Reproductive Systems

Dr. Michael P. Gillespie

Sexual Reproduction

Process by which organisms produce offspring by making germ cells called gametes.

The male gamete (sperm cell) unites with the female gamete (secondary oocyte). This is called fertilization.

The resulting cell contains one set of chromosomes from each parent.

Reproductive Organs

Males and females have anatomically distinct reproductive organs that are adapted for producing gametes, facilitating fertilization, and in females sustaining the growth of the embryo and fetus.

Reproductive Organs

The male and female reproductive organs can be grouped by function.

Gonads – testes in males and ovaries in females. Produce gametes and secrete sex hormones.

Reproductive Organs

Ducts – store and transport gametes. Accessory sex glands – produces substances that

protect the gametes and facilitate movement. Supporting structures:

Penis – facilitates delivery of gametes. Uterus – facilitates delivery and joining of gametes.

Facilitates growth of fetus during pregnancy.

Gynecology

Specialized branch of medicine concerned with diagnosis and treatment of diseases of the female reproductive system.

Urology

The study of the urinary system. Urologists also diagnose and treat diseases of

the male reproductive system.

Number Of Chromosomes

Human somatic cells contain 23 pairs of chromosomes, or a total of 46 chromosomes.

One member of each pair is inherited from each parent.

The members of each pair are called homologous chromosomes or homologs. They contain similar genes.

Number Of Chromosomes

Most of the homologs look the same with the exception of the sex chromosomes (designated X & Y).

Females carry to large X chromosomes. Males carry one large X and one small Y chromosome.

The other 22 pairs of chromosomes are called autosomes.

Number Of Chromosomes

Somatic cells contain 2 sets of chromosomes, so they are called diploid cells.

Geneticists use the symbol n to denote the number of different chromosomes in an organism.

In humans, n = 23. Diploid cells are 2n.

Meiosis

The reproductive cell division that occurs in the gonads.

It produces gametes in which the number of chromosomes is reduced by half.

Gametes contain a single set of 23 chromosomes and are called haploid cells.

Fertilization restores the diploid number of chromosomes.

Male Reproductive System

The organs of the male reproductive system are the testes, ducts, accessory sex glands, and supporting structures including the scrotum and penis.

The testes produce sperm and secrete hormones. A system of ducts transports and stores sperm. Semen contains sperm plus the secretions provided

by the accessory sex glands.

Functions Of The Male Reproductive System

Testes: produce sperm and the male sex hormone testosterone.

Ducts: transport, store, and assist in maturation of sperm.

Accessory sex glands: secrete most of the liquid portion of the sperm.

Penis: contains the urethra, a passageway for ejaculation and the excretion of urine.

Scrotum

The scrotum is the supporting structure for the testes.

Externally, the scrotum looks like a single pouch of skin separated into lateral portions by a median ridge of skin called the raphe.

Internally, the scrotal septum separates the scrotum into two sacs, each containing a single testis.

The septum contains muscle tissue called the dartos muscle.

Scrotum

When the dartos muscle contracts, it wrinkles the skin of the scrotum and elevates the testes.

The location of the scrotum and the contraction of its muscle fibers regulate the temperature of the testes.

Scrotum

Normal sperm production requires a temperature about 2-3 degrees C below core body temperature.

The scrotum is outside of the pelvic cavity and therefore maintains a lower temperature.

The cremaster muscle elevates the testes upon exposure to cold and during sexual arousal. This moves the testes closer to the pelvic cavity, where they can absorb body heat. The procedure is reversed in response to warmth.

Testes

The testes, or testicles, are paired oval glands.

A serous membrane called the tunica vaginalis partially covers the testes.

Testes

The tunica albuginea is internal to the tunica vaginalis and divides the testes into lobules.

The lobules contain 200-300 seminiferous tubules where sperm are produced. 2 types of cells:

Spermatogenic cells – sperm forming cells.Sertoli cells – supporting cells.

Testes

Spermatogenesis is the process by which sperm is produced.

Leydig cells lie between the seminiferous tubules and produce testosterone.

Cryptorchidism

A condition in which the testes do not descend into the scrotum.

It occurs in about 3% of full-term infants and 30% of premature infants.

Cryptorchidism

Untreated b/l cryptorchidism often results in sterility due to high temperatures.

The testes of about 80% of boys with cryptorchidism descend spontaneously within the 1st year of life.

Untreated, it results in a greater chance of testicular cancer.

Sperm

Spermatogenesis produces about 300 million sperm per day.

Once ejaculated, most sperm do not survive more than 48 hours in the female reproductive tract.

The sperm consists of a head with an acrosome (lysosomelike vesicle) and a nucleus with a haploid # of chromosomes (23).

Sperm

Enzymes within the acrosome aid in penetration of the sperm cell into the secondary oocyte.

The midpiece contains mitochondria. The tail is a typical flagellum that propels the

sperm cell.

Hormonal Control Of The Testes

Gonadotropin-releasing hormone (GnRH) – at puberty, the hypothalamus begins to release this hormone, which stimulates the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH).

LH stimulates Leydig cells to secrete testosterone. FSH and testosterone stimulate spermatogenesis.

Ducts Of The Testis

Pressure generated by the fluid secreted by Sertoli cells pushes sperm and fluid along the lumen of the seminiferous tubules into the straight tubules.

The straight tubules lead to the rete testis and then into the efferent ducts. The efferent ducts empty into the ductus epididymis.

Epididymis

The epididymis is a comma-shaped organ that lies along the posterior border of each testis.

The ductus epididymis is the site where the sperm mature.

Sperm are stored here and peristaltic contraction propels them into the ductus (vas) deferens.

Sperm may remain here for a month or more.

Ductus Deferens

Within the tail of the epididymis, the ductus becomes less convoluted and is known as the ductus deferens or vas deferens.

Functionally, the ductus deferens stores sperm and conveys them toward the urethra by peristaltic contractions of the muscular coat.

Sperm that are not ejaculated are eventually reabsorbed.

Spermatic Cord

The spermatic cord is a supporting structure of the male reproductive system that ascends out of the scrotum.

The spermatic cord passes through the inguinal canal into the abdomen.

Spermatic Cord

The canal originates at the deep (abdominal) inguinal ring, a slitlike opening in the aponeurosis of the transversus abdominis muscle.

The canal ends at the superficial (subcutaneous) inguinal ring, an opening in the aponeurosis of the external oblique muscle.

Inguinal Hernias

The inguinal region is a weak area in the abdominal wall.

Consequently, it is often the site of an inguinal hernia – a rupture or separation of a portion of the inguinal area of the abdominal wall.

Inguinal Hernias

Indirect inguinal hernia – part of the small intestine protrudes through the deep inguinal ring and enters the scrotum.

Direct inguinal hernia – a portion of the small intestine pushes into the posterior wall of the inguinal canal causing a localized bulging in the wall of the canal.

Ejaculatory Ducts

The ejaculatory ducts are formed by the union of the duct from the seminal vesicle and the ampulla of the ductus deferens.

They eject sperm and seminal vesicle secretions into the urethra just before ejaculation (propulsion of semen from the urethra to the exterior).

Urethra

In males, the urethra is the shared terminal duct of the reproductive and urinary systems.

Accessory Sex Glands

The accessory sex glands secrete most of the liquid portion of the semen.

They include the seminal vesicles, the prostate, and the bulbourethral glands.

Functions Of The Accessory Sex Gland Secretions

Seminal vesicles – secrete alkaline, viscous fluid that helps neutralize the acid secretions of the female reproductive tract. Provides fructose for ATP production by sperm. Contributes to sperm motility, viability, and helps semen coagulate after ejaculation.

Functions Of The Accessory Sex Gland Secretions

Prostate – secretes a milky, slightly acidic fluid that helps semen coagulate after ejaculation and subsequently breaks down the clot.

Bulbourethral (Cowper’s) glands – secrete alkaline to neutralize the acidic environment of the urethra and mucous to lubricate the lining of the urethra and tip of the penis during intercourse.

Semen

Semen is a mixture of sperm and seminal fluid, a liquid that consists of the secretions of the seminiferous tubules, seminal vesicles, prostate, and bulbourethral glands.

Semen has a slightly alkaline ph of 7.2 – 7.7.

Semen

The prostatic secretions give the fluid a milky appearance, whereas fluids from the seminal vesicles and bulbourethral glands give it a sticky consistency.

Seminal fluid provides sperm with a transportation medium, nutrients, and neutralizes the hostile acidic environment of the male urethra and female vagina.

Penis

The penis contains the urethra and is a passageway for the ejaculation of semen and the secretion of urine.

It is cylindrical in shape and consists of a root, body, and glans penis.

Root of the penis is the attached (proximal) portion. It consists of the following: Bulb of the penis (expanded portion of the base). Crura of the penis (the 2 separated and tapered portions).

Penis

Body of the penis. Glans of the penis – a slightly enlarged,

acorn-shaped region (distal region). The prepuce (foreskin) covers the glans in an

uncircumcised penis. The fundiform ligament and the suspensory

ligament of the penis arise from the pubic symphisis and support the weight of the penis.

Erection

Upon sexual stimulation, the arteries supplying the penis dilate and large quantities of blood enter the sinuses.

The stimulation may be visual, tactile, auditory, olfactory, or imagined.

Erection

Expansion of these spaces compresses the veins draining the penis, so blood outflow is slowed.

These vascular changes are due to the local release of nitric oxide and a parasympathetic reflex and result in an erection (the enlargement and stiffening of the penis).

Return to a flaccid state occurs when the arteries constrict and pressure on the veins is relieved.

Ejaculation

Ejaculation is a sympathetic reflex. The smooth muscle sphincter at the base of

the urinary bladder closes; Therefore, urine is not expelled during ejaculation and semen does not enter the urinary bladder.

Ejaculation

Before ejaculation occurs, peristaltic contractions occur and propel semen into the penile portion of the urethra. This leads to emission, the discharge of a small volume of semen before ejaculation.

Emission may also occur during sleep (nocturnal emission).

Circumcision

Circumcision is a surgical procedure in which part or the entire prepuce is removed.

It is usually performed just after delivery, 3 to 4 days after birth, or on the 8th day as part of a Jewish religious rite.

The following benefits may result from circumcision: lower risk of urinary tract infections, protection against penile cancer, and possibly a lower risk of STDs.

Organs Of The Female Reproductive System

Ovaries Uterine (Fallopian) tubes {oviducts} Uterus Vagina External organs

Functions Of The Female Reproductive System

Ovaries – produce secondary oocytes and hormones (progesterone, estrogens, inhibin, & relaxin).

Uterine tubes – transport a secondary oocyte to the uterus and normally are the sites where fertilization occurs.

Functions Of The Female Reproductive System

Uterus – site of implantation of a fertilized ovum, development of the fetus during pregnancy, and labor.

Vagina – receives the penis during sexual intercourse and is a passageway for childbirth.

Mammary glands – synthesize, secrete, and eject milk for nourishment of the newborn.

Ovaries

The female gonads are the 2 ovaries. They lie on either side of the uterus. They produce the gametes that develop into

mature ova (eggs) after fertilization. They produce the hormones progesterone,

estrogens (female sex hormones), inhibin, and relaxin.

Supporting Ligaments Of The Ovaries

Broad ligament of the uterus attaches to the ovaries and holds them in position.

Ovarian ligament anchors the ovaries to the uterus.

Suspensory ligament attaches the ovaries to the pelvic wall.

Uterine Tubes

Females have two uterine (fallopian) tubes, or oviducts that extend laterally from the uterus.

They provide a route for the sperm to reach an ovum and transport secondary oocytes and fertilized ova from the ovaries to the uterus.

Local currents produced by movements of the fimbriae (fingerlike projections) sweep the ovulated secondary oocyte from the pelvic cavity into the uterine tube.

Fertilization

A sperm usually encounters and fertilizes a secondary oocyte in the ampulla of the uterine tube.

Fertilization can occur at anytime within 24 hours after ovulation.

Fertilization

After fertilization, the nuclear materials of the haploid ovum and sperm unite.

The diploid fertilized ovum is called a zygote and begins to undergo cell divisions while moving toward the uterus.

It arrives at the uterus 6 to 7 days after ovulation.

Uterus

The uterus (womb) serves as part of the pathway for sperm deposited in the vagina to reach the uterine tubes.

It is the site of implantation of a fertilized ovum, development of the fetus during pregnancy, and labor.

During reproductive cycles when impantation does not occur, the uterus is the source of menstrual flow.

Anatomy Of The Uterus

Anatomical divisions of the uterus include: Fundus – a dome shaped portion superior to the uterine

tubes. Body – a tapering central portion. The uterine cavity lies

in here. Cervix – an inferior narrowing portion that opens into the

vagina. The interior is called the cervical canal. It opens into the uterine cavity at the internal os and into the vagina at the external os.

The isthmus is the portion between the body and the cervix.

Anatomy Of The Uterus

Anteflexion - normally, the body of the uterus projects anteriorly and superiorly over the urinary bladder.

Retroflexion – A posterior tilting of the uterus. The uterosacral ligaments, cardianl (lateral cervical)

ligaments, and round ligaments normally hold the uterus in anteflexion, but can permit enough movement for the uterus to become malpositioned.

Uterine Prolapse

Uterine prolapse is a falling down or downward displacement of the uterus.

This condition may result from weakening of supporting ligaments and pelvic musculature.

Uterine Prolapse

This is associated with disease, traumatic vaginal delivery, chronic straining from coughing or difficult bowel movements, or pelvic tumors.

Uterine Prolapse

Degrees of prolapse: 1st degree (mild) – the cervix remains within the

vagina, 2nd degree (marked) – the cervix protrudes to the

exterior through the vagina. 3rd degree (complete) – the entire uterus is

outside the vagina.

Uterine Prolapse

Treatment varies depending upon the degree of prolapse: Pelvic exercise. Dieting if the patient is overweight. A stool softener to minimize straining during defecation. Pessary therapy – placement of a rubber device around

the uterine cervix to prop up the uterus. Surgery.

Hysterectomy

Hysterectomy is the surgical removal of the uterus. It is the most common gynecological operation. It may be indicated in conditions such as

endometriosis, pelvic inflammatory diseases, recurrent ovarian cysts, excessive uterine bleeding, and cancer of the cervix, uterus, or ovaries.

Vagina

The vagina is a tubular, long fibromuscular canal lined with mucous membrane that extends from the exterior of the body to the uterine cervix.

It is the receptacle for the penis during sexual intercourse, the outlet for menstrual flow, and the passageway for childbirth.

Vagina

It has an acidic environment that retards microbial growth, but is also harmful to sperm.

Hymen – a thin fold of vascularized mucous membrane closes the inferior end of the vaginal opening to the exterior (vaginal oriface).

Imperforate hymen – sometimes the hymen completely covers the oriface. Surgery may need to be performed to permit the discharge of menstrual flow.

Vulva

Vulvu or pudendum refer to the external genitals of the female.

Vulva Components

Mons pubis – elevation of adipose tissue covered by skin and coarse pubic hair that cushions the pubic symphysis.

Labia majora. Labia minora. Clitoris – a cylindrical mass of erectile tissue and

nerves. Prepuce of the clitoris.

Vulva Components

Vestibule. Vaginal oriface. External urethral oriface. Paraurethral (Skene’s) glands – mucous

secreting glands. Greater vestibular (Bartholin’s) glands –

mucous secreting glands.

Perineum

The perineum is a diamond-shaped area medial to the thighs and bottocks of both males and females,

It contains the external genitals and anus. It is bounded on the anterior by the pubic

symphisis, laterally by the ischial tuberosities, and on the posterior by the coccyx.

The anterior urogenital triangle contains the external genitals and the posterior anal triangle contains the anus.

Episiotomy

During childbirth, the emerging fetus stretches the perineal region.

A physician sometimes performs an episiotomy, a perineal cut made with surgical scissors.

Episiotomy

The cut enlarges the vaginal opening to make more room for the fetus to pass.

The straight cut is easier to suture than the jagged tear that may form naturally.

The incisions is closed in layers with a suture that is absorbed. Stitches do not need to be removed.

Mammary Glands

The 2 mammary glands are modified sudoriferous (sweat) glands that produce milk.

Each breast has a nipple with lactiferous ducts where milk emerges.

Mammary Glands

The areola is the area surrounding the nipple and contains sebacous (oil) glands.

The suspensory ligaments of the breast (cooper’s ligaments) support the breast tissue.

The functions of the mammary glands are the synthesis, secretion, and ejection of milk (lactation).

Fibrocystic Disease Of The Breasts

The breasts of females are highly susceptible to cysts and tumors.

Frbrocystic disease is the most common cause of breast lumps in females.

Fibrocystic Disease Of The Breasts

Cysts (fluid filled sacs) develop. Mainly in females between ages 30 and 50

due to excess of estrogens or deficiency of progesterone.

This occurs about a week or so before menstruation begins.