Embryology

Question 1

From where does the urinary tract originate?

Answer 1

The cloaca

Question 2

What adult structures are formed from the ureteric bud (mesonephric duct)?

Answer 2

Collecting tubules and ducts
Minor and major calyces
Ureters
Renal pelvis

Question 3

What adult structures are formed from the metanephric blastema/mesoderm/metanephros?

Answer 3

The nephrons

Question 4

Over what period does organogenesis take place?

Answer 4

Normally weeks 3-8

Question 5

What makes up the urineferous tubule?

Answer 5

The nephron plus the collecting duct

Question 6

What makes up the nephron?

Answer 6

Renal corpuscle
PCT
Loop of Henle
DCT

Question 7

During what week of development does gastrulation take place?

Answer 7

3rd week

Question 8

What happens in gastrulation?

Answer 8

The bilaminar disk becomes trilaminar and three three primary germ layers form, from which all body tissues develop - ectoderm, endoderm, mesoderm

Question 9

What forms the kidney and ureter?

Answer 9

The intermediate mesoderm

Question 10

What forms the bladder and urethra?

Answer 10

The cloaca

Question 11

What does the paramesonephric duct form?

Answer 11

Uterus and uterine tubules

Question 12

What does the mesonephric duct form?

Answer 12

Ductus deferens

Question 13

What are the three sets of kidneys which develop before the genital system?

Answer 13

1st set: Pronephros

2nd set: Mesonephros

3rd: Metanephros

Question 14

What is the pronephros?

Answer 14

The first set of ‘kidneys’ which appear as the nephrogenic cord is subdivided. They are rudimentary and non-functioning and appear early in week 4

Question 15

What are the mesonephros?

Answer 15

Well developed set of early kidneys which function briefly during the early foetal period, appear late in week 4. They function as interim kidneys for four weeks

Question 16

What are the metanephros?

Answer 16

The primordia of permanent kidneys that develop in the 5th week

Question 17

What are the two sources of the metanephros from which the permanent kidneys develop?

Answer 17

Ureteric bud - drains the metanephros and will become the adult ureter
Metanephrogenic blastema

Question 18

Describe the development onwards of the ureteric bud

Answer 18

The stalk of the bud becomes the ureter and the cranial part becomes the collecting tubules. The first 4 generations of tubules become the major calyces and the second 4 generations of tubules become the minor calyces

Question 19

Describe the ascent of the kidneys

Answer 19

The ascent is mainly due to the differential growth of the lower body inferiorly away from the kidneys so they appear to ascend
The hilum rotates 90 degrees from ventral to medial
The ascent stops when contact with adrenal glands is made

Question 20

What divides the cloaca and what is it divided into?

Answer 20

The urorectal septum

Into the urogenital sinus and the rectal canal

Question 21

What do the three parts of the urogenital sinus go on to form?

Answer 21

Cranial part - bladder

Pelvic part - prostatic and membranous urethra in males, entire urethra in females

Caudal part - penile urethra in males

Question 22

What forms the trigone of the bladder?

Answer 22

The incorporation of the inferior parts of the mesophrenic ducts

Question 23

What adult structures are formed from the cloaca (urogenital sinus)?

Answer 23

Urethra

Bladder

Question 24

What are some abnormalities related to induction or differentiation of kidney tissue?

Answer 24

Duplication of the urinary tract - premature division of the ureteric bud resulting in either a double kidney or duplicated ureter and renal pelvis

Nephroblastoma (Wilm’s tumour) - malignant

Polycystic kidney disease

Question 25

What are some abnormalities relating to the ascent of the kidneys?

Answer 25

Pelvic kidney - one or both kidney(s) stay in the pelvis rather than ascending

Horseshoe kidney - the two developing kidneys fuse ventrally into a single kidney that gets trapped in the abdomen by the inferior mesenteric A

Supernumerary arteries - often more than one renal artery per kidney, can compress ureter and cause back up of fluid into kidney - hydronephrosis

Question 26

What are some abnormalities relating to the formation of the bladder?

Answer 26

Trigonitis -sensitive to sex hormones and can undergo metaplasia leading to obstruction

Abnormal attachment of the ureters - the ureters can sometimes be attached to either the urethra or parts of the reproductive tracts

Urachal fistulas, sinuses and cysts - occur when some of the allantois persists