Respiratory System

Respiratory System

The respiratory system is a vital part of the human body, responsible for the exchange of gases between the environment and the bloodstream. It consists of two main parts: the lung, which is the gas-exchanging organ, and the pump that ventilates the lungs, which includes the chest wall, respiratory muscles, and central nervous system (CNS).

Upper Airway Structure

The upper airway, which includes the nose, pharynx, and larynx, serves to protect the respiratory system against environmental agents of lung disease. It does this by filtering out larger particles through impaction and smaller particles through sedimentation. The mucociliary escalator, along with macrophages, helps to remove particles that reach the alveoli, while the pulmonary circulation acts as a filter for the blood, particularly in removing blood clots.

Lower Airway Function

The conducting airways, such as the trachea and bronchi, have relatively thick walls of mucosa, smooth muscle, and cartilage. They form a typical respiratory surface, which is thin, moist, and vascular. The bronchial tree, which is disrupted in disease, has conducting airways with thick walls and respiratory airways with thin walls. The respiratory airways form a typical respiratory surface, which is thin, moist, and vascular.

Gas Laws in Respiration

Gas laws play a crucial role in the process of respiration. The partial pressures of oxygen (PaO2) and carbon dioxide (PaCO2) in alveoli and arterial blood are important factors in maintaining the balance of gas exchange. The alveolar to arterial oxygen difference (2Da-aO2) is approximately 0.67 kPa (5 mmHg), and when a normal subject hyperventilates, alveolar oxygen and carbon dioxide tension and arterial oxygen and carbon dioxide tension move down the slope in the respiratory exchange ratio of 0.8.

Oxyhaemoglobin Dissociation Curve

The oxyhaemoglobin dissociation curve is a graphical representation of the relationship between the concentration of oxygen in the blood and the proportion of oxyhaemoglobin that is saturated with oxygen. The curve is sigmoidal, meaning that small changes in oxygen concentration can lead to large changes in oxyhaemoglobin saturation. This curve is important for understanding how the body regulates oxygen delivery to tissues.

Mechanical Control of Ventilation

The mechanical control of ventilation involves the interaction of various factors, including respiratory mechanics, airway resistance, and V/Q mismatch. The mechanics of the respiratory system are influenced by the lung compliance, which is the relationship between lung volume and pressure. Changes in lung compliance can lead to altered breathing patterns, such as increased or decreased respiratory rate.

Neurological Control of Breathing

The neurological control of breathing is a complex process that involves the central nervous system, brainstem, and spinal cord. The respiratory center in the brainstem generates the drive to breathe, and this drive is influenced by various factors, including the oxygen and carbon dioxide levels in the blood, as well as the presence of respiratory drive-modifying stressors. The muscles of the chest and abdomen contract in a coordinated manner to produce the negative intrathoracic pressure required for inhalation and the positive intrathoracic pressure required for exhalation.

In summary, the respiratory system is a complex and vital system that is essential for maintaining life. It is made up of the lung, which is the gas-exchanging organ, and the pump that ventilates the lungs, which includes the chest wall, respiratory muscles, and central nervous system. Understanding the structure and function of the respiratory system is crucial for understanding how it maintains the balance of gas exchange in the body.