lecture 29 Flashcards
which kidney is most inferior and why?
The right kidney is a little bit lower because it sits below the liver
Which structures comprise a kidney lobe?
one medullary pyramid and all the cortex that surrounds it
what is the nephron?
microscopic functional unit of the kidney responsible for urine formation
How many nephrons are their per kidney?
~1 million per kidney
How many types of nephrons are there?
two different types
what are the two types of nephrons?
Cortical nephrons
juxtamedullary nephrons
what is the most common type of nephron?
cortical nephrons ~85%
where are cortical and juxtamedullary nephrons located?
cortical nephrons lie mainly in the cortex
juxtamedullary nephrons extend deep into the medulla
what are juxtamedullary nephrons important for?
formation of concentrated urine
Functions of nephrons?
selectively filter blood
return to blood anything to be kept
carry waste away for storage and expulsion
Each nephron is comprised of?
a glomerular capsule
renal tubules
a collecting duct
Each nephron is associated with?
a glomerulus
peritubular capillaries
Glomerular capillaries are specialised for?
filtration
what type of capillaries are glomerular capillaries?
thin walled single layer of fenestrated endothelial cells
how are glomerular capillaries fed and drained?
By arterioles
peritubular capillaries are specialised for?
absorption
Peritubular capillaries wrap around what?
renal tubules
peritubular capillaries receives what?
filtered blood from glomerulus via efferent arterioles
reabsorbed filtrate from nephron
what are the vasa recta?
extensions that follow loops of Henle deep into the medulla
Vasa recta are only found where?
with juxtamedullary nephrons
Glomerulus is enclosed by?
glomerular capsule to form renal corpuscle
the renal corpuscle is where what meets?
capillary and nephron meet
the renal corpuscle is the site of what?
filtration barrier
What is the first part of the nephron?
glomerular capsule
What are the two layers of the glomerular capsule?
Outer parietal layer of simple squamous cells
inner visceral layer of podocytes
Between the two layers of the glomerular capsule is?
Capsular space which receives filtrate
what are podocytes surrounded by?
glomerular capillaries
what are podocytes?
very branched, very specialised epithelium
what are pedicels?
branches from intertwining foot processes of podocytes
What forms between pedicels?
filtration slits
what passes through filtration slits?
filtered blood passes through and into the capsular space
what are other names for filtration barrier?
blood-urine barrier
glomerular capsular membrane
where does the filtration barrier lie?
between blood and capsular space
what is allowed to pass filtration barrier?
water and small molecules
what is restricted by filtration barrier?
most proteins and red blood cells
what are the three layers of the filtration barrier?
fenestrated endothelium of glomerular capillary
fused basement membrane
filtration slits between the pedicels of the podocytes
which structures form renal corpuscle?
glomerulus
glomerular capsule
what happens after flirtation?
waste fluid and solutes filtered from the blood, some of which is reabsorbed and a lot further screened
what does urine =?
filtered - (reabsorbed + secreted)
What is the role of the proximal convoluted tubule?
bulk reabsorption
what surrounds the proximal convoluted tubule?
peritubular capillaries
What epithelium is the proximal convoluted tubule?
cuboidal epithelial cells
what structure reflects the function of the PCT?
dense microvilli on luminal membrane and highly folded basolateral membrane
What is the purpose of mitochondria in PCT?
to provide energy for bulk active transport of molecules like glucose
where does the nephron loop extend to?
from PCT and down into the medulla
Why is length important for nephron loop?
for production of dilute/concentrated urine
what surrounds the nephron loop?
vasa recta, in juxtamedullary nephrons only
what forms the thick descending limb of nephron loop?
cuboidal epithelium cells, similar to PCT
what epithelium are the thin limbs of the nephron loop?
simple squamous epithelium
what forms the distal convoluted tubule?
cuboidal epithelium, thinner than PCT
what is the role of the DCT?
fine tuning, regulated reabsorption
structure of the DCT?
few microvilli and no brush border
less mitochondria
What influences reabsorption in DCT?
aldosterone
What is the role of the collecting duct?
to collect filtrate from several DCTs which empty into the papilla
what influences reabsorption in collecting duct?
ADH and aldosterone
Structure of collecting duct?
wall of simple cuboidal epithelium
principal cells for reabsorption
intercalated cells for acid/base balance
how do you distinguish between proximal and distal convoluted tubule?
proximal has a fuzzy lumen due to microvilli and distal has a clear lumen
what is the juxtaglomerular apparatus?
specialised zone in every nephron located where DCT lies against afferent arteriole
What is the role of the macula dense cells?
chemoreceptors detect sodium levels
what is the role of the juxtaglomerular cells?
mechanoreceptors detect blood pressure
what does juxtaglomerular apparatus control?
glomerular filtration rate and blood pressure
