Renal Overview Flashcards
Where are nephrons located in the kidney?
Renal pyramids
What are the two specific ways that the kidneys regulate water/electrolyte balance?
- Regulate ECF
2. Plasma osmolality
How, generally, do the kidneys function to regulate BP? (2)
- Volume control
2. Renin-angiotensin system
What are the four major chemicals that the kidneys excrete?
Urea
Uric acid
Creatinine
Urobilins
What is the main source of erythropoietin?
Kidneys
Where does the last step of Vit D synthesis take place?
Kidneys
When do to the kidneys participate in gluconeogenesis?
Late fast
What is the lumen of the nephron?
Renal pelvis
What is the luminal side of the tubular cells?
The side that faces the lumen of the tubule
What is the apical side of the tubular cell?
The side opposite that of the lumen
What is on the basolateral side of the tubular cells?
Tight junctions
Where is ADH stored in the kidney?
1.
What is the branching names of the renal artery?
Interlobar to arcuate to afferent arterioles to efferent
What is the functional difference between the cortical nephrons and the juxtamedullary nephrons?
Cortical can dilute urine, but cannot concentrate
Juxtamedullary can concentrate and dilute urine
What are the two places that you can find nephrons? How are these named? (2)
In the cortex (superficial)
Medulla (juxtamedullary nephrons)
What is the functional unit of the kidney?
Nephron
What is the name of the artery that extends into Bowman’s capsule?
Afferent
What is the name of the artery that extends out of Bowman’s capsule?
Efferent
What is the structural difference between juxtamedullary and cortical nephrons?
Juxtamedullary has thin descending and ascending
Cortical has small thin descending. (remainder is thick)
What are the two components of the renal corpuscle?
Glomerulus and Bowman’s capsule
True or false: any freely filtered substance will be at the same concentration in the filtrate as it is in the plasma in the afferent arteriole
True
What controls filtration in the glomerulus?
Starling’s forces
What part of the glomerulus filters?
Glomerular capillaries
What part of the glomerulus reabsorb filtrate? What allows for this?
Peritubular capillaries
High protein [c]
What is the dilated, blind end of the nephron tubule that is invaginated by a tuft of of capillaries?
Bowman’s capsule
What are the three components of the Bowman’s capsule that allows for filtration of the blood?
- Capillary endothelium
- Basement membrane
- Specialized epithelium of capsule (podocytes)
What are the cells that act as phagocytes and removed trapped material from the basement membrane of the glomerulus?
Mesangial cells
What are the two epithelial layers of Bowman’s capsule?
- the visceral layer which surrounds the capillaries
2. the parietal layer which is the outer part of the capsule.
Bowman’s capsule empties into what?
The proximal convoluted tubule
What is the general term used when substances move from lumen of tubule into interstitial fluid (and then into blood vessels)?
Reabsorption
What is the general term used when substance moves from blood vessel into tubular fluid?
Secretion
What are the macroscopic areas of the kidney that produce urine? What are the structures that the urine passes to from here to the ureters?
Renal pyramids to minor calyx to major calyx to renal pelvis
What are peritubular capillaries? Are they found on all nephrons?
Capillaries next to the tubules. These are always found with nephrons
Where is plasma filtered in the nephron?
At the glomerular capillaries into Bowman’s space
Where does the filtrate flow from Bowman’s space?
To the proximal tubule
Where are the cells of the macula densa? What is their function?
In the distal convoluted tubule In contact with the afferent arteriole
Monitors NaCl delivery to the distal tubule
Is the pressure in Bowman’s capsule always the same?
Normally narrow range, but can vary in disease
What prevents proteins from flowing from the capillaries into Bowman’s space?
Negative charges on endothelial cells/podocytes and the presence of a BM
What is the protein concentration of the efferent arterioles relative to the afferent? What is the consequence of this?
Higher d/t loss of plasma
This allows for easier reuptake later for the peritubular capillaries
From the blood to Bowman’s space, how many layers does filtrate have to go through? What are these?
Three– Endothelium, BM, podocytes
What is the structural feature of the capillary endothelial cells that allows for high rates of filtration?
Fenestrated
What are the cells that sit on the capillaries in Bowman’s capsule that aid in filtration, and have many interdigitating extension?
Podocytes
What are the four processes that take place in the nephron?
- Filtration
- Reabsorption
- Secretion
- Excretion
Urinary excretion rate = what?
The rate at which the substance is filtered - the reabsorption rate + the rate at which it is secreted from the peritubular capillary blood into tubules
Looking at a nephron, how do you determine whether or not it is a cortical or a juxtamedullary one?
Where the glomerulus is
What are the cortical medullary rays?
The part of the cortex that contains the straight proximal tubules, cortical thick ascending limbs, and cortical collecting ducts
What are the structures through which filtrate passes on its way to the collecting duct (starting with Bowman’s capsule, 6)
- Bowmans capsule
- Proximal tubule
- Thin descending limb
- Thin ascending limb (if juxtamedullary)
- Thick ascending limb
- Distal tubule
How many cell layers make up the walls of the distal/proximal convoluted tubule?
One
The tight junctions between the cells that surround the tubule lumen separate what two parts of the nephron?
The lumen membrane and the basolateral membrane
What is the Na/K pump located in the nephron?
The cells of the proximal tubule
Where does most Na reabsorption occur in the nephron?
Proximal tubule
What is the chemical driving force for Na from the the lumen side of the tubule: into or out of the renal tubule cells?
Into
Thick or thin cells surrounding the proximal tubule?
Thick
Thick or thin cells surrounding the descending loop of henle ?
Thin
Thick or thin cells surrounding the ascending loop of henle?
Thick
Thick or thin cells surrounding the early and late distal tubules?
Thick
What is the direction of flow for Na, Cl, K, H2O, glucose, and aa in the proximal tubule? H+?
Out of for all except H+
What is direction of flow for Na, Cl H2O, and urea in the descending loop of henle?
All into except for H2O
What is the direction of flow for Na, Cl, K, Ca, HCO3, H+, and Mg in the thick ascending loop of Henle?
all out of the tubule lumen and into the capillaries except for H+
What are the two chemical that pass out of the lumen from the early distal tubule?
Na and Cl
What is the flow of Na, K, H2O, HCO3, and H+ in the late distal tubule?
Out of lumen: Na, H2O, HCO3
Into lumen: H+ and K+
How is Na reabsorbed from the lumen of the tubule?
Na/K pump into cell, and out towards capillaries
How is glucose reabsorbed from the lumen of the tubule?
Synport
Where is most of the Na reabsorbed? How?
Proximal tubule
Via Na proton antiporter
How is HCO3 reabsorbed?
Na/H transporters
What is absorbed in the first half of the proximal tubule?
Na with glucose, amino acids, lactate
How is glucose reabsorbed from the tubule?
Na symporters
What is the major driving force of water out of the tubule? How can it diffuse so readily?
Reabsorption of solutes
Aquaporins
Approximately what % of the filtered water Na+, Cl- , K+ have been reabsorbed by the end of the proximal tubule?
67%
What is the main way that substances are moved from the tubule of a nephron back into capillaries?
Na symport
What is isosmotic reabsorption of water?
Water moves with dissolved solutes
What can pass through tight junctions of the tubules?
Na and Cl
What are the two pumps on the capillary side of the renal tubule cell? Which way do the ions flow?
Na/K pump -Na in, K out
K/Cl pump -both out
A small amount of proteins are filtered each day. How are these reabsorbed?
Peptidases on the luminal surface breakdown to AAs. Reabsorbed like other AAs
Endocytosis for larger proteins
True or false: • Normally virtually all filtered protein is reabsorbed so little or no protein in urine.
True
How does proteinuria come about?
since endocytosis/digestion mechanism easily saturated an increase in filtered protein can cause proteinuria
What is the significance of the limited number of transporters in the distal tubule?
Saturable, and shared by many things
What is the major process occuring in the thick ascending limb of a nephron?
NaCl is pumped out but water cannot follow
Where does countercurrent exchange take place?
In the loop of henle
Where is the macula densa located within a nephron?
The final portion of the thick ascending limb
What is significant about the thick loop of henle, and plays a major role in secretion? What is the significance of this?
Impermeable to water
Thus can dilute filtrate here
Where can the body change the water concentration of the filtrate?
Collecting duct
What is the diluting segment of a nephron?
Thick ascending tubule
What part of the nephron is responsible for isosmotic reabsorption?
Descending limb
True or false: there are receptors that directly control water balance, and adjust excretion accordingly
False
Where is osmolality of the blood monitored?
Hypothalamus
Where is ADH synthesized?
Hypothalamus
What are the changes that osmoreceptors experience that cause a change in ADH secretion?
Swelling/shrinkage
