Transcript The Reproductive Systemx

The Reproductive
System
The Reproductive System
• Gonads—primary sex organs
▫ Testes in males
▫ Ovaries in females
• Gonads produce gametes (sex cells)
and secrete hormones
▫ Sperm—male gametes
▫ Ova (eggs)—female gametes
Female Reproductive System
• Ovaries
• Duct System
▫ Uterine tubes (fallopian tubes)
▫ Uterus
▫ Vagina
• External genitalia
Female Reproductive System
Figure 16.8a
Ovaries
• Within each ovary are structures called
ovarian follicles
▫ Each follicle consists of an immature egg
called a oocyte
▫ Each month in adult women, a follicle
ejects its oocytes from an ovary
 Called ovulation
Figure 16.7
Figure 16.11
Duct System
•Uterine tubes (fallopian tubes)
•Uterus
•Vagina
Uterine (Fallopian) Tubes
• Receive the ovulated oocyte and provide a
site for fertilization
• Attach to the uterus
• Little or no contact between ovaries and
uterine tubes
• Cilia create currents that carry oocytes
into the tubes
• Carried to the uterus by peristalsis and
beating of cilia
Female Reproductive System
Figure 16.8b
Uterus
• Hollow thick walled muscular organ
• Functions of the uterus
▫ Receives a fertilized egg
▫ Retains the fertilized egg
▫ Nourishes the fertilized egg
• Narrow neck of the uterus that projects
into the vagina is called the cervix
Uterus
• The uterine wall is composed of 3 layers
▫ Perimetrium
▫ Myometrium
▫ Endometrium
• If fertilization occurs, the embryo burrows
down into endometrium and develops
there
• If no fertilization occurs, the endometrium
is shed during menstruation
Vagina
• Extends from cervix to exterior of body
• Serves as the birth canal
• Receives the penis during sexual
intercourse
• Hymen—partially closes the vagina until it
is ruptured
• The pH of vagina is acidic, which keeps it
free from infection and hostile to sperm
Clitoris
• Contains erectile tissue
• Corresponds to the male penis
• The clitoris is similar to the penis in that it
is
▫ Composed of sensitive erectile tissue
▫ Becomes swollen with blood during
sexual excitement
Mammary Glands
• Present in both sexes, but only
function in females
▫ Modified sweat glands
• Function is to produce milk
• Stimulated by sex hormones (mostly
estrogens) to increase in size
Female Mammary Glands
Figure 16.13a
Male Reproductive System Overview
• Testes
• Duct system
▫ Epididymis
▫ Ductus (vas) deferens
▫ Urethra
Male Reproductive System Overview
• Accessory organs
▫ Seminal vesicles
▫ Prostate
▫ Bulbourethral glands
• External genitalia
▫ Penis
▫ Scrotum
Male Reproductive System
Figure 16.2a
Testes
• Each lobule contains one to four
seminiferous tubules
▫ Tightly coiled structures
▫ Function as sperm-forming factories
Figure 16.5a
Testes
Figure 16.1
External Genitalia
• Scrotum
▫ Divided sac of skin outside the
abdomen
▫ Maintains testes at 3°C lower than
normal body temperature to protect
sperm viability
Epididymis
• Functions to mature and store sperm cells
▫ Immature and nearly non-motile sperm
leave testes and are moved slowly through
the epididymis
▫ By day 20, sperm have gained the ability to
sperm
• Expels sperm with the contraction of
muscles in the epididymis walls to the vas
deferens
Ductus Deferens (Vas Deferens)
• Carries sperm from the epididymis to the
ejaculatory duct
• Moves sperm by peristalsis
• Ends in the ejaculatory duct which unites
with the urethra
Ductus Deferens (Vas Deferens)
• Ejaculation—smooth muscle in the
walls of the ductus deferens create
peristaltic waves to squeeze sperm
forward
• Vasectomy—cutting of the ductus
deferens at the level of the testes to
prevent transportation of sperm
Urethra
• Passageway
for both
urine and
semen
Seminal Vesicles
• Located at the base of the bladder
• Produces a thick, yellowish secretion (60%
of semen)
▫ Fructose (sugar)
▫ Vitamin C
▫ Prostaglandins
▫ Other substances that nourish and
activate sperm
Prostate
• Encircles the upper part of the urethra
• Secretes a milky fluid
▫ Helps to activate sperm
Bulbourethral Glands
• Pea-sized gland inferior to the prostate
• Produces a thick, clear mucus
▫ Cleanses the urethra of acidic urine
▫ Serves as a lubricant during sexual
intercourse
Penis
• Copulatory organ that delivers sperm to
female
• Contains spongy urethra composed of 3
cylindrical bodies of erectile tissue
▫ Connective tissue and smooth muscle with
vascular spaces
▫ Vascular spaces fill with blood during
erection
Semen
• Mixture of sperm and accessory gland
secretions
• Advantages of accessory gland secretions
▫ Fructose provides energy for sperm cells
▫ Alkalinity of semen helps neutralize the
acidic environment of vagina
▫ Semen inhibits bacterial multiplication
▫ Elements of semen enhance sperm
motility
Imbalances
• Testicular Cancer
▫ Affects one of every 50,000 males and most
common cancer among young males ages 1535
▫ Most common sign is a painless solid mass in
testis
▫ Risk factors in development:
 Nondescent of the testes
 Maternal exposure to toxins before birth
 Inflammation of the testis
Imbalances
• Prostate Cancer
▫ Most common cause of cancer death in men
after lung cancer
▫ Risk factors in development:
 Fatty diets
 Genetic predisposition
Imbalances
• PID (Pelvic Inflammatory Disease)
▫ Caused by infection that spreads
▫ Can cause scarring of the uterine tubes and
ovaries, which causes sterility
Imbalances
• Cerival Cancer
▫ Affects about 450,000 women each year,
killing almost half.
▫ Most common among women between the
ages of 30 and 50.
▫ Risk factors in development:
 Frequent cervical inflammations
 STD’s including genital warts
 Multiple pregnancies
Imbalances
• Breast Cancer
▫ Most common malignancy and 2nd most
common cause of cancer death of U.S. women
▫ 13% of women in the general population (132
out of 1000 individuals) will develop it
▫ Risk factors in development:
 Early menstruation and late menopause
 No pregnancies or first one late in life and no or
short periods of breast feeding
 Family history of breast cancer
 Hormone replacement therapy
Imbalances
• Breast Cancer
▫ BRCA1 and BRCA2 genes show mutations
which can trigger breast cancer
▫ Treatments include:
 Drug therapy
 Lumpectomy (only cancerous lump is removed)
 Mastectomy
Mammograms
Figure 16.14
Imbalances
• STDs
▫ The United States has the highest rate of infection
among developed countries
▫ Over 12 million people in the U.S., a quarter of
them adolescents, gets STDs each year
▫ They are the single most important cause of
reproductive disorders
Imbalances
• Gonorrhea
▫ Caused by a bacterium that invades the mucus
membranes of the reproductive and urinary
tracts
▫ Occurs most frequently in adolescents and
young adults
▫ Most common symptoms in males is painful
urination and discharge of pus from the penis
▫ Females can experience vaginal discharge,
uterine bleeding, and abdominal pain
Imbalances
• Gonorrhea
▫ Caused by a bacterium that invades the mucus
membranes of the reproductive and urinary
tracts
▫ Occurs most frequently in adolescents and
young adults
▫ Most common symptoms in males is painful
urination and discharge of pus from the penis
▫ Females can experience vaginal discharge,
uterine bleeding, and abdominal pain
Imbalances
• Syphilis
▫ Caused by a bacterium that is usually
transmitted sexually but can pass from an
infected mother
▫ After about 2 -3 weeks a red painless lesion
appears at the site of infection
▫ If untreated, a pink skin rash can occur and
fever and joint pain are common
▫ Disease enter latent period and then can only
be detected by a blood test
Imbalances
• Chlamydia
▫ Infects 4-5 million each year and responsible
for 20-50% of all cases of PID
▫ Symptoms include painful and frequent
urination, painful intercourse, vaginal and
penile discharge
▫ 80% of women do not experience symptoms
 Major cause of sterility
Birth Control Methods
• Surgical Sterilization
▫ Vasectomy
▫ Tubal ligation
• Hormonal Methods
▫
▫
▫
▫
“the pill”
Norplant implant
Depro
Vaginal ring
Birth Control Methods
• IUDs (interauterine devices)
• Coitus interruptus
• Induced Abortion
▫ RU 486
• Barrier methods
▫ Condoms
▫ Diaphragm
The Ovarian Cycle
• The total supply of eggs are present at
birth
• Ability to release eggs begins at
puberty
• Reproductive ability ends at
menopause
Uterine (Menstrual) Cycle
• 4 stages
▫ Menstrual Cycle
▫ Preovulatory Cycle
▫ Ovulation
▫ Postovulatory Cycle
Uterine (Menstrual) Cycle
• Menstrual phase
▫ Days 1–5
▫ Functional layer of the
endometrium is sloughed
▫ Bleeding occurs for 3–5 days
Uterine (Menstrual) Cycle
• Preovulatory Stage
▫ Days 6–14
▫ Regeneration of functional layer of the
endometrium
▫ Estrogen levels rise
▫ Ovulation occurs in the ovary at the end
of this stage
Uterine (Menstrual) Cycle
• Ovulation
▫ Release of the oocytes into the pelvic
cavity
▫ Usually occurs on day 14
Uterine (Menstrual) Cycle
• Postovulatory Stage
▫ Days 15-28
▫ Time between ovulation and onset of
next menstrual cycle
Ovarian Cycle
Figure 16.12c
Uterine (Menstrual) Cycle
Figure 16.12d
Human Development
• Fertilization
• Embryonic development
• Fetal development
• Childbirth
Fertilization
• The oocyte is viable for 12 to 24 hours after
ovulation
• Sperm are viable for 24 to 48 hours after
ejaculation
• For fertilization to occur, sexual intercourse
must occur no more than 2 days before ovulation
and no later than 24 hours after
• Sperm cells must make their way to the uterine
tube for fertilization to be possible
The Zygote
• First cell of a new individual
• The result of the fusion of DNA from
sperm and egg
• The zygote begins rapid mitotic cell
divisions
• The zygote stage is in the uterine tube,
moving toward the uterus
Cleavage
• Rapid series of mitotic divisions that
begins with the zygote and ends with the
blastocyst
• Zygote begins to divide 24 hours after
fertilization
• Three to 4 days after ovulation, the
preembryo reaches the uterus and floats
freely for 2–3 days
• Late blastocyst stage—embryo implants in
endometrium (day 7 after ovulation)
Inner cell
mass
Blastocyst
cavity
Cleavage
Trophoblast
(a) Zygote
(fertilized
egg)
(b) Early
cleavage
4-cell stage
(c) Morula
(d) Early
blastocyst
(b)
Fertilization
(a)
(e) Late blastocyst
(implanting)
(c)
Ovary
(d)
Uterine tube
(e)
Secondary
oocyte
Ovulation
Uterus
Endometrium
Figure 16.15
Developmental Stages
• Embryo—developmental stage until ninth
week
▫ Morula—16-cell stage
▫ Blastocyst—about 100 cells
• Fetus—beginning in ninth week of
development
Germ Layers
• Ectoderm
▫ Nervous system
▫ Epidermis of the skin
• Endoderm
▫ Mucosae
▫ Glands
• Mesoderm
▫ Everything else
Development After Implantation
• Chorionic villi (projections of the
blastocyst) develop
▫ Cooperate with cells of the uterus to
form the placenta
• Amnion—fluid-filled sac that surrounds
the embryo
• Umbilical cord
▫ Attaches the embryo to the placenta
Figure 16.17
Functions of the Placenta
• Forms a barrier between mother and embryo
(blood is not exchanged)
• Delivers nutrients and oxygen
• Removes waste from embryonic blood
• Becomes an endocrine organ (produces
hormones) and takes over for the corpus luteum
(by end of second month) by producing
▫ Estrogen
▫ Progesterone
▫ Other hormones that maintain pregnancy
The Fetus
• All organ systems are formed by the end of the
eighth week
• Activities of the fetus are growth and organ
specialization
• This is a stage of tremendous growth and change
in appearance
Photographs of a Developing Fetus
Figure 16.18a
Figure 16.18b
Table 16.1 (2 of 2)
Effects of Pregnancy on the Mother
• Pregnancy—period from conception until
birth
• Anatomical changes
▫ Enlargement of the uterus
▫ Accentuated lumbar curvature (lordosis)
▫ Relaxation of the pelvic ligaments and
pubic symphysis due to production of
relaxin
Effects of Pregnancy on the Mother
• Physiological changes
▫ Gastrointestinal system
 Morning sickness is common due to
elevated progesterone and estrogens
 Heartburn is common because of organ
crowding by the fetus
 Constipation is caused by declining
motility of the digestive tract
Effects of Pregnancy on the Mother
• Physiological changes (continued)
▫ Urinary system
 Kidneys have additional burden and
produce more urine
 The uterus compresses the bladder,
causing stress incontinence
Effects of Pregnancy on the Mother
• Physiological changes (continued)
• Respiratory system
 Nasal mucosa becomes congested and swollen
 Vital capacity and respiratory rate increase
 Dyspnea (difficult breathing) occurs during later
stages of pregnancy
Effects of Pregnancy on the Mother
• Physiological changes (continued)
▫ Cardiovascular system
 Blood volume increases by 25–40%
 Blood pressure and pulse increase
 Varicose veins are common
Childbirth (Parturition)
• Labor—the series of events that expel the infant
from the uterus
▫ Rhythmic, expulsive contractions
▫ Operates by the positive feedback mechanism
• False labor—Braxton Hicks contractions are
weak, irregular uterine contractions