🤾🏻♂️Human Physiology Engineering Unit 7 – Respiratory System
The respiratory system is a complex network of organs and tissues that enable gas exchange between our bodies and the environment. It delivers oxygen to cells and removes carbon dioxide waste, working closely with the cardiovascular system to maintain vital functions.
From the nose to the lungs, each part of the respiratory tract plays a crucial role in breathing mechanics and gas exchange. Understanding this system is essential for diagnosing and treating respiratory disorders, as well as developing innovative medical technologies.
Consists of organs and tissues that facilitate gas exchange between the environment and the bloodstream
Primary function is to deliver oxygen to the body's cells and remove carbon dioxide waste
Includes the upper respiratory tract (nose, pharynx, and larynx) and lower respiratory tract (trachea, bronchi, and lungs)
Closely interacts with the cardiovascular system to ensure efficient gas transport throughout the body
Plays a vital role in maintaining the body's acid-base balance by regulating carbon dioxide levels
Facilitates other functions such as speech production, olfaction (sense of smell), and protection against inhaled particles
Responds to changes in metabolic demand by adjusting ventilation rate and depth
Anatomy of the Respiratory Tract
Nose and nasal cavity
Serve as the entry point for inhaled air
Humidify, filter, and warm the incoming air
Contain olfactory receptors for the sense of smell
Pharynx (throat)
Connects the nasal and oral cavities to the larynx and esophagus
Plays a role in both the respiratory and digestive systems
Larynx (voice box)
Houses the vocal cords, which vibrate to produce speech sounds
Acts as a valve to protect the lower respiratory tract from food and liquid aspiration
Trachea (windpipe)
Tubular structure that connects the larynx to the bronchi
Lined with ciliated epithelium and mucus-secreting cells to trap and remove inhaled particles
Bronchi and bronchioles
Branching airways that progressively decrease in size as they extend into the lungs
Conduct air to the alveoli, the site of gas exchange
Lungs
Paired, spongy organs located in the thoracic cavity
Contain millions of alveoli, which are surrounded by capillaries for efficient gas exchange
Right lung is slightly larger than the left lung due to the position of the heart
Mechanics of Breathing
Breathing involves the coordinated movement of the diaphragm, intercostal muscles, and lungs
Inhalation (inspiration)
Diaphragm contracts and flattens, increasing the vertical dimension of the thoracic cavity
External intercostal muscles contract, lifting the ribs and expanding the thoracic cavity
Increased thoracic volume decreases intrapulmonary pressure, causing air to flow into the lungs
Exhalation (expiration)
Diaphragm and external intercostal muscles relax, decreasing the size of the thoracic cavity
Decreased thoracic volume increases intrapulmonary pressure, forcing air out of the lungs
Exhalation is typically passive during quiet breathing but can be active during forceful expiration
Lung volumes and capacities
Tidal volume (TV): volume of air inhaled or exhaled during normal breathing
Inspiratory reserve volume (IRV): additional air that can be inhaled beyond tidal volume
Expiratory reserve volume (ERV): additional air that can be exhaled beyond tidal volume
Residual volume (RV): air remaining in the lungs after maximal exhalation
Total lung capacity (TLC): maximum volume of air the lungs can hold, equal to the sum of all lung volumes
Gas Exchange and Transport
Gas exchange occurs primarily in the alveoli, where the air and blood are separated by a thin, permeable membrane
Oxygen diffuses from the alveoli into the blood, while carbon dioxide diffuses from the blood into the alveoli
Factors affecting gas exchange
Partial pressure gradients of oxygen and carbon dioxide between the alveoli and blood
Surface area of the alveolar-capillary membrane
Thickness of the alveolar-capillary membrane
Ventilation-perfusion (V/Q) matching, ensuring adequate airflow and blood flow to each alveolus
Oxygen transport
Most oxygen is bound to hemoglobin in red blood cells, forming oxyhemoglobin
A small amount of oxygen is dissolved in the blood plasma
Carbon dioxide transport
Dissolved in blood plasma as bicarbonate ions (HCO3-)
Bound to hemoglobin as carbaminohemoglobin
Dissolved in blood plasma as dissolved carbon dioxide
Respiratory Control and Regulation
Breathing is controlled by the respiratory center in the brainstem, which consists of the medulla oblongata and pons
Medullary respiratory center
Dorsal respiratory group (DRG) generates the basic rhythm of breathing
Ventral respiratory group (VRG) influences the pattern and depth of breathing
Pontine respiratory centers
Pneumotaxic center modulates the duration of inspiration and respiratory rate
Apneustic center promotes prolonged inspiration
Chemoreceptors detect changes in blood gas levels and pH
Central chemoreceptors in the medulla respond to changes in cerebrospinal fluid pH
Peripheral chemoreceptors (carotid and aortic bodies) respond to changes in arterial blood pH, oxygen, and carbon dioxide levels
Mechanoreceptors provide feedback on lung volume and airway resistance
Stretch receptors in the lung tissue detect lung inflation and prevent overinflation
Irritant receptors in the airways respond to noxious stimuli and trigger coughing or bronchospasm
Voluntary control of breathing
Cortical influences can override the automatic control of breathing for short periods (e.g., holding breath, speaking, singing)
Common Respiratory Disorders
Asthma
Chronic inflammatory disorder characterized by airway hyperresponsiveness and reversible airflow obstruction
Triggers include allergens, irritants, and exercise
Symptoms: wheezing, coughing, chest tightness, and shortness of breath
Chronic obstructive pulmonary disease (COPD)
Progressive, irreversible airflow limitation due to chronic bronchitis and/or emphysema
Main risk factor is long-term exposure to tobacco smoke
Symptoms: dyspnea, chronic cough, and sputum production
Pneumonia
Infection of the lung tissue caused by bacteria, viruses, or fungi
Symptoms: fever, chills, cough, chest pain, and difficulty breathing
Can lead to consolidation of lung tissue and impaired gas exchange
Sleep apnea
Repeated episodes of partial or complete upper airway obstruction during sleep
Types: obstructive sleep apnea (OSA) and central sleep apnea (CSA)
Symptoms: loud snoring, gasping during sleep, daytime sleepiness, and morning headaches
Lung cancer
Malignant growth in the lung tissue, often caused by long-term exposure to carcinogens (e.g., tobacco smoke, radon, asbestos)
Symptoms: persistent cough, chest pain, weight loss, and hemoptysis (coughing up blood)
Treatment options include surgery, chemotherapy, radiation therapy, and targeted therapy
Respiratory System Engineering Applications
Mechanical ventilation
Devices that provide artificial ventilation for patients with respiratory failure
Types: invasive (endotracheal or tracheostomy tube) and non-invasive (face mask or nasal interface)
Modes: volume-controlled, pressure-controlled, and pressure support ventilation
Extracorporeal membrane oxygenation (ECMO)
Technique that provides prolonged cardiac and respiratory support for patients with severe cardiopulmonary failure
Blood is drained from the patient, oxygenated through an artificial lung, and returned to the patient's circulation
Pulmonary function testing
Devices and techniques used to assess lung function and diagnose respiratory disorders
Spirometry measures lung volumes and flow rates during forced breathing maneuvers
Plethysmography measures total lung capacity and airway resistance
Diffusing capacity of the lung for carbon monoxide (DLCO) assesses the efficiency of gas exchange
Aerosol drug delivery systems
Devices that deliver medication directly to the lungs in the form of an aerosol
Examples: metered-dose inhalers (MDIs), dry powder inhalers (DPIs), and nebulizers
Advantages include targeted delivery, rapid onset of action, and reduced systemic side effects
Artificial lung development
Research aimed at creating functional, bioartificial lungs for long-term respiratory support or transplantation
Approaches include decellularized lung scaffolds, 3D bioprinting, and microfluidic devices
Challenges include replicating the complex structure and function of the native lung and preventing immune rejection
Key Takeaways and Review
The respiratory system is responsible for gas exchange between the environment and the bloodstream, delivering oxygen to cells and removing carbon dioxide waste
The respiratory tract consists of the upper (nose, pharynx, and larynx) and lower (trachea, bronchi, and lungs) portions, each with specific functions
Breathing mechanics involve the coordinated movement of the diaphragm, intercostal muscles, and lungs, resulting in changes in intrapulmonary pressure and airflow
Gas exchange occurs in the alveoli, where oxygen and carbon dioxide diffuse across the alveolar-capillary membrane based on partial pressure gradients
Respiratory control is primarily regulated by the medullary and pontine respiratory centers in the brainstem, with input from chemoreceptors and mechanoreceptors
Common respiratory disorders include asthma, COPD, pneumonia, sleep apnea, and lung cancer, each with specific pathophysiology and treatment approaches
Respiratory system engineering applications encompass mechanical ventilation, ECMO, pulmonary function testing, aerosol drug delivery systems, and artificial lung development
Understanding the structure, function, and regulation of the respiratory system is crucial for diagnosing and treating respiratory disorders and developing innovative engineering solutions