.

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Functions of plasma.

• Fluid exchange.• Maintenance of pH- Buffering.• Transport of substances.• Hemostasis- Clotting.• Immunity.• Reserve of body proteins.