Human sexual anatomy

Human sexual anatomy

Female Sexual Biology • Basic Reproductive Process • Internal Ovulation - Human ova are released and remain inside the body • Insemination – sperm are deposited into the female vagina leading to fertilization • Internal Fertilization – Ova are fertilized in a fallopian tube • Intrauterine Development – Embryonic and fetal development take place inside a female’s uterus • Postnatal Care – infants are fed milk produced by the female’s breasts

Female genitalia have long been a source of fascination, recently of celebration but generally of confusion. Today it seems that creating images of the vagina is the sole preserve of pornographers, erotic artists and feminists. Step in British artist Jamie McCartney who has grasped the nettle to create a monumental wall sculpture all about this most intimate of places. For 400 women their privates have gone public... • Half a decade since its humble beginnings, The Great Wall of Vagina has enticed women from many different countries and all walks of life to volunteer to be cast by McCartney in an overwhelmingly positive reaction to the project. • The 9 metre long polyptych consists of four hundred plaster casts of vulvas, all of them unique, arranged into ten large panels. McCartney set out to make this project as broad and inclusive as possible. The age range of the women is from 18 to 76. Included are mothers and daughters, identical twins, transgendered men and women as well as a woman pre and post natal and another one pre and post labiaplasty.

Female Primary and Secondary Sex Characteristics • Primary Sex Characteristics – Organs that contribute to reproduction and sexual activity • Secondary Sex Characteristics – Female characteristics that are not involved in reproduction, e.g. breasts, wider hips, more body fat, less hair on arms, legs and torso, smaller stature

Ovaries • Two in each female • Size of an almond • Produce ova and sex hormones (estrogen and progesterone) • 7 million immature ova produced by the ovaries as a fetus, this number begins to fall immediately, none left by age 50 • Menopause – cessation of ovum production and this cessation of menstrual periods

Fallopian Tubes • Two in each female • Runs 10 cm from the uterus opening to the pelvic cavity • Fingerlike projections sweep over the surface of the adjacent ovary • When an ovum is released it rises off the surface of the ovary and the fimbriae of the adjacent fallopian tube capture it • If sperm are present fertilization occur inside the tube

Uterus • Hollow pear shaped organ about the size of a woman’s fist and situated behind the bladder • Once an egg is fertilized it travels down the fallopian tube and into the uterus where implantation occurs, this allows development to take place

Uterus • Outer Layer • Fibrous connective tissue • Middle Layer • Muscle fibers for contractions • Inner Layer • Endometrium builds up every month in preparation for pregnancy • If pregnancy does not occur then this is expelled as the menstrual period

Uterus • Cervix • Connects the uterus to the vagina • Glands secrete cervical mucus • Pap Smear checks for cancer in the cervix

Vagina • Hollow tube extending from the cervix outside the body • With sexual excitement there is an increase of blood flow and secretion of lubricating fluid • G-Spot • About the size of a dime • Some women find stimulation in this area sexually arousing

Vagina • Constant secretions help control the growth of microorganisms in the vagina and cleanse the area • Vaginitis • A vaginal infection, “Yeast Infection” • Symptoms – irritation or itching of the vagina and vulva, unusual discharge and sometimes a disagreeable odor

Vagina • Hymen – thin piece of connective tissue at the entrance of the vagina • Likely to be torn or disrupted by a penis during intercourse

External Genitalia • Vulva – contains the external genitalia • Covered by a small mound of fatty tissue, which is covered by pubic hair • Perineum – region between the lower part of the vagina and the anus • Labia Minora and Majora • Minora – smaller, inner pair of folds surrounding the opening of the vagina • Majora – larger outer pair of folds • Both become engorged with blood when a woman is sexually excited

External Genitalia • Clitoris – an erotically sensitive organ located just above the urethra where the inner vaginal lips converge • Composed of a glans and a shaft • Shaft is made up of two cylindrical spongy bodes which extend along the sides of the vagina • With sexual excitement they become engorged with blood

Urethra • Exit tube for urine • Because of its location it is at risk of infection when bacteria is introduced or its opening is irritated • UTI Prevention • Urinate immediately after intercourse • Wipe front-to-back after urinating • After anal stimulation cleanse fingers or penis before vaginal entry

Urethra • UTI Symptoms • Frequent urge to urinate • Burning sensation with urination • Easily treated with medication • A mild case can be helped with drinking a lot of fluids and acidifying the urine by taking vitamin C or drinking cranberry juice

Urethra • Urinary Incontinence • Difficulty controlling urination • 25% of women • Involuntary leaking, urgent need to urinate • Situational – when lifting, sneezing, coughing or laughing • Treated with pelvic muscle strengthening exercises, surgery or medication

Female Sex Steroid Hormones • Ovaries produce estrogenic hormones, progesterone and testosterone • Female adrenal glands produce DHEA • Estrogens • Fetal sexual and reproductive organ development • Breasts, female hair pattern and fat deposition at puberty • Maintaining vaginal health and lubrication • Skin elasticity

Female Sex Steroid Hormones • Progesterone • Preparing for and maintaining pregnancy • Androgens • Genital and underarm hair growth • Maintenance of interest in erotic experience and aggression • Acne • Agricultural and Industrial Chemicals • Xenestrogens • Can inhibit or stimulate estrogen-dependent processes

Breasts • Mostly fat with 20% glandular tissue • Also connective tissue, blood vessels and nerves • Glandular Tissue divided into 15-20 lobules • Lobules contain clusters of milk-producing alveoli • Breast cancer results from uncontrolled, estrogen-stimulated, reproduction of cells that line the milk ducts

Breasts • Areola • Circular pigmented region around the nipple • Sebaceous glands provide protective lubricant • Contain muscle fibers that contract in response to sucking, cold and erotic arousal which produces nipple erection • Skin is soft and thin • Males have glandular breast tissue that can produce milk if hormonally activated • Newborns of both sexes occasionally express milk because of the mother’s hormones

Menstrual Cycle • Each cycle is preparation for pregnancy • Thickening of the uterus lining – endometrium • Growth of special blood vessels in endometrium for nutrient delivery to embryo • Menstruation – endometrium and special blood vessels are sloughed off because pregnancy has not occurred • 3-6 days

Menstrual Cycle • Cycle lasts 24-35 days • Some take hormonal contraceptives to regulate their menstrual cycle, extend the time between periods, suppress menstruation • Regulated by HPG system • Hypothalamo • Pituitary • Gonadal

Menstrual Cycle • Hypothalamo • Nerve cells in the brain’s hypothalamus, manufactures and releases GnRF (Gonadotropin Releasing Factor) • GnRF levels rise and fall, causing the cyclic nature of the menstrual cycle.

Menstrual Cycle • Pituitary • Cells in the pituitary gland (located at the base of the brain) • Responds to GnRF by releasing FSH (follicle stimulating hormone) and LH (luteinizing hormone)

Menstrual Cycle • Gonadal • Estrogen and progesterone production by the ovaries • Estrogen is controlled by FSH • Progesterone is controlled by LH • Both of these help regulate the HPG system

Menstrual Cycle • Phases • Menstrual Phase (Days 1-5) – First day of bleeding starts the cycle • Estrogen and progesterone levels are low • Proliferative Phase (Days 6-14) • Low estrogen through the previous phase trigger an increase in GnRF and FSH production • Ovum matures and ovaries produce estrogen • Proliferation of the uterus lining and uterine blood vessels

Menstrual Cycle • Phases • Ovulation Phase (Days 14-15) • Rising levels of estrogen causes a surge of LH production, triggers a mature ovum to be released from an ovary • Secretory Phase (Days 16-28) • FSH and LH stimulate the production of estrogen and progesterone from the corpus luteum. • Next Menstrual Phase

Menstrual Cycle • Menstrual Difficulties • Dysmenorrhea • “cramps” or abdominal pain during the first part of menstruation • Usually caused by prostaglandins, inducing strong contractions of the uterine muscle tissue • Promote removal of the menstrual tissue from the body • Can be caused my endometriosis, pelvic inflammatory disease, uterine fibroids or tumors in the pelvic cavity.

Menstrual Cycle • Menstrual Difficulties • Premenstrual Syndrome • 75% of women • Changes in feelings and disposition as menstruation approaches and during the first few days of menstruation • Premenstrual dysphoric disorder – combination of marked mood swings, depression, irritability and anxiety, affects normal daily life • Decrease caffeine, sugar and salt intake, increase exercise and intake of B-6 and calcium can help

Menstrual Cycle • Menstrual Difficulties • Amenorrhea • Interruption or cessation of regular menstrual periods • Due to pregnancy, psychological stress, depression, marital or sexual problems, fatigue, ingestion of opiate drugs, etc. • Calorie restriction and extreme exercise level, which decreases body fat to an abnormally low level

Menstrual Cycle • Menstrual Difficulties • Endometriosis • 10% of women • Endometrial tissue detaches from the uterus and lodges in ovaries or fallopian tubes • Tissue remains responsive to hormones, so it grows, degenerates and bleeds causing severe pain. • Treated surgically or with medication

Menstrual Cycle • Menstrual Difficulties • Toxic Shock Syndrome • Caused by a toxin that can colonize menstrual fluids • Symptoms – sudden fever, chills, vomiting, diarrhea, muscle aches and rash • Progresses rapidly • Fatal in 5% of cases • Risk reduced by changing tampons regularly, using lower absorbency tampons (not super)

Male Sexual Biology • Primary sex characteristics – directly involved in the production and delivery of sperm or eggs, fertilization and pregnancy • Testes – sperm and sex hormones produced • Genital duct system – sperm transported from the testes to the outside • Glands – produce seminal fluid • Penis

Male Sexual Biology • Secondary sex characteristics – anatomical and physiological features not primarily involved in the delivery of sperm or eggs or the maintenance of pregnancy, but are specific to members of a particular sex • Males are larger, stronger, have broader shoulders, slimmer hips and have prominent facial hair • Males tend to be aggressive, dominant and adept at spatial cognitive tasks • Generally the result of androgenic hormones

Male Sexual Biology • Understanding one’s own and a partner’s sexual biology can foster healthy sexuality

The Testes • Pair of oval-shaped organs • Produce sperm & sex hormones • Testosterone • Located in the scrotum, a sac-like structure that is attached to the front of the pelvis • Suspended in the scrotum by the spermatic cord • Contains nerves, blood vessels, a sperm duct (vas deferens) and a thin muscle (cremaster) • Cremaster raises and lowers the testis in response to cold, fear, anger and sexual stimulation

The Testes • Both testes develop inside a growing fetus, descend into the scrotum just before birth • Temperature • In the scrotum the testes are 5 degrees cooler than normal body temp • Necessary for sperm viability • Prolonged exposure to heat decreases viable sperm production • Coiled seminiferous tubules • 150 million sperm produced daily

The Genital (Sperm) Duct System • Long Y-shaped tube divided into four parts through which sperm move from the testes to the outside • Epididymis • Vas Deferens • Ejaculatory Duct • Urethra

The Genital (Sperm) Duct System • Epididymis • Lies on the back of the testis • 6 meters of tubule densely coiled to approx 4 cm • Damaged sperm are removed and remaining are concentrated into a dense mass and become capable of fertilizing an egg • Vas Deferens • Moves sperm from the epididymis up to the pelvic cavity • Vasectomy involves blocking the movement of the sperm into the penis by surgically removing a portion of the vas deferens

The Genital (Sperm) Duct System • Ejaculatory Duct • A short straight tube between the vas deferens and the urethra • Urethra • Exit tube for the sperm and urine • A small band of smooth muscle surrounding the urethra near the bladder closes off the bladder blocking ejaculate from entering the bladder • Makes it difficult to urinate when the penis is erect

Fluid Producing Glands • Sperm become mixed with secretions from three fluid-producing glands as they move through the genital duct system • Upon ejaculation the glands empty their contents into tubes that connect to the genital ducts • Seminal Vesicles • Prostate Gland • Cowper’s (Bulbourethral) glands

Fluid Producing Glands • Seminal Vesicles • Two vesicles located near the junction of each vas deferens and ejaculatory duct • Prostate Gland • Chestnut-sized organ surrounding the urethra near its origin at the bladder • Cowper’s (Bulbourethral) glands • Pair of pea-sized organs located along the urethra near the prostate

Fluid Producing Glands • Semen • Mixture of seminal fluid and sperm • Seminal fluid is produced in the seminal vesicles and prostate • Made of water, fructose, vitamins, minerals and proteins • Fluid nurtures sperm, protects it from attack by the female immune system and neutralizes the acidity of the vagina • 95% seminal fluid, 5% sperm

Fluid Producing Glands • Cowper’s (Bulbourethral) glands • Pair of pea-sized organs located along the urethra near the prostate • Produces small amounts of “pre-ejaculate”, a lubricating fluid that enters the urethra soon after a man becomes sexually aroused and before ejaculation • Contains few if any sperm • Can carry HIV

Ejaculation • The release of semen from the penis • Nerve signals from the brain travel down the spinal chord to the smooth muscle tissue that surrounds the tubes of the genital ducts and the fluid producing glands • Emission Phase • Expulsion Phase

Ejaculation • Emission Phase • Contraction of the smooth muscle forces seminal fluid into the genital duct system and propels semen to the prostate • Blocked temporarily by the prostatic urethra • Expulsion Phase • Semen collected my the prostatic urethra is forcefully propelled from the body by strong, rhythmic contractions of pelvic muscles and the smooth muscle surrounding urethra • “Wet Dreams” – spontaneous ejaculations during sleep

The Penis • Glans - Head • Shaft • Corpora cavernosa – two portions make the top of the penis • Corpus spongiosum – lies underneath and contains urethra

Human sexual anatomy