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ReproductionReproduction
Male Reproductive SystemMale Reproductive System
Male Reproductive SystemMale Reproductive SystemStructure Function
Testis Produce sperm
Epididymis Are where sperm mature and are stored
Scrotum Sac that contains the testis; regulates the temperature for proper sperm production
Vas deferens Carries mature sperm from the epididymis to the urethra for ejaculation
Seminal vesicles Glands that produce and add seminal fluid to the semen
Prostate gland Gland that produces the majority of the seminal fluid
Penis Facilitates copulation
Urethra Tube through which semen exits the penis
TestosteroneTestosteroneA hormone produced by the testesPerforms a variety of functions in the
male◦ Promotion of secondary sex characteristics
Chest and facial hair Extra muscle development Deeper voice
◦ Controls the growth and activity of the male reproductive organs
◦ Enhances sexual libido◦ Enhances immune function◦ Adds protection against osteoporosis
Different tissues and sperm Different tissues and sperm productionproductionSperm cells are produced in the seminiferous
tubulesTravel to the head of the epididymis through
the vasa efferenta◦ Here they become mature and mobile◦ Account for 10% of ejaculate
Seminal vesicles produce the fluid in semen◦ Accounts of 80% of the ejaculate◦ Contains fructose for energy and prostaglandins
which cause contractions in the female to help the sperm reach the egg
Prostate add alkaline fluid◦ Helps neutralize the environment inside the female
Cowper’s glands◦ Produce a clear liquid that lubricates the penis and
facilitates copulation
Micrograph of the testisMicrograph of the testis
SpermatogenesisSpermatogenesis
The process of producing sperm
Done through the process of meiosis
Role of hormones in sperm Role of hormones in sperm productionproductionFSH
◦ Stimulates sperm production in the seminiferous tubules
◦ Stimulates division and maturation of sertoli cells
LH◦ Stimulates the interstitial cells to produce
testosteroneTestosterone
◦ Promotes spermatogenesis
Female Reproductive Female Reproductive SystemSystem
Female Reproductive Female Reproductive SystemSystem
Structure Function
Ovaries Produce estrogen; produce the eggs
Fallopian tubes Carry the egg to the uterus
Uterus Muscular structure where the egg implants and matures
Endometrium Vascular lining of the uterus
Cervix Allows sperm to enter; pathway to childbirth
Vagina Muscular tube; pathway from external genitals to cervix
Corpus luteum Area on ovary where ovulation occurred; produces progesterone
The menstrual cycleThe menstrual cycleControlled by 4 hormones
◦ FSH (follicle stimulating hormones) Stimulates follicle growth Stimulates estrogen secretion Stimulates progesterone secretion Surges cause ovulation Produced in the pituitary gland
◦ LH (luteinizing hormone) Surge in concentration causes ovulation Stimulates formation of the corpus luteum Produced in the pituitary
The menstrual cycleThe menstrual cycle◦ Estrogen
Stimulates thickening of the endometrium Promotes secondary sexual characteristics
(breast growth, widening of the hips) Inhibits secretion of FSH Stimulates secretion of LH Produced in the ovary in a growing follicle
◦ Progesterone Inhibits ovulation Maintains the endometrium Inhibits FSH Inhibits LH Produced in the ovary in the corpus luteum and
the placenta during pregnancy
The menstrual cycleThe menstrual cycle Cycle starts with a release of FSH from the pituitary
gland◦ Stimulates the ripening of a follicle
Growing follicle releases estrogen◦ Increase the lining of the endometrium◦ Inhibits the production of FSH◦ Stimulates the production of LH
LH stimulates the ovulation (release of the egg) and the formation of the corpus luteum (tissue located at site of egg release)
Corpus luteum produces progesterone which keeps the endometrium intact and inhibits FSH and LH
If fertilization and implantation do not occur the corpus luteum degenerates and the pituitary starts producing FSH again to start the process from the beginning
The ovaryThe ovary
The OvaryThe OvaryOvaries contain follicles in different stages of
developmentGerminal epithelium
◦ Functions to keep the tissues of the organ together and separate from the rest of the body
Primary follicles◦ Immature◦ Not currently active in the process of oogenesis
Graafian follicles◦ Mature follicles◦ Function is to support the growth of the oocyte
(eventually turns into the egg)Secondary oocyte
◦ Oocyte that has undergone meiosis I
OogenesisOogenesisBegins in the ovaries of the female fetus
before birthFinal development occurs in the ovaries of
the adult femaleDevelopment of the primary follicle
◦ Germinal epithelium divides by mitosis◦ Forms numerous oogonia◦ Oogonia migrate to the connective tissue of the
ovary where they grow and enlarge and become oocytes
◦ Each oocyte is surrounded by layers of follicle cells◦ Process ceases during mid development of the fetus
several million exist in each fetus By puberty only 250,000 are still viable
OogenesisOogenesisMature follicles
◦ From puberty (approx. 11 yrs of age) to menopause (approx. 55 yrs of age) several follicles start growth each month but only one usually matures fully
◦ Follicle gets larger and moves to the outer edge of the ovary
◦ Undergoes Meiosis I with unequal cytoplasmic division Creates one oocyte and one non functional polar body
Secondary Oocyte◦ Second meiotic division begins…does not complete
until fertilization◦ Egg is released from the ovary during ovulation
Follicle wall ruptures….explains the pain some women feel
Sperm and eggSperm and egg
Head w/ haploid nucleus
mitochondriaFlagellum in tail
acrosome
Jelly coatProtein receptors
Egg plasma membrane
sperm vs. egg productionsperm vs. egg productionSimilarities
◦ Both produce haploid cells by meiosis◦ Both take place in the gonads◦ both are controlled by hormones
Differences◦ Spermatogenesis produces 4 sperm each time
while oogenesis produces only 1 egg◦ Formation of mature sperm continually occurs while
eggs only mature once a month (on average)◦ Sperm formation never stops, egg formation ends
at menopause◦ Sperm can be released at anytime while eggs are
released only once a month
FertilizationFertilizationRefers to the fusion of the sperm and eggGenerally occurs in the fallopian tubesAcrosome reaction
◦ The acrosome of the sperm contains an enzyme which allows it to enter the corona radiata
Penetration of the egg◦ Special receptor sites bind to the sperm
allowing it to enterCortical reaction
◦ When the head fuses with the secondary oocyte special lysosomes thicken the zona pellucida coat preventing other sperm from entering
Embryo developmentEmbryo development After fertilization the chromosomes of the male and
female line up at the equator of the egg cell for the first mitotic division◦ Not followed by growth◦ Called cleavage
Several cleavage divisions occur◦ End in a solid ball of cells called a morula◦ Reaches the uterus 4 days after fertilization
Development of the blastocyst◦ Created by several unequal divisions◦ Cause a fluid filled space to form in the middle of the ball◦ Cells on the outside are called trophoblast which embeds
in the endometrium Called implantation Turns into trohpoblast villi which will transfer nutrients from
the endometrium to the embryo until the placenta develops (at about 2 weeks)
HCGHCGHCG
◦ Human chorionic gonadotropin◦ Released by the trophoblastic cells after
they embed in the wall of the endometrium◦ Sustains the corpus luteum which
continues then to produce progesterone maintaining the endometrium
Eventually replaced by the placenta producing its own progesterone
Excreted in the urine and detected by a pregnancy test
The PlacentaThe PlacentaActs as an interface between the mother and
the baby◦ Oxygen and food diffuse from the mother to the baby◦ Waste diffuses from the baby to the mother◦ Mother and baby have independent circulation and
the blood does not mixTakes over progesterone production
◦ Maintains the pregnancy by reducing contractions◦ Reduces the chance that the mother’s body will have
an immune system reaction to the pregnancy◦ A drop in levels at the time of birth allows for lactation
Produces estrogen◦ Stimulates the growth of muscles in the uterus◦ Stimulates growth of the breasts◦ Levels drop near the time of birth
Amniotic sac and fluidAmniotic sac and fluidAmniotic sac
◦Contains the baby and the amniotic fluid◦Protects the baby against infection
Amniotic Fluid◦Buffers the baby from shock◦Protects the baby from mechanical harm◦Babies also drink the amniotic fluid to
practice swallowing…they also pee in it◦Constantly made and filtered by the
mother
Baby – Mother exchangeBaby – Mother exchangeFrom fetus to mother From mother to fetus
Carbon dioxide Oxygen
Urea Nutrients
Water Water
Hormones Hormones
Vitamins and minerals
Alcohol, nicotine, some drugs
The birth processThe birth process Approximately 38 weeks after conception the fetus is
ready to be born Starts the first stage of labor
◦ Can take a lot of time Progesterone levels drop
◦ Allows the uterus to have regular contractions Baby signals the release of prostaglandins
◦ Locally produced hormones◦ Initiate contractions in the uterine wall◦ Push the babies head against the cervix causing it to
dilate◦ Message is received by nerve ending in cervix and sent to
the pituitary gland Brain releases oxytocin
◦ Causes contractions to become longer and stronger◦ Babies head pushes harder against the cervix triggering
the release of more oxytocin
Birth Birth Second stage of labor
◦Occurs when the cervix is fully dilated
◦ usually takes no more than one hour◦Powerful contractions push the baby
out of the mother’s bodyThird stage of labor
◦Positive feedback loop is broken◦Placenta is expelled from the uterine
wall
IVFIVF Stands for in vitro fertilization Egg and sperm are joined in a petri dish and then
fertilized eggs are implanted into the female Eggs/sperm can belong to the couple involved or can
be donated◦ Woman who has the eggs gets injections of hormones to
hyper stimulate the ovary so that more than one egg will be released
◦ The eggs are then surgically removed A needle is placed into the ripe follicle and carefully removed Procedure is repeated until all the ripe eggs are removed
Egg and sperm are either mixed in a petri dish or the sperm is actually injected into the egg◦ The embryo is allowed to grow and then graded on its
quality◦ Those of good quality are either implanted into the uterus
or frozen for later use
Risks of IVFRisks of IVF IVF by passes the natural selection of only
healthy eggs and healthy sperm◦ Some evidence that genetic abnormalities are
higher in IVF children than in the general publicThe stimulation of the mothers hormones
can damage the ovary and her health Implantation of multiple embryos has
increased the number of multiple births◦ Human body is not designed to carry more than
one baby◦ Lasting long term negative effects on the mother◦ Increased risk of pre-maturity and developmental
problems
Ethical IVF factorsEthical IVF factorsCreation of life in a laboratoryFreezing of embryos (and later their disposal)Possibility of selecting embryos
◦ Embryos are regularly screened for genetic abnormalities
Birth mother/father may not be genetic parentsPossibility of creating embryos for medical
researchPossibility of engineering embryosAvailable only to the rich (its super expensive
and not often covered by insurance)◦ Over 10 million children under 5 die each year for lack
of basic needs◦ Reduces the adoption rate