Chapter 21: The Respiratory System

Overview

The respiratory system is essential for gas exchange, supplying oxygen to the body and removing carbon dioxide. It consists of anatomical structures that facilitate breathing and protect the respiratory mucosa.

Section 1: Anatomy of the Respiratory System

Learning Outcomes

• Identify the structures of the respiratory system and list their functions.

• Describe the roles of respiratory exchange surfaces and the structure of the larynx, trachea, and other conducting airways.

• Explain the general functions of the upper respiratory tract and describe its role in moistening, warming, and filtering air.

• Describe the structure and function of the lungs, including the bronchial tree and the pulmonary lobules.

Module 21.1: The Respiratory System Has Upper and Lower Respiratory Tracts with Different Functions

Division of the Respiratory System

• Upper respiratory tract: Nose, nasal cavity, paranasal sinuses, pharynx

• Lower respiratory tract: Larynx, trachea, bronchi, bronchioles, alveoli

The upper tract conditions air (filters, warms, humidifies), while the lower tract conducts air to gas exchange surfaces.

Functions of the Respiratory System

• Provides an extensive surface area for gas exchange between air and circulating blood

• Moves air to and from exchange surfaces of the lungs

• Protects respiratory surfaces from dehydration, temperature changes, and pathogens

• Produces sounds for communication

• Detects odors by olfactory receptors in the superior portions of the nasal cavity

Module 21.2: The Respiratory Defense System Protects the Respiratory Mucosa

Respiratory Defense System

• Mucous cells and mucous glands: Produce mucus that bathes exposed surfaces

• Cilia: Sweep mucus and trapped debris toward the pharynx (mucus escalator)

• Filtration: Nasal cavity removes large particles

• Alveolar macrophages: Engulf small particles that reach the lungs

Structure of the Respiratory Epithelium

• Epithelium changes along the tract: pseudostratified ciliated columnar in upper tract, stratified squamous in pharynx, simple squamous in alveoli

Module 21.3: The Upper Respiratory System

Structures of the Upper Respiratory System

• Nose: Primary passageway for air; contains nostrils (nares)

• Nasal cavity: Contains nasal septum, conchae, and meatuses; warms and humidifies air

• Paranasal sinuses: Frontal, ethmoid, sphenoid, maxillary; produce mucus and resonate sound

• Pharynx: Chamber shared by respiratory and digestive systems; divided into nasopharynx, oropharynx, laryngopharynx

Functions of the Nasal Cavity

• Extensive network of veins warms inhaled air

• Mucous moistens air and traps particles

• Air turbulence from conchae increases contact with mucosa

• Mouth breathing eliminates these benefits

Module 21.4: The Larynx Protects the Glottis That Produces Sounds

Structure of the Larynx

• Cartilages: Epiglottis, thyroid cartilage, cricoid cartilage

• Glottis: Opening through which air passes; contains vocal folds

• Vocal folds: Produce sound; vestibular folds prevent foreign objects from entering glottis

Sound Production

• Phonation: Vibration of vocal cords produces sound waves

• Articulation: Modification of sounds by tongue, teeth, lips

Table: Comparison of Upper and Lower Respiratory Tracts

Key Terms and Definitions

• Glottis: The opening between the vocal cords in the larynx

• Epiglottis: Cartilage that covers the glottis during swallowing

• Vestibular folds: Folds that protect the vocal cords and prevent foreign objects from entering the glottis

• Mucus escalator: Mechanism by which cilia move mucus and trapped particles out of the respiratory tract

Relevant Equations

While this section does not include specific equations, gas exchange in the alveoli is governed by principles such as partial pressure gradients:

• Partial Pressure Equation:

• Fick's Law of Diffusion:

Where D = diffusion coefficient, A = surface area, P1-P2 = partial pressure difference, T = thickness of membrane

Summary

• The respiratory system is divided into upper and lower tracts, each with specialized structures and functions.

• Defense mechanisms protect the respiratory mucosa from pathogens and debris.

• The larynx is crucial for sound production and airway protection.

• Understanding the anatomy and physiology of the respiratory system is essential for comprehending gas exchange and respiratory health.

Additional info: Some details, such as the specific names of paranasal sinuses and the structure of the respiratory epithelium, were expanded for completeness and academic context.