Development of URO system

Question 1

Describe the formation of the yolk sac

Answer 1

Forms as embryo rolls up
- links to midgut
- becomes the choriovitelline placenta

Question 2

Describe the formation of teh allantoic sac

Answer 2

Forms as an outgrowth of the hindgut
- root with gut becomes divided by urorectal septum
- A-sac becomes chorioallantoic placenta

Question 3

What are the 3 divisions of the mesoderm?

Answer 3

Paraxial
Intermediate
Lateral plate (splanchnic and somatic)

Question 4

How do the kidneys form?

Answer 4

Wave of differentiation down mesoderm:
- forms pronephros (this eventually regress)
- mesonephros then forms - regresses to form part of gonads and adrenal cortex
- metanephros then forms - becomes definitive kidney
- metanephric/ureteric duct becomes uretes, pelvis and collecting ducts

Question 5

What is the role of the mesonephros in fish/amphibians?

Answer 5

reproductive
endocrine
excretory

Question 6

What embryological remnant do the mesonephric ducts become?

Answer 6

ductus deferentes

Question 7

How is urine recycled in the foetus?

Answer 7

The urachus drains from the bladder into the allantois

Question 8

What is special about the development of the stallion urogenital system?

Answer 8

PMN persist in stallion as the uterus masculinus on the surface of the bladder trigone

Question 9

What are the embryological origins of the bladder and the bladder trigone?

Answer 9

Bladder - endodermal origin
Bladder trigone - mesodermal origin

Question 10

Describe the embryological origins of the adrenal cortex and medulla

Answer 10

Adrenal cortex is derived from some of regressing mesonephric tubules
Adrenal medulla derived from neural crest cells which migrate into centre of adrenal cortex

Question 11

Name some common developmental defects of the urogenital system

Answer 11

Ectopic ureters - one of both ureters enter the urethra/vagina downstream of the bladder sphincter
Renal agenesis, dysplasia, hypoplasia
Polycystic kidneys

Question 12

How does freemartinism occur?

Answer 12

A heifer born as a twin to a bull
Common blood supply between male and female fetus allows XY germ cells to migrate to female ovaries
Female exposed to testosterone
STERILE

Question 13

What does a freemartin calf look like?

Answer 13

Enlarged clitoris
Under-developed vulva
Long hairs near vulva
Small or absent uterus
Small ovaries
Prominant median eminence of pelvis, can be palpated on floor of pelvic canal

Question 14

Why is Angiotensin converting enzyme inhibitor (drug) effective at managing hypertension

Answer 14

blocks conversion of angiotensin I to angiotensin II (vasoconstrictor) to help dilate blood vessels & decreases aldosterone (promotes sodium & water retention & thus increases volume & pressure) secretion

Question 15

Why is Angiotensin receptor blocker (drug) effective at managing hypertension

Answer 15

block action of angiotensin II

Question 16

Why is calcium channel blocker (drug) effective at managing hypertension

Answer 16

inhibits influx of calcium into vascular smooth muscle cells leading to dilation

Question 17

Why is A1 blocker (drug) effective at managing hypertension

Answer 17

block a1 adrenergic receptors on vascular smooth muscle cells to inhibit vasoconstrictive effects of catecholamines leading to vasodilation

Question 18

Why is aldosterone antagonist (drug) effective at managing hypertension

Answer 18

inhibit action of aldosterone by binding to mineralocorticoid receptors in kidneys to prevent water retention, potassium excretion & vasoconstriction

Question 19

Why is B blocker (drug) effective at managing hypertension

Answer 19

block action of catecholamines & inhibit release of renin

Question 20

Why is thiazide diuretic (drug) effective at managing hypertension

Answer 20

inhibit reabsorption of sodium & chloride ions in distal convoluted tubules of kidneys to reduce blood volume & thus pressure

Question 21

Why is loop diuretic (drug) effective at managing hypertension

Answer 21

inhibit sodium-potassium-chloride co-transporter in thick ascending loop of henle leading to increased secretion