Reproductive system
Reproductive system
• Gametic meiosis
• All Animal
Kingdom
• Gametes made by
diploid organism
directly by meiosis
• Syngamy makes
zygote, which
develops into adult
Fertilization
• External: Eggs and sperm released outside of
bodies of male/female
– Most marine bony fish, most amphibians.
Fertilization
• Internal: Sperm deposited inside body of
female
– Reptiles, birds, mammals
Vertebrate Reproduction
(Internal fertilization)
• Oviparity: Eggs fertilized internally. Deposited
outside mother’s body to develop.
– Some cartilagenous fish, some bony fish, some
amphibians, most reptiles, all birds, few mammals
(monotremes).
Vertebrate Reproduction
Ovoviviparity: Eggs fertilized internally, remain in
mother. But rely on yolk for nourishment.
Young developed and hatched when released.
– Some bony fish, some cartilagenous fish, some
amphibians, many reptiles
Salamandra
female giving
birth to larvae
Vertebrate Reproduction
• Viviparity: Young develop in mother and obtain
nourishment mainly from mother (rather than
____________).
– Most cartilagenous fishes, few bony fishes, some
amphibians, few reptiles, almost all mammals.
Reproductive system
• Here, we emphasize human system (rat seen
in lab)
• Start with male, move to female
Reproductive system
• Male:
• 1) Makes gametes (sperm)
by meiosis
• 2) Delivers sperm to
vagina in female system
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Reproductive
system
Sperm cell:
Flagellum to swim with
Mitochondria for energy
Nucleus (haploid) in head
Acrosome: special ____________, contains enzymes that
help penetrate layers around egg.
Reproductive system
• Male reproductive system
• 1) Testes (plural: males have 2). Make sperm and
androgens (male hormones, such as testosterone)
• In bag called scrotum.
Reproductive system
• 1) Testes: Seminiferous tubules
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1) germinal cells divide (mitosis) to produce primary spermatocyte
2) primary spermatocyte divides by meiosis to make 4 spermatids
3) Spermatids develop into sperm
4) Process aided by ______________ cells, which help spermatids
transform into sperm.
Reproductive system
• Making sperm: a fulltime job
• 100-200 million formed per day, takes 100 days to
make them
• Influenced by temperature
• Normal testis temperature is 34 degrees, compared to
37 degrees internal body temperature.
Reproductive system
• Male reproductive system
• 2) Ducts to carry sperm. Epididymis: collecting duct
at testis. Vas deferens: duct from epididymis to
seminal vesicle. Ejaculatory ducts: from seminal
vesicle to prostate gland.
Reproductive system
• Male reproductive system
• 3) Accessory glands (package sperm). Seminal
vesicles: store sperm. Bulbourethral gland and
prostate gland (produce ____________).
Reproductive system
• Male reproductive system
• 3) Accessory glands (package sperm).
• Semen: fluid that enhances longevity of sperm
Reproductive system
• Semen: fluid that enhances longevity of sperm
• Contains:
– water
– sugars (fructose and glucose): used by sperm for energy
– __________________: neutralizes acidity from urine in
male urethra and acidic conditions in vagina
– prostaglandins: hormones that stimulate contractions of
smooth muscle in female system
– vitamins, minerals, amino acids, etc.
Reproductive
system
Male reproductive system
•
• 4) Penis: copulatory organ, delivers sperm to __________
of female
• When male excited, blood flow out decreased. Blood fills 2
corpora cavernosa (spongy tissue bodies on each side of
penis) during erection.
Reproductive system
• Female reproductive system
• 1) Produces gametes (eggs)
– actually oocytes: cells ______________ to being eggs!
• 2) Also nourishes embryo during gestation period
(time from fertilization to birth: 9 months for human).
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Reproductive system
Female reproductive system
1) Ovary (2 of them): Where oocytes formed
2) Fallopian tube (2 of them): connect ovary to uterus
3) Uterus: where fertilized egg implants and embryo
develops
Reproductive system
• Female reproductive system
• 4) Cervix: entrance to uterus
• 5) Vagina: connects uterus to outside body
Reproductive system
• Making oocytes in ovary
• Process starts before birth, when germinal cells
produce primary oocytes. These start meiosis I but
stop at prophase I at time of birth as primary follicles.
Reproductive system
• Follicles contain oocyte and cluster of other special cells
• Each female has about 2 ____________ follicles at birth.
Reproductive system
• Once puberty begins, one primary follicle matures
each month during menstrual cycle.
• Maturation, called ______________, ruptures follicle
and releases secondary oocyte.
Reproductive system
• In secondary oocyte, meiosis I completed and meiosis
II started. Stops at metaphase II.
• Will complete meiosis II to make egg only if
fertilized by sperm!
Reproductive system
• Note that follicle cells stay alive and secrete
hormones for a time after secondary oocyte released
• Become corpus luteum.
Reproductive system
• Hormones made by corpus luteum increase thickening of
lining of uterus
• This readies uterus in case fertilization occurs
• Oocyte moves down Fallopian tube by _________ lining
tube.
Reproductive system
• Menstrual cycle (takes about 28 days)
Reproductive system
• 1) pituitary gland (in head under brain) secretes
follicle stimulating hormone (FSH)
• 2) Follicles in ovaries begin to develop (only one
continues to end)
Reproductive system
• 3) Follicles release _____________: uterus lining
starts to thicken
Reproductive system
• 4) Estradiol stimulates more FSH. Also luteinizing
hormone (LH) made by pituitary.
• 5) Peak of FSH and LH at day 14 causes ovulation:
release of secondary oocyte from 1 follicle.
Reproductive system
• 6) Remnants of follicle are corpus luteum
• 7) Secretes estradiol and progesterone. They influence
pituitary to decrease FSH and LH production. Follicles
stop developing.
Reproductive system
• 8) After several days, corpus luteum starts to degenerate
• 9) Estradiol and progesterone levels drop
Reproductive system
• 10) Uterine lining(endometrium) sloughs off (period starts)
• 11) Decrease in estradiol and progesterone cause pituitary to
increase _______ production
• 12) Cycle starts again.
Reproductive system
• If fertilization happens:
• Embryo implants in uterine wall
• Eventually, placenta takes over production of
estradiol and progesterone. Lining stays thickened
(no period). No more follicles develop.
Reproductive system
• Lost along the way: fertilized oocyte can get outside
system and create ___________ pregnancy (implants
in wrong places)
• Problem: won’t develop normally. Must be removed
or can kill mother.
Manipulating
the
system
• Birth control (or
how not to
make a baby)
•
See also:
www.plannedparenth
ood.org
Manipulating the system
• 1) Abstinence.
• Variation: rhythm method. Time between _________
release and arrival in uterus about 5 days (after
ovulation). Sperm can remain alive in woman for
several days.
Manipulating the system
• 2) Sperm blockage (condom, cervical cap or
diaphagm)
Manipulating the system
• 3) Sperm destruction
• washing sperm out (douche)
• spermicide foams/jellies
Manipulating the system
• 4) Preventing ovulation: the pill and implants of various
types. Contain chemicals that act like ______________
(prevent follicle development).
Manipulating the system
• 5) Preventing embryo implantation: IUD (intrauterine
device). Irritates uterine lining.
Manipulating the system
• 6) Sterilization
– vasectomy for man (cutting/tying vas deferens)
– cutting/tying Fallopian tubes for woman.
Manipulating the system
• Fertility clinics (how to make a baby)
• _______% of couples have difficulty conceiving a
child
• About half cases due to male infertility, other half
female infertility
Manipulating the system
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Male infertility:
Large numbers sperm needed due to barriers in journey
1) long distance (sperm swim 3 mm/hour)
2) acidic conditions in vagina
3) most are active for <48 hours
Typically many hundreds of millions deposited, only
few hundred reach fallopian tubes
• So, numbers matter (Normal is____ million sperm/ml.
Low is <20 million/ml).
• Also vigor (activity level) and appearance
(morphology) of sperm matter.
Manipulating the system
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Fertility clinics (how to make a baby)
Female infertility:
______________ problems
Anatomical problems
Manipulating the system
• For both men and women: age ___________ fertility