Le tube proximal

Question 1

What is glomerular filtration autoregulation?

Answer 1

Helps keep DFG stable even with changes in blood pressure

stays constant between BP of 100-200

Question 2

What happens to autoregulation if BP increases or decreases?

Answer 2

What happens if BP increases?

paroi baroréceptrice perceives increase —> afferent arteriole narrows —> dissipates hydrostatic pressure —> glomerular capillary is not impacted by the increase in BP

What happens if BP decreases?

afferent arteriole dilates —> a greater percentage of this relieved pressure passes to the glomerular capillaries —> preserves the DFG

Question 3

What are the three main causes of kidney failure?

Answer 3

1. Irrigation sanguine faible
2. Système de drainage obstrué
3. Insuffisance rénale “parenchymateuse”
   
   1. Petites artères
   2. Les glomérules
   3. Des tubules
   4. Interstitium

Question 4

Where are the proximal tubules located?

Answer 4

Near the glomerulus

Question 5

How do the proximal tubules reabsorb things and how much do they reabsorb?

Answer 5

via active transport of Na+, coupled with other solutes, water via “transport iso-osmotique 50-75% of glomerular filtrate is reabsorbed depending on the “état volémique”

Question 6

Structure of “cellule du tubule proximal”:

Answer 6

Question 7

Why are there so many mitochondria?

Answer 7

Provide energy for active transport of Na+

Question 8

Why is there a bordure en brosse?

Answer 8

increase the contact between the membrane luminale and the liquide tubulaire

Question 9

Why are there folds in the membrane basolatérale?

Answer 9

Increase its surface area —> increase number of transporters per cell

Question 10

What is the principal “motor” of the tubule?

Answer 10

Na-K ATPase —> by decreasing the conc. of Na in the cells, it energizes the other mechanisms of transport within the cells

Question 11

How do the “cellules du tubule proximale” function?

Answer 11

Basolateral Na-K ATPase: Na out and K in —> decreases conc. of Na to 30mmol/L ish

Therefore sodium in the lumière tubaire wants to enter but can’t do so by itself —> co-transport with other molecules (glucose, phosphate, a.a) or can enter by an anti-port, H+ ions out for Na in

Question 12

What is “passage à l’espace paracellulaire”?

Answer 12

Substances reabsorbed by proximal tubular cells can enter through the luminal membrane and exit through the basolateral membrane to end up in the paracellular space to get to the peritubular capillaries

Question 13

De quel type d’épithélium est composé le tubule proximal?

Answer 13

L’épithélium du tubule proximal est un épithélium poreux qui permet le passage des molécules d’eau entre les cellules. Les molécules d’eau vont donc suivre les osmoles réabsorbés : cette réabsorption est iso-osmotique

Question 14

What is retrodiffusion?

Answer 14

Some of the liquid sent to the peritubular capillary isn’t absorbed and sent back through the cells into the lumière tubulaire

Question 15

What are some other important functions of the tubules proximales? (3)

Answer 15

Reabsorption of bicarbonate (HCO3-)

Reabsorption of of little proteins:

• the capillaire glomérulaire retains most of the proteins but some are still filtered out…
• these proteins are captured by the bordure en brosse or the cellule proximale —> the proteins are captured in vesicles which then merge with lysosomes which digest the proteins and break them down into amino acids and returned into the blood

Tubular secretion —> primitive function that filters out waste

Question 16

How are organic cations secreted?

Answer 16

enter from capillaries alone and leave through anti-port with H+

Question 17

How are organic anions secreted?

Answer 17

don’t need co-transport… enter from capillaries with Na+ and leave alone