Renal histology

Question 1

4 functions of the kidney

Answer 1

Filters blood to remove waste
Regulates water, salt and acid-base balance
Regulates blood pressure
Produces key hormones and enzymes

Question 2

Nephron

Answer 2

Functional unit of the kidney
1 million per kidney
Blood filter attached to tubular epithelium
Drain to collecting ducts

Question 3

Loop of Henle segments

Answer 3

Proximal convoluted tubule
Thin descending limb
Thin ascending limb
Thick ascending limb

Question 4

Tubular segments from renal corpuscle to collecting duct

Answer 4

Renal corpuscle
Proximal convoluted tubule
Proximal straight tubule
Thin descending limb
Thin ascending limb
Thick ascending limb
Distal convoluted tubule
Connecting tubule
Collecting duct

Question 5

Where does blood filtration occur?

Answer 5

Renal corpuscle

Question 6

Where is most of the filtrate volume reabsorbed?

Answer 6

Proximal tubule

65%

Question 7

Renal corpuscle

Answer 7

Capillary tuft (glomerulus) surrounded by podocytes
Urinary space between membrane and glomerulus
Outside layer formed by parietal squamous epithelial cells

Question 8

Poles of renal corpuscle

Answer 8

Vascular: where the afferent arteriole enters the capsule and the efferent arteriole leaves the capsule
Urinary: where the proximal tubule leaves the capsule

Question 9

Podocytes

Answer 9

Specialised visceral epithelial cells around the edge of the capillary tuft
Foot processes

Question 10

Three major components of the glomerular filtration barrier

Answer 10

Endothelium
Glomerular basement membrane
Podocytes

Question 11

Glomerular filtration barrier

Answer 11

Physical, change-selective barrier to restrict cells, albumin and other large proteins from entering
Consists of fenestrated glomerular capillaries enveloped by podocytes sending out large primary processes with smaller secondary (foot) processes interwoven across the top, forming filtration slits between them

Question 12

Glycocalyx coat

Answer 12

Found on glomerular capillary endothelium, leaky

Negatively charged to repel proteins

Question 13

Glomerular basement membrane

Answer 13

Thick physical and charge barrier

Made of dense core with outer layer or collagen and negatively charged proteoglycans

Question 14

Slit membrane

Answer 14

Fine filter made by interwoven podocyte foot processes covered in glycocalyx coat

Question 15

Podocyte effacement

Answer 15

Foot processes aren’t clearly interwoven so slit membrane isn’t formed, leading to leaky glomerular filter

Question 16

Mesangial cells

Answer 16

Smooth muscle cells packed into capillary tuft, giving support and slight contraction
Produce extracellular matrix and involved in glomerulosclerosis

Question 17

Glomerulosclerosis

Answer 17

Glomerular scarring

Mesangial cells proliferate and deposit ECM inappropriately causing stiffness and a scar

Question 18

Juxtaglomerular apparatus

Answer 18

Includes JG cells, macula densa cells and extraglomerular mesangial cells
Perform tubuloglomerular feedback and low tubular NaCl induced renin release

Question 19

JG cells

Answer 19

Juxtaglomerular cells
Modified smooth muscle cells in the wall of afferent arterioles
Secrete renin in response to low NaCl concentration

Question 20

Macula densa cells

Answer 20

Specialised cells in the wall of the thick ascending limb that sense NaCl concentration (as a proxy for flow) and in response vasoconstrict the afferent arteriole

Question 21

Proximal tubule cells

Answer 21

Cuboidal epithelium
Prominent brush border to increase surface area for transporters
Lateral processes and infoldings to increase surface area
Carry out pinocytosis

Question 22

Thin limb cells

Answer 22

Thin squamous epithelium
Water reabsorption
Nuclei bulge into lumen

Question 23

Distal tubule cells

Answer 23

Fine tuning salt, pH and urine concentration
Cuboidal epithelium
Interwoven lateral processes and infoldings
No brush border, just short microvilli
Doesn’t carry out pinocytosis

Question 24

Collecting duct

Answer 24

Final modifier of water, salt and urine pH

Cuboidal to columnar epithelium

Question 25

Medullary ray

Answer 25

Visible tubules in parallel at the centre of a lobule Only seen in the cortex Contain collecting duct and proximal and distal tubules

Question 26

Renal papillae

Answer 26

Apex of medullary pyramid

Question 27

Structures in the cortex

Answer 27

Renal corpuscle Proximal tubule Some distal tubule

Question 28

Structures in the medulla

Answer 28

Collecting ducts | Loop of Henle

Question 29

Outer renal corpuscle blood supply

Answer 29

Efferent arteriole forms peritubular capillary bed Interlobar ---> arcuate ---> interlobular Venous return opposite way

Question 30

Deep renal corpuscle blood supply

Answer 30

Long straight vessels (arterial vasa recta) bundled together with collecting duct and loops of Henl Branch to capillary beds around loops Venous return via bundled venous vasa recta

Question 31

Journey of blood through the kidney

Answer 31

``` Renal artery Interlobar artery Arcuate artery Interlobular artery Afferent arteriole Glomerulus Efferent arteriole Peritubular capillaries Interlobular vein Arcuate vein Interlobar vein Renal vein ```

Question 32

Ureter and bladder key points

Answer 32

``` Transitional epithelium Mucus membrane Very elastic subendothelial connective tissue Smooth muscle layers Outside layer of adventitia ```