Human reproduction by David


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Human reproduction by David

  1. 1. PRIMARY SEXUAL CHARACTERISTICSThe reproductive systems are the primary sexual characteristics. We alreadyhave them when we are born and they are different for male and female.
  2. 2. The external characteristics which differentiate men from women are called secondary sexual characteristics. Other changes are specific to each sex: Girls develop breasts and their hips get wider. Boys get deeper voices.
  3. 3. Reproductive cells carry out the function of reproduction. Sperm are the male reproduction cells. They are small. They have a head and a long tail called a flagellum. They are produced in large numbers from the time of puberty. Ova are the female reproductive cells. They do not move. From puberty, an ovum matures every month.
  4. 4. The female reproductive system is made up of: The ovaries produce the ova. The uterus is where the baby develops. The Fallopian tubes connect the ovaries to the uterus. The vagina connects the uterus to the outside of the body. The vulva is the external part of the female reproductive system.
  5. 5. The male reproductive system is made up of these organs:The testicles are outside the body. They produce sperm. They arecovered by a bag of skin called the scrotum.The vas deferens take sperm from the testicles to the urethra.The urethra takes the sperm outside the body.The seminal vesicles and prostate produce seminal fluid and send it tothe urethra.The penis is outside the male reproductive system.
  6. 6. Fertilisation occurs when an ovum and sperm join inside theFallopian tubes and they create a single cell called zygote.The zygotegoes down the Fallopian tubes, it is implanted in the wall of the uterusand it becomes an embryo.
  7. 7. Pregnancy lasts about 9 months an ends in a birth. During the early stages, different structures are created to protect the embryo. The placenta takes nutrients and oxygen from the mother’s blood to the embryo. The umbilical cord connects the embryo to the placenta. The amniotic sac protects the embryo. The baby develops step by step. After 3 months: The embryo has all its organs. It becomes a foetus. After 5 months: The baby’s body develops and it starts moving and the mother feels it. After 9 months: The baby is readyto be born and it weighs 3 kilos.
  8. 8. The process of giving birth is called labour. Labour takes place in three phases: Dilation: Rhythmic contractions make the opening of the vagina and vulva is big enough for the baby to come out. Expulsion: The baby is born and the doctor cuts the umbilical cord. Afterbirth: The placenta comes out of the mother’s body.