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Transcript
BIOLOGY 12
Reproductive System
Introduction to the
Reproductive System
http://www.youtube.com/watch?v=444fTSTuhjg&feature=related
Introduction
• We humans like all mammals, have
internal fertilization and development.
• This requires specialized organs for
both sexes.
Male Reproductive System
•Testis – 2 oval shaped glands
outside the body sperm and
hormone production
•Seminiferous tubules – 3 coiled
tubes approx. 250m in length
which carry out meiosis
spermatogenesis / sperm
production
•Interstitial cells cuboidal cells
surrounding the seminiferous
tubules which are responsible
for producing testosterone
•Scrotum – thin layer of skin
(sac) containing testis
•Epididymis – tube just outside
the testes where sperm is
stored and matures.
Testis
Seminiferous Tubules
• Vas deferens (ductus deferens) small muscular tube
leaving the testicles conducts semen from epididymis
• Seminal vesicle, prostate gland, and Cowpers
gland (bulbourethral gland) – all three are glandular
organs PROSTATE (largest) contribute to seminal fluid
(contents of semen to be discussed later)
• Penis – erectile tissue (spongin) copulatory organ
• Glans penis – end of the penis containing large number of
sensory receptors stimulation
• Foreskin – thin layer of skin over glans protection
• Urethra – muscular tube conducts semen and urine
• Corpus cavernosum – contains spongin becomes
engorged with blood when vein is constricted
• Urinary bladder – hollow muscular organ holds urine
Male Sexual Response
• Upon sexual arousal, the primary response is to
have the penis become erect.
• This is necessary to achieve internal fertilization.
• Upon arousal, NO (nitrogen oxide) is released
from cells at the base of the penis.
• Blood vessels dilate allowing blood to flow into
the corpus cavernosum.
• This is called vasocongestion.
• Once the penis is erect, coitus, which is the
insertion of the penis into the vagina can occur.
• The erection is maintained until an orgasm is
reached.
• The penis contains a
tissue along the top of
made of spongin and
cartilage.
• This engorgement
creates pressure on the
penal vein, closing it
resulting in the erection.
• This continues as long
as the tissue is
stimulated by the
parasympathetic
nervous system to keep
releasing NO.
SPERMATOGENESIS
The Sperm Cell
• Smallest cell in the body - contains three
regions:
A. The head: made of the acrosome and the
haploid nucleus.
B. The Mid Piece: containing many
mitochondria.
C. The Tail: - a flagellum (9 x 2 pattern of
microtubules).
Male Hormone Regulation
• The Interstitial cells between the
seminiferous tubules begin to secrete
Testosterone from puberty on.
• This is responsible for male secondary sex
traits and the male sexual responses.
HORMONE CONTROL
Two pituitary hormones regulate male
reproductive physiology:
1) Follicle Stimulating Hormone (FSH)
• FSH is released from the anterior pituitary
and targets the seminiferous tubules
initiating spermatogenesis.
2. Lutenizing Hormone (LH)
• Also released by the anterior pituitary but
it targets the Interstitial (Leydig) cells to
produce testosterone.
• Both pituitary hormones are regulated by
negative feedbacks.
Negative Feedback LOOP
Gonadotropic
releasing hormone
Follicle stimulating hormone
Leutenizing hormone
Increases sperm production
Increases testosterone
TESTOSTERONE
• The effects of testosterone are:
Increase penis growth
Facial, body, pubic and axillary hair
Enlarged larynx
Bone and muscle growth
Increased sex drive
Acne
The Female System
The female system is actually a dual
system: reproduction and providing an
environment for development of the fetus
Human Ovary and Fallopian Tube
Human Uterus: l.s.
FEMALE REPRODUCTIVE
SYSTEM
Female Reproductive Organs
ANATOMY / PHYSIOLOGY
• Ovaries – glandular organs (gonads) size of
•
•
•
•
•
small lemons developing eggs (oogenesis), and
produces sex hormones
Uterus – strong muscular organ, holds the
developing fetus
Endometrium ( uterine lining) nourishes the
developing embryo
Cervix – opeining to the uterus forms a plug
holding in the amniotic fluid during pregnacy
Vagina – muscular organ copulation and birth
canal
Labia majora, labia minora – outer folds of
skin forming the vulva protection
• Clitoris – organ of stimulation similar to
the glans penis in males
• Bartholin’s gland aids in lubrication prior
to orgasm
• Fimbrae – sweep egg up into fallopian
tubes when the ovary ruptures and
releases egg
• Fallopian tubes (oviducts) lined with tiny
ciliated cells which sweep egg and usually
site of fertilization
• Urethra – conducts urine from bladder
• Urinary Bladder – holds urine
Ovarian cycle is divided into 2 phases;
1) Follicular Phase where the egg matures
and is released from the ovary
2) Luteal Phase following the release of the
egg, the corpus luteum forms and
continues to release the hormone
progesterone which is responsible for
maintaining the endometrium lining.
OVARIAN CYCLE
1. Primary follicle containing an “oocyte” egg
begins to produce sex hormone estrogen
2. Secondary follicle containing primary oocyte
continues to develop.
3. Graafian follicle matures
4. Ovulation occurs when the Graafian follicle
ruptures releasing the oocyte.
5. Corpus luteum produces the sex hormone
progesterone and estrogen.
6. Corpus luteum gradually disinterates if the
egg is not fertilized.
 The Reproductive Cycle of the Human Female
 Menstrual cycle: changes that occur in the
uterus.
 Day 1: the first day of menstruation.
 Menstrual flow phase.
 Menstrual bleeding.
 Usually lasts for a few days.
 Proliferative phase.
 Regeneration and thickening of the
endometrium.
 About 1 – 2 weeks in duration.
 Secretory phase.
 Continued endometrial thickening, increased
vascularization of the endometrium, endometrium
develops glands that secrete a glycogen-rich fluid, and
a duration of about 2 weeks.
• If, by the end of the secretory phase, an embryo has
not
implanted in the uterus a new menstrual flow
commences.
Fig. 46.15d
Hormonal Control
Hormonal coordination of the menstrual
and ovarian cycles involves five hormones.
Gonadotropin releasing hormone
(GnRH) secreted by the hypothalamus.
Follicle-stimulating hormone (FSH)
secreted by the anterior pituitary.
Luteinizing hormone (LH) secreted by
the anterior pituitary.
Estrogens secreted by the ovaries.
Progesterone secreted by the ovaries.
GnRH stimulates secretion of small
amounts of FSH and LH.
FSH stimulates the growth of immature
ovarian follicles.
The growing follicles secrete small
amounts of estrogens.
Inhibits secretion of FSH and LH.
FSH and LH levels remain relatively low.
The rate of secretion of estrogens by the
growing follicle rises steeply.
Stimulates the secretion the GnRH.
Stimulates the secretion of FSH and LH.
LH secretion is especially high.
LH induces the final maturation of the follicle
and ovulation.
The follicular phase of the ovarian cycle is
coordinated with the proliferative phase of the
menstrual cycle.
Secretion of estrogens during the follicular
phase stimulates endometrial thickening.
Negative feedback Loop
Estrogen / Progesterone

Secondary Sex Characteristics
Breast growth
Mensturation
Pubic hair
Widening of hips
Acne
Distribution of fat
Mood swings
Developing
Oocyte
Menopause
Cessation of ovarian and
menstrual cycles.
 Usually occurs
between ages 46 and
54.
 Due to ovaries
decreased
responsiveness to
gonadotropins.
The Female System
B. Fertilization
• Occurs in the top one third of the Fallopian
tubes.
• Once ovulated, the egg is only viable for
about 24 hours if not fertilized.
• Events of fertilization will be studied in
detail when we do development next.
The Female System
C. Contraception
• Except for condom, all are female
directed.
i. The Pill: 2 types
• Estrogen Pill: causes negative feedback
on pituitary production of FSH - therefore,
the follicle doesn’t develop in the ovary.
• Progesterone Pill: feeds back upon LH
production - no LH surge - no ovulation.
The Female System
ii. The Intra-uterine Device
• Placed in uterus - prevents embryo from
implanting.
• May also be spermicidal.
iii. Rhythm method:
• Based upon avoiding sex during fertile
periods of menstrual cycle.
The Female System
iv. Tubal Ligation
• Involves surgery to cut a short section out
of each fallopian tube to prevent egg
getting to sperm.
• Male equivalent is vasectomy.
v. Diaphragm
• Used with foams and gels to act as
physical barrier of sperm into uterus.
The Female System
3. Implantation and Pregnancy
• After fertilization, the zygote continues to
move down the fallopian tube.
• As it does, development begins (details
later).
• It takes the embryo 7 - 12 days to get to
the uterus and implant in the
endometrium.
Cleavage to Blastula
Implantation
The Female System
• As it implants, it secretes a hormone
called Human Chorionic Gonadotropin
(HCG).
• This acts like LH and continues to
stimulate the corpus luteum to secrete
progesterone.
• If this didn’t happen, menstruation would
happen with the loss of the endometrium
and the embryo in it.
• HCG can be detected in the mothers
urine.
The Female System
• Progesterone also triggers other
anatomical and physiological changes in
the mother.
• This includes: breast development, uterine
growth, and placental development.
Conception to BIRTH
http://www.youtube.com/watch?v=AoisqOGQIVE&feature=r
elated
Development
Period of the Embryo
• For the first three months, organogenesis occurs
and it is termed an embryo.
• This is a 6 week embryo.
Development
Period of the Fetus
• During the second trimester, HCG
declines and the placenta secretes
its own progerestone.
• This is the period of the fetus
marked by growth of all the organs.
• This is a 4 month fetus.
Development
Period of the Baby
• The third trimester, period of the baby, is
marked by growth and maturation of all
organs and organ systems.
• The baby is capable of life outside the
womb during this period.
A. Labor: secretions of oxytocin from the
posterior pituitary cause the cervix to
Birth
contract and open.
• When dilated to 10 cm., the next phase
begins.
B. Birth of the baby:
• Typically delivered head first.
Postive Feed back loop during
LABOUR
C. Delivery of the
Afterbirth
• About half hour
after the baby is
born, the uterus
contracts again to
expel the placenta
and membranes.
• The uterus then
contracts tightly to
seal off all the
broken capillaries.
Reproductive Diseases
1. AIDS (Acquired Immunity Deficiency
Syndrome)
• Caused by the Human Immunodeficiency
Virus.
• HIV positive means the virus is present.
• Transmitted through sexual contact via
mucous membranes
• Is actually a fragile virus that does not
live long outside of a host.
• Can cross the placenta.
• Common in drug addicts sharing
needles.
• Drug cocktails are prolonging the life of
AIDS victims but there is no cure and
death from it is inevitable.
2. Genital Herpes
• Most common sexually transmitted
disease.
• Caused by Herpes simplex virus.
• Causes blisters, ulcers, severe itching,
fever, and painful urination 2 - 20 days
after infection.
• Heals by itself but is still very
contagious. Can recur anytime and is
very difficult to get rid of.
Genital Herpes
Reproductive
Diseases
3. Gonorrhea - caused
by a bacteria
• In males, results in a
yellowish discharge of
pus from penis painful urination.
• In females, effects
less obvious until fully
infected.
Reproductive Diseases
• Infects vagina and uterus and can cause
PID - Pelvic Inflammatory Disease - which
can lead to major problems as well as
permanent sterility.
• Baby can be infected during birth - eyes.
• Easily treated with antibiotics.
Reproductive Diseases
4. Chlamydia - small
bacterium
• Effects are similar to
gonorrhea but less
severe and often not
diagnosed or
treated.
• Frequent cause of
female sterility.
A leading cause of blindness in
children. Picture shows clouding
of cornea due to chlamydia.
Reproductive Diseases
5. Syphilis - spirillum
bacteria.
• A most ancient
disease. Picture
shows ancient skull
with damage due to
syphilis
First Stage: chancre
sore at site of
infection.
Primary Syphilis: Chancre sores
Chancre on penis
on labia
Secondary Syphilis
• Second Stage: nonitchy rash over body.
Tertiary Syphilis
Third Stage: Tertiary
Syphilis
• Large ulcerated sores
over body and on
internal organs.
• Attacks nervous
system - insanity.
• Eventually, leads to
death.
Tertiary Syphillis
• Syphilis is a
scourge of children
worldwide.
• It is almost
epidemic in Africa.
• Still common in
North America.