Reproductive system 2 Flashcards
Hormone production and meiosis in males:
1) APL sends FSH to the testes to stimulate the primary spermatocyte’s first meiotic division
2) APL sends LH to interstitial cells to stimulate them to produce testosterone which targets the secondary spermatocyte (produced from meiosis of the primary) and stimulates its meiosis
3) In the secondary meiosis, spermatids are produced and they form spermatozoa, which mature in the epididymis and become sperm cells. Meiosis begins in puberty
What is testosterone responsible for?
the development of primary (male genitalia) and secondary sex traits, fertility, and production of sperms
hormone production and meiosis in females:
1) First meiosis happens before birth but due to lack of sex hormones, the second cannot occur so the cells are all arrested in the prophase of the primary meiotic division (bivalents, nondisjunction hazard)
2) One oocyte per month matures since puberty. There are around 200 000 primary oocytes in the ovary.
3) Each main primary oocyte is enclosed in its own primary Graafian follicle made of follicular cells that produce estrogen. Follicles enlarge as oocytes do (by mitotic division, more cells = more estrogen produced = thicker endothelium) and also release follicular fluid as they do so
4) When the pressure in the follicle reaches a threshold, it bursts, and ovulation happens.
5) The primary oocyte is stimulated by FSH to continue its first meiotic division and by that process forms a secondary oocyte –> the follicle is now referred to as a mature Graafian follicle
6) Secondary oocyte enters the second meiotic division but is arrested in metaphase II when ovulation happens.
7) Meiosis completes when fertilization occurs
Corpus luteum vs corpus albicans
Corpus luteum – follicle turns into a yellow body after ovulation, it produces large quantities of estrogen and progesterone for 10-12 days due to its steroid reserves and in that way maintains the thickness of the endometrium
Corpus albicans – corpus luteum turns into it after 10-12 days, it is a scar on the ovary tissue, at the place of ovulation, it produces no hormones and this is when the endometrium sheds
Gametogenesis in males
Germ cell (2n) – (mitosis, growth, differentiation) –>
spermatogonia (2n) – (growth and differentiation) –>
primary spermatocyte (2n) – (1st meiosis) –>
secondary spermatocyte (n) – (2nd meiosis) –>
spermatids (n) –>
spermatozoa –>
mature sperm cells
Gametogenesis in females
Germinal epithelial cells (2n) – (mitosis, growth, differentiation) –>
oogonia (2n) – (growth and differentiation) –>
primary oocyte (2n, arrested in pro I) – (unequal cytokinesis) –>
secondary oocyte (n, arrested in meta II) – (fertilization) –>
3 polar bodies and an ovum
Compare and contrast male and female gametogenesis
Male: 4 sperm cells, large number of gametes produced in total through life, gametes form continuously from puberty, they release gametes at any time
Female: 1 ovum and 3 polar bodies, around 400 through life released and starting to do so before birth, release of gametes in a monthly cycle
Menstrual cycle
Two cycles, menstrual and ovarian are coordinated and controlled by brain hormones (FSH and LH) and from the ovary (estrogen and progesterone) – ensuring that the conditions in the uterus required to support pregnancy at the time of development and release of egg – two phases: follicle and luteal (follicular length varies, luteal phase is always two weeks)
List and explain the function of each hormone in the menstrual cycle
- FSH – released by the APL, stimulating the maturation of a new follicle with an immature egg cell (completion of meiosis I and start of meiosis II), produces estrogen
- LH (luteinizing hormone) – released by APL in response to the secretion of estrogen by the primary follicle cells (positive feedback), responsible for final maturation of the follicle, causes ovulation and corpus luteum formation (estrogen and progesterone production) – peaks at ovulation
- Estrogen – released in both phases, stimulates the development of female reproductive organs and sex traits, responsible for the thickening of the endometrium – the peak of estrogen secretion at day 12 causes the pituitary to release LH which causes ovulation (the release of the secondary oocyte from the mature follicle)
- Progesterone – responsible for the thickening of the endometrium and its maintenance during the 2nd phase of the cycle, together with estrogen, inhibits further LH and FSH secretion (negative feedback) in order to maintain the endometrium, and this lasts until the corpus albicans is created (no more estrogen and progesterone) and then a FSH is secreted again and a new cycle begins
Explain the entire mechanism – connecting the brain and ovaries
- pituitary gland slightly increases FSH concentration due to the gonadotropin-releasing hormone
- follicular cells of the primordial follicle activated
- primary oocyte inside is released from prophase I
- increase in estrogen levels
- thickening of the uterine lining
- FSH concentration drops (due to high estrogen levels)
- LH released and causes ovulation
- estrogen levels drop (due to high LH concentration)
- follicle fills with steroids, turns into corpus luteum and produces estrogen and progesterone
- endometrium thickens even more
- corpus albicans forms after steroid reserves run out and estrogen and progesterone production stopped
- the endometrium sheds
How is estrogen/progesterone and LH/FSH production a type of negative feedback mechanism?
What is the premenstrual syndrome?
When estrogen and progesterone levels are high, LH and FSH levels low (possibility of a pregnancy to happen, don’t want to begin another ovulation)
(PMS) is a steep drop in hormones (1-2 days before the menstruation)
