y4.1 human reproductive system 👩❤️💋👨 Flashcards
define asexual reproduction
asexual reproduction is the process resulting in the production of genetically identical offspring from one parent
define sexual reproduction
sexual reproduction is the process involving the fusion of nuclei to form a zygote and the production of genetically dissimilar offspring
changes in the ovary during menstruation
primary follicle -> Graafian follicle -> ovulation (Graafian follicle ruptures and releases ovum into oviduct) -> corpus luteum -> corpus luteum disintegrates
stages in the menstrual cycle: day 1 to 5 (FSH)
menstruation!
- due to low levels of oestrogen and progesterone, uterine lining breaks down and sheds in the form of menstrual blood
- pituitary gland secrets follicle-stimulating hormone (FSH)
stages in the menstrual cycle: day 6 to 13 (oestrogen and LH)
follicular stage!
- FSH stimulates the development of follicles in the ovaries; one of them develops into a Graafian follicle
- FSH stimulates the follicles to secrete oestrogen
- oestrogen stimulates the repair and growth of the uterine lining (becomes thick and spongy with blood vessels)
- high levels of oestrogen inhibit FSH production and stimulate pituitary gland to secrete LH
stages in the menstrual cycle: day 14 (LH)
ovulation!
- LH stimulates the Graafian follicle to rupture and release the ovum into the oviduct
- LH stimulates the formation of corpus luteum
stages in the menstrual cycle: day 15 to 28 (progesterone)
corpus luteum stage!
- corpus luteum secretes progesterone and some oestrogen
- progesterone maintains uterine lining by causing it to thicken further and be supplied with blood capillaries, preparing it for implantation of embryo
- progesterone inhibits ovulation and the production of FSH and LH
if the ovum is not fertilised at the end of the stage, the corpus luteum breaks down. progesterone and oestrogen levels drop and another cycle begins
describe the process of fertilisation
1) the ovum released from the ovary is usually surrounded by layers of follicle cells
2) to penetrate the ovum, the acrosome of the sperms releases enzymes to disperse the follicle cells and break down part of the ovum membrane for sperm to enter
3) the haploid sperm nucleus fuses with the haploid ovum nucleus to form a diploid zygote
4) once a sperm has entered the ovum, the membrane of the ovum changes so that no other sperms can enter
describe the process of implantation
1) cilia lining the oviduct sweep the zygote along the oviduct to the uterus
2) the zygote divides repeatedly by mitosis to form a ball of cells called embryo
3) the embryo secretes a hormone which prevents the corpus luteum from breaking down until the placenta is formed ; corpus luteum continues to secrete oestrogen and progesterone until placenta can take over
4) embryo embeds itself in the uterine lining ; fertilisation!
describe the development of placenta
1) after implantation, finger-like projections called villi grow from the embryo into the uterine lining, making up the placenta
2) umbilical cord containing 2 umbilical arteries and 1 umbilical vein connects the embryo to the placenta
functions of the amniotic fluid
- absorb shock, protect fetus against mechanical injury
- supports and cushions the fetus, allowing fetus to move
- lubricates the birth canal during birth
functions of placenta
- nutrition, gaseous exchange and excretion
- oxygen and nutrients for carbon dioxide and urea
- protective antibodies diffuse to protect against diseases
- produces progesterone for uterine lining
why does the mother and the fetus’ blood have to be kept separate?
to prevent the high blood pressure of the mother’s blood from damaging fetus’ blood vessels, and prevent agglutination if mother and child do not have compatible blood types
