L 3: Renal histology and cell bio

Question 1

The outer area of the kidney is called the _____, inside of which is the ________ which contains 4-18 (avg 8) _______. The apex of each pyramid is called the _______ which empties into a ________.

Answer 1

-cortex -medulla -pyramids -papilla -calyx

Question 2

What is the defining feature of the cortex?

Answer 2

-glomerulus

Question 3

Question 4

Answer 4

1. glomerulus
2. interstitium
3. tubules
4. vessel

Question 5

9 segments of nephron and their function

Answer 5

1. proximal covoluted tubule: bulk reabsorption of filtrate (water, nacl, HCO3, AA, glucose, P, other ions
2. proximate straight tubule
3. thin descending LoH: allows of urinary concentration
4. thin ascending LoH: urine concentration
5. Thick ascending LoH: Na, K, Cl, reabsoprtion, K secretion, H+ secretion, urinary dilution, low water permeability; loop diuretics!
6. Distal convoluted tubule: Na and Cl reabsorption, involved in urinary dilution; thiazide diuretics!!
7. Connecting tubule
8. Cortical collecting tubule: secrete H+, reabsorb K, vasopressin inc water permeability; aldosterone action site
9. Medullary collecting duct, inner or outer: primary site of regulated urea and water transport involved in urine [], vasopressin inc water permeability

Question 6

Answer 6

• proximal tubule in cortex with BRUSH BORDER
• highly eosinophilic on PAS stained and lined by relatively tall cuboidal epithelium
• lots of mito!

Question 7

What does the PCT brushbprder show in EM? what else is readily seen?

Answer 7

• correspond to long apical microvilli which makes sense because need lots of SA for bulk reclamation
• see it full of mitochondria!!

Question 8

In addition to apical brush border, was does the PCT have on its basal side?

Answer 8

• extensive basal invaginations with lots of mito inbetween them
• lots of transport!!

Question 9

Answer 9

• membrane infolding top left
• mito
• bottom: brush border

Question 10

Answer 10

• left is PCT
• right: DCT

Question 11

PCT vs DCT on histology

Answer 11

-DCT: smaller diameter, open lumens, lower pale staining epithelium, no brush border

Question 12

Answer 12

• collecting tubules and LoH in medullary kidney
• cells of thin LoH (right) are lower and flattened w little cytoplasm, smaller diameter
• CT large diameter, prominent cytoplasm

Question 13

Answer 13

• cells of LoH: low and flattened
• low metabolic activity; simple structure, small diameter

Question 14

Answer 14

–At the center of each lobule is a medullary ray, containing tubules that are parallel to each other and oriented radially in the cortex. The tubules in the medullary rays are continuous with those in the medulla.

–medullary ray

Question 15

What is at the center of each lobule? What about the edges and why does this make sense?

Answer 15

• medullary ray is at the center of each lobule
• along the 2 edges of each lobule are glomeruli
• this makes sense bc a lobule comprises all glomerui that contribute urine to the collecting ducts within a medullary ray

Question 17

What are the components of the medullary ray?

Answer 17

-medullary ray includes the Proximal straight tubule (PST), Thick ascending limb (TAL), and Cortical collecting tubule (CCT).

Question 18

What is found in the central medullary ray and periphery of lobule?

Answer 18

• central: proximal straight duct, collecting duct, and and thick ascending LoH
• periphery: distal CT, PCT, arteries, glomerulus

Question 19

2 zones of medulla

Answer 19

• outer medulla which contains loop of henle from both types of nephrons
• inner: loops of henle only from juxtamedullary nephrons

Question 20

Which type of nephron has its glomerulus near the corticomedullary border?

Answer 20

-juxtamedullary nephron

Question 21

Renal vasculature

Answer 21

The renal artery enters the kidney at the hilum, near the ureter. Veins follow the same path as arteries, in reverse. The artery branches into interlobar arteries, which travel to the medulla-cortex border remaining outside the medullary pyramids, The vessels branch into arcuate
arteries (and veins) that follow the edge of the cortex. The arcuate arteries branch into interlobular arterioles that travel tangentially in the cortex at the edges of the lobules. Intralobular arterioles, feeding the glomeruli, branch off the interlobular arterioles at each renal corpuscle.

Question 22

Where does the afferent arteriole arise from?

Answer 22

-interLOBULAR artery –> intralobular –> afferent arteriole

Question 23

Fates of efferent arteriole depends on _____.

Answer 23

-type of glomerulus involved

-Those of the superficial glomeruli supply the
capillary plexuses of the cortical labyrinth and the medullary rays. Thus, this supplies proximal and distal tubules, and some parts of the collecting ducts. The efferent arterioles of the juxtamedullary golmeruli descend into the medulla and form the descending vasa recta
which supply the adjacent capillary plexuses. The special disposition of the loops of Henle descending and ascending branches, in parallel
to the vasa recta and coupled with specific transport and permeability properties allow them to operate as “countercurrent multipliers”
creating a gradient of extracellular fluid tonicity in the medulla. This in turn is used to modulate urine tonicity and volume

Question 24

podocytes

Answer 24

• epithelial cells that surround glomerular basement membrane
• branch and interdigitate that provide structural support to capillaries and play important role in filtration (visceral layer)
• continuous with epithelial cells lining Bowmans capsule (parietal layer)

Question 25

Type of endothelium in glomerular capillaries

Answer 25

• fenestrated: block exit of cells but allow free flow of plasma
• contain anions

Question 26

Answer 26

1. endothelial cell
2. fenestrations
3. GBM
4. podocytes

Question 27

3 sieves of the glomerulus

Answer 27

1. fenestrated endothelium
2. GBM
3. podocytes

Question 28

What do we call the glomerular filtration barrier?

Answer 28

• connect foot processes to GBM and eachother across the SLIT DIAPHRAGM complex
• nephrin proteins

Question 29

Mesangial cells

Answer 29

• located between capillaries, under BL but outside capillary lumen
• no BL between them and endothelial cells
• phagocytic and have contractile properties; maintain BM

Question 30

3 ways kidney is an endocrine organ

Answer 30

1. 1,25 Vit D3 to maintain circulating calcium and phosphate levels
2. renin which increases extracellular fluid volume and maintains BP
3. Epo

Question 31

Steps of Vit D3 active synthesis

Answer 31

• 7-dehydrocholestrol + UV= Vit D or Vit D through diet
• then goes to liver to become 25-hydroxyVit D
• PT kidney to become 1,25 Vit D3
• promotes uptake of Ca from intestine

Question 32

Where does Vit D3 active formation occur?

Answer 32

-proximal tubule in kidneys

Question 33

Renin is secreted by the juxtaglomerular apparatus. Name the 3 components and their function

Answer 33

1. JG cells: secrete reninl found in afferent arteriole
2. macula densa (distal CT that sense salt)
3. Lacis cells: unknown

Question 34

Answer 34

• left is JG cells
• right is macula densa

Question 35

What cells make EPO?

Answer 35

• renal cortical interstitial cells
• exist between tubular cells of the cortex

Question 36

Answer 36

renal cortical interstitial cells that make EPO

-exist between tubular cells of cortex

Question 37

EPO regulation

Answer 37

• regulated by HIF (hypoxia inducible factor)
• normoxic: HIF constitutively -OH by PHD. Causes VHL to bring and degrade HIF
• hypoxic: HIP is not -OH and thus VHL doesnt bind to degrade it, so HIF can bind HRE and translate EPO gene