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Lab 10 Mini Lesson Learning Guides

Endocrine Physiology Mini-Lesson 1 Study Guide

Key Concepts & Definitions

  • Sex Determination vs. Sex Differentiation:

    • Sex determination is based on genotype (XX or XY chromosomes).

    • Sex differentiation refers to the development of phenotypic characteristics (e.g., reproductive organs, secondary sex traits).

  • Gamete Formation (Gametogenesis):

    • Two meiotic divisions reduce chromosome number from diploid (46, double chromatid) to haploid (23, single chromatid).

  • Primary Secretions of the Gonads:

    • Ovaries: Estrogen and Progesterone

    • Testes: Testosterone

    • Aromatase converts testosterone into estrogen.

    • 5-α-reductase converts testosterone into DHT.

  • HPG Axis Regulation of Gonadal Function:

    • Hypothalamus releases GnRH → Stimulates anterior pituitary → Releases FSH & LH → Stimulates gonads → Secretion of sex hormones and gametogenesis.

  • Functional Anatomy of the Female Reproductive Tract:

    • Internal Genitalia: Ovaries, fallopian tubes, uterus, cervix, vagina.

    • External Genitalia: Labia, clitoris, vaginal opening.

Study Questions

  1. Sex Determination vs. Sex Differentiation:

    • Genotype (XX, XY) determines sex, whereas phenotype develops due to hormonal regulation and receptor activity.

  2. Chromosomal Notation (46,XY Male / 46,XX Female):

    • 46: Total chromosomes.

    • XY or XX: Sex chromosomes.

    • Male/Female: Phenotypic sex.

  3. Meiotic Divisions in Gametogenesis:

    • Meiosis I: Reductional division (46, double chromatid → 23, double chromatid).

    • Meiosis II: Equational division (23, double chromatid → 23, single chromatid).

  4. Polar Bodies in Ovaries but Not Testes:

    • Unequal cytokinesis in oogenesis conserves cytoplasm for the ovum.

  5. Enzymes for Estrogen and DHT Production:

    • Aromatase: Converts testosterone into estrogen.

    • 5-α-reductase: Converts testosterone into DHT.

  6. Gonadal Functions & HPG Axis:

    • Functions: Gametogenesis and hormone secretion.

    • HPG Axis:

      • Hypothalamus (GnRH) → Pituitary (FSH & LH) → Gonads (Steroid hormones & gametes).

Endocrine Physiology Mini-Lesson 2 Study Guide

Oogenesis & Ovarian Cycle

  • Oogenesis Steps:

    • Begins before birth.

    • Primary oocyte (46, double chromatid) → Meiosis I → Secondary oocyte (23, double chromatid) + first polar body.

    • Meiosis II occurs only if fertilization happens → Ovum (23, single chromatid) + second polar body.

  • Ovarian Cycle Phases:

    • Follicular Phase (Days 1-13): Follicle maturation, estrogen secretion.

    • Ovulatory Phase (Day 14): LH surge triggers ovulation.

    • Luteal Phase (Days 15-28): Corpus luteum secretes progesterone; degenerates if no fertilization.

  • Follicle Development:

    • Primordial → Primary → Preantral → Early Antral → Mature (Graafian) Follicle.

    • One dominant follicle selected (~day 7).

  • Hormonal Regulation:

    • Early & Middle Follicular: FSH stimulates granulosa cells; LH stimulates theca cells.

    • LH Surge & Ovulation: Estrogen positive feedback.

    • Luteal Phase: Corpus luteum secretes progesterone, inhibin, estrogen.

  • Corpus Luteum Function & Fate:

    • Secretes progesterone; degenerates into corpus albicans if no fertilization.

Study Questions

  1. Oogenesis Steps:

    • Oogonium → Primary Oocyte (46, double) → Secondary Oocyte (23, double) → Ovum (23, single, if fertilized).

  2. Ovarian Cycle Events:

    • Follicular (1-13): Follicle growth, estrogen.

    • Ovulatory (14): LH surge, ovulation.

    • Luteal (15-28): Progesterone dominance.

  3. Follicular Development Stages:

    • Differ in size, fluid content, and hormone secretion.

  4. Corpus Luteum Formation & Function:

    • Forms from ruptured follicle; secretes progesterone.

  5. Regulation of Estrogen & Inhibin in Follicular Phase:

    • FSH stimulates granulosa cells (estrogen production).

    • LH stimulates theca cells (androgen precursors for estrogen).

  6. Dominant Follicle Selection (~Day 7):

    • Increased FSH receptor expression → Continues growth despite FSH decline.

  7. LH Surge & Ovulation:

    • Estrogen feedback → LH peak → Ovulation.

  8. LH Surge Effects:

    • Oocyte maturation, follicular rupture, corpus luteum formation.

  9. Hormonal Control in Luteal Phase:

    • High progesterone inhibits FSH/LH → Corpus luteum degenerates if no hCG signal.

  10. Corpus Luteum Viability:

  • ~14 days unless fertilization occurs (hCG maintains it).

Endocrine Physiology Mini-Lesson 3 Study Guide

Uterine Changes & Pregnancy Hormones

  • Uterine Phases:

    • Menstrual (Days 1-5): Shedding.

    • Proliferative (Days 6-14): Estrogen stimulates endometrial growth.

    • Secretory (Days 15-28): Progesterone from corpus luteum maintains endometrium.

  • Estrogen & Progesterone Roles:

    • Endometrium: Growth (estrogen), maintenance (progesterone).

    • Myometrium: Contractions (estrogen), inhibition (progesterone).

    • Cervical Mucus: Thin (estrogen), thick (progesterone).

  • Other Steroid Effects:

    • Puberty: Breast growth, fat distribution (estrogen).

    • Adult: Libido (androgens), bone density (estrogen).

  • Fertilization & Implantation:

    • Occurs in fallopian tube ~24 hrs post-ovulation.

    • Implantation ~Day 6-7 in endometrium.

  • Human Chorionic Gonadotropin (hCG):

    • Secreted by embryo → Maintains corpus luteum → Sustains pregnancy.

Study Questions

  1. Uterine Changes During the Cycle:

    • Menstrual (shedding), proliferative (growth), secretory (maintenance).

  2. Roles of Estrogen & Progesterone:

    • Estrogen: Growth, contractions.

    • Progesterone: Maintenance, relaxation.

  3. Additional Effects of Sex Hormones:

    • Estrogen: Fat distribution, bone health.

    • Progesterone: Pregnancy maintenance.

    • Androgens: Libido.

  4. Fertilization & Implantation Timing:

    • Fertilization: Fallopian tube (~Day 14-15).

    • Implantation: Uterus (~Day 20-22).

  5. hCG Source & Function:

    • Secreted by trophoblast → Maintains corpus luteum → Supports pregnancy.