Oogenesis and Spermatogenesis Flashcards
Where does Oogenesis begin
In utero
When is oogenesis completed
Fertilisation
When does oogenesis cease
At the menopause
Describe the production of oocytes
cyclical
What is the earliest recognisable terminal cell
The primordial germ cell
What is a primordial germ cell capable of
Mitosis
Where do primordial germ cells migrate to and when
The genital ridge by week 6 of embryo development
What is one of the two products in the first stage of meiosis
The first polar body
What does the presence of two polar bodies signify
Sperm entry and the completion of the 2nd meiotic division
What is the difference between the divisions in females to males
Unequal division in females
Equal division in males
When is there the largest number of germ cells in the female
8 months of development
Why is there a massive death of germ cells at birth
Unknown
Roughly how many germ cells will be ovulated
400-500
Roughly how many germ cells are females born with
2million
How long does the ovarian cycle last
28 days
What are the 2 phases of the ovarian cycle
Follicular and Luteal
What happens in the follicular phase of the ovarian cycle
Maturation of egg, ready for ovulation at mid-cycle
What signals end of follicular phase
Ovulation
What happens in the Luteal phase of the ovarian cycle
Development of the corpus luteum
Induces preparation of reproductive tract for pregnancy (if fertilisation occurs)
What is the primary follicle
The single layer of granolas cells that surrounds the primary oocyte
What do a lot of primary follicles do before ovulation
Undergo atresia or death
What do follicular cells left behind after ovulation undergo
Luteinisation - transformation to the corpus luteum
What does the corpus luteum secrete
Progesterone
What happens to the corpus luteum after ovulation
It grows for 8-9 days
What happens to the corpus luteum if no fertilisation has occurred
It will survive no longer than 14 days after ovulation
What does the degeneration of the corpus luteum signal
The start of a new follicular phase
What happens to the corpus luteum is fertilisation has occurred
Corpus luteum persists and produces increasing quantities of progesterone and oestrogen until after pregnancy
Where is GnRH secreted from
The hypothalamus
What two hormones does the anterior pituitary secrete that is important in females
FSH and LH
What does FSH do?
Stimulates development of follicles
What does LH do
Stimulates follicule maturation, ovulation and development of the corpus luteum
Where do both LH and FSH act
The ovary
What do FSH and LH stimulate
The secretion of estradiol and ovulation
What do the theca cells produce
Androgen
What is androgen converted to and by what
Oestradiol and by the granulosa
What does estradiol do
Thickens endometrium / thins cervical mucus
What does oestrogen do to FSH
Suppresses the production
What does the granolas in the dominant follicle express
LH receptor
What do high levels of oestrogen at mid cycle cause
hypothalamus to release GnRH
What happens to the levels of LH and FSH during ovulation
The levels fall
How can we detect ovulation
Measure LH levels from a dipstick
In clinic using US
Measuring temperature
What forms the corpus luteum
Remaining granulosa
What does the corpus luteum degenerate to form
The corpus albicans
If pregnancy occurs, what does the developing embryo produce
hCG (chorionic gonadotrophin)
What does hCG do?
Maintains the corpus luteum
The placenta takes over the role of what at around 6 weeks
The corpus luteum
