Components of the Respiratory System

Overview of the Respiratory System

The respiratory system is essential for gas exchange, supplying oxygen to the body and removing carbon dioxide. It is divided into anatomical and functional regions.

• Upper respiratory system: Includes the nose, nasal cavity, paranasal sinuses, and pharynx.

• Lower respiratory system: Includes the larynx, trachea, bronchi, bronchioles, and alveoli.

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.

• Facilitates olfactory sensation.

Structural Organization

Anatomy of the Respiratory Tract

The respiratory tract is divided 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 Mucosa

The respiratory mucosa lines the conducting portion of the respiratory system and consists of:

• Epithelium: Varies along the tract (see table below).

• Lamina propria: Underlying layer of areolar tissue supporting the epithelium.

Types of Respiratory Epithelium

Different regions of the respiratory tract are lined by specific epithelial types, adapted for their functions.

The Respiratory Defense System

The respiratory defense system protects delicate exchange surfaces from pathogens and debris.

• Mucous cells and glands: Produce mucus to trap particles.

• Cilia: Sweep mucus toward the pharynx (mucociliary escalator).

• Alveolar macrophages: Engulf small particles that reach the alveoli.

Upper Respiratory Tract

The Nose and Nasal Cavity

The nose is the primary entryway for air into the respiratory system.

• Nasal vestibule: Area inside the nostrils; contains coarse hairs for filtration.

• Nasal conchae: Bony projections that increase surface area, enhancing air turbulence and contact with mucosa.

• Nasal mucosa: Warms and humidifies incoming air; breathing through the mouth bypasses this step.

The Palates

• Hard palate: Forms the floor of the nasal cavity and separates it from the oral cavity.

• Soft palate: Extends posterior to the hard palate; separates nasopharynx from lower pharynx.

The Pharynx

The pharynx is a muscular chamber shared by the digestive and respiratory systems, divided into three regions:

• Nasopharynx: Superior portion, connected to nasal cavity.

• Oropharynx: Middle portion, posterior to oral cavity.

• Laryngopharynx: Inferior portion, extends from hyoid bone to entrance of larynx and esophagus.

The Larynx

Cartilages of the Larynx

The larynx contains three large, unpaired cartilages:

• Thyroid cartilage: Largest, forms the anterior and lateral walls (Adam's apple).

• Cricoid cartilage: Forms the posterior portion; provides support.

• Epiglottis: Elastic cartilage that covers the glottis during swallowing.

Ligaments of the Larynx

• Vestibular ligaments: Support the vestibular folds (false vocal cords).

• Vocal ligaments: Support the vocal folds (true vocal cords), which produce sound.

Sound Production

• Sound is produced by vibration of the vocal folds as air passes through the glottis.

• Pitch is determined by the length and tension of the vocal folds.

• Speech involves further modification by the tongue, lips, and other structures.

The Trachea and Bronchial Tree

The Trachea

The trachea, or windpipe, extends from the cricoid cartilage into the mediastinum, where it branches into the right and left primary bronchi.

• Tracheal cartilages: 15-20 C-shaped rings that keep the airway open.

• Trachealis muscle: Connects the ends of each cartilage ring posteriorly; allows for expansion of the esophagus during swallowing.

The Primary Bronchi

• Right and left primary bronchi branch from the trachea at the carina.

• Right bronchus is wider, shorter, and descends at a steeper angle than the left.

The Bronchial Tree

• Primary bronchi branch into secondary (lobar) bronchi, then into tertiary (segmental) bronchi.

• Each tertiary bronchus supplies a single bronchopulmonary segment.

• Bronchioles are smaller branches lacking cartilage, with walls dominated by smooth muscle.

• Terminal bronchioles mark the end of the conducting zone.

The Lungs

Lung Anatomy

• Right lung: Has three lobes (superior, middle, inferior); is wider and displaced upward by the liver.

• Left lung: Has two lobes (superior, inferior); is longer and displaced leftward by the heart, forming the cardiac notch.

Bronchopulmonary Segments

• Right lung: 10 segments

• Left lung: 8 or 9 segments

• Each segment is supplied by its own tertiary bronchus and branch of the pulmonary artery.

Pleural Cavities and Membranes

• Each lung is surrounded by a pleural cavity lined by a double-layered pleural membrane.

• Parietal pleura: Lines the thoracic wall.

• Visceral pleura: Covers the lung surface.

• Pleural fluid reduces friction and provides surface tension for lung expansion.

Autonomic Control of Airways

• Bronchodilation: Dilation of bronchial airways, caused by sympathetic activation; increases airflow.

• Bronchoconstriction: Constriction of bronchi, caused by parasympathetic activation or allergic reactions; reduces airflow.

Pulmonary Lobules

• Smallest compartments of the lung, separated by connective tissue partitions (trabeculae).

• Each lobule contains branches of a terminal bronchiole, pulmonary arteriole, and venule, and is supplied by lymphatics and nerves.

Summary Table: Major Structures of the Respiratory System

Additional info: The notes above expand on the original slides by providing definitions, context, and organization for easier study. The tables summarize key structural and functional differences in the respiratory tract.