sexual reproduction in the human (extended study)

Sexual Reproduction in the Human

(Extended Study)

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

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

Events when pregnancy does not occur

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 and 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

Syllabus

Depth of treatment

Detailed study of the menstrual cycle and hormonal control

Contemporary issues and technology

Menstrual disorders one example of a menstrual disorder from the

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