Female Reproductive System II Flashcards
What is oogenesis?
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)
What happens before birth?
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)
What happens from menarche till menopause - meiosis I?
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
What happens from menarche till menopause - meiosis II?
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
What does one primary oocyte form?
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)
Where does oogenesis occur?
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
What are the female reproductive hormones?
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
What is the function of GnRH, FSH and LH of the female reproductive hormones?
GnRH: stimulates release of FSH and LH
FSH: stimulates growth of ovarian follicles
LH: surges of LH involved in ovulation, formation of corpus luteum
What is the function of estradiol, inhibin and progesterone of the female reproductive hormones?
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
What is the ovarian/menstrual cycle?
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
What is mernache?
First menstrual period, occurs at age 12-13 (on average), part of puberty - orchestrated by increase in sex steroid production (estrogens) by the gonads
What is menopause?
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
What is the follicular (preovulatory) phase?
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
What is the luteal (postovalutory) phase?
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
What is the hormonal pathway of the follicular phase?
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