The Anatomy of the Lungs - Assignment Example

Question A) The Anatomy of the Lungs The pair of adult lungs plays a vital role in the oxygenation of every part of the body. They allow gas exchange so as to provide the body its essential needs of oxygen and make way to release the excess and unimportant by-products of this process. As likened by Wang (2002), the respiration system, which mainly includes the lungs, assumes an inverted tree form (p. 2). As the air is inspired, it travels from the trachea which represents the trunk of the tree, and continues to its smaller branches in the form of the bronchi and bronchioles until it reaches the farthest yet most important part, the alveoli being the leaves. To better understand the physiology of the airway and its system, it is encouraged to know the anatomy first. With this in mind, the paper will try to explain the anatomy of the lungs of an adult person with presumed healthy and complete parts of it. The Right and the Left Lungs. Normally, the human body has a pair of lungs floating freely inside the pleural cavity which is made up of epithelial membranes forming the pleura. The one which is faced to the lungs is the visceral pleura and the outer is called the parietal pleura. The lungs are contained inside the thoracic cavity and are situated beside each other; thus, the right and the left. They are divided by the mediastinum. Although they are basically and supposedly aren’t connected with any other part in the cavity, they are technically attached to it by its root and the ligamentum pulmonale. When held, the lung would feel “light, soft, and spongy in texture” and can float when placed in a container with water (Cunningham & Robinson, 1918, p. 1091). According to the authors, the color of the lungs is dependent on the age of a person. It appears rosy-pink in its early years and is darker in adults. This is due to the exposure levels of the lungs to dusts and other impurities. The Lungs and Its Form. The form of the lungs is essentially the result of the structure of the thoracic cavity. As the airways seem to represent an inverted tree, the individual lungs are like inverted cones with the tip of the lung in the superior part and the wider part as its inferior and forming its base. The tip is called the apex and the flat surface is the base. The right lung is slightly larger than the left and is, at the same time, bulkier (Gutman, 2009, p. 77). According to Cunningham and Robinson (1918), the location of the liver below the right lung contributes to this (p. 1091) along with the presence of the flat diaphragm underneath the both of them. This then forms the diaphragmatic surface of the lungs which is characteristically hallowed. In addition, the left lung is compressed due to the position of the heart inside the cavity. Radix Pulmonis. The radix pulmonis or the root of the lung is the fused name of the structures that go in and out of the lungs through the hilum. These structures include the principal bronchi, the pulmonary artery and veins, the bronchial nerves and veins and the lymph vessels (Kahle, Leonhardt, & Platzer, 1991, p. 132) which supplies blood, air and nerve impulses necessary for its functioning. The Lungs, Its Lobes, Segments and Lobules. Despite their almost-the-same structure, visible differences appear to characterize the right and left lungs from each other. The right lung has three lobes, the left has two. The individual lobes are then further divided into ten bronchopulmonary segments in the right and eight in the left. The segments are divided into subsegments and secondary lobules which contain the littlest part of respiratory bronchioles that are grouped to form the terminal bronchioles. These lead to the formation of the centrilobular bronchioles in the left and right bronchi. Such structural formation poses a benefit as each lobe can act independently from each other. Hence, it is alright to remove one part of the lung and leave the rest to perform the same function in case disease will occur. The capillaries, on the other hand, come from the branching of large pulmonary artery into arterioles. These capillary networks make it possible to exchange oxygen and other nutrients into the tissues with the by-products of metabolism like carbon dioxide and other metabolic wastes. Figure 1 shows exactly how the branching pattern goes; and figure 2 represents as to where the the process of exchanging of substances needed for metabolism. Figure 1. The division pattern of the lungs and airways (Virtual Medical Centre, 2002). Figure 2. Exchange process of metabolic nutrients and wastes (“Pulmonary alveolus,” 2006). The Alveoli. At the end of the division of the smallest terminal bronchioles, air ducts are formed ending into the alveolar sacs. They resemble grapes that are bunched together and are called alveoli. There are about 300 million of them in an adult lung, 150 million at each side (Bui & Taira, 2010, p. 4; Levitzky, 2003, p. 49). It is in this site that the capillaries that have been mentioned exchange oxygen and carbon dioxide. When flatly laid down, these alveoli would have formed a single tennis court. The alveoli “consist of one layer of cells, simple squamous epithelium” (Research & Education Association, 2004, p. 90). A substance called surfactant is released from certain parts of these epithelia to keep the alveoli from collapsing. They are purposely secreted to protect the inner surface of each alveolus from the pressure that the presence of water molecules inside. Collapse is prohibited as it inhibits the exchange of gas at the site, the main purpose of the respiratory system. Along with these surfactants are the macrophages. Since impurities such as dust, bacteria, and pollutant are inevitably inspired during the process of respiration, the body also produces macrophages to engulf them and serve as the cleaners of the lungs. Together with the bronchioles and the alveolar ducts, alveoli forms part of the basic functional unit of the lungs. (Question B) The Pathophysiology of Pneumonia Pneumonia is an infection caused by viral, bacterial, fungal or protozoal organisms which results to the inflammation of the lung parenchyma or the alveoli. It is one of the leading causes of death in the United States and also worldwide (Madara & Pomarico-Denino, 2008, p. 246). The process of infection can be triggered by way of inhalation or aspiration of the causative agent. However, developing it through hematogenous infection is not uncommon (Hoffman, Walker, Wadman, Caudill II, & Bott, 2004, p. 191). Upon acquiring the disease, classification can include origin, location [bronchopneumonia, lobular, or lobar] and type [primary or secondary, or nosocomial, community or hospital-acquired]. Causes such as suctioning, intubation, aspiration of gastric juice, inhalation of smoke or chemical fumes which can irritate the integrity of the organs involved, are also possible to cause the development of the disease (Crutchlow, Dudac, MacAvoy, & Madara, 2002, p.112). Normally, when infection is detected, primary immune response is triggered and mediated. However, in people who are very young or have compromised immune defense systems such as in the elderly and debilitated ones, these defenses are insufficient to fight against the invading foreign agents and materials in the body. In situations like these, the pneumonia-causing agents can continue to invade the lung parenchyma releasing harmful toxins which activate ineffective immune and inflammatory response. This process then follows a series of stages as prescribed by Crutchlow, Dudac, MacAvoy, and Madara. The first of these stages involves “vascular engorgement of the capillary bed and serous fluid leaks into the alveoli” (Crutchlow et at., 2002, p. 112). By this time, fever, chills, aching chest, malaise, dyspnea and watery phlegm will be observed in the patient. White blood cell count (WBC) will also increase in the presence of the immune response. Since mucus is continually produced, fine crackles will be observed upon auscultation. Entrance to the next stage will be characterized by the invasion of red blood cells and fibrin into the alveoli. This stage is named as the red hepatization stage and is followed by the gray hepatization stage. During gray hepatization, the disease-causing agent, and both red and white blood cells with the blood clotting substance fibrin consolidate inside the alveoli; and thus, giving off a gray appearance of the lungs upon viewing. Since air is prevented from entering the alveoli, exchange of gas is halted. Hence, dyspnea is apparent. Other more severe complications can result to this if condition is left untreated. The following images are presented to signify how the alveoli are prevented from functioning normally as they pus and other substance are accumulated inside them. Figure 3. The normal exchange of gases is interrupted by accumulated fluids (Badash, 2006). Figure 4. (a) Lobar Pneumonia (National Heart Lung and Blood Institute, n.d.). Since the bacteria are already inside the body, entering into the bloodstream is possible especially when it is untreated or has been present for a long time. Complications may range from infection to the adjacent parts of the lungs through building up of fluid such as to its chest wall to the infection of the blood called bacteremia which can lead to septicemia, the spinal cord meninges called meningitis, the bones or osteomyelitis, and the heart muscles of the covering of the heart and even to the joints causing a condition called septic arthritis (“What’re the,” 2005). There are many ways to confirm the presence of pneumonia. Culture and sensitivity, complete blood counts, bronchoscopy, pulse oximetry, and arterial blood gases (Lippincott Williams & Wilkins, 2002, p. 187; Crutchlow et al., 2002, p. 112) can support the diagnosis of pneumonia together with the symptoms as mentioned above. However, many medical practitioners have frequently over diagnosed the condition of pneumonia even without substantial evidences to the diagnosis (Speets et al., 2006). According to the Merck (2008) online manual, chest radiographs (CXR) are used as confirmatory tool in the diagnosis of pneumonia. Misdiagnosis can also be prevented (Speets, et al., 2006) when using CXR will be widely practiced in the clinical setting before confirming the condition. The following radiographic images show the presence of inflammation of specific parts of the lungs. Figures 7 & 8 show the basic functional parts of the lungs as the infection spreads. Figure 5. Lobar Pneumonia (Radiographical Society of North America, n.d.). Figure 6. Lobular Pneumonia (Radiology Teacher, n.d.) Figure 7. Bronchopneumonia (MedMinia, n.d.). Figure 8. Diffuse alveolar pneumonia (Xraypedia.com, 2008). Figure 9. Pneumonia can cause bilateral interstitial infiltrates (IslamicBoard.com, 2008). The next images, on the other hand, illustrate the spread of staphylococcal infection to the bones and joints as the bacteria causing the pneumonia have entered the bloodstream and into different parts. Figure 10. The arrow points to the patchy destruction of the left glenoid caused by osteomyelitis as a result of the pneumonia (Khan, 2009). Figure 11. Septic arthritis resulting from pyogenic infection such as bronchopneumonia (Acute Osteomyelitis, 2008). Figure 12. Osteomyelitis in a childs shin bones caused by staphylococcus aureus (Modric, 2008). References Acute osteomyelitis. (2008). Retrieved from http://www0.sun.ac.za/ortho/ webct-ortho/osteitis/osteitis.html Badash, M. (2006). Pneumonia. Retrieved from http://www.beliefnet.com/healthandhealing/getcontent.aspx?cid=11617 Bui, T. A. T., & Taira, R. K. (2010). Medical imaging informatics. New York, NY: Springer. Crutchlow, E. M., Dudac, P. J., MacAvoy, S., & Madara, B. R. (2002). Pathophysiology. Thorofare, NJ: SLACK Inc. Cunningham, D. J., & Robinson, A. (1918). Cunningham’s text-book of anatomy (5th Ed.). New York, NY: William Wood and Company. Gutman, H. (2009). Lung cancer and mesothelioma. USA: Howard Gutman. Hoffman, L. 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