Physiology of Breathing and Respiration

Breathing

• Breathing is an automatic physiological process requiring no effort.
• It's a rhythmic activity controlled by the brainstem.

Physiological Respiration

• It includes two main parts:
  • External respiration: Involves bringing air into the lungs (inhalation) and releasing air to the atmosphere (exhalation). This process happens between the lungs and the atmosphere.
  • Internal respiration: Describes oxygen and carbon dioxide exchange between the cells and blood vessels. This metabolic process occurs within the body.

Respiratory System

• The respiratory system consists of an air conducting portion and a gas exchange portion.
• The gas exchange occurs in the alveoli, small air sacs where oxygen and carbon dioxide are exchanged.
• Alveoli are richly supplied with capillaries for efficient gas exchange.

Common Mistakes and Misconceptions

• Physiological respiration and cellular respiration are distinct processes. Cellular respiration is a cellular process in which carbohydrates are converted to energy.
• People do not breathe only oxygen or exhale only carbon dioxide. Air contains oxygen and nitrogen and other components. The air we exhale has more carbon dioxide than the air we inhale. But oxygen is only part of the inhaled air.
• The respiratory system works in conjunction with the circulatory system to deliver and circulate oxygen throughout the body.

Respiratory Tract

• The upper respiratory tract includes the nose, nasal cavity, paranasal sinuses, pharynx, and larynx.
• The lower respiratory tract includes the trachea, bronchi, bronchioles, and alveoli.
• The respiratory tract can be divided into a conducting zone and a respiratory zone based on the distinction of gas transporting and gas exchanging.

Respiratory Zone Structures

• The conducting zone structures include respiratory passageways and include all organs apart from the alveoli.
• The respiratory zone structures include respiratory bronchioles, alveolar ducts, and alveoli. These areas ensure the exchange of oxygen and carbon dioxide.

Muscles of Ventilation

• The muscles of ventilation are classified as primary or accessory.
• Primary muscles are recruited during quiet breathing (tidal).
• Accessory muscles are recruited during forced or labored breathing.
• The major muscles of inspiration include the diaphragm, external intercostals, sternocleidomastoids, scalenes and pectoralis major and minor.
• The major muscles for expiration include the internal intercostals, abdominal muscles (rectus abdominis, transversus abdominis, and internal and external obliques).

Movements of Thorax During Ventilation

• The thorax enlarges in all three planes during inspiration: the anteroposterior dimension, the lateral or transverse dimension, and the vertical/superior-inferior dimension (increasing the cavity's size).

Mechanism of Respiration

• The lungs are enclosed within the pleural membranes forming a pleural sac filled with pleural fluid to prevent friction.
• Boyle's law describes the relationship between pressure and volume of gases. An increase in lung volume leads to a decrease in pressure, causing air to flow in.
• Inspired air moves into the lungs when the pressure in the lungs decreases and then the pressure outside the lungs is greater. Expired air flows out when the pressure in the lungs increases.
• Breathing in involves the diaphragm and associated muscles contracting, increasing the chest cavity volume, reducing intrapulmonary pressure and causing air to rush into the lungs.
• Breathing out involves the relaxation of the muscles, allowing the chest cavity to return to its normal size, increasing intrapulmonary pressure and forcing air out.

Inspiration and Expiration

• Inspiration is the active process of breathing air into the lungs.
  • The diaphragm and external intercostal muscles contract to enlarge the thoracic cavity.
• Expiration is the passive process of letting air out of the lungs.
  • The diaphragm and external intercostals relax, and the chest cavity recoils, causing air to flow out.

Forced Breathing

• Forced breathing requires the use of accessory muscles in both inspiration and expiration.

Common Symptoms of Chest Diseases

• Dyspnea (shortness of breath) is a symptom of a variety of conditions, including respiratory, cardiac, and metabolic diseases.

• Causes of dyspnea include respiratory diseases (asthma, COPD, pneumonia, pneumothorax, pleural effusion), cardiovascular diseases (pulmonary venous pressure elevation, left ventricular failure, mitral stenosis). increased respiratory drive (hyperthyroidism), and metabolic conditions (mitochondrial myopathies).

• Orthopnea and paroxysmal nocturnal dyspnea are specific types of dyspnea.

• Cough is a common symptom of various diseases with both dry and productive components. Air irritants (e.g. smoke, inhaled dusts, foreign bodies), airway diseases (e.g. upper respiratory tract infections), parenchymal lung diseases (e.g. pneumonia, tuberculosis), and heart failure are common causes of cough.

• Hemoptysis is the coughing up of blood from the respiratory tract. The causes include pneumonia, bronchitis, bronchogenic carcinoma, and pulmonary edema.

Explore the automatic processes of breathing and the two main components of physiological respiration. This quiz will delve into the functioning of the respiratory system, including the roles of external and internal respiration, gas exchange in alveoli, and common misconceptions about respiration. Test your understanding of the essential functions that support life.