Embryology

Question 1

What triggers the formation of testis from the indifferent gonad?

Answer 1

The SRY gene on the Y chromosome produces the testis-determining factor (TDF), which initiates the development of the testis from the primitive sex cords by week 7 of gestation.

Question 2

How does the ovary develop from the indifferent gonad?

Answer 2

Without the influence of the SRY gene, the indifferent gonad develops into an ovary, starting with the formation of cortical cords in the 7th week, which later differentiate into ovarian follicles.

Question 3

What are the key factors that control the descent of the testis into the scrotum?

Answer 3

The descent is influenced by the gubernaculum, increase in intra-abdominal pressure, and hormonal influences such as androgens and Müllerian inhibiting substance.

Question 4

How does the descent of the ovary differ from that of the testis?

Answer 4

The ovary descends to a position just below the pelvic brim, unlike the testis, which descends into the scrotum.

Question 5

What role does testosterone play in the development of male genital ducts?

Answer 5

Testosterone, produced by Leydig cells, induces the differentiation of the mesonephric (Wolffian) ducts into structures such as the epididymis, ductus deferens, and seminal vesicles.

Question 6

What structures develop from the paramesonephric (Müllerian) ducts in females?

Answer 6

The paramesonephric ducts give rise to the uterine tubes, uterus, and the upper part of the vagina.

Question 7

How does the male external genitalia develop?

Answer 7

Under the influence of androgens, the genital tubercle elongates to form the penis, and the genital swellings fuse to form the scrotum.

Question 8

What is the process for the development of female external genitalia?

Answer 8

Oestrogens stimulate the genital tubercle to form the clitoris, the urethral folds to form the labia minora, and the genital swellings to form the labia majora.

Question 9

What is cryptorchidism, and what causes it?

Answer 9

Cryptorchidism is the failure of the testis to descend into the scrotum, often due to abnormal androgen production or issues with the gubernaculum.

Question 10

What are some congenital anomalies associated with the Müllerian ducts?

Answer 10

Anomalies include uterus didelphys (double uterus), bicornuate uterus (two uterine cavities), and septate uterus (divided uterine cavity).

Question 11

What layer forms the gonads

Answer 11

Intermediate mesoderm along posterior wall of abdominal cavity