Renal System Flashcards
What are the two main compartments that make up body fluid?
- intracellular
- extracellular
Describe the intracellular body fluid.
- represents all fluid inside cells
- provides a stable medium for normal cell functioning
- consists of mainly water, dissolved ions, small molecules and larger proteins (enzymes)
- the principle component of the cytoplasm
- very stable and highly regulated
How much of the total body fluid does intracellular fluid make up?
- 2/3 of body fluids
How much of the total body fluid does extracellular fluid make up?
1/3
What three types of fluid make up the extracellular fluid?
- interstitial fluid
- plasma
- trans-cellular fluid
Describe interstitial fluid.
- largest subcomponent (80%)
- lies in the connective tissue matrix surrounding most cells
- contains nutrients, oxygen, waste, chemical messengers and small amount of proteins
Describe Plasma.
- 20% extracellular fluids
- exists in vascular system
- high protein concentration
- helps suspend vascular cells (erythrocytes etc.)
- role in transportation
Describe trans-cellular fluid.
- additional epithelial layer separating from the plasma
- eg. fluid in digestive tract
- very negligible in total body fluid
What is the ratio of fluid to solid in total body mass of:
1) males
2) females
1) 40% solids:60% fluids
2) 45% solids:55% fluids
Define homeostasis.
mechanisms which control the internal environment to keep conditions in the body relatively constant
What is the main difference between plasma and interstitial fluid and why is this important?
- higher concentration of proteins
- plasma proteins responsible for osmotic gradient across capillaries
- counteracts the hydrostatic pressure of capillary blood
What governs the exchange of water between different body fluid compartments?
- hydrostatic pressure
- colloid osmotic pressure
Define hydrostatic pressure.
- forces exerted by a fluid against a wall causing movement of fluid between different fluid compartments
- force pushing fluid out of capillary
Define colloid osmotic pressure.
- plasma proteins set up a gradient
- causing pulling force into the capillary, counteracting hydrostatic pressure
Why are ions ineffective osmotic agents (osmoles)?
can move rapidly between plasma and interstitial fluid due to their small size
Why are proteins good osmotic agents?
- membrane is selectively permeable
- proteins too large and therefore restricted to the plasma
define osmolality
concentration of substance in 1L solvent (water) measured in mosmoles / kg (H2O)
What does the osmolality of extracellular fluid depend on?
Na+
What does the osmolality of intracellular fluid depend on?
K+
Why is the membrane selective?
Allows movement of solutes (e.g. ions) across the membrane at different rates
What ions is the cell membrane more permeable to?
Cl- and K+
What ion is the cell membrane less permeable to?
Na+
