Female Physiology before Pregnancy and Female Hormones

Question 1

Reproductive Organs

Major anatomical structures of the Female Reproductive System

Answer 1

Vaginal canal

Uterine (Fallopian) tube

Ovary

Uterus

Question 2

The function of the Female Reproductive System

Answer 2

Vagina:
-Connects uterus with exterior

Uterine (Fallopian) tubes
-Carry oocytes to uterus - if sperm reaches oocyte,
fertilization is initiated and oocyte matures into ovum

Ovaries or female gonads:

• Release one immature gamete (oocyte) per month
• Produce hormones

Uterus:
-Encloses and supports developing embryo

Question 3

What is Oogenesis

Answer 3

A process that results in one ovum (matured oocyte)

production which begins before birth and it is accelerated at puberty (hormonal influence) and ends at menopause

Question 4

Oogenesis-Before birth (Fetal development)

Answer 4

Primordial germ cells migrate to the outer surface of the Ovary to reach the germinal epithelium and form
Oogonia/Primordial Ova (reproductive stem cells).

Oogonia collects around a unilayer of epithelial cells
(granulosa cells) that will start the “Follicular Phase”

Oogonia undergo mitotic proliferation to develop into
Primary Oocytes.

Meiosis I proceeds between 3rd and 7th month of
development and is suspended until puberty is reached.

Question 5

Oogenesis(Puberty)

Answer 5

After puberty the surge in Follicle Stimulating Hormone(FSH), trigger the start of the Ovarian Cycle.

Meiosis I is completed just before ovulation, giving rise to a haploid Secondary oocyte.

A Secondary oocyte is released during Ovulation but is suspended in Metaphase of Meiosis II.

Meiosis II is completed if ovum is fertilized by a
spermatozoa giving rise to diploid fertilized ovum

Question 6

Hormonal System

Answer 6

Two hormonal secretory systems namely Pituitary Gland as well as the Ovaries.

Gonadotropin releasing hormone (GnRH) is released by the hypothalamus to act on the Anterior Pituitary gland.

Anterior Pituitary Gland secretes the following hormones:

• Follicle-stimulating hormone (FSH)
• Luteinizing hormone (LH)

Ovaries secrete the following hormones:

• Estrogen (Target cells: Granulosa cells)
• Progesterone (Target cells: Theca cells)

Question 7

Hormonal System(2)

Answer 7

The amount of GnRH released increases and decreases during the female sexual cycle.

Changes in GnRH pulse frequency are controlled by:

• Estrogens that increase pulse frequency
• Progestins that decrease pulse frequency

This completes a feedback system of hormonal regulation

Question 8

Ovarian Cycle

Answer 8

The ovarian cycle is divided into:

• Follicular phase (pre-ovulatory phase)
• Luteal phase (postovulatory phase)

Question 9

Follicular Phase

Answer 9

Oogonia surrounded by single layer of granulosa cells form Primordial follicles.

Granulosa cells supply nourishment to the developing oogonia.

After the onset of puberty and secretion of FSH and LH, follicles grow in diameter as more layers of granulosa cells accumulates on the outside

This develops into Primary follicles

Question 10

Ovarian Cycle - Follicular Phase

Answer 10

This phase is dominated by the secretion of FSH more so than LH

FSH cause rapid proliferation of primary follicles including layers of granulosa cells

A second mass of cells arise outside the granulosa cells, known as theca cells

Theca cells adopt the epithelial characteristics of granulosa cells promoting the secretion of sex hormones

Granulosa cells secrete a follicular fluid that contains a
significant concentration of estrogen.

Accumulation of follicular fluid inside the Primary follicle forms an antrum between the granulosa cells

The accelerated growth of the Primary follicle
predominately under FSH stimulation causes an increase in FSH receptors aiding to a positive FSH feedback system

FSH from the Pituitary gland and Estrogen released by the granulosa cells promotes the insertion of LH receptors on the granulosa cells

Thus permitting granulosa cells to be stimulated by both LH and FSH.

In addition, the increase in estrogen and now LH act
together to increase proliferation of theca cells.

ONE follicle will outgrow the remaining follicles, that will undergo atresia.

Possible reason for involution is the feedback system of the large quantities of estrogen secreted by the granulosa cells, that act on the hypothalamus to inhibit further secretion of FSH.

This will curb the growth of the remaining primary follicles while continuing to sustain growth in the follicle due to their large numbers of granulosa cells and thus higher concentration of estrogen.

The single large follicle known as mature follicle.

Question 11

Ovulation

Answer 11

Occurs around day 14 of the normal 28-
day sexual cycle.

LH is essential in the final stage of follicular growth and is required for Ovulation.

LH surge hours before onset of Ovulation and act on both granulosa and theca cells.

LH converts both cells into progesterone-secreting cells whilst estrogen secretion ceases.

NB. Without the pre-ovulatory surge of LH, ovulation will not occur!

Question 12

Ovulation initiation by LH

Answer 12

LH surge causes release of progesterone.

Causing theca externa cells to release proteolytic
enzymes – digestion follicle wall.

Follicle wall is weakened resulting in increase swelling of the follicle.

At the same time vascularization in wall of follicle

Results in follicle rupture and release of ovum.

Question 13

Involution of Corpus luteum

Answer 13

The Corpus Luteum involute 12 days after ovulation and lose it’s secretory function and it’s yellow characteristic.

This is due to estrogen secretion that play a feedback role in decreasing the release of FSH and LH.

The lutein cells secrete inhibin that further prevents the anterior pituitary gland from secreting FSH.

The corpus luteum degenerate and develops into the corpus albicans.

Involution removes the feedback inhibition increasing FSH and LH.

FSH and LH stimulate new follicle development during a new ovarian cycle.

Question 14

Functions of the Ovarian Hormones

Answer 14

Estrogens promote growth of cells responsible for sexual characteristics.

Progestins function predominantly to prepare the uterus for pregnancy.

The most important estrogen is ß-estradiol and progestin is progesterone.

Question 15

Synthesis of Estrogens and Progestins

Answer 15

In ovaries mainly from cholesterol

Progesterone and androgens (male hormones) are
synthesized first.

During the follicular phase in the ovaries, androgens and progesterone are converted to estrogens in granulosa cells by aromatase.

Theca cells do not possess aromatase however androgens diffuse out of theca cells into adjacent granulosa cells

They are converted to estrogens by the enzyme

Question 16

Estrogens and Progesterone Are Transported

in the Blood Bound to Plasma Proteins

Answer 16

Both estrogens and progesterone are transported in the blood bound mainly with plasma albumin and with
specific estrogen- and progesterone-binding globulins

Question 17

Fate of Progesterone

Answer 17

Progesterone is degraded to other steroids that have no progestational effect.

For estrogens, the liver is especially important for this
metabolic degradation.

The major end product of progesterone degradation is
pregnanediol.

Question 18

Functions of the Liver in Estrogen Degradation

Answer 18

The liver converts estradiol and estrone into the almost
totally impotent estrogen estriol.

Therefore, diminished liver function actually increases
the activity of estrogens in the body, sometimes causing hyperestrinism.

Question 19

Estrogen function on the Uterus and Sex

organs

Answer 19

Estrogen stimulates the growth of external genitalia
including the female sex organs.

Estrogen change the vaginal epithelium into a more
resistant stratified cell type.

Estrogen causes increase in size of uterus as well as
proliferation of the endometrial glands and stroma.

Question 20

Estrogen function on Fallopian tubes and

Breast

Answer 20

Estrogen stimulate proliferation of glandular tissue of
fallopian tubes.

Also increase activity of the cilia which helps propel the ovum.

Estrogen stimulates growth of stromal tissue, ductile
system and fat deposition in breast.

Stimulate slight increase the breast lobules and alveoli.

Responsible for growth and external appearance of
female breast and milk-producing apparatus.

Question 21

Progesterone Effect on the Uterus

Answer 21

Progesterone promote secretory changes in the uterine endometrium during the latter half of the monthly female sexual cycle.

Preparing the uterus for implantation of the fertilized
ovum.

Progesterone decreases the frequency and intensity of uterine contractions, thereby helping to prevent
expulsion of the implanted ovum.

Question 22

Progesterone effect on the Fallopian

Tubes

Answer 22

Promotes increased secretion by the mucosal lining of
the fallopian tubes.

These secretions are necessary for nutrition of the
fertilized ovum

Question 23

Progesterone effect on the Breasts

Answer 23

Like Estrogen, progesterone promotes development of the lobules and alveoli of the breasts, causing the
alveolar cells to proliferate, enlarge, and become
secretory.

Progesterone also causes the breasts to swell.

Question 24

Monthly Endometrial Cycle and Menstruation

Answer 24

The endometrial cycle in the lining of the uterus operates through the following stages:

1. Proliferation of the uterine endometrium;
2. Development of secretory changes in the endometrium
3. Menstruation.

Question 25

Proliferative Phase (Estrogen Phase)

Answer 25

At the beginning of each monthly cycle, most of the endometrium has been desquamated by menstruation. Estrogens, during the first part of the monthly ovarian cycle, causes the stromal cells and the epithelial cells to proliferate rapidly. Before ovulation occurs, the endometrium increases greatly in thickness, owing to increasing numbers of stromal cells and to progressive growth of the endometrial glands

Question 26

Secretory Phase (Progestational Phase)

Answer 26

After ovulation has occurred, progesterone and estrogen together are secreted in large quantities by the corpus luteum. Estrogens cause cellular proliferation in the endometrium during this phase Progesterone causes marked swelling and secretory development of the endometrium. The purpose of endometrial changes is to produce a highly secretory endometrium that contains large amounts of stored nutrients to provide appropriate conditions for implantation of a fertilized ovum during the latter half of the monthly cycle.

Question 27

Menstruation

Answer 27

 If the ovum is not fertilized, menstruation follows  Menstruation is caused by the reduction of estrogens and progesterone, especially progesterone, at the end of the monthly ovarian cycle.  The first effect is decreased stimulation of the endometrial cells by these two hormones, followed rapidly by involution of the endometrium to about 65% of its previous thickness.  Vasoconstriction, decrease in nutrients to the endometrium, and the loss of hormonal stimulation initiate necrosis in the endometrium, especially of the blood vessels.  Desquamated tissue and blood in the uterine cavity, plus contractile effects of prostaglandins initiate uterine contractions that expel the uterine contents.  Approximately 40 milliliters of blood and an additional 35 milliliters of serous fluid are lost

Question 28

Negative Feedback Effects of Estrogen and Progesterone to Decrease LH and FSH Secretion

Answer 28

 Estrogen has a strong inhibitory effect on production of LH and FSH. Also, when progesterone is available, the inhibitory effect of estrogen is multiplied, even though progesterone by itself has little effect  These feedback effects seem to operate mainly on the anterior pituitary gland directly, but they also operate to a lesser extent on the hypothalamus to decrease secretion of GnRH, especially by altering the frequency of the GnRH pulses.

Question 29

Puberty and Menarche

Answer 29

 Puberty means the onset of adult sexual life.  Menarche means the beginning of the cycle of menstruation.  The period during which the sexual cycle ceases and the female sex hormones diminish to almost none is called menopause.  Puberty is caused by a gradual increase in gonadotropic hormone secretion by the pituitary, beginning at about 8 years old and usually culminating in the onset of puberty and menstruation between ages 10 and 14 years in girls (average, 12 years).

Question 30

Menopause

Answer 30

 The cause of menopause is “burning out” of the ovaries.  The production of estrogens by the ovaries decreases as the number of primordial follicles approaches zero.  The loss of estrogens often causes marked physiological changes in the function of the body, including (1) “hot flushes” characterized by extreme flushing of the skin, (2) psychic sensations of dyspnea, (3) irritability, (4) fatigue, (5) anxiety, and (6) decreased strength and calcification of bones throughout the body.  Administration of estrogen after menopause may increase the risk for cardiovascular disease.

Question 31

Female Sexual Act | Stimulation of the Female Sexual Act

Answer 31

 Successful performance of the female sexual act depends on both psychic stimulation and local sexual stimulation.  Sexual thoughts can lead to female sexual desire  Such desire is based on psychological and physiological drive, although sexual desire does increase in proportion to the level of sex hormones secreted.  Desire also changes during the monthly sexual cycle, reaching a peak near the time of ovulation, probably because of the high levels of estrogen secretion during the preovulatory period. Stimulation of the Female Sexual Act  Massage and other types of stimulation of the vulva, vagina, and other perineal regions can create sexual sensations.  The glans of the clitoris is especially sensitive for initiating sexual sensations.  The sexual sensory signals are transmitted to the sacral segments of the spinal cord through the pudendal nerve and sacral plexus.  Once these signals have entered the spinal cord, they are transmitted to the cerebrum.

Question 32

Female Erection Female Orgasm  The female orgasm is analogous to emission and ejaculation in the male, and it may help promote fertilization of the ovum.  During the orgasm, the perineal muscles of the female contract rhythmically, which results from spinal cord reflexes similar to those that cause ejaculation in the male.  It is possible that these reflexes increase uterine and fallopian tube motility during the orgasm, thus helping to transport the sperm upward through the uterus toward the ovum.  The orgasm seems to cause dilation of the cervical canal for up to 30 minutes, thus allowing easy transport of the sperm. Female Orgasm continues…  Copulation causes the posterior pituitary gland to secrete oxytocin  The oxytocin causes increased rhythmic contractions of the uterus, which may increase transport of the sperm.  The intense sexual sensations that develop during the orgasm also pass to the cerebrum and cause intense muscle tension throughout the body.  After culmination of the sexual act, this tension gives way during the succeeding minutes to a sense of satisfaction characterized by relaxed peacefulness, an effect called resolution.

Answer 32

 Extending into the clitoris is erectile tissue almost identical to the erectile tissue of the penis.  Erectile tissue is controlled by the parasympathetic nerves from the sacral plexus to the external genitalia.  Parasympathetic signals dilate the arteries of the erectile tissue, probably resulting from release of acetylcholine, nitric oxide, and vasoactive intestinal polypeptide at the nerve endings.

Question 33

Female Lubrication

Answer 33

 Parasympathetic signals also pass to the bilateral Bartholin glands located beneath the labia minora and cause them to secrete mucus immediately inside the introitus.  This mucus is responsible for much of the lubrication during sexual intercourse, although much lubrication is also provided by mucus secreted by the vaginal epithelium, and a small amount is provided from the male urethral glands.  This lubrication is necessary during intercourse to establish a satisfactory massaging sensation rather than an irritative sensation, which may be provoked by a dry vagina.

Question 34

Female Orgasm

Answer 34

 The female orgasm is analogous to emission and ejaculation in the male, and it may help promote fertilization of the ovum.  During the orgasm, the perineal muscles of the female contract rhythmically, which results from spinal cord reflexes similar to those that cause ejaculation in the male.  It is possible that these reflexes increase uterine and fallopian tube motility during the orgasm, thus helping to transport the sperm upward through the uterus toward the ovum.  The orgasm seems to cause dilation of the cervical canal for up to 30 minutes, thus allowing easy transport of the sperm.  Copulation causes the posterior pituitary gland to secrete oxytocin  The oxytocin causes increased rhythmic contractions of the uterus, which may increase transport of the sperm.  The intense sexual sensations that develop during the orgasm also pass to the cerebrum and cause intense muscle tension throughout the body.  After culmination of the sexual act, this tension gives way during the succeeding minutes to a sense of satisfaction characterized by relaxed peacefulness, an effect called resolution.