reproduction in humans Flashcards
sexual and asexual reproduction compared
both include mitosis, difference is that asexual does not involve specialised gametes or fertilisation
stages of sexual reproduction
gametes produced (through meiosis), male gamete transferred to female gamete, fertilisation, zygote formed (which divides several times by mitosis to form all the new cells of the animal)
production of gametes
male and female gametes produced in the sexual organs (testes and ovaries). cells in the organs divide by meiosis to produce the gametes.
sperm cells
sac of enzymes to penetrate the membrane of the egg, nucleus, mitochondria to provide energy for movement, flagellum for propulsion
mitosis vs meiosis
mitosis produces diploid cells which are genetically identical, meiosis produces haploid cells which are genetically unique
main stages of fertilisation
sperm approach the egg, a sperm penetrates the cell membrane and the sperm’s nucleus enters, the fertilisation membrane prevents any more sperm from entering. the sperm and egg nuclei fuse to form a zygote.
semen
sperm cells travel along the sperm ducts where they are mixed with a fluid from the seminal vesicles. semen is ejaculated through the urethra into the vagina
ovulation
each month an egg is released from the ovaries into the oviduct (fallopian tube)
umbilical chord
consists of umbilical artery (carrying deoxygenated blood containing waste products from the fetus to the placenta) and umbilical vein (carrying oxygenated blood containing nutrients from the placenta to the fetus)
placenta
allows fetus to obtain oxygen and nutrients from mother’s blood and to get rid of waste products e.g urea and CO2. placenta secretes female hormones, in particular progesterone which maintains the pregnancy and prevents the embryo from aborting.
amniotic sac
keeps the amniotic fluid around the developing fetus
amniotic fluid
cushions the fetus from mechanical shock and maintains a constant temperature around the fetus
pregnancy
membrane called the amniotic sac encloses the developing embryo, secretes a fluid called amniotic fluid. when the fetus becomes recognizably human we call it a fetus. At the end of 9 months of development there is no room for the fetus to grow which sends a hormonal signal to the mother to begin the birth process
stages to the birth of a child
- dilation of the cervix. gets wider to allow the baby to pass through. The muscles of the uterus contract strongly which tears the amniotic sac allowing the amniotic fluid to escape (water breaking)
- delivery of the baby. strong contractions of the muscles of the uterus push the baby’s head through the cervix and then through the vagina to the outside world.
- delivery of the afterbirth. after the baby has been born the uterus continues to contract and pushes the placenta out.
FSH
follicle stimulating hormone, stimulates the growth of the follicle in the ovaries in girls and stimulates sperm production in boys