Sexual anatomy - a summary of chapter 4 of Understanding human sexuality by Hyde and DeLamater

Sexology
Chapter 4
Sexual anatomy

Female sexual organs

The female sexual organs can be classified into two categories

• External organs
• Internal organs

External organs

The external genitals of females consist of

• The clitoris
• The mons pubis
• The inner lips
• The outer lips
• The vaginal opening

Vulva: the collective term of the external genitals of the female.
The appearance of the vulva varies greatly from one women to another.

The clitoris

Clitoris: a highly sensitive sexual organ in the female: the glans is in front of the vaginal entrance, and the rest of the clitoris extends deeper into the body.
It consists of

• Glans
  A knob of tissue situated externally in frond of the vaginal opening and the urethral opening
• A shaft consisting of two corpora cavernosa
  Extends perhaps an inch into the body
• Two crura
  Longer spongy bodies that lie deep in the body and run from the tip of the clitoris to either side of the vagina, under the major lips.

Female sexual organs and make sexual organs develop from similar tissue before birth.
The female’s clitoris is homologous to the male’s penis, both develop from the same embryonic tissue.

The clitoris has a structure similar to that of the penis in that both have corpora cavernosa.
The clitoris varies in size from one women to the next.
The clitoris is erectile.
Its internal structure contains corpora cavernosa that fill with blood, as the similar structures in the penis do.
The clitoris has a rich supply of nerve endings, making it very sensitive to stroking.
It is the only part of the sexual anatomy with no known reproductive function.

The Mons

Mons pubis: the fatty pad of tissue under the public hair.

The labia

Outer lips: rounded pads of fatty tissue lying on either side of the vaginal entrance. They are covered with public hair.
Inner lips: thin folds of skin lying on either side of the vaginal entrance.
The inner lips extend forward and come together in front, forming the clitoral hood.

The inner and outer lips are well supplied with nerve endings and thus are also important in sexual stimulation and arousal.

Bartholin glands: two tiny glands located on either side of the vaginal entrance.
Seem to have no significant function, but sometimes they become infected.

Fourchette: the place where the inner lips come together behind the vaginal opening.
Perineum: the skin between the vaginal entrance and the anus.
Introitus: the vaginal entrance.

The urinary opening lies about midway between the clitoris and the vaginal opening.
Urine passes through a separate pathway, the urethra.

Self-knowledge

Female’s external organs are much less visible than male’s.
It can be seen by using a mirror.

The hymen

The hymen: a thin membrane that, if present, may partially cover the vaginal entrance. It has openings to let the menstrual blood flow out.
At the time of first intercourse the hymen may be broken of stretched as the penis moves into the vagina.
This may cause bleeding and possibly some pain.
Some girls are born without hymen and others may tear it in active sports.

Internal organs

The internal sex organs of the female consist of

• The vagina
• The vestibular bulbs
• The Skene’s glands
• The uterus
• A pair of ovaries
• A pair of fallopian tubes

The vagina

Vagina: the tube-shaped organ in the female into which the penis is inserted during coitus and through which a baby passes during birth.
Sometimes called the birth canal.
At the bottom it ends in the vaginal opening, or introitus.
At the top it connects with the cervix (the lower part of the uterus).
During arousal it expands like a balloon, allowing space to accommodate the penis.

The walls of the vagina have three layers

• Vaginal mucosa
  The inner layer
  A mucous membrane similar to the inner lining of the mouth
• Middle layer
  Muscular
• Outer layer
  Forms a covering

The walls of the vagina are extremely elastic and are capable of expanding to the extent necessary during intercourse and childbirth, although with age they become thinner and less flexible.

The nerve supply is mostly to the lower one-third, near the introitus.
This part is sensitive to erotic stimulation.
The inner two-third of the vagina contains almost no nerve endings and is therefore relatively insensitive except to feelings of deep pressure.
Some women have a sport on the front wall of the vagina that is more sensitive than the rest of the vagina, the G-spot.

There is considerable difference in the appearance of the vulva of a women who has never had a baby (nulliparous) and the vulva of a women who has (parous).

Pelvic floor muscles: a set of muscles surrounding the vagina, the urethra and the anus.
Pubococcygeus muscle: a muscle around the vaginal entrance.

The vestibular bulbs

Vestibular bulbs: erectile tissue running under the inner lips.

The Skene’s gland or female prostate

Lies between the wall of the urethra and the all of the vagina.
In some women, it secretes fluid that is biochemically similar to male prostate fluid.
Many women find it to be a region of special erotic sensitivity on the wall of the vagina.
The size varies considerably form one women to the next, as does the amount of secretions.

The uterus

Uterus: the organ in the female in which the fetus develops.

• Cervix
  The narrow lower third that opens into the vagina
• Fundus
  The top
• The body
  The main part

The entrance to the uterus through the cervix is very narrow and is called the os.
The major function of the uterus is to hold and nourish a developing fetus.

The uterus, like the vagina, consists of three layers

• Endometrium
  Inner layer.
  Richly supplied with glands and blood vessels.
  Its state varies according to the age of the women and the phase of the menstrual cycle.
  It is the endometrium that is sloughed off at menstruation and creates the menstrual discharge
• Myometrium
  Middle layer
  Muscular
  The muscles are very strong and elastic
• Perimetrium
  Outer layer
  Forms the external cover of the uterus

The fallopian tubes

Fallopian tubes: the tubes extending from the uterus to the ovary. Also called the oviducts.
Lined with hairlike projections called ciclia.
The fallopian tubes are the pathway by which the egg travels towards the uterus and the sperm reach the egg.

Fertilization of the egg typically occurs in the infundibulum, the selection of the tube closest to the ovary.
The infundibulum curves around toward the ovary; at its end are numerous fingerlike projectios called fimbriae that extent toward the ovary.

The ovaries

Ovaries: two organs in the female that produce eggs and sex hormones.
Lie on either side of the uterus.

Each ovary contains numerous follicles.
Follicle: a capsule that surrounds an egg.
The ovaries do not connect directly to the fallopian tubes. The egg is realised into the body cavity and reaches the the tube by moving toward the fimbriae.

Breasts

The breast consists of about 15 or 20 clusters of mammary glands, each with a separate opening to the nipple, and of fatty and fibrous tissues that surround the clusters of glands.

The nipple is richly supplied with nerve endings and therefore very important in erotic stimulation for many women.
The nipple consists of smooth muscle fibres, when they contract, it becomes erect.
Areola: the darker area surrounding the nipple.

Male sexual organs

External organs

The penis

The penis serves important functions in sexual pleasure, reproduction, and elimination of body wastes by urination.

• Glans
  The tip
• Meatus or urethral opening
  The opening at the ends of the glans through which semen and urine pass
• Shaft
  The main part of the penis
• Corona
  The raised ridge at the edge of the glans

The corona and the rest of the glans are the most sexually excitable region of the male anatomy.

Urethra

• Three long cylinders of spongy tissue running parallel to the urethra inside the penis
  • Copora cavernosa
    The spongy bodies lying on top
  • Corpus songiosum
    The single one lying on the bottom of the penis
    During erection, the corpus spongiosum can be seen as a raised column on the lower side of the penis

These bodies are richly supplied with blood vessels and nerves.
Erection occurs when they become filled with blood.

Foreskin: a layer of skin covering the glans or tip of the penis in an uncircumcised male. Also called prepuce.
Under the foreskin are small glands that produce a substance called smegma, which is cheesy in structure.
The foreskin is easily retractable.
Circumcision: surgical removal of the foreskin of the penis.

Supercision: a form of male genital cutting in which a slit is made the length of the foreskin top, with the foreskin otherwise remaining intact.
Subincision: a form of male genital cutting in which a slit is made on the lower side of the penis along its entire length to the depth of the urethra.

The scrotum

Scrotum: the pouch of skin that contains the testes in the male.

Internal organs

Testes: the pair of glands in the scrotum that manufacture sperm and sex hormones
In the internal structure of the testes, two parts are important

• The seminiferous tubules
  Carry out the important function of manufacturing and storing sperm: spermatogenesis
  There are about 1000 of them
• The interstitial cells
  Produce testosterone
  Lie close to the blood vessels

One of the tricks that the scrotum and testes can perform, is to move up close to the body of down away from it.
These changes are brought about mainly by changes in temperature.
This is important because the testes should remain at a fairly constant temperature, slightly lower than normal body temperature. This is to protect the sperm.
This is possible to do the cremasteric reflex by the cremaster muscle.

Following initial cell division in the seminiferous tubules, the male germ cells go through several stages of maturation

• Spermatogonium
• Spermatocyte
• Spermatid
• Spermatozoan or sperm

Spermatogenesis: the manufacture of sperm
Occurs continuously in adult men.
A normal human sperm contains 23 chromosomes in the head.

After the sperm is manufactured in the seminiferous tubules, they proceed into the rete testes, a converging network of tubes on the surface of the testis toward the top.
The sperm then pass out of the testis and into a single tube, the epididymis.
Epididymis: a highly coiled tube located on the edge of the testis, where sperm mature. The sperm is stored here, where they master, possibly for as long as six weeks.

Upon ejaculation, the sperm pass form the epididymis into the vas deferens.
The vas passes up and out of the scrotum and then follows a paculiar circular path as it loops over the public bone, crosses beside the urinary bladder, and then turns downward toward the prostate.
As the tube passes trough the prostate it narrows and at this point is called the ejaculatory duct.
The ejaculatory duct opens into the urethra.

Sperm have no movement of their own until they mix with the secretions of the propstate.
Up to this point they are conveyed by the cilia and by contractions of the epididymis and vas.

Seminal vesicles: sacclike structures that lie above the prostate and produce about 60 percent of the seminal fluid.
The remaining 40 percent is produced by the prostate.

Prostate: the gland in the male, located below the bladder, that secretes some of the fluid in semen.
The alkalinity of the secretion provides a favourable environment for the sperm and helps prevent their destruction by the acidity of the vagina.

Cowper’s glands: glands that secrete a clear alkaline fluid into the male’s urethra.
It is thought that the function of this secretion is to neutralize the acidic urethra, allowing safe passage for the sperm.
The fluid often contains some stray sperm.

Cancer of the sex organs

Breast cancer

Cancer of the breast is the second most common form of cancer in women.

Causes

• Genetic factors
  Two breast-cancer genes of which mutations create a high risk of breast cancer and ovarian cancer
  • BRCA1 on chromosome 17
  • BRCA2 on chromosome 13
• Long term use of menopausal hormone therapy
• Obesity

Some women carrying the BRCA mutation choose to have a mastectomy before they develop cancer, as a preventive measure.

Diagnosis

Women can do breast self-exams.
Those are no substitute for mammograms and exams by clinicians.

Three kinds of breast lumps

• Cysts
  Fluid-filled sacs
• Fibroadenomas
• Malignant tumors

80 percent of breast lumps are cysts or fibroadenomas and are not dangerous.

The main technique available for early detection of breast cancer is mammography.
Taking and X ray of the breast.
This is highly reliable.
It is capable of detecting tumours that are so small that they cannot yet be felt.
But, it involves some exposure to radiation, which itself may increase the risk of cancer.

Recently, MRI scans have been developed to detect breast tumours, they are generally recommended only for high-risk cases.

Needle aspiration.
A fine needle is inserted in the breast. If the lump is a cyst, the fluid in the cyst will be drained out. If the lump disappears after this procedure, then is was a cyst and there is no need for further concern.
If the lump remains, it must be either a fibroadenoma or a malignant tumour.

Most physicians feel that only definitive way to differentiate between a fibroadenoma and a malignant tumour is to do a biopsy.
A small slit is made in the breast and the lump is removed. A pathologists then examines it to determine whether it is cancerous.

Treatment

Several forms of surgery may be performed when a breast lump is found to be malignant.

• If the lump is small and has not spread, the surgery may involve only a lumpectomy
  Lumpectomy: only the lump and a small bit of surrounding tissue are removed
• If the cancer has spread more, surgery is radical mastectomy
  Radical mastectomy: the entire breast, as well as underlying muscles and lymph nodes, is removed.
  Following surgery, radiation therapy and/or chemotherapy are used.

Therapy is generally highly effective.

Psychological aspects

The psychological impact of breast cancer and mastectomy can be enormous.
Two sources of the trauma

• Finding out that one has cancer of any kind is traumatic
• Surgery and possibly amputation of the breast is stressful

The typical emotional response of breast cancer patients is depression, often associated with anxiety.
It is common for women to have difficulty showing their incisions to their sexual partners. Relationship tensions and sexual problems may increase.

Most women gradually adapt to the stresses they have experienced.
For women who are more severely distressed, cognitive behavioural therapy with a trained therapist can be very effective.

Cancer of the cervix, endometrium and ovaries

Cancers of the cervix, endometrium, and ovaries are the most common cancers in women after breast cancer.

Approximately 95% of cases of cervical cancer are caused by HPV.
The Pap test can detect cancer long before the person has any symptoms.
A vaccine is available that prevents the most common HPV infections that cause cervical cancer.

Cancers of the ovaries and the uterine corpus have multiple symptoms, making diagnosis difficult.

• Endometrial cancer may be suspected when a woman has vaginal bleeding during times in the menstrual cycle other than her period
• Ovarian cancer symptoms
  Can be indicative of much less serious conditions

Imaging techniques such as pelvic sonogram and MRI and minimally invasive surgical techniques such as hysteroscopy can help diagnose these cancers.

Treatment for cervical cancer varies according to how advanced it is when diagnosed.

Hysterectomy: surgical removal of the uterus.

Cancer of the prostate

Cancer of the prostate is the second leading cause of cancer death in men.
Most cases are not lethal, and survival rates are high.

Early symptoms of prostate cancer

• Frequent urination
• Difficulty in urination
• Difficulty emptying the bladder
• Frequent erections and increase in sex drive
  But, as the disease progress, there are often problems with sexual functioning

Preliminary diagnosis of prostate cancer is by rectal examination.
But some men dislike the discomfort and it is not 100 percent accurate.
A blood test can be done as well.

Treatment often involves surgical removal of some or all of the prostate, plus some type of hormone therapy, radiation therapy, or anticancer drugs.

Cancer of the penis is rare compared to prostate cancer.

Cancer of the testes

Not a particularly common form of cancer.
Tends to be a disease of young men.
The first sign is usually a painless lump in the testes, or a sight enlargement or change in consistency of the testes.

When a lump is reported to a physician early and is localized, the survival rate is 99%.

Not every lump in the testes is cancerous.

Diagnoses is made by a physician’s examination of the testes and by ultrasound.
Final diagnosis involves surgical removal of the entire testis. The other testis remains.