Respiratory System Overview

Respiratory System Overview

• The respiratory system facilitates gas exchange, bringing in oxygen and releasing carbon dioxide.
• It involves several zones: conducting (upper respiratory) and respiratory (lungs).
• The conducting zone filters, warms, and moistens inhaled air.
• The respiratory zone facilitates gas exchange within the lungs.

Conducting Zone

• The conducting zone consists of tubes, the trachea & bronchi.
• Primarily composed of ciliated pseudostratified columnar epithelium.
• Goblet cells secrete mucus to trap dust and debris.
• Mucus is propelled out of the lungs by cilia.
• Hyaline cartilage maintains airway patency (keeps the airways open).
• Bronchioles have less cartilage and more smooth muscle than larger airways.

Respiratory Zone

• This zone includes bronchioles, alveolar sacs, and alveoli.
• The alveoli are the primary site of gas exchange.
• They're cup-shaped to increase surface area.
• Surrounded by a capillary network.
• Type I cells are specialized for gas exchange.
• Type II cells secrete surfactant to reduce surface tension and prevent alveolar collapse.
• Alveolar macrophages remove debris.
• The respiratory membrane is a thin membrane that separates the alveoli from capillaries, crucial for gas exchange. Consisting of 4 layers.

Pulmonary Ventilation (Breathing)

• Boyle's Law: Pressure and volume are inversely related.
• Inhalation: Chest cavity expands, decreasing pressure so air enters. This involves the contraction of the diaphragm and external intercostal muscles.
• Exhalation: Relaxation of the muscles allows the elastic recoil of the lungs and thoracic cavity, increasing pressure and pushing air out.
• Surfactant reduces alveolar surface tension, preventing collapse during exhalation.

Factors Affecting Breathing

• Surface tension: Surfactant reduces alveolar surface tension.
• Compliance: Lung and chest wall elasticity and surface tension affect the ease of expansion. Various diseases can reduce lung compliance.
• Airway resistance: Airway size affects resistance. Certain conditions like asthma or COPD increase airway resistance.

Breathing Patterns

• Eupnea: Normal breathing
• Apnea: Cessation/stopping of breathing
• Dyspnea: Labored breathing
• Tachypnea: Rapid breathing
• Diaphragmatic and costal breathing: Different patterns of breathing.

Gas Exchange

• Dalton's Law: Each gas in a mixture exerts its partial pressure.
• Henry's Law: Higher pressure equals more gas dissolved.
• External Respiration: Gas diffuses between alveoli and blood.
• Internal Respiration: Gases diffuse from blood to tissues.

Oxygen Transport

• Oxygen is poorly soluble in water.
• Hemoglobin (Hb) in red blood cells carries most oxygen.
• Each Hb molecule can carry four oxygen molecules.
• Factors affecting oxygen binding to Hb include pH, partial pressure of CO2, temperature, and 2,3-biphosphoglycerate (BPG). Low pH, high CO2, high temperature, and increased BPG decrease oxygen binding.
• Anemia is a condition where the body's capacity to carry oxygen is decreased.

Carbon Dioxide Transport

• CO2 is transported in three ways: Dissolved in plasma, bound to hemoglobin, and as bicarbonate ions.
• The conversion to bicarbonate involves a reaction that releases hydrogen ions; the chloride shift maintains ion balance.

Control of Breathing

• The respiratory centers in the medulla oblongata and pons control breathing rhythm.
• Chemical regulators (central and peripheral chemoreceptors) and other factors (stretch receptors, emotions, pain) regulate breathing.
• Ventilation is regulated via a negative feedback loop.

Hypoxia (Inadequate Tissue Oxygenation)

• Various types of hypoxia (low tissue oxygen): Hypoxic, anemic, ischemic, and histotoxic. Underlying mechanisms are different for each type.

Exercise and Respiration

• Exercise increases respiratory rate and heart rate to meet the increased oxygen demand of muscles.

Aging and Smoking

• Aging leads to reduced lung elasticity and vital capacity.
• Smoking damages the respiratory system, increasing susceptibility to diseases like emphysema and chronic bronchitis.

Respiratory Disorders

• Upper Respiratory Diseases: Coryza (common cold) and influenza (flu).
• Obstructive and Restrictive Diseases: Examples include asthma, COPD (emphysema, chronic bronchitis), lung cancer, cystic fibrosis, pneumonia, and tuberculosis.
• Symptoms and Characteristics of each disorder are described in a general/broad sense.