In normal blood, about 45 percent of a sample is erythrocytes. The hematocrit of any one sample can vary significantly, however, about 36—50 percent, according to gender and other factors.
Normal hematocrit values for females range from 37 to 47, with a mean value of 41; for males, hematocrit ranges from 42 to 52, with a mean of The percentage of other formed elements, the WBCs and platelets, is extremely small so it is not normally considered with the hematocrit. So the mean plasma percentage is the percent of blood that is not erythrocytes: for females, it is approximately 59 or minus 41 , and for males, it is approximately 53 or minus When you think about blood, the first characteristic that probably comes to mind is its color.
Blood that has just taken up oxygen in the lungs is bright red, and blood that has released oxygen in the tissues is a more dusky red. This is because hemoglobin is a pigment that changes color, depending upon the degree of oxygen saturation. Blood is viscous and somewhat sticky to the touch. It has a viscosity approximately five times greater than water. The viscosity of blood has a dramatic impact on blood pressure and flow.
Consider the difference in flow between water and honey. The more viscous honey would demonstrate a greater resistance to flow than the less viscous water. The same principle applies to blood. Although the surface of blood vessels is relatively smooth, as blood flows through them, it experiences some friction and resistance, especially as vessels age and lose their elasticity, thereby producing heat.
This accounts for its slightly higher temperature. The pH of blood averages about 7. Blood is therefore somewhat more basic alkaline on a chemical scale than pure water, which has a pH of 7. Blood contains numerous buffers that actually help to regulate pH.
Blood constitutes approximately 8 percent of adult body weight. Adult males typically average about 5 to 6 liters of blood. Females average 4—5 liters. Like other fluids in the body, plasma is composed primarily of water: In fact, it is about 92 percent water. Dissolved or suspended within this water is a mixture of substances, most of which are proteins. There are literally hundreds of substances dissolved or suspended in the plasma, although many of them are found only in very small quantities.
Visit this site for a list of normal levels established for many of the substances found in a sample of blood. In the process of evolution a series of structural modules have been incorporated into protein molecules as their integral domains by exon duplication and shuffling.
Owing to variable conformations of the resulting multi-domain proteins, the same modules may perform different tasks and be recognized only by specific ligands, thus controlling the delicately balanced system of haemostasis. Abstract A vascular fissure requires a patch that must be provided by constituents of the cellular and fluid phases of flowing blood.
Publication types Review. High levels of hemoglobin and other cellular debris can damage the kidneys. White blood cells White blood cells help fight infections. When viruses or bacteria enter the blood, for example through a cut, a scraped knee or an infected ear, white blood cells surround and destroy the invading microorganisms bacteria and viruses.
The three main types of white blood cells are granulocytes, lymphocytes and monocytes. Monocytes support the activity of other white blood cells through phagocytosis and identifying targets to be destroyed by antibodies. Most white blood cells live for a few hours or days in the blood, so the bone marrow is constantly producing more.
Vaccines work by triggering the body to produce these memory cells without actually making us sick. In transfusion medicine, white blood cells are removed from the final blood products. This procedure provides several benefits to patients receiving transfusions. Firstly, they are less likely to have a fever after their transfusion. They are also less likely to make antibodies against transfused donor cells, and so future platelet transfusion will remain effective.
White blood cells may also harbour infectious disease agents such as cytomegalovirus CMV. By removing them we reduce the risk of infection. Platelets Platelets are small, delicate, plate-shaped cell fragments that help stop bleeding by sticking together and forming a clot that seals a hole in a blood vessel.
Clot formation is triggered by the platelets coming into contact with torn blood vessels. This activates the platelets.
These places are called receptors. Von Willebrand factor is stored in the endothelial cells lining the blood vessels. The endothelial cells release the VWF into the blood. Activation and Secretion After the platelets stick to the collagen where the blood vessel is torn, they change their shape. Each platelet changes from a smooth disk to a ball shape with long arms that can reach out to other platelets.
This is called platelet activation. Activated platelets can stick to each other and to clotting proteins in the blood. Inside each platelet are storage spaces called granules. When the platelet changes shape, chemicals inside the granules are pushed out into the bloodstream.
This is called secretion. These chemicals from the granules signal other platelets to come and help. The chemicals allow the next step in forming a platelet plug, aggregation, to happen. Aggregation To form a platelet plug , the platelets have to stick to each other as well as to the blood vessel.
This is called platelet aggregation. The platelets form a clump that plugs the hole in the blood vessel. When platelets can stick to the blood vessel adhesion , change shape and signal other platelets to come help activation and secretion , and stick to each other aggregation , a good platelet plug is made.
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