Summary Medicine; homeostasis and body fluid compartments Review

Homeostasis and Body Fluid Compartments
- Homeostasis = maintenance of stable internal environment despite changing external
conditions

The Body Fluid Compartments

- Intracellular
o allows efficient cellular
metabolism
- Interstitial
o allows communication
between cells and plasma
- Plasma
o circulation
o allows us to be three
dimensional – allows
nutrients to be delivered to
body systems
- Lymph

Movement of fluid between the compartments

- Hydrostatic pressure
o Pushes water out
- Oncotic pressure
o Pulls water in

- HYDROSTATIC PRESSURE = Pressure on capillary walls due to pumping of heart (blood
pressure)
o Also due to gravity
- Water moves from an area of high hydrostatic
pressure to low hydrostatic pressure
o High blood hydrostatic pressure in
capillaries
o Low interstitial hydrostatic pressure (in tissues)
- Water PUSHED from capillaries to tissues

- OSMOTIC PRESSURE = the pressure exerted to prevent the movement of free solvent
molecules across a semi-permeable membrane from a low solute concentration to an area
of high solute concentration

- ONCOTIC PRESSURE = the pressure exerted by colloidal plasma proteins to reabsorb water
back into the blood system
o Due to plasma proteins
o Oncotic pressure of blood = colloid osmotic pressure
- Interstitial fluid contains less protein than blood – lower
oncotic pressure
- Water PULLED back into capillaries