Salt and Water transport in the GI tract Flashcards
What does osmolality mean?
- concentration of dissolved particles of chemicals and minerals within a solution
- high osmolality = high concentration of the substance dissolved
- very salty water = high osmolality of salt
What is a hypotonic solution?
- high concentration of solute inside cell
- H2O enter the cell to dilute solute and cell swells
- osmolality is lower than plasma
What is a hypertonic solution?
- low concentration of solute inside cell
- H2O leaves the cell to dilute solute outside of cell and it shrinks
- osmolality is higher than plasma
What is an isotonic solution?
- solute concentration is equal inside and outside of the cell
- no net movement of H2O
- osmolality is the same as plasma
Maintenance of bodily fluids comes under the regulation of 3 systems, what are these?
1 - enteric nervous system
2 - immune system
3 - endocrine system (hormones)
Where does fluid reabsorbtion take place in the GIT?
- throughout the GIT
- most in colon
Roughly how many litres of fluid enters the GIT through diet and secretions from the GIT, and how much of this gets reabsorbed?
- 9L enters the GIT
- 8.9L is reabsorbed
Although the majority of fluid secreted into the GIT is reabsorbed, where is fluid lost in the GIT?
- faeces
- aprox 100ml/day
Why is it important that the GIT reabsorbs the majority of liquid secreted into the GIT?
- maintains homeostasis
- allows secretions into GIT (enzymes etc..)
If liquids in the GIT tract either cannot be absorbed sufficiently or too much is absrobed or caused by dehydration, what can this cause?
- too much reabsorbed or dehydration = constipation
- too little reabsorbed = diarrhea
What does electrolyte mean?
- a substance that is capable of carrying an electrically charge
If sodium chloride (NaCl) was dissolved in a liquid what would this dissacociate into?
- Na+
- Cl-
What are the dominant intra and extracellular ions?
- inter = K+
- extra = Na+
What is the dominant extracellular anion?
- Cl-
Why is it important for the concentration of Na+, K+ and Cl- to be different intracellularly and extracelluarly?
- gives us the electrochemical gradient
- important for metabolic processes
What is the normal intra and extracellular concentration of Na+?
- intra = 10 mEq/L
- extra = 142 mEq/L
What is the normal intra and extracellular concentration of K+?
- intra = 140 mEq/L
- extra = 4 mEq/L
What is the normal intra and extracellular concentration of K+?
- intra = 4 mEq/L
- extra = 103 mEq/L
Cell membranes in the body are semi-permeable. What does this mean?
- certain things are able to cross but others are not
What is endocytosis and exocytosis?
- endocytosis = substance/molecule is brought into the cell
- exocytosis = substance/molecule leaves the cell
Molecules that are unable to cross semi-permeable membranes use what to transfer across membranes?
- transmembrane proteins
- Na/ATPas for example
What is able to freely move cross the semi-permeable membranes?
- non-polar, hydrophobic molecules (O2, CO2)
- small uncharged molecules (i.e. water, urea, ethanol)