Embryology of the UG system

Question 1

Urinary (and genital) system develops from

Answer 1

intermediate mesoderm of trilaminar disc

Question 2

Intermediate mesoderm separates from lateral and paraxial mesoderm during folding and forms

Answer 2

urogenital ridge

Question 3

Question 4

Pronephros (pronephric system) is nonfunctional cervical nephromtome. It is transitory and regresses by week

Answer 4

5

Question 5

Mesonephros is a primative kidney that develops in week

Answer 5

• 4
• contains
  
  • functional glomeruli
  • Mesonephric tubules
    
    • Mesonephric duct opens into cloaca

Question 6

The mesonephric duct opens into

Answer 6

cloaca

Question 7

Mesonephros are present and functional from weeks _____

Answer 7

• 6-10

Question 8

After week 10 the mesonephros degenerates except for

Answer 8

• The dcut sytem will contribue to part of the male genital system (ductus deferens)
• Some vestigial structures in the female

Question 9

Question 10

Renogenesis involves a process of reciprocal induction, which is ____ dependent

Answer 10

retinoic acid

Question 11

Cranial-caudal patterning establishes a “renogenic” region within the intermediate mesoderm in the tail of the embryo termed the

Answer 11

• Metanephric Blastema
  
  • The metanephric Blastema secretes growth factors that induce growth of the ureteric bud from the caudal portion of the mesonephric duct

Question 12

Steps in Renogenesis

Answer 12

• Involves a process of reciprocal induction, which is retinoic acid dependent
• Cranial-caudal patterning establishes a “renogenic” region within the intermediate mesoderm in the tail of the embryo
• This renogenic mesoderm is the metanephric blastema
• The metanephric blastema secretes growth factors that induce growth of the ureteric bud from the caudal portion of the mesonephric duct
• The ureteric bud proliferates and responds by secreting growth factors that stimulates proliferation and then differentiation of the metanephric blastema into glomeruli and kidney tubules
• Perturbations in any aspect of these inductive events (e.g. mutations of either metanephric or ureteric factors or disruption of retinoic acid signaling) may cause inhibition of ureteric bud growth and renal hypoplasia or agenesis
• Conversely, duplication or overproliferation of structures can also occur

Question 13

Ureteric bud derivatives

Answer 13

Collectin tubules/ducts —> Minor Calyces —-> Major Calyces —-> Renal Pelvis —> Ureters

Question 14

In utero function of metanephros

Answer 14

• Blood plasma from glomerular capillaries begins to be filtered by 10th week
• Urine is produced, but the primary funciton is not to clear waste (placenta) but to supplement produciton of amniotic fluid
• Oligohydramnios (insufficient amount of amniotic fluid) may indicate bilateral renal agenesis or urethral obstruction

Question 15

Accessory Renal Vessels

Answer 15

• Kidneys are formed in pelvis but ascend to lumbar region with progressive revascularization from common iliac and aorta
• Aberrant renal vessels enter the kidney independently from the primary renal vessels
• These occur in approximately 10% of individuals and 98% arise from the the abdominal aorta. Most enter the renal pelvis and pose little problem
• Aberrant arteries to the inferior pole of the kidney (4-6%) may be the cause of obstruction of the ureter and may cause an intermittent or continuous obstruction to urinary drainage form the renal pelvis

Question 16

Renal Agenesis

Answer 16

Question 17

Renal Fusion

Answer 17

• Prevents normal rotation
• Abnormal blood supply
  
  • usually from middle sacral or common iliac arteries
• ectopic kidney
  
  • may also be crossed with/without fusion
• Horshoe kidney

Question 18

___% of Horseshoe kidney presentation are fused at lower pole and usually found

Answer 18

• 90% of horshoe kidney’s are fused at lower pole
• Usually foudn inferior to inferior mesenteric artery

Question 20

Wilm’s Tumor

Answer 20

• Cancer of the kidney
• This usually affects children under the age of 5
• Wilms’ tumor is caused by motations in the WT1 gene

Question 21

Development of the urinary bladder

Answer 21

• The cloaca is divided by the urorectal septum
• The DORSAL (inferior) portion develops into the rectum and anal canal
• The ventral (superior) portion develops into the BLADDER and UROGENITAL SINS, which will give rise to the bladder and lower urogenital tracts (prostatic and penile urethrae) in males; urethra and lower vagina in females)

Question 22

Between weeks ___ -___, mesonephric duct and ureteric bud incorporation into posterior wall of urinary bladder

Answer 22

4-6

Question 23

Ureteric buds open into bladder wall, while mesonephric ducts open more inferiorly into the ____

Answer 23

• pelvic urethra
  
  • The triangular region of the incorporated mesonephric duct incorporated in the bladder wall forms the trigone

Question 24

An ectopic ureter

Answer 24

• the distal ureter acts as the ductus deferens and forms a trigone (this can lead to always being wet bc they have no sphincter to block the flow of urine)

Question 25

Urachal Fistula or cyst

Answer 25

• Bladder is continuous superiorly with allantois (which should collapse and become the urachus)
• The urachus may remain patent through its length (C-urachal fistula) or only at an end (B-urachal sinus)
• Remnants of the urachal lumen may also give rise to urachal cysts (A). These usually present as an abdominal mass

Question 26

At what week does phenotypic sexual differentiation begin

Answer 26

Week 7

Question 27

Male and Female external genitalia can be recognized at week

Answer 27

12

Question 28

Phenotypic differentiation is complete at week

Answer 28

20

Question 29

Mullerian (paramesonephric) duct develops into:

Answer 29

• Fallopian tubules
• uterus
• upper part of vagina

Question 30

Wolffian (mesonephric) duct develops into:

Answer 30

• Epididymis
• vas deferens
• seminal vesicle
• ejaculatory duct

Question 31

Synthesis of SRY protein (testis-determining factor, TDF) triggers ____ development

Answer 31

male

Question 32

Question 33

Question 34

Question 35

are paramesonephric and mesonephric ducts present during indifferent stage

Answer 35

• yes
  
  • testosterone leads to further development of Mesonephric duct
  • absence of testerone leads to further development of paramesonephric duct

Question 36

Gonads develop from what tissue(s)

Answer 36

• 3
  
  • epithelium of intraembryonic coelom
  • intermediate mesoderm
  • primordial germ cells
    
    • primordial germ cells from mesoderm of yolk sac invade the dorsal mesentery and migrate to urogenital ridges

Question 37

External Genitalia development

Answer 37

• Phallus
  
  • clitoris or penis
• (Uro)genital folds
  
  • labis minora or shaft of the penis
• Labioscrotal (Genital) swellings
  
  • labis majora or scrotum

Question 38

46, XY can have persistence of paramesonephric ducts if

Answer 38

the circulating levels of AMH are low or there is an abnormal response to normal AMH

Question 39

Mullerian agenesis

Answer 39

• Failure of the paramesonephric ducts to develop
• Results in missing uterine tubes, uterus and variable malformations of the upper poriton of the vagina
• Also called MRKH or Mayer-Rokitansky-Kuster-Hauser Syndrome

Question 40

Hypospadias

Answer 40

• Incomplete fusion of the urethral folds
• Urethra opens onto the ventral aspect of the penis
• Can result form inadequate androgen production or inadequate receptor sites for DHT
• Four types
  
  • Gladular
  • Penile
  • Penoscrotal
  • Perineal

Question 41

Classic virilizing adrenal hyperplasia

Answer 41

• Female intersex
• Females (46, XX) with severe forms of adrenal hyperplasia have ambigous genitalia at birth due to excess adrenal androgen production in utero
• Ambiguous genitalia ranges from complete fusion of the labioscrotal folds and a phallic urethra to only clitoromegaly, partial fusion of the labioscrotal folds, or both
• No abnormalities of ovaries

Question 42

Androgen Insensitivity Syndrome (AIS)

Answer 42

• An X-linked disorder in which receptors remain unresponsive to androgens
• Despite normal levels of testosterone, the male fetus fails to masculinise
• The external genitalia are feminine. Internally they possess non-functioning undescended testes
• At puberty, secondary female sexual characteristics may appear due to estradiol from testosterone aromatization
• Such males not only physically resemble females, but also tend to be feminine in gender and maybe behavior
• it is common to perform gonadectomies at puberty and for them to receive hormone therapy, to be reared as females

Question 43

5-alpha reductase deficiency (5-ARD)

Answer 43

• Autosomal recessive condition resulting in the inability to convert testosterone to the more physiologically active dihydrotestosterone (DHT)
• Because DHT is required for the normal masculinization of the external genitalia in utero, genetic males with 5-ARD are born with ambiguous genitalia (underdevelopment of penis and scrotum or pseudovaginal perineoscrotal hypospadias)
• Derivatives of mesophric duct are normal
• often misdiagnosed as AIS
• ‘Guevedoche’ or ‘Machihembras’ (first women, then man); third gender in some cultures
  
  • this is because at puberty when testosterone levels get high enough they may masculinize)