Lecture 35: Renal System Microanatomy

Question 1

what anatomical structures make up the renal system

Answer 1

• 2 kidneys
• 2 ureters
• bladder
• urethra

Question 2

what is the function of the kidneys

Answer 2

filter the blood to form filtrate

Question 3

how many lobes does a kidney have

Answer 3

10-18 lobes (multilobar)

Question 4

what is each lobe of the kidney divided into

Answer 4

• outer cortex

- inner medulla w/ renal papilla (apex)

Question 5

describe how urine passes from papillae to medulla

Answer 5

papillae –> minor calyces –> major calyces –> renal pelvis –> ureter

Question 6

how can you distinguish between cortex and medulla histologically

Answer 6

• cortex appears more granulated

- medulla appears more striated

Question 7

why does the cortex appear more granulated histologically

Answer 7

rounded shape of renal corpuscles

Question 8

what is the renal corpuscle comprised of

Answer 8

• Bowman’s capsule

- glomerulus

Question 9

what structures make up the nephron

Answer 9

• renal corpuscle
• proximal convoluted tubule
• loop of Henle
• distal convoluted tubule

Question 10

what is the role of the nephron

Answer 10

functional unit of the kidney responsible for filtration, reabsorption, and excretion

Question 11

why is it important that each kidney has so many nephrons (1.5million)

Answer 11

loss or dysfunction of a nephron is irreversible

Question 12

name the two epitheliums of the Bowman’s capsule

Answer 12

• parietal (outer)

- visceral (inner, in contact with glomerulus)

Question 13

what specialised cell type makes up the visceral epi of Bowman’s capsule

Answer 13

podocytes

Question 14

through which vessel does blood enter glomerulus

Answer 14

afferent arteriole

Question 15

through which vessel does blood exit glomerulus

Answer 15

efferent arteriole

Question 16

describe the significance of the efferent arteriole lumen being narrower than the afferent arteriole

Answer 16

• blood can’t leave glomerulus as fast as it enters
• causes blood to back up in the glomerulus
• increases the pressure of blood entering the glomerulus
• increased filtration

Question 17

what cells make up the juxtaglomerular complex/apparatus

Answer 17

• macula densa
• juxtaglomerular cells
• lacis cells

Question 18

what is the role of the macula densa in the juxtaglomerular apparatus

Answer 18

• chemoreceptor cells of DCT

- sensitive to Na+ conc.

Question 19

describe the role of the juxtaglomerular cells in juxtaglomerular apparatus

Answer 19

• specialised smooth muscle in tunica media of AA
• secrete renin that induces release of ang2
• causes constriction of EA which adjusts GFR

Question 20

describe the blood supply to the nephron

Answer 20

renal artery

• -> interlobar a.
• -> arcuate a.
• -> cortical radial/ interlobular a.
• -> afferent arterioles
• -> glomeruli
• -> efferent arterioles
• -> peritubular/intertubular caps
• -> venous return (parallels arterial flow)

Question 21

what does the blood-filtration barrier consist of

Answer 21

• fenestrated endothelium of glomerular caps
• fused basal laminae
• pedicles of podocytes

Question 22

describe the structure of a podocyte

Answer 22

• nucleus
• primary processes
• secondary processes
• filtration slits

Question 23

describe the lining of the PCT

Answer 23

• simple cuboidal epi
• numerous microvilli
• basal invaginations w/ sodium complexes

Question 24

function of the PCT

Answer 24

• reabsorb water, K+, ions, glucose, a.a. etc

Question 25

at what part of the nephron does most glomerular filtrate get reabsorbed

Answer 25

PCT - 70%

Question 26

describe the lining of the loop of Henle

Answer 26

• thin portion lined by simple squamous epi

- thick portion lined by simple cuboidal epi

Question 27

what is the function of the loop of Henle

Answer 27

special permeability properties for concentrating urine by counter current multiplier

Question 28

what vessels are parallel to loop of Henle

Answer 28

vasa recta branches of efferent arteriole

Question 29

describe the lining of the DCT

Answer 29

cuboidal cells w/ few/no microvilli

Question 30

which is more convoluted; PCT or DCT

Answer 30

PCT

Question 31

what vessels wrap around the DCT

Answer 31

peritubular/intertubular caps from efferent arteriole

Question 32

describe the lining of the collecting ducts

Answer 32

simple cuboidal/columnar epi

Question 33

outline the flow of filtrate through the CD

Answer 33

collecting tubules

• -> collecting ducts
• -> ducts of Bellini
• -> deliver urine to papillae

Question 34

describe the lining of the renal calyces and renal pelvis

Answer 34

lined by transitional epi (2-3 cells thick)

Question 35

do the renal calyces and renal pelvis contain muscle, why

Answer 35

yes

peristaltic contractions (smooth muscle) promote emptying of tubules into the calyces

Question 36

what is the function of the ureters

Answer 36

transport urine to the bladder by peristalsis

Question 37

describe the lining of the ureters

Answer 37

transitional epi (4-5 cells thick) w/ underlying lamina propria containing elastic fibres

Question 38

describe the lumen of the ureter

Answer 38

stellate

Question 39

describe the smooth muscle in the ureter vs renal pelvis

Answer 39

Renal Pelvis:

• well developed
• ill defined layers

Ureters:

• well developed
• ill defined layers EXCEPT
• better defined in distal end where there is an extra layer of longitudinal fibres

Question 40

what is the function of the bladder

Answer 40

reservoir for both storage and expulsion of urine into the urethra

Question 41

describe the lining of the bladder

Answer 41

• transitional epi (6-8 cells thick when contracted)
• can be called urothelium
• specialised cells called umbrella cells

Question 42

other than lining, describe the wall of the bladder histologically

Answer 42

• underlying lamina propria w/ bv and fibroelastic CT

- smooth muscle –> 3 large distinct layers