Introduction to the Respiratory System

Overview of the Respiratory Tract

The respiratory system is responsible for the exchange of gases essential for life. It consists of a series of structures that conduct air into and out of the lungs, where gas exchange occurs.

• Nose: Entry point for air.

• Pharynx: Muscular tube connecting the nasal cavity to the larynx.

• Larynx: Voice box; passageway for air and sound production.

• Trachea: Windpipe; conducts air to the bronchi.

• Bronchi and Bronchioles: Branching airways leading to the alveoli.

• Alveoli: Air sacs where gas exchange occurs.

• Lungs: Main organs of respiration.

Processes of Respiration

• Ventilation: Movement of air in (inspiration) and out (expiration) of the lungs.

• External Respiration: Exchange of gases between alveoli and blood.

• Transport: Movement of gases in the blood between lungs and tissues.

• Internal Respiration: Exchange of gases between blood and body tissues.

Functions of the Respiratory System:

• Gas exchange (O2 and CO2)

• Regulation of blood pH

• Protection (cilia, mucus, tonsils)

• Voice production (vocal cords)

• Olfaction (smell receptors)

Medical Terminology: Word Analysis

Root Elements and Terms

• Pulmon-: Lung (e.g., pulmonary)

• Spir-: To breathe (e.g., spirometry)

Upper Respiratory Tract

Structure and Function of the Nose

The nose serves as the main passageway for air entering the respiratory system. It filters, moistens, and warms incoming air and houses olfactory receptors for smell.

• Nares: External openings of the nose.

• Septum: Divides the nasal cavity into right and left halves.

• Palate: Hard and soft palate separate the nasal and oral cavities.

• Conchae and Meatus: Increase surface area for air filtration and humidification.

Disorders of the Nose

• Upper Respiratory Infection (URI): Common viral infection affecting the nose and throat.

• Rhinitis (Coryza): Acute inflammation of the nasal mucosa, usually viral.

• Allergic Rhinitis: Allergic reaction causing clear, watery nasal discharge.

• Sinusitis: Inflammation of the paranasal sinuses.

• Deviated Nasal Septum: Displacement of the septum to one side.

• Epistaxis: Nosebleed, often from the nasal septum.

• Nasal Polyps: Benign mucosal growths in the nasal cavity or sinuses.

Pharynx: Structure and Function

The pharynx, or throat, is a muscular tube that serves as a passageway for both air and food. It is divided into three regions:

• Nasopharynx: Posterior to the nasal cavity.

• Oropharynx: Posterior to the oral cavity.

• Laryngopharynx: Posterior to the larynx; leads to the esophagus and larynx.

• Tonsils: Lymphatic tissue (palatine, pharyngeal/adenoid, and lingual) that helps protect against pathogens.

• Uvula: Extension of the soft palate.

Disorders of the Pharynx

• Snoring: Sound produced by vibration of soft tissues during sleep.

• Obstructive Sleep Apnea (OSA): Repeated episodes of airway obstruction during sleep, causing hypoxia.

• Apnea: Complete cessation of breathing.

• Hypoxia: Low oxygen levels in tissues.

• Pharyngitis: Inflammation of the pharynx.

• Tonsillitis: Inflammation of the tonsils, often viral.

• Nasopharyngeal Carcinoma: Cancer of the nasopharynx.

Medical Terminology: Adjective Forms

• Pharynx → Pharyngeal: Pertaining to the pharynx

• Nasopharynx → Nasopharyngeal: Pertaining to the nasopharynx

• Oropharynx → Oropharyngeal: Pertaining to the oropharynx

• Laryngopharynx → Laryngopharyngeal: Pertaining to the laryngopharynx

Larynx: Structure and Function

The larynx, or voice box, is a cartilaginous structure involved in sound production and maintaining an open airway.

• Unpaired Cartilages: Thyroid (Adam's apple), cricoid, epiglottis

• Paired Cartilages: Arytenoid, corniculate, cuneiform

• Vocal Cords: True vocal folds for sound production

• Vestibular Folds: False vocal cords

Major Roles:

• Maintaining an open airway

• Producing sound

Disorders of the Larynx

• Laryngitis: Inflammation of the laryngeal mucosa

• Epiglottitis: Inflammation of the epiglottis, common in young children

• Laryngotracheobronchitis (Croup): Viral inflammation and obstruction of the upper airway in young children

• Papilloma/Polyps: Benign tumors due to overuse or irritation

Lower Respiratory Tract

Structure and Function

• Trachea: Windpipe; supported by C-shaped cartilage rings

• Lungs: Right lung (3 lobes), left lung (2 lobes)

• Tracheobronchial Tree: Branching system of airways

• Bronchioles and Alveoli: Smallest airways and air sacs for gas exchange

• Pleurae: Double-layered serous membrane covering the lungs

Bronchioles, Alveoli, and the Respiratory Membrane

• Bronchioles: Smallest conducting airways

• Terminal Bronchioles: End of conducting zone

• Alveoli: Site of gas exchange

• Respiratory Membrane: Thin barrier (0.5 µm) for gas exchange; consists of alveolar epithelium, fused basement membranes, and capillary endothelium

Function: Oxygen diffuses from alveoli to blood; carbon dioxide diffuses from blood to alveoli.

Surfactant

• Definition: Lipoprotein secreted by type II alveolar cells

• Function: Reduces surface tension, prevents alveolar collapse, aids lung inflation

• Clinical Relevance: Deficiency in premature infants causes Infant Respiratory Distress Syndrome (IRDS); damage can lead to breathing difficulties

Tracheobronchial Tree Pathway

• Nose → Pharynx → Larynx → Trachea → Primary Bronchi → Secondary Bronchi → Tertiary Bronchi → Bronchioles → Alveoli

• Each alveolus is surrounded by a pulmonary capillary network for gas exchange.

Lungs and Pleura

• Right Lung: Three lobes

• Left Lung: Two lobes

• Pleura: Double-layered membrane (visceral and parietal)

• Pleural Cavity: Space between pleural layers, filled with pleural fluid

Disorders of the Respiratory System

Common Symptoms and Signs

• Cough: Reflex to clear irritants; hemoptysis is coughing up blood

• Dyspnea: Shortness of breath

• Cyanosis: Bluish discoloration due to unoxygenated hemoglobin

• Changes in Breathing Rate:

  • Eupnea: Normal breathing (10–15 breaths/min in adults)

  • Tachypnea: Rapid breathing

  • Hyperpnea: Deep, rapid breathing

  • Bradypnea: Slow breathing

Major Respiratory Disorders

• Asthma: Recurrent bronchial obstruction, bronchoconstriction, mucus hypersecretion, airway inflammation

• Hypercapnia: Excess carbon dioxide in the blood

• Chronic Bronchitis: Long-term airway inflammation, excess mucus, cilia destruction; often due to smoking

• Acute Bronchitis: Short-term inflammation, usually viral or bacterial; resolves without lasting damage

• COPD (Chronic Obstructive Pulmonary Disease): Group of diseases (mainly chronic bronchitis and emphysema) causing long-term airflow limitation

• Emphysema: Destruction of alveolar walls, reducing gas exchange surface area

• Cystic Fibrosis (CF): Genetic disorder causing thick, sticky mucus in lungs and digestive tract

• Infant Respiratory Distress Syndrome (IRDS): Premature infants lack surfactant, leading to breathing difficulties

• Pleurisy (Pleuritis): Inflammation of the pleura, often due to infection or other diseases

• Pneumothorax: Air in the pleural space causing lung collapse

• Pneumonia: Infection of the lungs, alveoli fill with fluid or pus, impairing gas exchange

Summary Table: Key Respiratory Disorders

Additional info: This guide expands on the provided notes with definitions, clinical context, and a summary table for clarity and exam preparation.