The ovarian morphology of the sexually mature rhea (Rhea Americana) is described. Ovaries from 24 adult rheas in their reproductive age were collected in the slaughterhouse. Follicular diameters (n = 18) were measured and samples (n = 6) were fixed in 10% formaldehyde with 0.1M phosphate buffer at pH 7.4 for light microscopy. Results showed that the left ovary occupied the dorsal portion of the celomatic cavity in contact with the cranial portion of the left kidney and the suprarenal gland, being supported in the cavity through the mesovary. On the free surface of the ovary 72.4±17.09 follicles in different phases of development and 30.4±3.65 atretic follicles were observed. The follicles were linked to the ovarian surface by the follicular stalk and had a wide band surrounding its surface, the Stigma folliculare. Histologically, the ovary is constituted by a medulla, composed by connective tissue and vessels, and by a cortex with oocytes and follicles. The follicular wall is composed by the Theca externa and Theca interna, Stratum granulosum and the Zona radiata. The ovary surface is covered by a cubic epithelium, the germinal epithelium, on the connective tissue of the Tunica albuginea. The morphologic characteristics of the ovary of the rhea are due to the egg size in this species and generally similar to other birds.
Ovary; follicle; morphology; avian anatomy; rhea; Rhea americana