Download Chapter 1 - Monsignor Farrell High School

Reproductive Systems
Reproductive Organs
• Primary sex organs: Produce and house sex cells
• Secondary sex organs: Provide the route by which
sex cells unite
Reproductive Organs
• Primary sex organs (called gonads) include testes in
males and ovaries in females.
• The gonads produce sex cells (gametes); these include:
sperm in males, and eggs (ova) in females.
• Secondary sex organs encompass all other organs
necessary for reproduction.
• In males, this includes a system of ducts, glands, and the
penis, all of which are charged with storing and
transporting sperm.
• In females, the secondary sex organs provide a location
for the uniting of egg and sperm as well as the
environment for nourishing a fertilized egg.
Male Reproductive System
 Serves to produce, transport, and introduce
mature sperm into the female reproductive
tract
Testes
Spermatic cord
Cremaster muscle
Testis
Median septum
Testes
• The penis and the scrotum are the external portions of the
male reproductive system. Inside the scrotum reside two
testes, the organs that manufacture sperm and produce the
male hormone testosterone.
• Extending from the abdomen to each testicle is a strand of
connective tissue called the spermatic cord; the sperm
duct (vas deferens) as well as blood and lymphatic vessels
and nerves lie within the cord.
• Two small, oval testes lie suspended in a sac of tissue called
the scrotum.
• The median septum divides the scrotum.
• The cremaster muscle surrounds the spermatic cord and
testis. In cold weather, it contracts to draw the testes closer
to the body for warmth.
Inside the Testes
Rete testis
Efferent ductules
Spermatic ducts
Lobule
Epididymis
Seminiferous tubules
Vas deferens
Inside the Testes
• Inside the testes, a series of spermatic ducts carry
sperm away from the testis and out of the body.
• Fibrous tissue separates each testis into over 200
lobules. Coiled within each lobule are one to three
seminiferous tubules, where sperm are produced.
Also in the wall of the tubule are sustentacular
(Sertoli) cells. These cells promote the development of
sperm by supplying nutrients, removing waste, and
secreting the hormone inhibin, which plays a role in the
maturation and release of sperm.
• Lying between the seminiferous tubules are clusters of
interstitial cells—called Leydig cells—that produce
testosterone.
Inside the Testes
• A network of vessels called the Rete testis lead away
from the seminiferous tubules; these vessels provide a
location in which sperm partially mature.
• Efferent ductules conduct immature sperm away from
the testis to the epididymis. Sperm move from the
head of the epididymis to the tail, maturing as they go.
They are then stored in the tail of the epididymis,
where they remain fertile for 40 to 60 days. After that,
unless they are released, they disintegrate and are
reabsorbed by the epididymis.
• Sperm leave the tail of the epididymis and pass into the
vas deferens.
Vas Deferens
Vas deferens
Ejaculatory duct
Vas Deferens
• The vas deferens travels up through the spermatic cord,
into the pelvic cavity, over the ureter to the prostate,
and behind the bladder.
• As the vas deferens turns downward, it joins the
seminal vesicle to form the ejaculatory duct. The
ejaculatory ducts pass through the prostate and empty
into the urethra.
Question
Where is testosterone produced?
A.
B.
C.
D.
Seminiferous tubules
Interstitial cells of the testes
Epididymis
Sustentacular (Sertoli) cells
Accessory Glands
Accessory Glands
• Located at the base of the bladder, a pair of seminal vesicles
secretes a thick, yellowish fluid into the ejaculatory duct. The
fluid comprises about 60% of semen; it contains fructose (an
energy source for sperm motility) and substances that nourish
and ensure sperm motility.
• The prostate gland encircles both the urethra and ejaculatory
duct. It secretes a thin, milky, alkaline fluid into the urethra;
besides adding volume to the semen (it comprises about 30% of
the fluid portion of semen), the fluid enhances sperm motility.
• Two pea-shaped bulbourethral glands (also called Cowper’s
glands) secrete a clear fluid into the penile portion of the
urethra during sexual arousal. Besides serving as a lubricant for
sexual intercourse, the fluid also neutralizes the acidity of
residual urine in the urethra, which would harm the sperm.
Penis
• Body is called the shaft.
• Head is the glans penis.
• Loose skin covering is the prepuce.
Interior of the Penis
Corpus cavernosa
Corpus spongiosum
Interior of the Penis
• Three cylinders of erectile tissue fill the shaft of the
penis. During sexual arousal, the tissues fill with blood,
causing the penis to enlarge and become erect.
• The two larger cylinders of tissue are called the corpus
cavernosa (singular: corpus cavernosum).
• The smaller cylinder of tissue, called the corpus
spongiosum, encircles the urethra.
Spermatogenesis
Spermatogenesis
1. Sperm begin as spermatogonia, primitive sex cells located
in the walls of the seminiferous tubules.
2. Spermatogonia divide by mitosis to produce two daughter
cells, each with 46 chromosomes.
3. These cells then differentiate into slightly larger cells called
primary spermatocytes, which move toward the lumen of
the seminiferous tubule.
4.Through meiosis, the primary spermatocyte yields two
genetically unique secondary spermatocytes, each with
23 chromosomes.
5. Each secondary spermatocyte divides again to form two
spermatids.
6.Spermatids differentiate to form heads and tails and
eventually transform into mature spermatozoa (sperm),
each with 23 chromosomes.
Spermatozoa
Head
Middle piece
Tail
Spermatozoa
• The head contains the nucleus, which is packed with
genetic material. A cap called an acrosome contains
enzymes that help the sperm penetrate the egg during
fertilization.
• The middle piece contains numerous mitochondria
that supply the sperm with energy.
• The tail is a flagellum whose beating, whip-like
movements propel the sperm forward.
Semen
 65% of volume comes from seminal vesicles
 30% comes from prostate gland
 5% comes from bulbourethral gland
Semen
• Semen is a whitish fluid containing both sperm and
the fluid secretions of the accessory glands. Each
ejaculation expels between 2 and 5 ml of semen
containing between 40 and 100 million sperm.
• Immediately after ejaculation, semen becomes sticky
and jelly-like. This promotes fertilization by allowing
the semen to stick to the walls of the vagina and cervix
instead of immediately draining out. The alkalinity of
semen counteracts the acidity of the vagina; this is
important because sperm become immobile in an
acidic environment.
Question
Where do sperm begin development?
A. Seminiferous tubules
B. Seminal vesicles
C. Vas deferens
D. Epididymis
Male Sexual Response
 Excitement
 Plateau
 Orgasm
 Resolution
Female Reproductive System
Female Reproductive System
• The organs of the female reproductive system are
housed within the abdominal cavity.
• The female’s primary reproductive organs (gonads) are
the ovaries. The ovaries produce ova, the female
gametes.
• The accessory organs—which include the fallopian
tubes, uterus, and vagina—extend from near the ovary
to outside the body.
Ovaries
Ovaries
• Two ovaries—about the size and shape of almonds—sit
on each side of the uterus where they produce both egg
cells (ova) and sex hormones.
• Each ovary contains thousands of immature eggs.
During a menstrual cycle, hormones cause one egg to
begin to develop. Enclosed inside a bubble-like follicle,
the egg develops until, at a certain point, the follicle
bursts and releases the egg. This figure shows the stages
of a single egg and follicle development. (The ovary
does not contain eggs in multiple stages of
development.)
Internal Genitalia
Isthmus
Fundus
Ampulla
Body
Infundibulum
Cervix
Vagina
Fornices
Internal Genitalia
• The fallopian tubes are about 4 inches (10 cm) long and
extend from the ovary to the uterus. A narrow isthmus is
the portion closest to the uterus. The middle portion (the
ampulla) is the usual site of egg fertilization. Cilia lining
the inside beat to help propel the egg toward the uterus.
The distal end is the infundibulum. The fallopian tube
does not attach directly to the ovary; finger-like projections
called fimbriae fan over the ovary.
• The vagina is a muscular tube about 3 inches (8 cm) long; it
is a receptacle for the penis and sperm, a route for the
discharge of menstrual blood, and the passageway for the
birth of a baby. The smooth muscle walls can expand
greatly, such as during childbirth. The vagina extends
slightly beyond the cervix, creating pockets called fornices.
Internal Genitalia
• The uterus is a muscular chamber that houses and
nurtures a growing embryo. It sits between the urinary
bladder and the rectum, held in place by the broad
ligament. It tilts forward over the bladder. The curved,
upper portion is the fundus. The upper two corners
connect with the fallopian tubes. The central region is the
body. The inferior end is the cervix. A passageway through
the cervix, called the cervical canal, links the uterus to the
vagina. Glands within the cervical canal secrete thick
mucus; during ovulation, the mucus thins to allow sperm to
pass.
External Genitalia
Mons pubis
Prepuce
Clitoris
Labia majora
Labia minora
Lesser vestibular gland
Greater vestibular gland
External Genitalia
• The mons pubis is a mound of hair-covered adipose tissue
overlying the symphysis pubis.
• The labia majora (singular: labium majus) are thick folds
of skin and adipose tissue; hair grows on the lateral surfaces
of the labia majora while the inner surfaces are hairless.
• The labia minora (singular: labium minus) are two
thinner, hairless folds of skin just inside the labia majora.
• The area inside the labia is called the vestibule; it contains
the urethral and vaginal openings.
External Genitalia
• The labia minora meet to form a hood of tissue called the
prepuce over the clitoris. The clitoris is a small mound of
erectile tissue that resembles a penis. Its role is strictly
sensory, providing a source of sexual stimulation.
• A pair of mucous glands, called the lesser vestibular
glands (or Skene’s glands) open into the vestibule near the
urinary meatus, providing lubrication.
• Two pea-sized glands called greater vestibular glands (or
Bartholin’s glands) sit on either side of the vaginal
opening; their secretions help keep the vulva moist and
provide lubrication during sexual intercourse.
Question
What is the curved upper portion of the uterus called?
A. Infundibulum
B. Fimbriae
C. Vestibule
D. Fundus
Breasts
Lobule
Lactiferous duct
Lactiferous sinus
Acini
Suspensory ligaments
Areola
Breasts
• Each breast contains 15 to 20 lobules separated by fibrous
tissue and adipose tissue.
• Each lobule consists of clusters of tiny, sac-like acini that
secrete milk during lactation. Minute ducts drain the acini,
merging to form larger ducts. The ducts unite to form a
single lactiferous duct for each lobe. Before reaching the
nipple, the ducts enlarge slightly to form lactiferous
sinuses. Each duct ends in a tiny opening on the surface of
the areola.
• A pigmented area called the areola encircles the nipple.
Numerous sebaceous glands (that look like small bumps)
dot the surface. Sebum from these glands lubricates the
areola, helping prevent dryness and cracking during
nursing.
• Suspensory ligaments help support the breasts and also
serve to attach the breasts to the underlying pectoralis
muscles.
Female Reproductive Cycle
• Ovarian cycle: Centers on changes in the ovaries
• Menstrual cycle: Focuses on changes in the uterus
• The reproductive cycle averages 28 days in length;
however, the length of the cycle can range from 20 to
45 days. Both cycles are controlled by the cyclical
secretion of hormones: the ovarian cycle is governed
by the hormones FSH (follicle-stimulating hormone)
and LH (luteinizing hormone); the menstrual cycle is
under the influence of estrogen and progesterone.
Ovarian Cycle
• Follicular phase: Triggered by follicle-stimulating
hormone (FSH)
• Ovulation: Prompted by spike in luteinizing hormone
(LH)
• Luteal phase: Influenced by high levels of
progesterone secreted by corpus luteum
View animation on “Ovarian cycle”
Ovarian Cycle
• Low levels of estrogen and progesterone stimulate the
hypothalamus to release gonadotropin-releasing hormone
(GnRH). GnRH stimulates the anterior pituitary to release
FSH and LH.
• FSH triggers several of the follicles to resume development,
beginning the follicular phase. Only one follicle, will make
it to maturity. The developing follicle secretes estrogen
(which stimulates the thickening of the endometrium in the
menstrual cycle) and small amounts of progesterone. The
follicle migrates to the surface of the ovary. The mature
follicle is called a graafian follicle.
Ovarian Cycle
• In the mid-point of the cycle, estrogen levels peak,
triggering a spike in LH. The sudden spike in LH causes the
follicle to rupture and release the ovum (ovulation). The
fimbriae of the fallopian tube sweep across the top of the
ovary to catch the emerging oocyte.
• The remnants of the follicle remain on the ovary and form
the corpus luteum, which marks the beginning of the
luteal phase. The corpus luteum secretes large amounts of
progesterone and small amounts of estrogen. The
progesterone causes the endometrium to continue to
thicken and become more vascular. High levels of
progesterone and estrogen also inhibit the pituitary from
producing FSH and LH so that no other follicles develop.
Ovarian Cycle
• If fertilization doesn’t occur, the corpus luteum degenerates
into inactive scar tissue called the corpus albicans.
• Estrogen and progesterone levels plummet, causing the
endometrium to slough off, resulting in menstruation. With
the decline in ovarian hormones, the pituitary is no longer
inhibited; FSH levels begin to rise and a new cycle begins.
Menstrual Cycle
1.
2.
3.
4.
5.
Menstrual phase
Proliferative phase: ↑ estrogen → growth of blood
vessels
Ovulation
Secretory phase: ↑ progesterone → ↑ endometrial
thickening
Premenstrual phase: ↓ progesterone → ischemic
endometrium
Menstrual Cycle
• Estrogen and progesterone drive the menstrual cycle.
• Menstrual phase: The first day of bleeding is the first day
of the menstrual cycle; it lasts 3 to 5 days as the
endometrium sheds its functional layer.
• Proliferative phase: About day 6, rising levels of estrogen
(secreted by the ovaries) stimulates the repair of the base
layer as well as the growth of blood vessels.
• Secretory phase: The endometrium develops into a
nutritious bed about 5 to 6 mm thick.
• Premenstrual phase: If fertilization doesn’t occur, the
corpus luteum atrophies and progesterone levels plummet.
Blood vessels nourishing the endometrium spasm,
interrupting blood flow. The endometrium becomes
ischemic and necrotic, causing it to slough off.
Female Sexual Response
 Excitement
 Plateau
 Orgasm
 Resolution
Question
A surge in which hormone causes ovulation?
A. Follicle-stimulating hormone (FSH)
B. Luteinizing hormone (LH)
C. Estrogen
D. Progesterone