Archive for the ‘Constituents of human blood’ Category
Constituents of human blood
Cells
One microliter of blood contains:
- 4.7 to 8.1 million (male), 4.2 to 5.4 million (female) erythroctes. In mammals, mature red blood cells lack a nucleus and organelles. They contain the blood’s hemoglobin and distribute oxygen. The red blood cells (together with endothelial vessel cells and other cells) are also marked by glycoproteins that define the different blood types. The proportion of blood occupied by red blood cells is refered to as the hematocrit, and is normally about 45%. The combined surfaced area of all red blood cells of the human body would be roughly 2,000 times as great as the body’s exterior surface.
- 4,000-11,000 leukocytes. White blood cells are part of the immune system; they destroy and remove old or aberant cells and cellular debris, as well as attack infectious agents (pathogens) and foreign substances. The cancer of leukocytes is called leukemia.
- 200,000-500,000 thrombocytes.: thrombocytes, are called platelets, are responsible for blood clotting (coagulation). They change fibrinogen into fibrin. Thisfibrin creates a mesh red blood cells collect and clot, which then stops more blood from leaving the body and also helps to prevent bacteria from entering the body.
Plasma
| Parameter | Value |
|---|---|
| Hematocrit | 45 ± 7 (38–52%) for males 42 ± 5 (37–47%) for females |
| pH | 7.35–7.45 |
| base excess | −3 to +3 |
| PO2 | 10–13 kPa (80–100 mm Hg) |
| PCO2 | 4.8–5.8 kPa (35–45 mm Hg) |
| HCO3− | 21–27 mM |
| Oxygen saturation | Oxygenated: 98–99% Deoxygenated: 75% |
About 55% of whole blood is blood plasma, a fluid that is the blood’s liquid medium, which by itself is straw-yellow in color. The blood plasma volume totals of 2.7-3.0 litres (2.8-3.2 quarts) in an average human. It is essentially an aqueous solution containing 92% water, 8%blood plasma proteins, and trace amounts of other materials. Plasma circulates dissolve nutrients, such as glucose, amino acids, and fatty acids (dissolved in the blood or bound to plasma proteins), and removes waste products, such as carbon dioxide, urea, and lactic acid.
Other important components include:
- Serum albumin
- Blood-clotting factors (to facilitate coagulation)
- Immunoglobulins (antibodies)
- Lipoprotein particles
- Various other proteins
- Various electrolytes (mainly sodium and chloride)
The term serum refers to plasma from which the clotting proteins have been removed. Most of the proteins remaining are albumin and immunoglobulins.
The normal pH of human arterial blood is approximately 7.40 (normal range is 7.35-7.45), a weakly alkaline solutiion. Blood that has a pH below 7.35 is too acidic, whereas blood pH above 7.45 is too alkaline. Blood pH partial pressure of oxygen (pO2), partial pressure of carbon dioxide (pCO2), and HCO3 are carefully regulated by a number of homeostatic mechanisms, which exert their influence principally through the respiratory system and the urinary system in order to control the acid-base balance and respiration. Plasma alsoo circulates hormones transmitting their messages to various tissues. The list of normal reference ranges for various blood electolytes is extensive.
Blood in non-human vertebrates
Human blood is, most respects, typical of that of mammals, although the precise details concerning cell nubers, size, protein structure, and so on, vary somewhat between species. In non-mammalian vertebrates, however, there are some key differences.
- Red blood cells of non-mammalian vertebrates are flattened and ovoid in from, and retain their cell nuclei.
- There is considerable variation in te types and proportions of white blood cells; for example, acidophils are generally more common than in humans.
- Platelets are unique to mammals; in other vertebrates, small, nucleated, spindle cells are responsible for blood clotting instead.
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