Microanatomy of Renal System Flashcards
What is the function of the Renal System
- Filter blood to form filtrate
- balances the composition and volume of blood , painting homeostasis of body fluid
How much of C.0 do kidneys receive
25%
Explain the gross anatomy of the renal system
1- paired kidneys
2- Paired ureters draining urine from kidneys
3- ureter drains into bladder
4- bladder holds urine until it’s passed through urethra
Where do Kidneys receive blood from and where is it drained
Receive blood from renal arteries coming from the abdominal aorta.
Drain blood into renal veins which drain into inferior Vena cava.
Where is the hilum of the Kidneys
At the medial borders of the Kidneys
Describe the anatomy of the kidney
- surrounded by CT capsule
- Multilobar ( 10-18 lobes )
- Every lobe has outer cortex and inner medulla with renal papilla at it’s apex
What is renal papilla
openings in the papillae will release urine to minor calyces
What are Calyces and what are their functions
- cup shaped sells at the end of renal papillae
- minor drain into major Calyces which drains into renal pelvis and then ureter
What is the histological appearance of the cortex
- dotty, granular appearance
What is the histological appearance of the medulla
- linear ,striated appearance
Name the functional unit of the Kidney and what it’s responsible for
Nephron. Responsible for Filtration, reabsorption and excretion.
Is loss of dysfunction of nephrons reversible
No
Histologically Describe a nephron
Blind-ending epithelial lined hollow tubule
What is the nephron composed of
1- Renal corpuscle ( bowman’s capsule & glomerulus )
2- Proximal convoluted tubule
3- Loop of Henle
4- Distal convoluted tubule
Which parts of the nephron are in the cortex and which are in the medulla
Cortex : PCT , Bowman’s capsule , glomerulus , part of DCT
Medulla : Loop of Henle , part of DCT
Where does the blood get into the nephron
From the glomerulus
Are the collecting ducts part of the nephron?
No , separate system
Describe the Renal Corpuscle
Blind ending part of nephron. Expanded spherical portion from proximal tubule is Bowman’s capsule.
What is Bowman’s capsule lined with
simple squamous epithelium
What is the glomerulus
A tuft of capillaries that where pushed into Bowman’s capsule during kidney formation
What is the glomerulus lined with
Parietal cells. Visceral epithelium from the Bowman’s capsule epithelium
What is the entry and exit point of the glomerulus called and what is it’s function.
The vascular pole where afferent and efferent arterioles bring blood into and out of the glomerulus. Blood enters via afferent and exits via efferent.
What is the exit point for filtrate called and what structures does it link
The urinary pole where filtrate drains from Bowman’s space into PCT
What are Podocytes
The cells that make up the blood filtration barrier
What is the anatomical difference between the afferent and efferent arterioles and What happens due to this difference.
The lumen of the efferent arteriole is smaller than the afferent arteriole. Means that blood exiting is under higher pressure since it has to pass through narrower lumen resulting in a bit of blood back up in the glomerulus.
Gives more time for blood to be filtered
What type of epithelium lines the glomerulus capillaries
Fenestrated Epithelium
What important feature is seen in the vascular pool
The Juxtaglomerular Complex.
What is the Juxtaglomerular Complex ( describe where it is and what it is composed of )
A portion of the DCT of the nephron sits at the afferent and efferent arteriole in the vascular pool. Between the DCT and arterioles and around the arterioles is the juxtaglomerular complex that is made of Juxtaglomerular cells and Macula dense.
What is the function of the Juxtaglomerular Complex
Assesses and monitors blood pressure and GFR
What is the macula densa and what is its function
Cells lining the DCT. Chemoreceptors monitoring the luminal sodium concentration and will adjust GFR if needed.
Explain what the macula densa does in detail
- Macula densa cells will signal cells in afferent arteriole wall called the juxtaglomerular cells
- will be signalled to secrete renin into the blood stream
- causes Angiotensin to be released
- results in vasoconstriction, increasing blood BP in efferent arteriole which allows blood to flow even slower in glomerulus
What are Lacis cells
Cells located between the two arterioles. Extraglomerular mesangial cells
What are Juxtaglomerular cells
Specialized smooth muscle cells of the tunica media in the afferent arteriole that secretes renin .
Describe the entire blood supply of the kidney (including the nephron )
1- Renal artery branches into interlobar arteries ( in between lobes ) which travels up to corticomedullary junction and then divided into arcuate arteries that runs between Cortex and medulla.
2-Arcuate artery will branch into interlobular artery that heads through cortex.
3- Interlobular artery branches into afferent arterioles that enter nephrons. Will branch into glomeruli capillaries that drain into efferent arterioles .
4-Efferent a. branches into peritubular capillaries which head down into the medulla , forming the vase recta surround the loop of henle and then draining into renal vein.
What capillaries take up what is being reabsorbed from he nephron
The peritubular capillaries
What is the blood-filtration barrier
The barrier in between the blood in glomerular capillaries and filtrate in Bowman’s space
What does the blood-filtration barrier consist of ( Hint: 3 things )
1- Fenestrated epithelium of glomerular capillaries
2- fused basal laminae (basement membrane of capillaries and podocytes )
3- Pedicles of podocytes ( part of the visceral epithelium )
How are the podocytes part of the blood-filtration barrier
- podocytes develop long processes that wrap around glomerular capillaries called primary processes.
- Secondary processes branch off of primary , aka pedicles. - - The pedicles make up the third layer of the blood-filtration barrier
What are filtration slits and what is their function.
Slits in between the secondary processes that through them the filtrate passes. Only allows solutes of particular size to pass from blood into bowman’s space.
What lines the PCT
simple cuboidal epithelium with long microvilli and basal invaginations
What’s the histologically presentation of PCT lumen
Cloudy / frothy looking due to long microvilli projecting into lumen.
What is the purpose of the PCT basal invaginations
Contain sodium complexes that help pump sodium out of cell and transport glucose and amino acids back into blood stream.
What’s the percentage of glomerular filtrate reabsorbed in PCT
70%
What happens in the PCT
Water, potassium , ions, glucose, amino acids and ions are reabsorbed into the peritubular capillary branches of the efferent arteriole
What are the two divisions in the loop of henle
Thick and Think portions
What lines the thin portion of Loop of henle
simple squamous epithelium
What lines the thick portion of Loop of henle
simple cuboidal epithelium
What is the vasa recta
Vessels branched from efferent arterioles that are parallel to the loop of Henle
What is the function of the Loop of Henle
Where the urine starts to be concentrated by the counter-current multiplies
What lines the DCT
simple cuboidal epithelium but no or few microvilli
What is the difference between histological presentation of PCT and DCT
- DCT has clearer lumen since there are less microvilli
- DCT is less convoluted
Why does DCT have few microvilli
there’s a little bit of reabsorption taking place but not much compared to PCT
What is the function of PCT
partially responsible for potassium , sodium , calcium and PH
What wraps around the DCT
Peritubular capillaries
What lines the collecting ducts
- simple cuboidal epithelium for collecting tubules and ducts
- columnar epithelium for ducts of Bellini
What is the function of the collecting ducts
Takes urine from DCT and collects it into collecting tubules , then into collecting ducts and then into ducts of Bellini at renal papilla
What are the Renal calyces
- lumen surround the renal papilla
What lines the Renal calyces
transitional epithelium , 2-3 cells thick
What’s the wall of the renal calyces made of and what is its function
well developed smooth muscle but not in distinct layers that preform the peristaltic contractions that promotes pushing of urine from papilla into calyces
What is the function of the ureters
Transport urine into bladder by peristalsis ( contraction )
What lines the ureter
Transitional epithelium
What is the shape of the ureter lumen
star shaped lumen ( stellate ) that expands
What’s deep to the ureter epithelium
Lamina propria with elastic fibres for stretching and Smooth muscle
What is the function of the bladder
Storage organ for urine and explosion of urine into urethra
What lines the bladder
Transitional epithelium 6-8 cells thick ( aka urothelium )
- speciallised cells called umbrella cells make up urothelium
What’s deep to the urothelium
Lamina propria with BV and fibroelastic CT. Followed by 3 indistinct layers of smooth muscle.
