Urinary/renal systems 2 Flashcards
How many nephrons are there in each kidney
Approx. 1 million
What are the two types of nephrons
Cortical nephrons - 85%
Juxtamedullary nephrons
What is the main different between the two types of nephrons
Cortical lies mainly in cortex and Juxtamedullary extends deep into the medulla
What is the juxtamedullary nephrons important for
Formation of concentrated urine
What are the functions of the nephron
Selective blood filtering
Return anything to be kept to blood
Carry waste away for storage and expulsion
What is each nephron comprised of
Glomerular capsule
Renal tubules
Collecting duct
What is each nephrons associated with
Glomerulus
Peritubular capillaries
Describe glomerular capillaries (what makes up glomerulus)
Thin walled single layer of fenestrated endothelial cells - specialised for filtration
What do arterioles do for glomerular capillaries
Feed and drain them
Describe where peritubular capillaries are
Wrap around renal tubules - specialised for absorption
What do peritubular capillaries do
Receive reabsorbed filtrate from nephron
Some non-filtered solutes needing to be excreted can pass into nephrons
What are vasa recta
Extensions that follow loops of Henle deep into medulla - only in Juxtamedullary
Describe the renal corpuscle
The glomerulus enclosed by the glomerular capsule - where capillary and capsule meet - filtration barrier
What are the two layers of the glomerular capsule (Bowman’s)
Outer parietal - simple squamous
Inner visceral - podocytes
What is between the two layers of the glomerular capsule
Capsular space - receives filtrate
Where are podocytes located
Surrounding the glomerular capillaries
Describe podocytes
Very branched specialised epithelium - forms intertwining food processes - pedicles
What forms between Pedicels
Filtration slits - Filtered blood moves through and passes into capsular space
Describe the filtration barrier
Between blood and capsular space
What does and doesn’t the filtration barrier allow through
Allows free passage of water and small molecules
Restricts most proteins and RBC (not filtered into nephron)
What are the three layers of the filtration barrier
Fenestrated endothelium (glomerular capillary) Fused basement membrane Filtration slits between pedicels of podocytes
Is everything that’s filtered secreted
No
What happens after filtration
Urine is waste fluid
Solutes filtered from blood
Some filtrate reabsorbed
Some not unfiltered secreted into nephron
What does urine equal
Urine = filtered - reabsorbed + secreted
What does the Proximal convoluted tubule (PCT) do
Bulk absorption - surrounded by peritubular capillaries
Describe the structure of the Proximal convoluted tubule (PCT)
Cuboidal epithelial Dense microvilli on luminal membrane Highly folded basolateral membrane Lots of mitochondria Leaky epithelium
Where is the nephron loop located
Loops down into medulla
Surrounded by vasa recta (juxtamedullary)
What is the length of the nephron loop important in
Production of dilute/concentrated urine
Describe the structure of the nephron loop
Thick descending and ascending limb - Similar to DCT structure
Thin descending and ascending limb - Simple squamous epithelium
Why are different area of the nephron loop different thicknesses
So they can have different permeabilities to water and sodium
Describe the distal convoluted tubule (DCT)
Fine tuning
Cuboidal epithelium - thinner than PCT
Describe the structure of the distal convoluted tubule (DCT)
No brush boarder (few microvilli)
Fewer mitochondria
What is reabsorption in the DCT mostly influenced by
Aldosterone - hormone
Describe the collecting duct
Fine tuning
Filtrate from several DCT’s into one collecting duct
Where do collecting ducts empty
At the Papilla
Describe the structure of the collecting duct
Simple cuboidal epithelium
What are the two main cells in the collecting duct
Principle - reabsorption
Intercalated - Acid/Base balance
What is the juxtaglomerular apparatus (JGA)
Specialised zone in every nephron - located where DCT lies against afferent arteriole
What are the specialised cells in the DCT of the juxtaglomerular apparatus (JGA)
DCT - Macula densa cells - chemoreceptors (sodium levels)
What are the specialised cells in the DCT of the juxtaglomerular apparatus (JGA)
Afferent arteriole - Juxtaglomerular cells - Mechanoreceptors (blood pressure
