Flashcards in 1.2 Female Deck (27):
How are the ovaries suspended?
Short peritoneal fold of mesentery - mesovarium.
Medially within the mesovarium is a short ovarian ligament that tethers the ovary to the uterus.
What is the ovarian ligament a remnant of?
What is the connective tissue capsule surrounding the ovary?
Tunica albuginea of the ovary - smooth later of ovarian mesothelium - dull/grey
What happens to the ovaries over time?
Epithelium becomes progressively scarred and distorted because of the repeated rupture of ovarian follicles and discharge of oocytes.
Describe the development of oogonia.
Primordial germ cells (from yolk sac wall) colonise the cortex of the primordial gonad and differentiate into oogonia.
Oogonia proliferate rapidly by mitosis.
By the end of 3rd month, oogonia arranged in clusters surrounding by epithelium.
The majority continue to divide by mitosis but some enter meiosis to become primary oocytes (arrest in prophase I)
What stimulates oogonia entry to meiosis
Mesonephric (follicular) cells - flattened epithelial cells that surround the primary oocytes to form primary follicles
When is meiosis arrested and why?
Diplotene stage of prophase due to OMI - oocyte maturation inhibitor secreted from follicular cells.
What is a primary follicle?
Primary oocytes arrested in meiosis I surrounded by a layer of mesonephric epithelia.
When is the max number reached?
Mid gestation (7 mil)
Cell death then begins and many oogonia and primary oocytes degenerate.
Can a woman produce any more oocytes after birth
No, no more formed later, all produced from this stock.
Beginning at puberty, until menopause, a small number of follicles begin further development each day.
What are the stages to form a mature gamete
What happens in the preantral/primordial follicle phase?
Primary oocyte grows dramaticullar but does not restart meiosis
Flat follicular cells become cuboidal granulosa cells.
These secrete glycoprotein to surround the oocyte with zone pellucida.
Surrounding CT cells form a Theca Folliculi:.
Describe the Theca folliculi
Inner theca interna - vascular and endocrine
Outer theca externa - fibrous capsule
Function of theca cells
What happens in the antral/secondary follicular phase?
Granulosa cells continue to proliferate and fluid filled vesicles form between them.
These combine to form the antrum.
As more fluid forms the Graafian follicle expands to 2mm diameter without repro hormone stimulation
What cells do FSH and LH bind to in the astral phase and what doe they cause.
LH - Thecal cells - Secrete androgens, which are converted to oestrogen's by granulosa cells under the influence of FSH.
FSH - Granulosa cells
When does the pre-ovulatory phase begin?
37 hours before ovulation.
What happens in the preovulatory phase?
Oestrogen causes receptors for LH to appear on outer Granulosa cells.
LH surge stimulates these receptors, leading to rapid changes in the follicle.
Within 3 hours of LH surge, follicle restarts meiosis. Division is asymmetric, cytoplasm remains with one daughter cell and the other forms a condensed polar body.
The secondary follicle then enters meiosis II and arrests 3 hours prior to ovulation.
What follows the start of meiosis II in the preovulatory phase?
Follicle size increases dramatically by increase in astral fluid volume to 25 mm diameter
The structure weakens
LH stimulates collagenase activity leading to follicle rupture.
Ovum is carried out in the fluid and gathered up by the fallopian tube fimbriae.
When is meiosis completed
If the ovum is fertilised.
After how many hours do unfertilised cells degenerate?
24 hours after ovulation
What happens to the follicle after ovulation?
Reorganises into the corpus luteum, which secretes progesterone and oestrogen under LH influence. This stimulates the uterine mucosa to enter the secretory stage in prep for embryo implantation.
How long does the corpus luteum live?
14 days before regressing spontaneously in the absence of a fertilised ovum.
What is the corpus albicans and when does it form.
If fertilisation doe snot occur the corpus luteum degenerates and forms a mass of fibrotic scar tissue - corpus albicans.
Progesterone production decreases, precipitating menstrual bleeding.
What happens to the corpus luteum if fertilisation occurs?
Degeneration of CL prevented by hCG secreted by developing embryo.
CL continues to grow and forms the CL of pregnancy
Cells continue to secrete progesterone until month 4 when placenta secretion is adequate alone.
FSH and LH stimulate rapid growth of follicle - mature follicle = graafian follicle
LH surge increases collagenase activity.
Prostaglandins increase response to LH - muscle contraction in ovarian wall.
Oocyte extruded, breaking free of ovary.