Bio test 1, Reproduction

• Sexual arousal in the male


  Penis becomes firm and erects as a result of blood flowing into the erectile tissue
• Sexual arousal in the female


  Lining of the vagina produces mucus to lubricate the vagina
• Copulation


  Male inserts the penis into the female’s vagina
• Ejaculation


  Sensory stimulus in the male results in the ejaculation of semen into the top of the vagina
• Fertilization


  1. Sperm swims through the cervix and into the uterus

  2. Sperm enters the cytoplasm of the egg and the male nucleus of the sperm fuses with the female nucleus
• The released egg is thought to survive for about 24 hours
• The sperm might be able to fertilize an ovum for about 2 or 3 days
• There is only a short period of about 4 days each month when fertilization might occur
• If the fertile period can be estimated accurately, it can be used either to achieve or to avoid fertilization (conception)
• Many mammals give birth to more than one offspring at a time, each member of which has come from a separate egg
• Human twins may come from one zygote (identical, or monozygotic twins) or two zygotes (non-identical, dizygotic, or fraternal twins)
• Fraternal twins do not resemble each other any more than other children born separately in the same family, but identical twins are strikingly alike and always of the same sex
• Triplets, quadruplets, and quintuplets may include a pair of identical twins. The other babies in such multiple births usually come from separate zygotes
• About 33% of identical twins have separate placentas, but the other identical twins share a common placenta
• Embryo development


  The fertilized egg (zygote) first divides into two cells. Each of these divides again, producing four cells. The cells continue to divide to produce a solid ball of cells, an early stage in the development of the embryo. The embryo travels down the oviduct to the uterus, where it implants into the lining. The embryo grows, producing new cells that form tissues and organs. After 8 weeks, when all the organs are formed, the embryo is called a fetus
• One of the first organs to form in the embryo is the heart, which pumps blood around the body
• Inside the uterus, the embryo becomes enclosed in a fluid-filled sac called the amnion or water sac, which protects it from damage and prevents unequal pressures from acting on it. The fluid is called amniotic fluid
• The placenta becomes closely attached to the lining of the uterus and is attached to the embryo by a tube called the umbilical cord
• Oxygen and nutrients such as glucose and amino acids pass across the placenta to the embryo’s bloodstream. Carbon dioxide passes from the embryo’s blood to that of the mother. Blood entering the placenta from the mother does not mix with the embryo’s blood
• Human embryo from 5 to 35 weeks is surrounded by the amnion and placenta
• As little as 4 weeks after giving birth, it is possible, though unlikely, that a woman may conceive again
• Frequent breastfeeding may reduce the chances of conception
• It would be possible to have children at about 1-year intervals
• Most people do not want, or cannot afford, to have as many children as this
• All human communities, therefore, practice some form of birth control to space out births and limit the size of the family
• Family planning methods


  Methods used to space out births and limit the size of the family
• Family planning methods

  • Natural
  • Artificial
• Some family planning methods

  • Can help prevent the transmission of HIV and other sexually transmitted infections
• Family planning /contraception


  Reduces the need for abortion, especially unsafe abortion
• Family planning


  • Reinforces people’s rights to determine the number and spacing of their children
• Preventing unintended pregnancy


  Prevents deaths of mothers and children
• Benefits of family planning / contraception

  • Preventing pregnancy-related health risks in women
  • Reducing infant mortality
  • Empowering people and enhancing education
  • Reducing adolescent pregnancies
  • Slowing population growth
• Abstinence


  This involves a couple avoiding sexual intercourse to prevent pregnancy and exposure to sexually transmissible pathogens
• Abstinence


  • Effective method for preventing pregnancy and exposure to sexually transmissible pathogens
• Fertility Awareness/Natural Family Planning


  Rely on understanding the most likely time of ovulation to avoid intercourse or use a barrier method
• Withdrawal (Coitus Interruptus)


  Refers to the moment a man pulls his penis out of his partner’s vagina before ejaculation to prevent sperm from entering and fertilizing an ovum
• Withdrawal (Coitus Interruptus)


  • Requires no money, devices, hormones, or medical provider; effectiveness similar to male condom; no protection against sexually transmitted infections and HIV; requires self-control; may diminish pleasure for some
• Monitoring body temperature


  If it were possible to know exactly when ovulation occurred, intercourse could be avoided for 3–4 days before and 1 day after ovulation
• Cervical mucus


  Changes in cervical mucus can help detect the fertile period for avoiding intercourse
• Fertility awareness methods


  • Standard Days Methods
  • Calendar Rhythm Method
  • Symptothermal Method
  • Ovulation Method