Grayce P. Storey
Life consists of a series of changes. During the constant changes in life the body undergoes many cycles. One such cycle is the menstrual cycle which commences at puberty and continues through the child bearing years or menopause.
The commencing of the menstrual cycle is one sign of maturity, of becoming a woman. Month after month this cycle is repeated and is normally interrupted by pregnancy. After the birth of the baby the cycle resumes.
In order for the menstrual cycle to commence certain organs and glands become involved or start functioning.
The onset of menstruation is called menarche. There are a variety of intervals between periods. It is thought that the 28 day cycle may be a myth because few woman have a perfectly regular cycle. The interval between periods may change many times during a woman’s life. There are many circumstances that may affect the menstrual cycle, such as: illness, abrupt change of climate, or severe emotional stress. “The cycle is particularly irregular during the early years and again at menopause.”
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Some women may experience premenstrual tension. These symptoms may occur 10-14 days prior to the onset of the menstrual period. These symptoms may include “headache, bloating of the abdomen, fullness and pain of the breasts, increased irritability, depression, and emotional instability. The symptoms usually disappear hours after the menstrual flow starts.”
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The pituitary gland produces and stimulate the growth hormones. It is through the blood that this information is carried to the bones and tissue. This gland is about the size of a pea at menarche and is located at the base of the brain, (see diagram 5.) This gland is also called the master gland, the chief gland, or the control gland. It is the pituitary gland that notifies the gonads that it is time to start functioning. The pituitary sends a follicle stimulating hormone to stimulate the growth and development of follicles in the ovaries. The ovaries secrete estrogen which aid in the maturation of the follicle.
The ovaries are two glands containing thousands of follicles or egg sacs on either side of the uterus. Once a month ovulation occurs. In one of the 2 ovaries an egg or ovum matures and breaks out of its sac or graafian follicle and out of the ovaries. Luteotropic hormone (LTH) secrete progesterone which aid in follicle growth and maturation.
The two fallopian tubes, with fringed open ends near the ovaries, are less than 5 inches long, (see diagram 3). These tubes provide passageway to the uterus. It is also through these tubes that the egg travels enroute to the uterus after ovulation. The uterus or womb is a hollow organ. The lining is called the endometrium, from which the menstrual flow comes, (see figure 1). Every month the lining of the uterus (endometrium) builds up into a spongy mass of tissue containing blood to form a bed for the fertilized egg. If the egg is unfertilized it will disintegrate and will shed.
The vagina or birth canal is the passageway from the uterus to the outside of the body, (see diagram 1). It is through this channel that the menstrual flow leaves the body by way of the cervix.
The menstrual cycle is divided into four phases: 1. the menstrual phase - the actual shedding of the endometrium, 2. post menstrual phase - this is resting stage immediately following menstruation. During this time, the pituitary sends out hormones to the ovum and another egg begins to ripen, 3. intermenstrual phase the ovaries releases a hormone which stimulates the endometrium and causes it to thicken. Ovulation occurs (a mature egg breaks out of the graafian follicle) the mature egg enters the fallopian tube, and the endometrium provides a nesting place for its development, and 4. premenstrual phase - the lining of the uterus continues to grow and thicken in preparation for the fertilized egg. If the egg is not fertilized the corpus luteum stops producing progesterone and the egg disintegrates. The lining is shedded and a new cycle commences. If fertilization and implantation does take place the corpus luteum continues secreting progesterone and menstruation does not occur.
The proliferative phase includes the postmenstrual phase and the intermenstrual phase. It is during this phase that the hormone estrogen which is produced by the ovaries prepares the uterus and the walls begin to thicken.
The secretory phase which is the premenstrual phase. It is during this phase that ovulation occurs and the portion that remains in the ovary is called the corpus luteum. The corpus luteum secretes progesterone which prepares the lining of the uterus to receive and nurture the fertilized egg.
During the normal menstrual flow, the individual discards 1-1/2 to 5 ounces of blood over the several days. This loss of blood is quickly replaced and does not cause weakening.
The female organs of reproduction include the ovaries, fallopian tubes, the uterus, the vagina, and the external genitalia, (see diagram 3). The ovaries and glands are located in the pelvis. The FSH, LH and estradiol are essential for the complete development of the mature ovum, which involves both follicular and oocyte maturation.
Progesterone is a hormone of pregnancy. This hormone stimulates the fallopian tubes and uterus in glandular secretions. Progesterone suppresses muscular contractions of the fallopian tubes and uterus which is critical to the maintenance of the pregnancy. Progesterone maintains the structure of the spiral arteries that provide blood to the secretory endometrium of the uterus. Progesterone acts on the cervix to greatly increase the viscosity of the cervical mucus.
The ovaries produce ova and the sex hormones, progesterone and estrogen. One is located on each side of the pelvis, lateral to the uterus. Each ovary is attached to the side of the uterus by a short ovarian ligament.
Out of the 2 million primary oocytes at birth, during sexual life only about 400 of these follicles become mature and the rest regress in size throughout life. At menopause, only scars remain.
The fallopian tubes, sometimes called the uterine tubes, or oviduct are bilateral muscular ducts. These ducts mucosa contain ciliated epithelium, which are little hair-like bodies. They are about 4 inches long. The dilated end near the ovaries has a number of fingerlike processes called fimbriae.
The function of the oviduct is a passageway to convey the ova from the ovaries to the uterus. It is in these tubes that fertilization takes place, (see diagram 3).
The uterus is a hallow, thick walled, pear shaped, muscular organ. The uterus is located in the pelvic area between the rectum and the bladder. The three parts of the uterus includes (1) the body, which expands over the oviduct; (2) the isthmus, or middle, slightly constricted portion; (3) the cervix, the lower part that surrounds the cervical canal.
The uterus is the organ in which the embryo grows and develops until the time of partrician.
The vagina is a fibromuscular tube which is anterior to the rectum and anal canal and posterior to the bladder and urethra. It is the organ of copulation and during parturition it serves as the exit from the uterus.
The lining of the vagina secretes an acid fluid that serves as a cleanser and lubricant.
The external female genitalia are often grouped together under the vulva, which include the moms pubis, the labia majora, the labia minora, the clitoris, the vestibular of the vagina and the greater vestibular glands.
The moms pubis, is a fatty pad of tissue located on the pubic bone above the genital organs. After puberty it is covered with hair and has the shape of an inverted triangle. The labia majora, is the external folds of skin that protects the vagina. It conceals most of the external reproductive organs. This organ is homologues to the scrotum in the male. Located in the labia majora are large sebaceous glands that become pigmented after puberty. (see diagram 2)
The labia minora, are two longitudinal folds that borders the vagina.
The clitoris is located at the apex of the triangular area, it is homologues to the penis in the male. This organ contains erectile tissue and becomes firm and filled with blood when stimulated.
The vestibule of the vagina is situated posterior to the clitoris. The urethra opens into the area anteriorly and the vagina opens posteriorly.
The bartholin’s glands function is to moisten. These glands open on either side of the vaginal orifice.