Respiratory System Anatomy Quiz

Microscopic Structure of the Lung

• The lung lecture covered the microscopic structure of the lung, including the respiratory system and respiratory passages.
• Learning objectives included identifying and describing the histological structure of the upper and lower respiratory zones, the respiratory epithelium in the upper airways, and the bronchial tree at the level of bronchi.
• The respiratory system is anatomically classified into conducting and respiratory passages.
• Conducting passages include the nasal cavity, pharynx, larynx, trachea, primary bronchi until the level of the larynx.
• Lower respiratory tract includes the remaining part of the respiratory tract past the larynx.

Functional and Histological Classification

• Conducting passages conduct air to and from the lungs.
• They clean the air, removing dust, debris and particles.
• They also condition the air by warming and humidifying it, protecting the delicate respiratory tract structure.
• Conducting passages begin at the nose and end at the terminal bronchioles.
• No gas exchange occurs in this zone.
• No alveoli are present in this zone.

Respiratory Portion

• The respiratory portion is involved in gaseous exchange.
• Respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli are part of the respiratory portion.
• Terminal bronchioles are distinct from respiratory bronchioles.
• Alveoli are the sites of gas exchange in the lungs.

Respiratory Epithelium

• The respiratory epithelium lines the upper respiratory tract up to the large bronchioles.
• It's pseudostratified columnar epithelium with goblet cells.
• The lining transitions to simple epithelium in the terminal bronchioles.
• Cells found in the respiratory epithelium include goblet cells, ciliated cells, basal cells, brush cells, and small granule cells.
• Goblet cells secrete mucus to trap foreign bodies.
• Ciliated cells help move mucus and foreign materials out of the respiratory tract.
• Basal cells act as stem cells, renewing other cell types.
• Brush cells are chemosensory receptors.
• Small granule cells (neuroendocrine) release hormones and neurotransmitters.

Respiratory Epithelium - Trachea

• Tracheal epithelium is pseudostratified columnar ciliated epithelium with goblet cells.
• It has lamina propria with seromucous glands.
• The trachea has hyaline cartilage in a C-shaped structure, maintaining patency.

Bronchial Tree and Lung Lobules

• The bronchial tree begins at the trachea and branches into bronchi that further subdivide into bronchioles and alveoli.
• The right and left primary bronchus carry air into the corresponding lungs.
• Secondary bronchi further divide into tertiary bronchi supplying segments of each lobe.
• Bronchioles eventually lead to terminal bronchioles, which lead to respiratory bronchioles, then alveolar ducts, and finally to alveolar sacs. Alveoli are the main functional unit.

Bronchial Tree – Bronchi

• Bronchi have respiratory epithelium (including goblet cells).
• Lamina propria with glands (elastic-smooth muscle-MALT).
• Cartilage plates in the bronchi maintain patency.

Bronchial Tree - Bronchioles

• Bronchioles have simple columnar to simple cuboidal epithelium (no goblet cells).
• Lamina propria is more elastic.
• No cartilage and prominent smooth muscle are present in bronchioles.
• Clara cells are present in the bronchioles.

Questions & Answers

• Q1: Terminal bronchioles are lined with simple cuboidal ciliated epithelium.
• Q2: Terminal bronchioles do not perform gas exchange.
• Q3: Brush cells in the respiratory epithelium have chemosensory function.
• Q4: Cartilage is absent in the bronchioles.