Answer for The Cases on Respiratory System (Quiz)

Assalamualaikum and a very good morning, here are the answers for the cases posted before on facebook. Hopefully you will get some benefits from this quiz. Insyaallah.

Case 1

A

• The microscopic changes leading to emphysema.
• Chronic irritation of the respiratory tract by cigarette smoke causes macrophages and neutrophils to proliferate.
• Activated neutrophils, in turn, release protease enzymes, one of which, called elastase, can chemically destroy elastin protein found in lung tissue.
• Normally, the activity of elastase is modulated by another enzyme called alpha-1 antitrypsin.
• However, alpha-1 antitrypsin is destroyed by the free radicals produced by cigarette smoke.
• This tips the balance in favor of elastase and sets the stage for the slow, gradual destruction of elastin in the walls of the alveoli and the connective tissue between adjacent bronchioles.
• Multiple alveoli coalesce into larger air pockets, destroying much of the surface area previously available for gas exchange.
• Furthermore, destruction of the elastic connective tissue between adjacent bronchioles causes them to collapse, especially during exhalation, leading to the trapping of air in the alveoli and the ultimate "barrel chest" appearance of Joe's thorax.
• To overcome the obstructed airways, Joe must use his accessory muscles of respiration (i.e. the sternocleidomastoids, pectoralis minors, and scalenus muscles).

B

• The loss of alveolar surface area due to emphysema makes it difficult for Joe to take in sufficient oxygen and excrete carbon dioxide at a sufficient rate.

C

• Joe's arterial blood pH is lower than normal because he is having a difficult time excreting carbon dioxide (CO2) from his bloodstream at an adequate rate. Since CO2 is continuously produced as a by-product of cellular respiration, its level rises in Joe's bloodstream, where it binds to water to produce carbonic acid, which dissociates into hydrogen ion and bicarbonate ion in the following reversible buffering reaction:
• CO2 + H2O <—> H2CO3 <—> H+ + HCO3-
• Thus, as CO2 accumulates, H+ concentration rises, lowering the pH of the bloodstream. Joe is hypoventilating to the point that his blood pH has fallen below normal, a condition known as respiratory acidosis.

Case 2

A

• "Bronchogenic" refers to something that arises from the bronchi of the lungs.
• "Carcinoma" is the general term for malignant tumors (or "cancers") that arise from epithelial tissue.
• A bronchogenic carcinoma is a malignant tumor that arises from the epithelial lining tissue of the bronchi.
• The majority of bronchogenic carcinomas fall into one of four categories, based upon their histologic characteristics: (A) squamous cell ("epidermoid") cancer, (B) small cell ("oat cell") cancer, (C) large cell ("anaplastic") cancer, and (D) adenocarcinoma.
• The first three types are strongly correlated with cigarette smoking. In fact, only about 2% of all lung cancers occur in non-smokers. It is likely that Alden's tumor is either a squamous cell, small cell, or large cell carcinoma.
• Adenocarcinomas are less commonly associated with cigarette smoking, and they more commonly arise in the periphery of the lungs.

B

• Cancer is a biological phenomenon in which cells are triggered to undergo uncontrolled cell division.
• The proliferating cells are often (but not always) poorly differentiated and tend to metastasize (or spread) from their area of formation to surrounding or distant tissues.
• There are probably hundreds of causes of cancer and several mechanisms of carcinogenesis (cancer formation).
• Epithelial tissue is particularly prone to carcinogenesis, possibly for the following reasons:
• (A) this tissue lines all body surfaces, inside and out, and is thus the first tissue that carcinogenic (cancer-causing) agents strike upon entry into the body.
• (B) most types of epithelium divide fairly rapidly under normal circumstances, and thus may be more susceptible to the intracellular triggers of uncontrolled cell division.

C

• Severe infectious bronchitis may occasionally cause blood to appear in the sputum.
• The hemoptysis may also be due to a bronchogenic carcinoma.
• Cancerous growths often have a rich blood supply, and they frequently bleed into neighboring tissues.
• In addition, a cancer that is rapidly enlarging can damage already existing blood vessels.
• Since Alden's cancer is near the bronchial surface, blood may spill into the bronchial tree and be coughed upward (i.e. hemoptysis)