*Human Reproduction

*Human Reproduction

*Humans, like many living things, reproduce by Sexual Reproduction.

*This is when 2 organisms combine their genetic information to make a new organism

*This method involves meiosis

*This is different from Asexual Reproduction

*When a single organism uses its genetic information to make an offspring

*This does not involve meiosis

*Human Reproduction

*In order to sexually reproduce, we need meiosis as it makes gametes.

*Male gametes are sperm

*Female gametes are ovum or eggs

*In humans, gametes are made in the gonads.

*Male gonads are the testes

*Female gonads are the ovaries

*Gametogenesis

*So how do these gametes form?

*It all happens through meiosis within the gonads.

*This process is called gametogenesis

*Spermatogenesis in men

*Oogenesis in women

*Spermatogenesis

*In order to understand how sperm are made, we need to understand a little about male anatomy.

*I apologize for the awkwardness of the next slide…

*Male Anatomy

*The Male Reproductive System

*Penis – the male reproductive organ.

*Urethra – The tube that carries urine and semen out of the penis

*Testicle – where sperm are produced.

*Epididymis – where sperm mature and are stored

*Vas Deferens – tube that carries mature sperm to the urethra

*Prostate Gland – creates a fluid that is added to sperm to make semen. Acts as a valve that allows semen to pass through.

*Seminal Vesicle – add a fluid to sperm to make semen. Fluid is a nutrient and aids in motility.

*Testes*The testes are the site of spermatogenesis

*They are housed within the scrotum, a sack made of skin that keeps the testes cool.

*This is because spermatogenesis works best at a temperature slightly lower than body temperature

*Semen

*Sperm mature in the epididymis

*At the time of ejaculation, the sperm exit the body*Ejaculation – when the prostate

gland allows sperm to exit through the urethra

*During ejaculation, the sperm mix with liquids from the prostate gland and the seminal vesicle

*This liquid is called semen

*Semen – a liquid with nutrients that helps lubricate the sperm and provide them with energy as they travel

*Female Reproductive

System

*Now that we understand the male reproductive system, let’s take a look at the female reproductive system.

*The Female Reproductiv

e System

•Cervix – directs sperm during sexual intercourse. Allows flow of endometrium during menstruation by opening slightly

•Vagina –The vagina is a muscular, hollow tube that extends from the vaginal opening to the cervix

•Fallopian Tubes – Transport the egg from the ovary to the uterus. Where egg is fertilized

•Ovaries – Female organ that produces eggs

•Uterus – Accepts the fertilized egg. Where the embryo develops. Strong muscular walls help push child out during childbirth

*Oogenesis

*Oogenesis is meiosis in the female body

*It creates 1 egg cell and 3 polar bodies (non-useful cells)

*This takes place in the ovaries

*Oogenesis begins a cycle in the female body to prepare it for fertilization

*This process is called the Menstrual Cycle

*Meiosis in the Gonads

*The Menstrual Cycle

*Before reproduction happens, the female body prepares in case of fertilization

*This process of the body preparing itself is called the Menstrual Cycle

*It is a regular cycle that typically lasts 28 days in most human women.

*Menstrual Cycle

*Stage 1 – Menstruation –

*During this time, the ovaries are undergoing the first stages of oogenesis.

*The inner lining of the uterus called the endometrium starts to break down

*This causes some bleeding to occur as the endometrium is shed

*This lining and blood is removed from the body via the vagina.

*Menstruation typically lasts about 4 days

*Menstrual Cycle

*Stage 2 – Follicular Phase

*The next step in the menstrual cycle is the endometrium starts to rebuild and thicken

*The egg now begins to grow and develop slightly larger

*The egg could be fertilized at this stage

*This stage usually lasts another 8-9 days

*Menstrual Cycle

*Stage 3 – Ovulation

*The egg is released from the ovary

*At this time, the egg will travel through the fallopian tube heading toward the uterus

*This is the time that the egg is most likely to be fertilized

*This stage only lasts about 2-3 days as the egg will disintegrate after that

*Menstrual Cycle

*Stage 4 – Luteal Stage

*The endometrium has reached its full size

*The spot in the ovary where the egg was released begins to release hormones

*This causes the body to be prepared in case of fertilization

*If there was no fertilization, the body goes through the menstrual phase again and the cycle repeats

*This process lasts about 12-14 days

*Reproduction

*All of these processes lead to the process of sexual reproduction

*Every organism that participates in sexual reproduction on Earth strives to pass on its genes. Some go to extended lengths such as fights to the death, ornamental displays, special calls, pheromones, and much much more.

*It is the process striving to reproduce that can push evolution in a variety of directions.

*Human Reproductio

n

*Reproduction in humans is carried out by the male and female sex organs – the penis and the vagina

*The male inserts the penis into the vagina. This process is called sexual intercourse

*At the end of intercourse, the male ejaculates

*This causes the semen to be released into the vagina

*Human Reproduction

*The semen provides lubrication and nutrients to the sperm as they make a long trek

*Sperm pass:

*Through the vagina

*Past the cervix

*Through the uterus

*Into the fallopian tubes

*Sperm travel at about 50μm/s

*Human Reproduction

*About 300 million sperm make the journey to the fallopian tube where only 1 is allowed to penetrate the egg

*The sperm and egg fuse into one cell called a zygote

*This causes the cell to change the ‘polarization’ of the membrane which pushes other sperm away from the egg.

*The zygote then gets a hard membrane that does not allow any more sperm to penetrate

*Zygote

*The zygote finishes traveling down the fallopian tube and implants in the uterus

*The zygote now begins to grow through

mitosis

*Where the zygote implants, the uterus creates a connection called the placenta

*This is where the mother’s blood will exchange oxygen and nutrients with the embryo

*Embryonic Stage

*The first stage of development in the uterus is the Embryonic stage

*This lasts about 9 weeks

*During this time:

*The cells specialize and differentiate into different types of cells

*The organs begin to develop

*This is the time that the new individual is most vulnerable to deformities

*Fetal Stage

*The fetal stage lasts about 30-31 weeks

*Most of structures of the body have formed already

*The internal structures such as organs and systems finish developing

*At the time of birth, the fetus is ready to survive on its own.

*Birth

*After 9 months in the uterus, the fetus is ready to survive outside the mother’s body

*The cervix with open (dilate) and through muscle action in the uterus, the baby will be pushed out

*The baby typically comes out head first