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Ch 8 - The Follicular Phase, Estradiol - Coggle Diagram

- - - - Ovulate with a regular frequency and do not require copulation
      - Ovulation is brought about totally in response to hormonal changes
    - - Require stimulation of the vagina and/or cervix for ovulation to occur
      - Most have a long copulation time or copulate with intense frequency to ensure adequate neural stimulation will take place and cause ovulation
      - The tactile stimulation is converted to action potentils that innervate the hypothalamus to cause a preovulatory surge of GnRH
        
        This causes LH to be released prompting the cascade of events leading to ovulation
      - Camelids are a modified version of this - presence of seminal plasma in reproductive tract is more important than tactile stimulation in inducing ovulation
- - - - PGE2
        
        Secretes plasminogen which is converted to plasmin by an activator
        
        Helps the follicle remodel itself into a corpus luteum after ovulation by directing the organization of the tissue structure
        
        Plasmin is the active enzyme that helps deissolve the coagulum of the corpus hemorrhagicum and aids in remodeling the follicle into a corpus luteum
      - PGF2a
        
        Lysosomal enzymes cause further connective tissue deterioration at the apex of the follicle
        
        Causes contractions of the myoid (smooth muscle) components of the ovary
        
        Causes lysosomes within granulosa cells to rupture, releasing their enzymes
        
        Intermittent contractions will increase local rpessure to force the stigma to protrude even more dramatically from the surface of the ovary
- - - - Selection
        
        A group of growing follicles that have not undergone atresia
        
        Multiple in dogs and cats
        
        One in horse and cow
        
        Low FSH, moderate LH and low inhibin
      - Dominance
        
        Produce increasing amounts of estradiol and inhibin
        
        Inhibin is a protein hormone secreted by antral follicles that inhibits release of FSH from anterior pituitary
        
        ONly follicles receiving a large blood supply grow and ovulate
        
        Low FSH, high LH pulse frequency and high inhibin
      - Recruitment (emergence)
        
        Phase of follicular development in which a cohort (group) of small antral follicles begins to grow (emerge) to secrete estradiol
        
        Most recruited follicles undergo atresia
        
        High FSH and low LH pulse frequency, low inhibin and low estradiol
      - Atresia
        
        Degeneration of follicles
        
        Occurs continuously throughout folliculogenesis
    - - Estradiol and inhibin secreted by growing follicles decreases FSH
      - GnRH pulse frequency increases LH
- - - - GnRH secretion appears to be spontaneous but is influenced by progesterone
    - - Secretes basal levels of GnRH until it receives appropriate positive stimulus
      - Consists of 3 nuclei
        
        Preoptic nucleus
        
        Suprachiasmatic nucleus
        
        Anterior hypothalamic area
      - Surge center responds dramatically to high blood concentrations of estradiol and low concentrations of progesterone
    - - Surge = once per cycle
      - Tonic = consistent
    - - Anterior Lobe of the Pituitary
        
        Stimulates secretion of FSH and LH
        
        Causes growth and development of ovarian follicles