Lecture 23: GU System II

Question 1

Describe the bipotentiality of early reproductive system, including the “neutral” gonad and the double duct system

Answer 1

Comparative by potential-can either become male or female=primordial germ cells.

Mesonephric duct: contributes to reproductive system= wolffian duct.

Neutral gonad: has potential of forming either testis or ovary.

Double duct system: paramesonephric (mullerian) ducts form in mesonephric ridge parallel to wolffian ducts.

Question 2

In the development of the reproductive system, why is the female morphology considered to be the “default”?

Answer 2

The gonads are indifferent.

The switch that determines whether the indifferent gonad will develop by default into an ovary or testis is carried on Y chromosome on the SRY (sex-determining region)

Question 3

Describe how “neutral” gonad can morphological form either ovaries or testes

Answer 3

W/in the medulla, solid cords of cells develop. Sex cords [w/in medulla] have the potential to give rise to the seminiferous tubules containing sertoli cells and interstital cells (in even of genetic male).

Anastomosing w/ sex cords in male=rete cords.

Female: medulla regresses and the cortex forms the ovary.

FF=Tunica albuginea: CT separates cortex from medulla. in adult, male=external surface, female=internalized in ovary.

Question 4

List the 2 pairs of ducts that form as part of the indifferent embryonic reproductive system.

Answer 4

1. mesonephric (wolffian): may be used for sperm transport in the male and which degenerate in the female (or else retained in both sexes for urine transport)
2. Paramesonephric (mullerian): used in the female for egg transport. In male, these ducts degenerate.

All vertebrates, sperm and most part, eggs are conducted to the exterior via a closed duct system.

Question 5

Describe the fate of each of the pairs of ducts in the female phenotype and the male phenotype.

Answer 5

Female: rete cords degenerate w/ rest of medulla. Mullerian ducts degenerate b/c presence of Y chromosome. HUMANS HAVE SIMPLEX UTERUS.

Males: mesonephric tubules retained as part of closed duct system that conveys sperm to the exterior. In MALE these are called efferent ductules.

–In most vertebrates mesonephric duct is used mostly/exclusively for sperm transport. When this is the case, it is called a ductus deferens or vas deferens.

Question 6

Describe the comparative anatomy of the reproductive system in various vertebrate groups

Answer 6

Anurans: male frogs, urinary and genital functions and have BIDDER’s organ-rudimentary ovary- can become functional ovary. Gonads are internal. BOTH SEXES HAVE RUDIMENTARY STRUCTURES OF OPPO. SEX.

Placentals/marsupials: viviparous. Internal fertilization. Uteri classification of uteri is based on amt. of fusion in distal mullerian ducts.

Question 7

Describe the external genitalia from a bipotential embryonic condition in mammals.

Answer 7

3 primordia give rise to genitalia:

• Tubercle: glans penis.
• Genital folds: shaft of penis-labia minora
• Genital swelling: scrotum. Labia majora

Question 8

Cortex of indifferent gonad forms the:

Answer 8

Ovary

Question 9

Rete cords and sex cords will degenerate along with the mesonephric tubules and ducts in:

Answer 9

Females

Question 10

This gives rise to the oviducts, uterus, and a portion of the vagina:

Answer 10

Mullerian ducts.