Respiratory System: Breathing Process and Common Diseases
Breathing
Breathing is the process of taking in oxygen from the air and transporting it to the cells, where it’s used in chemical reactions to produce energy. These reactions generate carbon dioxide, which is expelled during exhalation.
Breathing involves two phases:
- External Respiration: Oxygen moves from the air into the blood, and carbon dioxide moves from the blood into the air in the lungs.
- Internal Respiration: Oxygen travels through the blood to body cells for energy production. Carbon dioxide produced during this process is transported back to the lungs via the blood for removal.
Physiology of Respiration
Ventilation
Ventilation is the process of bringing outside air into the lungs for gas exchange. It’s a cyclical process with two phases: inspiration (inhaling) and expiration (exhaling).
Inspiration: Respiratory muscles contract, expanding the rib cage and decreasing internal pressure, drawing air into the airways. During quiet breathing, the diaphragm is the primary muscle involved. During labored breathing (e.g., exercise), additional muscles like the intercostal muscles assist.
Expiration: Respiratory muscles relax, allowing the lungs to recoil to their normal volume and expel air. Quiet expiration is passive, while forced expiration involves contraction of abdominal and internal intercostal muscles.
Gas Transfer
Gas transfer occurs through diffusion, a passive process where gases move from areas of high concentration to areas of low concentration. Oxygen diffuses from the alveoli (air sacs in the lungs) to the blood, and carbon dioxide diffuses from the blood to the alveoli.
Cellular Respiration
Oxygen in the blood binds to hemoglobin, an iron-containing protein in red blood cells. Hemoglobin’s affinity for oxygen allows it to capture oxygen in the alveoli and release it in tissues where oxygen levels are lower.
As cells use oxygen, hemoglobin releases it, and oxygen diffuses into the cells. Carbon dioxide produced by cellular reactions diffuses into the capillaries, dissolves in the blood, and is transported to the alveoli for removal during exhalation.
Respiratory Pacing
The nervous system controls breathing rate and depth to meet the body’s needs without conscious effort. Respiratory centers in the brainstem regulate this process.
Voluntary control of breathing allows us to speak, sing, etc. However, we cannot hold our breath indefinitely or engage in forced breathing for extended periods.
Respiratory Diseases
Acute Rhinitis
Acute rhinitis is a short-term inflammation of the nasal mucosa, characterized by mucus hypersecretion, difficulty breathing, reduced sense of smell, and sneezing. Causes include infection, chemical irritation, and allergies.
Sinusitis
Sinusitis is inflammation of the sinus lining, which can be acute or chronic. It’s often caused by blockage of sinus drainage, leading to mucus buildup and potential bacterial or viral infection. Symptoms include pain near the affected sinus, nasal congestion, fever, and mucus secretion.
The Common Cold
The common cold is an acute inflammation of the upper respiratory tract mucosa caused by various viruses. It typically involves rhinitis and pharyngitis, sometimes with laryngitis. Symptoms include mucus hypersecretion, difficulty breathing, sore throat, mild fever, and cough.
Influenza (Flu)
Influenza is a viral infection characterized by nasopharyngitis, fever, and muscle aches. Treatment is similar to that for the common cold, but recovery may take longer (2 weeks or more).
Acute Bronchitis
Acute bronchitis is a short-term inflammation of the bronchial tree, causing narrowing of the bronchi and difficulty breathing. It’s often caused by infection, irritants, or pollutants. Symptoms include cough, fever, difficulty breathing, chest pain, and muscle pain from coughing.
Bronchial Asthma
Bronchial asthma is a widespread obstruction of the lower respiratory tract, characterized by edema and mucus hypersecretion, leading to narrowed bronchi and difficulty breathing. It’s caused by an exaggerated bronchial response to certain substances. Symptoms include shortness of breath (especially during exhalation), rapid breathing, and wheezing.
Pneumonia
Pneumonia is inflammation of the lung tissue, particularly the alveoli, which fill with fluid, hindering gas exchange. It’s commonly caused by bacterial or viral infection or chemical irritation. Symptoms include fever, chills, cough with sputum, difficulty breathing, rapid heart rate, and potentially cyanosis (bluish discoloration of the skin).
Tuberculosis
Tuberculosis is a bacterial infection primarily affecting the lungs but can also affect other organs. It’s spread through the air by inhaling droplets from an infected person’s cough or sneeze. Symptoms can be mild initially (cough, fever, fatigue, weight loss, night sweats) but can progress to severe lung damage and involvement of other organs.
Pulmonary Emphysema
Pulmonary emphysema is a disease that irreversibly destroys the alveolar walls, impairing gas exchange and lung function. The most common cause is smoking, but it can also be caused by irritants or genetic disorders. Symptoms include difficulty breathing, cough, wheezing, and reduced exercise capacity.
Chronic Obstructive Pulmonary Disease (COPD)
COPD is a progressive obstruction of the airways, particularly the smaller ones, along with destruction of alveolar walls. It primarily affects individuals over 65 and is a leading cause of death and disability. The main causes are bronchial irritants like smoking, toxins, and air pollution. Symptoms include cough, sputum production, frequent bronchitis, and shortness of breath, which worsens over time.