sexual reproduction in the human (extended study)
TRANSCRIPT
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