Recap questions chapter 8b Where is each egg contained? What happens after ovulation? What is the function of FSH? What is the function of LH? What are the functions of oestrogen and progesterone?

Sex Organs and Hormonal Control Menstruation Higher Human Biology Unit 2 Chapter 8c

Learning Intentions What is the menstrual cycle? What is the follicular phase? What is the luteal phase? What occurs after fertilisation? What is the role of the cervix in fertility? How does temperature change during the menstrual cycle? What is cyclical and continual fertility?

What is the menstrual cycle? The interaction of the female gonadotrophic and sex hormones Lasts, on average, 28 days Continuous – each cycle stimulates the beginning of the next The first day of each cycle is the first day of menstruation (menstrual blood flow)

What is the follicular phase? The first phase of the menstrual cycle FSH stimulates development and maturation of Graafian follicle and production of oestrogen from ovarian tissues

Follicular phase cont’d Oestrogen concentration increases  repair and proliferation of endometrium  surge in production of LH (and FSH) around day 14 of cycle oestrogen LH

Follicular phase cont’d Rapid increase in LH  ovulation - wall of Graafian follicle ruptures and egg released - egg swept along oviduct by cilia - egg only lasts 3-4 days, if fertilisation does not occur in this time the egg degenerates.

What is the luteal phase? Second phase of cycle After ovulation LH stimulates Graafian follicle to become the corpus luteum Corpus luteum is a gland-like structure that secretes oestrogen and progesterone Increase in concentration of progesterone stimulates further development of endometrium - thick, vascular and spongy - now ready for implantation of blastocyst

Negative feedback If no fertilisation occurs - high concentration of oestrogen and progesterone  inhibition of production of LH and FSH by anterior pituitary  decrease in concentration of LH and FSH Low concentrations of FSH and LH lead to: - no new follicles develop - degeneration of corpus luteum - progesterone levels drop - low levels of oestrogen and progesterone around day 28 cause the endometrium to degenerate - menstruation occurs

What occurs after fertilisation? If fertilisation occurs a zygote is formed. The zygote secretes hormone human chorionic gonadotrophin (HCG) Has same effect as LH - corpus luteum is maintained  progesterone levels maintained  menstruation prevented After implantation of the embryo in the uterus the corpus luteum degenerates and the placenta continues the production of progesterone