Anatomical and immunohistochemical considerations on the microinnervation of trachea in humans.

The anatomy of the tracheal microinnervation is understudied in humans; the purpose of our study was to fill this gap by working on human adult tracheas, to compare the results with those obtained from animal studies, and to checking whether or not these studies are suitable to be translated from comparative to the human anatomy. The study was designed as a qualitative one. The present work was performed on human adult tracheas dissected out in 15 human adult cadavers. Microdissections were performed in eight tracheas and revealed the outer peritracheal plexus, segmentally supplied and distributed to trachea and esophagus, with longitudinal intersegmentary anastomoses but also with bilateral interrecurrential anastomoses previously undescribed in anatomy. Seven different tracheas were transversally cut and paraffin embedded. Histological stains (HE, toluidine blue, luxol fast blue, Giemsa on tissues and trichrome Gieson) and immunohistochemistry using primary antibodies for nNOS, neurofilament, SMA and the cocktail of citokeratines CK AE1-AE3+8/18 were done. According to the histological individual variation, the neural layers of the posterior wall of the human trachea could be considered as it follows: (a) an outer neural layer, ganglionated, associated with the connective covering layers, adventitia and the posterior fibroelastic membrane (external elastic lamina); (b) a submucosal ganglionated neural layer, mainly with juxtaglandular microganglia that may expand, as glands do, through the outer covering layers; (c) intrinsic nerves of the transverse trachealis muscle; (d) the neural layer intrinsic to the longitudinal elastic band (internal elastic lamina) and supplied from the inner submucosa; (e) the neural plexus of the lamina propria, with scarcely distributed neurons. We also bring here the first evidences for the in vivo nNOS phenotype of mast cells that were identified, but not exclusively, within the trachealis muscle.

Transverse subisthmic course of the innominate artery in an adult: detailed anatomy and additional variation.

A rare morphology of an aberrant innominate artery (IA) is reported here, together with additional arterial variation encountered in the respective specimen. The IA originated in the aortic arch on the left side of the trachea, coursed on that side of the trachea to reach the left thyroid lobe, turned in at a right angle to pass anterior to the trachea and immediately inferior and parallel to the thyroid isthmus, and finally it divided inferior to the right thyroid lobe into the right subclavian and common carotid arteries. The right common carotid artery immediately turned at a right angle to ascend in the neck. Thus the terminal branches of the IA had origins in a higher position than is usually expected. This aberrant course of the IA determined a step-like morphology in the sagittal plane of the left common carotid artery. Additional variations were also encountered: (a) a lateralised right external carotid artery with the superior thyroid artery initially coursing over the internal carotid artery; (b) the right vertebral artery coursing over the inferior thyroid artery and entering the transverse process of the fifth cervical vertebra; (c) the left subclavian and vertebral arteries were tortuous. Knowledge of the presence of this IA variant, with a transverse subisthmic segment, appears to be important in various surgical approaches, such as tracheostomies, thyroidectomies, and mediastinoscopies; in addition, the variations of the IA and the vertebral arteries are relevant for lower cervical spine approaches. Nevertheless, the lateralised external carotid artery may lead, if unidentified, to hemorrhagic complications during carotid space approaches. It is important for surgeons to be aware that if an aberrant IA is identified it may not be the only variation in that patient.