Key Area 3- The Biology of Controlling Fertility Flashcards
What does it mean if women are cyclical fertile?
.They have fertile periods, which means they are only fertile for a few days during each menstrual cycle.
.The pituitary and ovarian hormones cause there to be a small period of fertility of two days which occurs immediately after ovulation.
Why are men continuously fertile?
.The negative feedback control of testosterone maintains a relatively constant level of pituitary hormones FSH and ICSH in the bloodstream so sperm are constantly being produced by the testes
How can drugs stimulate ovulation?
.They prevent the negative feedback of oestrogen on FSH secretion during the luteal phase
.They mimic the normal action of FSH and LH
.However, these drugs are often overly effective they bring about ‘super ovulation’, resulting in multiple births
What is artificial insemination?
.It involves collecting several samples of semen over a period of time to increase the number of sperm in the sample
.Or semen from a donor can be used if the man is sterile
.This is then introduced into the female reproductive tract, during her fertile period, by some other means than sexual intercourse
What is intra-cytoplasmic injection (ICSI)?
.This is used if mature sperm are defective or very low in number
.The head of the sperm is drawn into a needle and injected directly into the egg to achieve fertilisation
What is in vitro fertilisation (IVF)?
.It refers to fertilisation occurring outside the body in a culture dish
.It solves the problem of infertility caused by a blockage of the oviducts
What are the stages of IVF?
.Eggs are surgically removed from the ovaries after hormone stimulation
.The eggs are mixed with sperm in a culture dish of nutrient medium to allow fertilisation to occur or a sperm may be injected directly into an egg (ICSI)
.The fertilised eggs are incubated until they form at least eight cells
.These are then inserted into the mothers uterus (uterine implantation)
.The remaining embryos can be frozen and stored in case a second attempt at implantation is required
What is pre-implantation genetic diagnosis?
.It identifies single gene disorders and chromosome abnormalities when used in conjunction with IVF
Which two methods can be used in conjunction with IVF?
.In vitro fertilisation, ICSI
.Pre-implantation genetic diagnosis, PGD
What are some physical methods of contraception?
.Barriers
.Condom
.Diaphragm
.Cervical cap
.IUD
.Sterilisation procedures
What is the Intra-uterine (IUD) or coil?
.It is often T shaped with metallic copper parts
.It is fitted into the uterus to prevent the implantation of an embryo in the endometrium
What are the sterilisation procedures?
.In men, a vasectomy involves cutting and tying the two sperm ducts. This prevents sperm being released during sexual activity
.In women, a tubal ligation involves cutting and tying the two oviducts. This prevents eggs meeting sperm and reaching the uterus
What is the oral contraceptive pill?
.It is a chemical method of contraception.
.It contains a combination of synthetic oestrogen and progesterone that mimic negative feedback control preventing the release of FSH and Lh by the pituitary gland
.This procedure makes the concentration of progesterone and oestrogen increase in the bloodstream, resulting in the inhibition of follicle maturation and ultimately ovulation fails to occur
What is the progesterone only mini pill/injection/implant?
.It contains synthetic progesterone to thicken the cervical mucus to reduce sperm access to the uterus
What is the morning after pill?
.It is emergency hormonal contraceptive pills to prevent or delay ovulation
.These pills are often referred to as ‘morning after’ pills, but they can be taken up to 72 hours or 120 hours after unprotected sex, depending on which type of pill is used
