CHAPTER 1 PHYSIOLOGY OF FEMALE REPRODUCTIVE SYSTEM
SECTION 1:THE PHYSIOLOGICAL CHARACTERISTICS OF FEMALE IN DIFFERENT STAGES
According to the age and reproductive endocrine changes in women's life, the physiology of women can be divided into 7 stages: fetal period, neonatal period, childhood, puberty or adolescence, sexual maturity, menopausal transition period, postmenopausal period.
1. Fetal Period
Fertilized eggs are composed of paternally and maternally derived 23 pairs （46）chromosome which becomes a new individual. XX zygote for females XY for males. Gonadal differentiation is slow. Around 8-10 weeks the gonadal tissue changes to ovarian structure. After the formation of ovarian androgen, Mullerian development leads to female genital tract formation.
That growth and development do not begin at the time of birth is quite obvious. For the pediatrician, birth marks the onset of growth and development from a clinical standpoint. To provide a clear understanding of these phenomena after birth, the changes that occur before birth and continue to take place in the postnatal period are reviewed here.
Life as a new individual commences at the moment of fertilization. Growth becomes an inherent force in that individual and continues, in stature at least, until the average age of about 20 years unless disease, accident, or death interferes. During this time, there are also marked changes in differentiation or maturation of specific organs as well as in the body as a whole.
The increase in weight is even more surprising. From birth to maturity the weight is increased 20-fold. From the time of fertilization to birth the increase in weight is approximately 6 billion times.
Fetal Behavior:
1.1 Fetus at 8 weeks
The major components of both trunk and limb musculature are evident in the embryo at the end of the second fetal month. The nerves as yet have no anatomical or physiologic connections with either smooth or striated muscle. During this time, the embryo floats quiescently in the amniotic fluid. However, movement has already taken place in this new in-dividual. Since 4 weeks of age the heart has been beating at a fairly regular rate.
1.2 Fetus at 12 to 14 weeks
With increasing age and maturation of the neuromuscular system the movements spread caudally and become more pronounced in the lower trunk. Then discrete reflexes appear, accompanying spread of the skin areas sensitive to stimulation.By 14 weeks, the human fetus has largely ceased to exhibit the earlier, more generalized responses and activity becomes less stereotyped.
1.3 Fetus at 28 weeks
The fetal age at 28 weeks approximately demarcates the zone between viability and non viability. The following out-lines of behavior are based on the observations of Gesell in premature infants from fetal ages of 28 to 40 weeks.
1.4 Fetus at 28 to 32 weeks
（1）Movements are meager, fleeting, poorly sustained.
（2）Lack of muscular tone.
（3）Mild avoidance response to bright light and sound.
（4）In prone position turns head to side.
（5）Palmar stimulation elicits a barely perceptible grasp.
（6）Breathing is shallow and irregular.
（7）Inconstant tonic neck reflex.
1.5 Fetus at 32 to 36 weeks
（1）Movements are sustained and positive.
（2）Muscle tone fair under stimulation.
（3）In prone position turns head, elevates rump.
（4）Fairly well-established tonic neck reflex.
1.6 Fetus at 36 to 40 weeks
（1）Movements active and sustained.
（2）Muscle tone well.
（3）In prone position attempts to lift head.
（4）Cries well when hungry and disturbed.
2. Neonatal Period
Within 4 weeks after birth.
（1）Few babies demonstrate lactation. （2）A few also have a small amount of vaginal bleeding. （3）Physiological jaundice.
3. Childhood
During the period of: From the 4 week after birth to the age of 12, known as childhood.
Characteristic: Physical growth is faster. Reproductive system growth is slower.. Introduction of children to language and comprehension activity very early in life is necessary for the development of cognitive abilities and communication skills. A variety of age-appropriate toys and activities are preferable because they will provide opportunity for diverse stimulation and enhance cognitive development in many ways. Activities and toys are classified as education has progressed and are designed to stimulate the development of specific cognitive and motor abilities.
4. Puberty or Adolescence
After birth, the gonads are quiescent until they are activated by gonadotropins from the pituitary to bring the final maturation of the reproductive system.
This period of the final maturation is known as adolescence. It is often called puberty, although strictly defined, puberty is the period when the endocrine and gametogenic functions of the gonads first develop to the point where reproduction is possible. In girls, the first event is thelarche, the de velopment of breasts, followed by pubarche, the development of axillary and pubic hair, and then menarche, the first menstrual period. The initial periods are generally anovulatory, and regular ovulation begins about 1 year later.
The age at the time of puberty is variable. In the U.S., in recent years, puberty has generally been occurring between the ages of 8 and 13 in girls. Another event that occurs in humans at the time of puberty is an increase is called adrenarche. It occurs at age 8-10 years in girls. The adrenal androgens contribute significantly to the growth of axillary and pubic hair. The breasts develop under the influence of the ovarian hormones estradiol and progesterone, with estradiol primarily responsible for the growth of ducts and progesterone primarily responsible for the growth of lobules and alveoli.
Characteristic:
（1）First sexual characteristics: Reproductive organs from infantile to adult type.
（2）Secondary sexual characteristics: Includes a high pitch voice, breast fullness and uplift, the armpit and pubic hair, the pelvic development, chest, shoulders, hips, subcutaneous fat increased, forming a characteristic of the female body.
（3）Growth spurt.
（4）Menarche: this is an important symbol of puberty, menstrual cycle is often irregular. After the irregular cycles about 2-3 with ovulation, menstruation gradually becomes normal.
5. Sexual maturity
This period is also called the reproductive period; This is the most productive period of ovarian reproductive function and endocrine function, generally from the age of 18, which lasted about 30 years.
Characteristic:
（1）Periodic ovulation has been established.
（2）Reproductive organs and breast under the effect of ovarian secretion of hormones change periodically.
6. Menopausal transition period
Menopause is one of the hottest women's health topics as the baby boomer generation comes of age. An unprecedented number of American women, about 1.25 million annually, are experiencing menopause. This generation of women has grown up believing that informed decisions are based on adequate information. They want answers to questions that previously have not been asked. They want to know what to expect physiologically and psychologically as they go through this next life transition.
This generation has removed the shroud of secrecy around a number of health topics, from breast cancer to menopause. Menopause, physiologically speaking, is the time when ovulation and menstruation cease but, more commonly, is referred to as the period from perimenopause to postmenopause. Menopause can also be viewed positively as the life stage when women have more time to be creative and autonomous, to evaluate prior life choices, and to plan for future choices.
Refers to the time in the females' life when ovarian function begins to decline until the last period of the menstrual period. Generally begins after 40 years of age. Usually it lasts 1 or 2 years, rarely to longer than 10 years. Last menstrual period in women's life is called postmenopausal. The World Health Organization （WHO）defined the time when ovarian function declines until 1 year after the menopause period is called the menopausal transition.
Chinese women's menopause age is on an average of 50 or so. Starting from the ovarian function decline until meno-pause, the period known as the menopausal transition
Characteristic:
（1）No ovulation “menstruation”.
（2）Lower levels of estrogen. These lead to vasomotor disorders and mental neurological symptoms. In the body, under the regulation of autonomic nervous system compensation occurs. Hence most women have no obvious symptoms. However, some women manifest with hot flashes, sweating, insomnia, depression, or irritability, etc.
7. Postmenopausal period
During the period of: Refers to the post menopausal period of life. After 60 years of age, the body gradually aging into senility period.
Characteristic:
（1）The body's aging change, reproductive organs further atrophy. They are prone to atrophic vaginitis.
（2）Bone metabolism disorders cause osteoporosis. The women are prone for fractures.
（李志英）