Lecture 29: The Nephron Flashcards
What are the two types if nephrons called?
- cortical
- juxtamedullary
What type of nephron is the most abundent?
cortical
The name of nephrons is determined by what?
The location of the renal corpuscle
Where are the cortical nephrons located?
in the cortex
Where are the juxtamedullary nephrons located?
the renal corpuscle is in the cortex, next to the renal medulla but they extend deep into the medulla
Which type of nephron is important for making concentrated urine?
juxtamedullary
What are the three functions of the nephron?
- selectively filter blood
- return anything to be kept to the blood
- carry waste waste away for storage and expulsion
Each nephron is comprised of what three things?
- a glomerular capsule
- renal tubules
- a collecting duct
Each nephron is associated with what two capillaries?
- a glomerulus (glomerular capillaries)
- peritubular capillaries
The glomerulus/glomerular capillaries are specialised for what?
filtration
The wall of the glomerulus/glomerular capillaries is comprised of what type of epithelium?
fenestrated endothelial cells
Glomerulus/glomerular capillaries are fed and drained by what, and why?
arterioles (afferent and efferent)
in order to be able to control the pressure and flow of blood
Peritubular capillaries are specialised for
absorption
What do peritubular capillaries wrap around?
renal tubules
Peritubular capillaries carry filtered blood from what?
the efferent arteriole
The peritubular capillaries receive reabsorbed filtrate from the ________ and can secrete into the ________
nephron
nephron
The peritubular capillaries have extensions called _______ _______ which are located where?
vasa recta
deep in the medulla
Vasa recta are only found in which type of nephron?
juxtamedullary
What two things make up the renal corpuscle?
the glomerulus/glomerular capillaries and the glomerular capsule
The renal corpuscle is where the _____ and _______ meet and it the site of _________ ________
nephron
capillary
filtration barrier
What is the first part of the nephron called?
the glomerular capsule
The glomerular capsule is made up of what two layers? What cells are these two layers made of?
- Outer parietal layer of simple squamous epithelium
- inner visceral layer of podocytes
What is between the visceral and parietal layer of the glomerular capsule?
the capsular space
What is the purpose of the capsular space?
It is where what we take out goes first
Podocytes form the ______ layer of the glomerular capsule. These cells have branches which form intertwining foot processes called ______
visceral
pedicels
What are filtration slits?
gaps in between the pedicels
Where does the filtration barrier lie?
between the glomerulus/glomerular capillaries and the capsular space
What is the purpose of the filtration barrier?
to allow free passage of water and small molecules such as glucose and salts but to restrict the passage of most proteins and red blood cells
The filtration barrier is made up how many layers?
3
What are the layers that make up the filtration barrier?
- fenestrated endothelium of the glomerular capillary
- fused basement membrane
- filtration slits between the pedicels of the podicytes
Urine =
filtered - reabsorbed + secreted
After the glomerular capsule, what is the second part of the nephron called?
the proximal convoluted tubule (PCT)
Where does the bulk reabsorption take place?
in the PCT
Where is the PCT located?
in the cortex
What is the PCT surrounded by?
peritubular capillaries
What is the structure of the PCT?
- cuboidal epithelial cells
- dense microvilli (brush border) on the luminal membrane
- highly folded basolateral membrane
- many mitochondria for active transport
- leaky epithelium
What is the third part of the nephron called?
nephron loop
Where is the nephron loop located?
in the medulla
What is the nephron loop surrounded by?
the vasa recta (in juxtamedullary nephrons only)
What are the four parts of the nephron loop called and what epithelium is located here?
- thick descending limb: like the PCT
- thin descending limb: simple squamous epithelium
- thin ascending limb: simple squamous epithelium
- thick ascending limb: like DCT
The different areas of the nephron loop have different permeabilities to
water and sodium
What is the fourth part of the nephron called?
distal consulted tubule (DCT)
What is the structure of the DCT?
- cuboidal epithelium but thinner that the PCT
- few microvilli so no brush border
- fewer mitochondria
Reabsorption in the DCT is mainly regulate by what hormone?
aldosterone
What is the fifth part of the nephron called?
the collecting duct
Filtrate from several DCTs drain into one collecting duct which empty at the _______
papilla
Describe the structure of the collecting duct
- wall of simple cuboidal epithelium
Reabsorption in the collecting duct is mainly regulate by what hormones?
ADH and aldosterone
What are two different cuboidal cells in the collecting duct and what is the role of these two different cells?
principle cells: reabsorption
intercalated cells: acid/base balance
Where is the juxtaglomerular apparatus (JGA) located?
where the DCT lies against the afferent arteriole (looping around)
What are the specialised cells in the DCT that make up the JGA?
What are they and what is their role?
macula densa cells
these are chemoreceptors that detect Na (and therefore H2O levels)
What are the specialised cells in the afferent arteriole that make up the JGA?
What are they and what is their role?
juxtaglomerular cells
these are mechanoreceptors which can detect blood pressure
What does the JGA control the rate of?
glomerular filtration rate, ensuring the system is working at full capacity to stabilise blood pressure
