28-1 Chapter 28 - THE REPRODUCTIVE SYSTEM

(figures relate to Tortora/Grabowski 9^th edition of Principles of Anatomy and Physiology)

I. INTRODUCTION

A. Sexual reproduction - producing offspring by means of germ cells called gametes.

B. Gonads produce gametes and secrete hormones.

C. Gynecology is the specialized branch of medicine concerned with the diagnosis and treatment of diseases of
the female reproductive system. Urology is the study of the urinary system but also includes diagnosis and
treatment of diseases and disorders of the male reproductive system.

II. THE CELL CYCLE IN THE GONADS

A. The cell cycle in the gonads produces gametes by a special type of nuclear division called meiosis, that
reduces the number of chromosomes by one half, (from 2n to n)

B. Chromosomes in Gametes

1. A gamete has only 23 chromosomes, one member of each chromosome pair.

2. The two chromosomes that make up a chromosome pair are called homologous chromosomes or
homologs.

a. They contain similar genes, are arranged in the same order, and look very similar.

b. The exception is die sex chromosomes. The female contains two X chromosomes; and the
male, an X and a Y chromosome (Y being much smaller than X).

c. The other 22 pairs of chromosomes are called autosomes.

3. A cell with a full set of chromosomes is called a diploid cell (2n). A cell with only one chromosome
from each pair is termed haploid (n).

C. Meiosis (Figure 28.1).

1. Meiosis results in the production of haploid cells that contain only 23 chromosomes.

a. Meiosis I consists of four phases: prophase I, metaphase 1, anaphase I, and telophase 1.

1) During prophase I, the chromosomes become arranged in homologous pairs.

2) During metaphase I, the homologous pairs of chromosomes line up along the
metaphase plate of the cell, with the homologous chromosomes side by side.

3) During anaphase I, the members of each homologous pair separate, with one member
of each pair moving to an opposite pole of the cell.

4) Telophase I and cytokinesis are similar to telophase and cytokinesis of mitosis.

b. During prophase L the two chromatids of each pair of homologous chromosomes pair off, an
event called synopsis. The resulting four chromatids form a tetrad. Portions of one chromatid
may be exchanged with portions of another (Figure 28.2), an event called crossing-over.

1) This process permits an exchange of genes among homologous chromosomes.

2) It results in genetic recombination, the formation of new combinations of genes.

c. Meiosis II consists of prophase II, metaphase II, anaphase II, and telophase II.

d. These phases are similar to those in mitosis, but result in four haploid cells.

28-2

III. MALE REPRODUCTIVE SYSTEM

A. The male structures of reproduction include the testes, a system of ducts (ductus epididymis, ductus deferens,
ejaculatory duct, urethra), accessory sex glands (seminal vesicles, prostate gland, bulbourethral glands), and
several supporting structures, including the penis (Figure 28.3).

B. Scrotum

1. The scrotum is a cutaneous outpouching of the abdomen that supports the testes; internally, a vertical
septum divides it into two sacs, each containing a single testis (Figures 28.3, 28.4).

2. The reproduction and survival of spermatozoa require a temperature that is lower than normal core
body temperature by a few degrees, thus, the function of the scrotum.

C. Testes

1. The testes, or testicles, are paired oval-shaped glands (gonads) in the scrotum (Figure 28.5).

a. The testes develop high on the embryo's posterior abdominal wall and usually begin their
descent into the scrotum through me inguinal canals during the latter half of the seventh
month of fetal development.

b. The testes contain seminiferous tubules (in which sperm cells are made).

c. Embedded among the spermatogenic cells in the tubules are large Sertoli cells or
sustentacular cells (nurse cells).

1) They nourish spermatocytes, spermatids, and spermatozoa; mediate the effects of testosterone and FSH on spermatogenesis; control movements of spermatogenic cells and the release of spermatozoa into the lumen of the seminiferous tubule; and secrete fluid for sperm transport.

d. The Leydig cells or interstitial endocrinocytes found in the spaces between adjacent
seminiferous tubules secrete testosterone (Figure 28.6).

e. Failure of the testes to descend is called cryptorchidism, involving one or both testes.
(Clinical Application)

2. Spermatogenesis - process by which the seminiferous tubules of the testes produce haploid sperm.

3. Mature sperm consist of a head, midpiece, and tail (Figure 28.8). Produced at the rate of about 300
million per day. Once ejaculated, life expectancy is 48 hours within the female reproductive tract.

4. Hormonal Control of spermatogenesis (Figure 28.9)

a. At puberty, gonadotropin releasing hormone stimulates anterior pituitary secretion of
follicle-stimulating hormone (FSH) and luteinizing hormone (LH). FHS initiates
spermatogenesis, and LH assists spermatogenesis and stimulates production of testosterone.

b. Testosterone controls the growth, development, functioning, and maintenance of sex organs;
stimulates bone growth, protein anabolism, and sperm maturation; and stimulates
development of male secondary sex characteristics. (Figure 28.10).

D. Ducts

28-3

1. The duct system of the testes includes the seminiferous tubules, straight tubules, and rete testis.

2. Epididymis (Figures 28.1,28.3)

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

b. The ductus epididymis - site of sperm maturation and storage; sperm may remain in storage
here for at least a month, after which they are either expelled or degenerated and reabsorbed.

3. Ductus (Vas) Deferens (Figures 28.1, 28.2, 28.3)

a. Also called seminal duct, stores sperm and propels them toward the urethra during ejaculation

4. The ejaculatory ducts are formed by the union of the ducts from the seminal vesicles and ducti
deferens; their function is to eject spermatozoa into the prostatic urethra (Figure 28.11).

5. The male urethra is the shared terminal duct of the reproductive and urinary systems which serves as
a passageway for semen and urine. (Figures 28.1, 28.11).

E. Accessory Sex Glands

1. The seminal vesicles secrete an alkaline, viscous fluid that contains fructose, prostaglandins, and
clotting proteins.

a. The alkalinity helps to neutralize acid in the male urethra and female reproductive tract.

b. The fructose is for ATP production by sperm.

c. Prostaglandins contribute to sperm motility, viability, and stimulate vaginal contractions.

2. The prostate gland secretes a milky, slightly acidic fluid that contains: (1) citric acid, which can be
used by sperm for ATP production; (2) acid phosphatase; and (3) several proteolytic enzymes

3. The bulbourethral (Cowper’s) glands secrete mucus (lubrication) and an alkaline substance that
neutralizes acid.

F. Semen (seminal fluid) is a mixture of spermatozoa and accessory sex gland secretions - provides the fluid in
which spermatozoa are transported and nourished; and neutralizes acidity of male urethra and female vagina.

G. Penis

1. The penis is the male organ of copulation that consists of a root, body, and glans penis. It is used to
introduce spermatozoa into the vagina (Figure 28.12).

2. Expansion of its blood sinuses under the influence of sexual excitation (parasympathetic response) is
called erection

3. Ejaculation, propulsion of semen from the urethra to the exterior, is a sympathetic reflex.

4. Covering the glans penis is the loosely fitting prepuce, or foreskin. Circumcision is a surgical
procedure in which part or all of the prepuce is removed (for either religious or hygienic reasons).
There is no consensus among physicians regarding the need for circumcision or the use of anesthesia
during the procedure.

IV. FEMALE REPRODUCTION SYSTEM

A. The female organs of reproduction include the ovaries (gonads), uterine (Fallopian) tubes, uterus, vagina, vulva, and mammary glands (Figure 28.13).

28-4

B. Ovaries

1. The ovaries are paired glands that are homologous to the testes.

2. The ovaries are located in the upper pelvic cavity, on either side of the uterus. (Figure 28.14).

3. The histology of the ovary is illustrated in Figure 28.15.

a. Ovarian follicles lie in the cortex and consist of oocytes in various stages of development.

b. A mature (Graafian) follicle expels a secondary oocyte by a process called ovulation (14d).

c. A corpus luteum contains the remnants of an ovulated follicle and produces progesterone,
estrogens, and relaxin until it degenerates.

4. Oogenesis (occurs in the ovaries)

a. Oogenesis results in the formation of a single haploid secondary oocyte (egg).

C. Uterine Tube (Figure 28.18)

1. The uterine (Fallopian) tubes transport ova from the ovaries to the uterus - normal site of fertilization

2. If implantation occurs here, it's called an ectopic pregnancy and cannot survive.

D. Uterus

1. The uterus (womb) is an organ the size and shape of an inverted pear that functions in the transport of
spermatozoa, menstruation, implantation of a fertilized ovum, development of a fetus during
pregnancy, and labor.

2. Anatomical subdivisions of the uterus include the fundus, body, isthmus, and cervix.

3. Histologically, the uterus consists of an outer perimetrium, middle myometrium, and inner
endometrium (Figure 28.20).

4. Secretory cells of the mucosa of the cervix produce a cervical mucus (a mixture of water,
glycoprotein, serum-type proteins, lipids, enzymes, and inorganic salts).

a. The cervical mucus supplements the energy needs of the sperm.

b. Both the cervix and the mucus serve as a sperm reservoir, protect sperm from the hostile
environment of the vagina, and protect sperm from phagocytes.

5. Hysterectomy refers to surgical removal of the uterus and is the most common gynecological
operation. (Clinical Application)

E. Vagina

1. The vagina functions as a passageway for spermatozoa and the menstrual flow, the receptacle of the
penis during sexual intercourse, and the lower portion of the birth canal (Figures 28.13, 28.18).

2. The mucosa of the vagina is continuous with that of the uterus.

a. Mucosa dendritic cells are APCs (antigen-presenting cells) that participate in the transmission of viruses, such as HTV, to a female during intercourse with an infected male.

28-5

b. The mucosa contains large stores of glycogen which decompose into organic acids which set

up a hostile acid environment for sperm. Alkaline components of semen neutralize the acidity

and increase sperm viability.

3. The vaginal orifice is often partially covered by a thin fold of vascularized mucous membrane called the hymen. If the orifice is completely covered, this imperforate hymen must be surgically opened to permit menstrual flow (Figure 28.22).

F. Vulva

1. The term vulva, refers to the external genitalia of the female (Figure 28.22).

2. It consists of the mons pubs, labia majora. labia minora, clitoris, vestibule, vaginal and urethra!
orifices, hymen, bulb of the vestibule, and the paraurethral (Skene's), greater vestibular (Bartholin's),
and lesser vestibular glands (Figure 28.23).

3. Table 28.1 summarizes the homologous structures of the male and female reproductive systems.

G. The perineum is the diamond-shaped area between the thighs and buttocks of both males and females that
contains the external genitals and anus (Figure 2823).

H. Mammary Glands (modified sudoriferous, sweat, glands)

1. Milk-secreting cells are the alveoli.

2. Essential function - lactation = synthesis of milk (does not occur during pregnancy because it
requires PROLACITN, produced after birth); secretion and ejection of milk (suckling stimulates
nerve impulses in areola to cause release of oxytocin).

3. Colostrum - higher in protein, lower in fat content; source of PASSIVE IMMUNITY
(Antibodies that pass from mother to child); yellowish fluid exuding from mother
prior to lactation.

V. FEMALE REPRODUCTIVE CYCLE

A. The general term female reproductive cycle encompasses the ovarian and uterine cycles

1. The ovarian cycle is a series of events associated with the maturation of an ovum.

2. The uterine (menstrual) cycle involves changes in the endometrium to prepare for the reception of a
fertilized ovum.

B. Hormonal Regulation of the Female Reproductive Cycle (we did a lot of this during endocrine)

1. The menstrual and ovarian cycles are controlled by GnRH from the hypothalamus, which stimulates
the release of FSH and LH by the anterior pituitary gland (Figure 28.25).

2. Progesterone works with estrogens to prepare the endometrium for implantation and the mammary
glands for milk synthesis.

3. A small quantity of relaxin is produced monthly to relax die uterus by inhibiting contractions (making
it easier for a fertilized ovum to implant in the uterus). During pregnancy, relaxin relaxes the pubic
symphysis and helps dilate the uterine cervix to facilitate delivery.

C. Phases of the Female Reproductive Cycle

28-6

1. The female reproductive cycle may be divided into three phases (Figure 28.26).

a. The menstrual cycle (menstruation) lasts for approximately the first 5 days of the cycle.

1) Small secondary follicles in each ovary begin to develop.

2) Stratum functionalis layer of the endometrium is shed, discharging blood, tissue
fluid, mucus, and epithelial cells.

b. The preovulatory phase, or proliferative phase, is the time between menstruation and
ovulation, lasting from days 6-13 in a 28-day cycle.

1) A single secondary follicle (occasionally more than one) develops into a vesicular
ovarian (Graafian) follicle, or mature follicle. This follicle produces a bulge on the
surface of the ovary (Figure 28.15).

2) The dominant follicle continues to increase its estrogen production under the
influence of an increasing level of LH (Figure 28.27).

3) During this phase, endometrial repair occurs.

c. Ovulation is the rupture of the vesicular ovarian (Graafian) follicle with release of the
secondary oocyte into the pelvic cavity, usually occurring on day 14 in a 28-day cycle.

1) The high levels of estrogen during the last part of the preovulatory phase exert a
positive feedback on both LH and GnRH to cause ovulation (Figure 28.28).

a) GnRH promotes release of FHS and more LH by the anterior pituitary gland.

b) The LH surge brings about the ovulation.

2) Following ovulation, the follicular cells enlarge, change character, and form the
corpus luteum, or yellow body, under the influence of LH. Stimulated by LH, the
corpus luteum secretes estrogens and progesterone.

d. The postovulatory phase is the most constant in duration and lasts from days 15-28 in a 28-
day cycle, the time between ovulation and onset of the next menstrual period.

1) With reference to the ovaries, this phase of the cycle is also called the luteal phase, during which both estrogen and progesterone are secreted in large quantities by the corpus luteum.

a) If fertilization and implantation do not occur, the corpus luteum degenerates.
The decreased secretion of progesterone and estrogens then initiates another
menstrual phase (uterine and ovarian cycle).

b) If fertilization and implantation do occur, the corpus luteum is maintained
until the placenta takes over its hormone-producing function. During this
time, the corpus luteum, secretes estrogens and progesterone to support
pregnancy and breast development for lactation. Once the placenta begins its
secretion, the role of the corpus luteum becomes minor.

28-7

2) With reference to the uterus, this phase is also called the secretory phase because of

the secretory activity of the endometrial glands as the endometrium thickens in anticipation of implantation.

2. Menstrual abnormalities include amenorrhea (absence of menstruation), dysmenorrhea (pain

associated with menstruation), and abnormal uterine bleeding. (Clinical Application) VI. BIRTH CONTROL METHODS

A. Several methods of birth control are available, each with advantages and disadvantages.

B. The only method of preventing pregnancy that is 100% reliable is total abstinence.

C. Methods of birth control discussed in the text include surgical sterilization (vasectomy, tubal ligation),
hormonal methods (oral contraception, the Norplant implant, depo-provera injection, the vaginal ring),
intrauterine devices (IUDs), spermacides, barrier methods (condom, vaginal pouch, diaphragm, cervical cap),
periodic abstinence (rhythm method, sympto-thermal method), coitus interruptus (withdrawal), and induced
abortion (including die drug RU 486, or mifepristone).

D. A summary of methods of birth control is presented in Table 28.2.
VII. AGING AND THE REPRODUCTIVE SYSTEMS

A. In females, the reproductive cycle normally occurs once each month from menarche, the first menses, to
menopause, the last menses.

1. Between the ages of 40 and 50 the ovaries become less responsive to the stimulation of gonadotropic
hormones from the anterior pituitary. As a result, estrogen and progesterone production decline, and
follicles do not undergo normal development.

2. In addition to the symptoms of menopause, such as hot flashes, copious sweating, headache, vaginal
dryness, depression, weight gain, and emotional fluctuations, with age females also experience
increased incidence of osteoporosis, uterine cancer, and breast cancer.

B. In males, declining reproduction function is more subtle, with males often retaining reproductive capacity into
their 80s or 90s.

1. In males, decreasing levels of testosterone decrease muscle strength, sexual desire, and viable sperm,

2. Prostate disorders are increasingly common with age, particularly benign hypertrophy.

3. Erectile dysfunction, previously termed impotence, is the consistent inability of an adult male to
ejaculate or to attain or hold an erection long enough for sexual intercourse. (Clinical Application).

VIII. DISORDERS: HOMEOSTATIC IMBALANCES

A. Sexually transmitted diseases (STDs) are disease spread by sexual contact and include chlamydia, gonorrhea, syphilis, and genital herpes.

1. Chlamydia is a STD caused by the bacterium Chlamydia trachomatis. At present chlamydia is the most prevalent and one of the most damaging of the STDs.

a. In most cases, the initial infection is asymptomatic and difficult to recognize clinically.

28-8

b. In males, urethritis is the principal result. In females, urethritis may spread through the

reproductive tract and develop into inflammation of the uterine tubes, which increases the risk of ectopic pregnancy and sterility.

2. Gonorrhea ("clap") is an infectious STD that affects primarily the mucous membrane of the
urogenital tract, the rectum, and occasionally the eyes. The disease is caused by the bacterium
Neisseria gonorrhoreae.

a. Males usually suffer inflammation of the urethra with pus and painful urination.

b. In females, infection may occur in the urethra, vagina, and cervix, and there may be a
discharge of pus. However, infected females often harbor the disease without any symptoms
until it has progressed to a more advanced stage. If die uterine tubes become involved, pelvic
inflammation may follow, often causing sterility and occasionally causing peritonitis.

c. If the bacteria are transmitted to the eyes of a newborn in the birth canal, blindness can result.
Administration of a 1% silver nitrate solution or penicillin or erythromycin in the neonate's
eyes prevents infection.

3. Syphilis is an STD caused by the bacterium Treponema pallidum.

a. It is acquired through sexual contact, exchange of blood, or transmitted through the placenta to a fetus.

1) Primary stage: a painless open sore, called a chanker.

2) Secondary stage: skin rash, fever, and aches in the joints (systemic infection).

3) The tertiary stage occurs when signs of organ degeneration appear.

4. Genital herpes is an incurable STD caused by the type n herpes simplex virus (HSV-2).

a. HSV-2 causes genital infections such as painful blisters on the prepuce, glans penis, and
penile shaft in males and on the vulva or sometimes high up in the vagina in females.

b. The blisters disappear and reappear in most patients, but the virus itself remains in the body.
B. Male Disorders

1. Testicular cancer originates in die sperm-producing cells.

a. Most common between 15 and 34. All males should perform regular testicular self-exams.

b. An early sign is a mass in the testis, often associated with pain or discomfort.

2. Prostate Disorders

a. Acute prostatitis, the prostate gland becomes swollen and tender.

b. Chronic prostatitis, one of the most common chronic infections in men of the middle and
later years, the gland feels enlarged, soft, and very tender with an irregular surface outline.

c. Prostate cancer is the leading cause of cancer deaths in men in the United States.

1) A blood test can measure the level of prostate-specific antigen (PSA) in the blood.

2) The amount of PSA increases with the enlargement of the prostate gland and may
indicate infection, benign enlargement, or prostate cancer.

28-9

3) Treatment for prostate cancer may involve surgery, radiation, hormonal therapy, or

chemotherapy. C. Female Disorders

1. Endometriosis is characterized by the growth of endometrial tissue outside the uterus.

a. The tissue enters the pelvic cavity via the open uterine tubes and may be found in any of
several sites - on ovaries, surface of the uterus, sigmoid colon, pelvic and abdominal lymph
nodes, cervix, abdominal wall, kidneys, and/or urinary bladder.

b. Symptoms include premenstrual pain or unusual menstrual pain.

2. Breast cancer is the second-leading cause of death from cancer in United States women,

a. It is seldom seen before age 30, but its occurrence rises rapidly after menopause.

b. Two genes increase susceptibility to breast cancer: BRCA1 (breast cancer 1) and BRCA2.
Mutation of BRCA1 also confers high risk for ovarian cancer.

c. Early detection - especially by breast self-examination and mammography - is still the most
promising method to increase the survival rate for breast cancer.

d. The factors mat increase the risk of breast cancer development include family history of
breast cancer, especially in a mother or sister, never having a child or having a first child after
age 35; previous cancer in one breast exposure to ionizing radiation, such as x-rays;
excessive alcohol intake; and cigarette smoking.

e. Treatment for breast cancer may involve hormone therapy, chemotherapy, radiation therapy,
lumpectomy, a modified or radical mastectomy, or a combination of these. Radiation
treatment and chemotherapy may follow the surgery.

3. Ovarian cancer is the sixth most common form of cancer in females.

a. It is difficult to detect before it metastasizes beyond the ovaries.

b. Risk factors include age (usually over age 50); race (white are at greatest risk); family history
of ovarian cancer; never having children or first pregnancy after age 30; high-fat, low-fiber,
vitamin A-deficient diet; and prolonged exposure to asbestos or talc.

c. Early ovarian cancer - no symptoms or only mild ones associated with other common problems.

d. Later-stage signs and symptoms include an enlarged abdomen, abdominal and/or pelvic pain,
persistent gastrointestinal disturbances, urinary complications, menstrual irregularities, and
heavy menstrual bleeding.

4. Cervical cancer starts with cervical dysplasia and can be diagnosed early with a Pap smear.

a. Some evidence links cervical cancer to genital warts (papilloma virus).

b. Other risk factors are increased incidence associated with an increased number of sexual
partners, young age at first intercourse, and cigarette smoking.

BIRTH CONTROL METHODS

1. Most reliable = ABSTINENCE

2. Almost 100% effective: Risk:

Vasectomy Sterility

Tubal ligation

Norplant (subcutaneous implant of hormones) Irregular menstrual bleeding

3. About 95% effective: Risk:

Oral contraceptive (BCP) Thromboembolism (smokers esp.),

(protects against ovarian cancer) heart attack, stroke

Intrauterine Device (IUD) - Cu or plastic/progestin Pelvic Inflammatory Disease
Depo-Provera (hormonal injection - 3 mo.) Breast cancer/osteoporosis

Lunelle (1 month injection) None yet

4. About 85% effective: Risk:

Male and Female condom w/out spermicide Unknown

Vaginal sponge with spermicide Diaphragm with spermicidal jelly Spermicidal foams Cervical Cap

5. Less than 75% effective: Risk:

Coitus interruptus Little to none

Jellies, creams, suppositories alone

Rhythm

6. Less than 50% effective: Risk:

Douching Pregnancy

7. RU-486 (mifespristone) / Preven

May be used up to 72 hours after unprotected sex as a contraceptive. RU-486 is more commonly used as an abortion pill up to 7 weeks after implantation. Should only be used under doctor's supervision after careful consideration. **May trigger high blood pressure, blood clots, breast cancer.