16.4 Histology: Of the urinary system

Question 1

What zones is the kidney divided into?

Answer 1

Cortex (outer), medulla (inner)

Question 2

Where do blood vessels of the kidney enter and exit?

What is at the boundary between cortex and medulla?

Answer 2

Enter and exit at the hilum

Arcuate vessels at the boundary

Question 3

What is the nephron? What does it consist of?

Answer 3

Functional unit of kidney (0.3-1.5 million/kidney)

Renal corpuscle, tubule (nephron joins collecting duct in the cortex)

Question 4

What are the roles of the corpuscle, the tubule and the collecting duct?

Answer 4

Corpuscle: filters blood
Tubule: modifies filtrate
Collecting duct: carries urine away

Question 5

What are the differences in components of the cortex and medulla?

Answer 5

Cortex contains all of the corpuscles

Question 6

What are the two types of nephron?

Answer 6

Juxta medullary (15%), base of cortex, loops deep into medulla

Cortical (85%), higher in cortex, tubule loops halfway into medulla

Question 7

What is the glomerulus? Where does it sit?

Answer 7

Glomerulus is a tuft of capillaries connected to arteriole, pushes into expanded tubular end

Question 8

What is Bowman’s space? What is it lined by?

Answer 8

A space continuous with the lumen of the tubules that doesn’t have capillaries. (the urinary space)

Lined by podocytes over capillaries, parietal cells over outer layer.

Question 9

What cells support the glomerulus?

Answer 9

Mesangial cells (limited connective tissue)

Question 10

What are the two poles of the renal corpuscle?

Answer 10

Vascular pole (capillaries enter)

Urinary pole (tubule drains Bowman’s space)

Question 11

What is the renal corpuscle lined with?

Answer 11

Squamous parietal cells give way to cuboidal epithelium of tubule

Question 12

What covers glomerular capillaries? What is inbetween the processes?

Answer 12

Podocytes, glycocalyx and slit membranes between the processes

Question 13

What is the filtration barrier in the renal corpuscle? (3)

Answer 13

A barrier that contains slit membranes with small pores (3-5nm), a basal lamina that traps molecules (>69kD), and the fenestrated capillary that lacks diphragms

Question 14

What is the role of the kidney tubule? What does this result in?

Answer 14

Modify ultrafiltrate, recover and secrete substances=hyperosmotic urine (rich in urea)

Question 15

What does the proximal tubule do? What part is in the cortex?

Answer 15

Proximal tubule reabsorbs glucose, aa’s, protein

Part in cortex is convoluted tubule

Question 16

What happens on the folded basal membrane of proximal tubule?

Answer 16

Na+/K+ ATPase pumping Na+ across cell, Cl/H2O follow, Na/Cl/H2O moves passively across apical membrane (needs ATP from mitochondria)

Question 17

What is the Loop of Henle permeable to?

Answer 17

Urea and electrolytes, (descending limb more permeable to water)

Question 18

What does the distal tubule lack?

What is it permeable/impermeable to?

How is it different to the proximal tubule?

Which part is in the cortex?

Answer 18

Lacks microvilli (cuboidal cells)

Impermeable to water/urea (has Cl/Na pumps)

More mitochondria than proximal tubule

Distal convoluted tubule in cortex

Question 19

What makes the collecting duct permeable to water?

Answer 19

Antidieuretic hormone (vasporessin)

Question 20

What are the juxtamedullary nephrons critical for?

Answer 20

Hyperosmotic urine

Question 21

What do juxtaglomerular apparatus do? What do the JG cells do?

Answer 21

Monitor filtrate volume/Na+ concentation

Release renin (eventually AngII)

Question 22

What are vasa recta? What do they do?

Answer 22

Capillaries from efferent arteriole that envelop tubule (crucial for urine concentration)

Question 23

What does the medulla consist of?

Answer 23

Thick/thin loops of Henle
Collecting ducts
Capillaries of vasa recta

Question 24

What is the structure of the ureter? (3)

Answer 24

Lined with transitional epithelium, has LP, thick muscularis of SM

Question 25

What is the bladder lined with?

Answer 25

Transitional epithelium

Question 26

What is the ureter lined with?

Answer 26

Transitional and stratified squamous epithelium

Question 27

What does the pelivc floor act as?

Answer 27

Sphincter outside bladder (both sexes)