Respiratory System Anatomy: Route of Air Flow

Study Notes

Respiratory System Anatomy

Route of Air Flow

Inspiratory and expiratory pathways pass through: nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, and alveoli located in the lungs.
Nasal cavity: warms, humidifies, and filters air.
Pharynx: has three areas (nasopharynx, oropharynx, and laryngopharynx) and serves as a passage for air and food/liquid.

Functions of Organs

Larynx: contains cartilage and other connective tissue, involved in breathing, producing sound (vocal cords), and protects the trachea against food and liquid aspiration.
Trachea: contains C-shaped cartilage rings and a small area of smooth muscle (dorsal side).
Bronchi and bronchioles: conduct air to and from the respiratory zone structures.
Respiratory zone structures: respiratory bronchioles, alveoli involved in gas exchange (external respiration).
Lungs: composed of alveoli, elastic tissue, and airways.

Alveolus and Respiratory Membrane

Alveolus: site of external respiration.
Alveolar epithelium: mostly simple squamous for gas exchange, also has simple cuboidal cells that secrete lung surfactant.
Macrophages (innate immune system) are present in alveoli.
Respiratory membrane: consists of alveolar epithelium, capillary epithelium (endothelium), and fused basement membranes.

Changes in Airway Structure

As you progress closer to the alveoli:
- Mucociliary escalator (presence of mucous and cilia) is present.
- Cartilage is present in larynx to small bronchi (not in bronchioles).
- Smooth muscle is present in pharynx, trachea (dorsal side), and bronchioles, becoming more prominent in smaller airways.

Protective Mechanisms of the Respiratory System

Mucous production: traps and kills bacteria.
Cilia: works with mucous to remove debris (mucociliary escalator).
Tonsils: trap and remove pathogens.
Epiglottis: prevents food and liquid from entering the trachea.
Cartilage: keeps airways open.
Lung surfactant: reduces surface tension in the alveoli.
Macrophages: part of the innate immune system.

Pulmonary Ventilation

Volume Changes and Pressure Changes

As volume increases, pressure decreases; as volume decreases, pressure increases.
Total pressure is the sum of all partial pressures (e.g., pO2 and pN2).

Sequence of Events in Pulmonary Ventilation

Brainstem: sends signals to spinal nerves.
Spinal nerves: stimulate diaphragm and intercostal muscles.
Diaphragm and intercostal muscles: contract and relax, causing changes in air pressure.
Pressure gradients: develop between the thoracic cavity and the atmosphere.
Airflow: occurs due to pressure gradients.

Respiratory Muscles and Lung Elasticity

Diaphragm and intercostal muscles: primary muscles involved in inspiration and expiration.
Additional muscles (e.g., sternocleidomastoid, scalenes, internal intercostals, and abdominal-wall muscles) are recruited for forced inspiration and expiration.
Lung elasticity: plays a crucial role in producing volume changes that cause air to flow into and out of the lungs.

Description

Learn about the path of air during inhalation and exhalation, including the functions of the nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, alveoli, and lungs. Identify and label each organ on a diagram. Test your knowledge of the respiratory system!