understanding ^Vo rds de-, separation from:
dehydration—removal of water from the cells or body fluids. edem-, swelling: edema— swelling due to an abnormal accumulation of extracellular fluid. -emia, a blood condition: hypoproteinemia— abnormally low concentration of blood plasma protein. extra-, outside: extracellular fluid—fluid outside of the body cells. im- (or in-), not: imbalance—
condition in which factors are not in equilibrium. intra-, within: intracellular fluid—fluid within the body cells. neutr-, neither one nor the other: neutral—solution that is neither acidic nor basic. -osis, a state of: acidosis— condition in which hydrogen ion concentration is abnormally high. -uria, a urine condition:
ketouria—presence of ketone bodies in the urine.
After you have studied this chapter, you should be able to
1. Explain water and electrolyte balance, and discuss the importance of this balance.
2. Describe how the body fluids are distributed within compartments, how fluid composition differs between compartments, and how fluids move from one compartment to another.
3. List the routes by which water enters and leaves the body, and explain how water input and output are regulated.
4. Explain how electrolytes enter and leave the body, and how the input and output of electrolytes are regulated.
5. Explain acid-base balance.
6. Describe how hydrogen ion concentrations are expressed mathematically.
7. List the major sources of hydrogen ions in the body.
8. Distinguish between strong and weak acids and bases.
9. Explain how chemical buffer systems, the respiratory center, and the kidneys minimize changing pH values of the body fluids.
he summer of 1995 was a brutal time in Chicago. A fierce heat wave swept the city on July 12-16, with temperatures hovering between 93-104° F. The Cook County medical examiner's office worked round the clock during this time to handle 465 heat-related deaths. Several factors point to a heat-related death:
Body temperature at or soon after death of greater than 105° F
Evidence that heat caused the death
Decomposition of the corpse
No other identifiable cause of death
Evidence that the person was alive just before the heat wave
In the many blazing hot, un-air-conditioned apartments of Chicago, mostly elderly people fell victim. An untold number suffered severe dehydration, which may have been the direct cause of death. As body fluids became concentrated, with not enough water to form sweat to counter the rising and relentless heat, body temperatures soared. Wastes accumulating in extracellular fluids may have caused symptoms of cerebral disturbance, including mental confusion, delirium, and coma, preventing many people from seeking help.
Other communities also lost citizens to the heat wave of 1995. As a result, local governments now issue public service announcements in-
The term balance suggests a state of equilibrium, and in the case of water and electrolytes, it means that the quantities entering the body equal the quantities leaving it. Maintaining such a balance requires mechanisms to ensure that lost water and electrolytes will be replaced and that any excesses will be excreted. As a result, the levels of water and electrolytes in the body remain relatively stable at all times.
It is important to remember that water balance and electrolyte balance are interdependent because electrolytes are dissolved in the water of body fluids. Consequently, anything that alters the concentrations of the electrolytes will necessarily alter the concentration of the water by adding solutes to it or by removing solutes from it. Likewise, anything that changes the concentration of the water will change the concentrations of the electrolytes by making them either more concentrated or more dilute.
Body fluids are not uniformly distributed. Instead, they occur in regions, or compartments, of different volumes that contain fluids of varying compositions. The movement of water and electrolytes between these compartments is regulated to stabilize their distribution and the composition of body fluids.
forming people how to deal with heat and provide air-conditioned areas for people to stay. A piece of advice for all—when the mercury rises, drink! The human body cannot function for long with too little water.
The body of an average adult female is about 52% water by weight, and that of an average male is about 63% water. The differences between the sexes is due to the fact that females generally have more adipose tissue, which has little water. Males have relatively more muscle tissue, which contains a great deal of water. Water in the body (about 40 liters), together with its dissolved electrolytes, is distributed into two major compartments: an intracellular fluid compartment and an extracellular fluid compartment (fig. 21.1).
The intracellular (in"trah-sel'u-lar) fluid compartment includes all the water and electrolytes that cell membranes enclose. In other words, intracellular fluid is the fluid within the cells, and, in an adult, it represents about 63% by volume of the total body water.
oo Reconnect to chapter 1, Homeostasis, page 6
The extracellular (ek"strah-sel'u-lar) fluid compartment includes all the fluid outside the cells—within the tissue spaces (interstitial fluid), the blood vessels (plasma), and the lymphatic vessels (lymph). Epithelial layers separate a specialized fraction of the extracellular fluid from other extracellular fluids. This transcellular (trans-sel'ular) fluid includes cerebrospinal fluid of the central nervous system, aqueous and vitreous humors of the eyes, synovial fluid of the joints, serous fluid within the body cavities, and fluid secretions of the exocrine
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.