Embryology

Question 1

What germ layer do the kidneys originate from?

Answer 1

Mesoderm

Question 2

When do the pronephros form?

Answer 2

In the 4th week of gestation

Question 3

Where do the pronephros form?

Answer 3

Cervical region

Question 4

What part of the pronephros persists?

Answer 4

Duct

Question 5

How many mesonephros are produced and in what direction?

Answer 5

40 tubules produced craniocaudally

Question 6

When do the mesonephros regress?

Answer 6

By the end of the 5th week of gestation

Question 7

When the mesonephros regress, what is left and what do they do?

Answer 7

Leave 20 pairs (L1-L3):

 - Differentiate in excretory units
           - > Function weeks 6-10 then regress

Question 8

When do the metanephros appear?

Answer 8

~5 weeks gestation

Question 9

When do the metanephros begin to function?

Answer 9

~9-11 weeks gestation

Question 10

What do the metanephros form?

Answer 10

The permanent kidney

Question 11

What two structures form the metanephros and where do they originate from?

Answer 11

Ureteric bud:
- Protrusion from mesonephric duct
Metanephric blastama:
-From the mesonephric duct

Question 12

In regards to the metanephros, when do the ureteric buds sprout and where from?

Answer 12

Day 28 of gestation

From distal mesonephric ducts

Question 13

In regards to the metanephros, when does the metanephric blastema sprout and where from?

Answer 13

Day 32 of gestation

Ureteric buds penetrate sacral intermediate mesoderm

Question 14

What is the process of development from the ureteric bud?

Answer 14

Ureteric bud -> Ureter -> Renal pelvis -> Major calyces -> Minor calyces -> Collecting ducts

Question 15

What part of development of the ureteric bud is a dichotomous division?

Answer 15

Renal pelvis -> Major calyces

Question 16

What does the metanephric blastema form?

Answer 16

Metanephric blastema -> Metanephric cap -> Metanephric vesicle -> Bowman’s capsule:

 - > PCT
 - > Loop of Henle
 - > DCT

Question 17

Where do the kidneys initially develop? When do they reach their end position?

Answer 17

In pelvis

Reach end position by week 9

Question 18

In what direction do the hila of the kidneys point during weeks 5 and 6?

Answer 18

Anteriorly (in pelvis)

Question 19

When do the kidneys reach the abdomen and what direction do the hila face then?

Answer 19

~Week 7

Hila face medially

Question 20

What happens to the kidneys as the embryo grows caudally?

Answer 20

Kidneys start to lie:

 - Retoperitoneally
 - At L1 level

Question 21

How can the general blood supply of the kidney be described?

Answer 21

By closest aortic branches

Question 22

What vessels initially supply the kidney?

Answer 22

Median sacral nerve and temporary aortic branches

Question 23

What happens to the temporary aortic branches when kidney reaches final position?

Answer 23

Tend to regress (can persist -> Accessory renal arteries)

Question 24

What is a pelvic kidney?

Answer 24

When one kidney fails to ascend

Question 25

What is the process by which a horseshoe kidney forms?

Answer 25

Inferior poles of metanephroi meet and fuse before ascent:

- Trapped beneath inferior mesenteric artery

Question 26

What is the cloaca?

Answer 26

Hindgut endoderm

Question 27

What forms the cloaca?

Answer 27

Rectum
Primitive urogenital sinus:
     - Bladder
     - Pelvic urethra
     - Definitive urogenital sinus

Question 28

Where do the mesonephric ducts incorporate into and what do they form?

Answer 28

Into posterior bladder wall
Form:
     - Epididymis
     - Vas deferens
     - Seminal vesicle

Question 29

What is the urachus?

Answer 29

The closed remnant of the allantois, a duct between the bladder and the yolk sac

Question 30

What is a urachal sinus?

Answer 30

Urachal lumen persists at upper part:

- Opens at umbilicus

Question 31

What is a urachal fistula?

Answer 31

Urachal lumen persists along entire length:

 - One end open in the bladder
 - One end open at umbilicus
           - > Urine discharged through umbilicus

Question 32

What is a urachal cyst?

Answer 32

Small part of lumen remains patent:
- Each end closed
-> Forming median umbilical ligament
Secretory activity of epithelium remains active:
- Cystic dilatation

Question 33

What is the normal remnant of the urachus?

Answer 33

Median umbilical ligament