�HOW IS A HUMAN-BEING FORMED?

¿HOW IS A HUMAN-BEING FORMED? Description of male and female genital organs. Ovum and sperm. Fertilisation. Zygote. Cellular division. The human embrion and its development. Birth. Summary. INTRODUCTION - What is reproduction? - Reproduction of a human being - Male and female reproduction cells : spermatozoon and ovum - Where are spermatozoa produced? - Where are ova produced? FERTILIZATION - The human race has a system of internal fertilisation. What does this mean? - Journey of the spermatozoa - Fertilisation of the ovum EMBRYO DEVELOPMENT - The 4 week-old embryo - Formation of legs and arms - Heart beating, primitive blood-circulation network. Liver and genital crests. - The placenta - At the 5th week: pancreas and muscles - At the 7th week: retina, hands and fingers - At the 8th week: gastric juices, bones of the hands and feet, mouth and nose - At the 10th week: From this age on the embryo is called foetus and its heartbeat can be heard by ultrasonic waves. - At the 11th week: Its vagina or penis is formed - At the 12th week: The foetus weighs about 2/3rds of an ounce - Third Month : neurons start making up its future nervous system - The foetus and the umbilical cord - The amniotic fluid - The placenta allows antibodies to pass through it, also nicotine, alcohol and viruses which can seriously affect the foetus growth - During this 3rd month, eyelashes and nails appear. The foetus now has fingerprints. - At the 17th week: we can clearly make out the spinal column. The mother will be able to feel the movements of the child. - At the 23rd week: Practically all of its organs are now formed and all it has to do now is to grow. - From now on, and up until the time it is born, the baby will gain size and weight rapidly. - The foetus will change its position to one where its head will be upright. - The foetus is fed through the umbilical cord - Meanwhile, the foetus has returned to its head-downwards position - Through the amniotic membrane we can distinguish the features of the soon-to-be-born child - Nine months after it was conceived, the baby will normally go about preparing itself for birth by positioning its head in the mother’s pelvis. When this happens, then birth is about to take place. BIRTH - The foetus passes through the neck of the uterus which has been previously dilated by a series of contractions and finally emerges. - Then the umbilical cord is cut. - Now the child has to breathe for itself. - Problems during the birth: the “Breach birth” SUMMARY