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Respiratory System Diseases

Respiratory System Diseases
The respiratory system could get affected by infections or diseases due to a wide range of reasons. The following HealthHearty write-up provides information on some of the common respiratory system diseases.
Ratnashri Dutta
Last Updated: May 31, 2018
3D illustration of Lungs medical concept.
The human respiratory system is divided into the upper and lower respiratory tract. The upper respiratory tract comprises the nasal cavity, pharynx, and larynx, whereas the lower respiratory tract is composed of the trachea, bronchi, and the lungs. The inhaled air moves through the trachea and bronchi into the lungs, which are paired sponge-like organs located on either side of the chest. The exchange of oxygen and carbon dioxide occurs within the alveoli, which are clusters of microscopic air sacs located at the end of bronchioles in the lungs. Pleura refers to the two-layered membranous structure that lines the lungs and the inner walls of the chest. The space between the two layers contains a small amount of fluid that lubricates the membranes.

Though the human body employs various mechanisms to destroy the disease-causing bacteria, viruses, fungi, etc., and prevent the environmental irritants from causing damage, sometimes the immune system is unable to do so. Pathogens and pollutants enter the respiratory system through the inhaled air and multiply, thereby leading to inflammation of different parts of the respiratory tract.
Upper Respiratory Tract Infections
Upper respiratory infections, as the name suggests, are infections involving the upper respiratory tract. Some of the common upper respiratory tract infections include:
Rhinitis refers to the inflammation of the mucous membrane lining the nose. Allergic rhinitis occurs when a person inhales something that he/she might be allergic to. For instance, some people may develop allergic rhinitis due to the inhalation of allergens such as pollen, mold, dander, etc. Some of the characteristic symptoms of rhinitis include runny nose, sneezing, watery eyes, nasal congestion, sore throat, etc. Nonallergic rhinitis is said to occur when the nasal mucosa gets inflamed due to exposure to environmental/occupational irritants, weather changes, or viral infections (common cold or flu). 
The sinuses are air-filled cavities located in the skull. When the nasal passages or sinuses become inflamed, the sinus openings become blocked, which in turn, affects the drainage of mucus in an adverse manner. The moist environment created by blocked sinuses increases the chances of infections. Allergies and infections (bacterial, viral, or fungal) are the main contributing factors for the inflammation of the sinuses. Nasal passages or sinuses can also get blocked due to nasal polyps or deviated septum. The symptoms of sinusitis include sinus pressure, congestion, stuffy nose, loss of smell, fatigue, fever, etc.
Laryngitis refers to the inflammation of the larynx, which is also known as the voice box. Exposure to pathogens that cause common cold, flu, or bronchitis can cause laryngitis. Irritation due to exposure to environmental irritants could also cause the vocal cords to swell. Hoarse voice is the main symptom of this condition. It could also cause loss of voice, pain while swallowing, sore throat, fever, etc.
Tonsils are masses of lymphoid tissue located on either side at the back of the throat. It is believed that tonsils filter and trap the pathogens, preventing them from entering the airways. Tonsillitis refers to the inflammation of tonsils due to exposure to Streptococcus aureus bacteria or viruses such as Adenoviruses, Influenza viruses, Epstein-Barr virus, Parainfluenza viruses, Enteroviruses, etc. Tonsillitis is usually characterized by symptoms such as throat pain, sore throat, enlarged tonsils, fever, or difficulty in swallowing.
The inflammation of the pharynx occurs due to overgrowth of bacteria, viruses, or other pathogens in the throat. Exposure to bacteria such as Group A Streptococcus, Mycoplasma pneumoniae, and Chlamydophila pneumoniae, or viruses that cause infectious mononucleosis, common cold, or influenza could cause pharyngitis. Sore throat is one of the common symptoms of pharyngitis. The affected individuals might also experience symptoms such as fever, muscle aches, cough, earaches, malaise, or difficulty in swallowing.
Lower Respiratory Tract Infections
The lower respiratory tract comprises the bronchi and the lungs. The causal agents for lower respiratory tract infections could be bacteria, viruses, fungi, etc. Prolonged exposure to environmental irritants could also be a contributing factor. Here's some information on the types of lower respiratory tract infections.
Pneumonia is a respiratory condition that is characterized by the inflammation of the lungs. Pneumonia could affect one or both lungs. Streptococcus pneumoniae is often the causative agent for bacterial pneumonia. Viral infections such as common cold and flu could also progress to pneumonia, if proper care is not taken. The symptoms of pneumonia include labored breathing, cough, fever, chills, shortness of breath, malaise, etc. Pneumonia could also cause pleurisy (inflammation of the pleura) and pleural effusion (accumulation of fluid between the layers of the pleura, leading to shortness of breath or painful breathing).
Bronchitis refers to the inflammation of the bronchi, which are the main airways that carry inhaled air to the lungs. This respiratory condition is caused by infections or exposure to tobacco smoke, dust, fumes, or other environmental pollutants. It could be acute or chronic. Acute bronchitis is characterized by sudden onset of symptoms, and lasts for a couple of weeks. More often than not, viruses responsible for causing common cold and flu are also the causal agents for acute bronchitis. Affected people usually experience symptoms such as cough, tightness in chest, wheezing, fever, labored breathing, or fatigue. Chronic bronchitis develops gradually, and lasts for more than three months.
Bronchiolitis refers to the inflammation of bronchioles, which are the smaller branches of the main airways. It usually affects premature infants. Though the respiratory syncytial virus is one of the common causal agents, influenza virus could also cause bronchiolitis. Though the symptoms are mild at the onset, symptoms such as nasal congestion, severe cough, wheezing, or fever appear within a couple of days. Oxygen therapy might be required in cases wherein the affected child experiences respiratory distress and cyanosis (bluish discoloration of the skin). Affected children are at an increased risk of developing asthma.
Asthma is characterized by inflamed and constricted airways. The narrowing of the airways restricts the flow of air into the lungs. Inhalation of certain substances irritates the airways, causing them to tighten and become sensitive. Increased production of mucus may further constrict the airways, obstructing air flow. The symptoms of asthma include wheezing (whistling sound while breathing), chest tightness, coughing, and shortness of breath. The symptoms may be mild or severe. Timely treatment is essential in case of flare-ups.
Pleural cavity refers to the space between the pleura or the serous membranes that line the lungs and the chest wall. A small amount of liquid is present in the pleural space. As the lungs inflate and deflate during inhalation and exhalation, this fluid helps the pleural membranes to slide over each other, thereby allowing the lungs to move smoothly within the chest cavity. Pneumothorax, which is commonly known as collapsed lung, is a medical condition wherein air gets accumulated within the pleural space. This causes pressure to build up over the lungs. As a result, the lungs are not able to expand properly during inhalation. The risk factors could include trauma to the chest, or medical conditions such as tuberculosis, whooping cough, cystic fibrosis, asthma, or chronic obstructive pulmonary disease (COPD).
Chronic Obstructive Pulmonary Disease
COPD refers to a group of lung diseases called chronic bronchitis, emphysema, and chronic obstructive airways disease. Emphysema is a progressive lung disease that is characterized by the decreased elasticity of the lung tissues and formation of irregular pockets in the alveoli. Chronic smokers are at an increased risk of developing this condition. Airway reactivity and deficiency of alpha-1-antitrypsin enzyme are the other risk factors. Shortness of breath, labored breathing, rapid breathing, wheezing, chronic cough, chest tightness, and reduced tolerance for physical activities are some of the symptoms associated with this condition. Emphysema and/or chronic bronchitis result in blockage of the airways, thereby leading to chronic obstructive airways disease. Cough, excessive phlegm, recurring chest colds, wheezing, and shortness of breath on exertion are some of the symptoms of chronic obstructive airways disease.
Pulmonary Fibrosis
Pulmonary fibrosis is characterized by scarring throughout the lungs. Long-term exposure to toxins/pollutants (silica dust, asbestos, grain dust, etc.) or chronic inflammatory conditions such as tuberculosis, systemic lupus erythematosus, rheumatoid arthritis, sarcoidosis, or scleroderma, could be the contributing factors. People who are undergoing radiation treatment or chemotherapy are also at a risk. Lungs could also get damaged due to the prolonged use of certain antibiotics. The symptoms of pulmonary fibrosis include shortness of breath, cough, and decreased tolerance to exercise.
Tuberculosis (TB) is a highly infectious disease. The causal organism for TB is one of the strains of bacteria belonging to the Mycobacterium tuberculosis complex. When the infection is restricted to the lungs, the affected individual is diagnosed with pulmonary tuberculosis. This infection can spread from person to person, when the bacteria become airborne. When the individual with an active TB disease coughs or sneezes, others can inhale the bacteria. People with a compromised immune system are susceptible, as their immune system may not be able to fight the infection. The common symptoms of TB include cough, fever, weight loss, loss of appetite, etc. The affected individual might cough up blood-stained phlegm.
Cancer refers to the development of a malignant growth due to an abnormal and uncontrolled cell division. It could affect any part of the respiratory tract. Lung cancer, which is caused due to abnormal and uncontrolled division in the cells of the lung tissues, is one of the leading causes of cancer-related deaths in the United States. When the cancer originates in the lungs, it is referred to as primary lung cancer. When the cancer originates in some other part of the body, and spreads or metastasizes to the lungs, it is referred to as secondary lung cancer. It is categorized into small cell lung cancers (SCLC) and non-small cell lung cancers (NSCLC). Though heavy smokers are at an increased risk of developing this serious condition, non-smokers with a family history are also susceptible. Risk factors also include alcohol abuse and prolonged exposure to asbestos or radon gas. The symptoms of lung cancer include persistent cough, shortness of breath, chest pain, wheezing, blood-stained sputum, unexplained weight loss, etc.
Exposure to pollutants, allergens, and disease-causing agents is often the contributing factor for most respiratory system diseases. Many respiratory infections spread by person-to-person contact, which is why, precautionary measures must be followed when the incidence of such infections is high. Avoid contact with people who exhibit the symptoms associated with respiratory infections. Avoidance of the triggers is the best precautionary measure for people affected by allergies, asthma, allergic rhinitis, etc. Smoking is one of the major risk factors for these conditions, which is why, it would be in one's best interest to quit smoking. Medical help must be sought to treat respiratory problems. Antibiotics, antiviral drugs, and antifungal drugs are often prescribed for treating bacterial, viral, and fungal infections respectively. Antipyretics, anti-inflammatory drugs, or immune-modulating drugs might be prescribed in some cases. Inhaled corticosteroids or bronchodilators are prescribed for treating conditions that are characterized by constricted airways. The treatment options for cancer involve chemotherapy or radiation therapy. Surgery might be suggested for the removal of the malignant growth.
Disclaimer: The information provided in this article is solely for educating the reader. It is not intended to be a substitute for the advice of a medical expert.