Sex in Science

  • Created by: Michaela
  • Created on: 26-04-14 09:51


  • The reproductive organs produce sex cells. They form an organ system called the reproductive systrem
  • Girls are born with about 100,000 undeveloped egg cells in each ovary
  • In females, the ovaries contain small, undeveloped egg cells.
  • Once every 28-32 days, an egg cell from one ovary becomes mature.
  • It is released into the oviduct (some called the Fallopain tube or egg tube.)
  • The oviduct is lined with cilia that sweep the egg cell towards the uterus. 
  • The uterus is where the baby will develop.
  • It has strong, muscular walls and a soft lining.
  • The lower end of the uterus is made of a ring of muscle called the cervix.
  • The cervix holds the baby in place during pregnancy
  • The cervix opens into the vagina.
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  • Males make sperm cells in thier testes.
  • The testes are held outside the bodyin the a bag of skin called the scotrum.
  • Their position helps to keep the sperm cells at the right temperature to develop properly.
  • Adult men produce up to 100 million sperm cells every day.
  • A sperm cell is 0.06mm long.
  • When sperm cells are released from the testes they travel up the sperm ducts, where special fluids are added from glands.
  • The fluids give the sperm cells energy.
  • Together the sperm cells and the fluids are called semen.
  • the semen leaves through the urethra.
  • This tube also carries irine from the bladder, but never at the same time as semen.
  • The penis head is sensitive and is protected by a covering of skin (the foreskin).
  • This is sometimes removed, for religious reasons or because it is too tight, in a process called circumcision.
  • After puberty, amn will produce sperm for the rest of his life.
  • A womens ovaries stop releasing egg cells at about the age of 45-55-known as the menopause
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  • Sometimes, a women might release 2 egges at the same time.
  • If both are fertilised, twins are produced.These twins will not be identical.
  • Sometimes the fertilised egg cell divides in 2 and 2 new cells get seperrated.
  • Both of these cells can grow into embryos and produce identical twins.
  • Identical twins will either be 2 girls or 2 boys.
  • Most animals have more than 1 baby at a time. 
  • Having more than one baby is called a multiple birth
  • Female nine-banded armadillos always give birth to four identical quadruplets
  • Very occasionally, when the fertilised egg divides in 2, the 2 new cells start to seperate but do not seperate fully.In this case the twins will ne joined together (conjoined), often at the hip. During world war ll the cruel Nazi 'doctor' Josef Mengele sewed twins together to try to create conjoined twins
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  • As a man and a woman prepare to have sex, various things happen to their bodies.
  • The womans vagina becomes moist and the mans penis fills with blood, makingit stiff (an erection).
  • During sex, the penis is inserted into the vagina andthe man moves it back wards and forwards.
  • Eventually seman is pumped out into the top of the vagina.
  • This is called ***********
  • The seman is sucked up through the cervix .
  • Small movements of the uterus wall carry it up to the oviduct .
  • Here, the sperm cells start to swim along the oviducts.
  • If a sperm cell meets an egg cell, the sperm cell can burrow into it and fertilise it.
  • In fertilisation, the nucleus of the sperm cell joins with the nucleus of the egg cell.
  • Each nucleus contains half the instructions for a new human and so the baby will have features from both its mother and its father.
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Fertility Treatmeant

  • Some family cant start familys this is because problems with the man or th womans reproductive organs.
  • Hospital tests can find out whats wrong.
  • Damaged or narrow oviducts may stop sperm cells getting to the eeg cell.
  • Doctors can try to make the wider.
  • If this does not work, the women may be given a sex hormone to make her produce many egg cells all at once.
  • These are collected and added to mans sperm cells in a dish.
  • The fertilised egg cells are then implanted in the uterus
  • Some men produce very few sperm cells (they have a low sperm count).
  • In this case, one sperm cell is taken and injected into an egg cell using a very fine needle.
  • Helping couples to have a baby in this way is called IVF(in vitro fertilisation)and  the babies are often called test-tube babies.
  • The first successful IVFtreatmeant was carried out in rabbits in 1959
  • Scientists then did further experiments with mice before they were ready to try IVF out on Humans.
  • The worlds first test-tube baby, Louise Brown, was born in Oldham in 1978
  • Ivf is also used in animals today, to increase the numbers of animals that dont breed well in captivity
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  • Menstrual cycle is a sersies of events that occur in the female reproductive system.
  • Each takrs about a month and is controlled by sex hormones
  • These are made in the brain and ovaries.
  • The soft lining of the uterus breakes passes out of the agina along with a little blood. A period usually lasts gor 3-7 days.
  • After menstruation: an egg cell starts to mature in one of the ovaries.
  • About 14 days after the cycle has started, the egg cell is released.This is ovulation.
  • egg cell is swept along the oviduct toward the uterus.
  • Soft lining of the uter us helps to feed an embryo and the lining is replaced each cycle to make sure it can do this.
  • About 14 days after ovulation, if the egg has not been fertilised, the lining of the uter us breaks apart again and the cycle restarts with another period.
  • If the women becomes pregnant the cycle stops.
  • A period will occur every 28-32 days.
  • A period can vary a lot , especially when periods first start.
  • Sanitary towels or tampons are used to absorb the blood.
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Being Pregnant

  • Amniotic fluid, protects the baby
  • The fluid is contained within a bag called the amnion
  • A plaenta also grows
  • It provides the developing foetus wih the things it need to grow like e.g(oxygen,water and food) from the mothers blood into the foetus blood.
  • The umbilical cord carries blood between the foetus and the placenta.
  • mothers blood does not mix with the foetus blood.
  • mothers blood is pumped around her body under a lot of pressure which would damage the delicate foetus.
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A healthy foetus

  • Pregnant women eats a healthy diet since she must provide the foetu with food, including vitamins and minerals.
  • Needs to take regular exercise to keep her muscles strong and her circulatory system working well.
  • Ante-natal classes teach women specail exercises to prepare them for birth
  • pregnant women go for ultrasound scans.These make pictures of the foetus that doctors use to see if there are ang problems.
  • Some viruses, alcohol, drugs and chemicals from cigarette smoke will all go through the placenta and into the foetus, where they can cause damage.
  • viruses are tiny microbes that can cause diseases. 
  • Virus that cause rubella can cause a foetus to become deformed 
  • Girls should be vaccinated against rubella.
  • alcohol will damage a foetus brain.
  • lllegal drugs, like heroin, also cause brain damage in the foetus.
  • Doctor , be very careful about what medicines they give to pregnant women.
  • The blood of a women who smokes carries less oxygen than it should, which means that the foetus may not get enough oxygen. A baby that has not recieved enough oxygen is likely to be premature.
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