Key Area 2

(c) Hormonal control of the menstrual cycle

Time for a biggie. The Menstrual Cycle. Take your time here - read the information carefully and consider the diagrams that are included. This is worth investing the time. The menstrual cycle can be a right pain - but it is the (not-so) secret to cyclical female fertility.

Something to Read...

Open the document below and read the mandatory course notes provided by SQA for this Key Area. You may wish to use your home learning time to copy these notes into a jotter or choose a digital presentation format that suits your learning style.

CfE Higher Human Biology Unit 2, Key Area 2c

Something to Watch...

The link for the NHS Menstrual Cycle animation takes you to a general NHS page on "period pain" - scroll to the bottom of this page for the animation.

Something to look at...

There are many diagrams that are needed to support your understanding of this part of the course. Have a look to see which ones help you the most.

The flowchart summarises the hormonal-control of puberty in females

The diagram to the right shows the secretion of FSH and LH from the pituitary gland. Both act on the ovaries. Within the ovaries, the FSH stimulates the maturation of the follicle; LH triggers ovulation and stimulates the development of the corpus luteum post-ovulation. The ovary itself secretes oestrogen (before ovulation) and progesterone (after ovulation).

Oestrogen is secreted by the ovaries. It promotes the proliferation of the endometrium in preparation for pregnancy. It also acts on the pituitary gland to stimulate further secretion of LH.

This diagram summarises the effect of a second ovarian hormone called Progesterone. This is secreted by the corpus luteum, after ovulation. It promotes the vascularisation of the endometrium so it has a rich blood supply in the event of a pregnancy. It also plays a role in negative feedback on FSH and LH - it inhibits further secretion of these pituitary hormones.

This shows an overview of the menstrual cycle, which is divided into 2 phases - the follicular phase (day 1 until ovulation) and the luteal phase (ovulation - day 28). The average menstrual cycle takes approximately 28 days, with the first day of menstruation regarded as day one of the cycle.

This diagram is the final one I will include. It summarises the key events that occur during the menstrual cycle.

The top chart shows the changes, over 28 days, in the relative concentrations of the pituitary hormones. The peak concentration of LH triggers ovulation, around day 14. The influence of these hormones on the developing follicle can be seen.

The middle chart shows the change, over 28 days, in the ovarian hormones and this influence these have on the endometrium.

You should be able to see:

  • Menstruation - day1

  • Follicle develops day 1-14, in line with increasing FSH

  • Endometrium develops day 1-14, in line with increasing oestrogen

  • Ovulation - day 14 - in line with peak of LH

  • Development of corpus luteum after day 14 in line with increase in progesterone concentration

  • Vascularisation of endometrium after day 14, in line with increasing progesterone levels.

Something to do...

Go to SCHOLAR to access the content shown in the image opposite.

You are now ready for your in-class lesson on hormonal control of the menstrual cycle. Remember to bring any questions or queries with you.

You are now ready to move onto Key Area 3: The biology of controlling fertility.