1.2 Female

Question 1

How are the ovaries suspended?

Answer 1

Short peritoneal fold of mesentery - mesovarium.

Medially within the mesovarium is a short ovarian ligament that tethers the ovary to the uterus.

Question 2

What is the ovarian ligament a remnant of?

Answer 2

Gubernaculum

Question 3

What is the connective tissue capsule surrounding the ovary?

Answer 3

Tunica albuginea of the ovary - smooth later of ovarian mesothelium - dull/grey

Question 4

What happens to the ovaries over time?

Answer 4

Epithelium becomes progressively scarred and distorted because of the repeated rupture of ovarian follicles and discharge of oocytes.

Question 5

Describe the development of oogonia.

Answer 5

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)

Question 6

What stimulates oogonia entry to meiosis

Answer 6

Mesonephric (follicular) cells - flattened epithelial cells that surround the primary oocytes to form primary follicles

Question 7

When is meiosis arrested and why?

Answer 7

Diplotene stage of prophase due to OMI - oocyte maturation inhibitor secreted from follicular cells.

Question 8

What is a primary follicle?

Answer 8

Primary oocytes arrested in meiosis I surrounded by a layer of mesonephric epithelia.

Question 9

When is the max number reached?

Answer 9

Mid gestation (7 mil)
Cell death then begins and many oogonia and primary oocytes degenerate.

Question 10

Can a woman produce any more oocytes after birth

Answer 10

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.

Question 11

What are the stages to form a mature gamete

Answer 11

Preantral
Antral
Preovulatory

Question 12

What happens in the preantral/primordial follicle phase?

Answer 12

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:.

Question 13

Describe the Theca folliculi

Answer 13

Inner theca interna - vascular and endocrine

Outer theca externa - fibrous capsule

Question 14

Function of theca cells

Answer 14

Secrete oestrogens

Question 15

What happens in the antral/secondary follicular phase?

Answer 15

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

Question 16

What cells do FSH and LH bind to in the astral phase and what doe they cause.

Answer 16

LH - Thecal cells - Secrete androgens, which are converted to oestrogen’s by granulosa cells under the influence of FSH.
FSH - Granulosa cells

Question 17

When does the pre-ovulatory phase begin?

Answer 17

37 hours before ovulation.

Question 18

What happens in the preovulatory phase?

Answer 18

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.

Question 19

What follows the start of meiosis II in the preovulatory phase?

Answer 19

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.

Question 20

When is meiosis completed

Answer 20

If the ovum is fertilised.

Question 21

After how many hours do unfertilised cells degenerate?

Answer 21

24 hours after ovulation

Question 22

What happens to the follicle after ovulation?

Answer 22

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.

Question 23

How long does the corpus luteum live?

Answer 23

14 days before regressing spontaneously in the absence of a fertilised ovum.

Question 24

What is the corpus albicans and when does it form.

Answer 24

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.

Question 25

What happens to the corpus luteum if fertilisation occurs?

Answer 25

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.

Question 26

Describe ovulation

Answer 26

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.

Question 27

Compare spermatogenesis and oogenesis

Answer 27

Sperm:
200 mil per day
O:
1 per 28 day cycle
S:
4 formed with equal division of cytoplasm.
O:
One with unequal division and 2 polar bodies formed.
S:
Starts at puberty
O:
starts in fetes
S:
Continues through adult life
O:
Ends at menopause
S:
Motile
O:
Non motile
S:
All stages complete in testes
O:
Last stage of meisosi II in oviduct