Transcript Slide 1

Reproductive System
rev 5-11
The term genitalia refers to male and female
reproductive organs.
Male Reproductive System Anatomy
The scrotal sac contains 2 testes.
– The process of sperm formation is called
spermatogenesis.
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• The testes are located outside of the body
because sperm need lower temperatures
to survive.
• Sperm production takes place in the
seminiferous tubules of the testes
– In between the seminiferous tubules
are interstitial cells which produce
testosterone, the male hormone.
• Many seminiferous tubules join to become
the epididymus. Sperm are stored here
and maturation also occurs.
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• Sperm enter the vas deferens or ductus
deferens which passes through an opening in
the wall of the body called the inguinal
canal.
– The ability of newly formed sperm to swim
develops in the epididymis and the vas
deferens.
– Sperm continue their maturation here.
– A vasectomy ties off the vas deferens so
sperm are no longer available for
fertilization.
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• The vas deferens connects to the ejaculatory
duct after it merges with the seminal vesicle
duct.
• When the male ejaculates semen, rhythmic
contractions of smooth muscle propel the
sperm through the ejaculatory duct and then
through the urethra.
• The penis is the male organ of sexual
intercourse. It contains erectile tissue that
fills with blood and causes the erection during
sexual stimulation.
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Glands which help sperm survive:
• Seminal vesicles produce seminal fluid which is
a watery mixture containing fructose, which
provides energy for the sperm, and
prostaglandins which are thought to induce
muscle contractions.
• Prostate gland:produces an alkaline fluid which
raises the pH of the vagina to a more optimal pH.
• Cowper’s or bulbourethral glands secrete
mucus into the urethra during sexual arousal.
This provides lubrication for intercourse and
washes away traces of acidic urine
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Sperm Production
• Meiosis:
– Purpose: produces sperm and eggs with half
the number of chromosomes (23) of somatic
cells. (Cells with ½ the chromosomes are called
haploid cells.)
– Sperm formation and maturation takes about
9-10 weeks. Sertoli cells surround and
nourish the growing sperm cells.
– Egg maturation and release takes about 14
days and occurs once per month
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Cell division terminology:
• Gamete: sperm or egg produced by meiosis
• Diploid: describes the “normal” number of
chromosomes in any cell
• Haploid: cell which contain 23 chromosomes
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Sperm
• consist of 3 major parts: a head, midpiece,
and a tail.
• The head contains the nucleus and 1/2 of the
chromosome number of the parent.
– Acrosome covers the head.
– The midpiece contains mitochondria and
ATP.
• The tail propels the sperm.
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Regulation of Male Reproductive Activity
Hormones:
• Testosterone:
– Source: Leydig cells in seminiferous tubules
– Function: controls growth and function of male
reproductive tissues, stimulates aggression and
sexual behavior, and secondary sexual characteristics
• GnRH: Gonadotropin-releasing hormone from the
hypothalamus; stimulates the anterior pituitary gland to
release LH and FSH
• LH: stimulates production of testosterone
• FSH (Follicle Stimulating Hormone): may enhance sperm
formation
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The Female Reproductive System
Anatomy:
The external female genitalia or vulva:
• the Mons Pubis, a fatty, rounded tissue area,
covers the pubic symphysis.
• The Labia Majora are 2 elongated,
pigmented, hair covered, fat padded skin
folds which surround and enclose the Labia
Minora.
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• The Labia Minora are 2 smaller, highly
vascular, hair free folds.
• The Clitoris is a small organ partly enclosed
by the labia minora.
• The Urethral opening lies between the
clitoris and the vaginal opening.
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Internal female reproductive organs
Ovaries are the primary reproductive
organs. They lie near the ends of the
fallopian tubes (also called oviducts).
• The ovaries produce eggs called
oocytes. Eggs have 1/2 the number of
chromosomes as the parent.
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• They also produce the hormones
estrogen and progesterone
• The distal ends of the fallopian tubes
are funnel shaped and have fingerlike
projections called fimbriae.
• The egg is propelled toward the uterus
by the cilia on the walls of the fallopian
tubes.
• If fertilization by a sperm occurs, it
usually takes place in the distal third of
the fallopian tube.
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The uterus is a hollow, pear shaped, muscular
organ which is located between the bladder
and the rectum. It will “incubate” the fertilized
egg.
• Its narrow, lower end is called the cervix.
The middle part of the uterus is called the
body and the upper part is called the fundus.
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Uterine layers
– Endometrium: inner layer
• A fertilized egg will implant into this layer.
After implantation, the endometrium helps
form the placenta.
• This is the layer that sloughs off during
menstrual flow.
– Myometrium: middle, muscular layer
– Perimetrium: outer layer
– Cervix: the narrow opening in the lower part
of the uterus
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• The cervix joins the vagina.
– It serves as a birth canal and the female
organ for sexual intercourse.
– It permits the passage of menstrual blood
to the outside of the body.
– Vestibular glands secrete lubricating
mucus.
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The Breasts are considered to be part of the
reproductive organs
• are really modified sweat glands which
produce milk to nourish newborn infants.
• milk production (lactation) is stimulated by
estrogen and progesterone only when birth
has actually occurred.
• the nipple is at the center of each breast. It
contains smooth muscles that can contract
and cause the nipple to become erect.
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• Surrounding the nipple is the pigmented
areola.
• Internally, the breasts contain mammary
glands that produce milk.
– The glands consist of many milk producing
lobules. Contractile cells around each lobule
allow the milk to be released and ducts
deliver the milk to the nipple.
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Menstrual Cycle
Each month the ovaries and uterus go through a
pattern of changes called the menstrual cycle.
– Typically lasts 28 days; is controlled by
hormones
– Menstrual cycles begin at puberty and end at
menopause
• A complete menstrual cycle consists of 2 linked
cycles: an ovarian and a uterine cycle
• Ovarian cycle: oocytes mature and are
released
– Immature follicle develops; GnRH, FSH and
LH increase
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– Estrogen and progesterone secreted
– Follicle matures; now called Graafian follicle
– Increasing estrogen causes surge of LH so
that ovulation occurs—the egg is released
– A corpus luteum forms from the ruptured
follicle site and secretes large amounts of
estrogen and progesterone to prepare the
endometrium for the possible pregnancy
– If no pregnancy occurs, estrogen and
progesterone levels decline and another
menstrual cycle begins.
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– If the egg is fertilized, it moves down the
fallopian tube and implants in the uterine
endometrium
– The developing embryo secretes its own
hormones to enable the corpus luteum to
continue to secrete estrogen and
progesterone until the placenta develops.
– The placenta will take over the job of
secreting progesterone and estrogen as well
as become a nutrient/waste filter between the
maternal and fetal circulation.
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Uterine cycle: prepares uterus for pregnancy
• Menstrual phase: With no pregnancy, days 1–5,
estrogen and progesterone decrease,
endometrial lining degenerates, menstruation
occurs
– Proliferative phase: days 6–14, estrogen and
progesterone increase, endometrial lining
begins to proliferate
– Ovulation: day 14
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– Secretory phase: corpus luteum produces
progesterone and estrogen, endometrium
continues to proliferate, uterine glands mature
and produce glycogen as a potential energy
source for an embryo
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Maintenance of Menstrual Cycle
• Cycles of hormones of pituitary and
reproductive structures:
– Positive feedback:
• In proliferative phase, increasing estrogen
causes surge in LH
– Negative feedback:
• In secretory phase, steady levels of
estrogen and progesterone inhibit LH and
FSH release
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Infertility: Inability to Conceive
• Many causes of infertility:
– Number and quality of sperm, pelvic
inflammatory disease (PID), endometriosis
• Enhancing fertility:
– Options: artificial insemination, in vitro
fertilization, GIFT and ZIFT,
fertility-enhancing drugs, surrogate mothers
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Sexually Transmitted Diseases (STDs): Worldwide
Problem
• Bacterial: gonorrhea, syphilis, chlamydia
• Viral: HIV, hepatitis B, genital herpes,
genital warts
• Other: yeasts (Candida), protozoan
(Trichomonas), arthropod (pubic lice)
• Prevention:
– Strategies: choose partner wisely,
communicate, use suitable barriers, get tested
and treated
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