Physiology
(10) 19/4/2018
Abdallah Riyalat & Abd AL-Rahman Salman
Female reproductive system All the ideas in slides are included & I think the sheet is enough but the exact text of them is not included. Some
information are from the book or from the internet. I hope I will cover all information & sorry for any mistake. Let’s
take a deep breath and start.
This lecture is talking about physiology of female reproductive system. Physiologically, Female reproductive
functions can be divided into two major phases:
1) Preparation of the female body for conception and pregnancy
2) The period of pregnancy itself.
We will cover part of the first phase.
First of all we have to remember briefly the anatomy of female reproductive system which is consist of ovaries,
fallopian tubes (also called uterine tubes), uterus, and vagina
also you have to know the internal structures which I will not talk about
them. You can review them from anatomy lecture.
In the intrauterine life the number of germ cells that are going to form the
ovum (a process called oogenesis**) are about 7 million cells (primordial
follicles).
By the time during fetal life, this number decreases gradually because
many of these cells die continuously (in a process called atresia).
At birth this number will be only 1-2 million cells.
From birth until puberty, some cells again will be atretic and they will
reach 400-500 thousand cells only (primary follicles). This number
represents the number of germ cells that are able to form mature ovum
during female life.
In the whole female life only 400-500 mature ovum is going to be
produced so out of the germ cells found at puberty many of them will die
again.
**Oogenesis: A developing egg (Oocyte) becomes Mature egg (Ovum)
through series of steps.
The Fundamental reproductive unit of the female is the single ovarian follicle.
It is composed of one germ cell (oocyte), surrounded by endocrine cells. These endocrine cells differ from one
stage to another. We will take about these stages of the follicle later but mainly these cells are granulosa cells &
theca cells.
Stages of oogenesis:
*All oocytes formed in females are produced during
fetal life. They degenerate with time and at birth the
ovaries contain about 2 million oocytes.
*All the oocytes go into meiotic arrest when they
reach the first meiotic division during fetal life.
*The primary oocytes remain in the prophase of the
first meiotic division until the time of puberty, when
they are gradually released to complete meiosis at
regular intervals known as the ovarian cycle.
*On the average only one oocyte matures during
each cycle, which occurs at monthly intervals, so that
the total amount of oocytes to be ovulated is about
500 oocytes in a lifetime.
*note: oogonia is a small diploid cell which on
maturation forms a primordial follicle in a female fetus
*when a female form a mature ovum there are 2
possibilities: either it will be fertilized by a sperm or if
the sperm is not present the body will get rid of it by
menstrual cycle.
*6-12 ovum per month will be produced but only one
of them will become mature (on the other hand in
male all germ cells will form mature sperms)
Female hormonal system: consists of three hormones:
1) Hypothalamic releasing hormone, gonadotropin releasing hormone GnRH
2) Anterior pituitary sex hormones, FSH and LH secreted in response to the release of GnRH from the
hypothalamus
3) Ovarian hormones, estrogen and progesterone secreted in response to pituitary hormones
*These hormones secreted at different rate during different parts of the female monthly sexual cycle. The
duration of the cycle averages 28 days. It may be as short as 20 days or as long as 45 days in some women.
* The ovarian changes that occur during the sexual cycle depend completely on secretion of FSH & LH.
*During childhood this cycle is not present because the hypothalamus does not secret GnRH for an unknown
reason
* At age 9 to 12 years secretion of these hormones leads to onset of normal monthly sexual cycles beginning
between the ages of 11 and 15 years (puberty).
*during first half of the cycle estrogen & progesterone are present but the progesterone with less amounts. On
the other hand in the second half the amount of progesterone is more than estrogen
*the amount of FSH will be more than LH except at the time of ovulation.
*in the middle (day 14) it is the time of ovulation where we have a significant increase in LH
*no LH no ovulation
*Estrogen and progesterone act as a negative feedback for the secretion of FSH & LH during most of the cycle
but at day 12-14 (at the time of ovulation) they act as a positive feedback causing increase the secretion of FSH
& LH during this period
Differences between spermatogenesis and oogenesis:
1. In females, mitotic proliferation of oogonia occurs prior to birth. In males, spermatogonia proliferate only after
puberty.
2. in females, meiotic divisions of oocyte produces only one mature ovum. In males, meiotic divisions of primary
spermatocyte produces 4 mature spermatozoa
3. In females, second meiotic division is completed only upon fertilization. In males, the products of meiosis
(spermatids) undergo substantial differentiation in the maturing process.
Ovarian cycle is a series of monthly repetitive physiological and developmental changes in the ovaries, which
prepare the ovaries for ovulation and subsequent development of a Corpus Luteum whose hormones will assist
in regulating the uterine cycle and, if the implantation of a developing embryo occurs, assist in regulating the
pregnancy.
It is regulated by FSH and LH
The changes that occur in the ovary during each cycle can be divided into three phases:
1) Follicular phase (day 1-13)
2) Ovulatory phase (day 13-15)
3) The luteal phase (day 15-28).
These phases run in parallel with the phases of the uterine cycle and together comprise the menstrual cycle.
Before the explanation of these phases, here is a general idea about what happens. Under the presence of
estrogen in the follicular phase, discharge of blood (menses) stop & the lining of the uterus become thick, Follicle
in the ovary begin to develop under the influence of many hormones. After that the mature ovum/follicle that is
produced during the follicular phase release oocyte (ovulation) while the remaining of the follicle in the ovary
called corpus luteum. Then the oocyte can live 24 hours or less without fertilization. Corpus luteum secret
progesterone that make a change in the uterus to prepare it for pregnancy if implantation doesn’t occur in
about 2 weeks the luteum degenerate and cause a drop in the level of estrogen and progesterone the uterus
shed itself (lining) by a process called menstruation
Ovarian Follicle Growth:
When a female child is born, each ovum is surrounded by a single layer of granulosa cells; and now it is called a
primordial follicle. This follicle is suspended as we said at prophase of meiosis 1. After puberty, when FSH and
LH begin to be secreted the follicles begin to grow
1- Enlargement of the ovum
2- Growth of additional layers of granulosa cells
These follicles are known as primary follicles.
*Function of granulosa cells:
1- Nourishment to the ovum
2- Secrete oocyte maturation inhibition factor that keep the ovum in suspended in its primordial state in the
prophase stage of meiotic division.
Antral and Vesicular Follicles:
Spindle cells derived from the ovary interstitium collect in several layers outside the granulosa cells, giving rise to
a second mass of cells called the theca.
1- Theca interna secrete estrogen and progesterone
2-Theca externa form vascular connective tissue capsule of the developing follicle
After that, the mass of granulosa cells secretes a follicular fluid that contains a high concentration of estrogen
causes an antrum to appear within the mass of granulosa cells as the figure below
*Until now, all growth stages from the primordial to antral follicle are caused by FSH alone.
After that greatly accelerated growth occurs and leads to larger follicles called vesicular follicles.
This accelerated growth is caused by:
1- Estrogen makes granulosa cells more sensitive to FSH
2- FSH and the estrogens promote LH receptors on the original granulosa cells
3- Estrogens & LH cause proliferation of the follicular thecal cells and increase their secretion
And now only one follicle fully matures each month, and the remainder undergo Atresia. But why??
The large amounts of estrogen from the most rapidly growing follicle act on the hypothalamus to depress further
enhancement of FSH secretionblocking further growth of the less well developed follicles
* The single follicle reaches a diameter of 1 to 1.5 centimeters at the time of ovulation and is called the mature
follicle.
*menarche: the first menstrual
period occur after the onset of
puberty
Ovulation:
Occurs 14 days after the onset of menstruation. The follicle ruptures at a point called stigma→ releasing the
secondary oocyte and corona radiata (granulosa cells surround the oocyte) into the peritoneal cavity to be taken
up by the oviduct.
The zona granulosa and thecal cells remain in the ovary. Granulosa and Theca interna cells change into lutein
cells and growth to form corpus luteum.
Now 1-Granulosa cells form progesterone and estrogen
2-Theca cells form androgen androstenedione and testosterone which are change by aromatase enzyme in the
granulosa cells to estrogen
Discharge of the ovum occur (with part of the cumulus) of the mature Graafian follicle from the surface of ovary at
the middle of the cycle (14+2 days before the subsequent menstruation).
Surge of LH Is Necessary for Ovulation. LH is necessary for final follicular growth and ovulation. Without this
hormone, even when large quantities of FSH are available, the follicle will not progress to the stage of ovulation.
The LH also has a specific effect on the granulosa and theca cells, converting them mainly to progesterone-
secreting cells more progesterone & decreased estrogen
After secretion of progesterone:
1- The theca externa begins to release proteolytic enzymes dissolution of the follicular wall swelling of the
entire follicle and degeneration of the stigma
2- Rapid growth of new blood vessels into the follicle wall with increase of prostaglandins by prostaglandin
endoperoxide synthase plasma transudation into the follicle (pseudo-inflammatory response) swelling of the
follicle follicle rupture
*This Process facilitated by intrafollicular pressure and contraction of smooth muscle in theca
* FSH (some LH) play a role by stimulating the release of plasminogen activator from granulosa cells (converts
plasminogen to plasmin)
Luteal phase:
within the next 2-3 days after expulsion of the ovum from the follicle, the remaining granulosa and theca interna
cells change rapidly into lutein cells (dependent mainly on LH). They enlarge in diameter and become filled with
lipid inclusions that give them a yellowish appearance (الجسم االصفر)
Corpus luteum is formed by:
1- The zona granulosa →granulosa lutein
2- Theca cells → theca lutein cells & some capillaries & c.t.
Both of these cells become cuboidal with central nucleus
The corpus luteum normally grows to about 1.5 centimeters in diameter, reaching this stage of development 7 to
8 days after ovulation then it begins to involute & loses its secretory function and its yellowish, lipid characteristic
about 12 days after ovulation (it’s now called corpus albicans)
A local hormone called luteinization-inhibiting factor, seems to hold the luteinization process in check until after
ovulation.
The corpus luteum secrete large amounts of both progesterone and estrogen. So if the pregnancy occur, it will
promote required progesterone until formation of the placenta
Corpus luteum life span:
-In the absence of fertilization, 14 days →apoptosis → Corpus albicans
- If pregnancy occur, chorionic gonadotropin which is secreted by the placenta, can act on the corpus luteum to
prolong its life usually maintaining it for at least the first 2 to 4 months of pregnancy. It has LH like action causing
further growth of CL and increases its hormonal production.
CL is important in the beginning of pregnancy because it support the early embryo until placenta takes over the
function of Estrogen & Progesterone production
Involution of the Corpus Luteum and Onset of the Next Ovarian Cycle:
1- Estrogen and progesterone inhibit the secretion of FSH & LH cause degeneration of CL
2- Lutein cells secrete small amount of inhibin hormone which inhibit FSH secretion cause degeneration of CL
Final involution normally occurs at the end of almost exactly 12 days of corpus luteum life (day 26). At this time
there is decrease in estrogen, progesterone & inhibin no further feedback inhibition for FSH secretion
growth of new follicles
Summary
About every 28 days, gonadotropic hormones from the anterior pituitary gland cause about 8 to 12 new follicles
to begin to grow in the ovaries. One of these follicles finally becomes “mature” and ovulates on the 14th day of
the cycle. During growth of the follicles, mainly estrogen is secreted. After ovulation, the secretory cells of the
ovulating follicle develop into a corpus luteum that secretes large quantities of both the major female hormones,
progesterone and estrogen. After another 2 weeks, the corpus luteum degenerates, whereupon the ovarian
hormones estrogen and progesterone decrease greatly and menstruation begins. A new ovarian cycle then
follows
We talked about negative & positive feedback but this is a combination of these information:
Positive feedback:
Sex hormones (Estrogen) ↑ → GnRH or LH/FSH↑ -- Estrogen peak (≥200pg/ml) → LH/FSH peak → during
ovulation only.
Negative feedback:
Sex hormones (Estrogen)↑ → GnRH or LH/FSH↓
*Follicular phase: Estrogen↑ → FSH↓
*Luteal phase: Estrogen & Progesterone↑ → LH/FSH↓ (formation of CL)
Estrogen & Progesterone↓ → LH/FSH↑ (regression of CL)
Indicators of ovulation:
1- Mid-abdominal pain (irritation of the peritoneum): follicles have some fluid inside them so when they rupture,
the fluid goes to peritoneal cavity causes some irritation & abdominal pain
2- Increase elasticity of cervical mucus
3- Cervical mucus dries in Arborizing form
4- Decrease Cornified cells in the vaginal mucosa
5- Increase Basal body temperature (increase 0.5 C)
6- Increase Urinary Estrogen, and pregnanediol or plasma progesterone level during luteal phase (day 21)
7- Absolute proof of ovulation is pregnancy
Menstrual phase: 4-7 days
Proliferative phase: growth of endometrium & the wall will significantly increase
Secretary phase: secretes after ovulation
FSH is mainly for the growing for the ovum
The lecture is DONE I hope you got benefit from this sheet and sorry for any mistake
“Woman” word consist of “wo” + “man”
What does “wo” mean??
It means World Origin
Greetings to All WOMEN…