A pulmonary lobule is a subdivision formed as the bronchi branch into bronchioles. Each lobule receives its own large bronchiole that has multiple branches. An interlobular septum is a wall, composed of connective tissue, which separates lobules from one another. The blood supply of the lungs plays an important role in gas exchange and serves as a transport system for gases throughout the body. In addition, innervation by the both the parasympathetic and sympathetic nervous systems provides an important level of control through dilation and constriction of the airway.
The major function of the lungs is to perform gas exchange, which requires blood from the pulmonary circulation. This blood supply contains deoxygenated blood and travels to the lungs where erythrocytes, also known as red blood cells, pick up oxygen to be transported to tissues throughout the body. The pulmonary artery is an artery that arises from the pulmonary trunk and carries deoxygenated, arterial blood to the alveoli.
The pulmonary artery branches multiple times as it follows the bronchi, and each branch becomes progressively smaller in diameter. One arteriole and an accompanying venule supply and drain one pulmonary lobule. As they near the alveoli, the pulmonary arteries become the pulmonary capillary network. The pulmonary capillary network consists of tiny vessels with very thin walls that lack smooth muscle fibers.
The capillaries branch and follow the bronchioles and structure of the alveoli. It is at this point that the capillary wall meets the alveolar wall, creating the respiratory membrane.
Once the blood is oxygenated, it drains from the alveoli by way of multiple pulmonary veins, which exit the lungs through the hilum. Dilation and constriction of the airway are achieved through nervous control by the parasympathetic and sympathetic nervous systems. The parasympathetic system causes bronchoconstriction , whereas the sympathetic nervous system stimulates bronchodilation. Reflexes such as coughing, and the ability of the lungs to regulate oxygen and carbon dioxide levels, also result from this autonomic nervous system control.
Sensory nerve fibers arise from the vagus nerve, and from the second to fifth thoracic ganglia. The pulmonary plexus is a region on the lung root formed by the entrance of the nerves at the hilum. The nerves then follow the bronchi in the lungs and branch to innervate muscle fibers, glands, and blood vessels. Each lung is enclosed within a cavity that is surrounded by the pleura. The right and left pleurae, which enclose the right and left lungs, respectively, are separated by the mediastinum.
Horizontal fissure was absent in 3. Four point six one percentage of right lungs had 3 fissures and 4 lobes. Three point zero seven percentage of right lungs had 3 arteries, Sixty-three point zero seven percentage of right lungs had two veins in the hilum; Ninety-eight point four six percentage of right lungs showed 2 bronchi in the hilum, and 1. Two of the right lungs 3. Fifteen point zero six percentage of left lungs showed incomplete oblique fissure and 2.
Five point four seven percentage of left lungs showed 2 arteries and Eighty point eight two percentage of left lungs had two veins in the hilum and Twenty-one point nine one percent of left lungs had 2 bronchi and The knowledge of variations in the lobar and hilar anatomy of the lung presented in this study is clinically important while interpreting the radiological images and performing surgical procedures.
The lungs are essential organs of respiration and are situated in the thoracic cavity on either side of the mediastinum. Being vital organs of respiration, the lungs are divided by fissures into lobes which facilitate movements of lobes in relation to one another.
Amongst the pair, the right lung is divided into three lobes namely upper, middle and lower by oblique and horizontal fissures. The left lung is divided into two lobes namely upper and lower by oblique fissure [ 1 ]. The arrangement of lung tissue into lobes by fissures facilitates the movements of the lobes in relation to one another thus helping in uniform expansion of the whole lung in inspiration [ 2 ]. Behind the cardiac impression in mediastinal surface each lung shows a triangular depression named the hilum, where the structures which form the root of the lung enter and leave the organ.
Both the lungs admit two pulmonary veins and one pulmonary artery through the hilum. The bronchi differ in their mode of subdivision between the left and right lungs [ 1 ]. The right bronchus gives off a branch to the superior lobe about 2.
As this branch arises above the level of the pulmonary artery it is named as the eparterial bronchus. Other division come off below the artery and thus termed hyparterial bronchus.
The left bronchus passes below the level of pulmonary artery before it divides and so all its branches are hyparterial. Understanding of the normal anatomy is very essential foundation of the surgical knowledge. Though the fissures and the lobar pattern of the lungs are studied in a few populations, the hilar anatomy of the lungs has been overlooked [ 3 ]. Variant anatomy may lead to misinterpretation of a radiograph or computed tomography CT scan [ 4 ].
Certain radiological findings can mislead the diagnosis as in the cases of extra lobes, as it may misinterpret as lung lesions. In the presence of extra lobes, the CT scan shows a significant increase in the size of mediastinum around the trachea [ 5 ]. The accessory fissure might alter usual pattern of lung collapse in patients with endobronchial lesion, and pose difficulty in diagnosing the extent of lesion. Normally pneumonia will be restricted to the lobes affected by it, but in patients with incomplete fissures, it may spread to adjacent lobes through the parenchymal continuation [ 6 , 7 ].
In the current study, we focused on the morphological variations of the lungs in the south Indian cadaveric samples. One hundred thirty-eight isolated, adult formalin fixed cadaveric lungs preserved in the dissection hall were observed for the study. The lungs belonged to the adult age group between years. No gender difference of the lungs was made in this study.
Only those lungs which were covered all over by pleura except at the hilum were used in the study. If any part of the lung was cut off during its removal, such lung was excluded from the study.
Too low perfusion and a higher ratio indicates alveolar dead space, while too low ventilation and a lower ratio indicates a shunt, which is a lack of air supply relative to perfusion. The lungs are located on either side of the heart and are separated by fissures into lobes, three in the right and two lobes in the left.
The lungs are located in two chambers of the thoracic cavity on either side of the heart. Though similar in appearance, the two lungs are not identical, nor wholly symmetrical. Fissures are double folds of pleura that divide the lung into lobes. There are three lobes in the right lung and two in the left lung. The lobes are further divided into segments and then into lobules, which are hexagonal divisions of the lungs that are the smallest visible subdivision.
The lobes are further divided into segments and then into lobules, hexagonal divisions of the lungs that are the smallest subdivision visible to the naked eye. The lobes of the lungs : The right lung has three lobes and the left lung has two. The right lung is five centimeters shorter than the left lung to accommodate the diaphragm, which rises higher on the right side over the liver; it is also broader. The volume, the total capacity, and the weight of the right lung is greater than that of the left.
The right lung is divided into three lobes. The upper lobe is the largest lobe of the right lung. It extends from the apex of the lung down to the horizontal and oblique fissures. It bears apical, anterior, and posterior bronchopulmonary segments. The middle lobe is the smallest lobe of the right lung, located between the horizontal and oblique fissures.
It bears medial and lateral bronchopulmonary segments. The lower lobe is the bottom lobe of the right lung. It lies beneath the oblique fissure.
It bears medial, lateral, superior, anterior, and posterior bronchopulmonary segments. The Left Lung : This has a concave depression that accommodates the shape of the heart, called the cardiac notch.
The human left lung is smaller and narrower that the right lung, and is divided into two lobes, an upper and a lower, by the oblique fissure. The left lung has only two formal lobes because of the space taken up in the left side of the chest cavity by the heart, though it does have the lingula, which is similar to a lobe. The left lung has a depression on the medial side of its surface called the cardiac notch, a concave impression molded to accommodate the shape of the heart.
The upper lobe of the left lung contains anterior and apicoposterior bronchopulmonary segments. It is above the oblique fissure. The lower lobe of the left lung contains superior, anterior, posterior, medial, and lateral bronchopulmonary segments.
The lingula is not formally considered to be a lobe. It is a small, tongue-like projection of the left lung that is analogous to the middle lobe of the right lung. It contains superior and inferior bronchopulmonary segments.
Above and behind the cardiac impression is a triangular depression named the hilum. The hilum is the root of the lung where that contains structures that supply the lungs with blood, lymph fluid, and innervation, such as the pulmonary vein, pulmonary artery, pulmonary nerves, and lymphatic vessels. The lung is "stuck" to this sack by a small amount of liquid, which creates surface tension. It creates a very smooth surface so that as the lungs expand and contract they can ride over the heart and surrounding elements.
Since each lung is in a separate pleural sac, if the chest wall gets punctured, only one lung will collapse. The lungs are "stuck" to the inside of the thorax, also by surface tension. As the ribcase and diaphragm move, the lungs are stretched, drawing air into the lung, or the lungs are compressed, pushing the air out.
Residual Volume: the quantity of air that remains in the lungs and airways, even after a maximum exhalation -. When breathing very shallowly, the accumulation of CO 2 makes us yawn -.
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