Study Guide on the Respiratory System: Larynx, Trachea, and Bronchial Tree

Larynx

• The larynx, also known as the voice box, plays a crucial role in the respiratory system.

Cartilages of the Larynx

  • Comprised of 9 cartilages in total:

    • 3 paired cartilages:

    • Arytenoids

    • Corniculates

    • 3 unpaired (single) cartilages:

    • Epiglottis (elastic cartilage)

    • Thyroid (hyaline cartilage)

      • The largest cartilage, referred to as the "Adam's apple"

      • In males, it is around 4 inches in size and plays a role in deepening the voice during puberty

    • Cricoid (hyaline cartilage)

      • Shaped like a signet ring

Vocal Cords

  • The larynx consists of folds of mucous membrane that form:

    • False vocal cords (vestibular folds)

    • True vocal cords (vocal folds)

  • The tension applied to the vocal cords can be adjusted by the contraction of muscles, particularly the thyroarytenoid muscle, which raises the pitch of the voice.

  • The glottis is the opening between the true vocal cords.

Trachea

  • The trachea is approximately 4-5 inches long and composed of 16-20 C-shaped rings of hyaline cartilage, which provide structural support.

  • The trachea's lumen is located anterior to the esophagus, allowing flexibility for swallowing.

  • The trachea is lined with smooth muscle that allows the esophagus to expand when food passes through.

Bronchial Tree

  • The bronchial tree consists of larger and straighter conducting airways.

  • Major components include:

    • 1° bronchus (primary bronchus)

      • Divides into 2° bronchi (secondary bronchi)

      • The left primary bronchus is also known as the left main stem bronchus.

    • The secondary bronchi (lobar bronchi) feed into the lobes of the lungs:

      • Right lung has 3 lobes, thus 3 secondary bronchi

      • Left lung has 2 lobes, thus 2 secondary bronchi

    • 3° bronchi: also referred to as segmental bronchi, further divide into smaller branches.

    • Bronchioles continue to divide approximately 12 times, leading to terminal bronchioles and respiratory bronchioles.

    • Alveolar sacs contain clusters of alveoli, which are the functional units of gas exchange in the lungs.

  • Alveoli are involved in the exchange of oxygen and carbon dioxide with the bloodstream.

    • Alveolar macrophages are present to prevent infection.

    • Type I pneumocytes:

      • Simple squamous epithelial cells that make up the structure of alveoli.

    • Type II pneumocytes secrete surfactant, a substance that prevents alveoli from collapsing by reducing surface tension.

Pleura and Pleural Cavity

  • The pleura consists of two membranes that enclose the lungs:

    • Visceral pleura: lines the lungs directly

    • Parietal pleura: lines the thoracic cavity

  • The pleural cavity is the space between these two pleurae, which contains pleural fluid that acts as a lubricant to reduce friction during respiratory movements.

Fissures of the Lungs

  • The lungs have several anatomical features, including fissures:

    • Horizontal fissure: separates the upper and middle lobes of the right lung

    • Oblique fissure: separates the lower lobe from the upper and middle lobes (right lung) and upper lobe from the lower lobe (left lung).