Summary of Ciclo sexual femenino: hormonal, uterino y ovárico | Fisiología de las hormonas sexuales femeninas

Summary of the Video: "Ciclo sexual femenino: hormonal, uterino y ovárico | Fisiología de las hormonas sexuales femeninas"

This video provides a comprehensive overview of the female sexual cycle, focusing on the hormonal, uterine, and ovarian aspects. It explains the anatomy, physiology, hormonal regulation, and phases of the menstrual cycle, emphasizing the interactions between the hypothalamus, pituitary gland, and ovaries, as well as the effects of Estrogen and Progesterone on the uterus and other tissues.

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Main Ideas and Concepts

1. Anatomy Overview

• External and internal female reproductive anatomy: labia majora/minora, vaginal vestibule, urethra, vaginal canal, uterine cervix, uterine body, fallopian tubes (oviducts), and ovaries.
• Fallopian tubes have specific segments: uterine portion, ampulla (fertilization site), infundibulum (contacts ovary via fimbriae).
• Uterine histology:
  • Outer layer: serosa (or adventitia).
  • Myometrium: thick muscular layer, highly vascularized.
  • Endometrium: mucosal lining with basal and functional layers; functional layer subdivided into compact, spongy, and basal layers.
  • Functional layer is shed during menstruation; basal layer regenerates it under Estrogen influence during proliferative phase.

2. Ovarian Structure and Follicle Development

• Ovary covered by germinal epithelium (misnamed), tunica albuginea (dense connective tissue), cortex (follicles), and medulla (fibroelastic connective tissue).
• Oogenesis:
  • Primordial germ cells → oogonia → primary oocytes (arrested in prophase I until puberty).
  • At puberty, FSH resumes meiosis → secondary oocyte + first polar body.
  • Secondary oocyte arrests in metaphase II until fertilization.
  • Fertilization completes meiosis → zygote formation.
• Folliculogenesis:
  • Primordial follicle → primary follicle (single layer of granulosa cells).
  • Primary follicle → secondary follicle (multiple granulosa layers, formation of zona pellucida, theca interna and externa layers).
  • Secondary follicle → tertiary (antral or Graafian) follicle with fluid-filled antrum.
  • Ovulation triggered by LH surge causing follicle rupture and oocyte release with corona radiata and zona pellucida.
  • Corpus luteum forms from leftover follicular cells, secretes Progesterone.
  • If fertilization occurs, hCG maintains Corpus luteum; if not, Corpus luteum degenerates.

3. Hormonal Regulation and Feedback

• Hypothalamus secretes GnRH (gonadotropin-releasing hormone) in a pulsatile manner.
• GnRH stimulates anterior pituitary gonadotrophs to release FSH and LH.
• FSH stimulates granulosa cells; LH stimulates theca cells.
• Negative feedback by Estrogen and Progesterone on hypothalamus and pituitary regulates gonadotropin secretion.
• Pulsatile secretion of GnRH is crucial; constant stimulation leads to receptor downregulation and decreased gonadotropins.
• GnRH receptor agonists and antagonists can both decrease gonadotropin secretion by disrupting pulsatility or blocking receptors.

4. Steroid Hormone Synthesis

• Theca cells (LH receptors) convert cholesterol → pregnenolone → androgens (androstenedione, testosterone).
• Granulosa cells (FSH receptors) convert androgens → estrogens (estradiol mainly) via aromatase enzyme.
• Estrogens circulate bound to carrier proteins; free Estrogen diffuses into target cells, binds Estrogen receptors, and modulates gene expression.
• Estrogen effects include tissue proliferation, protein synthesis, and mitosis.

5. Physiological Effects of Estrogen and Progesterone

• Estrogen:
  • Promotes breast stromal development, duct growth, fat deposition.
  • Maintains bone density by inhibiting bone resorption.
  • Stimulates endometrial proliferation and uterine tube ciliated cells.
  • Causes mild renal sodium and water retention.
  • Changes vaginal epithelium to stratified, increases fat in mons pubis, enlarges labia.
  • Increases nitric oxide production (vasodilation).
  • Increases cholesterol secretion in bile (explains higher gallstone risk in women).
  • Enhances metabolism and fat deposition in female-typical areas.
• Progesterone:
  • Stimulates mammary lobule proliferation.
  • Slight immunosuppressive effect to tolerate pregnancy.
  • Increases uterine secretory activity.
  • Reduces uterine contractions by inhibiting oxytocin receptors.
  • Increases secret

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Educational

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