Female Reproductive System II

Question 1

What is oogenesis?

Answer 1

Oogenesis is the formation and development of the oocyte from oogonia. Occurs in the ovaries and requires both mitosis and meiosis
Oogenesis begins before female is born, continues through puberty when ovarian cycles begin until menopause is reached
Oocytes develop within ovarian follicles (1 oocyte per follicle)

Question 2

What happens before birth?

Answer 2

Female born with all oocytes she will have for her lifespan
Before birth oogonium are divided by mitosis and oogonia differentiate to form primary oocytes, in meiosis I the oocyte halts at prophase I within primordial follicle
Many primary oocytes undergo atresia (cell death)

Question 3

What happens from menarche till menopause - meiosis I?

Answer 3

In puberty we are under influence of GnRH from hypothalamus and a small number of follicles are recruited each ovarian/menstrual cycle. Only one oocyte will complete development and ovulate (within dominant follicle), primary oocyte completes meiosis I, forms a secondary oocyte and 1st polar body

Question 4

What happens from menarche till menopause - meiosis II?

Answer 4

Secondary oocyte starts meiosis II, halts at metaphase II
If oocyte interacts with spermatozoa(fertilisation) completion of meiosis II occurs, genetic information combines and zygote forms
If not fertilised oocyte undergoes cell death and never complete meiosis

Question 5

What does one primary oocyte form?

Answer 5

Primary oocyte, 2n=46, ultimately forms one ova, n=23, from secondary oocyte, n=23, three polar bodies, n=23, also form however undergo atresia (degeneration)

Question 6

Where does oogenesis occur?

Answer 6

Oocytes develop within developing follicle, follicles are multilayered, contain granulosa cells and theca cells. Granulosa cells produce estradiol, some are found around the oocyte. In ovulation the oocyte and corona radiata (provides protection) are released into peritoneal cavity

Question 7

What are the female reproductive hormones?

Answer 7

Hypothalamus releases GnRH (gonadotrophin releasing hormone)
Anterior pituitary releases FSH (follicle stimulating hormone) and LH (luteinizing hormone)
Ovary (follicles) release estradiol and inhibin
Ovary (corpus luteum) releases inhibin and progesterone

Question 8

What is the function of GnRH, FSH and LH of the female reproductive hormones?

Answer 8

GnRH: stimulates release of FSH and LH
FSH: stimulates growth of ovarian follicles
LH: surges of LH involved in ovulation, formation of corpus luteum

Question 9

What is the function of estradiol, inhibin and progesterone of the female reproductive hormones?

Answer 9

Estradiol: assists follicle growth, bone and muscle growth, endometrial growth, secondary sex characteristics
Inhibin: negative feedback to anterior pituitary to suppress FSH
Progesterone: negatively feeds back to suppress GnRH (LH and FSH), endometrial maturation and maintains pregnant state

Question 10

What is the ovarian/menstrual cycle?

Answer 10

The regular cyclic changes in the ovary and uterus that prepare an oocyte/ova for fertilisation and the endometrium for embryo implantation
Occur approximately on a monthly basis (~28 days) between menarche and menopause

Question 11

What is mernache?

Answer 11

First menstrual period, occurs at age 12-13 (on average), part of puberty - orchestrated by increase in sex steroid production (estrogens) by the gonads

Question 12

What is menopause?

Answer 12

Cessation of menstruation, typically occurs in early 50s, reduction of estradiol and progesterone due to a sense of or lack of response by follicles, anterior pituitary feedback no longer active therefore FSH/LH high

Question 13

What is the follicular (preovulatory) phase?

Answer 13

Day 1-14 of menstrual cycle
Increased FSH, growing follicles secrete estradiol and inhibin, growing follicles undergo atresia except for dominant follicle, dominant follicle secretes large amounts of estradiol, high estradiol stimulates surge of LH causing follicles to rupture and ovulation to occur

Question 14

What is the luteal (postovalutory) phase?

Answer 14

Day 15-28 of menstrual cycle
Ovulated follicle collapses and forms corpus luteum, luteum secretes hormones which decrease FSH and LH secretion. If fertilisation and implantation do not occur corpus luteum involutes causing fall in progesterone and estradiol —> cycle starts again

Question 15

What is the hormonal pathway of the follicular phase?

Answer 15

Hypothalamus secretes GnRH which stimulates anterior pituitary to release FSH and LH. This stimulates the ovary to release estradiol which negatively feedbacks to the hypothalamus and anterior pituitary decreasing GnRH, FSH and LH production

Question 16

What is the hormonal pathway of the midcycle phase?

Answer 16

Hypothalamus secretes GnRH which stimulates anterior pituitary to release FSH and LH. This stimulates the ovary to release estradiol with positively feedbacks to the hypothalamus and anterior pituitary increasing GnRH, FSH and LH production

Question 17

What is the hormonal pathway of the luteal phase?

Answer 17

Hypothalamus secretes GnRH which stimulates anterior pituitary to release FSH and LH. This stimulates the ovary to release progesterone with negatively feedbacks to the hypothalamus and anterior pituitary decreasing GnRH, FSH and LH production

Question 18

What is the menstrual and proliferative phase of the menstrual cycle?

Answer 18

Days 1-14
Endometrium breaks down and bleeds during menstruation
Estradiol stimulates endometrial growth from approx days 6-14
Rapid tissue growth, including growth of glands and vasculature

Question 19

What is the secretory phase in the menstrual cycle?

Answer 19

Days 15-28
After ovulation (day 14) corpus luteum secretes progesterone which promotes endometrial maturation
Glands become secretory, spiral arterioles grow and coil

Question 20

What happens in the menstrual cycle when fertilisation and implantation does not occur?

Answer 20

Corpus luteum atrophies causing progesterone levels to fall and spiral arteries to contract. This results in endometrial tissue breaking down and bleeding occurring. Shed tissue and blood is removed via cervix and vagina