Respiratory System

Learning objectives

1. Recognize major parts of the respiratory track: trachea, bronchi, bronchioles, terminal bronchioles, respiratory bronchioles, alveolar duct, and alveoli.

2. Understand the blood-air interface in the alveolus and know the function of the type I and II pneumocyte and alveolar macrophage.

The respiratory system functions in the exchange of gases between the external and internal environments. Major parts of the system include the nasal cavity, larynx, trachea, bronchi, and pulmonary alveoli. Some regions of the respiratory system are specialized for conduction of gases and other areas function primarily in the exchange of gases. Filtration mechanisms exist in both regions. The function of each part of the respiratory system is reflected in the structure of its wall: the type of epithelium and its apical modifications, intraepithelial and subepithelial glands, cartilaginous rings and plates, smooth muscle and elastic tissue, and the relationship of capillary endothelium to alveolar epithelium.

Segment Characteristics
Trachea Cartilage rings, pseudostratified ciliated epithelium with goblet cells, glands in submucosa
Bronchi Plates of cartilage, smooth muscle, pseudostratified ciliated epithelium with goblet cells, glands may be present
Bronchioles No cartilage, smooth muscle, no glands Larger: pseudostratified ciliated epithelium with goblet cells
Smaller: simple columnar or cuboidal, ciliated epithelium
Terminal: Simple cuboidal ciliated epithelium with non-ciliated Clara (club) cells
Bronchioles Alveoli form out-pocketings from walls of bronchiole, smooth muscle in non-respiratory portions of walls Initial segment: both ciliated and Clara (club) cells
Distal segment: Clara (club) cells predominate
Alveolar ducts and alveoli Squamous epithelium (type I pneumocytes), surfactant cells (type II pneumocytes), macrophages

Lab activities

  1. Respiratory System: Slides
  2. Respiratory System: Micrographs
  3. Questions
  4. Answers