Hormones & ReproductionIn Humans

Sex & Growth Hormones

• Our hormones are determined by our chromosomes.

– Males are XY– Females are XX

What do these hormones do?

• Large scale body changes– how do they work

• turn genes on• start new processes

in the body by turning genes on that were lying “dormant”

Pituitary gland hormones

• Sex & reproductive hormones– FSH

• follicle stimulating hormone• stimulates egg & sperm production

– LH• luteinizing hormone• stimulates ovaries & testes• prepares uterus for fertilized egg

– oxytocin• stimulates childbirth contractions• releases milk in nursing mothers

– prolactin• milk production in nursing mothers hormones hormones

Reproductive hormones• Testosterone

– from testes– sperm production &

secondary sexual characteristics

• Estrogen– from ovaries– egg production, preparing

uterus for fertilized egg & secondary sexual characteristics

Male Reproductive System

Male Reproductive System

• The male reproductive system has both internal and external organs.

Seminal Vesicle

Ampulla of Ductus

Deferens

Vas Deferens

Prostate

Epididymus

Testicle

Penis

Urethra

The Sperm

Head

Midpiece

Tail (Flagellum)

Urinary Bladder

Scrotum

Male Reproductive System• Testes

– make sperm via meiosis. The testes are also responsible for producing testosterone.

- Testosterone is responsible for many of the "male" characteristics.

• Scrotum – sac that holds testicles outside of

body

Sperm Production

• The production of sperm is called spermatogenesis.

• Nearly 200-300 million sperm are deposited in the female during fertilization.

• Males produce around 100 million sperm per day.

Spermatocytes

sperm

Sperm Production

• Semen – A mixture of sperm and

fluid. Leave the body through the urethra, which is the same tube that carries urine outside the body.

Male Reproductive System• Epididymus

– collects mature sperm which is eventually propelled through the vas deferense

• Vas deferens – tube where sperm travel to the outside of the body.

• Vasectomy– the tube is cut to prevent sperm

leaving (and fertilizing an egg)

- This procedure can be

done right in the doctor's office

Male Reproductive System

• Prostate, seminal vesicles, Cowper’s (bulbourethal) glands

– nutrient rich fluid to feed & protect sperm

Female Reproductive

System

Fallopian Tubes

Uterus

Ovary

Cervix

Vagina

Ovum

Corpus Luteum

Ovary

Female reproductive system

• Ovaries– produces eggs via meiosis & hormones

• Uterus– nurtures fetus; lining builds up each month

Female reproductive system

• Fallopian tubes– tubes for eggs to travel from ovaries to uterus

• Cervix– opening to uterus, dilates 10 cm for birthing baby

• Vagina– birth canal for birthing baby

Female reproductive system

Egg maturation in ovary

releasesprogesterone

maintainsuteruslining

produces estrogen

• The process of making eggs is called oogenesis.

The Menstrual Cycle

Why a menstrual cycle?

• Females are the vessels for the production of offspring. Their bodies prepare for pregnancy to ensure that the species continues on to the next generation.

• The menstrual cycle is completely regulated by hormones. These hormones work on a 28 day cycle in preparation for ovulation so fertilization can occur.

• Ovulation – a 2-3 day period during the cycle when the egg is released. (fertilization most likely to occur)

Hormones in Menstrual Cyle• FSH & LH

– released from pituitary– stimulates egg development & hormone release– peak release = release of egg (ovulation)

• Estrogen – released from ovary cells around developing egg

– stimulates growth of lining of uterus

– decreasing levels causes menstruation

• Progesterone – released from “corpus luteum” in ovaries

• cells that used to take care of developing egg

– stimulates blood supply to lining of uterus

– decreasing levels causes menstruation

corpusluteumovary

Female reproductive cycle

pregnancy

maintainsuterus lining

no

yes

Feedback

estrogenegg

matures &is released(ovulation)

builds up uterus lining

FSH & LH

progesterone

progesterone

fertilized egg(zygote)

HCG

corpus luteum breaks downprogesterone drops

menstruation

corpusluteum

maintainsuterus lining

GnRH

pituitarygland

hypothalamus

The Cycle With No Fertilization

FSH & LHreleases egg

Estrogen increases

uterine lining

endometrium

Progesteronesheds lining

What if Fertilization Occurs?

The menstrual cycle stops and the body works to take care of the developing embryo!

The Cycle With Fertilization

HCGkeeps

progesterone high

(positive feedback)

Progesteronemaintains

uterine lining

Any Questions??

Why a menstrual cycle?• Menstrual cycles occur in humans and primates, there are

very few other mammals that have actual menstrual cycles.

• In other mammals it is referred to as estrus, which is actually somewhat different than a menstrual cycle.

• One difference is that animals that have estrus cycles reabsorb the endometrium (uterine lining) if conception does not occur during that cycle.

• Animals that have menstrual cycles shed the endometrium through menstruation instead.

Why a menstrual cycle?• Another difference is sexual activity. In species with estrous

cycles, females are generally only sexually active during the estrus phase. This is also referred to as being "in heat.“

• In contrast, females of species with menstrual cycles can be sexually active at any time in their cycle, even when they are not about to ovulate.

*Interesting fact – humans are one of the few animals that do not have some kind of visible obvious display of fertility.

Evolutionary biologists suggest this trait evolved as a way to keep males interested for more than just the fertile period, increasing the likelihood of male parental care of offspring.