Hormones Reproduction In Humans Sex Growth Hormones Our

Hormones & Reproduction In 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

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 Urinary Bladder Scrotum The Sperm Head Prostate Epididymus Testicle Urethra Penis Midpiece Tail (Flagellum)

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 Ovary Uterus Cervix Ovum Vagina 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 • The process of making eggs is called oogenesis. releases progesterone maintains uterus lining produces estrogen

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

Feedback Female reproductive cycle egg matures & is released (ovulation) estrogen builds up uterus lining corpus luteum ovary progesterone FSH & LH maintains uterus lining fertilized egg (zygote) yes pituitary gland pregnancy Gn. RH hypothalamus no corpus luteum breaks down progesterone drops menstruation HCG corpus luteum progesterone maintains uterus lining

The Cycle With No Fertilization

FSH & LH releases egg

Estrogen increases uterine lining

endometrium

Progesterone sheds lining

What if Fertilization Occurs? The menstrual cycle stops and the body works to take care of the developing embryo!

The Cycle With Fertilization

HCG keeps progesterone high (positive feedback)

Progesterone maintains 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.