title: Relationship between the morphology of and progesterone production by the corpus luteum of the mare.
abstract: The histology of the growing, secreting and regressing CL of thirty-five cycling and early pregnant mares with known breeding histories was studied by light microscopy. Thecal cells are best developed a few days before ovulation. They regress very quickly and within 24 hr after ovulation all remaining thecal cells are in an advanced stage of degeneration. Hypertrophy and luteinization of the granulosa cells commences 10 hr after ovulation and maximum size (37-5 mum) is reached later. The luteal tissue enlarges mainly through hypertrophy of the lutein cells. Two types of lutein cells are found in the CL, a large light-staining cell and a small dark-staining cell. Degeneration of the lutein cells in the non-pregnant mare commences on Day 12 after ovulation and in the pregnant mare on Day 38 after ovulation. The primary CL of pregnancy regresses after the secondary CL are formed. The progesterone concentration in the peripheral plasma is closely correlated with the morphological changes in the CL.
mesh_terms: D000818:Animals; D003338:Corpus Luteum / Q000033:anatomy & histology / Q000378:metabolism; D005260:Female; D006107:Granulosa Cells / Q000378:metabolism; D006736:Horses / Q000502:physiology*; D011247:Pregnancy; D011374:Progesterone / Q000096:biosynthesis*; D013799:Theca Cells / Q000378:metabolism; D013997:Time Factors
chemical_list: D011374:Progesterone