human reproduction Flashcards
sexual reproduction
requires gametes
genetically varied offspring
meiosis and mitosis
asexual reproduction
doesn’t involve gametes
genetically identical offspring (clones)
mitosis
sperm
flagellum- moves them through water
egg cell
produced monthly from ovaries
external fertilisation
females release ova into water and sperm have to swim through water to fertilise ova
outside body
internal fertilisation
male animals (birds and mammals) ejaculate sperm in special fluid into female bodies
inside body
fertilisation more likely
each gamete has half normal number of chromosomes
fertilisation = full number
humans- sperm + ova only have 23 chromosomes
zygote= 46
fertilisation
fusion of haploid male and female gametes, restoring diploid number of chromosomes in zygote
human fertilisation
during sexual intercourse- pass along sperm duct and mixed with fluid from seminal vesicles (semen)
ejaculated into vagina out of urethra
sperm swims towards oviducts
ovum released into oviduct from ovary every month
from zygote to embryo
zygote travels down oviducts
during time it develops into embryo
(ball of 32 cells which will implant in lining of the uterus)
embryo to foetus
placenta secretes progesterone to ensure uterus lining remains thick, and prevent embryo from aborting
pregnancy- membrane called amnion enclose developing embryo.
amnion secrets amniotic fluid which protects developing embryo against jolts and bumps
embryo develops and gets more complex- when it looks human = foetus
foetus to baby
after 9 months- no room left for foetus to grow so it sends hormonal ‘signal’ to mother to imitate birth (going into labour)
foetus born = baby
placenta (connected by umbilical cord) develops from embryo.
placenta anchors embryo in uterus and allows:
-nutrients and oxygen to move from mother to embryo
-waste materials and carbon dioxide to move from embryo to mother
materials pass from one to another by diffusion
hormones and menstrual cycle
cycle- control development of lining of uterus(womb) so when ovum is fertilised the lining will be ready to receive the fertilised egg
when not fertilised- lining is lost (period)
middle of cycle (day 14) the follicle moves towards edge of ovary and egg is released as follicle bursts open- ovulation
lining of uterus has been repaired after menstruation and thickened- by oestrogen
after egg is released it travels down oviduct (fallopian tube) to uterus.
what is left of follicle in ovary- forms corpus luteum which makes progesterone
placenta secretes progesterone- takes over CL role
puberty in boys
voice breaks sperm production begins shoulders broaden facial, armpit, body and pubic hair growth greater muscle development growth and development of genitalia possible mood swings and acne
puberty in girls
voice deepens- doesn’t break
menstrual cycle begins
pelvis broadens in preparation for pregnancy and labour
armpit and pubic hair growth
muscle development and fat deposits on breasts, hips and thighs
growth and development of genitalia
possible mood swings and acne
