sexual reproduction in the human. learning objectives outline the stages in the menstrual cycle...

Sexual Reproduction in the Human

Learning objectives

• Outline the stages in the menstrual cycle

• Discuss the role of hormones in the menstrual cycle

• Discuss the Cause/Prevention/Treatment for fibroids or for endometriosis

Depth of treatment

• Detailed study of the menstrual cycle and hormonal control

Menstrual Cycle

Hormonal control in the menstrual cycle

• Four hormones involved:– FSH (Follicle Stimulating Hormone)– Oestrogen – LH (Luteinising Hormone)– Progesterone

• Each hormone causes the production of the hormone following it and inhibits the hormone preceding it

FSH – Follicle Stimulating Hormone

• Produced by pituitary gland• Produced early in the cycle (days 1-5)• Stimulates a few potential eggs to develop,

surrounded by graafian follicles• Only one usually survives• Sometimes used in fertility treatments to

stimulate ovaries to produce eggs – often lots of eggs develop. This explains some multiple births

• Each graafian folllicle then produces oestrogen

Oestrogen

• Produced by the graafian follicle in the ovary

• Produced from days 5 -14

• Causes the endometrium to develop

• Inhibits FSH ensuring no further eggs develop (useful in contraceptive pill)

• High levels of oestrogen just before day 14 stimulate release of LH

LH - Luteinising Hormone

• Produced by the pituitary gland

• Produced on day 14

• Causes ovulation

• Causes the remains of graafian follicle to develop into corpus luteum

• Corpus luteum makes final hormone in the cycle progesterone (along with small amounts of oestrogen)

Progesterone

• Produced by the Corpus Luteum in the ovary

• Produced from days 14-28

• Maintains structure of endometrium

• Inhibits FSH to stop further eggs developing

• Inhibits LH to stop further ovulation and pregnancies

• Prevents contractions of the uterus

Learning Check

• List the four hormones involved in the menstrual cycle

• In each case state where it is produced

• Give a function for each hormone

Contemporary issues and technology

• Menstrual disorders– one example of a menstrual disorder from the

following: endometriosis and fibroids– one possible cause, prevention and treatment

Menstrual disorder (Fibroids)

• Fibroids are tumours of the uterus

• They are the result of the overproduction of cells

• They do not invade other tissues and do not spread (benign)

• Slow growing - range from the size of a pea to the size of a melon

• Common between ages of 35 and 45

• Small fibroids often produce no symptoms

• As they enlarge they produce heavy and prolonged menstrual bleeding (this can lead to anaemia, pain, miscarriage or infertility)

Menstrual disorder (Fibroids)

Cause

• Cause is uncertain

• May be an abnormal response to oestrogen

• Can occur in women taking the contraceptive pill

Prevention and treatment

• Small fibroids require no treatment just monitoring to check their growth

• Large fibroids can be removed by surgery

• If many large fibroids are present a Hysterectomy may be necessary. This is where the uterus is removed

Menstrual disorder (Endometriosis)

• Growth of endometrial cells outside the uterus (often in fallopian tube)

• Normally endometrium is shed each month in the menstrual cycle. In endometriosis misplaced endometrium is unable to exit the body

• Results in internal bleeding, inflammation of surrounding area and pain

• Formation of scar tissue may result• If in the fallopian tube this can interfere with the

passage of eggs to the uterus (infertility)

Cause

• Exact cause remains unknown

• Several theories (response to excess oestrogen creation)

Prevention and treatment

• No known cure

• Hysterectomy (removal of uterus) - no guarantee that symptoms will disappear

• Medication can be taken to interfere with hormones resulting in a reduction or elimination of menstrual flow