Ch 24 Fluid and Electrolyte Homeostasis and Imbalances

body fluid =

water within the body and the particles dissolved in it

body fluid flows in

arteries, veins, and lymph vessels

body fluid is contained in 2 major compartments, what are they

extracellular and intracellular

extracellular fluid

outside the cell; 1/3 of total

intracellular fluid

inside the cell ; 2/3 total

where are the locations of extracellular fluid?

interstitial compartment

vascular compartment

in dense connective tissue and bone

transcellular fluid

interstitial compartment is

between cells

vascular compartment is

in blood vessels

transcellular fluid is

synovial (joint), cerebrospinal, GI fluids

what are the four processes of fluid homeostasis?

1. fluid intake

2. fluid absorption

3. fluid distribution

4. fluid excretion

what is fluid intake?

entry of fluid into the body by any route

what is thirst triggered by?

-increased concentration of extracellular fluid (osmolality)

-decreased circulating blood volume

-dryness of the mucous membrane

older adults may have insufficient fluid intake due to

diminished cerebral osmoreceptor-mediated thirst

what are other possible route of fluid intake?

intravenous intake

intake tubes in GI tract and other body cavities

subcutaneous tissue or bone marrow infusion

rectal intake (tap water enema)

what is fluid distribution?

movement of fluid between vascular and interstitial compartments

capillary hydrostatic pressure and interstitial fluid colloid osmotic pressure move fluid from

blood vessels to the interstitial compartment

capillary hydrostatic pressure is

outward-pushing vascular fluid against vessel wall

interstitial fluid colloid osmotic pressure is

inward pulling force of particles in the interstitial fluid

capillary forces move fluid from

interstitial compartment into capillaries (vascular compartment)

capillary osmotic pressure is

inward pulling force of particles in vascular fluid

interstitial fluid hydrostatic pressure

outward push of interstitial fluid against outside of capillary walls

water moves in and out of the cells by

osmosis

Osmosis

fluid distribution between interstitial and intracellular compartments

cell membranes are permeable to

water but not electrolytes

osmosis mechanism

water crosses cell membrane rapidly to equalize particle concentration inside and outside the cells

water goes to

higher osmolality

what are the types of fluid excretion?

visible, invisible, and through abnormal routes

visible excretion

urine (kidneys)

sweat (skin)

invisible excretion

insensible perspiration (skin)

water loss (bowels,lung)

abnormal routes of excretion include

emesis (vomiting)

wound drainage

how do healthy kidneys operate in fluid excretion

healthy kidneys adjust fluid excretion in response to blood pressure and several hormones

what hormones do the kidney use in fluid excretion?

antidiuretic hormone (ADH)

aldosterone

natriuretic peptides (ANP and BNP)

what hormone is secreted in response to high osmolality or decreased volume

ADH which causes the kidneys to retain water (not salt)

what hormone is secreted in response to angiotensin II levels or increased plasma potassium?

aldosterone which induces kidneys to conserve saline (salt and water)

what natriuretic peptides (ANP and BNP)