Is blood is the only bodily fluid that can carry pathogens
They are concave on both sides and this gives them an optimal surface to volume ratio (Fig. The erythrocytes (red blood cells) are round, disk-shaped structures with an average diameter of 7.5 µm. The white blood cells (leukocytes) are further subdivided into (differential white cell count): The following are average values per microliter (1 µl = 1 mm 3) for the formed elements of the blood: Other noteworthy features of blood include its essentially constant composition, relatively constant osmotic pressure, and a pH value that varies only within narrow limits (7.2−7.4) (the so-called “constant internal milieu”). In addition to water, blood plasma contains a number of salts (electrolytes), proteins (albumins and globulins), lipids (fatty acids and cholesterol), and carbohydrates (blood glucose), and numerous vitamins, trace elements, and enzymes. When blood vessels are injured, the clotting factors carried in the blood, such as fibrinogen and platelets, are of vital importance. Simultaneously, blood transports heat from the metabolically active organs to the surface.Īnother task of blood is coagulation. Nutrients from where they are absorbed (intestinal villi) to where they are utilized (organs), of metabolic products to the excretory organs (kidneys), and of substances acting inside the body to their sites of activity (hormones). For instance, it undertakes the transport ofĢ62 6 Blood, the Immune System, and Lymphoid Organs The fluid portion of the blood, the plasma, subserves several different transportation tasks. In this case the blood serves solely as a means of transportation from the site of cell formation (bone marrow) to the site of action. They perform these tasks most of the time outside the blood vessels, in the connective tissues. White blood cells serve to defend against pathogens and foreign bodies ( immunity). The red blood cells, for instance, are responsible for the transport of blood gases from the lung to the tissues (oxygen) and from the tissues back to the lungs (carbon dioxide). While a function of the blood vessels is to distribute the blood overall (heat regulation and distribution of substances), the formed and unformed blood components have some very specific functions. The total circulating blood volume in humans is about 8 % of body weight i.e., the total blood volume of a person weighing 70 kg is about 5.6 liters.īlood has multiple functions closely connected with its components and with the vascular system. It averages 45 %, and is usually a little higher in men (47 %) than in women (43 %). The proportion of the total blood volume occupied by all blood cells in percent is called the hematocrit (see Fig. (leukocytes ) blood cells and the platelets (thrombocytes (Fig. The cellular components of this tissue are the red ( erythrocytes) and white connective tissue).īlood may be viewed as tissue-a sort of fluid transportation tissue, of which the intercellular substance is the blood plasma (plasma). For the most part they are formed in the same site, the bone marrow, but they differ considerably in their location and the site of their functioning (blood vs. Developmentally they both originate from the mesenchyme.
Is blood is the only bodily fluid that can carry pathogens free#
The cells of the blood and the immune cells are free connective tissue cells and are in part of identical origin. 260 6 Blood, the Immune System, and Lymphoid Organs