Histology of Respiratory System Flashcards
What is the basic histology of the respiratory tract?
The respiratory tract has a histological structure that varies from the upper to the lower parts:
Nasal cavity and upper respiratory tract (e.g., trachea, bronchi):
Epithelium: Ciliated pseudostratified columnar epithelium with goblet cells that secrete mucus to trap debris and pathogens.
Lamina propria: Contains connective tissue, blood vessels, and immune cells like lymphocytes.
Cartilage: C-shaped cartilage rings in the trachea that provide structural support.
Smooth muscle: Located in the walls of the trachea and bronchi, helping with bronchoconstriction.
Bronchi and bronchioles:
Bronchi: Lined by ciliated pseudostratified columnar epithelium with goblet cells. Cartilage rings are replaced by cartilage plates as the bronchi divide.
Bronchioles: Lined by simple columnar to cuboidal epithelium, with less cartilage and no goblet cells. Smooth muscle becomes more prominent to regulate airflow.
Alveoli:
Epithelium: Composed of type I alveolar cells (simple squamous) for gas exchange and type II alveolar cells (cuboidal) that secrete surfactant to reduce surface tension.
What is the basic histology of the lungs?
The lungs are made up of several structures with distinct histological features:
Lung parenchyma:
Alveolar sacs are composed of clusters of alveoli, where gas exchange occurs.
Alveolar epithelium: Type I alveolar cells form the thin wall of the alveolus, while Type II cells produce surfactant, which reduces surface tension and prevents alveolar collapse.
Pulmonary blood vessels:
Surrounding the alveoli are capillaries where gas exchange occurs (oxygen diffuses into the blood, and carbon dioxide diffuses out).
The pulmonary arteries bring deoxygenated blood, and the pulmonary veins carry oxygenated blood.
Interstitium (connective tissue):
Between the alveoli and blood vessels, the interstitium consists of elastic fibers and collagen, which help maintain lung structure and elasticity.
The lungs have a rich network of lymphatic vessels for immune surveillance and fluid drainage.
Bronchi and bronchioles:
Similar to the respiratory tract, the bronchi have cartilage and smooth muscle, and the bronchioles have more smooth muscle and a thinner epithelium as they get smaller.
