Morphology of the Oligoryzomys nigripes respiratory system

Macroscopic and histological aspects of the pharynx and larynx of the giant anteater (Myrmecophaga tridactyla Linnaeus, 1758)

Giant anteater (Myrmecophaga tridactyla) is an endangered species that resides in much of Latin America, but it has been losing its habitat, especially in the Cerrado biome, where it constantly suffers traumas resulting from fires and roadkill. The anatomical knowledge of structures of the respiratory system is important for a better morphophysiological understanding of the species. Thus, this study aimed to perform the macroscopic and histomorphological description of the pharynx and larynx of the giant anteater. Twelve adult giant anteaters were used, three of them fixed in buffered formalin for further dissection and pharynx and larynx macroscopic analysis of structures. From the other animals, samples of the pharynx and larynx were collected and prepared for histological evaluation under optical microscope. Macroscopically, their pharynx and soft palate are extensive, and the anatomical location of these structures and the larynx differs greatly from that described in other species. The larynx, although more caudal, was similar to that of other animals. Histologically, the epithelium of these regions varied between the pseudostratified ciliated columnar and the non-keratinized stratified squamous epithelium. Laryngeal cartilages were composed of elastic (epiglotti) and hyaline cartilages (arytenoid, cricoid and thyroid cartilage), with an ossification process and glandular clusters around the hyaline cartilage. The distinct anatomical location of the pharynx and larynx of Myrmecophaga tridactyla is the main macroscopic finding of this study, besides the length of the pharynx and soft palate of these animals.

Histomorphology of the lower respiratory tract in the Indian crested porcupine (Hystrix indica)

The Indian crested porcupine (Hystrix indica) (ICP) is widely distributed in Asia; however, compared with other rodents, little is known about the structures of its respiratory system. The aim of this study was to evaluate the histomorphology of the lower respiratory portion of the ICP to provide a basis for the identification of the normal structure of this organ. The larynx, trachea and lungs of four carcasses of adult Indian crested porcupines (two males and two females) were dissected and fixed in 10% neutral-buffered formalin. The gross anatomy and histology of all specimens were evaluated. A macroscopic evaluation showed unique structures in the ICP respiratory system, including the presence of a chamber-like structure at the origin of the bronchi and a difference in epiglottis shape between males and females. Histologically, the stratified squamous epithelium covered the epiglottis and arytenoid cartilage, and the pseudostratified ciliated columnar epithelium covered the internal part of the thyroid and cricoid cartilages. Histomorphological studies showed a few goblet cells in the tracheal epithelium. In the bronchi and larger bronchioles, pseudostratified ciliated columnar epithelia were observed. Bronchi were surrounded by segments of cartilage. Distal bronchioles had a simple cuboidal/columnar epithelium with club (Clara) cells, lacked cartilaginous tissue in their walls and had a complete smooth muscle layer. These results revealed histomorphological differences between the ICP and other rodents.