2.3 the biology of controlling fertility
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What type of fertility do men exhibit?
Continuous fertility Men continually produce sperm in their testes.
what type of fertility do females exhibit?
Cyclical fertility Women are only fertile for a few days during each menstrual cycle.
What physiological changes indicate a woman’s fertile period?
Body temperature rises and cervical mucus becomes thin and watery
What are common causes of infertility in males?
• Low sperm count • Abnormal sperm • Low motility
What are common causes of infertility in females?
• Failure to ovulate • Blocked oviducts • Implantation failure
What is artificial insemination?
A procedure where several samples of semen are collected over time.
When is artificial insemination particularly useful?
When the male has a low sperm count.
What can be done if a partner is sterile in artificial insemination?
A donor may be used to provide semen.
What is the role of drugs in stimulating ovulation?
They prevent the negative feedback effect of estrogen on FSH secretion.
What is the result of stimulating ovulation with certain drugs?
Encouragement of more follicles to develop.
What can other ovulatory drugs mimic?
The action of FSH and LH.
What can super ovulation lead to?
Multiple births or collection of ova for IVF.
What is the first step in IVF programmes?
Surgically removing eggs from ovaries after hormone stimulation.
How are eggs fertilized in IVF?
They are mixed with sperm in a culture dish.
What happens to fertilized eggs in IVF before implantation?
They are incubated until they have formed at least eight cells.
What is pre-implantation genetic diagnosis (PGD)?
A technique used in IVF to identify single gene disorders and chromosomal abnormalities.
What is intra-cytoplasmic sperm injection (ICSI)?
A procedure where the head of the sperm is injected directly into the egg.
When is ICSI used?
If mature sperm are defective or very low in number.
what are physical methods of contraception
• barrier methods (e.g. condoms, diaphragm prevent fertilization) • insta uterine devices (IUDs that prevent implantation of blastocyst) • sterilization (•In females, oviducts are blocked or sealed preventing the ova from reaching the sperm • In males, duct from testicles are cut preventing the release of sperm)
what are chemical methods of contraception
-The oral contraceptive pill (It contains a combination of synthetic ostrogen and progesterone that mimics negative feedback preventing the release of FSH and LH from the pituitary gland This prevents the development of follicles) • The progesterone-only (mini) pill (causes thickening of the cervical mucus) • The morning-after pill (prevents ovulation or implantation)