Female reproductive Flashcards
What are the two main functions of the ovary?
Produce haploid gametes capable of being fertilized
Produce sex hormones: oestrogen progesterone, and peptides (e.g. inhibin, activin) which act both systemically and locally.
When does meiosis of gametes occur in females?
Starts and arrests in foetal life
After birth what slowly happens to the follicles?
Atresia (apoptosis)
How many primary oocytes are produced?
6-7million
How many oocytes does a woman ovulate in her lifetime?
~400
What does a follicle consist of?
Primary oocyte, surrounded by its zona pellucida, granulosa cells and later, thecal cells
What substance surrounds the primary oocyte?
Zona pellucida - glycoprotein
What does interstitial tissue of ovary contain?
Corpora lutea and corpora albicantia from previously ovulated follicles/ matter from atretic follicles
Connective tissue, vessels and nerves.
What junctions link granulosa cells?
Gap junctions
How many layers of the thecal cells surround a follicle?
2, inner theca interna and outer theca externa
What is the role of the theca interna cells?
Secrete androgens
What is the role of the theca externa?
Protective capsule
After the primary oocyte leaves the follicle in ovulation, what forms the corpus luteum?
Granulosa and theca interna cells
When is day 1 of the menstrual cycle?
The first day of menstruation
How many days does the menstrual cycle last?
~28 days
What determines length of the menstrual cycle?
Follicle growth and corpus luteum lifespan
What are the two phases of the menstrual cycle and why are they named as such?
During the first half the reproductive system is dominated by a developing follicle (follicular phase)
After ovulation products of the corpus luteum dominate (luteal phase).
What triggers puberty?
Activation of kisspeptin neurones
What does kisspeptin activation stimulate?
Release of hypothalamic GnRH
What does GnRH stimulate?
Release of FSH and LH from the anterior pituitary
When to primordial follicles appear?
16-24 weeks gestation
What are the layers of the primordial follicle?
Primary oocyte surrounded by a single layer of flat pregranulosa cells
What happens in the initial stage of follicle development?
Primary oocyte enlarges and the granulosa cells become rounded to produce a primary follicle
What does a primordial follicle develop into?
Primary follicle
How does a primary follicle change into a secondary follicle
Mitosis in the single layer of granulosa cells and differentiation of surrounding stromal cells to form thecal cells produces a secondary follicle.
Granulosa cells have FSH receptors and the thecal cells LH receptors.
What happens when secondary follicles are stimulated by FSH
Secrete fluid which coalesces to form an antrum and the follicle is called an early antral (tertiary) follicle.
Which follicular cells bind to FSH and which to LH
Granulosa cells have FSH receptors and the thecal cells LH receptors.
What is a Graafian follicle?
Mature tertiary/antral follicle
Which granulosa cells are shed with the oocyte at ovulation?
Cumulus granulosa cells
What happens when primary oocyte undergoes meiosis I?
2n primary oocyte splits into secondary (n) oocyte and polar body (n)
What does FSH cause granulosa cells to do?
Stimulates their division
Stimulates the secretion of antral fluid
Activating them to convert the androgens provided by the thecal cells to oestrogen by stimulating production of aromatase
Stimulates production of peptide hormones and growth factors
Stimulates the production of LH receptors in selected follicles.
What does LH cause thecal cells to do?
Causes them to grow and divide
Secrete androgens
When do LH receptors develop on mural granulosa cells?
When the dominant follicle (stimulated by FSH) has been selected for ovulation during a cycle.
When is FSH high in the menstrual cycle?
At the end of the luteal phase and in the early follicular phase to stimulate follicle growth
Why does FSH decline through the follicular phase?
Negative feedback of inhibin and oestrogen from the developing follicle.
When is the LH surge?
Just before ovulation
What causes the follicle rupture and oocyte release?
LH surge
What is leuteinization?
The conversion of remaining follicle cells to corpus luteum
How many days does the corpus luteum grow for?
Roughly 7
Why is FSH low in luteal phase?
Negative feedback of oestrogen and progesterone
What allows FSH to increase again at the end of the luteal phase?
Corpus luteum starts to degenerate, falling steroid production allows FHS to rise again.
Why is LH low in the luteal phase?
Progesterone released by the corpus luteum inibits it
What does elevated FSH early in the menstrual cycle achieve?
Stimulates the development of a cohort of follicles
Why is background LH production needed early in the menstrual cycle?
So thecal cells produce androgens which is converted to oestrogen by granular cells (stimulated by FSH)
What effects does oestrogen (oestrodiol) have ?
Local effects within the ovary
Effects on the uterine tube/uterus stimulating the proliferative phase of the endometrium, and on the cervix/vagina
Feedback: As the follicle starts to produce oestradiol this (with inhibin) inhibits the secretion of FSH.
Sensitise the pituitary to GnRH by what is called a ‘positive feedback’ mechanism, preparing the gonadotrophs to release massive amounts of LH (LH surge) just before ovulation.
What does inhibin do?
Local actions to stimulate production of androgens by the theca and an endocrine action to suppress FSH secretion by the pituitary.
Where does activin act?
Within the ovary
What does follistatin act as?
Activin-binding protein
What is the benefit of FSH inducing expression of LH receptors on mural granulosa cells?
So they are maximally responsive to LH at the time of the LH surge.
What does the LH surge cause (4)?
The oocyte to enter the 2nd meiotic division
Release of the oocyte and its cumulus of granulosa cells by inducing degenerative changes in the follicle wall
In-growth of blood vessels through the ruptured basal lamina
Steroidogenic enzymes expressed by luteal cells secrete progesterone, with some oestradiol.
What happens to the tertiary follicle in meiosis II?
Extrudes 1 polar body
What does progesterone released by corpus luteum have effect on?
On the uterus to induce the secretory phase of endometrial activity
On the pituitary and hypothalamus to cause negative feedback, decease GnRH
Is the corpus luteum an endocrine gland?
Yes, a temporary one
Without HcG what becomes of the corpus luteum after 7 days?
Luteolysis - corpus luterum regresses
What happens as the corpus luteum regresses?
Progesterone levels fall
Negative feedback on FSH and LH is removed so increased level of FSH causes another wave of follicles to grow
What causes luteolysis in humans?
Unknown, likely that a paracrine event controls human luteolysis
This is blocked by human chorionic gonadotrophin (hCG) which rescues the corpus luteum and allows pregnancy to proceed.
What triggers the menopause?
Number of oocytes is severely depleted - failure of follicular development -secretion of oestrogens and inhibins is drastically reduced
What does low oestrogen/inhibins cause?
Lack of negative feedback at the pituitary and excessive secretion of LH and FSH
Lack of oestrogen action on a variety of tissues including bone, skin, hair, liver, cause osteoporosis, thinned skin and hair, and an unwanted rise in plasma cholesterol and attendant increase in cardiovascular disease.
What can be used to can be used to stimulate the onset of parturition?
Prostaglandins
What happens to the endometrium in the follicular/proliferative phase?
Grows and proliferates
When are spiral arteries most prominent in endometrium?
Luteal phase
What stimulates secretion from the endometrial glands?
Progesterone
How do endometrial glands appear in the proliferative phase and why?
Uterine glands appear long due to oestrogen secretion by the ovaries.
What stimulates growth/increased blood flow of the spiral arteries?
Increased progesterone secretion
In the luteal phase what happens to the endometrial glands?
Become very coiled with wide lumens and produce a glycogen-rich secretion.
The phase of meiosis in which the mature oocyte is arrested prior to fertilisation?
Metaphase of meiosis 2
The phase of meiosis when homologous chromosomes recombine ?
Prophase of meiosis 1
What structure does the embryo absorb oxygen across?
Placental villi
During an unfertilised menstrual cycle endometrial growth …
Involves both hyperplasia and hypertrophy
What does the corpus luteum become?
Corpus albicans
What hormone secretion is a sign ovulation has occurred?
Progesterone
Which hormone remains low in concentration during the luteal phase due to steroid negative feedback until the corpus luteum begins to degenerate?
FSH
What happens to the stimulated follicles that don’t get ovulated?
Atresia
The layer of cells that surrounds the oocyte and protects it during ovulation …
Corona radiata
A hormone that has a relaxant effect on uterine smooth muscle during pregnancy…
Progesterone
A hormone that increases gap junction proteins in uterine smooth muscle cells to ensure contractions are in synchrony in childbirth…
Estradiol
Are egg cells haploid?
No, unless selected, paused in prophase I (diploid)
Do follicles depend on Oestrogen for development?
No, FSH
What day of the menstrual cycle is the endometrium at its thickest?
21
After menstruation, what part of the endometrium tissue remains?
Straight part of arteries and base of glands
The phase of meiosis oocytes are stored in the ovary prior to preovulatory LH surge?
Prophase I
