HISTO of the Kidney Flashcards
What composes the urinary system?
The Kidneys & the urinary tract
What is at the apex of every renal pyramid?
The renal papilla
Where does the transitional epithelium begin?
@ the renal papilla
What are the functions of the kidney?
Filtration
Reabsorption/Excretion
Synthesis of Renin & Erythropoietin
Activation of Vitamin D3
What forms the corticomedullary border?
15-20 renal lobes or pyramids
About how many collecting ducts drain into each renal papilla?
about 20
Where are glomeruli located?
In the cortex
Where are cortical labryinths located?
In the cortex
Where are medullary rays located?
In the cortex
What makes up a kidney lobe?
Medullary pyramid + overlying cortex
What makes up a kidney lobule?
Group of nephrons that open into the same collecting duct…medullary ray is in the middle & interlobular arteries are on both side.
What composes the nephron? What is its function?
Glomerulus + PCT + Loop of Henle + DCT
Filtration, Excretion, Reabsorption
What composes the renal corpuscle?
Nephron + Bowman’s Capsule
Which blood vessels separate the cortex from the medulla?
The arcuate vein & artery.
What is the functional unit for producing urine?
Uriniferous Tube
This is composed of the nephron & the collecting duct.
What is the area cribrosa?
holes…located at the end of the renal papilla.
Where are the renal corpuscles located for juxtamedullary nephrons?
In the cortex.
What is the order of the arteries beginning w/ the interlobar arteries?
Interlobar arteries give rise to: arcuate arteries
Arcuate arteries give rise to: Interlobular arteries
Interlobular arteries give rise to: afferent arteriole
What are the 3 different kinds of capillary networks?
Normal: arteriole to capillary to venule
Arterial Portal System: afferent arteriole to capillary to efferent arteriole to capillary to venule (in the kidney)
Venous Portal System: arteriole to capillary to vein to capillary/sinusoid to vein
Where do you see the arterial portal system? Where do you see the venous portal system?
Arterial: kidney
Venous: liver & pituitary
What is the general purpose of a portal system?
It slows things down so that filtration can be separated from absorption.
In the arterial portal system where do you go after the efferent arteriole?
Peritubular capillaries…then venule…interlobular vein…arcuate vein…interlobar vein & out.
What covers the glomerulus?
Visceral layer of epithelium w/ podocytes
What makes up the outside layer of the Bowman’s Capsule?
The parietal layer of epithelium: considered mesothelium.
Where does the glomerular filtrate go after it comes thru the arterioles?
Released into the Bowman’s Space
What are the 2 poles of the Renal Corpuscle?
The vascular pole (where the afferent & efferent arterioles are & the juxtaglomerular apparatus is)
180 degrees later…
The Urinary Pole (where the glomerular filtrate drains into the PCT)
What are the 3 components of the juxtaglomerular apparatus?
macula densa (a part of the DCT)
Extraglomerular mesangial cells (b/w the arterioles)
Juxtaglomerular cells
What lies on the inside of the visceral wall of the renal corpuscle?
Mesangial Matrix.
Here are the mesangial cells.
What do mesangial cells that are located in the matrix do?
Secrete Extraceullar Matrix
Secrete Cytokines
Secrete Prostaglandins
Secrete Endothelins (can induce capillary constriction)
Have phagocytic activity
**contract & regulate blood flow thru the capillaries & therefore regulate glomerular filtration.
Are there basement membranes in the layers of the Bowman’s Capsule?
Yes.
Visceral Wall has a basement membrane made up of the fusion of the basal laminae of the endothelium & the podocytes
Parietal Wall has a basement membrane that faces outside of the capsule.
Which cells are the macula densa cells in contact with?
The extraglomerular mesangial cells.
What do the sympathetic fibers innervate in the nephron?
The afferent arteriole…this firing will cause the release of renin.
Where is the urinary space?
it is the area b/w the visceral wall & the parietal wall.
What is the relationship b/w the visceral & parietal walls of the renal corpuscle?
They are opposing, but continuous. Like an invagination.
Where are the fenestrations in the renal corpuscle?
In the visceral wall!! This way you get your filtrate into the urinary space.
What is another name for the parietal wall?
The Bowman’s Capsule
Where is the location of the juxtaglomerular cells?
These are modified smooth muscle cells in the tunica media of the afferent & efferent arterioles.
histologically…can you tell the difference b/w the afferent & efferent arterioles? B/w the arterioles & venules?
Can’t tell the difference b/w the afferent & efferent arterioles.
You CAN tell the difference b/w an arteriole & a venule.
What are the 3 layers of the basal laminae on the visceral wall side?
Capillary Side: Lamina Rara Interna
In the middle a very thick: Lamina Densa
Visceral Layer Side: Lamina Externa
Does the body of the podocytes face the inside of the glomerulus or the urinary space?
The urinary space.
Explain the arrangement of the podocytes on the visceral wall.
The podocytes have primary processes & secondary processes called pedicels.
The pedicels interdigitate. B/w them is the filtration slit covered in a thin filtration diaphragm.
What does the lamina rara catch? The lamina densa?
Lamina Rara catches negatively charged molecules & stiff molecules that can’t be deformed
Lamina Densa catches large molecules.
What is the fluid called that gets into the urinary space?
Glomerular Ultrafiltrate
How does the basal laminae keep from getting clogged? How does the basal laminae keep from getting eaten alive?
Intraglomerular Mesangial Cells phagocytize the clogs.
Podocytes & glomerular endothelial cells replenish the basal laminae.
What are mesangial cells derived from?
Mesoderm, not bone marrow
What’s the basic order of the structures that separate the capillary from the urinary space?
Capillary Side Endothelium that is fenestrated Basal Lamina (3 layers) Podocytes (w/ filtration slits) Urinary Space Side
What is found b/w the secondary processes of podocytes (aka pedicels)?
Filtration Slits.
Note: the pedicels are connected by a filtration slit diaphragm composed of nephrin.
The nephrin is connected to the actin filaments of the podocytes w/ a protein called CD2AP
What types of molecules can get thru the fenestrae of the endothelium? Which types can’t? Why?
Can get in: water sodium urea glucose small proteins Can't get in: large anionic protein B/c blocked by an anionic coat of negatively charged glycoproteins (heparan sulfate).
What types of molecules make up the basal lamina? What about it also slows down the anionic molecules?
Type IV collagen
Laminin
Fibronectin
proteoglycans (w/ lots of heparan sulfate)
** the heparan sulfate is why it is hard for anionic molecules to get thru here too.
T/F The pedicels also have an anionic coat, making it difficult for large anionic proteins to make it thru.
True
What happens when there is a mutation in the gene encoding nephrin?
Congenital Nephrotic Syndrome
Causes massive proteinuria (leakage of albumin in the urine)
Causes edema.
What type of epithelium is found in the proximal convoluted tubule?
simple cuboidal epithelium
What type of stain can you use to see a PCT?
eosin stain; PCT is eosinophilic
What are some important features of the PCT that help you to identify it on a histo slide?
simple cuboidal epithelium eosinophilic striated border of microvilli have an irregular lumen **look fuzzy.
What types of substances & % are reabsorbed @ the PCT back into the blood thru the peritubular capillaries?
Gradient created thru reabsorption of glucose & salt.
70% of water is reabsorbed.
Amino acids & proteins, & HCO3- are also reabsorbed here.
What types of substances does the PCT try to keep pushing thru into the urine?
organic solutes
drugs
toxins
creatinine
What are the 3 things in the PCT that help fcn w/ protein reabsorption?
apical canaliculi
vesicles
vacuoles
What molecules are reabsorbed in the PCT via the paracellular pathway?
This pathway causes reabsorption b/w cells. Molecules that use this pathway include: H20, Ca++, K+,
What molecules are reabsorbed in the PCT via the transcellular pathway?
This pathway causes reabsorption thru cells.
Molecules that use this pathway include: H20, glucose, peptides
Which side of the PCT is the Na+/H+ exchanger on? What ends up in the urine then?
the luminal side.
H+ ends up in the lumen.
Which side of the PCT is the sodium potassium pump on? What ends up in the blood then?
The side next to the capillaries. Na+ ends up in the blood.
Explain the importance of the basal ridges of the PCT.
These are infoldings of the plasma membrane on the side of the PCT that is closest to the capillaries. They have a ton of mitochondria, which help supply the energy for the sodium potassium pump to get sodium back in the blood. These basal ridges interdigitate which help lock cells together.
Aside from interdigitating basal ridges…what helps connect the cuboidal epithelial cells of the PCT?
Tight Jcns.
How can you tell the vasa recta from the thin limbs of the loops of Henle?
The vasa recta have RBCs inside.
What types of epithelium are the thin limbs of the loops of Henle made of?
Simple Squamous Epithelium.
What is the difference in permeability of the thin descending limb of the loop of Henle & the thin ascending limb of the loop of Henle?
Descending limb: Permeable to H20
Ascending Limb: slightly permeable to H20
Where are the interstitial cells located in a nephron?
They span the space b/w the loop of Henle & the vasa recta.
T/F All of the DCT have macula densa cells.
False. Only @ the JG apparatus.
What is the function of the macula densa cells in the DCT & what are its characteristics?
Fcn:
monitor filtrate for salt…as a part of the JG apparatus.
Characteristic:
tall, narrow cells.
What 2 substances can be secreted into the lumen of the DCT?
potassium
hydrogen ions
What is the DCT sensitive to?
Aldosterone. Can actively resorbe Na & passively absorbe Cl
What makes up the cortical labyrinth?
the region of the cortex w/ glomeruli & PCT & DCT
Explain the nuclei of the thin portions of the loop of Henle.
They are bulging into the lumen.
Where is the JG apparatus located in terms of poles?
@ the vascular pole of the nephron
How does the structure of the DCT compare to the structure of the PCT?
It lacks a brush border. It has a smooth lumen.
It has a wider lumen.
It has shorter simple cuboidal epithelium than the PCT.
T/F the distal convoluted tubule is impermeable to water.
True.
T/F DCT, like the PCT has abundant lysosomes & tubulovesicular structures.
False. It doesn’t have these structures.
T/F The DCT, unlike the PCT, doesn’t have any microvilli or basal mitochondria.
False. It does have these structures. It’s just that its microvilli are more sparse. They don’t have a brush border.
What are JG cells? Where are they located? How does their size compare to normal smooth muscle cells?
They are modified smooth muscle cells, larger than normal smooth muscle cells, that are a part of the JG apparatus & that secrete renin. They are located mainly in the afferent arteriole, but also partly in the efferent arteriole.
What happens when JG cells are triggered by sympathetic nerve fibers? What NT accomplishes this?
They secrete renin.
NE or dopamine.
What are the 3 components of the juxtaglomerular apparatus?
Macula densa cells (of the DCT)
The JG cells (mainly in the afferent arteriole)
extraglomerular mesangial cells
What is the basic deal w/ the sensing of sparse salt in the filtrate by the macula densa cells & the secretion of renin by the JG cells?
The macula densa cells & the JG cells somehow communicate. The extraglomerular mesangial cells are thought to be a part of this communication process.
JG cells are connected thru gap jcns.
Extraglomerular mesangial cells are connected thru gap jcns & are perhaps connected to the JG cells thru gap jcns, too.
Although Highi doesn’t necessarily buy it, what is the reaction of extraglomerular mesangial cells to ang II?
Contraction.
T/F The collecting ducts have a different embryological origin than the nephrons.
True.
What type of epithelium lines the collecting ducts? What are the 2 specialized cell types found here?
Simple Cuboidal Epithelium.
Principal cells
intercalated Cells.
Which are more prevalent in the collecting duct–principal or intercalated cells?
Principal Cells
How do the 2 main cells that make up the collecting duct differ in their staining?
Principal Cells: stain light.
Intercalated Cells: stain dark.
T/F Cortical collecting ducts are found only in the medullary rays.
False. They are also sometimes found in cortical labryinths.
When do you stop seeing the intercalated cells in the collecting ducts?
You see them in the cortical collecting ducts & in the medullary collecting ducts in the outer medulla. By the time you get to the inner medulla you don’t see the intercalated cells anymore.
When do you stop seeing the principal cells in the collecting ducts?
You stop seeing them when you get to the papillary collecting ducts. Here: they have a simple columnar epithelium w/ a single cilium that lines them.
Aside from staining light, what are other characteristics of the principal cells in the collecting ducts?
They have a round central nucleus & a single central cilium. They have less abundant mitochondrial in their basal cytoplasm.
Aside from staining dark, what are other characteristics of the intercalated cells in the collecting ducts?
They have microplicae (folds) on their apical surface & they have apical cytoplasmic vesicles. They also have abundant mitochondria in their cytoplasm. They have distinct lateral cell borders.
What is the fcn of the principal cells?
W/ the presence of ADH–they reabsorb water into the blood.
W/o ADH: urine doesn’t have a lot of solute & is large in volume.
What is the fcn of the intercalated cells?
put H+ in the urine, put HCO3- in the urine, put potassium back into the blood.
How much urine do you produce a day? How is this possible when you have 180 L of glomerular filtrate per day?
1.5-2 L per day.
Condensed by PCT, DCT, & CT.
T/F the collecting ducts are a part of the nephron.
False. They are only a part of the uriniferous tubule.
What is another name for mesangial cells?
Lactis cells
What are the ducts of Bellini?
The papillary collecting ducts.
Where does the transitional epithelium begin?
@ the renal papilla/ minor calyces.
What are the layers of the ureter in the upper part of the tract? From inside to outside?
Stellate Lumen Transitional epithelium (urothelium) Fibroelastic Lamina Propria (made of collagen & elastic fibers--allows stretch) Inner longitudinal smooth muscle outer circular smooth muscle Adventitia
What are the layers of the ureter in the lower part of the tract? From inside to outside?
Stellate Lumen Transitional Epithelium (urothelium) Fibroelastic Lamina Propria (made of collagen & elastic-great for stretch) Inner Longitudinal Smooth Muscle Middle Circular Smooth Muscle Outer Longitudinal Smooth Muscle Adventitia
What does the ureter layers lack?
NO muscosal or submucosal glands.
No submucosa.
NO muscularis mucosae
What does the ureter have (mucosa talk)?
Mucosa (epithelium & lamina propria)
Muscularis Externa
Serosa (adventitia) SOMETIMES
When does the transitional epithelium of the ureter look like transitional & when does it not?
It does look this way when there is contraction & not distention. It doesn’t look this way when there is distention. Gets rid of the dome shape.
Why is it important that the ureter be distensible?
For continuous flow
For the accommodation of kidney stones
What is a unique feature of the relationship b/w the cells of the urothelium of the urinary bladder?
They slide over each other like plates.
What are the layers of the urinary bladder? Starting from the lumen outward…
Lumen Transitional Epithelium (urothelium) Fibroelastic Lamina Propria Inner longitudinal smooth muscle layer Middle circular smooth muscle layer Outer longitudinal smooth muscle layer Adventitia (fibroelastic)
What is different about the adventitial layer of the urinary bladder on its superior surface?
Here it isn’t considered adventitia, but is considered serosa b/c of the peritoneum that covers it after the adventitia.
What is one possible explanation for why females have a higher rate of urinary tract infections than males?
The female urethra is much shorter. There is also a short distance b/w the urethra & anus in females. The bacteria don’t have a very long journey to the urinary bladder & their dream of infection.
How does the epithelium transition in the female urethra as you move from the top to the opening?
Near Bladder
Transitional
Pseudostratified & Stratified Columnar
Stratified Squamous non-keratinized @ the end
What are the 3 sections of the male urethra? What do they represent in terms of epithelium?
Prostatic Urethra: Transitional
Membranous Urethra: Pseudostratified & stratified columnar
Penile Urethra: Stratified squamous non-keratinized.
What are 2 characteristics (not the epithelium) that both male & female urethras share?
vascular fibroelastic lamina propria
urethral glands
What are the urethral glands called in males?
Glands of LIttre
What is the purpose of the urethral glands?
They lubricate the 2 surfaces of the urethra so they don’t stick together.
What composes the 2 sphincters of the urethra?
Inner Sphincter: inner longitudinal; outer circular smooth muscle layers
Outer Sphincter: skeletal muscle (voluntary control).
