Development of the Genitals

Question 1

What is the genital ridge? Where does it develop from? What does it consist of?

Answer 1

Precursor of the gonads (reproductive organ)
Intermediate mesoderm
Ridge of mesenchyme + epithelium

Question 2

What cells migrate to the genital ridge? During which week? What do they allow to form?

Answer 2

Primordial Germ cells
6th week
Primitive sex cords

Question 3

What do the primitive sex cords form in males? What are they composed of? (3)

Answer 3

Testis cords
1.Sertoli cells
2. Germ cells
3. Leydig cells

Question 4

Where are Leydig cells originated from? Where are they found? What do they produce from which week?

Answer 4

Mesenchymal origin
Between cords
Produce testosterone- from week 8

Question 5

What happens to the Primitive sex cords in females? What develops? What do they divide into? What does this form?

Answer 5

Regress
Cortical cords
Cells that surround germ cells
Forms the primordial follicle

Question 6

When is the indifferent gonad identical until? What are the two ducts called? When do they begin to differentiate?

Answer 6

7th week
Mesonephric (Wolffian) and Paramesonephric (Mullerian)
Begin to differentiate at week 7

Question 7

What gene determines Development of the testes? What does it stand for and what chromosome is it present on?

Answer 7

SRY
Sex determining region -Y (chromosome)

Question 8

What other two hormones allow male development of testes? How?

Answer 8

Anti-Mullerian hormone- causes Mullerian duct to regress
Testosterone- stabilises wolffian ducts

Question 9

What three factors allow female development?

Answer 9

Absence of SRY
WNT4- ovarian development
Oestrogen- Female differentiation, develops mullerian ducts

Question 10

Where do the caudal and rostral ends of the mullerian ducts open up into respectively? Where does it project into?

Answer 10

Caudal- Meet in midline
Rostral- opens into abdominal cavity
Project into urogenital sinus

Question 11

Where does the Mesonephric/Wolffian duct open into?

Answer 11

Urogenital sinus

Question 12

What do the mesonephric/ Wolffian ducts develop into? Under the influence of what? Where does the distal end open into? What does this mean?

Answer 12

Vas deferens under influence of testosterone
Distal end opens up into urogenital sinus and absorbed by bladder wall
Means ureter and duct enter separately

Question 13

The mesonephric duct opens into the part of the urogenital sinus that will become what? What does this form? What develops around it?

Answer 13

Prostatic urethra
Forms ejaculatory duct
Prostate develops around ejaculatory duct

Question 14

What else develops from the Vas deferens? What cells produce anti-mullerian hormone? What does this cause?

Answer 14

Seminal vesicle
Sertoli cells
Regression of the paramesonephric/ mullerian ducts

Question 15

What do the upper parts of the paramesonephric ducts develop into? What happens to the caudal parts? What does this form (3)? Under the influence of?

Answer 15

Uterine tubes
Fuse with each other
Uterus, cervix and upper vagina
Oestrogen

Question 16

What makes up the upper and lower parts of the developing vagina respectively? What happens when they meet? What develops?

Answer 16

Upper= Paramesonephric ducts
lower= Urogenital sinus
Growth of sinovaginal bulbs
Lumen develops

Question 17

What are the 4 key structures of the indifferent external genitalia?

Answer 17

1. Genital tubercle
2. Urethral folds
3. Urethral groove
4. Genital swellings

Question 18

What do the 4 key structures of the undifferentiated external genitalia develop into in females? Under the influence of what?

Answer 18

1.Genital tubercle- Clitoris
2.Urethral folds= Labia minora
3.Urethral groove= Vestibule
4.Genital swellings= Labia major
Oestrogen

Question 19

What three key structures of the undifferentiated external genitalia do parts of the male external genitalia develop into? How? Under what influence?

Answer 19

Genital tubercle- Elongates to form penis
Urethral folds- fuse to form penile urethra
Genital swellings- scrotum