Lecture 38 Flashcards
How is chloride brought to the basolateral side of renal epithelial cells?
The positive charge which arises due to sodium absorption onto the basolateral side leads to the negative chloride moving to the basolateral side paracellularly.
How much of our body weight is water and what is the proportion?
60% of body weight for males is total body water, 55% for females, 2/3rds is intracellular fluid, 1/3 is extracellular fluid (1/5 is plasma, 4/5 is interstitial). ECF has higher Na+, Ca2+, Cl-, HCO3- and slightly higher pH but has lower K+. They both have the same osmolarity (275-295 mosmol/L).
What is the change in urine osmolarity as it travels through the loop of Henle and where is water absorbed?
Water is reabsorbed mostly in the PCT (66%) then the tDLH (proximal side of loop of Henle)(25%), then the CCT (2-8%), this is roughly the same as sodium and is driven primarily by the osmolarity changes by absorbing sodium. In the PCT the solution is isotonic, water is then absorbed in the tDLH, this makes the solution hypertonic , this becomes hypotonic at the TAL and becomes hypertonic again at the end due to anti-diuresis.
What does changiing water content do to our system and what does ADH do?
Changing water content will change the osmolarity of the system, fluid therefore shifts between the ECF and ICF to equalise (changing water content changes cell size and hence the function, particularly important for red blood cells). Water will move to the area of higher osmolarity and hence osmolarity needs to be controlled. The total body water changed alter plasma osmolarity, this is detected by osmoreceptors in the hypothalmus, stimulating the pituitary gland to secrete more or less ADH, (which then alters permeability of the collecting ducts, can also be triggered by decreased blood volume).
How does ADH increas water reabsorption?
The basolateral side of the collecting duct The basolateral side of the collecting duct cells have a vasopressin (ADH) receptor. This leads to a cascade which releases more aquaporin channels to allow water through for reabsorption. Without the ADH the collecting duct is relatively impermeable to water, meaning it is not rebsorbed and hence there is more water lost in the urine (low osmolarity).
What is diuresis and anti diuresis?
Diuresis is low ADH due to high amounts of water, anti diuresis is high ADH due to low amounts of water.
