The Reproductive System

Male reproductive structures include the

external genitalia and internal genitalia

Reproductive system
▪ Only system not essential to sustaining life
▪ Gonads produce gametes
• Male gametes are sperm
Male reproductive structures

External genitalia
▪ Penis contains erectile tissue, deposits sperm into
vagina of female
▪ Urethra conducts semen to exterior
▪ Scrotum surrounds
testes
Male reproductive structures

Internal genitalia
▪ Ductus deferens conduct sperm between
epididymis and prostate
▪ Seminal gland secretes fluid making up much
volume of semen
Male reproductive structures

Internal genitalia (continued)

▪ Prostate secretes fluid and enzymes
▪ Bulbo-urethral gland secretes fluids that lubricate
tip of penis
▪ Epididymis is the site
of sperm maturation
▪ Testis produces sperm
and hormones
Sperm transport relies on ducts, glands, and
related structures of the scrotum and testes

Path of sperm
▪ Testis to the epididymis, along the ductus
deferens, then along the ejaculatory duct to the
urethra
Main structures of the male reproductive system

Accessory organs secrete various fluids into

the reproductive tract
▪ Seminal glands, prostate, and bulbo-urethral
glands secrete various fluids into ejaculatory duct
and urethra
▪ Urethra passes through the penis to exit the body
Main structures of the male reproductive system

The testes
▪ 5 cm long; 3 cm wide; 2.5 cm thick
▪ Each weighs 10–15 g
Main structures of the male reproductive system

The testes
▪ Form inside the body cavity adjacent to the kidneys
• Connective tissue bands do not elongate as fetus
grows
– Relative position of testes changes as body enlarges
• Late in fetal development, connective tissue band
contracts
– Pulls each testis through abdominal musculature into
the scrotum
Main structures of the male reproductive system

Scrotum and associated structures

▪ Scrotal cavities
• House the testes
• Scrotal septum separates right and left cavities
– Marked by a raised thickening (raphe of scrotum) in
the scrotal surface
▪ Dartos muscle
• Smooth muscle in the skin of the scrotum
• Elevates testes and wrinkles scrotal surface
▪ Cremaster muscle
• Contracts to pull testes closer to body during sexual
arousal or when exposed to cold temperature
Main structures of the male reproductive system

Scrotum and associated structures (continued)

▪ Spermatic cords
• Extend through the inguinal canals between testes
and abdominopelvic cavity
• Each contains layers of fascia and muscle
– Layers enclose the ductus deferens, blood vessels,
nerves, and lymphatic vessels
▪ Superficial inguinal ring
• Entrance to the inguinal canal
Main structures of the male reproductive system

Scrotum and associated structures (continued)

▪ Inguinal canal
• Extends from the inguinal ring to the scrotal cavity
• Presence of spermatic cords creates weak points in
the abdominal wall
– Inguinal hernias
o Protrusions of visceral tissue or organs into the
inguinal canal
o Fairly common in males
Superficial and deeper features of male
reproductive system
Main structures of the male reproductive system

Internal organization of the testes

▪ Tunica vaginalis
• Serous membrane; lines scrotal cavity
• Reduces friction
▪ Tunica albuginea
• Tough, fibrous capsule; covers testis
• Continuous with septa subdividing testes into lobules
Main structures of the male reproductive system

Internal organization of the testes (continued)

▪ Seminiferous tubules
• Coiled tubules within lobules
• Site of sperm production
• Myoid cells contract to transport sperm through tubule
• Rete testis (rete, a net)
– Maze of passageways
– Seminiferous tubules merge into straight tubules then
rete testes
• Efferent ductules
– 15–20 tubes connecting the rete testis to the
epididymis
Internal organization of the testes
Spermatogenesis occurs in the testes and
produces mature sperm

Spermatogenesis (sperm production)

▪ Involves three processes
1. Mitosis and cell division (cytokinesis)
– Process producing two identical daughter cells
– Since daughter cells contain 23 pairs of chromosomes
(or two sets of chromosomes), they are called diploid
– In seminiferous tubules, stem cells undergo mitosis
Mitosis
Sperm formation and structure

Spermatogenesis (continued)
▪ Involves three processes (continued)
2. Meiosis
– Special form of cell division involved in gamete
production
– Two cycles of cell division (meiosis I and II)
– Produces four haploid (haplo, single) cells, each with
23 individual chromosomes
– Synapsis
o Corresponding material and paternal chromosomes
associate to form 23 chromosome pairs
o Set of four chromatids is called a tetrad
Meiosis
Sperm formation and structure

Spermatogenesis (continued)
▪ Involves three processes (continued)
3. Spermiogenesis
– Differentiation of immature male gametes into
physically mature spermatozoa
Sperm formation and structure

Mitosis of spermatogonium
▪ Spermatogonia (singular, spermatogonium)
• Stem cells in the seminiferous tubules
• Go through mitosis to form two daughter cells
– One cell remains in contact with the tubule basement
membrane
– The other is a primary spermatocyte
o 16 days from spermatogonium to primary
spermatocyte
Sperm formation and structure

Process of spermatogenesis (continued)

▪ Meiosis I
• Each primary spermatocyte begins with 46
chromosomes diploid
• Daughter cells produced are called secondary
spermatocytes
– Each contains 23 chromosomes haploid
– Each chromosome has pair of duplicate chromatids
• 24 days from primary spermatocyte to secondary
spermatocyte
Sperm formation and structure

Process of spermatogenesis (continued)

▪ Meiosis II
• Secondary spermatocytes divide to produce
spermatids
– Each spermatid contains 23 chromosomes
– Each primary spermatocyte produces four spermatids
• Only a few hours from secondary spermatocyte to
spermatid
Sperm formation and structure

Process of
spermatogenesis
(continued)
▪ Spermiogenesis
• Physical maturation of sperm
• Each spermatid matures into
a single sperm
• 24 days from spermatid to
sperm
Spermatagonia to sperm
Sperm formation and structure

Structure of a sperm
▪ Specialized to deliver chromosomes to female
gamete
• Lacks most organelles and intracellular structures in
order to reduce size and mass
▪ Acrosome
• Membranous compartment containing enzymes
essential to fertilization
▪ Head
• Contains nucleus with densely packed chromosomes
Sperm formation and structure

Structure of a sperm (continued)

▪ Neck
• Contains both centrioles of the original spermatid
• Microtubules of distal centriole are continuous with
those of the middle piece and tail
▪ Middle piece
• Contains mitochondria to provide ATP for tail
movement
▪ Tail (flagellum)
• Whiplike organelle that moves the sperm
Structure of a sperm
Meiosis and early spermiogenesis occur within
the seminiferous tubules

Seminiferous tubules
▪ Tightly coiled within
lobules
• Often seen in cross
section in micrographs
▪ Sites of
spermatogenesis
Seminiferous tubules

Seminiferous tubules (continued)

▪ Spermatogenesis and spermiogenesis together take
9 weeks
▪ Each segment of seminiferous tubule is at different
phase of spermatogenesis
▪ Surrounded by a delicate connective tissue capsule
Seminiferous tubules

Seminiferous tubules (continued)

▪ Spaces between tubules contain:
• Areolar tissue
• Blood vessels
• Large interstitial endocrine cells (Leydig cells)
– Produce androgens, such as testosterone and
androstenedione (dominant sex hormones in males)
Seminiferous tubules

Cells in the wall of the seminiferous tubule

▪ Spermatogonia (stem cells)
▪ Spermatocytes (undergoing meiosis)
▪ Spermatids (undergoing spermiogenesis)
• Develop into mature sperm
▪ Nurse cells (Sertoli cells)
• Extend from the tubular capsule to the lumen
• Located between other types of cells
– Nurse cell cytoplasm surrounds those other cells
▪ Spermiation
• Process in which a sperm loses attachment to the
nurse cell and enters the tubule lumen
Cells of the seminiferous tubule
Seminiferous tubules

Compartments of the seminiferous tubule

▪ Nurse cells are joined by tight junctions
• Form a blood testis barrier protecting
developing sperm cells from the body’s
immune system
• This layer of nurse cells
divides the seminiferous
tubule into two
compartments
– Basal compartment
o Contains spermatogonia
– Luminal compartment
o Where meiosis and
spermatogenesis occur
The male reproductive tract receives secretions
from the seminal, prostate, and bulbo-urethral
glands
Activation of sperm
▪ Sperm released from testes are physically mature
• But immobile and incapable of fertilizing an oocyte
▪ Other parts of male reproductive system are
responsible for functional maturation, nourishment,
storage, and transport of spermatozoa
Male reproductive tract and glands

Activation of sperm (continued)

▪ Capacitation
• Process enabling sperm to become motile and fully
functional
• Usually occurs in two steps
1. Sperm become motile when mixed with seminal
gland secretions
2. Sperm become capable of fertilization when
exposed to the female reproductive tract
Male reproductive tract and glands

Ampulla
▪ Expanded distal
portion of ductus
deferens
Ejaculatory duct
▪ Carries fluid from
seminal gland and
ampulla to urethra
Male reproductive tract and glands

Epididymis (epi, on, + didymos, twin)

▪ Start of the male reproductive tract
▪ Coiled tube bound to posterior border of each testis
▪ Lined with pseudostratified columnar epithelium
• Has long stereocilia that increase surface area
▪ Sperm undergo functional maturation here
Male reproductive tract and glands

Epididymis (continued)
▪ Regions of the epididymis
• Head
– Receives spermatozoa from efferent ductules
• Body
– Extends inferiorly
along the posterior
surface of the testis
Male reproductive tract and glands

Epididymis (continued)
▪ Regions of the epididymis (continued)
• Tail
– Starts near the inferior border of the testis
– Number of coils decreases
– Connects with the
ductus deferens
Male reproductive tract and glands

Male reproductive tract (continued)

▪ Ductus deferens (or vas deferens)
• 40–45 cm (160–16 in.) long
• Passes through inguinal canal as part of spermatic
cord
• Transports sperm from the epididymis
• Can store sperm for several months in a state of
suspended animation
Male reproductive tract and glands

Seminal glands (also called seminal vesicles)

▪ Sandwiched between the posterior wall of the
urinary bladder and the rectum
▪ Secretion ejected by smooth muscle lining gland
• Stimulates flagellum movement in sperm
• First step of capacitation
▪ Produce ~60 percent of
semen volume
Male reproductive tract and glands

Semen
▪ Contains sperm and seminal fluid
▪ Fluid is a combination of secretions from:
• Seminal glands
• Nurse cells
• Epididymis
• Prostate
• Bulbo-urethral glands
▪ ~2–5 mL of semen are released in a typical
ejaculation
Male reproductive tract and glands

Prostate
▪ Encircles the proximal urethra as it leaves the
bladder
▪ Produces 20–30 percent of semen volume
▪ Secretions contain seminalplasmin
• Antibiotic that may help prevent urinary tract
infections in males
Male reproductive tract and glands

Bulbo-urethral glands (Cowper’s glands)

▪ Located at the base of the penis
▪ Duct of each gland empties into the urethra
▪ Secrete thick, alkaline mucus
• Helps neutralize acids in the urethra
• Also lubricates the tip of the penis
The penis conducts urine and semen to the
exterior

Functions of the penis

▪ Two functions
1. Conducts urine to the exterior
2. Introduces semen into the female’s vagina during
sexual intercourse
Penis

Regions and structures of the penis

▪ Root of the penis
• Fixed portion that attaches the penis to the body wall
just inferior to the pubic symphysis
▪ Body (or shaft) of the penis
• Tubular, movable
portion of the organ
Penis

Regions and structures of the penis (continued)

Glans penis (head)
▪ Expanded distal end that surrounds the external
urethral orifice
▪ Neck of glans
• Narrow portion
between the shaft
and the glans
Penis

Erectile tissue
▪ Three-dimensional network with vascular spaces
▪ In the resting state, arterial branches are
constricted, and muscular partitions are tense
(restricts blood flow into the erectile tissue)
▪ Corpora cavernosa (singular, corpus cavernosum)
• Two cylindrical masses on the anterior/dorsal surface
of the penis
▪ Corpus spongiosum
• Surrounds the penile urethra
• Expands at the tip of the penis to form the glans
Penis

Tissue layers of the penis

▪ Outer skin
• Resembles thin skin of the scrotum
• Dermis has smooth muscle continuous with the
dartos muscle of the scrotum
▪ Underlying areolar tissue allows skin to move
without distorting deeper structures
▪ Elastic tissue
• Deep to the areolar tissue
• Encircling internal structures
Tissue layers of the penis
Penis

Foreskin (prepuce)
▪ Surrounds tip of penis
Smegma
▪ Waxy material
secreted by preputial
glands
Penis

Phases in the male sexual response

▪ Arousal
• Erotic thoughts or stimulation of sensory nerves in the
genital region increase parasympathetic stimulation
through pelvic nerves
• Release of nitric oxide causes arterial dilation
– Blood flow increases, engorging vascular channels
– Erection of the penis occurs
• Secretion of bulbo-urethral glands lubricates the tip of
the penis
Penis

Phases in the male sexual response (continued)

▪ Emission
• Caused by sympathetic activation
• Begins with peristaltic contractions in the ampullae of
the ductus deferens
– Pushes sperm into the prostatic urethra
• Contractions continue in the seminal glands and
prostate
• Secretions from these glands mix with sperm to form
semen
Penis

Phases in the male sexual response (continued)

▪ Ejaculation
• Powerful, rhythmic muscular contractions
– Bulbocavernosus muscles (at base) push semen
toward external urethral orifice
– Ischiocavernosus muscles (along sides) stiffen erect
penis
• Controlled by somatic motor neurons in the lower
lumbar and upper sacral segments of the spinal cord
• Contractions associated with pleasurable sensations
known as male orgasm
Penis

Impotence, or erectile dysfunction (ED)

▪ Inability to achieve or maintain an erection
▪ Various causes
• Vascular changes (e.g., low blood pressure)
• Interference with neural commands
• Psychological factors (depression, anxiety)
▪ Medications (e.g.,Viagra and Cialis) temporarily
inactivate enzymes that oppose nitric oxide (NO)
• Small amounts of NO can then produce erection
Testosterone plays a key role in establishing and
maintaining male sexual function

Hormonal interactions
▪ Hypothalamus
• Secretes gonadotropin-releasing hormone (GnRH)
– Released at a steady rate and pace
• Targets the anterior lobe of the pituitary gland
▪ Anterior lobe of the pituitary
• Responds by producing two gonadotropins
– Luteinizing hormone (LH)
– Follicle-stimulating hormone (FSH)
Hormonal interactions regulating male
reproductive function

Hormonal interactions (continued)

▪ Luteinizing hormone (LH)
• Targets the interstitial cells of the testes
– Interstitial cells secrete testosterone and other
androgens
• Testosterone levels are regulated by negative
feedback
– High testosterone level inhibits release of GnRH
Hormonal interactions regulating male
reproductive function

Hormonal interactions (continued)

▪ Follicle-stimulating hormone (FSH)
• Targets nurse cells of seminiferous tubules
• Nurse cells
– Promote spermatogenesis and spermiogenesis
– Secrete androgen-binding protein (ABP)
o Stimulates maturation of spermatids
– Secrete inhibin
o Inhibits FSH
o Provides feedback control of spermatogenesis
Hormonal control of male sexual function
Hormonal interactions regulating male
reproductive function

Peripheral effects of testosterone

▪ Maintains libido (sexual drive) and related behaviors
▪ Stimulates bone and muscle growth
▪ Establishes and maintains male secondary sexual
characteristics
▪ Maintains accessory glands and organs of the male
reproductive system
Peripheral effects of testosterone
Hormonal interactions regulating male
reproductive function

Dihydrotestosterone (DHT)
▪ Testosterone is converted to DHT in some tissues
▪ Comprises ~10 percent circulating levels of
testosterone
▪ Can bind to same receptors as testosterone
▪ Some tissues respond to DHT instead of
testosterone
• External genitalia
▪ Other tissues are more sensitive to DHT than
testosterone
• Prostate
Female reproductive structures include the
external genitalia and internal genitalia

Overall functions of the female reproductive

system
▪ Produces sex hormones
▪ Produces functional gametes
▪ Protects and supports developing embryo
▪ Maintains growing fetus
▪ Nourishes newborn infant
Female reproductive structures

Female external genitalia

▪ Vulva—outer genitals and urethra
Female internal genitalia
▪ Ovaries, uterine tubes, uterus, and vagina
Mammary gland of breast
▪ Produces milk to
nourish infant
Female reproductive structures

Female gonads are the ovaries

▪ Produce gametes (oocytes that mature into ova)
▪ Produce hormones
Female reproductive tract
▪ Uterine tubes (deliver oocyte or embryo to the
uterus)
• Normal sites of fertilization
▪ Uterus (site of embryonic and fetal development)
• Also site of exchange between maternal and
embryonic/fetal bloodstream
Female reproductive structures

Female reproductive tract (continued)

▪ Vagina (site of sperm deposition)
• Birth canal during delivery
• Passageway for fluids during menstruation
Female reproductive structures

External genitalia
▪ Mons pubis
• Pad of fatty tissue overlapping symphysis pubis
▪ Clitoris
• Contains erectile tissue
▪ Labia
• Contain glands that lubricate the entrance to the
vagina
Mammary glands
▪ Produce milk to nourish newborn infant
Major female reproductive organs are the ovaries,
uterus, and their associated structures

Ovary
▪ Paired almond-shaped organs near the lateral wall
of the pelvic cavity
▪ Three main functions
1. Production of immature female gametes (oocytes)
2. Secretion of female sex hormones (estrogens and
progesterone)
3. Secretion of inhibin (inhibits FSH production in the
anterior pituitary gland)
Female reproductive organs

Layers of the ovaries

▪ Germinal epithelium
• Layer of squamous or cuboidal cells covering the
ovary
• Continuous with the visceral peritoneum
▪ Tunica albuginea
• Dense connective tissue layer just deep to the
germinal epithelium
▪ Interior of the ovary
• Cortex (superficial layer where oocytes are
produced)
• Medulla (deep to the cortex)
The ovary
Female reproductive organs

Female reproductive system structures

▪ Uterine tube
• Expanded funnel (infundibulum) opens into the
pelvic cavity along the surface of the ovary
• Other end opens into the uterine cavity
▪ Uterus
• Inferior to the ovaries
• Usually angled anteriorly above the urinary bladder
▪ Vesico-uterine pouch
• Pocket between uterus and posterior bladder wall
Female reproductive organs

Female reproductive system structures

(continued)
▪ Recto-uterine pouch
• Pocket between posterior uterus and anterior colon
▪ Vagina
• Extends from the uterus base (cervix) to the exterior
▪ External genitalia
• Clitoris
– Stimulation produces pleasurable sensations
associated with female orgasm
• Labia
The female reproductive system
Female reproductive organs

Connective tissues and ligaments stabilize the

ovary
▪ Ovarian ligament
• Extends from uterus to medial surface of ovary
▪ Mesovarium
• Fold of mesentery; supports and stabilizes ovary
▪ Suspensory ligament
• Extends from lateral surface of ovary to pelvic wall
▪ Broad ligament
• Extensive mesentery enclosing ovaries, uterine tubes,
and uterus
• Attaches to sides and floor of pelvic cavity
Ligaments and connective tissue
Oogenesis occurs in the ovaries, and ovulation
occurs during the 28-day ovarian cycle

Oogenesis
▪ Formation and development of the oocyte
▪ Begins before birth, accelerates at puberty, ends at
menopause
▪ Nuclear events are the same as with
spermatogenesis
Oogenesis and the ovarian cycle

Steps in oogenesis
▪ Mitosis of oogonium (plural, oogonia)—female
reproductive stem cells
• Mitosis completed prior to birth
• For each oogonium, produces one oogonium and one
primary oocyte
Oogenesis and the ovarian cycle

Steps in oogenesis (continued)

▪ Meiosis I
• Begins between 3rd and 7th month of fetal
development
• Primary oocytes begin meiosis I but stop at
prophase I until puberty
– Rising FSH levels trigger start of the ovarian cycle
– Each month, some of the primary oocytes are
stimulated to complete meiosis I
• Yields haploid secondary oocyte and a polar body
– Secondary oocyte gets the majority of cytoplasm
Oogenesis and the ovarian cycle

Steps in oogenesis (continued)

▪ Ovary releases a secondary oocyte (not a mature
ovum)
• Meiosis does not complete unless fertilization occurs
Oogenesis and the ovarian cycle

Steps in oogenesis (continued)

▪ Meiosis II
• Secondary oocyte begins meiosis II
– Suspended in metaphase II at ovulation
• At fertilization, the secondary oocyte divides into a
second polar body and a mature ovum (both haploid)
Steps in oogenesis
Oogenesis and the ovarian cycle

Ovarian cycle
▪ Involves changes in ovarian follicles
• Specialized structures where oocyte growth and
meiosis I occur
▪ About 2 million primordial follicles exist at birth
• Each containing a primary oocyte
▪ By puberty, only about 400,000 primordial follicles
remain
• Others degenerated in a process called atresia
▪ Each month, FSH stimulates the development of
several follicles
Oogenesis and the ovarian cycle

Stages of the ovarian cycle

▪ Primordial follicle in egg nest
• Primordial follicle
– Inactive primary oocyte surrounded by a simple
squamous layer of follicle cells
• Egg nests
– Clusters of primary oocytes
in the outer portion of the
ovarian cortex, near the
tunica albuginea
Oogenesis and the ovarian cycle

Stages of the ovarian cycle (continued)

▪ Formation of primary follicles
• Follicular cells enlarge, divide, and form several
layers around the primary oocyte
• Follicular cells now called granulosa cells
• Zona pellucida (pellucidus, translucent)
– Region that develops around the oocyte
• Thecal endocrine cells (theca, box)
– Layer of cells that form around the follicle
• Thecal cells and granulosa cells work together to
produce estrogen
Formation of primary follicles
Oogenesis and the ovarian cycle

Stages of the ovarian cycle (continued)

▪ Formation of secondary follicles
• Follicle wall thickens, and follicular cells secrete fluid
• Fluid-filled pockets expand and separate the inner
and outer layers of the follicle
Oogenesis and the ovarian cycle

Stages of the ovarian cycle (continued)

▪ Formation of tertiary follicle
• Occurs about day 10–14 of cycle
• One secondary follicle becomes a tertiary follicle, or
mature graafian follicle
– Roughly 15 mm in diameter
• Expanded central chamber (antrum) is filled with
follicular fluid
– Oocyte projects into the antrum
• Granulosa cells form a protective layer (corona
radiata) around the secondary oocyte
Formation of tertiary follicle
Oogenesis and the ovarian cycle

Stages of the ovarian cycle (continued)

▪ Ovulation
• Tertiary follicle releases secondary oocyte and corona
radiata into the pelvic cavity
• Marks end of follicular phase and start of luteal
phase
Oogenesis and the ovarian cycle

Stages of the ovarian cycle (continued)

▪ Formation of corpus luteum (lutea, yellow)
• Empty tertiary follicle collapses
• Remaining granulosa cells proliferate
• Secrete progesterone and estrogens
– Progesterone stimulates maturation of the uterine lining
▪ Formation of corpus albicans
• Knot of pale scar tissue produced by fibroblasts
• Formed by degeneration of the corpus luteum when
fertilization does not occur after 12 days
• Marks the end of the ovarian cycle
Stages of the ovarian cycle
The uterine tubes are connected to the uterus, a
hollow organ with thick muscular walls

Uterine tubes (fallopian tubes)

▪ Hollow, muscular structures ~13 cm long
▪ Lined with ciliated epithelium
▪ Distal portion connects to the uterus
▪ Infundibulum
• Funnel-like expansion adjacent to the ovary
• Has numerous fingerlike projections (fimbriae)
– Extend into the pelvic cavity
– Drape over the surface of the ovary (but no physical
connection)
• Inner surface lined with cilia that beat toward the
lumen of the uterine tube
Uterine tubes and the uterus

Uterine tubes
(continued)
▪ Ampulla
• Muscular middle
segment of the
uterine tube
▪ Isthmus
• Short segment
connected to the
uterine wall
Uterine tubes
Uterine tubes and the uterus

Oocyte transport
▪ Involves combination of ciliary movement and
peristaltic contraction of smooth muscle in the
uterine tube
▪ Takes 3–4 days for a secondary oocyte to travel
from infundibulum to the uterine cavity
▪ Fertilization must occur within the first 12–24 hours
after ovulation
Uterine tubes and the uterus

Uterus
▪ Hollow, muscular organ
▪ Provides mechanical protection, nutritional support,
and waste removal for embryo (weeks 1–8) and
fetus (>8 weeks)
▪ Contractions in the muscular wall are important in
delivering the fetus at birth
Uterine tubes and the uterus

Layers of the uterine wall

▪ Perimetrium (peri, around
+ metra, uterus)
• Outer surface
• Incomplete serosa
continuous with the
peritoneal lining
Uterine tubes and the uterus

Layers of the uterine wall

(continued)
▪ Myometrium (myo-,
muscle)
• Thick muscular middle
layer
• Smooth muscle layer
provides force for childbirth
▪ Endometrium
• Glandular inner lining
whose characteristics
change with each uterine
cycle
Uterine tubes and the uterus

The uterine cavity and cervix

▪ Uterine cavity, or uterine lumen
• Large, superior cavity continuous with isthmus of
uterine tube
▪ Internal os (os, opening or mouth)
• Opening connecting the uterine cavity to the cervical
canal
▪ Cervical canal
• Constricted passageway at the inferior end of the
uterine cavity
• Begins at internal os; ends at external os
▪ External os
• Curving vaginal opening into the uterus
Uterine tubes and the uterus
Uterine tubes and the uterus

Regions of the uterus

▪ Fundus
• Rounded portion superior to the openings of the
uterine tubes
▪ Body
• Largest portion of the
uterus (two-thirds of
the organ)
• Ends at the constriction
encircling the internal os
Uterine tubes and the uterus

Regions of the uterus (continued)

▪ Cervix
• Inferior portion of the uterus
• Surrounds the cervical canal
• Projects into the vagina
The uterine (menstrual) cycle involves changes in
the functional layer of endometrium

Uterine vasculature
▪ Uterine artery →
▪ Arcuate arteries: encircle the endometrium →
▪ Radial arteries: supply the endometrium →
The uterine cycle

Uterine vasculature (continued)

▪ Straight arteries: supply the basilar layer (region
adjacent to the myometrium) →
▪ Spiral arteries: supply the functional layer
(contains large tubular uterine glands)
The uterine cycle

The uterine cycle, or menstrual cycle

▪ Monthly changes in the functional zone of the uterus
in response to sex hormone levels
▪ Averages 28 days in length (range 21–35 days)
▪ First cycle (menarche) begins ~11–12 years of age
▪ Cycles continue until menopause (~45–55 years of
age)
▪ Regular cycle may be interrupted by illness, stress,
starvation, or pregnancy
The uterine cycle

Phases of the uterine cycle

▪ Menstrual phase
• Degeneration of the
functional zone of the
endometrium
• Caused by
constricted spiral arteries
• Process of endometrial
sloughing (menses, or
menstruation)
– Lasts ~1–7 days
– ~35–50 mL blood lost
The uterine cycle

Phases of the uterine cycle

(continued)
▪ Proliferative phase
• Uterine gland basal cells multiply
and spread, restoring uterine
epithelium
• Stimulated and sustained by
estrogens secreted from
developing ovarian follicles
• Builds the functional zone to
several millimeters thick
• Uterine glands manufacture
glycogen-rich mucus
– Can be metabolized by an early embryo
The uterine cycle

Phases of the uterine cycle

(continued)
▪ Secretory phase
• Uterine glands enlarge
– Increased secretion of
glycoproteins to support embryo
• Arteries supplying uterine wall
elongate and spiral through the
functional zone
• Stimulated by both progesterone
and estrogens from the corpus
luteum
• Begins at ovulation and lasts until
menses
The vagina opens into the vestibule

Vagina
▪ Elastic, muscular tube
▪ Extends from the cervix to the vestibule (space
bordered by the labia minora)
▪ Typically 7.5–9 cm (3–3.6 in.) long
▪ Variable diameter (highly distensible)
▪ Internal passageway is the vaginal canal
Vagina and external genitalia

Functions of the vagina

1. Passageway for menstrual fluids
2. Receives penis during sexual intercourse and
holds spermatozoa prior to their passage into the
uterus
3. Forms inferior portion of birth canal
Vagina and external genitalia

Components of the vagina

▪ Vaginal canal
• Internal passageway
• Lined by nonkeratinized stratified squamous
epithelium
▪ Fornix
• Shallow recess in the
vagina surrounding the
tip of the cervix
▪ Rugae
• Folds formed by the
vaginal lining when
relaxed
Vagina and external genitalia

Components of the vagina (continued)

▪ Hymen
• Elastic epithelial fold that usually partially blocks
entrance to the vagina
– Frequently absent
• Stretched or torn during
intercourse, tampon
use, or heavy physical
exercise
Vagina and external genitalia

Vulva, or pudendum
▪ Area containing the female external genitalia
▪ Vestibule
• Central space bounded by small folds called labia
minora (singular, labium minus)
▪ Lesser vestibular glands
• Secrete onto the vestibular surface, keeping it moist
▪ Greater vestibular glands (Bartholin’s glands)
• Activated during sexual arousal
• Mucous glands that discharge into the vestibule
• Same embryonic origins as the bulbo-urethral glands
of males
Vagina and external genitalia

Vulva, or pudendum (continued)

▪ Vestibular bulbs
• Masses of erectile tissue on either side of the vaginal
entrance
• Have the same embryonic origin as the corpus
spongiosum of the penis
▪ Mons pubis
• Bulge of adipose tissue deep to the skin and
superficial to the pubic symphysis
Vagina and external genitalia

Vulva, or pudendum (continued)

▪ Clitoris
• Projects into the vestibule
• Contains erectile tissue comparable to the corpora
cavernosa and corpus spongiosum of the penis
▪ Prepuce, or hood
• Extensions of the labia minora encircling the body of
the clitoris
▪ Labia majora (singular, labium majus)
• Prominent folds of skin encircling the labia minora
and adjacent structures
Female external anatomy
Each breast contains a mammary gland that
secretes milk

Mammary glands
▪ Provide nourishment (milk) for developing infant
▪ Milk production (lactation) controlled by hormones
released by the reproductive system and the
placenta
▪ Located on the anterior chest, directly over the
pectoralis major muscle
Mammary glands

Structure of a mammary gland

▪ Embedded in the subcutaneous tissue of the
pectoral fat pad deep to the skin
▪ Suspensory ligaments of the breast
• Bands of dense connective tissue
• Surround the duct system and form partitions
between lobes and lobules
▪ Glandular tissue divided into lobes
• Each lobe has several secretory lobules
• Each lobule is composed of secretory alveoli
Mammary glands

Structure of a mammary gland (continued)

▪ Ducts from the lobules converge into one
lactiferous duct per lobe
• Each lactiferous duct expands near the nipple to form
a lactiferous sinus
▪ Nipple
• Conical projection where 15–20 lactiferous sinuses
open onto the body surface
▪ Areola
• Reddish-brown skin around the nipple
• Grainy texture from sebaceous glands deep to the
surface
The breast
The ovarian and uterine cycle are regulated by
hormones of the hypothalamus, pituitary gland,
and ovaries
Ovarian and uterine cycles
▪ Ovarian and uterine cycles are controlled by cyclical
changes in hormones
▪ Two cycles must operate synchronously for proper
reproductive function
▪ Steps in ovarian cycle hormonal regulation
1. Release of gonadotropin-releasing hormone
(GnRH)
– From hypothalamus
– Causes production and secretion of FSH
– Causes production (not secretion) of LH
Ovarian cycle, phase 1
Regulation of the ovarian and uterine cycles

▪ Steps in ovarian cycle hormonal regulation

(continued)
2. Follicular phase of the ovarian cycle
– Begins when FSH stimulates some secondary follicles
to become tertiary follicles
– As follicles develop, FSH levels decline (as a result of
negative feedback effects of inhibin)
– Developing follicles also secrete estrogens (especially
estradiol)
o Low levels of estrogens inhibit LH secretion
o Inhibition decreases as estrogen levels climb
o Estrogen decreases basal body temperature about
0.3ºC (0.5ºF) lower than during the luteal phase
Ovarian cycle, phase 2
Regulation of the ovarian and uterine cycles

▪ Steps in ovarian cycle hormonal regulation

(continued)
3. Luteal phase
– GnRH and elevated estrogen levels stimulate LH
secretion
– Massive surge in LH on or around day 14 triggers:
o Completion of meiosis I by the primary oocyte
o Forceful rupture of the follicular wall
o Ovulation (~9 hours after LH peak)
o Formation of corpus luteum
– Luteal phase begins after ovulation
Regulation of the ovarian and uterine cycles

▪ Steps in ovarian cycle hormonal regulation

(continued)
3. Luteal phase (continued)
– Corpus luteum secretes progesterone
o Stimulates and sustains endometrial development
– Progesterone levels increase, and estrogen levels fall
o Suppresses GnRH
– If pregnancy does not occur, corpus luteum
degenerates
o Progesterone levels fall
o GnRH increases and begins a new cycle
Full ovarian cycle
Gonadotropic hormone levels (FSH and LH)
Follicle stages during ovarian cycle
Ovarian hormone levels
Endometrial changes during uterine cycle
Basal body temperature
Key events of ovarian and uterine cycles
Clinical Module: Birth control strategies vary in
effectiveness and associated risks

Male condoms (prophylactics, or

“rubbers”)
▪ Cover glans and shaft of penis
during intercourse
▪ Prevent spermatozoa from reaching
the female reproductive tract
▪ Only strategy that protects against
sexually transmitted diseases
(STDs)
• Examples: syphilis, gonorrhea,
human papillomavirus (HPV), and
AIDS
Birth control strategies

Diaphragm with spermicide

▪ Diaphragm
• Dome-shaped silicone cup
with a flexible rim
• Because of variability in
vagina size, must be fitted to
an individual
• Inserted prior to intercourse
to cover the external os
• Must be coated with
spermicide to be effective
• Failure rate 5–6 percent even
with proper fit
Birth control strategies

Birth control pills (oral

contraceptives)—combined
(estrogen and progesterone)
▪ The most effective form of birth
control when used as prescribed
▪ Have certain health risks
• Can worsen problems with
hypertension, diabetes mellitus, epilepsy, gallbladder
disease, heart trouble, or acne
• Increases risk of venous thrombosis, strokes,
pulmonary embolism, and (for women over 35) heart
disease
Birth control strategies

Progesterone-only forms of birth

control
▪ Progesterone-only pill (taken
daily)
▪ Depo-Provera injection (injected
every 3 months)
• Uterine cycles become irregular and
cease in 50 percent of women
▪ Problems include:
• Tendency to gain weight
• Slow return to fertility (up to 18
months) after discontinuing
injections
Birth control strategies

Intrauterine device (IUD)

▪ Small plastic loop or a T
inserted into the uterine cavity
▪ Copper type affects sperm
movement, blocking it from
oocyte
▪ Hormonal type may prevent
ovulation and thickens cervical
mucus, blocking sperm entry
Birth control strategies

Rhythm method, or “Natural

Family Planning”
▪ Abstaining from sexual activity
on days ovulation may be
occurring
▪ Timing based on patterns and
physical changes indicating
ovulation
• Basal body temperature
• Cervical mucus texture
• Urine tests for LH
▪ High failure rate (13–20 percent) due to irregularity
in women’s cycles
Birth control strategies

Hormonal post-coital
contraceptives (Plan B)
▪ Also called the emergency
“morning after” pill
▪ Involves taking levonorgestrel
contraceptive pills up to 3 days
after unprotected intercourse
▪ Prevents the ovary from
releasing an oocyte for longer
than usual or interferes with
fertilization
▪ Can be purchased over-the-
counter
Birth control strategies

Surgical sterilization—male
▪ Vasectomy
• Each ductus deferens is cut and blocked (either
segment is removed and tied/cauterized, or silicone
plug is inserted)
– Relatively easy to reverse with silicone plugs
• Can be performed in a physician’s office in minutes
• Failure rate extremely low
• No disruption in sexual function
• Sperm are still produced but degenerate in the male
reproductive tract
Vasectomy
Birth control strategies

Surgical sterilization—
female
▪ Tubal ligation
• Each uterine tube is cut and
tied
– Can be done by laparoscopy
• Requires general anesthesia
• Complications are more likely
than with a vasectomy
• Failure rate also extremely
low
Clinical Module: Reproductive system disorders
are relatively common and often deadly
Prostate disorders

▪ Benign prostatic hypertrophy (BPH)

• Occurs spontaneously in men, typically over age 50
• Declining testosterone production and the presence of
estrogen may stimulate growth
• Can constrict prostatic
urethra and affect urination
Reproductive system disorders

Prostate disorders (continued)

▪ Prostate cancer
• Second most common cause of cancer deaths in
males
• Can be screened for by blood tests for prostate-
specific antigen (PSA)
• Treatment is radiation or surgical removal of prostate
(prostatectomy)
Reproductive system disorders

Testicular cancer
▪ Occurs at relatively low rate (1 case per 263 males
per year)
▪ More than 95 percent result from abnormal
spermatocytes or spermatogonia
▪ Treatment is combination of
orchiectomy (testes removal) and
chemotherapy
▪ Survival rate near 99% as a
result of early diagnosis
and improved treatment
 Reproductive system disorders

Breast disorders
▪ Changing hormone levels can cause inflammation of
the mammary gland tissues
▪ Cysts
• Formed if inflamed lobules are walled off by scar
tissue
• Fibrocystic disease
– Condition in which clusters of cysts can be felt as
discrete masses
– Benign condition, but biopsy may be needed to
distinguish masses from breast cancer

© 2018 Pearson Education, Inc.

Reproductive system disorders

Breast disorders (continued)

▪ Breast cancer
• Malignant metastasizing tumor of mammary gland
• Leading cause of death in women ages 35–45
– Most common in women over age 50
• Notable risk factors
– Family history of breast cancer
– First pregnancy after age 30
– Early menarche or late menopause
• Treatment includes surgery, radiation, chemotherapy,
and hormones
– Surgical removal may involve removal of part or all of
mammary gland as well as axillary lymph nodes
Breast cancer
Reproductive system disorders

Ovarian cancer
▪ Accounts for more deaths than any other cancer of
female reproductive system
▪ Treatment is chemotherapy, radiation, and surgery
▪ Prognosis
• For cancers originating in the general ovarian tissues
or abnormal oocytes, relatively good prognosis
• For 85 percent of ovarian cancers that are
carcinomas (epithelial cancers), sustained remission
is obtained in only one-third of cases
Ovarian cancer
Reproductive system disorders

Cervical cancer
▪ Starts in cells of cervix
▪ Death rate decreased
as a result of Pap test for
early detection
▪ Human papillomavirus (HPV) is responsible for 75
percent of cervical cancers
• Vaccine protects against several types of HPV
Reproductive system disorders

Sexually transmitted diseases (STDs)/sexually

transmitted infections (STIs)
▪ Transferred from person to person primarily or
exclusively by sexual intercourse
▪ Consequences range from inconveniences to lethal
▪ Include at least two dozen bacterial, viral, and fungal
infections
• Examples: Chlamydia, HIV, syphilis, gonorrhea
Reproductive system disorders

Sexually transmitted diseases (STDs)/sexually

transmitted infections (STIs) (continued)
▪ Incidence increasing in the U.S.
• Contributors to the problem include poverty,
intravenous drug use, prostitution, and drug-resistant
pathogens