After the formation of the corpus luteum, it develops rapidly. If not pregnant, the corpus luteum gradually degenerates, and this type of corpus luteum is called the periodic corpus luteum. If pregnant, the corpus luteum will continue to maintain its size and secretion function throughout the pregnancy, which is called the pregnancy corpus luteum. There are significant differences between the corpus luteum of the cycle and the corpus luteum of pregnancy when observed by imported cattle using ultrasound.

The formation and development of the corpus luteum in cows can be observed by imported cows using ultrasound. The formation of the corpus luteum begins after ovulation, with the formation of a red body first, and on the third day, the red body turns into a new corpus luteum. The corpus luteum further develops, and through animal B-ultrasound observation, the corpus luteum volume reaches its maximum from day ll to day 15. Then it stops developing and gradually regresses, becoming noticeably degraded by day 16.

After ovulation, imported cattle can be observed by B-ultrasound, and the follicular wall collapses to form folds (folds already appear in mature follicular walls in pigs and cattle before ovulation). The blood vessels of the follicular membrane are damaged and bleed, filling the follicular cavity with blood and some serous fibrous fluid, called the red body.

As the basement membrane disintegrates, blood vessels in the follicular endometrium proliferate and extend into the granulosa layer, gradually absorbing blood. Under the action of LH secretion from the anterior pituitary gland, granulosa cells enlarge and become polygonal, with lipid granules appearing in the cytoplasm, forming granulosa corpus luteum cells; The follicular endometrial cells also undergo similar changes, forming membrane-bound corpus luteum cells with smaller volume and darker nuclear and cytoplasmic staining. At this time, the red body composed of blood clots transforms into corpus luteum.

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