Embryology

Question 1

What causes a Wilm’s tumor?

Answer 1

1.Cause: mutation of the WT1 gene which leads to abnormal differentiation of the intermediate mesoderm. Often presents with abnormalities of the reproductive system as well (due to the fact that the intermediate mesoderm gives rise to both the kidney and gonad).

Question 2

At what age does a wilm’s tumor appear?

Answer 2

before age 5 typically

Most common malignant tumor in children

Question 3

What arises from the nephrogenic ridge?

Answer 3

Urinary system

Question 4

What arises from the gonadal ridge?

Answer 4

Reproductive system

Question 5

The nephrogenic ridge and gonadal ridge are components of?

Answer 5

Intemediate mesoderm

Question 6

What is the first set of kidneys that forms?

Answer 6

Pronephros (vestigial structure, forms during week 4)

Question 7

What is the second set of kidneys? Are they functional?

Answer 7

Mesonephros - yes.

(form in month 3, drain to mesonephric duct (Wolffian)

Question 8

Where does mesonephric duct drain to?

Answer 8

Cloaca

Question 9

What is the “definative kidney”?

Answer 9

Metanephros

Question 10

What are the two structures of the metanephros?

Answer 10

Metanephric blastema

Ureteric bud (metanephric diverticulum)

Question 11

What forms the metanephric blastema? What excretory units does this form?

Answer 11

a. Forms from intermediate mesoderm within pelvis in a similar manner as mesonephros.
b. Forms excretory units of kidney (nephron)
1. Bowman’s capsule
2. Proximal convoluted tubules
3. Loops of henle
4. Distal convoluted tubules

Question 12

What is the ureteric bud formed from? What does it penetrate? What components of the duct system does it form?

Answer 12

a. Evagination of mesonephric duct
b. Penetrates metanephric blastema.
c. Forms duct system
1. Collecting tubules
2. Minor and major calyces
3. Renal pelvis
4. Ureter

Question 13

What causes renal agenesis?

Answer 13

a. Cause: Ureteric bud fails to form and/or induce differentiation of the metanephric blastema.
b. Can be unilateral or bilateral.

Question 14

What arises in the case of bilateral renal agenesis?

Answer 14

Potter sequence

Question 15

What does potter sequence result in? What secondary symptoms arise due to this?

Answer 15

Oligohydramnios (low levels of amniotic fluid)

Secondary symptoms caused by oligohydramnios…

1. Hypoplastic lungs
2. Potter facies: broad, flat nose; wide-set eyes; low-set ears; micrognathia.
3. Sometimes limb malformation as well (club foot)

Question 16

What is the cause of renal hypoplasia?

Answer 16

a.Cause: Inadequate branching of ureteric bud and lack of differentiation of nephrons.

Question 17

What’s going on in renal hypoplasia? What is persistent fetal lobulation?

Answer 17

a. Functional nephrons are present, just very few.
b. Persistent fetal lobulation is a type of renal hypoplasia

Question 18

What causes renal dysplasia?

Answer 18

Different causes, different types. Ex: multicystic dysplastic kidney - cystic diseases

Question 19

What do we need to know about polycystic disease?

Answer 19

They are congenital

Question 20

Describe the ascent of the kidneys

Answer 20

Week 6-9, normally kidney migrates out of pelvis into the abdomen. It rotates as it does so. As the kidney ascends it recieves new arteries. (initially from iliac arteries, post ascension, from aorta)

Question 21

What causes horseshoe kidney?

Answer 21

Inferior poles of left and right kidneys fuse in pelvis. Ascent is blocked by inferior menteric artery.

Question 22

What causes accessory renal arteries?

What are the symptoms?

Answer 22

a.Cause: Arise from persistence of caudal renal arteries during development.

Usually asymptomatic, in some cases can compress ureter and cause hydronephrosis

Question 23

Can you just remove accessory renal arteries?

Answer 23

No, since they are segmental arteries (providing blood to an entire kidney segment.

Question 24

What causes duplication of the urethra?

Answer 24

Splitting of the ureteric bud (should not happen)

Question 25

What is an ectopic ureter?

What part is normal?

Where doe the normal and abnormal ones open?

What does this cause?

Answer 25

Two independent ureters form with different origins and exits. The lower ureter is the normal one and drains to the bladder normally.

Abnormal opens Too low, beneath the sphincter urethrae.

Leads to urinary incontinence and predisposition to urinary tract infections (UTI)

Question 26

A.The urorectal septum divides the cloaca into…

Answer 26

the anterior urogenital sinus and the posterior rectum/anal canal.

Question 27

What are the portions of the urogenital sinus?

Answer 27

Cranial (vesical portion)

Middle (pelvic) portion

Caudal (phallic) portion

Question 28

Describe the cranial (vesical) portion of the urogenital sinus

Answer 28

a. Forms bladder; except for trigone region (from the mesonephric duct).
b. During development, the allantois (one of the fetal membrane) is connected to the endoderm of the urogenital sinus.
c. The allantois will form the urachus (median umbilical ligament).

Question 29

What does the middle (pelvic) portion of the urogenital sinus form?

Answer 29

Forms urethra in females.
Forms prostatic and membranous urethra in males.

Question 30

What does the caudal, (phallic) portion of the urogenital sinus form?

Answer 30

In males only - forms penile urethra

Question 31

What does the mesonephric duct form in men and women?

Answer 31

Women - nothing, it regresses

Men - most of the internal repro stuff

Question 32

What does the urachus typically form?

Answer 32

median umbilical ligament

Question 33

What causes exstrophy of the bladder/cloaca?

Answer 33

Failure of the ventral body wall to fuse

Question 34

What happens when the lumen of the urachus remains open?

Answer 34

1. Urachal fistula (entire lumen remains open, urine may leak from umbilicus).
2. Urachal sinus
3. Urachal cyst