2.1-2.4

• testes are the site of gamete production in males.
• the male gamete is called sperm.
• sperm is produced in the seminiferous tubules in the testes.
• The onset of puberty is triggered in the pituitary gland by the secretion of a release hormone which is produced by the hypothalamus.
• In males, ICSH is produced by the pituitary gland. It stimulates the interstitial cells to promote testosterone production in the seminiferous tubules.
• Testosterone promotes sperm production, as well as activating the prostate gland and seminal vesicles, in males.
• Levels of testosterone inhibit the hypothalamus and pituitary gland to slow the release of the FSH and ICSH which in turn reduces sperm production temporarily.
• FSH released by the pituitary gland develops the follicles in the ovaries for females and stimulates sperm production directly in the seminiferous tubules in males.
• LH released by the pituitary gland stimulates ovulation in females and brings the development of the corpus leutem.
• The prostate gland and the seminal vesicles secrete fluids that maintain the motility and viability of the sperm.
• The ovaries contain immature ova in various stages of development .
• Each ovum is surrounded by a follicle that protects the developing ovum and secretes hormones.
• Mature ova are released into the oviduct where they may be fertilised by sperm to form a zygote.
• The follicular phase of the menstrual cycle starts with the release of FSH stimulating the development of the follicle and the follicle starting the production of estrogen.
• In the follicular phase of the menstrual cycle, oestrogen stimulates the proliferation of the endometrium and thins the cervical mucus, making it more easily penetrated by sperm.
• In the follicular phase of the menstrual cycle, once oestrogen levels get high enough the stimulates a surge of LH from the pituitary gland.
• In the follicular phase of the menstrual cycle, the surge of LH causes the release of the ova from the follicle (ovulation), causing the end of the follicular phase and the beginning of the luteal phase.
• during ovulation in females, around day 14, body temperature increases 0.5°C.
• In the luteal phase of the menstrual cycle, the surge of LH develops the follicle which causes it to develop into a corpus luteum which secretes progesterone.
• Progesterone in the luteal phase of the menstrual cycle causes further proliferation of the endometrium, preparing for implantation if fertilisation occurs.
• In the luteal phase of the menstrual cycle high progesterone and oestrogen levels cause negative feedback of LH and FSH.
• If fertilisation doesn't occur. Low levels of FSH and LH in the luteal phase of the menstrual cycle, means the corpus luteum is not maintained and starts to degenerate.
• The degeneration of the corpus luteum in the luteal phase of the menstrual cycle causes a drop in progesterone and oestrogen.
• A drop in progesterone and oestrogen in the luteal phase of the menstrual cycle leads to the proliferated endometrium no longer being maintained.
• A drop in progesterone and oestrogen in the luteal phase of the menstrual cycle leads to menstruation - bleeding caused by loss of the endometrium for 4-7 days.
• Low progesterone and oestrogen levels cause the stop of negative feedback of FSH and LH on the pituitary gland, leading to the release of FSH and LH causing the menstrual cycle to repeat itself again.
• If fertilisation does occur, the blastocyst implants itself into the endometrium lining and begins to secrete a hormone, which causes the corpus luteum to continue to release progesterone and oestrogen.
• Women show cyclical fertility leading to a fertile period that lasts only a few days in each cycle.
• Men continually produce sperm in the testes to show continuous fertility.
• Drugs can be used to stimulate ovulation. They mimic the normal action of FSH and LH and prevent the negative feedback effect of oestrogen on FSH during the luteal phase. This can lead to super ovulation, which can lead to multiple births.
• Artificial insemination is the insertion of semen into the female tract by another means of sexual intercourse. Semen can be collected over a period of time and preserved by freezing until required.
• IVF is the surgical removal of eggs from ovaries after hormone stimulation. Eggs are mixed with sperm in a culture dish. The fertilised eggs are incubated until they have formed at least eight cells and are then transferred to the uterus for implantation.
• Intra Cytoplasmic Sperm Injection (ICSI) If mature sperm are defective or very low in number, ICSI can be used. The head of the sperm is drawn into a needle and injected directly into the egg to achieve fertilisation.
• PGS (preimplantion genetic screening) approach that checks the embryo for single gene disorders and common chromosomal abnormalities in general.
• PGD (Preimplantation Genetic Diagnosis) is used to check for a known chromosomal or gene defect.
• Barrier methods of contractions work by either preventing fertilisation, preventing implantation, or by ensuring eggs or sperm are not released.
• Hormonal methods of contraception alter the normal sequence of events in the menstrual cycle to prevent ovulation. Examples of this would be the mini pill (progesterone only) and 'morning after' which can be taken up to 72 or 120 hours after unprotected sex.
• Another example of a hormonal method of contraction is the oral contraceptive pill (chemical method of contraception). It contains a combination of synthetic oestrogen and progesterone that mimics negative feedback preventing the release of FSH and LH from the pituitary gland.
• an IUD is an example of an implantation prevention device and is a form of contraception
• Examples of contraception that prevent fertilisation are condoms and caps.