Essay, Research Paper: Female Anatomy

The Vagina The vagina is a thin walled-tube, 8 to 10 cm long. It lies between thebladder & the rectum & extends from the cervix to the body exterior. Theurethra is embedded in its anterior wall. Often called the birth canal, thevagina provides a passageway for delivery of an infant & for menstrualflow. Since it receives the penis (& semen) during sexual intercourse, it isthe female organ of copulation.The highly distensible wall of the vagina wall consists of three coats:An outer fibroelastic adventitia.A smooth muscularis.A mucosa marked by transverse ridges or rugae, which stimulate thepenis during intercourse. The epithelium of the mucosa is a stratified squamous epithelium adaptedto stand up to friction. Certain of the mucosal cells act asantigen-presenting cells & are thought the route of HIV transmission froman infected male to the female during intercourse. The vaginal mucosahas no glands; it is lubricated by the cervical mucous glands. Its epithelialcells release large amounts of glycogen, which is anaerobically metabolizedto lactic acid by resident bacteria. Consequently, the pH of a woman svagina is normally quite acidic. This acidity helps keep the vagina healthy& free of infection, but it is also hostile to sperm. Although vaginal fluid ofadult woman is acidic, it tends to be alkaline in adolescents, predisposingsexually active teenagers to sexually transmitted diseases. In virgins, the mucosa near the distal vaginal orifice forms anincomplete partition called the hymen. The hymen is very vascular & tendsto bleed when it is ruptured during the first coitus (sexual intercourse). However, its durability varies. In some females, it is ruptured during asports activity, tampon insertion, or pelvic examination. Occasionally, it isso though that it must be breach surgically if intercourse is to occur.The upper end of the vaginal canal loosely surrounds the cervix of theuterus, producing a vaginal recess called the vagina fornix. The posteriorpart of this recess, the posterior fornix, is much deeper than the lateral &anterior fornices. Generally, the lumen of the vagina is quite small &,except where it is held open by the cervix, its posterior & anterior walls arein contact with one another. The vagina stretches considerably duringcopulation & childbirth, but its lateral distension by the ischial spines & thesacrospinous ligaments.The uterus tilts away from the vagina. Hence, attempts by untrainedpersons to induce an abortion by entering the uterus with a surgicalinstrument may result in puncturing of the posterior wall of the vagina,followed by hemorrhage & - if the instrument is unsterile - subsequentperitonitis. The External GenitaliaThe external genitalia, also called the vulva or pudendum, include the:M0ns, pubis.Labia.Clitoris.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 posteriorlyfrom the mons pubis are two elongated, hair-covered fatty skin folds, thelabia majora. These are the female counterpart of the male scrotum. Thelabia majora enclose the labia minora, two thin , hair-free skin folds,homologous to the ventral penis. The labia minora enclose a recess calledthe vestibule, which contains the external opening of the urethra moreanteriorly followed by that of the vagina. Flanking the vaginal opening arepea-sized greater vestibular glands, homologous to the bulbourethralglands of the males. These glands release mucus into the vestibule & helpto keep it moist & lubricated, facilitating intercourse.Just anterior to the vestibule is the clitoris, a small, protrudingstructure, composed largely of erectile tissue, that is homologous to thepenis of the male. It is hooded by a skin fold called the prepuce of theclitoris, formed by the junction of the labia minora folds. The clitoris isrichly innervated with sensory nerve endings sensitive to touch, & itbecomes swollen with blood & erect during tactile stimulation, contributingto a female s sexual arousal. The clitoris has dorsal erectile columns; but itlacks a corpus spongiosum. The female urinary & reproductive tracts arecompletely separate, & neither runs through the clitoris. The female perineum is a diamond-shaped region located between thepubic arch anteriorly, the coccyx posteriorly, & the ischial tuberositieslaterally. The soft tissues of the perineum overlie the muscles of the pelvicoutlet & the posterior ends of the labia majora overlie the central tendon,into which most muscles supporting the pelvic floor insert. The Mammary GlandsThe mammary glands are present in both sexes, but they normallyfunction only in females. Since the biological role of the mammary glandsis to produce milk to nourish a newborn baby, they are actually importantwhen reproduction has already been accomplished. Developmentally, the mammary glands are modified sweat glands thatare really part of the skin, or integumentary system. Each mammarygland is contained within a rounded skin-covered breast anterior to thepectoral muscles of the thorax. Slightly below the center of each breast isa 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 whenstimulated by tactile or sexual stimuli & when exposed to the cold. Internally, each mammary gland consists of 15 to 25 lobes that radiatearound & open at the nipple. The lobes are padded & separated from eachother by fibrous connective tissue & fat. The interlobular connective tissueforms suspensory ligaments that attach the breast to the underlyingmuscle fascia to the overlying dermis. As suggested by their name, thesuspensory ligaments provide natural support for the breast, like a built-inbrassiere. Within the lobes are smaller units called lobules, which containgrandular alveoli that produce milk when a woman is lactating. Thesecompound alveolar glands pass the milk into the lactiferous ducts, whichopen to the outside at the nipple. Just deep to the areola, each lactiferousduct has a dilated region called a lactiferous sinus. Milk accumulates inthese sinuses during nursing. In non-pregnant women, the grandular structure of the breast islargely undeveloped & the duct system is rudimentary; hence, breast sizeis largely due to the amount of fat deposits.Breast CancerInvasive breast cancer, the most common malignancy of US women,strikes about 180,000 American women each year. One in eight womenwill develop this condition. Breast cancer usually arises from the epithelialcells of the ducts, not from the alveoli. A small cluster of cancer cellsgrows 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.Previous history of breast cancer.Family history of breast cancer (especially sister or mother).Other risk factors proposed but as yet unproved include:Silicone breast implants.Exposure to high estrogen concentrations while in utero &post-menopause.Cigarette smoking & excessive alcohol intake.Some 10 % of breast cancers stem from hereditary defects & half of thesecan be traced to dangerous mutations in a pair of genes, dubbed BRCA1 &BRCA2, which virtually guarantee that the carriers will develop breastcancer. However, more than 70 % of women who develop breast cancerhave no known risk factors for the disease.Breast cancer is often signaled by a change texture, puckering, orleakage from the nipple. Early detection by breast self-examination &mammography is unquestionably the best way to increase one s chancesof surviving breast cancer. Simple self-examinations should be healthmaintenance priority in every women s life. The American Cancer Societyrecommends scheduling mammography, X-ray examinations that detectsbreast cancers too small to feel, every two years for women between 40 to49 years old & yearly thereafter.Once diagnosed, breast cancer is treated in various ways:Radiation therapy.Chemotherapy.Surgery, often followed by irradiation or chemotherapy, to destroystray cancer cells. Radical mastectomy is the removal of the entire affected breast, plus allunderlying muscles, fascia, & associated lymph nodes. Medical recordsreveal that this painful & disfiguring treatment is no more effective athalting the cancer than less extensive surgery. Most physicians nowrecommend lumpectomy, in which only the cancerous part is excised, or asimple mastectomy, removal of the breast tissue only. Many mastectomy patients opt for breast reconstruction to replace theexcised tissue. Silicone gel implants were initially used, but they have beenbanned by the FDA. Currently tissue flaps, containing muscle, fat, & skintaken from the patient s abdomen or back, are providing acceptablealternatives 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 eggis called the ovarian cycle. It has 2 phases:Follicular phase - the period of follicle growth.Luteal phase - ovulation occurs.The uterine (menstrual) cycle is a series of cyclic changes that theuterine endometrium goes through each month as it responds to changinglevels of ovarian hormones in the blood. Day 1-5, menstrual phase(shedding of endometrium), day 6-14, proliferative phase (theendometrium rebuilds itself), day 15-28 secretory phase (the endometriumprepares for implantation).For fertilization, sperm must reach an oocyte, which is viable for 12 to 24hours after it is cast out of the ovary. Most sperm retain their fertilizingpower for 24 to 72 hours after ejaculation. For fertilization to occur, sex orcoitus must occur no more than five days before ovulation or no later than24 hours after. Fertilization occurs when a sperm fuses with an egg toform a fertilized egg or zygote. Sperm freshly deposited in the vagina areincapable of penetrating a oocyte. They must first be capaciated (theirmembranes must become fragile so that the hydrolytic enzymes in theiracrosomes can be released). The sperm that arrive first on the scene helpbreak 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 calledthe fast block to polyspermy. Then when the 2 pronuclei join, the resultis fertilization, or a zygote.