Chapter 1: Gonad Development Flashcards
How long is the indifferent stage for gonad development?
4-7 weeks
What is the indifferent stage of gonad development?
when the gonads initially go through a time where there is no specific ovarian or testicular characteristics
What is the urogenital ridge?
when the indifferent gonads develop into a longitudinal elevation or ridge of intermediate mesoderm
What are the components of the indifferent gonads?
primordial germ cells
primary sex cords
mesonephric (Wolffian) and paramesonephric (Mullerian) ducts
Primordial germ cells are important towards gonadal development in what way?
provide critical inductive influence on gonad development
What do primordial germ cells arise from?
lining cells in the wall of the yolk sac
When do primordial germ cells start migration?
week 4
What are primary sex cords?
finger- like extensions of the surface epithelium which grow into the gonad that are populated by the migrating primordial germ cells
Mesonephric (Wolffian) duct.
ducts of the indifferent gonad that contribute to the male genital tract
Paramesonephric (Mullerian) duct.
duct of the indifferent gonad that contribute to the female genital tract
Sry gene is found on the Y chromosome and enocodes for what?
TDF testis-determining factor
Testosterone is secreted by what cells?
Leydig cells
Mullerian-inhibiting factor is secreted by what cells?
Sertoli cells
DHT helps differentiate what organs?
external genitalia
What hormone is required for development of the ovary and female reproductive system?
estrogen
Ovarian development occurs in the absence of the Sry gene and the presence of what gene?
WNT4 gene
What is synapsis in meiosis I?
pairing of 46 homologous chromosomes
What is crossing over in meisosis I?
exchange of segments of DNA
What is disjunction in meiosis I?
separation of 46 homologous chromosome pairs (no centromere splitting) into 2 daughter cells, each containing 23 chromosome pairs
Draw out the process of meiosis I and meiosis II and label the steps.
See diagram
At week 4 in the process of spermatogenesis, primordial germ cells arrive in the indifferent gonad and remain dormant until what stage in life?
puberty
Describe the process of spermatogenesis.
- When a boy reaches puberty, primordial germ cells differentiate into type A spermatogonia, which serve as stem cells throughout adult life.
- Some type A spermatogonia differentiate into type B spermatogonia
- Type B spermatogonia enter meiosis I to form primary spermatocytes
- Primary spermatocytes form 2 secondary spermatocytes
- Secondary spermatocytes enter meiosis II to form 2 spermatids
- Spermatids undergo spermiogenesis, which is a series of morphological changes resulting in the mature spermatozoa
Describe the process of oogenesis.
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)
- primary oocytes arrested in meiosis I are present at birth
- 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
- the secondary oocyte becomes arrested the second time in metaphase of meiosis II and is ovulated
- at fertilization within the uterine tube, the secondary oocyte completes meiosis II to form a mature oocyte and polar body
