MORPHOLOGY AND BIOMETRY OF THE THYMUS IN Gallus gallus domesticus (Linnaeus, 1758) FROM THE ISA BROW LINEAGE

Abstract

The anatomy of the thymus was described in thirty chickens (Gallus gallus domesticus) of the Isa Brow line. Samples were prepared by fixation and preservation in 10% formalin solution and analyzed by subsequent dissection. The thymus lobes were found along the ventral region of the neck from the third cervical vertebra to the proximity to the clavicular bones in relation to the vagus nerve, the common artery of the vagus nerve and the jugular vein. The number of lobes ranged from four or five to the right antimere and three to five to the left. The mean lobe size was 0.80 x 0.43 x 0.38 cm for the cranial lobe, 1.53 x 0.81 x 0.42 cm for the middle cranial lobe, 2.10 x 0.64 x 0.46 for the middle lobe, 2.29 x 0.89 x 0.59 for the middle caudal lobe and 3.82 x 1.39 x 1.11 cm for the caudal lobe in the right antimere. In the left antimere, 0.80 x 0.41 x 0.37 cm was recorded for the cranial lobe, 1.55 x 0.80 x 0.44 cm for the middle cranial lobe, 2.37 x 0.87 x 0.56 for the middle lobe, 2.37 x 0.85 x 0.60 for the middle caudal lobe and 3.89 x 1.43 x 1.08 cm for the caudal lobe. The thymus of birds from the Isa Brow lineage presented characteristics similar to those found in other lineages with respect to the division of lobes and topography. However, skeletal, syntopic and holotopic disparities were observed that indicate some unique characteristics of the thymus in this lineage.