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Menstrual Cycle - Coggle Diagram
Menstrual Cycle
Hormones
GnRH
GnRH is secreted in pulses
As intervals decrease the GnRH favours the luteal phase
Constant release will suppress gonadotropin hormones
Steroid hormones
Estrogen and progesterone decreases GnRH release
FSH and LH decreases GnRH release
GnRH decreases its own release
Neutrotransmitters
Dopamine, acetylcholine, noradrenaline, serotonin, inhibin
FSH
Components
Composed of alpha and beta subunits
Actions
Stimulates growth of ovarian follicles
Stimulates aromatase activity and production of estrogen
Stimulates formation of LH receptors
Leads to ovulation with LH
Levels
Begins to increase at end of previous menstrual cycle
Decline in FSH levels at mid-follicular phase via negative feedback (estrogen and inhibin)
Small increase in progesterone concentrations generates FSH level surge, and occurs with LH surge
LH
Structure
Water soluble containing alpha and beta subunits
Action
Induces androgen production
Sitmulates proliferation, differentiation and secretory activity
Leads to oocytes to complete first meiotic division, rupture of mature follicle/ovulation, luteinization of theca and granuolsa cells
Receptors
On surface of theca cells
Level
: Peaks on day 13 of 28 menstural cyucle
Inhibin
Characteristics
Peptide hormone secreted by granulosa cells
FSH stimulates production of inhibit by grnaulosa cells, and works with estradiol to inhibit FSH release
All inhibin levels decline with loss of luteal functiona nd remain low
Estradiol
Characteristics
Sex steroid hormone derived from cholesterol and produced by granulosa cells
In menstrual cycle
Drop at ovulation, rise during luteal phase, and drop to menstrual levels at lureal phase unless there ia pregnancy
Physiological Effects
Rise in estrogen levels -> Growth spurt, maturation of internal and external genitalia
acts AS trophic hormones for tissues of reproductive tract
LH surge
Thickens endometrium during follciular phase
Progesterone
Characteristics
Sex steroid derived from cholesterol
Produced by ovaries and placenta, store in adipose tissue
In menstrual cycle
Low during preovulatory phase, rise after ovulation, and are elevated in luteal phase
In pregnancy, hCG is released to maintain corpus luteum to maintian lvevels of progesterone
Physiological Effects
Converts endometrium to its secretory phase
Antagonized mitotic effect of estrogen
Makes vaginal epitheliuma nd mucus thick and impenetrable to sperm
Decreases maternal immune response
Decreases contractiltiy of uterine smooth muscle
Inhibits lactation during pregnancy
Androstenedione
Sex steroid derived from cholesterol, produced by testicles, adrenals and ovarain cortex
Precursor for production of estrone
Released by ovarain theca cells, and is used as a precursor for production of estradol
Physiological Effects
Promotes protein synthesisi
Effects are anabolic and virilizing (testeosterone)
Cause enlargemenmt fo sebacious glands and acne, increased libido, pubic hair and axillary hair growth
Key Facts
Ovarian and Endometrial cycles combine to form the menstrual cycle
Controlled by hypothalamus, pituitaryt ovarian axis
Ovarian Cycle: Refers to changes that occur in the ovary each month during menstrual cycle
Endometrial cycle: Cyclic growth and shedding of endometrium each month in respnse to estrogen and progesterone
Important hormones
GnRH, FSH, LH, Estrogen, progesterone
GnRH -> Stimulates LH and FSH -> Stimulates Estrogen adn progesterone -> Stimulate growth and maturation of ovarian follicles and preparation of endometrial lining
Glands
Hypothalamus
Importatn for reproduction
Contains nuclei with medial preoptic (GnRH), Arcuate (GnRH, GHRH, dopamine)
Pituitary Gland
Leader of endocrine system
Anterior pituitary gland: mostly cellular, very vascular, secretes FSH,LH,PRL, GH, TSH, ACTH, controls ovaraian function
Posterior: Secretes vaspressin and oxytocin
Menstrual Cycle
Oogenesis
Ovarian differentiation begins at 6-8 weeks gestation
Follicles
Follicular growth
85 days for rimary follcile to progress to point of ovulation
Independent of gonadotropins to produce cohort of follicles that will develop in response to FSH stimulation
Number of mature follicles that matrue is dependent on amont of FSH and sensitivty to gonadotropins
Ovarian Cycle
If implantation occurs, luteum produces hormones to maintain pregnancy
Corpus luteum makes hormones to regulate endometrial cycle
Follicular Phase
Goal: Develop viable follicle
Early events initiation: Decrease in estrogen/progesterone at end of previous cycle, increase in FSH levels
Follicle Stages
Priamry follicle: Growth and differentation of primordial follicle -> primary follicle
Gonadotropin independent, stimulus unknown, major time of oocyte growth
Antral Follicle
Gonadotropin dependent
Granulosa cells proliferate and a fluid filled cavity called antrum develops
Single follicle destined to become domiannt grows at faster rate (tertiary follicle)
Deficiency in FSH and FSH receptors in other follicle inhibits estradiol production (accumulation of androstenediones -> atresia of follicles)
Graafin Follicle
Final stage of focllucular developemnt
Granulosa cells divided into 2 groups
Mural granulosa cells: Thin layer along periphery of follicle
Cumulus Oophorus: surrounds oocyte; inner most cells called corona radiata
Oocyte undergoes cytoplastmic and nuclear maturation to prepare oocytesfor embyogeneiss
Ovulatory Phase
Prior to ovulation: Estrogen increases rapidly, generates LH surge to complete meiosis 1 in oocytes
Ovulation Mechanism
Pressure thinning of tissue on the surface opf the follicle by rapid increase in antral fluid
Pg stimulate contraction of myofibrils
LH surge triggers activation of proteolytic enzymes (plasmin and collagenase)
At time of Ovulation
Follicle rupture to release oocyte, granulosa and theca cells remain in ovary
Luteal Phase
Corpus luteum forms under effect of LH
Granulosa and tehca cells proliferate and undergo hyperthrophy to form granulosa-lutein cells
Cl produces high levels of progesterone, and moderate levels of estradiol and inhiibin
Wihtout pregnancy, corpus luteum regresses
Endometrial Cycle
About Endometrium
Innermost glandular layer which is a lining of uterus
During menstrual cycle, endometrium grows thick, blood vessel rich layer
2 Layers
Basal Layer
Not shed and responisble for development of functional layer
Function layer
Stratum compaftum: Supreficial of gland necks and dense stroma
Stratum spongiosum: Glands and large amounts of loosely organized stroma nad interstitial tisue
Proliferates in response to estrogen, rebuilds after menstruation
Menstural Phase
Dayu 1-4 of a menstrual cycle
Periodic desquamation of endometrium
Leukocytes/Cytokines invovled in inflammatiory reaction
Plasmin and matrix: tissue breatdown
PG; Constric spiral arterioles leading to ischemia and desquamation
Proliferative Phase
Day 4-14 of mentsural cycle
Glandular and stromal cells of functional layer proliferate rapidly
Glands become more tortuous and cells lining glandular lumen undergo pseudostratification
Tubular glands with columnar cells and dense stroma proliferate
Secretory Phase
Day 15-28 of cycle
Begins at ovulationa and correlates with ovarina luteal phhase
Glands are coiled, more edematous
Secretions rich in glycogen and glycoprotein
If pregnancy does not occur, corpus luteum rdegenerates and lack of progesteon causes spiral arteries to constrict and endometrial tissue to become ischemic