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The reproductive system
- 40. MULTIPLE BIRTHS
Editor's Notes
- ..for the perpetuation of life
- Types: budding, multiple fission, binary fission, Regeneration/Fragmentation
- Main reproductive organs – GONADS that produce sex cells called GAMETES
- On average, 1.25 to 5 mL of semen is expelled during ejaculation
- Puberty in females starts when the hypothalamus signals the pituitary gland to release FSH and LH. FSH stimulates cells within the ovaries to produce estrogen
- During the menstrual cycle, an egg develops and is released from the ovary. The uterus is prepared to receive a fertilized egg. If the egg is fertilized, it is implanted in the uterus and embryonic devt begins. If the egg is not fertilized, it is discharged.
- The follicular phase begins when estrogen levels in the blood are low Anterior pit.gland secretes FSH and LH which cause a follicle to develop to maturity As the follicle develops, cells surrounding the egg enlarges and produce more estrogen Estrogen causes the lining of the uterus to thicken
- During sexual intercourse, sperm is released when semen is ejaculated through the penis into the vagina. Sperm swim through the uterus into fallopian tubes. If an egg is present in one of the fallopian tubes, its chances of being fertilized is high. The egg is surrounded by a protective layer that contains binding sites to which sperm can attach. Sperm head releases enzyme that break down protective layer of egg
- Full term at 39 to 40 weeks
- Homopaternal superfecundation Heteropaternal superfecundation Fraternal twinning Identical twinning