![]() ![]() Dyspneic patients breathe rapidly, often laboring to draw breath even when at rest. While counting the respiratory rate, the examiner can observe other breathing characteristics. In adults, a normal respiratory rate at rest is about 12 breaths per minute. Inspection: The examiner determines the respiratory rate by unobtrusively watching the patient's chest rise and fall and counting the number of breaths per minute. The blood that is low in O but high in CO 2 is in contact with the air that is high in O and low in CO 2 for less than 1 second. This capillary surface area surrounds 300 million air sacs (alveoli). The volume of the pulmonary capillary circulation is 150 mL, but this is spread out over a surface area of approx. The blood and air are brought together so closely that only approx. This is achieved by two pumping systems, one moving a gas, and the other a liquid. The purpose of the lung is to bring air and blood into contact so that O can be added to the blood and CO 2 removed. The pulmonary arteries and veins circulate the blood involved in gas exchange. The bronchial arteries and veins circulate blood to the bronchial tree. The lungs are innervated by parasympathetic fibers via the vagus nerve and sympathetic fibers from the anterior and posterior pulmonary plexuses to the smooth muscle in the walls of the bronchial tree. This respiratory membrane is thin (0.07 to 2.0 μm) and permits oxygen (O) to diffuse into the blood and carbon dioxide (CO 2) to diffuse from the blood to the air. In the alveolus, blood and inspired air are separated only by the cells of the alveolus and of the pulmonary capillary. Each of these divides into two respiratory bronchioles, which in turn divide to form 2 to 11 alveolar ducts, from which the alveolar sacs and alveoli arise. There are 50 to 80 terminal bronchioles in each lobe. There are about 10 bronchopulmonary segments in the right lung and 8 in the left, the actual number varying. The pattern of distribution of these into the segments of each lobe is important in pulmonary and thoracic surgery. These further divide into a great number of smaller bronchioles. The primary bronchi divide into secondary bronchi, one for each of five lobes. Two primary bronchi, one on each side, extend from the trachea. Behind this is the hilum, through which the blood vessels, lymphatics, and bronchi enter and leave the lung.Īir travels from the nasal passages to the pharynx, larynx, and trachea. The left lung has an indentation (the cardiac depression), for the normal placement of the heart. The total capacity of the lung varies from 3.6 to 9.4 L in men and 2.5 to 6.9 L in women. Respirations per minute are 12 to 20 in an adult. The lungs contain 300,000,000 alveoli, and their respiratory surface is about 70 sq m. The right lung has three lobes and the left two. The lungs include the lobes, lobules, bronchi, bronchioles, alveoli (air sacs), and pleural covering. The base of each lung rests on the diaphragm, and each lung apex rises from 2.5 to 5 cm above the sternal end of the first rib, the collarbone (clavicle), supported by its attachment to the hilum or root structures. The lungs are connected with the pharynx through the trachea and larynx. ![]()
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