The Respiratory System

Functions of the Respiratory System

The respiratory system is essential for gas exchange and maintaining homeostasis in the body. It consists of organs and structures that facilitate the movement of air and the exchange of gases between the atmosphere and the bloodstream.

• Gas Exchange: Provides a large surface area for the exchange of oxygen and carbon dioxide between air and circulating blood.

• Ventilation: Moves air into and out of the lungs to facilitate gas exchange.

• Mucous Secretion: Protects the respiratory surfaces from dehydration and invasion by pathogens.

• Sound Production: The larynx produces sounds for speech.

• Olfaction: The olfactory epithelium sends sensory information to the central nervous system for the sense of smell.

Organization of the Respiratory System

Anatomical Divisions

The respiratory system is organized into upper and lower tracts, each with specific structures and functions.

• Upper Respiratory Tract: Includes the nose, nasal cavity, paranasal sinuses, and pharynx.

• Lower Respiratory Tract: Includes the larynx, trachea, bronchi, bronchioles, and alveoli.

The system can also be divided functionally into conducting and respiratory portions:

• Conducting Portion: Nasal cavity to terminal bronchioles; responsible for filtering, warming, and humidifying air.

• Respiratory Portion: Respiratory bronchioles and alveoli; site of gas exchange.

Respiratory Epithelia

Structure and Function

The respiratory tract is lined by a specialized mucous membrane that varies by region.

• Pseudostratified Ciliated Columnar Epithelium: Lines most of the respiratory tract; contains goblet cells that secrete mucus to trap particles.

• Lamina Propria: Underlying layer of loose connective tissue supporting the epithelium.

Olfactory Epithelium: Located in the superior region of the nasal cavity, contains sensory receptors for smell.

Nose and Nasal Cavity

Structure and Regions

The nose and nasal cavity are the primary entry points for air and play a role in filtering, warming, and humidifying inhaled air.

• External Nares (Nostrils): Openings to the nasal cavity.

• Vestibule: Area just inside the nostrils lined with skin and coarse hairs.

• Nasal Septum: Divides the nasal cavity into left and right portions; composed of bone and cartilage.

• Superior, Middle, and Inferior Nasal Conchae: Bony projections that create turbulence in the airflow, aiding in warming, humidifying, and filtering air.

Functions of the Nasal Conchae

• Cause turbulent airflow to increase contact with mucous membranes.

• Warm and humidify incoming air.

• Remove airborne particles.

Paranasal Sinuses

Air-filled spaces within the bones of the skull that open into the nasal cavity. They lighten the skull, produce mucus, and contribute to voice resonance.

• Frontal sinus

• Ethmoid sinus

• Sphenoid sinus

• Maxillary sinus

Pharynx

Regions of the Pharynx

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

• Nasopharynx: Superior portion, posterior to the nasal cavity; lined with pseudostratified ciliated columnar epithelium.

• Oropharynx: Middle portion, posterior to the oral cavity; lined with stratified squamous epithelium.

• Laryngopharynx: Inferior portion, posterior to the larynx; also lined with stratified squamous epithelium.

Larynx

Structure and Cartilages

The larynx is a cartilaginous structure that connects the pharynx to the trachea and houses the vocal cords.

• Epiglottis: Elastic cartilage that covers the laryngeal opening during swallowing to prevent food from entering the airway.

• Thyroid Cartilage: Largest laryngeal cartilage; forms the laryngeal prominence (Adam's apple); composed of hyaline cartilage.

• Cricoid Cartilage: Only laryngeal cartilage that forms a complete ring; provides support and attachment for muscles and ligaments.

• Other Cartilages: Arytenoid, corniculate, and cuneiform cartilages are involved in the movement and function of the vocal cords.

Functions of the Larynx

• Keeps the airway open via cartilaginous support.

• Produces sound for speech (phonation).

• Prevents food and liquids from entering the lower respiratory tract during swallowing.

Summary Table: Major Cartilages of the Larynx

Key Terms and Definitions

• Olfactory Epithelium: Specialized tissue involved in smell, located in the superior nasal cavity.

• Pseudostratified Ciliated Columnar Epithelium: Type of epithelial tissue with cilia and goblet cells, lines most of the respiratory tract.

• Laryngeal Prominence: The protrusion of the thyroid cartilage, commonly known as the Adam's apple.

• Vocal Folds: Also known as vocal cords, these are mucosal folds that vibrate to produce sound.

Additional info:

• The notes provide a foundational overview of the upper respiratory tract, focusing on structure, function, and histology relevant to introductory Anatomy & Physiology courses.

• Further study should include the lower respiratory tract, mechanisms of breathing, and gas exchange at the alveolar level.