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Ch21 Body Fluids

Ch21 Body Fluids - Body Fluid Compartments ICF and ECF Body...

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1 Body Fluids Body Fluid Compartments: ICF and ECF Body Fluids square4 Intracellular fluid (ICF): ~ 63% of total body fluids square4 high in K + , phosphate and magnesium square4 Extracellular fluid (ECF): ~ 37% of total body fluids square4 high in Na+, Cl- Body Fluids square4 Extracellular fluid (ECF) is composed of: square4 Interstitial fluid square4 Blood plasma square4 Lymph square4 Fluid in special compartments square4 CSF, aqueous & vitreous humors of the eye, and the serous and synovial fluids Homeostasis of Body Homeostasis of Body Fluids Fluids Maintained by: square4 Hypothalamus (osmoreceptors & thirst mechanisms) square4 osmoreceptors = specialized neurons in hypothalamus which monitor osmotic pressure of blood, i.e. detect any changes in blood solute concentration (mainly Na + conc.) square4 Kidneys (renin-angiotensin mechanism) square4 Hormones (aldosterone from the adrenal cortex) square4 pH regulators (electrolytes, chemical & physical buffers) Importance of Water square4 Main solvent square4 Transport medium square4 Necessary in metabolic reactions square4 Body has ~ 40 liters (10.56 gallons) of body water square4 % of body water c3down as the amount of fat and age c2up square4 Highest in the young, the thin, and the muscular square4 Babies: 75% water square4 Men: 63 % square4 Women: 52%
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2 Sources of Water Balance Water intake = Water output Water Balance square4 Constant fluid interchange between the 2 compartments square4 Fluids are transferred across semi-permeable membranes by diffusion or osmosis square4 osmosis is the primary method of water movement square4 Conc. of solutes (i.e. electrolytes) determines the direction of water movement square4 “where sodium goes, water follows” Water Balance square4 Regulated by ADH, aldosterone, and the enzyme renin square4 If dehydration occurs (e.g. in hemorrhage or sever diarrhea) f4rightc3down in blood volume & c3up in osmotic pressure square4 Osmoreceptors f4right hypothalamus f4right posterior pituitary f4right release of ADH f4rightc3up water reabsorption by the kidneys f4rightc3up blood volume, and c3down osmotic pressure If Dehydration Occurs: square4 Water loss f4rightc3down blood volume f4rightc3down BP f4right renal cells produce renin f4right catalyzes angiotensin I to angiotensin II square4 Angiotensin II f4right adrenal cortex f4right aldosterone f4rightc3up Na + & water reabsorption by the kidneys square4 Stimulates thirst centers in hypothalamus
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