Ovarian Cycle and Conception

Question 1

Menstrual Cycle

Answer 1

controlled by hypothalamic-pituitary-ovarian (HPO)
28 day cycle

Question 2

3 phases of ovarian cycle

Answer 2

Follicular/preovulatory phase
Ovulation
Luteal Phase

Question 3

Day 0-13 Follicular/preovulatory phase

Answer 3

Increased FSH (Follicle-Stimulating Hormone): Stimulates the growth of ovarian follicles.

Low LH (Luteinizing Hormone): Remains low during this phase.

Estrogen Rising: Follicles produce estrogen, which stimulates the thickening of the uterine lining (endometrium).

The dominant follicle produces more estrogen as it matures.
Ovary & Follicle Development:
Multiple follicles begin to mature, but usually only one becomes dominant.

The dominant follicle produces more estrogen as it matures.

Endometrial Changes:
The lining of the uterus begins to thicken in preparation for a possible pregnancy.

Physical Signs:
Menstruation occurs at the beginning of the phase (Day 0).

As estrogen rises, women may experience increased cervical mucus, which is thinner and more elastic, aiding sperm motility.

Key Event: The follicular phase ends with the surge in LH (around Day 13) which triggers ovulation.

Question 4

Day 14-Ovulation

Answer 4

eggs released
The dominant follicle bursts, releasing the mature egg (oocyte) into the fallopian tube (this is ovulation).

The ruptured follicle transforms into the corpus luteum, which starts producing progesterone to prepare the endometrium for potential pregnancy.

Question 5

Day 15, 28-Luteal Phase

Answer 5

Increased Progesterone: After ovulation, the ruptured follicle transforms into the corpus luteum, which secretes progesterone. This hormone maintains the uterine lining (endometrium) for a potential pregnancy.

Estrogen Levels: Estrogen levels remain moderately high but lower than during the follicular phase.

Low LH and FSH: Both luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels decrease.

Ovary & Follicle Activity:
The corpus luteum continues to secrete progesterone for about 10-12 days, supporting the thickened uterine lining.

If pregnancy does not occur, the corpus luteum degenerates, leading to a drop in progesterone and estrogen levels.

Question 6

Conception

Answer 6

5 days before ovulation
Mitosis-cell duplication
Meiosis-production of gametes
Blastocyst-inner cell mass which forms embryo and trophoblast

Question 7

Implantation

Answer 7

Blastocyst embeds in uterine endometrium
-7 days after ovulation
-occurs day 20-22
-conceptus is called embryo until week 8 and becomes fetus
Folding of embryo-forms basis of early development of organs-embryo changes shape

Question 8

Maintenance of early pregnancy

Answer 8

hCH from trophoblast cells enters maternal blood stream
hCH maintains corpus luteum
Corpus Luteum provides progesterone & Oestrogen for maintenance until week 10

Question 9

Early Embryogenesis

Answer 9

Blastocyst travels through fallopian tube until implanted un uterus-fertilisation occurs-zygote

Question 10

Viability

Answer 10

Capability of an independent exidtence outside woman’s uterus
-neonate born between 23 and 24 weeks and 6 days

Question 11

Teratogens

Answer 11

external agent mother is exposed to such as drugs, environment, infections and diabetes