Trachea and the mode of branching of bronchial tree

INTRODUCTION: The trachea provides a passageway for inhaled gas to reach the gasexchange regions of the lungs from the atmosphere. Its characteristic anatomy provides the surgeon with many challenges. Knowledge of anatomy is essential to the study of airway management. The rigidity of trachea is provided by cartilaginous rings that extend approximately two-thirds the circumference. Both benign and malignant processes affect trachea necessitating treatment. The initial evaluation of patients with suspected tracheal pathology includes a thorough history and physical examination, standard chest x-ray and neck x-ray, CT scan can determine local extension, degree of luminal compromise and the length of the trachea that is involved. Bronchoscopy is required in the evaluation and treatment of tracheal pathology. Tracheostomy should be considered in the presence of severe maxillofacial injury to ensure an adequate airway. The golden rule of tracheostomy based entirely on anatomical considerations- “is stick exactly in the midline”. In the present work, the effort will be to provide an account of the structure of the lungs, with particular attention to its application in thoracic surgery. More and more, rational dissection has come to replace the unnecessarily destructive method of mass ligature at the hilum. The availability of effective chemotherapy, especially for tuberculosis, has made the benefits of segmental resection available to an ever increasing number of patients. Peripheral lesions can be removed by “wedge” resection, but there has renamed a definite need for more direct attack on lesions confined to a single segment deep within a lobe, where conservation of tissue is of paramount importance. Here an account of knowledge of bronchial and vascular relationships is essential, if these operations are to be done with maximum safety. AIM OF THE STUDY: 1. To study the anatomical variations in length, diameter and number of tracheal rings. 2. To study the anatomical variations in length, angle and the divisions of primary bronchus. 3. To study the anatomical variations of bronchial tree in right and left lungs. MATERIALS AND METHODS: The 50 pairs of specimens for this present study were obtained from the embalmed cadavers of Anatomy Department and also from the postmortemed bodies in the Department of Forensic Medicine, Thanjavur Medical College during the period of study. The specimens were collected without any age, sex, socio-economic status, religion or pathological bias. The specimen was removed from the cadaver as per the Cunningham’s manual of practical anatomy. An incision is made in the skin from chin to sternum in the midline and the flap of skin is reflected inferolaterally. A transverse incision is made through the deep fascia immediately above the sternum and the deep fascia is reflected. The infrahyoid muscles are separated to expose the pretracheal fascia. Below the isthmus of the thyroid gland trachea is exposed after removing the pretracheal fascia. A transverse cut is made below the cricoid cartilage and the trachea is separated from the adjacent structures. CONCLUSION: In the present study the tracheo bronchial tree was studied and the results were compared with earlier studies. The summary of the present study in human, in 50 pairs of specimens of both lungs is as follows. The diameter of trachea was within normal limits in about 94%. The length of trachea was within normal limits in about 76%. The number of tracheal rings was within normal limits in about 90%. The length of the right primary bronchus was within normal limits in about 90%. The angle of the right primary bronchus was within normal limits in about 90%. The length of the left primary bronchus was within normal limits in about 94%. The angle of the left primary bronchus was within normal limits in about 72%. In the right lung both eparterial and hyparterial bronchus were present. In the left lung only the hyparterial bronchus was present in all specimens. In the right upper lobe bifurcation occurred in 66%, trifurcation in 34%. In the right middle lobe length of the middle lobe bronchus was within normal limits in 86%. In the right middle lobe bifurcation occurred in 94%, trifurcation in 6%. In the right lower lobe superior segment orifice was at same level or overlapping in 30% and at separate levels in 70%. In the right lower lobe the branching pattern of superior segment was bifurcation in 90% and trifurcation in 10%. In the right lower lobe the subsuperior bronchus was present in 92%. In the right lower lobe the branching pattern of basal trunk was bifurcation in 84% and trifurcation in 16% of the specimens. In the left upper lobe branching pattern was bifurcation in 88%, trifurcation in 12%. In the left lower lobe superior segment bronchus bifurcated in 90%, trifurcated in 10%. In the left lower lobe subsuperior bronchus was present in all lungs. In the left lower lobe the branching pattern of basal trunk was bifurcation in 78%, trifurcation in 22%. Unfortunately the lung is not simply built. An understanding of its structure can be achieved only by effort. In planning operative procedures that will serve to remove disease, while preserving useful tissue, this effort will be well expended. An attempt at application of the anatomical data is very useful to the planning of the surgical approach. Pulmonary functions show exactly how essential is the amount of pulmonary tissue for good and efficient functioning of lungs. Therefore the segmental resection can be performed in eligible cases saving valuable lung tissue. To undertake this, detailed anatomy of the segmentation of lungs then becomes inevitable. This study is presented to shed more light on normal anatomy of trachea and the branching pattern of bronchi