Menstrual Cycle

Question 1

Ovarian and Uterine Cycles overview

Answer 1

Ovarian:
Follicular phase
Ovulatory phase
Luteal phase

Uterine:
Menses
Proliferative
Secretory

Question 2

Ovarian early follicular phase:

Answer 2

FSH stimulates tertiary follicle maturation

Granulosa → AMH
- AMH ⊣ other follicles developing

Theca cells → androgens (aromatase converts to estrogens)
- Low estrogen exerts negative feedback on GnRH/FSH/LH

Question 3

Ovarian mid-late follicular phase:

Answer 3

Positive feedback loop of estrogen driving endometrial thickening

Estrogen + rising progesterone → LH surge

Question 4

Ovulatory phase

Answer 4

Inflammatory leukocyte secrete prostaglandins

Follicle rupture/release of oocyte

Question 5

Ovarian early-mid luteal phase:

Answer 5

Granulosa/theca cells become luteal cells and secrete progesterone + inhibin

Deposition of lipids/glycogen in endometrium

Cervical mucus thickening

Question 6

Ovarian late luteal phase

Answer 6

No pregs → corpus luteum → corpus albicans

↓ progesterone + estrogen, FSH + LH ↑ again

Endometrium sloughs off → menstruation

Question 7

Uterine cycle: menses

Answer 7

Loss of superficial layers of secretory endometrium

Corresponds with early follicular phase

Question 8

Uterine cycle: proliferative phase

Answer 8

New layers of endometrium to prepare uterus for egg

Corresponds with mid-late follicular phase

Question 9

Uterine cycle: Secretory phase

Answer 9

Thick endometrium becomes secretory structure

Signaled by hormones from corpus luteum

Corresponds with luteal phase

Question 10

Follicular development 7 steps

Answer 10

1) Primordial (primary oocyte encircled by granulosa cells + basal lamina)

2) Primary follicle + granulosa divide (then puberty)

3) Secondary follicles + theca cells develop outside basal lamina → tertiary follicle + antral fluid w/ hormones/enzymes

4) One dominant follicle (others don’t survive)

5) Oocyte released

6) Corpus luteum (granulosa/theca cells) develops into luteal cells

7) No pregnancy: corpus luteum –> corpus albicans

Question 11

Fertilization to implantation

Answer 11

Day 1: fertilization

Days 2-4: Preimplantation begins (embryo development). Zygote begins mitosis, forming the embryo, as it makes its way to the uterus.

Days 3-5: Blastocyst (hollow ball of about 100 cells) reaches the uterus.

Days 5-9: Implantation occurs. Blastocyst implants in endometrium.

Chorion: formed from outer layer of cells → placenta → chorionic villi form as embryo forms which penetrate endometrium

Inner cells to form: embryo, plus amnion, allantois (umbilical cord to be), yolk sac
Endometrial cells engulf blastocyst
Corpus luteum requires hormonal influence to not go inactive

Question 12

Extra-embryonic membranes:

Answer 12

Extraembryonic membranes: membranes surrounding the embryo.

Chorion: encloses embryo and eventually forms placenta

Amnion: secreted amniotic fluid

Allantois: become part of umbilical cord

Yolk sac: degenerates early in development.

Question 13

Human chorionic gonadotropin (hCG) during pregnancy

Answer 13

Maintains corpus luteum (structurally related to LH) to maintain progesterone production keeping endometrium intact. Chemically detected in a pregnancy test.

Question 14

Human chorionic somatomammotropin (hCS/hPL) during pregnancy

Answer 14

Alters maternal glucose and FA metabolism to support fetal growth.

Necessary for breast development and lactation.

Question 15

Estrogen and progesterone roles during pregnancy

Answer 15

Estrogen: Continuously produced through pregnancy, helps develop milk-secreting ducts in breasts. Inhibit secretion of milk.

Progesterone: Continuously produced through pregnancy, maintains endometrium.

Converts milk duct epithelium into secretory structure (late pregnancy), Inhibit secretion of milk.

Production taken over by placenta after corpus luteum degenerates.