Estrous Cycle/ Final Maturation and Ovulation Flashcards
What are the targets/ actions of estrogen?
-vagina: mucosa increases in thickness (copulation)
-cervix/cranial vagina: produces mucous for lubrication, flush out foreign material following copulation, and sperm transport
-uterus: development of uterine glands
-oviduct: increases secretory rate, cilia increase beat frequency
What are the additional actions of estrogen?
-increased blood flow(hyperemia) to all of repro tract
-facilitates of leukocytes to submucosa
-edema of external genitailia
-delivery pf hormones and metabolites
-increased tone and motility of musculatris in all regions of the tract
-hypothalamus: GnRH surge leading to LH surge= ovulation
What is a deterministic model?
increased GnRH secretion is required to induce the preovulatory LH surge and thus ovulation
-increased GnRH secretion is needed to drive the LH surge
What is a permissive model?
GnRH secretion need not increase. Rather the preovulatory LH surge results from enhanced sensitivity of the pituitary gland to GnRH.
-no surge of GnRH
What are the two type of ovulators and what species?
- induced(reflex): rabbit, cat, ferret, and mink
intromission stimulates the surge of LH ovulation (greater window of reception), ovulation occurs through the neuroendocrine reflex/ will not ovulate unless copulation occurs - Spontaneous: farm animals and humans, controlled by events of estrous or menstrual cycle
How does ovulation occur?
occurs due to endogenous and neuroendocrine factors
-copulation or presence of male is not necessary for ovulation to occur
describe the process of ovulation
- hyperemia at the ovary (7 fold increase in blood flow)
- theca interna becomes swollen, resulting in hydrostatic pressure
- Theca interna begins to produce progesterone instead of androsteindione
- progesterone stimulates synthesis of collagenase (breaks down collagen in the follicle/weakens follicular wall)
Process of ovulation part 2
- follicular fluid volume increases
- basement membrane partially disintegrates
- stigma of follicle begins to push out ward and weaken
the stigma is the site of the follicle rupture
What hormone/molecule is produced by the ovary during ovulation?
PGF2a synthesized and secreted by the ovary
-causes lysosomes in granulosa to rupture
-contractions of smooth muscle of ovary
PGFE2 synthessized and secreted by the ovary
-activates plasminogen( converted to plasmin)
-together they assist with remodeling follicle into corpus luteum
How is the CL formed?
luteinization: transformation of follicular cells into luteal tissue
-after ovulation: walls of follicle collapse forming fold (allowing mixing of cells)
–Granulosa become large luteal cells
—theca become small luteal cells
What are the characteristics of large luteal cells
20-70 micrometers
-majority of progesterone synthesis/secretion
-rarely multiply after ovulation
-increase in volume (hypertrophy)
-contains LH receptors, but binding of LH to its receptor does not increase progesterone production from these cells
What are the characteristics of small luteal cells
less than 20 micro meters
-produce progesterone
-increase in number (hyperplasia)
-have LH receptors and respond to LH by increasing progesterone production
Which center of the brain responds to high concentrations of estrogen?
the surge center
When does GnRH pulse frequency begin and why?
early in the follicular phase, GnRH pulse frequency begins to increase because of low progesterone, thus causing FSH and LH to be secreted form the anterior lobe
-GnRH secretion from the surge center is controlled by high estrogen and low progesterone
Describe the 4 stages of follicular growth and the hormone levels
- recruitment: High FSH + Low LH pulse frequency + low inhibin + low estrogen
- selection: low FSH + moderate LH+ low inhibin
- dominance: low FSH + high LH pulse frequency + high inhibin
- atresia: degeneration of follicles
