Female Anatomy Essay, Research Paper
‘The Vagina’
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 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 the
penis during intercourse.
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 fornices. 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
sacrospinous ligaments.
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
peritonitis.
The External Genitalia
The 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 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
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 s
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 interlobular 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
grandular 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
these sinuses during nursing.
In non-pregnant women, the grandular structure of the breast is
largely undeveloped & the duct system is rudimentary; hence, breast size
is largely due to the amount of fat deposits.
Breast Cancer
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.
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 these
can be traced to dangerous mutations in a pair of genes, dubbed BRCA1 &
BRCA2, 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
49 years old & yearly thereafter.
Once diagnosed, breast cancer is treated in various ways:
Radiation therapy.
Chemotherapy.
Surgery, often followed by irradiation or chemotherapy, to destroy
stray cancer cells.
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.
Luteal phase – ovulation occurs.
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
prepares for implantation).
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 capaciated (their
membranes must become fragile so that the hydrolytic enzymes in their
acrosomes 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 polyspermy.” Then when the 2 pron