Reproduction
Topic 6
Standard Level
STARTER: How much do you remember from IGCSE?
Learning Ojectives
• Draw and label diagrams of the adult male and female
reproductive systems.
• Outline the role of hormones in the menstrual cycle,
including FSH (follicle stimulating hormone), LH (luteinizing
hormone), estrogen and progesterone.
• Annotate a graph showing hormone levels in the menstrual
cycle, illustrating the relationship between changes in
hormone levels and ovulation, menstruation and thickening
of the endometrium.
• List three roles of testosterone in males
Hormones
• Four main hormones involved in controlling
menstruation
Name
Made…
Function
FSH
Pituitary
Stimulates one egg cell
to develop (become
follicle)
Oestrogen
Follicle (ovary)
Stimulates rebuilding
of the uterus wall
LH
Pituitary
Stimulates follicle to
burst and release the
ovum
Progesterone
Corpus Luteum (ovary)
Completes
development of uterus
wall, promotes
glycogen storage
The Menstrual Cycle
• During the first week of the cycle the pituitary
gland is stimulated
• It releases follicle stimulating hormone (FSH)
Annotate your Menstrual cycle
handout as we move through the
next few slides
• FSH stimulates a potential egg cell
in the ovary
• The cells around the ovum also
develop. This is called a follicle.
• Follicle cells secrete oestrogen.
• Oestrogen stimulates rebuilding
of uterus wall.
An oocyte (pre-ovum)
surrounded by follicle
cells
False colour SEM of human uterus wall, approximately 13 days into cycle. Green
cells are secretory, and orange cells are ciliated
• Initial concentrations of oestrogen are low.
• The low concentration has a negative feedback effect on the
secretion of FSH.
Negative feedback lowers FSH
concentration
• As follicle grows is
produces larger
concentrations of
oestrogen.
• At a certain threshold, its
effect reverses.
• It now has a positive
feedback effect on
secretion of FSH from
pituitary.
• Also stimulates pituitary
gland to release
luteinising hormone (LH)
Positive feedback from
increasing oestrogen
concentration causes increase in
FSH and LH from pituitary gland.
Follicle gets bigger – releases
more oestrogen
• Peak of LH causes follicle to burst and release
ovum
• This is ovulation (on day 14 of the cycle)
• Follicle reforms to become structure called
corpus luteum (‘yellow body’)
• LH stimulates corpus luteum to produce
progesterone.
Peak of LH causes ovulation (day
14)
Oestrogen falls because follicle is
gone, but corpus luteum still
produces some.
Ovulation – ovum released from
follicle. Follicle become corpus
luteum
• Progesterone completes uterus wall.
• Increases blood supply and promotes
glycogen storage.
• Rising concentrations of progesterone and
oestrogen have negative feedback effect on
FSH and LH.
• This prevents new follicles forming.
Fall in FSH and LH due to
negative feedback with
oestrogen and progesterone
Progesterone produced by
corpus luteum. Inhibits FSH and
LH
Corpus luteum – produces
progesterone. Uterus wall fully
completed.
• Fertilisation must occur within 2 days of ovulation.
• Embryo takes 3 days to reach the uterus and implant.
• If no embryo implants within a week the corpus luteum
starts to break down.
• Progesterone and oestrogen concentrations fall. Uterus
wall begins to break down.
• FSH no longer inhibited, so begins to rise.
• Cycle begins again
FSH and LH totally inhibited
Breakdown of corpus luteum
causes fall in progesterone and
oestrogen
Corpus luteum begins to break
down if no embryo has
implanted a week after
ovulation
FSH begins to rise since it’s not
inhibited by oestrogen and
progesterone
Low levels of progesterone and
oestrogen because there is no
follicle or corpus luteum
Uterus wall breaks down due to
low levels of oestrogen and
progesterone
New egg cell stimulated by rising
FSH levels
Menstrual cycle summary
Stick the statement into the correct column!
DAY 1-4
FOLLICULAR PHASE
DAY 5-14
OVULATORY PHASE
DAY 14-28
LUTEAL PHASE
STARTER: GROUP ACTIVITY:
Calculate
a) the magnification of the sperm
b) The maximum diameter of the main body of the ovum
GROUP ACTIVITY:
Calculate
a) the magnification of the sperm
b) the maximum diameter of the main body of the ovum
a) magnification
measured length
scale bar label
41mm = 41000 µm
45µm
45µm
=
X 911
b) diameter of ovum
measured length
magnification
70mm
X 911
=
0.0768 mm
=
76.83µm
Learning Ojectives
• Outline the process of in vitro fertilization
(IVF).
• Discuss the ethical issues associated with IVF.
CLASS ACTIVITY: Can you narrate each phase of the
menstrual cycle with reference to specific hormones?
STARTER: Complete this flow chart in your workbooks!
TIMED INDIVIDUAL ACTIVITY: