Respiratory Histology

Question 1

Describe the features of Respiratory Epithelia. (Compare to Olfactory Epithelia)

Answer 1

Thinner than olfactory epithelia.

1. Goblets cells
2. Pseudostratified columnar epithelia
3. Presence Cilia

Question 2

Describe the features of the Olfactory Epithelia. (Compare this to the Respiratory Epithelia.)

Answer 2

THICKER than respiratory epithelia and has 3 cell types. NO GOBLET CELLS are present.

1. Sensory (Olfactory) Receptor Cells
2. Sustentacular Cells
3. Basal Cells

Question 3

What features are present in the larynx.

Answer 3

1. The larynx has 3 pairs of hyaline cartilage.
2. The ventricular fold is closer to the back cartilage plates.
3. The vocal folds are present in the middle of the larynx, featuring Vocalis Muscle.

Question 4

What features are present in the Trachea?

Answer 4

1. C-ring hyaline cartilage with Trachealis Muscle near the anterior side for tracheal diameter regulation.
2. Smooth muscle, then adventitia surrounds the trachea.
3. No Lung Tissue is present
   * From lumen and out: Respiratory Epithelium > Basement Membrane > Lamina Propria > Cartilage > Adipocytes (Adventitia)

Question 5

Describe and name the 3 components of the Blood Air Barrier.

Answer 5

BaB has a lot of surface area for effective gas exchange.

1. Pneumocytes Type I
2. Shared Basement Membrane with the…
3. Endothelial Cells of Pulmonary Capillary

Question 6

Describe the features of the Muscular Bronchioles.

Answer 6

1. No Cartilage is present.
2. Smooth Muscle Walls surround the bronchioles
3. Clara Cells start to appear.
4. Goblet cells start to disappear.
5. CT contains ELASTIN fibers.

Question 7

How does the Intrapulmonary bronchioles differ from the muscular?

Answer 7

1. Features Cartilage Plates
2. Lung tissue (alveoli) is seen around it.
3. These run alongside Pulmonary Arteries.

Question 8

What features are seen in smaller bronchioles?

Answer 8

1. Clara Cells - secrete lipoprotein to reduce surface tension within the smaller sections of the conduction system. These also serve as stem cells.
2. These bronchioles don’t have alveolar sacs. They precede terminal bronchioles.

Question 9

Describe the main features of Terminal Respiratory Bronchioles and Alveoli.

Answer 9

1. ELASTIN FIBERS and Simple Squamous Epithelium are more abundant.
2. Terminal Bronchioles lie more distal to the small bronchioles [span outward 3D]
3. Type 1 Pneumocytes form most of the alveolar walls. Type 2 Pneumocytes secrete surfactant to prevent collapse during pressure changes.

Question 10

Define the function of Sustentacular cells.

Answer 10

These support other cells in the olfactory epithelium, especially the receptor cells (olfactory neurons).
*They are anatomically above receptor nuclei closer to nasal lumen.

Question 11

Describe the function of basal cells.

Answer 11

Basal cells serve as stem cells in the olfactory epithelium.

Question 12

What do Bowman’s Glands do in the lamina propria?

Answer 12

Secrete a watery, proteinaceous secretion which acts as a solvent for odorous substances.

Question 13

Describe the histological differences between the ventricular and vocal folds of the larynx.

Answer 13

1. Ventricular folds - pseudostratified epithelium, core of CT
2. Vocal folds - stratified squamous epithelium, core of Skeletal muscle

Question 14

Describe the function of Clara Cells and where they are found.

Answer 14

1. Secrete a Lipko-protein substance that acts like surfactant (but isn’t). Can serve as stem cells too.
2. They start to appear in muscular bronchioles and further down the tract.

Question 15

Distinguish the trachea, Intrapulmonary bronchus and the muscular bronchiole from each other.

Answer 15

1. Trachea - no lung tissue, C-shaped cartilage ring.
2. IP Bronchus - Lung tissue is present with cartilage plates and respiratory epithelium.
3. Muscular bronchiole - no cartilage present, surrounded by SM and contains Clara cells.

Question 16

Describe the histology of the Respiratory bronchiole.

Answer 16

Marks the start of gas exchange in the respiratory system. Indicated by “thin outpockets” of simple squamous epithelium.

Question 17

How can one tell the difference between a pulmonary artery and pulmonary vein?

Answer 17

Pulmonary arteries run ALONGSIDE respiratory bronchioles.

Pulmonary veins are usually present further AWAY from bronchioles.

Question 18

Distinguish the Type I Pneumocytes from the Type II. (Function and histology)

Answer 18

Type I Pneumocytes - is more abundant in numbers and composes the alveolar wall. These are thin for gas exchange.
Type II - secrete surfactant to reduce Surface tension and are observed with “multilamellar vesicles” under SEM

Question 19

Describe the physical features and function of the alveolar macrophage.

Answer 19

The “dust cell” functions to clean the alveolar passages by collecting microbes and debris. They look like spotted, loose cells microscopically. Easy to distinguish.

Question 20

Describe the pathophysiology of Emphysema.

Answer 20

1. Prolonged smoking or exposure to pollutants lead to more macrophages.
2. Macrophages secrete proteases and LESS a1-antitrypsin (normally prevents elastace from breaking down elastin)
3. Neutrophils release more “unhindered” ELASTACE that breaks down alveolar walls.
4. Manifests as Reduced Total SA; expanded alveoli ~ hindered gas exchange.
5. Patient is known to have “barrel chest” due to HYPERINFLATION