Revision:Reproduction

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Describe how Sexual reproduction promotes variety in a species

• Half the genes of one individual are donated to the offspring, and half the genes of the other individual are donated to the offspring. This promotes variability.

Draw diagrams of the male and female urogenital systems

Explain the role of hormones in regulating the changes of puberty in boys and girls, and in the menstrual cycle

Role in changes of puberty

• Testosterone
  • Responsible for the enlargement of
    • the penis and testes
    • the prostate
    • other accessory organs.
  • Affects the growth of the larynx
    • accompanying a deeper voice
  • an increase in skeletal size
  • a distribution of body hair
  • they also stimulate muscle tissue
• Oestrogen
  • Role in Menstrual cycle
• FSH
  • Stimulates ovaries to produce Progesterone
  • stimulates the growth of a follicle in the ovary
• LH
  • Causes ovulation
  • Stimulates ovaries to produce Progesterone
• Oestrogen
  • Repair of uterus lining
  • Release of LH
• Progesterone
  • Uterus lining maintained
  • Inhibits FSH production

List the Secondary Sexual Characteristics of both sexes

• Male
  • Growth of Larynx
    • Deeper Voice
  • Increase in skeletal size
  • Body hair
• Female
  • Changes in distribution of body fat
  • Growth of body hair
  • Hips widen
  • Breasts grow
• Both
  • Growth spurt

Explain the difference between Copulation and Fertilisation

• Fertilisation- the fusion of an egg cell and a sperm.
• Copulation is sexual intercourse.

Describe Early embryo development up to implantation of blastocyst

• Fertilisation must occur in an oviduct because if the cell has travelled any further it will be dead. The egg cell has a protective layer around it called the vitelline envelope. A sperm uses the enzymes in its acrosome to get into the cell and through the protective layer. Once a sperm cell has entered the egg cell, the egg cell changes its structure so that no single sperm can enter it. The nuclei of the two cells fuse. fertilisation results in

1. changes in the outer surface of the egg that prevent entry of other sperm cells
2. metabolic activation of the egg
3. introduction of the genetic material of the father
4. cleavage.

Embryo Development- At about 36 hours after fertilization, the fertilized egg divides to form two cells, at 60 hours, the two cells divide to form four cells. At three days, the four cells divide to form eight. This ball of cells is called a blastocyst. By about 5 days after fert. it consists of some 120 cells. 6 days after fert. the ball reaches the uterus and penetrates the endometrial tissues-called implantation. It becomes surrounded by ruptured blood vessels and the nutrient-filled blood escaping from them.

State that the Fetus is supported and protected by amniotic sac and amniotic fluid

State that Materials are exchanged between maternal and fetal blood in placenta

Outline the Process of birth and hormonal control

• labour, delivery and afterbirth.
• Labour
  • Dilation begins with the onset of contractions of the uterus. It ends with the full dilation, or opening, of the cervix. At the beginning, uterine contractions occur at intervals of about 15 to 20 minutes and are relatively mild.
  • Expulsion bigins with the full dilation of the cervix and the appearance of the head in the cervix called crowning.
  • placental stage begins immediately after the baby is born. It involves contractions of the uterus and the expelling of fluid, blood and finally the placenta with the umbilical cord attached, also called the afterbirth.

Describe Four methods of family planning and contraception

• Vasectomy - the vas deferens on each side is severed, and the cut ends are folded back and tied off, preventing the release of sperm from the testis. This is 100% effective.

• Tubal ligation - the oviduct is severed and tied. This prevents the passage of oocyte to uterus. Also 100% effective.

• The pill - inhibits secretion of FSH and LH thereby preventing follicle maturation and ovulation. 100-90 % effective. Contains progesterones and estrogens.

• Condom - covers the male penis and prevents sperm from entering the vagina. 97-64% effective, depending on the quality.

Outline the Ethical Issues of Family Planning and contraception

There are no ethical issues. (Surely this is wrong - while so people might see no ethical issues, there are some such as preventing the natural course of things/preventling life from forming that some people might have. Otherwise there would not have been all the controversy in history over contraception and the Catholic Church would not have had well known anti-contraception views). To say there are no ethical issues is plain wrong. One person might not have any issues, but to try and say there are none full stop is showing a lack of understanding of others and their beliefs.)

Outline the techniques of Amniocentesis and chorionic villus sampling

• Amniocentesis
  • fluid samples are taken from the amniotic cavity. They contain cells that have been sloughed off by the embryo. It cannot be performed until the sixteenth week of pregnancy. It can be used to diagnose nearly 400 conditions from chromosomal abnormalities to biochemical disorders

• CVS
  • a small sample of tissue is removed from the chorion, which is identical to the embryo itself. It is taken via the vagina.

Outline the process of In vitro fertilization (IVF)

The process of uniting two human germ cells (sperm and egg) outside the human body and in an artificial environment; term often includes the process of embryo transfer; first successful human birth using this technique took place in England 1978; the process itself and related techniques such as the freezing of eggs, sperm, or embryos for future implantation have raised ethical questions, including the fear of experimentation with human foetuses.

Removal of the egg - the egg is taken from the Graffian follicle in the ovary. The aim is to collect the egg a few hours before ovulation. To increase the chances of success, doctors arrange for the woman to produce a larger number of eggs than the single one normally formed during each menstrual cycle. She is made to produce many eggs through the use of hormone-based drugs. Using ultrasound guidance, a hollow needle is inserted into the vagina, and through its wall into one of the follicles. The egg is then sucked out, and placed in a test-tube containing a special medium. This procedure is repeated for the other follicles. The eggs are then maintained in separate test tubes at 37 C in an incubator. Meanwhile, the sperm are prepared. A few hours after collection, about 100, 000 of the prepared sperm are added to each egg in a small petri dish. After.16- 20 hours the eggs are checked to see if they have been fertilized. The embryos are then left to develop for 2-3 days in the incubator. They can then be transplanted back into the uterus.

Outline Ethical Issues of IVF

Again, there are no ethical issues related with IVF (Again, a stupid thing to say - of coruse there are. You might not have any, but it doesn't mean others don't and you can't talk about them here.)

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