Thurber RS 3- Development of the Urogenital Sinus

Question 1

What structures form the definitive kidney?

Answer 1

The definitive kidneys (metanephros) arise from two sources

1) Metanephric blastema gives rise to the excretory system of the kidney
2) Ureteric bud gives rise to the collecting system of the kidney

Question 2

What are some congenital kidney anomalies?

Answer 2

Horseshoe bladder: Kidneys fused at their anterior pole and the inferior mesenteric artery prevents them from ascending

Kidney agenesis: Can cause oligohydramnios

Pelvic Kidneys: Umbilical arteries prevent ascension

Duplication of ureters

Ectopic Connections: The ureters form fistulas with the rectum, vagina, urethra

Question 3

What is the difference between epispadias and hypospadias

Answer 3

Epispadias is an opening the top (dorsal) side of the urethra, while hypospadias is an opening on the bottom (ventral)

Question 4

What structures does the vagina come from?

Answer 4

The top 1/3: Paramesonephric ducts

Bottom 2/3rds: Urogenital sinus, or sinovaginal bulb

Question 5

What is the urachus/allantois? What happens if it does not obliterate?

Answer 5

The allantois connects the apex of the bladder and umbilicus to drain the bladder of the fetus. It obliterates and becomes the median umbilical ligament.

If it does not obliterate a urachal fistula, where the bladder contents can pass through the umbilicus

Question 6

What part of the embryological germ layers do the gonads, kidneys and genital ducts come from?

Answer 6

Intermediate Mesoderm

Question 7

What is the urogenital ridge? What structures does it differentiate into?

Answer 7

The intermediate mesoderm differentiates into two columns called the urogenital ridges.

The urogenital ridges further differentiate into the nephrogenic cord (which becomes the urinary system) and the gonadal ridge (which becomes the genital system)

Question 8

What are the three successive structures that lead up to the permanent kidney?

Answer 8

Pronephros (non-functional)

Mesonephros (Regresses, but gives rise to the mesonephric ducts)

Metanephros- Arises from the ureteric bud and metanephric blastema, becomes the permanent kidney

Question 9

What structures of the urogenital system does the endoderm give rise to?

Answer 9

• Epithelium of the bladder and urethra
• Inferior 2/3rds of the vagina (sinovaginal bulb)
• Prostate gland
• Bulbourethral, paraurethral and greater vestibular glands

Question 10

What are the parts of the urogenital sinus? What structures arise/events occur at each part?

Answer 10

The urogenital sinus can be divided into vesical, pelvic and phallic parts

Vesical part: Gives rise to the bladder

Pelvic part differs in males and females

• Males: Membranous and prostatic urethra, prostate and bulbourethral gland, location where mesonephric ducts
• Females: urethra, sinovaginal bulb, paramesonephric ducts connect

Phallic part

• In females: Vestibule of the vagina
• In males: Penile urethra

Question 11

What are the 5 uterine and vaginal abnormalities listed?

Answer 11

Uterine didelphys w/double vagina: No fusion of the paramesonephric ducts

Uterine bicornis with single vagina: Partial fusion of the paramesonephric ducts

Uterus bicornis unicollis: One paramesonephric duct does not connect with the sinovaginal bulb/urogenital sinus

Vaginal atresia: Sinovaginal bulb does not form

Separated uterus: Uterine septum is maintained