Extracellular fluid (ECF) surrounds all cells in the body. The intracellular fluid (ICF) compartment is the system that includes all fluid enclosed in cells by their plasma membranes. Fluid Compartmentsīody fluids can be discussed in terms of their specific fluid compartment, a location that is largely separate from another compartment by some form of a physical barrier. Water content varies in different body organs and tissues, from as little as 8 percent in the teeth to as much as 85 percent in the brain. ![]() Water content of the body’s organs and tissues. In contrast, teeth have the lowest proportion of water, at 8–10 percent. The brain and kidneys have the highest proportions of water, which composes 80–85 percent of their masses. The percent of body water changes with development, because the proportions of the body given over to each organ and to muscles, fat, bone and other tissues change from infancy to adulthood (Figure 17.11.1). Human beings are mostly water, ranging from about 75 percent of body mass in infants to about 50–60 percent in adult men and women, to as low as 45 percent in old age. An appropriate balance of solutes inside and outside of cells must be maintained to ensure normal function. As a result, water will move into and out of cells and tissues, depending on the relative concentrations of the water and solutes found there. Osmosis is basically the diffusion of water from regions of higher concentration to regions of lower concentration, along an osmotic gradient across a semi-permeable membrane. In the body, water moves through semi-permeable membranes of cells and from one compartment of the body to another by a process called osmosis. For instance, sodium ions (Na +) and chloride ions (Cl –) are often referred to as electrolytes. Often in medicine, a mineral dissociated from a salt that carries an electrical charge (an ion) is called an electrolyte. In the human body, solutes vary in different parts of the body, but may include proteins-including those that transport lipids, carbohydrates and, very importantly, electrolytes. The dissolved substances in a solution are called solutes. The chemical reactions of life take place in aqueous solutions. Identify the causes and symptoms of oedema.Explain the importance of protein channels in the movement of solutes.Contrast the composition of the intracellular fluid with that of the extracellular fluid.Explain the importance of water in the body.Oxford: Oxford University Press 2011.By the end of this section, you will be able to: Wilkins R, Cross S, Megson I, Meredith D, editors. Water, electrolytes and acid-base balance. Note: Numerical data in the diagram is from reference 2.ġ. The diagram below illustrates the values for total body water and fluid distribution based on a 70 kg man and are approximate values. The plasma and interstitial fluid are separated by the capillary wall. cerebrospinal fluid, synovial fluid, digestive secretions, peritoneal fluid, intraocular fluid and pleural Transcellular fluid is enclosed within epithelial lined spaces (e.g.Interstitial fluid surrounds the cells and. ![]() The extracellular fluid is further subdivided into the following body fluid compartments: The intracellular fluid and extracellular fluid are separated by cell membranes. Extracellular fluid, which is found outside the cells.Intracellular fluid, which is found inside the cells.The distribution of total body water is divided into two major body fluid compartments: ![]() This is mostly due to a decrease in muscle mass and an increase in body fat. In old age, the total body water percentage decreases. These differences in total body water percentage between men and women are because of women typically having less muscle mass and a greater amount of adipose tissue than men. In healthy lean people, the total body water comprises 50-60% of body weight in men and 45-50% of body weight in women.
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