Physiology of reproductive system



Physiology of reproductive system:

The female reproductive cycle is a complex process that encompasses a series of chemical secretions and reactions to produce fertility and birth.

The female reproductive cycle is a general term encompassing:

The ovarian cycle:

The ovarian cycle is the series of events associated with a developing oocyte (ovum or egg) within the ovaries. While men manufacture daily, woman are born with a single lifetime supply of ova that are released form the ovaries gradually throughout the childbearing years. In the female ovary 2 million oocytes are present at birth, and about 400,000 follicles are still present at puberty. The ovarian cycle begins when the follicular cells well and the maturation process starts. The ovary raises many follicles monthly, but usually only one follicle matures to reach ovulation. The ovarian cycle consists of three phases

1. Follicular phase: this phase is when the follicles in the ovary grow and form a mature egg. It starts on day 1 of the menstrual cycle and continues until ovulation, approximately 10 to 14 days. The hypothalamus is the initiator of this phase. Increasing levels of estrogen secreted from the maturing follicular cells and the continued growth of the dominant follicle cell induce proliferation of the endometrium and myometrium.

This thickening of the uterine lining supports an implanted ovum if pregnancy occurs. Prompted by hypothalamus, the pituitary gland releases follicle-stimulating hormone(FSH) which stimulates the ovary to produce 5 to 20 immature follicles. Each follicle houses an immature oocyte or egg. A surge(flow) in luteinizing hormone(LH).

2. Ovulation: a mature follicle ruptures in response to a flow of LH releasing ovum, when ovulation occurs, there is a drop in estrogen. Typically ovulation takes place 10-12 hours after the LH peak and 24-36 hours after estrogen levels peak. The life span of the ovum is only about 24 hours; unless it meets a sperm on it's journey within that time, it will die.

During ovulation the cervix produces thin, clear, stretchy mucus that is design to help the sperm travel up to meet the ovum.

3. The Luteal phase: begins at ovulation and lasts until the menstruation phase of the next cycle. After the follicle ruptures as it releases the egg, it closes and form a corpus luteum. The corpus luteum secretes increasing amounts of the hormone progesterone, which interacts with the endometerium to prepare it for implementation. The progesterone secreted by the corpus luteum causes the temperature of the body to rise until the start of the next period. Temperature indicates the ovulation occurrence.

The endometrial Cycle:

The endometrial Cycle occurs in response to cyclic hormone changes

1. Proliferative Phase: starts with enlargement of the endometrial glands in response to increasing amount of estrogen. The blood vessels become dilated and the endometerium increases in thickness, it lasts from about day 5 of the menstrual cycle to the time of ovulation.

2. Secretory Phase: it follows ovulation to about 3 days before the next menstrual period under the influence of progesterone, endometrium becomes thickened and more vascular, these changes are all in preparation for implantation. Estrogen levels drop during this phase as progesterone dominates.

3. Menstrual Phase: it begins as the spiral arteries rupture secondary to ischemia, releasing blood into the uterus, and the endometrium is sloughed off. If fertilization dose not take place, the corpus luteum degenerates as a result both estrogen and progesterone levels fall and the thick ended endometrial lining sloughs away from the uterine wall and passes out via the vagina. The menstrual flow marks the end of one menstrual cycle and the start of a new one.

Menstrual Cycle Hormones:

1. Gonadotropin-Releasing Hormone (GnRH) is secreted form the hypothalamus in a pulsatile manner throughout reproductive cycle. GnRH induces the release of FSH and LH to assist with ovulation.

2. Follicle-Stimulating Hormone (FSH) secreted by the anterior pituitary gland and is primarily responsible for the maturation of the ovarian follicle. It is highest and most critical during the first week of the follicular phase of the reproductive cycle.

3. Luteinizing Hormone (LH) secreted by the anterior pituitary gland and is required for both the final maturation and luteinization of the ruptured follicle.

4. Estrogen is secreted by the ovaries and is crucial for the development and maturation of the follicle. It is predominant at the end of the follicular phase. After ovulation, estrogen levels drop sharply as progesterone dominates. Estrogen also causes the uterus to increase in size and weight because of increased glycogen, amino acids, electrolytes and water. Blood supply is expanded as well. Estrogen inhibits FSH production and stimulates LH production.

5. Progesterone is secreted by the corpus luteum. It's levels increase just before ovulation and peak 5 to 7 days after ovulation. During the luteal phase, progesterone induces swelling and increased secretion of the endomertrium. This hormone is called the hormone of pregnancy because of it’s calming effect(reduces uterine contractions) on the uterus, allowing pregnancy to be maintained.

6. Prostaglandins are a closely related group of oxygenated fatty acids that are produced by the endometrium with a variety of effects throughout the body.

Prostaglandins are not technically hormones because they are produced by all tissues rather than by special glands. Large amounts of Prostaglandins are found in menstrual blood.

sexual maturation:

starts with the brain, the hypothalamus transmits an enzyme to the anterior pituitary gland to begin production of Gonadotropic hormone, which activate the tests and ovaries and produce puberty.

Timing for puberty between 10-14 years of age, sexual maturation in girls occurs between 12-18, in boys 14-20

Changes in girls by age

Age (year)

9-11 Breasts elevation of papilla with breast bud formation

11-12 straight hair along the labia, vaginal epithelium becomes cornified, ph. Of vaginal secretions acid, slight mucous vaginal discharge present

12-13 pubic hair grows darker, breasts enlarge, axillary hair present, menarche occurs

Girls are taller than boys during puberty, others are the changes in the pelvic contour. They should be educated regarding their changes.

The age at which adolescents initiate sexual activity (the establishment of menstruation and ovulation in females and the development of soermatogesis in males)

If adolescents engage in sexual relations are emotionally unprepared, those need special care and regular visits to the health centers.

menstrual cycle:

It is an episodic uterine bleeding in response to cyclic hormonal changes.

It is bringing new life

Menarche: the first menstrual period in girls, the length of it accepted to be 28 days (from the beginning of one menstrual flow to the beginning of the next)

The length of the menstrual flow is 4 to 6 days although women may have periods as shorter as 2 days or long as 7 days.

4 body structures are involved in the physiology of the menstrual cycle

1. hypothalamus

menstrual cycle initiates from the releasing of the (GnRH) from the hypothalamus to pituitary gland to begin production of FSH & LH

2. Pituitary gland

Production of FSH & LH. Responsible for the maturation of the ovulation

3. Ovary

The ovum will grow and mature in the ovary's primordial follicles, produce a fluid contains a high content of estrogen

4. Uterus

After menstrual flow, the endometrium of the uterus becomes thin, then the production of progesterone and estrogen decreases, the endometrium of the uterus begins to generate.

Then menses occur as blood from the ruptured capillaries, fragments of the endometrial tissue and the unfertilized ovum.

Infertility:

or the inability to conceive a child or sustain a pregnancy to child birth This condition associates with high anxiety from the couple. The society has a great effect on the concept of infertility

The parents need education for that

Infertility divided in to primary and secondary.

Primary: there have been no previous conceptions

Secondary: there has been a previous viable pregnancy but the couple is unable to conceive at present.

Sterility:

Is the inability to conceive because of a known condition.

The chance of infertility increase with age, after the thirties pregnancy, too young mothers, women using oral, injectable, or implanted hormones. Other male factors are disturbances in the production of sperm cells, obstruction in seminiferous tubes and ducts, problems of sperm mobility and problems of ejaculation

Menopause:

Is the cessation of menstrual cycle. Indicates the time of life after changes are occurring ranging between 40-55 years.

If menarche occurred early in a mother it will probably occur early in her daughter, same time as the menopause the earlier the age of menarche the earlier menopause tends to occur, it makes their end of their ability to bear children, falling of estrogen will occur, osteoporosis & others.

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