4.5 : Fertilization & Pregnancy Fertilization

•  During sexual intercourse, sperms ejaculated into the vagina pass through the cervix into the uterus

•  The sperms then swim up to the Fallopian tubes

•  If an ovum is present in the Fallopian tube, the sperms surround the egg cell

4.5 : Fertilization & Pregnancy Fertilization •  Only the head of

the sperm can break through the membrane of the ovum

•  The tail is left outside

•  Nucleus of sperm fuses with nucleus of ovum and forms a zygote

•  Fertilization takes place in the Fallopian tube – Pregnancy begins

4.5 : Fertilization & Pregnancy Fertilization

•  Cell division happens as the zygote moves down the Fallopian tube towards the uterus

•  Zygote divides into two cells, then four and so on until it becomes a small ball of many cells called EMBRYO

4.5 : Fertilization & Pregnancy Implantation of the Embryo

•  IMPLANTATION -Embryo attaches itself to the uterus wall with a placenta

•  Placenta is connected to the embryo by the umbilical cord

•  Embryo is surrounded & protected by 2 membranes containing fluid called amniotic fluid with the function : –  Shock absorber & protects

the embryo –  Buoys up the embryo so

that it can move freely

4.5 : Fertilization & Pregnancy Development of the Embryo into a Foetus

•  Embryo has its own blood circulatory system – does not depend on the mother for blood supply

•  Things that diffuse from mother’s blood capillaries into placenta : –  Dissolved food –  Hormones –  Antibodies –  Oxygen

4.5 : Fertilization & Pregnancy Development of the Embryo into a Foetus

•  In the same way, waste products from embryo will diffuse into placenta then into mother’s blood capillaries

•  Embryo continues grow in the uterus

•  After 2 months : All main organs can be clearly seen – it’s called FOETUS

4.5 : Fertilization & Pregnancy Development of the Embryo into a Foetus

•  About 4 ½ months, mother starts to feel the kick from foetus

•  Before birth, foetus changes its position so that the head lies downwards

•  About 9 months : Foetus is born which is then called a baby

•  Gestation : The period from fertilization to birth

4.5 : Fertilization & Pregnancy Development of the Embryo into a Foetus

•  During birth : –  Uterus wall

contracts –  Membranes

surrounding foetus break

–  Cervix opens –  Pushing force of

the mother together with the force of contraction of the uterus wall push the baby out through the vagina

4.5 : Fertilization & Pregnancy Development of the Embryo into a Foetus

•  After birth, umbilical cord is tied in two places to prevent bleeding and then cut in between

•  Placenta, umbilical cord & ruptured membranes associated with foetus are discharged automatically : aka AFTERBIRTH