The minor fissure is similarly completed. Medial traction of the bronchus clamp and dissection of the interlobar artery under direct vision lead to the middle trunk of the superior pulmonary vein and its posterior and inferior branches.
The common stem of the posterior and inferior veins is identified. The site of insertion of the middle lobe vein into the superior PV is preserved. The venous stem is divided with a stapling device.
After the specimen is removed, the pleural cavity is irrigated, and the bronchial closure is tested. The inferior pulmonary ligament is divided, allowing rotation of the lower lobe to facilitate the complete fill of the pleural space 2 - 5. The inferior pulmonary ligament is mobilised. The right middle lobe lies against the anterior chest wall. The mediastinal pleura is incised to identify and ligate the right middle lobe vein, usually a branch of the right superior PV.
The fissure between the upper and middle lobe is typically incomplete. After the exposition of anterior mediastinum and anterior surface of the upper and middle lobes, the venous drainage of these two lobes is recognised. The fissure line is developed as described previously. The development of the fissure between the upper and lower lobes reveals the lymph nodes in the area and the mean pulmonary artery. The right middle lobe PA arises from the intermediate artery near the superior segmental artery of the lower lobe.
The right middle lobe PA is defined and stapled. The surgeon should avoid the posterior recurrent ascending branch to the upper lobe or the superior segmental branch to the lower lobe.
All these vessels come off very close to one another. Finally, the right middle lobe bronchus is closed with a stapling device. Care must be taken to avoid injury to the superior segmental bronchus which comes out very close to the right middle lobe orifice. After the specimen is removed, the pleural cavity is irrigated, and the bronchial closure is tested 2 , 3 , 6.
The oblique fissure is opened retracting the right upper and middle lobes anteriorly and the lower lobe posteriorly. The interlobar PA is deeply situated in the region where the oblique and horizontal fissures meet. The visceral pleura overlying the interlobar artery is opened. The PA is dissected. The middle lobe artery, originating from the anteromedial surface of the interlobar artery, must be demonstrated.
The superior segmental artery lies posterolaterally. Rarely, the posterior ascending artery to the upper lobe arises from the superior segmental artery. Occasionally, the basal arteries may have a short common trunk from which two branches arise: one for the anterior and medial segments, the other the posterior and lateral segments.
Attention is then directed to securing the superior segmental artery, taking care to preserve the posterior segmental artery to the right upper lobe. The lobe is retracted anteriorly and superiorly. The inferior pulmonary ligament is divided up to the lower border of the inferior PV. The posterior mediastinal pleura is incised over the posterior surface of the inferior PV, which is cleared of tissue, and the pleural incision is carried superiorly to the bronchus intermedius.
The interval between the lower border of the bronchus and the superior PV is dissected. The anterior surface of the inferior PV is then cleared. With a finger serving as a guide, the inferior PV is then isolated and closed by a vascular stapler. The lower lobe bronchus is then dissected. Since the middle lobe bronchus and the superior segmental bronchus derive from the intermediate bronchus, it may be necessary to divide the basal segmental bronchus and the superior segmental bronchus separately to avoid the obstruction of the middle lobe bronchus.
Usually, an oblique application of the stapling device does not occlude the middle lobe bronchus. On the contrary, the lower lobe bronchus may be sutured as previously described. After the specimen is removed, the pleural cavity is irrigated, and the bronchial closure is tested 1 , 3 , 4.
The alveoli expand and contract 15, times a day. During activity, the rate of respiration doubles — and in extreme activities triples — and the amount of air reaching the alveoli increases three to five times. Stress can also result in deeper and faster respiration.
Indoor air pollutants can have two to five times more pollutants than outdoor air. First, it raises the temperature of cool air to body temperature, or it cools hot air to body temperature. Second, it moisturizes the air to percent humidity to prevent dehydration of alveolar membranes.
Last, it cleans the air. Foreign and possibly harmful substances are filtered from in-flowing air and removed by several means, including nasal hairs and sticky mucus lining the airways that is produced at a rate of about a quart a day. It contains antimicrobial agents that help to neutralize harmful germs and many viruses. Importantly, hair-like projections on cells lining the airways, called cilia, move the soiled mucus out of the lungs and air passages to the throat to be swallowed and destroyed by stomach acid.
Pollutants reaching the alveolar gas-exchanging membranes are removed by specialized cells called phagocytes and macrophages that ingest particles to move most to be carried away via lymph vessels and nodes.
However, much of the black carbon is merely moved to non-exchanging portions of the lung. In addition to conditioning air for the alveoli, ventilation of the lungs helps to cool the body down when it is overheated. About 7 percent of body heat is removed via evaporation from airways inside and outside the lungs. Eleven ounces of water per day are lost as water vapor. Three percent of body heat is lost by heating air below body temperature as the lungs are ventilated. Other amazing functions of the lungs include controlling the acid-base balance pH of the body as a whole by selectively retaining or eliminating carbon dioxide.
In order to be ventilated for gas exchange, the lungs act as bellows. At both hila, the arrangement of structures from anterior to posterior is pulmonary vein, pulmonary artery, and principal bronchus.
Bronchial vessels are the posterior-most structures at both hila. A thorough knowledge of variations in lung anatomy is of prime significance during surgical procedures such as lobectomy, pneumonectomy, and segmentectomy of lungs. Though there are few studies published regarding variations in lobes and fissures of the lungs, the literature is yet scarce about the structures at hilum of lungs. Hence, the aim of the present study was to document variations in hilar anatomy arrangement and number of lungs and variations in fissures and lobes of lungs if any.
Arrangement of pulmonary hilar structures was meticulously observed. Any deviation in normal pattern of presentation was recorded and documented in the form of photographs.
Lungs which exhibited pathological changes at hilar region and mutilations were excluded from the study. Normal pattern of the arrangement of hilar structures was seen in 22 right Variation in pattern of the arrangement of hilar structures was observed in 14 right Variations were seen in one of the following ways:.
Deviation from the number of structures present in hilum. Deviation from normal pattern of the arrangement of structures in hilum. Variations in the number of lobes in lung. Variations were more common in the left lung. All the variations are summarized in Table 1. Structure which showed the highest variation at both the lung hila was the pulmonary vein. More than two pulmonary veins were seen in 13 Multiple bronchi at the hilum were seen in 6 Two right lungs 5. More than one pulmonary artery was seen in both the lungs but was more common in the right lungs as depicted in Table 1.
Deviation from normal pattern of the arrangement of structures was seen in one 2. The left lung showed the arrangement of structures from anterior to posterior as pulmonary artery, principal bronchus, and pulmonary vein. Six of the right lungs showed the arrangement of structures from above downward as pulmonary artery, bronchus, and pulmonary vein.
Two of the right lungs showed the arrangement of structures from above downward as bronchus, pulmonary artery, and pulmonary vein. They were seen more frequently in the left compared to the right lungs. One right lung specimen 2. Three of the left lungs showed three lobes and the other two left lungs showed an incomplete oblique fissure. The variations observed have been displayed in Figure 1.
The respiratory system starts developing by day 22 of the intrauterine life when a diverticulum forms as an evagination of the foregut. By day 26—28, the diverticulum immediately bifurcates into two primary bronchial buds. At around 5 th week of intrauterine life, the right bronchial bud branches into three secondary bronchial buds and the left bronchial bud branches into two, and by the 6 th week, secondary bronchial buds branch into tertiary bronchial buds to form bronchopulmonary segments.
Pulmonary veins have a similar number of branches but are separated from airways by alveoli. Pulmonary vessels form in mesenchyme by vasculogenesis.
Airways act as a template for the development of blood vessels. This ranges from an abnormal number of pulmonary lobes or bronchial segments to the complete absence of a lung.
Branching morphogenesis of the respiratory tree is regulated by reciprocal interaction between endoderm and surrounding mesoderm. Replacement of tracheal mesenchyme with that of bronchial bud will stimulate ectopic tracheal budding and branching. A thorough literature search showed only two recent studies similar to the present one. Hence, the findings of the present study will be compared with these two studies done by Murlimanju et al.
Similar study was done by Murlimanju et al. Similar to the previous study in the present variations in pulmonary hilar structures is seen higher in the left lungs. We also found the prevalence of variable hilar structures is higher in the right lungs compared to the previous study. George et al. Murlimanju et al. In the present study, we saw it in
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