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