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The vagina is a thin walled-tube, 8 to 10 cm long. It lies between the bladder & the rectum & extends from the cervix to the body exterior. The urethra is embedded in its anterior wall. Often called the birth canal, the vagina provides a passageway for delivery of an infant & for menstrual flow. Since it receives the penis (& semen) during sexual intercourse, it is The highly distensible wall of the vagina wall consists of three coats: A mucosa marked by transverse ridges or rule, which stimulate the The epithelium of the mucosa is a stratified squamous epithelium adapted to stand up to friction. Certain of the mucosal cells act as antigen-presenting cells & are thought the route of HIV transmission from an infected male to the female during intercourse.
The vaginal mucosa has no glands; it is lubricated by the cervical mucous glands. Its epithelial cells release large amounts of glycogen, which is anaerobically metabolized to lactic acid by resident bacteria. Consequently, the pH of a woman's vagina is normally quite acidic. This acidity helps keep the vagina healthy & free of infection, but it is also hostile to sperm. Although vaginal fluid of adult woman is acidic, it tends to be alkaline in adolescents, predisposing sexually active teenagers to sexually transmitted diseases. In virgins, the mucosa near the distal vaginal orifice forms an incomplete partition called the hymen.
The hymen is very vascular & tends to bleed when it is ruptured during the first coitus (sexual intercourse). However, its durability varies. In some females, it is ruptured during a sports activity, tampon insertion, or pelvic examination. Occasionally, it is so though that it must be breach surgically if intercourse is to occur.
The upper end of the vaginal canal loosely surrounds the cervix of the uterus, producing a vaginal recess called the vagina fornix. The posterior part of this recess, the posterior fornix, is much deeper than the lateral & anterior forces. Generally, the lumen of the vagina is quite small &, except where it is held open by the cervix, its posterior & anterior walls are in contact with one another. The vagina stretches considerably during copulation & childbirth, but its lateral distension by the ischial spines & the The uterus tilts away from the vagina. Hence, attempts by untrained persons to induce an abortion by entering the uterus with a surgical instrument may result in puncturing of the posterior wall of the vagina, followed by hemorrhage & - if the instrument is unsterile - subsequent The external genitalia, also called the vulva or pudendum, include the: Structures associated with the vestibule.
The mons pubis is a fatty, rounded area overlying the pubic symphysis. After puberty, this area is covered with pubic hair. Running posteriorly from the mons pubis are two elongated, hair-covered fatty skin folds, the labia majora. These are the female counterpart of the male scrotum. The labia majora enclose the labia minora, two thin, hair-free skin folds, homologous to the ventral penis.
The labia minora enclose a recess called the vestibule, which contains the external opening of the urethra more anteriorly followed by that of the vagina. Flanking the vaginal opening are pea-sized greater vestibular glands, homologous to the bulbourethral glands of the males. These glands release mucus into the vestibule & help to keep it moist & lubricated, facilitating intercourse. Just anterior to the vestibule is the clitoris, a small, protruding structure, composed largely of erectile tissue, that is homologous to the penis of the male. It is hooded by a skin fold called the prepuce of the clitoris, formed by the junction of the labia minora folds. The clitoris is richly innervated with sensory nerve endings sensitive to touch, & it becomes swollen with blood & erect during tactile stimulation, contributing to a female's sexual arousal.
The clitoris has dorsal erectile columns; but it lacks a corpus spongiosum. The female urinary & reproductive tracts are completely separate, & neither runs through the clitoris. The female perineum is a diamond-shaped region located between the pubic arch anteriorly, the coccyx posteriorly, & the ischial tuberosities laterally. The soft tissues of the perineum overlie the muscles of the pelvic outlet & the posterior ends of the labia majora overlie the central tendon, into which most muscles supporting the pelvic floor insert. The mammary glands are present in both sexes, but they normally function only in females. Since the biological role of the mammary glands is to produce milk to nourish a newborn baby, they are actually important when reproduction has already been accomplished.
Developmentally, the mammary glands are modified sweat glands that are really part of the skin, or integumentary system. Each mammary gland is contained within a rounded skin-covered breast anterior to the pectoral muscles of the thorax. Slightly below the center of each breast is a ring of pigmented skin, the areola, which surrounds a central protruding nipple. Large sebaceous glands in the areola make it slightly bumpy & produce sebum that reduces chapping & cracking of the skin of the nipple. Autonomic nervous system controls of smooth muscle fibers in the areola & nipple cause the nipple cause the nipple to become erect when stimulated by tactile or sexual stimuli & when exposed to the cold. Internally, each mammary gland consists of 15 to 25 lobes that radiate around & open at the nipple.
The lobes are padded & separated from each other by fibrous connective tissue & fat. The interocular connective tissue forms suspensory ligaments that attach the breast to the underlying muscle fascia to the overlying dermis. As suggested by their name, the suspensory ligaments provide natural support for the breast, like a built-in brassiere. Within the lobes are smaller units called lobules, which contain glandular alveoli that produce milk when a woman is lactating.
These compound alveolar glands pass the milk into the lactiferous ducts, which open to the outside at the nipple. Just deep to the areola, each lactiferous duct has a dilated region called a lactiferous sinus. Milk accumulates in In non-pregnant women, the glandular structure of the breast is largely undeveloped & the duct system is rudimentary; hence, breast size is largely due to the amount of fat deposits. Invasive breast cancer, the most common malignancy of US women, strikes about 180, 000 American women each year. One in eight women will develop this condition. Breast cancer usually arises from the epithelial cells of the ducts, not from the alveoli.
A small cluster of cancer cells grows into a lump in the breast from which cells eventually metastasize. Known risk factors for developing breast cancer include: Early onset menses & late menopause. No pregnancies or first pregnancy later in life. Family history of breast cancer (especially sister or mother). Other risk factors proposed but as yet unproved include: Exposure to high estrogen concentrations while in utero & Cigarette smoking & excessive alcohol intake. Some 10 % of breast cancers stem from hereditary defects & half of these can be traced to dangerous mutations in a pair of genes, dubbed BRCA 1 & BRCA 2, which virtually guarantee that the carriers will develop breast cancer.
However, more than 70 % of women who develop breast cancer have no known risk factors for the disease. Breast cancer is often signaled by a change texture, puckering, or leakage from the nipple. Early detection by breast self-examination & mammography is unquestionably the best way to increase one's chances of surviving breast cancer. Simple self-examinations should be health maintenance priority in every women's life. The American Cancer Society recommends scheduling mammography, X-ray examinations that detects breast cancers too small to feel, every two years for women between 40 to Once diagnosed, breast cancer is treated in various ways: Surgery, often followed by irradiation or chemotherapy, to destroy Radical mastectomy is the removal of the entire affected breast, plus all underlying muscles, fascia, & associated lymph nodes. Medical records reveal that this painful & disfiguring treatment is no more effective at halting the cancer than less extensive surgery.
Most physicians now recommend lumpectomy, in which only the cancerous part is excised, or a simple mastectomy, removal of the breast tissue only. Many mastectomy patients opt for breast reconstruction to replace the excised tissue. Silicone gel implants were initially used, but they have been banned by the FDA. Currently tissue "flaps, " containing muscle, fat, & skin taken from the patient's abdomen or back, are providing acceptable alternatives for "sculpting" a natural looking breast. Classwork (pgs. 1056 - 1061) June 1, 1999 'Female Cycles & Fertilization' The monthly series of events associated with the maturation of an egg is called the ovarian cycle. It has 2 phases: Follicular phase - the period of follicle growth.
The uterine (menstrual) cycle is a series of cyclic changes that the uterine endometrium goes through each month as it responds to changing levels of ovarian hormones in the blood. Day 1 - 5, menstrual phase (shedding of endometrium), day 6 - 14, proliferative phase (the endometrium rebuilds itself), day 15 - 28 secretory phase (the endometrium For fertilization, sperm must reach an oocyte, which is viable for 12 to 24 hours after it is cast out of the ovary. Most sperm retain their fertilizing power for 24 to 72 hours after ejaculation. For fertilization to occur, sex or coitus must occur no more than five days before ovulation or no later than 24 hours after. Fertilization occurs when a sperm fuses with an egg to form a fertilized egg or zygote.
Sperm freshly deposited in the vagina are incapable of penetrating a oocyte. They must first be capacitated (their membranes must become fragile so that the hydrolytic enzymes in their acro somes can be released). The sperm that arrive first on the scene help break down the outer layer of the egg, so other sperm can penetrate it; only one sperm is allowed in, after that there is an electrical event called the "fast block to polysemy. " Then when the 2 pron Bibliography:
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Research essay sample on Labia Minora Labia Majora
