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Reproductive Cyclicity: Follicular Phase - Coggle Diagram
Reproductive Cyclicity: Follicular Phase
Elevated gonadotropin secretion from anterior lobe of the pituitary
Controlled by ovarian estrogen and hypothalamic GnRH
GnRH responsible for stimulating released of FSH and LH
Tonic and surge centers control GnRH
Tonic = spontaneous but influenced by progesterone
Small amplitudes of GnRH
FSH and LH secretion
Growth and development of ovarian follicle
Decreased FSH = estradiol + inhibin
Increased LH = GnRH pulse frequency
Surge = controlled by high estradiol with low progesterone
Positive feedback = response to rising estradiol
Secretes large amount of GnRH
LH surge
Ovulation
Negative feedback = estradiol low and progesterone high
Reduces frequency of GnRH pulses
Surge center responds to high estradiol
Follicular growth and preparation for ovulation
AKA follicular dynamics
Cyclic recruitment
Starts after puberty and is result of elevated FSH that occur in each cycle
Initial recruitment phase
Continuous recruitment of primordial follicles into a growing follicle pool that terminates with atresia
Occurs continuously throughout estrous cycle
Antral follicles
Always present
Develop in response to basal levels of FSH and LH
Selection
Low FSH + moderate LH + low inhibin
Dominance
Exerting inhibitory effect on other antral follicles
Production of inhibin and estradiol
Low FSH + high LH pulse frequency + high inhibin
Species Differentiation
Monotocous
Single follicle selected and develops dominance
Polytocous
Multiple dominant follicles
Recruitment/emergence
Cohort begins to grow and secrete estradiol
High FSH + low LH pulse frequency + low inhibin + low estradiol
Atresia
Degeneration
Occurs throughout folliculogenesis
Suppressed FSH and reduced blood supply
LH dependent
Mature selected, dominant, and preovulatory follicles
FSH dependent
Recruited and selected follicles
Sexual receptivity (estrus)
Effects of estradiol on repro tract
Leukocytosis
Phagocytize foreign material
Initiation of uterine gland growth
Increased blood flow/hyperemia
Leukocytosis
Genital swelling
Elevated myometrial tone
Sperm transport
Change in tissue electrical conductivity
Electrical resistance in vulva decreases
Increased mucosal secretion
Flush foreign material out after copulation
Privileged pathways for spermatozoa to enter uterus
Lubricate vagina and cervix for copulation
Genital swelling
Increased capillary pressure and lymph buildup
Elevated estradiol + low progesterone = behavioral changes
Ovulation
Started by LH surge
Increases PGF2a
Increase contraction of ovarian smooth muscle
Increase follicular pressure
Ovulation
Release lysosomal enzymes
Follicle wall weakens
E2 to P4 by dominant follicle
Increase P4
Increase collagenase
Increase PGE2
Increase blood flow to ovary and dominant follicle
Hyperemia
Edema
Surface epithelium
Plasminogen activator
Tunica albuginea
Plasmin
Capillary venules
Tumor necrosis factor a
Kills granulosa cells
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Histamine
Gap junction breakdown between granulosal cells and oocyte
Removal of meiotic inhibition
First polar body
Haploid oocyte
Fertilization
Breakdown of CT
Ovarian contractions
Elevated blood flow
Spontaneous ovulators
Regular frequency
Doesn't require copulation
Responds to hormonal changes
Cow, sow, ewe, mare, woman
Reflex/induced ovulators
Requires stimulation of vagina/cervix
Rabbit, felids, ferret, mink
Copulation stimulates sensory nerves in the vagina and cervix
Impulses relayed to spinal cord
Impulses relayed to surge center in hypothalamus
Hormonal induced ovulation
Requires premature luteolysis
Caused by PGF2a
GnRH release
FSH and LH release
Superovulation
High number of follicles selected followed by ovulation
Requires exogenous gonadotropins
Provide high FSH
Luteolysis
Driving force for initiation of follicular phase
CL becomes nonfunctional
Reduction in progesterone secretion
Negative feedback removed and GnRH released
FSH and LH released
Promotes final follicular development and estradiol secretion
Proestrus + estrus
Oocyte maturation
Nuclear arrest (dictyotene)
Cytoplasmic growth
Mitotic division of primordial germ cells
Resumption of meiosis
Zona pellucida
Mediated by granulosa cells of follicle