Corpus Luteum - Anatomy & Physiology

The Corpus Luteum

When the dominant antral follicle ovulates, slight localised haemorrhage occurs at the site of ovulation and fills the former cavity.
The small amount of bloody tissue can be observed by the naked eye.
Loss of fluid from the antral cavity causes the follicle to collapse into many folds.
As a result, some granulosal and thecal layers are pushed into the apex of the ruptured follicle.
This protrusion of tissue and ruptured blood vessels forms a structure known as the Corpus Haemorrhagicum.
Following this, the theca interna and granulosa cells differentiate into large and small luteal cells.
- Luteal cells contain increased quantities of lipid droplets and the pigment 'lutein'.
As the blood is resorbed, a solid Corpus Luteum is formed by proliferation of granulosa and theca intera cells as well as blood vessels. This remains on the surface of the ovary.
In the non-pregnant animal, corpora lutea are transient structures.
Cyclic corpora lutea undergo proliferation and vascularisation directly after ovulation.
The corpora lutea then regress and degenerate into a connective tissue scar, the Corpus Albicans.
If the ovum is fertilised, the corpus luteum remains fully developed and active throughout at least part of the pregnancy.
Corpora lutea produce progesterone.
Progesterone prepares and maintains the uterus for implantation of the fertilised ovum.
The number of corpora lutea formed are directly related to the number of oocytes released.

Progesterone Biosynthesis- Copyright L.Wilkie 2008

In most species, luteinization and progesterone synthesis is regulated principally by luteinising hormone (LH) in the non-fertile cycle.
Further conversion to oestradiol is prevented.