Respiratory System Anatomy: Nose, Larynx, Lungs & Bronchi

Posted on Mar 16, 2025 in Biology

Respiratory System Anatomy

Area of Conduct

Formed by a series of interconnected cavities and tubes: nose, pharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles. These structures conduct air into the lungs.

Respiratory Tract

The respiratory tract is woven into the lungs where gas exchange occurs, covering the respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli.

Nose

The internal structures of the nose fulfill these functions:

  1. Filter, warm, and humidify the incoming air.
  2. Detect olfactory stimuli.
  3. Modify sound vibrations emitted during speech.

Pharynx

  • Funnel-shaped tube extending from the internal nostrils down the neck.
  • Located posterior to the nasal and oral cavities, and anterior to the cervical vertebrae.
  • Composed of skeletal muscle and covered by a mucous membrane.
  • Functions as a pathway for both air and food.
  • Serves as a resonating chamber for speech sounds.
  • Contains the pharyngeal tonsils.
Nasopharynx

The nasopharyngeal tonsils are located on the posterior wall and exchange air with the nasal cavity, balancing air pressure between the pharynx and middle ear.

Oropharynx

Communicates with the mouth and nasopharynx, containing tonsils and the tongue.

Laryngopharynx

Connects the esophagus to the larynx. Along with the oropharynx, it serves as a passage for air, food, and liquids.

Larynx

Thyroid Cartilage

Forms the anterior wall of the larynx and is larger in men than in women.

Epiglottis

A cartilage that joins the thyroid cartilage and hyoid bone. It moves up and down, covering the larynx during swallowing to direct food and liquids into the esophagus. Coughing helps expel any foreign objects.

Cricoid Cartilage

A hyaline cartilage ring forming the bottom wall of the larynx and connected to the first tracheal cartilage. It serves as a benchmark for tracheotomy.

Arytenoid Cartilage

Composed of hyaline cartilage on the cricoid cartilage. They join the true vocal cords and throat muscles, participating in voice production.

Trachea

  • A tubular airway located anterior to the esophagus.
  • Extends from the larynx to the top of the T5 vertebra, where it splits into the left and right main bronchi.
  • Covered by mucosa and supported by cartilage.
  • Composed of 16 to 20 C-shaped rings of hyaline cartilage, preventing the trachea from collapsing inward and obstructing the airway.
  • The C-shape allows the esophagus to expand against the trachea during swallowing.

Bronchi and Bronchioles

  • The trachea divides into the right main bronchus (supplying the right lung with 3 lobes) and the left main bronchus (supplying the left lung with 2 lobes).
  • The main bronchi are incomplete cartilaginous rings, lined by pseudostratified ciliated columnar epithelium.
  • Pulmonary blood vessels, lymph vessels, and nerves enter along with the bronchi.

Lungs

  • There are two lungs, each with a conical shape.
  • Located in the chest cavity, alongside the heart and mediastinal structures.
  • Protected by the pleural membrane:
Pleural Membrane
  • The outer layer adheres to the diaphragm and chest wall cavity, called the parietal pleura.
  • The inner layer adheres to the lungs, called the visceral pleura.
Pleural Cavity

The space between the parietal and visceral pleura.

Each lobe is divided into smaller segments supplied by a tertiary or segmental bronchus.

The segments are divided into compartments called lobules, each receiving a lymphatic vessel, an arteriole, a venule, and a branch of a terminal bronchiole, all wrapped in elastic tissue.

The terminal bronchioles divide into microscopic branches called respiratory bronchioles.

The respiratory bronchioles are subdivided into several alveolar ducts, leading to two or more alveoli that share a channel called alveolar sacs.