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The Luteal Phase of the Estrous Cycle - Coggle Diagram
The Luteal Phase of the Estrous Cycle
The Luteal Phase (overall)
Consists of: corpora lutea formation, production of progesterone, and luteolysis
Lasts from the time of ovulation until regression (luteolysis) of the corpus luteum near the end of the estrus cycle
The dominant ovarian hormone during the luteal phase is progesterone
Includes metestrus and diestrus
Near the end of the luteal phase, luteolysis occurs and the CL (corpus luteum) loses its functional integrity and decreases in size
Luteolysis causes an irreversible structural degradation of the corpus luteum
A lysed corpus luteum will become a corpus albicans
The remanent of the corpus luteum appears as a white scar-like structure because of the connective tissue that remains after the glandular tissue disappears
Luteinization is the process whereby cells of the ovulatory follicle are transformed into luteal tissue
After ovulation the theca interna and the granulosal cells of the follicle undergo a dramatic transformation which is luteinization
Corpus Luteum
Functional (producing high levels of progesterone) or nonfunctional (regressing or producing low levels of progesterone)
Real-time ultrasonography has proven effective
Use this technique on cows and mares to determine ovarian status
Originates from the ovulatory follicle
The "vigor" of the corpus luteum probably depends on the number of luteal cells and the degree to which the CL becomes vascularized
Luteal Tissue
Consists of large and small luteal cells
Large cells originate from the granulosal cells
Small cells originate from the cells of the theca interna
Both small and large luteal cells are steroidogenic (possessing the ability to produce steroids), or in this case progesterone
Progesterone Synthesis
Due to the functional capability of the newly developed corpus luteum
Poor progesterone synthesis and secretion is believed to be an important contributor to reproductive failure
Major importance in the endocrine control of reproduction because it exerts a strong negative feedback on the hypothalamus
Elevated progesterone reduces the frequency of the basal episodic secretion of GnRH by the tonic GnRH center
Luteolysis