Crash Course in Reproduction • http://www.youtube.com/watch?v=_7rsH2loIY8
Defining Sexual Reproduction • 1. A sex organ produces sex cells • 2. A sperm combines with a egg • 3. A zygote is produced and develops into an embryo • 4. The embryo develops through mitosis and cell division into a mature offspring
Conjugation • Some bacteria don’thave a nucleus. • Conjugation is when two bacteria join together at their membrane. • they can share small pieces of DNA
Separate Sexes Sex cells are made by plants and animals • Gametes are sperm and egg cells. • Gametes have half as many chromosomes as a body cell. • Fertilization is when gametes meet to start forming a new organism
Internal vs. External Fertilization • Internal Fertilization is when gametes meet inside of a female • (ex. Primates, Elephants)
Internal vs. External Fertilization • External Fertilization is when two gametes meet outside of an adult • (ex. Fish such as salmon)
Hermaphrodites • individuals who create both male and female sex cells within the same body.
Hermaphrodites • Slow or motionless organisms succeed as hermaphrodites (they can be less picky about mates that way). • Flat worms can exchange sperm and eggs with one another.
Testes • Produces the sperm • Contained inside the scrotum • Hangs outside of the body to decrease the temperature (approx 3 degrees) • Optimum sperm production at lower temperatures
Prostate Gland • The source of seminal fluid
Sperm: the swimmers • One cell • Head – Contains DNA that enters into the egg at fertilization • Mitochondria – Gives energy to allow the flagellum to move • Flagellum/tail – Propulsion • Live for up to 5 days inside of the female
Epididymus: storage • Stores the mature sperm • If sperm not used, white blood cells scavenge and devour old sperm
Vasectomy • Two small incisions are made on either side of the scrotum through which the vas deferens can be cut and tied/sealed to ensure it does not reattach
Ejaculation • The release of semen from an erect penis • Sperm is forced through the vas deferens by involuntary contractions • Passes by the prostate and seminal vesicles • Prostate and Seminal Vesicles: provide fluid that activate the sperm (sugars that give the sperm nourishment)
Ejaculation • The semen and sperm are ejected out of the penis through the urethra • 300 000 000 sperm cells are released
Egg Preparation: the other side • All eggs begin in the ovary • Eggs begin as a follicle (it is the eggs plus several other cells that give the egg nourishment) • The human ovary contains 400 000 immature follicles • Once mature the ovary releases the egg into the oviduct (fallopian tubes) to wait for the sperm
The Ovary: Ovulation http://www.youtube.com/watch?v=nLmg4wSHdxQ
Swimming in unsafe waters • Post-ejaculation • The sperm are inserted into the vagina and swim into the uterus • The vagina is a harsh place, 25% of sperm die upon ejaculation
The long journey • Sperm then have to choose between fallopian tubes • ½ go the wrong way…
Fertilization • The remaining sperm, then need to dig through the layers of the egg to fertilize it • Only one sperm gets through, then the egg’s membrane becomes impermeable
Fertilization • Once the sperm has joined with the egg, the zygote moves down the fallopian tube into the uterus and attaches to the endometrium
Fertilization Video • http://www.youtube.com/watch?v=_5OvgQW6FG4 • http://www.youtube.com/watch?v=1w9o89KkX2A - min.15-20
Menstruation • When a woman menstruates, she sheds the lining of her uterus (endometrium) because she is not pregnant. This shedding of the endometrium is the bleeding that women experience roughly every 28 days.
Menstrual Cycle – Why do women menstruate? • Average menstrual cycle is 28 days • Menstruation (or the bleeding) lasts about 3-7 days.
Menstrual Cycle – Why do women menstruate? • Each month, the uterus prepares for a fertilized egg to embed in its lining • The lining has a rich blood supply to potentially support a embryo • If a fertilized egg does not implant (ie: the woman does not get pregnant), the lining is shed (menstruation) and a new cycle begins • This whole cycle is regulated by several hormones
Birth Control Pills • The pill has many formulations, but most contain synthetic estrogens and progestins, and some contain only progestin. • keep the levels of circulating estrogens and progestinsHIGH • avoid that big drop at day 11 • big drop prevents LH and FSH from increasing, which prevents ovulation
Birth Control Pills • So why do you still menstruate on the ‘pill’? • the last week you are only taking placebo pills…and so estrogen and progestrone levels drop off, causing menstruation.