Structure and function of renal tubule

Question 1

mention two techniques used to investigate tubular functions and briefly explain

Answer 1

micropuncture; two smalls holes are made in the wall of the nepron where experiment is to take place. viscous oil is then injected, then the fluid is injected and after a wax block. the fluid is then collected later before the first oil block and analysed.

electrophysiology(electrode potential); a micro electrode is inserted in the wall of the nephron and this is used to measure whether ions are moving against conc gradient or down it.
electrophysiology(patch calmping); current flows through indiviudual ion channel measured, electrical ressistance can be measured across patch of cell memebrane an changes that occur when channels close or open. used to determine types of channels and its response to drugs and hormones

Question 2

mention the two types of nephrons

Answer 2

cortical nephron- which makes up 85% of nephrons and has a short loop of henle

juxta-medullary nephron which makes up 15% of nephrons and has a long loop of henle. kangaroo rat is an example of an animal that has juxta medullary nephron.

Question 3

what channels are found on the luminal and basolateral membrane of the pct

Answer 3

luminal; sodium-glucose symporter
na amino acid symporter
na hydron symporter

basolateral; sodium/pottasium atpase pump
glut 2 transporter

Question 4

what channels are found on the luminal and basolateral membrae of the thick loh

Answer 4

luminal- soudium chloride pottasium
symporter

basolateral; sodium pottasium atpase
pottasium channels
chloride channels

Question 5

functions of the early dct

Answer 5

this is where the macula densa cells are found
it provides feedback of glomerular filtrate rate and tubular fluid flow within that nephron
it is relatively straight ie not the most convoluted part of the convoluted tubule

Question 6

functions of the late dct

Answer 6

solute reabsorption without water reabsorption
further dilution of tubular fluid
high na/k atpase activity
low water permeability
adh can exert its actions
has a role in acid base balance via secretion of ammonia

Question 7

describe the collecting duct

Answer 7

the collecting duct is formed by the joining of collecting tubule. it is made up of two cells; a)the intercalated cells which are involved in acid-base regulation and acidification of urine
b) the principal cells: which are involved in ECF volume regulation and Na balance.
it is the final site for urine processing an dit is made very permeable to water by ADH.
it is also permeable to urea.
has very few mitochondria

Question 8

What are the the four major factors contributing to the build up of solute conc in the renal medulla

Answer 8

a)active transport of sodium and co-transport of k and cl out of the thick ascending limb into the medullary interstitium

b) active transport of ion from the CD into the medullary interstitium.

c)facilitated diffusion of urea from CD into the medullary interstitium

d) very little diffusion of water from the ascending limbs of tubules into the medullary interstitium.