Anatomy & Physiology II: Respiratory System Study Notes

Respiratory System Overview

The respiratory system is responsible for the exchange of gases (oxygen and carbon dioxide) between the body and the environment. It consists of several anatomical structures that facilitate breathing, protect the airways, and ensure efficient gas exchange.

Nose/Nasal Cavity

• External Nares (nostrils): Openings to the nasal cavity that allow air entry.

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

• Olfactory Mucosa/Epithelium: Contains sensory receptors for smell.

• Olfactory Glands: Produce mucus for olfactory epithelium.

• Superior, Middle, Inferior Nasal Conchae: Bony projections that increase surface area and help warm, moisten, and filter air.

• Superior, Middle, Inferior Nasal Meatuses: Passages beneath each concha for airflow.

• Hard and Soft Palate: Separate the nasal cavity from the oral cavity.

Paranasal Sinuses

Air-filled spaces in the skull that lighten its weight and help warm and moisten inhaled air.

• Frontal Sinus

• Sphenoid Sinus

• Ethmoid Sinus

• Maxillary Sinus

Pharynx

• Nasopharynx: Upper part, behind the nasal cavity.

• Oropharynx: Middle part, behind the oral cavity.

• Laryngopharynx: Lower part, leads to the larynx and esophagus.

• Pharyngeal, Palatine, Lingual Tonsils: Lymphatic tissue for immune defense.

Larynx

The larynx (voice box) is involved in breathing, producing sound, and protecting the trachea against food aspiration.

• Thyroid Cartilage: Largest cartilage, forms the Adam's apple.

• Laryngeal Prominence: Anterior projection of the thyroid cartilage.

• Cricoid Cartilage: Ring-shaped cartilage below the thyroid cartilage.

• Epiglottis: Flap that covers the glottis during swallowing.

• Glottis: Opening between the vocal cords.

• Vocal Folds (True Vocal Cords): Produce sound.

• Vestibular Folds (False Vocal Cords): Do not produce sound; help close the larynx during swallowing.

• Cartilages: Arytenoid, Corniculate, Cuneiform (support vocal folds and laryngeal structure).

Alveoli

Alveoli are tiny air sacs in the lungs where gas exchange occurs.

• Type I Cell: Simple squamous cells for gas exchange.

• Type II Cell: Secrete surfactant to reduce surface tension.

• Alveolar Macrophage: Engulf debris and pathogens.

• Alveolar Sac: Cluster of alveoli.

Trachea

The trachea (windpipe) is a tube that connects the larynx to the bronchi, allowing air passage to the lungs.

• Tracheal Cartilages: C-shaped rings that keep the trachea open.

• Carina: Ridge at the base of the trachea where it splits into bronchi.

• Pseudostratified Ciliated Columnar Epithelium: Lines the trachea, moves mucus upward.

• Goblet Cells: Produce mucus.

• Submucosa: Connective tissue layer with glands.

Bronchi

The bronchi are airways that branch from the trachea into the lungs, further dividing into smaller bronchioles.

• Primary Bronchi: Main branches entering each lung.

• Secondary (Lobar) Bronchi: Branches to each lobe of the lung.

• Tertiary (Segmental) Bronchi: Further subdivisions.

• Bronchioles: Smallest airways, lead to alveoli.

• Respiratory Bronchioles: Begin gas exchange.

• Simple Cuboidal Epithelium: Lines smaller bronchioles.

• Smooth Muscle: Controls airway diameter.

Thoracic Cage

The thoracic cage protects the lungs and supports breathing.

• Costal Cartilages: Connect ribs to sternum.

• Intercostal Muscles: Assist with breathing movements.

• Diaphragm: Main muscle of respiration.

Lungs

The lungs are paired organs where gas exchange occurs. Each lung is divided into lobes and covered by pleura.

• Lung Tissue: Composed of alveoli, bronchi, and blood vessels.

• Fissures: Separate lung lobes (oblique, horizontal).

• Pleura: Double-layered membrane (visceral and parietal) surrounding each lung.

• Right Lung: Superior, middle, and inferior lobes.

• Left Lung: Superior and inferior lobes; contains cardiac notch.

Additional Respiratory Structures

• Brainstem (Pons, Medulla Oblongata): Controls the rate and depth of breathing.

• Diaphragm: Contracts to allow inhalation; relaxes for exhalation.

Example: Gas Exchange in Alveoli

Oxygen diffuses from alveolar air into pulmonary capillaries, while carbon dioxide diffuses from blood into alveoli to be exhaled.

Additional info: The respiratory system also plays a role in pH regulation, vocalization, and protection against pathogens through mucociliary clearance and immune cells.