The Respiratory System

Introduction

The respiratory system is essential for supplying the body with oxygen (O2) and removing carbon dioxide (CO2). It works closely with the circulatory system to maintain homeostasis and support cellular metabolism.

• Main Function: Supply body with O2 and remove CO2.

• Processes of Respiration:

  1. Pulmonary ventilation: Movement of air into and out of the lungs.

  2. External respiration: Exchange of gases between air in the lungs and blood.

  3. Transport of respiratory gases: Movement of O2 and CO2 in the blood.

  4. Internal respiration: Exchange of gases between blood and tissues.

Respiratory Anatomy Questions

• What are the major organs of the respiratory system?

• What are the four processes of respiration and their functions?

• How do the respiratory and circulatory systems work together?

• What is the structural plan of the respiratory system?

• What is the function of the mucosa in the respiratory tract?

• What are the functions of the nose and nasal cavity?

• What are paranasal sinuses and their functions?

• What are the regions of the pharynx and their roles?

Structural Plan of the Respiratory System

Overview

The respiratory system resembles an inverted hollow tree, with the trachea as the trunk and the bronchi and bronchioles as branches. The alveoli are like leaves where gas exchange occurs.

• Major Organs: Nose, nasal cavity, pharynx, larynx, trachea, bronchi, lungs, alveoli.

• Respiratory Tracts: Upper (nose, nasal cavity, pharynx) and lower (larynx, trachea, bronchi, lungs).

Oh the Mucosa!

• Mucosal membrane: Lines the airways, producing about 125 mL of mucus daily.

• Function: Traps dust, bacteria, and other particles; moistens and protects the respiratory tract.

Nose and Nasal Cavity

Structure and Function

• Nasal septum: Separates the interior of the nose into two cavities.

• Functions:

  • Warms, moistens, and filters inhaled air.

  • Contains olfactory receptors for smell.

  • Provides a resonating chamber for speech.

• Clinical Note: Nasal polyps are noncancerous growths associated with chronic inflammation.

Paranasal Sinuses

• Located in frontal, sphenoid, ethmoid, and maxillary bones.

• Lighten the skull and help warm and moisten air.

• Drain into the nasal cavity.

Pharynx

Structure and Regions

• Pharynx: Muscular tube that serves as a passageway for air and food.

• Regions:

  • Nasopharynx: Superior region, behind the nasal cavity; contains openings for auditory tubes.

  • Oropharynx: Middle region, behind the oral cavity; passageway for food and air.

  • Laryngopharynx: Inferior region; leads to the larynx and esophagus.

Functions of the Respiratory System

Summary of Key Functions

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

• Moves air to and from the exchange surfaces of the lungs.

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

• Produces sounds for communication.

• Facilitates olfaction (sense of smell).

Table: Comparison of Respiratory Tracts

Example: Airflow Pathway

• Air enters through the nose → passes through the nasal cavity → pharynx → larynx → trachea → bronchi → bronchioles → alveoli (site of gas exchange).

Additional info:

• The mucociliary escalator is a mechanism where cilia move mucus upward toward the pharynx for removal, helping to keep the respiratory tract clear of debris and pathogens.

• Respiratory mucosa contains lysozyme and defensins, which provide antimicrobial defense.