Menstrual Cycle PDF

The Menstrual Cycle Year 11 Human Biology  Menstrual cycle – a cycle where changes in the endometrium occur in preparation for a developing embryo if fertilisation occurs. Closely linked with the stages of the ovarian cycle. The Divided into...

The Menstrual Cycle Year 11 Human Biology  Menstrual cycle – a cycle where changes in the endometrium occur in preparation for a developing embryo if fertilisation occurs. Closely linked with the stages of the ovarian cycle. The Divided into 5 stages; Menstrual Menstruation, pre-ovulation, ovulation, secretion and Cycle pre-menstruation Menarche – The commencement of puberty. The first menstrual period. Menopause – Period of years when the cycle becomes irregular, gradually slowing and then ceasing completely. Usually around 45-55. Menstrual cycle brief summary  Menstruation (day 1-4) Menstruation  Days 1-4 of the cycle.  Broken down endometrium, capillaries and mucus are lost through the vagina.  Referred to as a “period”.  Occurs if fertilisation has not occurred for the ovum produced in the previous cycle.  Pre-ovulation (day 5-12) Pre-ovulation  Days 5-12 of the cycle  The endometrium begins to repair and become thicker and softer.  The number of blood vessels and mucus-secreting glands increases.  Happens simultaneously with development of primary follicle in the ovary.  Ovulation (day 13- 15) Ovulation  Days 13-15 (usually on the 14th day of the cycle).  The mature follicle in the ovary ruptures and the ovum is released.  Endometrium continues to develop.  Secretion (day 16- 20) Secretion  Days 16-20 of the cycle.  Endometrium continues to thicken and soften in preparation for implantation.  Glands of the endometrium, cervix and fallopian tubes begin to produce a glycogen-rich, watery secretion.  Occurs whilst the ovum moves through the reproductive system and corpus luteum forms.  Pre-menstruation (day 21-28) Pre-ovulation  Days 21-28 of the cycle.  If fertilisation doesn’t occur, the endometrium begins to degenerate.  Occurs as the corpus luteum degenerates in the ovary. The Menstrual and Ovarian Cycle