Ch 22 Respiratory system

Chapter 22: The Respiratory System

Introduction

• Breathing and Life: Represents the essence of life; breathing begins with the first inhalation of a newborn and culminates with the final gasp of a dying individual, highlighting its fundamental role in sustaining life.

• ATP Requirements: All physiological processes in the body require adenosine triphosphate (ATP), which necessitates oxygen for its synthesis in cellular respiration while producing carbon dioxide as a byproduct that must be expelled from the body.

• Respiratory System Function: Comprises a series of tubes and structures that deliver air to the lungs; it plays a crucial role in the diffusion of oxygen into the bloodstream and the removal of carbon dioxide, thus maintaining homeostasis.

• Cardiopulmonary System: The interplay between the respiratory and cardiovascular systems is vital for delivering oxygen and efficiently removing carbon dioxide through circulation, showcasing their integrated function.

• Acid-Base Balance: The respiratory system collaborates with the urinary system to maintain the body's acid-base balance, ensuring a stable internal environment essential for cellular function.

Anatomy of the Respiratory System

• Respiration Definition: Encompasses not only the mechanical aspect of lung ventilation but is also closely tied to cellular metabolism, where oxygen is utilized for energy production and carbon dioxide is produced as a waste product.

Functions of the Respiratory System:

• Gas Exchange: Facilitates the exchange of oxygen (O2) and carbon dioxide (CO2) between the blood and air within the alveoli, a process essential for aerobic metabolism.

• Communication: Integral to speech production, the respiratory system aids in vocalization through exhaled air passing through the larynx.

• Olfaction: The sense of smell is closely related to airflow and exposure to airborne chemicals, which the respiratory system plays a role in detecting.

• Acid-Base Balance: Maintains the pH level of body fluids by regulating the expulsion of carbon dioxide, which can influence blood acidity levels.

• Blood Pressure Regulation: The respiratory system assists in the synthesis of angiotensin II, a hormone involved in regulating blood pressure and fluid balance.

• Blood and Lymph Flow: Breathing creates negative pressure within the thoracic cavity, enhancing venous return and lymphatic flow, which is critical for circulation and immune response.

• Blood Filtration: The lungs play a role in filtering out small clots from the bloodstream, preventing potential emboli that could disrupt circulation.

• Abdominal Content Expulsion: Engages in aiding bodily functions such as urination, defecation, and childbirth through the Valsalva maneuver, which increases abdominal pressure.

Principal Organs of the Respiratory System

• Key Components: The primary elements include the nose, pharynx, larynx, trachea, bronchi, and lungs, each serving specific functions in the overall respiratory process.

• Alveoli: These microscopic air sacs are essential for gas exchange, providing a vast surface area (~70 m²) to facilitate the efficient transfer of oxygen into the blood and carbon dioxide out.

• Conducting Division: Comprises the respiratory passages from the nasal cavities through to the major bronchioles, designed for airflow rather than gas exchange.

• Respiratory Division: Specifically includes the alveoli and regions where gas exchange occurs, making it crucial for respiratory efficiency.

Upper and Lower Respiratory Tract

• Upper Respiratory Tract: Encompasses the structures from the nose to the larynx, responsible for air filtration, conditioning, and olfactory functions.

• Lower Respiratory Tract: Extends from the trachea down through the lungs, primarily responsible for gas exchange and ventilation.

The Nose

• Functions: The nose plays critical roles in warming, cleansing, and humidifying inhaled air, as well as detecting odors and amplifying the voice during speech.

• Structure: Extends from the external nostrils to the posterior nasal apertures; composed of both bone and hyaline cartilage (including nasal bones, maxillae, lateral cartilages, and alar cartilages).

• Nasal Fossae: Divided by a nasal septum that consists of bone and cartilage, allowing airflow to pass through the conchae for optimal conditioning of air.

• Respiratory Epithelium: Lines the nasal cavity and contributes significantly to airflow management, warmth, and moisture retention.

• Goblet Cells: Secrete mucus to trap inhaled particles and pathogens; the cilia propel this mucus towards the pharynx for clearance.

• Erectile Tissue: Swells periodically to redirect airflow between nostrils, promoting even nasal function and airflow.

The Trachea

• Structure: A rigid tube (~12 cm in length and 2.5 cm in diameter) supported by C-shaped cartilage rings, preventing collapse and ensuring a clear passageway for air.

• Inner Lining: Composed of ciliated pseudostratified columnar epithelium interspersed with mucus-secreting cells; effectively functions in debris removal through the mucociliary escalator mechanism.

• Branches: Divides into right and left main bronchi with distinct anatomical features influencing the likelihood of aspirated objects lodging in either lung.

The Lungs and Bronchial Tree

• Lung Anatomy: The lungs differ in size and shape; the right lung is shorter and consists of three lobes, whereas the left lung is taller, features two lobes, and has a cardiac impression accommodating the heart.

• Bronchial Tree: The main bronchus branches into lobar and segmental bronchi, progressively becoming smaller; all bronchi are lined with ciliated pseudostratified columnar epithelium to facilitate air passage and remove debris.

Alveoli

• Quantity: Each lung contains approximately 150 million alveoli, maximizing the surface area available for gas exchange and enhancing respiratory efficiency.

• Types of Alveolar Cells:

  • Type I Cells: Flat cells that facilitate rapid gas diffusion due to their thinness.

  • Type II Cells: Secretory cells that produce surfactant, a substance that reduces surface tension and prevents alveolar collapse during exhalation.

  • Macrophages: Immune cells stationed within the alveoli that clean dust and debris; dying cells are removed via the mucociliary escalator.

The Pleurae

• Visceral vs. Parietal Pleura: The visceral pleura intimately covers the lungs, while the parietal pleura adheres to the thoracic cavity walls; the pleural cavity contains serous fluid to minimize friction and assist in lung expansion during respiration.

Pulmonary Ventilation

• Breathing Mechanics: Comprised of two phases: inspiration (inhalation) and expiration (exhalation); driven by pressure differences between the lungs and the atmosphere, allowing for airflow.

• Diaphragm: The primary muscle involved in breathing, contracting during inspiration to enlarge the thoracic cavity.

• Intercostal Muscles: Play a supporting role in expanding and contracting the thoracic cage, further facilitating effective ventilation.

Neural Control of Breathing

• Brainstem Centers: The medulla oblongata and pons regulate the rhythm and coordination of breathing, responding to both voluntary commands and autonomic control.

• Chemoreceptors: Sensors located in the brain and major arteries that monitor blood pH and gas levels, allowing for dynamic adjustment of respiratory rates as metabolic demands change.

Gas Exchange and Transport

• Partial Pressure: The differential partial pressures of gases determine the efficiency of gas exchange; this is influenced by factors such as the composition of inspired air versus alveolar air.

• Transport Mechanisms: Oxygen is predominantly transported by binding to hemoglobin in red blood cells, while carbon dioxide is primarily carried in the form of bicarbonate ions dissolved in plasma.

Effects of Gases and Regulation

• Metabolic Needs Adjustment: The unloading of oxygen from hemoglobin is modulated by pH, temperature, and levels of 2,3-bisphosphoglycerate (BPG), which vary with tissue activity levels.

• pH Sensitivity: Central chemoreceptors are particularly responsive to changes in blood pH, regulating ventilation rates to maintain optimal acid-base balance.

Summary of Key Concepts

• Respiratory Dysfunction and Disorders: A comprehensive understanding of lung volume measurements and the distinction between restrictive and obstructive disorders is essential for effective clinical diagnosis and management.

• Role of External Factors: Environmental variables such as altitude and humidity can significantly impact respiratory function, posing challenges to ventilation and gas exchange efficiency.