renal histology

Question 1

what are the functions of the kidney

Answer 1

• filter blood to remove waste as urine
• regulate water, salt, acid-base balance
• regulate BP
• produce hormones/enzymes (e.g. renin)

Question 2

describe a nephron

Answer 2

• is the smallest functional unit of the kidneys
• it is a filtering tubule
• there are around 1 million per kidney
• blood filter attached to a tubular epithelium

Question 3

what cells line the renal corpuscle

Answer 3

podocytes (envolope capillaries)

parietal epithelial cells (squamous)

Question 4

what are the 3 main components of the glomerular filtration barrier

Answer 4

• endothelium (wall of capillary)
• glomerular basement membrane
• podocytes

Question 5

function of the glomerular filtration barrier

Answer 5

• physical barrier
• charged selective barrier (repels negative charges)
  e. g. albumin
• restricts large proteins

Question 6

describe the glomerular capillary endothelium

Answer 6

• negatively charged glycocalyx (repels negatively charged proteins)
• holes which are permeable to small molecules

Question 7

describe the glomerular basement membrane

Answer 7

• thick
• made up of collagen and negatively charged proteoglycans
• has a dense core and less dense outer layer
• acts as a physical (inner) and charged barrier (outer)

Question 8

describe the podocytes

Answer 8

• adhere to GBM
• forms slits through primary and secondary processes
• covered in a negatively charged glycocalyx coat

Question 9

define podocyte effacement

Answer 9

a disease damaging the glomerular filter - causing a leaky filter

Question 10

describe the role of mesangial cells

Answer 10

• SM cells packed inside capillary tuft
• maintain tuft shape
• produce ECM
• loss of function results in glomerular scarring from overproducing ECM

Question 11

describe the contents of the juxtaglomerular apparatus

Answer 11

JG cells - modified SM cells that line the afferent arteriole and can secrete renin
macula densa cells - special cells lining thick ascending limb, sense salt conc in filtrate (flow rate)
extraglomerular mesangial cells

Question 12

describe the function of the juxtaglomerular apparatus

Answer 12

• if the concentration of salt in the distal tubule is high it will induce afferent arteriolar vasoconstriction
• if the flow/salt concentration is low then it will induce renin release

Question 13

features of proximal tubule cells

Answer 13

• cuboidal epithelium
• brush border (microvilli) to increase surface area
• pinocytosis
• lateral processes and infoldings to increase surface area

Question 14

features of thin limb cells

Answer 14

• thin squamous epithelium
• role in water reabsorption as part of LOH
• nuclei bulge into lumen

Question 15

features of distal tubule cells

Answer 15

• no brush border
• no pinocytosis
• cuboidal
• lateral processes and infoldings

Question 16

features of collecting duct cells

Answer 16

-cuboidal to columnar epithelium