This can be very useful in Anatomy and physiology coursework as well as for students who are preparing for their examinations at the college introductory level.

1. CHAPTER TWENTY-SEVEN
The Reproductive System
27.1 Anatomy & Physiology of the Male Reproductive System
A. Function: manufacture gametes (sperm) and to deliver them to the female reproductive tract, where
fertilization can occur.
B. It consists of gonads (which produce the gametes and hormones), accessory glands and organs (that
secrete fluids into ducts), and perineal structures that form the external genitalia.
1. Scrotum = pouch of skin containing the testis, or gonad of the male.
a. Divided into two scrotal cavities by a scrotal septum marked externally by a raised ridge
called the raphe.
b. Allows testicles to descend outside the body cavity where they can remain cooler and
proper sperm production can occur. Proper sperm production occurs at three degrees
lower than body temperature.
c. Two muscles are associated with the scrotums ability to change size and shape during
temperature changes:
i. Dartos muscle=smooth muscle layer that wrinkles the scrotal sac trapping warm
air.
ii. Cremaster muscle=skeletal muscle layer that pulls testicles close to the body
thus regulating temperature.
2. Testes = paired, oval-shaped gonads of the male located in the scrotum.
a. Descend through the inguinal canal during development.
b. Produce sperm within the seminiferous tubules via spermatagonia and their helper
cells sertoli cells or sustentacular cells. While the interstitial cells produce androgens,
specifically testosterone.
c. Surrounded by two connective tissue layers: the tunica vaginalis (both parietal and
visceral layers) as well as the tunica albuginea = an tough, inner fibrous capsule that
extends internally to divide the testes into 250-300 lobules which each contain one to
four seminiferous tubules (site of sperm production).
d. From the seminiferous tubules of the testis, the sperm is transported via the tubulus
rectus (straight tubule) into the rete testis and then out the efferent ductules into the
epididymis.
e. Testes descend through the abdominal musculature into the scrotal cavity during the 7th
month of development. Cryptorchidism is when 1 or both of the testes fail to descend
out of the abdominal cavity.
f. Spermatogenesis = sperm formation begins during puberty and continues throughout
life.
i. Occurs in the seminiferous tubules of the testes and generally takes 9 weeks.
ii. Requires three steps: 1) mitosis of the spermatogonia followed by 2) one of the
daughter cells undergoing meiosis to form the gametes and 3) differentiation of
immature male gametes into physically mature sperm called spermiogenesis.
a. Mitosis of spermatogonia = each division of a diploid spermatogonium
produces two daughter cells. One is a spermatogonium that remains in
contact with the basal lamina of the tubule, and the other is a primary
spermatocyte that is pushed towards the lumen of the tubule.
b. Meiosis I = as meiosis I begins, each primary spermatocyte contains 46
individual chromosomes. At the end of meiosis I, the daughter cells are
called secondary spermatocytes. Every secondary spermatocyte

2. contains 23 chromosomes, each of which consists of a pair of duplicate
chromatids.
c. Meiosis II = the secondary spermatocytes soon enter meiosis II, which
yields four haploid spermatids, each containing 23 chromosomes. For
each primary spermatocyte that enters meiosis, four spermatids are
produced.
d. Spermiogenesis = the spermatids undergo physical maturation to form
the spermatozoa or sperm, a process which takes approximately 24 days.
i. The head and acrosome form on one end. The head contains the
23 chromosomes and the acrosome contains enzymes essential to
fertilization of the egg.
ii. The neck contains both centrioles of the original spermatid. The
microtubules of the distal centriole are continuous with those of
the mid-piece and tail.
iii. The mid-piece contains the mitochondria arranged in a spiral
around the microtubules. Mitochondrial activity provides the ATP
required to move the tail.
iv. The tail is a flagellum, or whip-like organelle, used to move the
sperm.
iii. Contrast mitosis and meiosis of spermatogenesis:
Characteristic MITOSIS MEIOSIS
Reason for conducting cell
division
Growth, repair, and
maintenance of body cells.
Formation of gametes
(sperm or eggs)
Type of cell undergoing
division
Somatic cells (body cells) Gametes (sex cells)
Number of daughter cells
produced
2 daughter cells formed 4 spermatids
Number of chromosomes in
each daughter cells
46 (dipoid) 23 (haploid)
Comparison of the daughter
cells to the mother cell
Genetically identical Genetically different due to
crossing over and random
fertilization events
3. Epididymis = coiled tube approximately twenty feet long consisting of a head, body, and tail
region. Located on the posterior, lateral side of the testicle.
a. Stores non-motile sperm for about twenty days as it matures to a swimming sperm.
b. The pseudostratified columnar epithelia lining the epididymis have numerous stereocilia
(non-motile microvilli) which absorb excess fluid and secrete nutrients to the sperm.
4. Ductus Deferens = also called the vas deferens
a. Transports sperm out of the epididymis and towards the urethra.
b. As part of the spermatic cord, the vas deferens, the blood vessels, nerves, and
lymphatic vessels to/from the testes extends through the inguinal canal, into the pelvic
cavity, then up, over and behind the bladder.
c. Contraction of the smooth muscle propels sperm from the epididymis, through the vas
deferens, and towards the urethra.
d. Ampulla=the terminal end of the ductus deferens that is somewhat enlarged.
e. Just before the sperm is deposited into the urethra, the vas deferens joins the duct from
the seminal vesicle to form the ejaculatory duct.

3. f. Each ejaculatory duct penetrates through the prostate gland where it drains sperm and
secretions from the seminal vesicle into the urethra.
g. A vasectomy is done for sterilization purposes. This procedure cuts, ties, and cauterizes
the vas deferens.
5. Accessory structures (glands)
a. Seminal vesicles = paired glands located posterior to the bladder.
i. Produces a viscous, alkaline secretion containing fructose, prostaglandins, and
clotting factors.
ii. Contributes 60% of the volume of semen.
iii. When sperm mix with the fluids of the seminal vesicles they undergo the first
step of capacitation and begin beating their flagella, becoming motile sperm.
b. Prostate gland = a small, single gland located at the base of the bladder.
i. In addition to several other compounds of uncertain significance, prostate
secretions contain seminalplasmin, an antibiotic protein that may help prevent
urinary tract infections in males.
ii. Accounts for about 20% - 30% of semen volume.
c. Bulbourethral glands (Cowper’s glands) = paired glands located at the bulb of the penis
producing a thick, alkaline fluid that lubricates the tip of the penis and neutralizes the
urinary acids.
6. Urethra = part of the urinary and reproductive system.
a. Transports both urine and semen to the exterior (at different times).
b. Extends from the bladder to the tip of the penis and is divided into three regions:
i. Prostatic urethra=portion surrounded by the prostate gland
ii. Membranous urethra=the portion that passes through the urogenital diaphragm
iii. Spongy (penile) urethra=portion that runs through the penis and opens to the
outside of the body through the external urethral orifice (75% of urethral
length).
7. Penis = male copulatory organ and along with the scrotum constitute the males external
genitalia.
a. Consists of the root (bulb and crus/crura of penis), body (or shaft) and the glans penis
(or head). The glans penis is attached to the shaft at the narrow neck.
b. Covering the glans penis is the prepuce, or foreskin, which is often removed by a minor
surgical procedure called circumcision.
c. The penis consists of erectile tissue that contains many vascular spaces that fill with
blood during sexual arousal causing the tissue to become engorged and rigid.
d. The crura consists of three masses of erectile tissue:
i. Corpus spongiosum = the mid-ventral erectile body that surrounds the urethra
and forms the glans penis.
ii. Corpora cavernosa = paired masses of dorsal erectile tissue that makes up most
of the penis and extend to the neck.
Physiology of the Male Reproductive System
A. Arousal = enlargement and stiffening of the penis results from engorgement of the erectile bodies with
blood.
1. Arterioles supplying blood to the penis are usually constricted resulting in a flaccid penis.
2. Stimulation triggers a parasympathetic reflexes that promotes the release of nitric oxide. The
NO relaxes the smooth muscles allowing the blood vessels of the penis to dilate.
3. Expansion of the corpus cavernosa compresses on drainage veins which prevent blood from
draining away. Hence an erection is achieved.

4. 4. Parasympathetic impulses also cause the bulbourethral gland to release their secretions before
ejaculation occurs to lubricate the urethra and tip of the penis.
5. Impotence = a male is unable to achieve or maintain an erection.
B. Emission = propulsion of semen from the male duct system as a result of a spinal reflex.
1. Further stimulation leads to the sympathetic activation that causes emission.
2. Peristaltic contractions of the vas deferens propel sperm towards the urethra within the
prostate gland.
3. The seminal glands and prostate gland begin contracting and their secretions mix with the
sperm to form semen.
4. The bladder sphincter muscle constricts preventing the expulsion of urine.
C. Ejaculation = a powerful series of rhythmic contraction that causes the semen to be ejected from the
body.
1. The muscles of the penis undergo rapid rhythmic contractions propelling semen at a high rate
of speed (200 inches per second).
2. The entire ejaculatory event is referred to as climax or orgasm.
D. Semen Analysis
1. Alkalinity=7.2 to 7.6
2. Normal discharge=2-5 ml per ejaculation
3. Sperm count is roughly 50 to 130 million per ml of ejaculate.
4. Morphology= <35% are abnormal
5. Motility= 60% exhibit forward motility
6. Survival=can live 48 hours after ejaculation
7. Sterility=less than 20 million sperm/ml
27.2 Female Reproductive System
A. Function: Produce gametes (egg or ova) as well as nurture and protect the developing embryo.
B. Also consists of gonads, ducts, and mammary glands:
1. Ovaries = paired, almond-shaped gonads of the female located on each side of the uterus and
held in place by the ovarian ligament, suspensory ligament, and broad ligament.
a. The ovaries produce immature female gametes called oocytes that mature to form the
ovum. The ovaries also produce female sex hormones: estrogen, progesterone, and
inhibin.
b. Covered by two tissue layers:
i. Tunica albuginea=fibrous connective tissue closest to the ovary.
ii. Germinal epithelium=cuboidal cells that are continuous with the parietal
peritoneum.
c. Composed of many tiny saclike structures called ovarian follicles that each consists of an
immature egg called an oocyte.
2. Uterine Tubes = also called the oviducts or fallopian tubes.
a. Transport ova from the ovaries to the uterus.
b. The ampulla terminates in funnel-shaped structure called the infundibulum, which
serves as the normal site of fertilization of the egg.
c. Fimbriae are finger-like projections which possess many cilia and are located at the ends
of the uterine tubes and partially surround the ovary to receive the egg during
ovulation.
d. Takes 3 days for the egg to travel the length of the tube.
e. As the egg reaches the end of the tube it must pass through a narrowed region called
the isthmus.

5. 3. Uterus = also called the womb; a pear-shaped muscular structure located superior to the
bladder.
a. Consists of three regions:
i. Fundus = a rounded upper region
ii. Body = the major portion of the uterus
iii. Cervix = narrow neck and mouth of the uterus; possesses a cervical canal that is
connected on both ends to the cervical os.
b. Uterine wall is also composed of three layers
i. Endometrium=thick innermost mucus lining where the fertilized egg will
penetrate.
ii. Myometrium=muscular middle layer; composed of smooth muscle.
iii. Perimetrium=outermost serous layer.
c. The endometrium has two chief strata
i. Stratum functionalis, or the functional zone; spiral arteries deliver nutrient rich
blood to this zone.
ii. Stratum basalis, or basilar zone; forms a new functional layer each month.
straight arteries deliver blood to the basilar zone.
4. Vagina = a thin-walled, muscular tube extending from the cervix to the vestibule.
a. Serves to receive the penis and semen during sexual intercourse.
b. Also functions as the birth canal and passageway for menses.
c. In a relaxed state, the vagina possesses numerous rugae and is lined with
stratified squamous epithelium.
d. The upper portion of the vagina surrounds the cervix creating an anterior and
posterior fornix.
e. An incomplete partition called the hymen is located at the distal end of the
vaginal orifice and can be ruptured during coitus (sexual intercourse), use of
tampons, athletic activities, etc.
5. External Genitalia = also called the vulva or pudendum.
a. Mons pubis = rounded ridge over the pubic bone wear pubic hair develops.
b. Labia majora = hair covered skin folds.
c. Labia minora = inner, somewhat smaller, hair-less skin folds.
d. Clitoris = a small, protruding structure that is homologous to the penis in males and
possesses erectile tissues. A fold of skin encircling the clitoris is the prepuce.
e. Vestibular glands = homologous to the bulbourethral glands of the male.
f. Perineum = soft tissue between the vaginal region and the anus that can be cut during
childbirth in a procedure called an episiotomy.
6. Mammary Glands = modified sweat glands present in both sexes but functional only in females
in response to prolactin. The production of milk is called lactation.
a. Secretory alveoli secrete the milk and cluster together to form lobules.
b. Each lobe drained by a lactiferous duct, dilating to form a lactiferous sinus.
c. On each side, the mammary gland lies in the subcutaneous tissue of the pectoral fat pad
deep to the skin of the chest.
d. Areolar is the pigmented portion of the breast with a protruding nipple.
Physiology of the Female Reproductive System
A. Oogenesis = production of eggs or ova which occurs before birth, is completed only if the egg becomes
fertilized by sperm. Meiosis begins before a woman’s birth, accelerates at puberty, and ends at
menopause.

6. 1. Mitosis of Oogonia = unlike spermatogenesis in males, oogonia complete their mitotic divisions
before birth.
2. Meiosis I = between the third and seventh months of fetal development, the daughter cells, or
primary oocytes prepare to undergo meiosis. They precede as far as Prophase I but then the
process is halted. The primary oocytes remain in a state of suspension until the individual
reaches puberty, when rising levels of FSH trigger the start of the ovarian cycle. Each month
thereafter, some of the primary oocytes are stimulated to undergo further development.
Meiosis I is then completed, yielding a secondary oocyte and a polar body.
3. Once a month, a secondary oocyte is ovulated into the fallopian tube. The secondary oocyte is
suspended in metaphase II and will not finish meiosis unless fertilization occurs.
4. Meiosis II is completed if and only if fertilization occurs!
5. Polar bodies degenerate and die.
B. The Ovarian Cycle = divided into two phases separated by ovulation
1. Follicular phase
a. Day 1-13 = follicle growth
b. The primordial follicles (simple squamous shaped cells) containing the primary
oocytes are activated forming primary follicles (simple cuboidal cells called
granulosa cells surrounded by thecal cells).
c. The granulosa cells and thecal cells begin to secrete estrogen.
d. The granulosa cells also secrete a glycoprotein that forms a transparent membrane
around the oocyte called the zona pellucida.
e. The follicle now thickens forming a secondary follicle (composed of stratified
cuboidal) and a fluid-filled cavity, called the antrum begins to form.
f. As the antrum continues to expand, the granulosa cells become isolated on a stalk
forming the corona radiata around the oocyte. This now distinguishes the structure
as a Graafian follicle (or vesicular follicle).
2. Ovulation
a. Day 14 = follicle growth and ovulation
b. The antrum swells causing the ballooning ovary wall to rupture and expel the secondary
oocyte and its corona radiata.
c. In 1-2% of all ovulations, more than one oocyte is ovulated.
d. Ovulation marks the end of the follicular phase and the beginning of the luteal phase.
3. Luteal phase
a. Day 15-28 = formation of corpus luteum from granulosa and thecal cells.
b. After ovulation, the ruptured follicle collapses and the antrum fills with clotted blood
forming the corpus luteum which now begins to secrete progesterone and estrogen.
c. If fertilization does not occur, the corpus luteum continues to degenerate to form the
corpus albicans, or scar tissue.
C. The Uterine Cycle
1. Menstrual Phase (or Menses)
a. Approximately day 1 - 5
b. The uterine cycle begins with the onset of menses, an interval marked by the
degeneration of the functional zone of the endometrium. This degeneration is caused
by constriction of the spiral arteries, which reduces endometrial blood flow.
c. Eventually, the weakened arterial walls rupture, and blood pours into the connective
tissues of the functional zone. Blood cells and degenerating tissues then break away
and enter the uterine cavity, to be lost by passage through the external cervical os and
into the vagina.
d. The process of endometrial sloughing is called menstruation.

7. 2. Pre-Ovulatory Phase (also called proliferative phase)
a. Approximately day 6 - 14
b. The basilar zone and the deepest uterine glands survive menses. The epithelial cells of
the uterine glands then multiply and spread across the endometrial surface.
c. Spiral arteries begin to develop and penetrate through the new functional zone of the
endometrium (angiogenesis).
d. Restoration of the functional zone of the endometrium is stimulated and sustained by
estrogens secreted by the ovarian follicles.
e. Ovulation occurs on day 14 due to LH surges.
3. Post-Ovulatory Phase (also called secretory phase)
a. Approximately day 15-28
b. The uterine glands begin to secrete nutritious glycogen-rich mucus into the uterine
cavity to sustain the blastocyst until implantation has occurred.
c. Secretion and preparatory changes in the endometrium occurs in response to rising
progesterone fromthe corpus luteum in expectation of a potential embryo.
d. Meanwhile, mucus secreted by the cervix becomes viscous creating a cervical plug.
e. The secretory phase begins at ovulation and persists as long as the corpus luteum
remains intact. When the corpus luteum stops producing stimulatory hormones, a new
uterine cycle begins with the onset of the next menses.
4. Menopause
a. Cessation of menstruation also known as menarche. Occurs 45-55 years of age.
b. Ovaries fail to respond to FSH and estrogen levels decline. Number of remaining
follicles decrease. Regression of organs often occurs. Hot flashes and mood swings
common due to hormonal imbalances.
D. Hormones
1. GnRH = gonadotropin releasing hormone, stimulates the production and secretion of FSH
2. FSH = follicle stimulating hormone; stimulates maturation of the ovarian follicles and the
production of estrogen
3. LH = luteinizing hormone; stimulates ovulation of the oocyte and secretion of progesterone
4. Progesterone = stimulates thickening and vascularization of the endometrium and secretion of
nutrient rich fluids from the uterine glands
5. Estrogen = establishment and maintenance of the female secondary sex characteristics and
initiates the repair and regeneration of the endometrium
27.3 Development of the Male and Female Reproductive Systems
A. Development of sexual organs in the embryo
Both male and female embryo’s sexual organs grow from the same tissue. The ability of certain
tissue to change into male of female is also known as bipotential. All eggs would develop into
females without the addition of the gene found in the (SRY) sex determining region of the Y
chromosome. With the SRY different genes become activated and the testes begin to develop.
Without the SRY oogonia and follicles form within the ovary. Once the testes are formed leydig
cells begin to secrete testosterone which stimulates male external genitalia of the glans penis.
Without testosterone the clitoris begins formation. Other reproductive structures are not
bipotential and are formed from embryological duct systems.
B. Further sexual development occurs at puberty
1. Hormones: At around age 8 the hormone cascade of puberty begins. GnRH from the
hypothalamus stimulates the pituitary to release LH and FSH and gonadal release of estrogen or
testosterone. Pre-pubescent children are very sensitive to negative feedback systemof
reproductive hormones. As children reach puberty the negative feedback sensitivity partially

8. declines and the reproductive organs become more sensitive to the effects of the hormones.
This leads to the maturity of the gonads, higher levels of hormones and spermatogenesis or
folliculogenesis. Multiple factors can influence onset of puberty such as genetics, environment,
psychological stress as well as nutrition. Fat stores may also be linked to menarche.
2. Signs of Puberty
a. Female – development of breast tissue, widening of pelvis, growth of axillary and pubic
hair. Growth spurt of up to 3” per year from the ages of 9-11. First menstruation around
age 13.
b. Male – increased muscular development, increased larynx/vocal cords for deeper voice,
increased growth of axillary, facial, pubic and body hair. Growth spurt of up to 4” per
year from ages 11-13 with continued development into early 20s. First fertile ejaculation
around age 15.
27.4 Homeostatic Imbalances
A. Testicular cancer = common in young men ages 15 – 35; rate is approximately 3 in 100,000
males per year. Survival rates are at 95%.
B. Hypertrophy of the prostate gland = enlargement of the prostate gland which leads to anuria
or impotence. Prostate cancer is a malignancy of the prostate gland and is the second most
common cancer and second most common cause of cancer deaths in males.
C. Pelvic inflammatory disease (PID) = bacterial infection resulting in inflammation
D. Breast cancer = if inflamed lobules become walled off by scar tissue, cysts are created. Clusters
of cysts are known as fibrocystic disease. Breast cancer is a malignant, metastasizing tumor of
the mammary glands and is the leading cause of death in women age 35 – 45.
E. Ovarian cancer = 1 in 70 women will develop ovarian cancer; causes 14,600 deaths per year.
F. Cervical cancer = most common reproductive cancer in women age 15-34 especially in case
where there is a history of sexually transmitted diseases. 70% of cervical cancers are linked to
HPV, the human papillomaviruses.
G. Sexually transmitted diseases=gonorrhea, syphilis, Chlamydia, genital warts, genital herpes, etc
H. Amenorrhea = cessation of menses
I. Dysmenorrhea = painful menstruation
J. Endometriosis = over production of endometrium
K. Cryptorchidism = failure of testes to descend into the scrotum