Reproduction Topic 6 Standard Level. STARTER: How much do you remember from IGCSE?

Reproduction

Topic 6Standard 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

menstruationName 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 summaryStick the statement into the correct column!

DAY 1-4FOLLICULAR PHASE

DAY 5-14OVULATORY PHASE

DAY 14-28LUTEAL PHASE

STARTER: GROUP ACTIVITY: Calculate a) the magnification of the spermb) The maximum diameter of the main body of the ovum

GROUP ACTIVITY: Calculate a) the magnification of the spermb) the maximum diameter of the main body of the ovum

a) magnificationmeasured length scale bar label

41mm = 41000 µm45µm 45µm

= X 911

b) diameter of ovummeasured length magnification

70mmX 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: