2.2

• Corpus luteum


  The remains of the follicle in a mammalian ovary after it has released an ovum (egg) into the oviduct. The corpus luteum secretes hormones involved in the menstrual cycle.
• Fertilisation


  The fusing of the nucleus of the male gamete and female gamete.
• Follicle


  Fluid filled ball of cells found in the ovary containing an ovum (egg).
• Follicle stimulating hormone (FSH)


  A hormone which stimulates oestrogen production and the growth of follicles (egg-sacs) in the ovary. It is secreted by the pituitary gland.
• Hormone


  A chemical substance, produced by a gland and carried by the blood, which alters the activity of specific target organs (and is then destroyed by the liver)
• Hypothalamus


  Part of the brain which controls water balance, temperature and secretion of hormones by the pituitary gland.
• Interstitial cell stimulating hormone (ICSH)


  A hormone produced by the pituitary gland that stimulates the production of testosterone in the testes.
• Luteinising hormone (LH)


  A hormone secreted by the pituitary gland, which stimulates ovulation.
• Menstrual cycle


  Recurring series of events in the human female reproductive system.
• Menstruation (or period)


  The loss of blood and tissue from the lining of the uterus through the vagina during the menstrual cycle.
• Negative feedback mechanism


  Mechanism to lower raised levels of something, and to raise reduced levels of something.
• Oestrogen


  A female sex hormone produced in the ovaries, responsible for puberty in girls and the regulation of the menstrual cycle.
• Ovulation


  The release of an egg (ovum) from a follicle in the ovary. It usually occurs around the mid-point of the menstrual cycle.
• Progesterone


  Sex hormone produced by the ovaries and placenta.
• Puberty


  The physical changes a child's body goes through when developing into an adult.
• Testosterone


  Male sex hormone produced in the testes, which is responsible for puberty in boys.
• Hormonal influence on puberty

  1. Pituitary gland is stimulated to release FSH, LH or ICSH by a releaser hormone produced in the hypothalamus

  2. FSH, LH and ICSH travel through the blood to the testes and ovaries

  3. ICHS stimulates the testes to produce testosterone

  4. LH stimulates the ovaries to produce oestrogen
• Menstrual cycle


  1. Day 1: Menstruation occurs

  2. By day 5: Loss of blood stops, lining of uterus begins to re-grow, egg cell starts to mature

  3. Around day 14: Mature egg cell is released from ovary (ovulation)

  4. If egg is not fertilised: Lining of uterus begins to break down, cycle repeats
• Hormonal influence on sperm production

  1. FSH promotes sperm production in seminiferous tubules

  2. ICSH stimulates interstitial cells to release testosterone

  3. Testosterone stimulates sperm production and activates prostate gland and seminal vesicles

  4. Negative feedback system regulates testosterone production
• Hormonal influence on menstrual cycle

  1. Follicular phase: FSH stimulates follicle development and oestrogen production

  2. Oestrogen stimulates endometrium growth and affects cervical mucus

  3. Oestrogen inhibits FSH, peak levels stimulate LH surge triggering ovulation

  4. Luteal phase: Corpus luteum secretes progesterone, inhibits FSH and LH

  5. If no fertilisation: Corpus luteum degenerates, progesterone drops, menstruation occurs

  6. If fertilisation: Corpus luteum maintained, progesterone levels remain high
• The menstrual cycle takes approximately 28 days, but it can be slightly more or less than this. The cycle stops while a woman is pregnant.