Chapter 1: Gonad Development

Question 1

How long is the indifferent stage for gonad development?

Answer 1

4-7 weeks

Question 2

What is the indifferent stage of gonad development?

Answer 2

when the gonads initially go through a time where there is no specific ovarian or testicular characteristics

Question 3

What is the urogenital ridge?

Answer 3

when the indifferent gonads develop into a longitudinal elevation or ridge of intermediate mesoderm

Question 4

What are the components of the indifferent gonads?

Answer 4

primordial germ cells
primary sex cords
mesonephric (Wolffian) and paramesonephric (Mullerian) ducts

Question 5

Primordial germ cells are important towards gonadal development in what way?

Answer 5

provide critical inductive influence on gonad development

Question 6

What do primordial germ cells arise from?

Answer 6

lining cells in the wall of the yolk sac

Question 7

When do primordial germ cells start migration?

Answer 7

week 4

Question 8

What are primary sex cords?

Answer 8

finger- like extensions of the surface epithelium which grow into the gonad that are populated by the migrating primordial germ cells

Question 9

Mesonephric (Wolffian) duct.

Answer 9

ducts of the indifferent gonad that contribute to the male genital tract

Question 10

Paramesonephric (Mullerian) duct.

Answer 10

duct of the indifferent gonad that contribute to the female genital tract

Question 11

Sry gene is found on the Y chromosome and enocodes for what?

Answer 11

TDF testis-determining factor

Question 12

Testosterone is secreted by what cells?

Answer 12

Leydig cells

Question 13

Mullerian-inhibiting factor is secreted by what cells?

Answer 13

Sertoli cells

Question 14

DHT helps differentiate what organs?

Answer 14

external genitalia

Question 15

What hormone is required for development of the ovary and female reproductive system?

Answer 15

estrogen

Question 16

Ovarian development occurs in the absence of the Sry gene and the presence of what gene?

Answer 16

WNT4 gene

Question 17

What is synapsis in meiosis I?

Answer 17

pairing of 46 homologous chromosomes

Question 18

What is crossing over in meisosis I?

Answer 18

exchange of segments of DNA

Question 19

What is disjunction in meiosis I?

Answer 19

separation of 46 homologous chromosome pairs (no centromere splitting) into 2 daughter cells, each containing 23 chromosome pairs

Question 20

Draw out the process of meiosis I and meiosis II and label the steps.

Answer 20

See diagram

Question 21

At week 4 in the process of spermatogenesis, primordial germ cells arrive in the indifferent gonad and remain dormant until what stage in life?

Answer 21

puberty

Question 22

Describe the process of spermatogenesis.

Answer 22

1. When a boy reaches puberty, primordial germ cells differentiate into type A spermatogonia, which serve as stem cells throughout adult life.
2. Some type A spermatogonia differentiate into type B spermatogonia
3. Type B spermatogonia enter meiosis I to form primary spermatocytes
4. Primary spermatocytes form 2 secondary spermatocytes
5. Secondary spermatocytes enter meiosis II to form 2 spermatids
6. Spermatids undergo spermiogenesis, which is a series of morphological changes resulting in the mature spermatozoa

Question 23

Describe the process of oogenesis.

Answer 23

At week 4, primordial germ cells arrive in the indifferent gonad and differentiate into oogonia, Oogonia enter meiosis I to form primary oocytes.
(all primary oocytes are formed by month 5 of fetal life; they are arrested the first time in prophase (diplotene) of meiosis I and remain arrested until puberty)

1. primary oocytes arrested in meiosis I are present at birth
2. When a girl reaches puberty, during each monthly cycle a primary ooccyte becomes unarrested and completes meiosis I to form a secondary oocyte and polar body
3. the secondary oocyte becomes arrested the second time in metaphase of meiosis II and is ovulated
4. at fertilization within the uterine tube, the secondary oocyte completes meiosis II to form a mature oocyte and polar body