Renal 1. Organization of the Urinary System Flashcards
What are the two main regions of the capsule around the kidney?
- Renal Cortex - outer portion
* Renal Medulla - inner portion
• Nephrons are where main action takes place, make urine, 2 types:
1) cortical nephron: located in renal cortex (80-90%)
2) juxamedullary nephron: big parts of then extends to renal medulla region (10%)
Nephron: composed of two parts -
the renal corpuscle and renal tubule
Renal tubule segments:
proximal convoluted tubule, Loop of Henle
Renal corpuscle:
Glomerulus + Bowman’s capsule
Flow of fluid through a Cortical Nephron
Globular (bowmans) capsule —> proximal consulates tubule —> descending loop of Henley —>
ascending loop of henle —>
distal consulates tubule (drains into collecting duct)
Flow of fluid through a medullary nephron
Globular (bowmans) capsule —> proximal consulates tubule —> descending loop of Henley —> thin ascending loop of henle —> ascending loop of henle —> distal consulates tubule (drains into collecting duct)
Where does blood enter and exit the nephron?
Blood enters via the Afferent arteriole and exits through the Efferent arteriole
How does blood enter the KIDNEY?
How does blood leave the KIDNEY?
Renal artery (enter) Renal vein (leave)
From the afferent arteriole, where does the blood flow after?
From afferent arteriole, flows into capillary network called glomerulus, then goes back into another arteriole (efferent exterior), this efferent arteriole turns into peritubular capillaries (tightly coupled with blood supply, important for putting things in and out of blood)
• Vasa-recta:
specific to medullary nephrons, referred to tight coupling of the nephron with surrounding blood supply
Which nephrons contain the vasa recta?
Medullary nephrons
• Granular cells
tightly coupled with afferent arteriole, important for blood pressure regulation. Sensitive to stretch.
High blood flow = with high blood pressure = granular cells stretch = sets cascade of events that reduces in blood pressure.
• Macula densa cells:
very sentive to amounts of salt that’s inside the tubule, not inside the blood.
High blood pressure = filter out a lot of salt out of blood into the glomerulus, and gets into distal tubule as it leaves glomerulus
Macula densa senses high salt =
high blood pressure = tries not to increase blood pressure.
Macula densa senses low salt =
low blood pressure = communicates with granular cells that produce renin, renin increases blood pressure. (Renin cascade)
What is the relationship between salt level in the blood and blood pressure?
They are direct.
- low salt = low blood pressure
- high salt = high blood pressure
Granular cells are coupled with ?
Afferent arteriole
What’s the relationship between blood pressure and blood flow?
They they direct.
- high blood pressure = high blood flow
- low blood pressure = low blood flow
The three cell types that regulate GFR are
- granular
- macula densa,
- mesengial
A decrease in the GFR flowing past the macula densa →
decreases sodium deliver to macula densa → increase renin secretion
What is the order blood flows through the different types of tubules in the medullary nephron?
proximal consulates tubule PCT—> THIN descending limb —> THIN ascending limb —> THICK ascending limb —> distal consulates tubul DCT —> cortical collecting tubul CCT —> connecting tubule —> initial collecting tubule (ICT) —> collecting duct
contrast the thin descending limp, the thick ascending limp is very important for
water balance (reapportion of water and blood pressure)
What kind of nerve fibre is connected where in the nephron, what does it do?
Granular cells Innervated by sympathetic nerve fibers which can change the resistance of the afferent arteriole
• Release renin which controls afferent arteriole resistance
Does the kidney connect do parasympathetic or sympathetic nerve fibres?
Only connects to sympathetic nerves.
What’s the sympathetic nerve role
Regulation of blood pressure
Blood enters the glomularus via the
Afferent arteriole, 20% of the blood gets filtered into the bowman capsule in the form of plasma, then leaves through the efferent arteriole
Are are the three ways the Glomulerus Filters the blood?
1) fenestrated (pores) of glomerular endothelial cells
2) basement membrane (basal lamina of glomerulus)
3) slit membrane between pedicels
Fenestration (pore) of the glomerular endothelial cells
Prevents filteration of blood cells
(like RBC, albium, Hb & other large mol.) Blood plasma passes through !
- Found within thinnest layer
if blood comes in urine = problem with
Fenestration as its job is to filter out blood cells and prevent then form goin into urine
What’s a reason the fenestrated pores in glomerular endothelial cells would allow blood to pass?
pores stretched due to high blood pressure = blood passes through tubule = goes into urine
Basement membrane
Prevents filtration of larger proteins.
Membrane is (-) charged, so repels any (-) charged molecules like ions, and attracts (+) charges ions and modules. Anything with (-) wont pass the membrane and is filtered
Slit membrane between pedicels
Prevents filteration of medium sized protiens.
What are pedicels and how do they help in filtration of medium sized molecules through the glomerulus?
Pedicels are projections that are created by podocytes, which are part of glomerulus.
These projection have slits between them (play role in filtration). Podocytes and slit membrane both have a (-) charge = only allow the passage of (+) charged ions, no (-) charges pass.
3 basic renal functions
1) filtration
2) reabsorption
3) secretion
Filtration:
Blood comes in through the afferent arteriole, goes into the glomerulus and then a certain amount of plasma contianing all ions is filter out of the blood ( 20% of it )
Where do all the filtered plasma and other contents o the blood go once filtered by the glomerulus?
It flows down the tubule (20% of all the ions and plasma will have been filtered)
In this tubule where the filtrate flows down, what occurs?
Reabsorption and secretions process occur in the tubule where all the filtrate is flowing down, so things are still being put in and out.
• Reabsorption:
After blood passes the glomerulus, continues down the efferent arteriole, there are still undersiables in the blood within the tubule, these undesirables are removed from the tubule and into the afferent capillary through REABSORPTION, putting it back into the blood.
In terms of reabsorption, what happens to glucose?
glucose in the glomulerus is freely filterable, so it all goes into the blood through reabsorption once its passes through glomerulus. That’s why there’s no glucose in urine.
If glucose in urine = problem with
reabsorption.
Glucose clearance is
0
• Secretion:
for the components that dont get filtered by glomerulus, and continue down the efferent and shouldn’t be in the blood, they will be secreted into the tubule (into the urine).
How does reabsorption occur?
Through the proximal tubule, substances can pass through the membrane via either the tight junctions (paracellular) or through transcellular transport. They are selectively permeable.
• Intercalated cells:
important for acid base balance.
• principal cells:
important for water regulation
