Female Reproduction Notes 2024 PDF

Ova Production o Controlled by FSH, LH, oestrogen and progesterone. o Each ovary is surrounded by a layer of germinal epithelial cells that divide by meiosis to produce ova. o The germinal epithelial cells initially divide to form primary follicles. Each ovary contains many primary follicles....

Ova Production o Controlled by FSH, LH, oestrogen and progesterone. o Each ovary is surrounded by a layer of germinal epithelial cells that divide by meiosis to produce ova. o The germinal epithelial cells initially divide to form primary follicles. Each ovary contains many primary follicles. o Each primary follicle contains an immature ovum. o At puberty, the primary follicle develops into a secondary follicle which contains a mature ovum. o Once a month, the secondary follicle develops into a Graafian follicle which contains a fully developed / mature ovum. o The Graafian follicle secretes oestrogen. o One a month , the Graafian Follicle bursts and the mature ovum is released from ovary into the fallopian tube – ovulation. o This ovum may or may not get fertilized in the fallopian tube. o If fertilisation occurs – then only will meiosis 2 occur to produce a haploid ovum. o No fertilisation occurs – meiosis 2 does not occur, unfertilized ovum passes out of body with endometrium, as blood – menstruation. o After ovulation, the remainder of the Graafian follicle left behind in ovary becomes the corpus luteum. o The corpus luteum secretes progesterone. o If no pregnancy occurs – corpus luteum disintegrates. o If pregnancy occurs – corpus luteum remains and increases in size for first 3 months of pregnancy, continuing to secrete progesterone.  The Menstrual Cycle o Starts at puberty when hormones are secreted. o Menstrual cycle divided into 4 stages: Stage 1 – Menstruation (Day 1 – Day 5) o Lining of the uterus – endometrium, breaks away, together with unfertilized ovum - bleeding occurs. o This is triggered by a drop in oestrogen and progesterone. o At the same time, a new ovum starts to mature in ovary – stimulated by an increase in FSH. Stage 2 – Repair phase (Day 6 – Day 13) o Ovum takes about 14 days to reach maturity. o During this time the endometrium starts to repair itself which prepares for possible implantation of fertilized ovum. o The repair process is controlled by high levels of oestrogen. o Ovum released from ovary on Day 14 – ovulation. Triggered by high levels of LH. o Ovum travels along the oviduct to reach the uterus. Stage 3 - Receptive Phase (Day 15 Day 21) o Endometrium is well developed & ready to receive fertilized ovum i.e., if fertilization has taken place. Stage 4 – Pre-Menstrual Phase (Day 22 – Day 28) o If no fertilization & implantation, endometrium starts to break down. o By day 28, the endometrium breaks down completely. o Menstruation will start again – endometrium & unfertilized ovum will be lost.  Hormonal Control of the Menstrual Cycle o 4 hormones work together during this cycle. o The pituitary gland produces 2 gonadotrophic hormones i.e., FSH & LH. o The ovary produces reproductive hormones i.e., oestrogen & progesterone. o Oestrogen feeds back to the pituitary gland to lower the levels of FSH & stimulate the secretion of LH. o When oestrogen decreases, pituitary gland is stimulated to release more FSH. o High progesterone levels feeds back to the pituitary gland to decrease levels of FSH & LH. o When progesterone decreases, pituitary gland is stimulated to release more FSH & LH. Female hormonal control of reproduction HYPOTHALAMUS pituitary gland FSH LH OVARIES OESTROGEN PROGESTERONE CONTROLS SECONDARY MAINTAINS THE SEXUAL CHARACTERISTICS ENDOMETRIUM DURING AND REPAIRS THE PREGNANVY ENDOMETRIUM Oestrogen only, is secreted before ovulation by the Graafian follicle. Progesterone and some Oestrogen is secreted after ovulation by Corpus Luteum.  The Menstrual Cycle (Use this as a guide only) Ovarian Cycle Uterine Cycle Occurs in ovary Occurs in uterus Follicular Phase (6-13) Menstrual Phase *(1-5) Development of Menstruation takes place Graafian Follicle Repair Phase Ovulatory Phase * (14) Repair / thickening of endometrium Ovulation Secretory Phase (15-28) Luteal Phase Secretion of glucose by Formation of endometrium to nourish Corpus Luteum fertilized egg  Before ovulation, high levels of Oestrogen in the blood cause a negative feedback to occur, thus inhibiting FSH – no more follicles need to mature since there is already 1 mature Graafian Follicle. High levels of Oestrogen also cause a positive feedback to occur, thus stimulating LH (LH surge) which will assist with ovulation. After ovulation, negative feedback only exists if there is pregnancy, since the blood will have high levels of progesterone. This negative feedback inhibits production of FSH and LH so the development of further follicles is prevented, hence no ovulation/menstruation when a female is pregnant.  If no pregnancy occurs, progesterone and oestrogen levels in the blood decreases and a negative feedback stimulates production of FSH and LH and the cycle starts again. If there is pregnancy, Corpus Luteum secretes progesterone for first 3 months. After 3 months, Corpus Luteum degenerates and placenta, which would now be fully developed, will secrete progesterone for the rest of the pregnancy. Summary of the Menstrual Cycle Pituitary gland secretes FSH, which stimulates the ovary to produce a mature follicle. Follicle matures into Graafian follicle & secretes oestrogen. Oestrogen stimulates endometrium to grow & thicken. Increase in oestrogen, inhibits FSH so that another follicle is not produced. By day 14 LH is produced by pituitary gland. LH assist with ovulation by causing the Graafian follicle to burst & release ovum. Remains of Graafian follicle becomes corpus luteum, which secretes progesterone. Progesterone takes over function of oestrogen & maintains the endometrium. If there is no implantation – corpus luteum degenerates. This causes amount of progesterone to decrease. By day 28, progesterone levels are very low & endometrium can no longer be maintained, it will be lost/shed – menstruation. Low levels of progesterone stimulates the pituitary gland to produce FSH & the cycle starts again.