Lecture 3 Development Of The Repro System

Question 1

What does the urogenital system develop from?

Answer 1

Intermediate mesoderm

Question 2

Development of the reproductive system

Answer 2

1. Indifferent gonads develop from primordial germ cells
2. The indifferent gonads can differentiate into the testis or ovary and the indifferent external genitalia depending on the presence of testosterone.
3. The testis or ovary have indifferent duct systems and differentiate into either the epididymis and vas deferens for the testis or uterus, Fallopian tubes and part of the vagina for the ovary

Question 3

Which structure is shared between the GI tract, Repro tract and urinary tract?

Answer 3

The cloaca - dilated end of the hindgut closed to the outside by the cloacal membrane

Question 4

Urogenital ridge

Answer 4

Region of intermediate mesoderm giving rise to the embryonic kidney and gonad

Question 5

Where is the gonad derived from?

Answer 5

From intermediate mesoderm and the primordial germ cells

Question 6

Primordial germ cells

Answer 6

Arise in the yolk sac and migrate when developed into the retroperitoneum, along the dorsal mesentery

Question 7

What drives male development?

Answer 7

SRY gene present in the Y chromosome

Question 8

Male development

Answer 8

Gonad: testis
Hormone: Testosterone (androgens) and Mullerian inhibiting hormone
Internal genitalia: mesonephric duct (wolffian)

Question 9

Female development

Answer 9

Gonad: ovary
Hormone: oestrogen
Internal genitalia: paramesonephric duct (Müllerian duct)

Question 10

Why does the wolffian mesonephric duct develop in men?

Answer 10

Due to androgens released in the testis

Question 11

Why is there no mullerian (paramesonephric) duct in men

Answer 11

Due to mullerian inhibiting hormone released by the testis that suppresses the paramesonephric duct (mullerian)

Question 12

Where do the paramesonephric and mesonephric ducts end?

Answer 12

At the urogenital sinus part of the cloaca

Question 13

Ectopic androgen effects in women

Answer 13

Wolffian and Müllerian ducts

Persistence of wolffian mesonephric duct even in women due to androgen
No testis therefore no MIH therefore persistence of the mullerian paramesonephric duct

Question 14

Androgen insensitivity syndrome in men

Answer 14

No wolffian mesonephric duct
No mullerian paramesonephric duct

Receptors are insensitive to testosterone therefore Wolffian ducts degenerate
Testes present that secrete MIH therefore mullerian paramesonephric ducts degenerate

Question 15

Mesonephric wolffian duct

Answer 15

First acts as the duct for the embryonic kidney in both males and females
Drains into the urogenital sinus
When the kidney develops it becomes surplus

It is converted into the vas deferens and epididymis
Migrates with the testis as it descends to the scrotum

Question 16

Urogenital sinus

Answer 16

Becomes the urinary bladder

Question 17

Paramesonephric Müllerian duct

Answer 17

Invagination of the urogenital ridge epithelium

Cranially: opens into the abdominal cavity
Caudally: makes contact with the cloaca urogenital sinus

Question 18

Undifferentiated external genitalia components

Answer 18

Genital tubercle
Genital folds
Genital swellings

Question 19

External genitalia of men development

Answer 19

The genital tubercle elongates into the glans penis
The genital folds fuse to form the spongy urethra (penile raphe)
The genital swellings become the scrotum

Influenced by testes derived androgen hormones

Question 20

External genitalia of women development

Answer 20

The genital folds develop into the labia minora
The genital tubercle develops into the clitoris
The genital swellings develop into the labia majora
The urethra opens into the vestibule

Question 21

Descent of the gonad

Answer 21

Gubernaculum attaches the gonad inferiorly to the labioscrotal folds
Abdominal pelvic cavity increases
Gonads descend

Question 22

Descent of testes

Answer 22

1. The gubernaculum attaches to the inferior pole of the testes
2. It contacts and shortens dragging the testes down to the scrotum causing the testes to invaginate into the layers of the abdominal wall
3. Forms the inguinal canal
4. The testes pass through the processus vaginalis
5. Once the testes are in the scrotum, the gubernaculum becomes the scrotal ligament and the processus vaginalis becomes the tunica vaginalis

Question 23

Covering of the spermatic cord

Answer 23

Internal spermatic fascia - transversalis fascia
Cremasteric fascia - internal oblique aopneurosis
External spermatic fascia - external oblique aponeurosis

Question 24

Descent of the ovary

Answer 24

1. Gubernaculum attaches the ovary inferiorly to the labioscrotal folds
2. The ovary descends to the pelvis
3. The developed uterus prevents further descent
4. The remnants of the gubernaculum are the round ligament and ligament of the ovary

Question 25

Where is the round ligament of the uterus found

Answer 25

Inguinal canal

Question 26

What part of the gonad does the testes develop from?

Answer 26

Medulla

Question 27

What part of the gonad does the ovaries develop from

Answer 27

Cortex

Question 28

Congenital adrenal hyperplasia

Answer 28

Decreased concentration of corticoids (cortisol and mineralocorticoids like aldosterone) 
Increased concentration of androgens 
- ambiguous external genitalia 
- weight loss
- lethargic