Microscopic anatomy of the urinary tract Flashcards by Janina Wait

Describe the vascularisation of the kidney

Supplied by single branch of aorta (renal artery)
Splits into interlobar artery within kidney
Then arcuate artery
Then interlobar artery
Into vasa recta
Into arcuate vein, then interlobar vein and then renal vein out into caudal vena cava

How well did you know this?

Not at all

Perfectly

What is the reason for the gross appearance of cat kidneys?

The subscapular veins run towards the hilum of the kidney, givign a grooved appearance

How well did you know this?

Not at all

Perfectly

What is meant by end arteries?

Vessels that do not have anastomoses with a back up blood supply
Closed blood supply

How well did you know this?

Not at all

Perfectly

What is the relevance of end arteries to renal function?

Renal arteries are end arteries

- Damage to an artery will lead to a whole section losing its blood supply and dying off

How well did you know this?

Not at all

Perfectly

What is the nephron?

The functional unit of the kidney

How well did you know this?

Not at all

Perfectly

What is the nephron made up of?

The renal corpuscle (glomerulus)

- And the tubular system

How well did you know this?

Not at all

Perfectly

What are the components of the tubular system of the nephron? (in order)

Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Collecting duct (drains into pelvis)

How well did you know this?

Not at all

Perfectly

What components are found in the renal cortex

Proximal and distal convoluted tubues

- Glomeruli

How well did you know this?

Not at all

Perfectly

What components are found in both the inner and outer medulla of the kidney?

The thin loops of Henle

- Collecting ducts

How well did you know this?

Not at all

Perfectly

What is found in the outer medulla?

Straight proximal tubule (S3)
Thick ascending loop
Collecting ducts
Thin tubules
Vasa recta

How well did you know this?

Not at all

Perfectly

What is found in the inner medulla?

Collecting ducts
Thin tubules
Vasa recta

How well did you know this?

Not at all

Perfectly

What can be seen in the cortex of the kidney on histology?

Renal corpuscles
Convoluted tubules
Medullary rays

How well did you know this?

Not at all

Perfectly

Describe the glomerulus

Aka renal corpuscle
Vascular tuft/ capillary bundle
Fneestrated so filtrate drains out
Pressure difference between afferent and effect arteriole to facilitate filtration

How well did you know this?

Not at all

Perfectly

Which has higher pressure, the afferent or the efferent arteriole in the kidney?

The efferent

- Facilitates filtration through the glomerulus

How well did you know this?

Not at all

Perfectly

Describe Bowman’s capsule

Inner (visceral) layer made up of podocytes
Outer (parietal) layer
Not directly in contact with blood
Podocytes between vascular tuft and inner of capsule

How well did you know this?

Not at all

Perfectly

What are the filtration mechanisms found in the glomerulus?

Physical

- Electrical

How well did you know this?

Not at all

Perfectly

What is the function of the podocytes in Bowman’s capsule?

Filter to keep proteins in the blood

How well did you know this?

Not at all

Perfectly

What are the mesangial cells?

Mesothelium of the capillary tuft (glomerulus)

How well did you know this?

Not at all

Perfectly

What are the functions of the mesangial cells?

Properties of immune and smooth muscle cells
Assist filtration barrier
Provide structural support
Phagocytose foreign material

List the filtration apparatus of the glomerulus

Fenestrated capillary endothelium
Charge of the glomerular basement membrane (-ve charge, repels anions)
Podocytes
Physical action of glomerular basement membrane

How do podocytes act to filter the blood?

Have primary and secondary processes
Pedicels
Filtration slite between pedicels
Anything larger than slit will not pass through

Describe the structure of the proximal tubule

Made up of 3 segments
S1, S2, S3
S1,2 are convoluted, S3 is straight
Brush border
Basal striation
Interdigitation of basal processes
Infolding of basal cell membrane to increase SA

What is the function of the proximal tubule?

Majority of transport
Bulk absorption
Reabsorption from filtrate e.g. glucose

How does the proximal tubule carry out its function?

Enzymatic system

- Abundant Na/K ATPase

Why are there many mitochondria present in the proximal tubule cells?

- Reabsorption is an enzymatic process - Active process, lots of ATP needed - Mitochondria supply this ATP

What is the disadvantage of the enzymatic system in the proximal tubule?

- Can be overloaded - osmotically active substances can get into the loop of Henle - E.g. glucose

What are the different segments of the Loop of Henle? (in order)

- Thick descending limb - Thin segment - Thick ascending limb

What is the function of the loop of Henle?

- Concentration of urine

How does the Loop of Henle carry out its function?

- Countercurrent multiplier | - Water out of descending loop, ions out of the ascending loop

Describe the concentration of ions in the loop of Henle

- Increasing ion concentration down the loop, decreasing up the loop - 2 isotonic regions - Highest concentration of salts at the bottom of the loop

What is medullary wash out and how does this occur?

- Too much fluid | - Unable to produce concentrated urine

Describe the structure of the distal tubule

- Straight segment - Convoluted segment - Basal striation

What is the function of the distal tubule?

- Ion transfer | - Balances amount of water in teh body

How does the distal tubule carry out its function?

- Pumps sodium chloride - Controls K, Cl, Na to balance water - Isotonic solution of these ions

What is the juxtaglomerular apparatus?

- Terminal portion of straight distal tubule comes into contact with the afferent and efferent arterioles of its "own" glomerulus - Macula densa where in contact

What is the function of the juxtaglomerular apparatus?

Rate and concentration of sodium going past measured here

Describe the structure of the collecting ducts

- Inner medulla - Flat cylindrical cells - Each individual duct coalesces to a larger duct to open to renal papilla

What is the function of the collecting ducts?

- Bring urine together | - Alter amount of water in urine

How do the collecting ducts carry out their function?

- Use concentration gradient set up by loop of Henle | - ADH inserts aquaporins to allow more absorption into tissues

Where do the collecting ducts connect to the papilla?

- At area cribrosa of the papilla, into the renal pelvis

What is unique about the horse renal pelvis?

- Contain low numbers of mucus glands - Referred to as pelvis renalis and uretericae glands - Simple branched tubualveolar glands present in mucosa and produce viscous mucinous material

What is the vasa recta?

- Capillary network around the loop of Henle | - Reabsorbs water from interstitium and carries back to venous sytem

Describe the microscopic structure of the ureters

- Transitional epithelium - Thick, fibroelastic lamina propria - Upper 2/3rds smooth muscle, 2 layers inner (longitudinal) and middle (circular) - Lower 1/3rd only has outer longitudinal smooth muscle

What is the function of transitional epithelium?

- Stretchable and impermeable, can adjust to distension | - Can stretch until appears squamous

Describe the microscopic structure of the bladder

- 3 layers of smooth muscles - Transitional epithelium - Underlying mucosa heavily folded to accomodate volume changes - As expands, folds disappear

Describe the microscopic structure of the urethra

- Mainly transitional epithelium - Some parts with stratified epithelium - Erectile tissue in both sexes (endothelial lined vascular spaces)