Physiology of menstrual cycle and pharmacological interruptions Flashcards Preview

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How many eggs roughly do females have at the following life stages:
1.) before birth
2.)At birth
3.) First period
4.) Menopause

1.) 7 million
2.) 2 million
3.) 0.5 million


Describe the normal development of an ovarian follicle including the relative lengths

Primordial follicle=0.4um
Primary follicle= 100um
Secondary follicle= 200um
Early tertiary follicle= 400um


What is the corpus luteum

A hormone-secreting structure that develops in an ovary after an ovum has been discharged but degenerates after a few days unless pregnancy has begun.


Describe the 3 phases of the ovulation cycle

1.) Follicular phase: day 1-10; hormones signal 10-20 follicles to grow on ovary; oestrogen matures one oocyte
2.) Ovulation phase : day 11-14; Oocyte undergoes division; follicle wall thins and ruptures, oocyte enters abdominal cavity near fimbrae of fallopian tube
3.) Luteal phase: Days 14-28; oestrogen levels drop; egg travels through fallopian tube towards uterus.


When do FSH and LH levels peak?

During ovulation


Explain the FSH threshold-window concept

FSH is produced in the brain.Increased FSH makes several follicles grow. The bigger the follicles get, the more oestrogen they produce. A certain level of oestrogen makes the FSH level drop. This drop in FSH removes the competition, hence only one follicle grows, leading to one baby.


How is the oocyte propelled through the fallopian tube and into the uterus.

By the fallopian tube contractions and the cilia


What do the fimbrae do shortly before ovulation?

Sweep over the surface of the ovaries


What is the function of LH

Signals to the egg,allowing it to be released


What are the two layers of the endometrium and their function.

Stratum functionalis: Thick superficial layer that is sloughed off during menstruation and grows anew during each cycle

Stratum basalis layer is the deepest tissue of endometrium and is adjacent to the myometrium. It is the constant layer of endometrium, that does not undergo conformational changes during the uterine cycle and its purpose is to replace the tissue loss during the menstruation, so it gives rise to the new stratum functionalis.


When does implantation take place?

Begins by day 6-7 after ovulation (day 21 of menstrual cycle)


Which reproductive hormone act directly on the ovaries and what do they do?

- Estrogens: promotes maturation of reproductive organs,development during puberty,regulates menstrual cycle, pregnancy
-Progesterone: helps maintain the uterine lining ( ='pro-gestation'). Promotes breast development, regulates menstrual cycle, sustains pregnancy
-FSH: regulates ovarian function and maturation of ovarian follicles
-LH: Assists in production of estrogen and progesterone,regulates maturation of ovarian follicles,triggers ovulation
-Human chorionic gonadotrophin: helps sustain pregnancy
-Testosterone: helps stimulate sexual interest
-Oxytocin: stimulates uterine contractions in child birth
-prolactin: stimulates milk production
-prostaglandins: mediates hormone response and stimulates muscle contractions


Describe the follicle-stimulating hormone receptor.

A transmembrane receptor that interacts with the follicle-stimulating hormone and which represents a GPCR


What is the menstrual cycle?

A series of cyclic changes in the endometrium(inner lining of uterus) in response to changes in the levels of ovarian hormones


What is the function of GnRH?

Its found in the hypothalamus. It promotes maturation of the gonads and regulates the menstrual cycle.


List the gonadotrophic hormones



Describe the menstrual phase (day 1-5)

The functional layer of the endometrium becomes detached from the uterine wall, resulting in bleeding (menses)


Describe the proliferative phase (day 6-14)

Gonadotrophin releasing hormone stimulates release of FSH & LH which cause follicular development. This causes an increase in the levels of oestrogen as they grow and thus the endometrium begins to proliferate and thicken, tubular glands and spiral arteries form. There is also stimulation of progesterone receptors synthesis in endometrial cells.


Describe the secretory phase ( day 15-22)

There are rising levels of progesterone.
Enlargement of glands which begin secreting mucus and glycogen in prep. for implantation of the fertilized ovum. Increased fluid (oedema) in the stroma


What day does the progesterone peak occur on?

Day 21


Describe the hypothalamic-pituitary-ovarian axis

The hypothalamus releases GnRH which stimulates gonadotrophs on the anterior pituitary to release LH/FSH this acts on the ovary to stimulate the release of estrogen/ progesterone to act on the uterus


Explain which aspects may give rise to gonadal dysfunction

1.)Problem with the driver:
2.)Problem with the functional units(follicles):
3.)Problem with the receiver:


What can cause hypoestogenic status?

-anorexia nervosa
-iatrogenic treatment
-functional hypothalamic amenorrhea
-ovarian failure
-post menopausal women


What can cause hyperandrogenic status?

-tumors of the ovary


What causes anovulation

-Hypothalamic dysfunction
-Pituitary dysfunction
-Thyroid dysfunction
-Ovarian failure


What are the most common causes of ovulatory dysfunction?

-PCOS ( woman has a lot of follicles but they arent released in a timely manner)
-hypothalamic amenorrhea (menstruation stops for several months due to a problem involving the hypothalamus)
-hyperprolactinemia (prolactin produced in the brain at high conc. may suppress ovulation)
-premature ovarian failure (woman has no eggs)


What are the complications of being an obese woman in terms of fertility.

-reduced fertility
-higher rates of miscarriage
-require higher doses of ovulation-inducing agents


What should be the first line of treatment in obese women with anovulatory infertility and why?

Weight loss, because it...
-restores ovulation
-achieves spontaneous prgenancy
-is effective and cheap
-has no side effects


What are central obesity and BMI major determinants of?

-insulin resistance


What are the effects of clomiphene citrate and how does it work?

-FSH stimulates ovulation
-clomiphene citrate stimulates endogenous FSH production
-should be first line of treatement for those with absent/irregular ovulation but who have normal basal levels of endogenous estradiol
-It's a blocker of oestrogen receptors in the pituitary gland
-These people don't have cyclical FSH