Physiology
Physiology attempts to explain the physical and chemical factors that are responsible for the origin, development, and progression of life (physio = nature; ology = the study of). Each type of life, from the very simple virus up to the largest tree or to the complicated human being, has its own functional characteristics. Therefore, the vast field of physiology can be divided into viral physiology, bacterial physiology, cellular physiology, plant physiology, human physiology, and many more divisions.
In human physiology we are concerned with the specific characteristics and mechanisms of the human body that make it a living being. The very fact that we remain alive is almost beyond our own control, for hunger makes us seek food and fear makes us seek refuge. Sensations of cold make us provide warmth. Physiology has many subdivisions. For example, neurophysiology explains the workings of nervous system, and cardiac physiology studies the function of the heart, which acts as a muscular pump to keep blood flowing throughout the body.
Blood Physiology
Blood is the "the river of life" that surges within us. It transport everything that must be carried from one place to another within the body; nutrients, wastes, and body heat, through blood vessels.
Components and Functions of Blood
Among all of the body’s tissues, blood is unique: it is the only fluid tissue. Although blood appears to be a thick, homogeneous liquid, the microscope reveals it has both solid and liquid components. Essentially blood is a complex connective tissue in which living blood cells, the formed elements, are suspended in a nonliving fluid matrix called plasma.
Physical Characteristics and Volume
Blood is sticky opaque fluid with a characteristic metallic and salty taste. Depending on the amount of oxygen it is carrying, the color of blood varies from scarlet (oxygen-rich) to a dull red (oxygen-poor). Blood is heavier than water and about five times thicker, or more viscous, largely because of its formed elements. Blood is slightly alkaline, with a pH between 7.35 and 7.45. Its temperature (380C) is always slightly higher than body temperature.
Blood accounts for approximately 8 percent of body weight. The average adult body contains approximately 6 liters of blood.
Plasma
Plasma, which is approximately 90% water, is the liquid part of the blood and 10% of various substances. Over 100 different substances are dissolved in this straw-colored fluid. Examples of dissolved substances include nutrients, vitamins, salts (electrolytes), respiratory gases, hormones, plasma proteins, and various wastes and products of cell metabolism. Plasma proteins are the most abundant solutes in plasma. Except for antibodies and protein-based hormones, the liver makes most plasma proteins. The plasma proteins serve a variety of functions. For instance, albumin contributes to the osmotic pressure of blood, which acts to keep water in the bloodstream; fibrinogen, a coagulation proteins, help stem blood loss when a blood vessel is injured; and antibodies or immunoglobulins, part of the body’s defense mechanisms against diseases, help protect the body from pathogens. Other proteins include enzymes, hormones, growth factors, which are necessary to clot the blood when bleeding occurs. Plasma proteins are not taken up by cells to be used as food fuels or metabolic nutrients, as are other solutes such as glucose, fatty acids, and oxygen.