Osmosis and Membrane Process Flashcards
Osmolality
measurement of solute concentration in fluid
High osmolality = high solute concentration
Range of serum osmolality varies in species
Increased osmolality of blood triggers
Desire to drink
Release of antidiuretic hormone
Decreased osmolality of blood
Inhibits desire to drink
Inhibits release of antidiuretic hormone
Serum osmolality tests may be ordered to asses
Hydration status
High osmolality if dehydrated
Hyperglycaemia
Functioning of hypothalamus
Poisoning by ethylene glycol
Antifreeze poisoning
Series of oxidation reactions in liver and kidneys metabolize ethylene glycol
Toxic metabolites cause metabolic acidocis and nephrotoxosis
Oxalate is cytotoxic
Isotonic fluid therapy
Osmolality comparable to that of normal blood
extracellular fluid has same concentration of dissolved substances as intracellular fluid
Example : 0.9% NaCl (normal saline)
Hypertonic fluids
Osmolality is greater than that of blood
Extracellular fluid has higher concentration of solutes than the cytoplasm
Water leaves the cell, causing the cell to shrink and become shrivelled
Hypotonic fluids
Osmolality is less than that of blood
Higher concentration of solutes in the cytoplasm than in the extracellular fluid
Water flows into the cell and causes it to swell and possibly to break
Electrolytes are
Small and most abundant solute in body
Greatest ability to cause fluid shifts between compartments
Concentration in body fluids is expressed as milliequivalents per litre
Osmolality and water
Any change in the concentration of any solute incurs movement of water from one compartment to another
Water crosses cell membrane
or
Water crosses capillary walls
Edema is a
Abnormal, excess accumulation of fluid in tissue
Common sign of abnormal movement of fluid from vascular space into interstitial space
Pulmonary edema
Fluid leaking into lungs
Cutaneous edema
Leaking into skin
Crystalloid fluid
Composed of water rich with electrolytes
hypotonic or isotonic
Solutes are small
Able to cross the vascular wall
Good for rehydrating extravascular spaces and correcting acid/base imbalances
Colloid fluid
Heavy molecules suspended in isotonic crystalloid
Solutes too large to cross vascular wall
“hold” fluid in intravascular space
Passive process
Requires no energy
Active process
Require energy to be used
Three types of membrane permeability
Freely permeable
Impermeable
Selectively permeable
Diffusion
Kinetic movement of molecules from higher to lower concentration
Concentration gradient
Factors determining whether molecule may pass through cell membrane:
Molecular size
Lipid solubility
Molecular charge
Channels allow certain ions to pass through