Menstrual Cycle PDF

MENSTRUAL CYCLE Created @September 30, 2024 12:51 PM Class SCIENCE - BIOLOGY Type Lecture Reviewed MENSTRUAL CYCLE The menstrual cycle is a cycle which begins at puberty to prepare the body...

MENSTRUAL CYCLE Created @September 30, 2024 12:51 PM Class SCIENCE - BIOLOGY Type Lecture Reviewed MENSTRUAL CYCLE The menstrual cycle is a cycle which begins at puberty to prepare the body for pregancy. It lasts around 28 days but can be shorter or longer, especially if a young person has just started having periods. MENSTRUAL PHASE (DAY 1-5) It begins on the first day of menstruation and lasts till the 5th day of the menstrual cycle. The following events occur during this phase: 1. The uterus sheds its inner lining of soft tissue and blood vessels which exits the body from the vagina in the form of menstrual flruid. Blood loss of 10ml to 80ml is considered normal. 2. You may experience abdominal cramps. These cramos are caused by the contraction of the uterine and the abdominal muscles to expel the menstrual fluid. FOLLICULAR PHASE (DAY 1-13) This phase also begins on the first day of menstruation, but it lasts till the 13th day of the menstrual cycle. The following events occure during this phase: 1. The pituitary gland secretes a hormone that stimulates the egg cells in the ovaries to grow. 2. One of these egg cells begins to mature in a sac-like-structure called follicle. It takes 13 days for the egg cell to reach maturity. MENSTRUAL CYCLE 1  3. While the egg cell matures, its follicle secretes a hormone that stimulates the uterus to develop a lining of blood vessels and soft tissue called endometrium. OVULATION PHASE (DAY 14) On the 14th day of the cycle, the pituitary gland secrets a hormone that causes the ovary to release the matured egg cell. The released egg cell is swept into the fallopian tube by the cilia of the fimbriae. Fimbriae are finger like projections located at the end of the fallopian tube close to the ovaries and cilia are slender hair like projections on each Fimbria. LUTEAL PHASE (DAY 15-28) The phase begins on the 15th day and lasts til the end of the cycle. The following events occur during this phase: 1. The egg cell released during the ovulation phase stays in the fallopian tube for 24 hours. 2. If a sperm cell does not impregnate the egg cell within that time, the egg cell disintegrates. 3. The hormone that causes the uterus to retain its endometrium gets used up by the end of the menstrual cycle. This causes the menstrual phase of the next cycle to begin. THE MENSTRUAL CYCLE ANSD HORMONES: DAY 1-5 Menstruation occurs if the egg is not fertilized by a sperm. Blood is lost. Day 1-13 FSH causes the egg to mature in the ovary DAY 14 LH stimulates the release of an egg DAY 15-28 Progesterone maintains the lining of the uterus, ready for a fertilized egg. MENSTRUAL CYCLE 2  MENSTRUAL CALENDAR Menstrual Cycle is also used as a natural birth control which we called the Calendar Rhythm Method. However, this is NOT applicable for women with irregular menstrual cycles, or these which last less then 25 or more than 32 days. If your average menstrual cycle is 8 days, you ovulate around day 14 and your most fertile days are days 11-16. But why? Sperm cells can live inside the body of a female for 3-4 days waiting for a mature egg cell. While egg cell dies after 3 days from the ovulation day. That is a 3-4 days before ovulation and 3 days after. VAGINA The vagina is a muscular tube tube which connects the cervix to outside the body. It is where the penis enters during sexual intercourse and where the baby exits the body during child birth. The vagina is also where the menstrual blood (period) leaves the body. ESTROGEN A female sex hormone made in the ovaries. It is responsible for puberty in girls and regulating the menstrual cycle. It stops FSH being produced to prevent more than one egg being released each cycle, it repairs and thickens the uterus lining and stimulates the pituitary gland to release LH. PITUITARY GLAND The pituitary gland is where FSH and LH are produced. THE OVARIES The ovaries produce estrogen and progesterone. THE PLACENTA If a woman become pregnant, the placent produces progesterone to maintain the lining od the uteru sand to stop menstruation. PREGNANCY MENSTRUAL CYCLE 3  Fertilisation occurs when the sperm and egg join during sex. The fertilised egg implants in the lining of the uterus. This is the start of pregnancy, During pregnancy, menstruation does not happen, so periods do not occur. MENOPAUSE When women reach a certain age, they stop having periods. They stop menstruating and no longer have a regular cycle. This is called the menopause. It usually occurs around the age of 50 but can happen earlier or later depending on the person. MENSTRUAL CYCLE 4