The fertile female Flashcards
How can you tell when an animal with an oestrus cycle is ready for ovulation?
mainly behaviour
what is ovulation?
release of an ovum
At what point during meiosis do the oocytes pause?
when they are primary immature oocytes
What do the primary immature oocytes associate themselves with?
Primordial follicles
What does the LH surge do in oogenesis?
Forms a secondary oocyte with a polar body
What is a follicle?
a functional unit within the ovary
What is recruitment
when primordial follicles develop in each cycle
What is the zona pellucida?
The outer protective layer of the oocyte
When do the primordial follicles form?
when the primary oocytes do
What layer is avascular and therefore is required for the oocyte to take up nutrients?
Granulosa
What is the function of follicular fluid?
takes up space within the follicle further increasing the size
What triggers ovulation?
Pre-Ovulatory surge
What is another name of a collapsed follicle?
corpora haemorrhagica
What forms after ovulation?
it becomes an oocyte
What is the follicular phase of the menstrual cycle?
When the follicle is developing
What is the luteal phase of the menstrual cycle?
When you have a corpus luteum producing progesterone
What is oestrus a marker of in animals?
The end of the follicular phase/ ovulation
What is the function of prostoglandin?
Main luteolytic agent (causes luteolysis)
What is atresia?
Degradation of the follicles that are not recruited in the menstrual cycle
Which hormone triggers selection?
FSH
When does the oocyte begin meiosis I?
Meiosis I begins before puberty but then the oocyte becomes arrested in prophase I
When is meiosis I completed?
The nuclear arrest is lifted during the LH surge (puberty) so meiosis I is completed and a secondary oocyte forms
What are the two main forms of female reproductive cycle?
The menstrual cycle and the oestrus cycle
What does puberty do to primordial follicles?
Stimulates the development of primary follicles from primordial follicles
What type of follicle is ovulated?
Mature/Graafian follicle
At what stage is the zona pellucida formed?
Primary follicle
At what stage do thecal cells develop around the granulosa cells?
Secondary follicle
What is the function of the follicular fluid (antral cavity)?
To increase follicle size
What is the function of granulosa cells proliferating?
To increase follicular size
How do we protect developing gametes from the blood supply?
Thecal cells, basal lamina and granulosa cells
What is the consequence of granulosa cells being avascular?
No blood cells therefore the granulosa cells must regulate development/ nutrition
What does the binding of androgens to thecal cells on the follicle do?
Stimulates the proliferation of granulosa cells and the production of some oestrogen
What does FSH binding to granulosa cells trigger?
The production of enzymes that produce oestrogen from teh androgens produced by the thecal cells
What does oestradial trigger?
Stimulates even more granulosa cell proliferation
What happens to the endocrine nature of the follicle after the pre-ovulatory LH surge?
Granulosa cells loosen, there is increased blood flow to the theca cells, stops the synthesis of oestrogen and starts synthesising progesterone
When does a secondary oocyte become a zygote?
After it has been fertilized
What do the granulosa cells become after ovulation?
Large luteal cells (high lipid concentration)
What do the thecal cells become after ovulation?
Small luteal cells
When does luteolysis occur?
Over a period of 1-3 days in the late luteal phase
Where is Pgf2A produced?
In primates and dogs- ovary
In most other animals- uterine endometrium
What cells produce oxytocin in response to pgf2a?
The large luteal cells (which also causes positive feedback of even more pgf2a)
When does ovulation occur during the oestrus cycle?
at the end of the follicular phase
What is dioestrus characterised by?
Functional corpus luteum and high progesterone levels
What is proestrus characterised by?
Significant increase in oestradiol
What is oestrus characterised by?
High oestradiol and sexual receptivity
What happens to the egg cell before birth?
Primordial germ cell divides by mitosis to become oogonia/ primary oocyte
Primary oocyte then undergoes meiotic prophase to double its chromatids (46 chromosones/ chromatids to 46 chromosoneds and 96 chromatids) (still 2n)
What occurs to the egg cell post-puberty?
Oogenesis
Once a month an LH surge causes the meiotic arrest to be liftted
Meiosis 1 is completed and a secondary oocyte is formed (n=23)
This oocyte is then ovulated and fertlized producing a 2n zygote
How often is meiosis 1 completed?
It is completed by one primary oocyte each month
What occurs during ovulation in terms of hormones
LH pulses stimulate the granulosa cells to produce estrogen, the increase in estrogen stimulates the pre-ovulatory LH surge (surge centre)
This causes a secondary oocyte to form and ovulate
and changes to occur (granulosa cells loosen, follicle size increases, granulosa cells withdraw from the zona pellucida)
Less estrogen is produced and more progesterone is produced
What is a corpus hemorrhagicum?
ruptured follicle
What is the fate of the follicle after ovulation?
Fibrin core forms a blood clot, granulosa and thecal cells break down
Basal lamina breaks down
Granulosa cells hypertrophy to large luteal cells
Theca cells become small luteal cells
