Respiratory System

Respiratory System Overview

  • Respiration: Involves the ventilation of lungs and the exchange of gases.

    • External Respiration: Exchange of gases between air and blood; between blood and tissue fluid.

    • Internal Respiration: Use of O2 in cellular metabolism.

Respiratory Tract Anatomy

  • Key Structures:

    • Nasal cavity

    • Nostril

    • Pharynx

    • Oral cavity

    • Trachea

    • Larynx

    • Carina of trachea

    • Right and left main bronchi

    • Right and left lungs

    • Diaphragm

Functions of the Respiratory System

  • Enables Speech and Vocalization

  • Sense of Smell: Facilitated by the nose.

  • Defense Mechanisms:

    • Cilia and mucus trap particles.

  • Acid-Base Balance: Regulates pH in the body.

  • Water Loss and Heat Elimination

  • Inactivation and Activation of Materials:

    • Inactivation of substances (e.g., Aspirin).

    • Activation of the angiotensin system (angiotensinogen to angiotensin II).

Components of the Nose

  • Structure: Comprised of bone and cartilage.

  • Functions:

    • Warms, cleanses, and humidifies inhaled air.

    • Detects odors.

    • Resonates to amplify voice.

Nasal Cavity and Mucosa

  • Mucosa Types:

    • Olfactory Mucosa: Roof of nasal cavity.

    • Respiratory Mucosa: Warming air and trapping debris through mucus, lysozyme, and cilia.

Upper Respiratory Tract Components

  • Sinuses (Frontal, Sphenoid)

  • Nasal conchae and meatuses (superior, middle, inferior)

  • Pharyngeal tonsil

  • Auditory tube

  • Uvula and tonsils

Pharynx Regions

  • Nasopharynx: Contains auditory tubes and pharyngeal tonsil.

  • Oropharynx: Contains palatine and lingual tonsils.

  • Laryngopharynx: Located below the oropharynx.

Larynx Structure and Function

  • Components:

    • Glottis: Opening between vocal cords.

    • Epiglottis: Directs food to esophagus.

    • Infant Larynx: Higher position aiding simultaneous breathing while swallowing.

  • Framework: Composed of cartilage layers including thyroid (Adam's apple) and arytenoid cartilage.

Vocal Cords and Their Action

  • Types of Vocal Cords:

    • Vestibular Folds: Close glottis during swallowing.

    • Vocal Cords: Produce sound with intrinsic and extrinsic muscles controlling function.

Trachea

  • Structure: A rigid tube about 4.5 inches long, supported by C-shaped cartilage rings.

  • Role: Adjusts airflow and is lined with ciliated epithelium for mucociliary clearance.

Bronchial Tree

  • Primary Bronchi: Branch into secondary bronchi.

  • Bronchioles: Lacks cartilage, more smooth muscle.

  • Alveoli: Where gas exchange occurs, connected through ducts and sacs.

Respiratory Zone

  • The conducting zone leads to the alveoli where external respiration occurs (gas exchange).

Alveolar Cells

  • Type 1 Alveolar Cells: Squamous epithelial cells facilitating diffusion.

  • Type 2 Alveolar Cells: Produce surfactant to prevent alveolar collapse.

  • Macrophages: Preserve lung health by eliminating pathogens.

Pleural Sac

  • Contains visceral and parietal layers and a fluid-filled cavity to reduce friction and maintain pressure gradient.

Pressure and Flow in Respiration

  • Atmospheric Pressure: Drives respiration; normal is 760 mmHg.

  • Pressure Gradients: Created in thoracic cavity during breathing movements.

Mechanisms of Ventilation

  • Inspiration: Involves the contraction of diaphragm and intercostal muscles, increasing thoracic cavity volume.

  • Expiration: Can be passive or forced, dependent on muscle contraction and volume changes.

Lung Volume Changes

  • Tidal Volume: Air exchanged in quiet breathing.

  • Vital Capacity: Maximum air exhaled after maximum inhalation.

Respiratory Capacities and Factors

  • Total lung capacity, forced expiratory volume, and factors affecting lung mechanics include age, body size, and health.

  • Disturbances: Include obstructive and restrictive disorders affecting airflow.

Neural Control of Respiration

  • Controlled by the medulla oblongata and pons, regulating respiratory rhythm based on bodily needs.

Gas Exchange Mechanisms

  • Simple diffusion of gases results in oxygen and carbon dioxide exchanges based on partial pressure gradients.

  • The efficiency correlates with surface area and membrane thickness.

Oxygen Transport and Utilization

  • Hemoglobin Binding: Transports O2 and CO2; influenced by partial pressure and physiological states (e.g., pH changes, temperature).

Lung Diseases and Their Impact

  • Lung diseases alter gas exchange capabilities, such as pneumonia and emphysema affecting surface area and membrane efficiency.

Abnormalities in Respiratory Physiology

  • Conditions like hypoxia or hyperoxia influence respiratory efficiency, requiring proper clinical management for symptoms.

Effects of Smoking on Health

  • Smoking is a primary cause of lung cancer leading to significant morbidity and mortality.

  • Common forms include squamous-cell carcinoma that originates in bronchial epithelium.