Histology of the Respiratory Tract Elizabeth J. Kovacs, Ph.D.

Learning Objectives: You should be able to:

• List the functions of the conducting portion of the airway. Draw a diagram of the mucocilliary escalator and describe how it functions. Be sure to include the different cell types involved.
• List the components of the wall of the trachea. Compare and contrast the structural features of the wall of the trachea, an intrapulmonary bronchus and a bronchiole.
• List the cell types you would expect to find in an alveolus. Correlate alveolar structure with alveolar function.
• Describe the path of an oxygen molecule from the trachea through out the conducting portion of the airway into a capillary in the wall of an alveolus. List the barriers to a molecule of oxygen from the alveolar space to a red blood cell in a pulmonary capillary.
• Compare and contrast the architecture of a normal lung with that of a smoker, someone with emphysema, fibrosis, or asthma.
• Remember that lungs are your friends (so don't smoke).

Overview     Upper Portion of the Airway     Lower Portion of the Airway     Lung Disorders     MainMenu

1. Upper and Lower Airways
2. Conducting Portion and Respiratory Portion (Fig. 1)
3. Cells, Tissues and Structure
   • epithelium
   • lamina propria (loose CT with lymphoid tissue)
   • bone, cartilage, smooth muscle (support structures)
   • submucosal CT with glands
   • adventitia - submucosal CT (connect to surroundings)

Upper Portion of the Airway

1. Structure - Nose and Mouth
2. Function(s)
   • humidifying
   • warming (or cooling)
   • removing suspended particles

Lower Portion of the Airway

1. Trachea
   • respiratory epithelium
   • mucocilliary escalator (Fig. 2)
2. Bronchi
   • main (primary) bronchi
   • secondary bronchi
   • etc.
3. Bronchioles
   • preterminal
   • terminal
   • respiratory
4. Alveoli
   • structure
     
     Alveolar ducts
     Alveolar sacs
     Alveoli
     Alveolar pores
   • cell types (Fig. 3)
     • type I pneumocyte (squamous epithelium)
     • type II pneumocyte
     • alveolar macrophages
     • endothelial cell
     • function - alveolar capillary barrier (Fig. 4)

        

Overview     Upper Portion of the Airway     Lower Portion of the Airway     Lung Disorders     MainMenu

Lung Disorders

1. Black lung disease (pneumoconiosis)
2. Emphysema
3. Asthma