Lecture 1.2: Origins of the Gametes Flashcards
What is spermatogenesis?
Gamete maturation in males
What is oogenesis?
Gamete maturation in females
How many gametes do males produce?
200million/day
How many gametes do females produce?
12-13/year
What are Gametes?
They are haploid cells that can undergo fusion of their
nuclei at fertilisation to form a zygote
What are the General Principles of Gamete Formation (Gametogenesis)?
Primordial germ cells colonise the primordial gonad (Cortex vs. Medulla of primordial gonad)
After colonising the gonad, PGCs:
* Proliferate by mitosis
* Reshuffle genetically and eventually reduce to
haploid by meiosis
* Cyto-differentiate into mature gametes
Overview of the Formation of the Female Gamete
- Germ cells colonise the gonadal cortex
- Proliferate, by mitosis and become oogonia
- These then turn into primary oocytes which
undergo meiosis - They then arrest at diplotene stage (a resting phase
between prophase and metaphase of the first
meiotic division) until puberty
What are Oogonia? What happens to them?
- Diploid cells
- Proliferate rapidly by several mitotic divisions
- Max numbers reached mid-gestation (7 million)
- Most die during gestation, ie when still a fetus.
What is it called when a primary oocyte gets surrounded by single layer of flat epithelial granulosa
cells?
Primordial Follicle
How many Primordial Follicles is a female born with?
Female is born with ovaries that contain ~2 million primordial follicles
How many Primordial Follicles does a female have at puberty?
40,000
Why is there a decrease in Primordial Follicles between birth and puberty?
Most become atretic in childhood
How long is the average menstrual cycle?
~28 days
What happens in the Menstrual Cycle?: Days 1-7
Uterus lining breaks down and menstruation occurs
What happens in the Menstrual Cycle?: Days 8-11
The lining of the womb thickens in preparation for the egg
