Histology of Lower Respiratory Tract

Question 1

What is the function of the Larynx?

Answer 1

Phonation and to protect the trachea-bronchial tree

Question 2

How is the epithelium of the vocal cords different from the rest of the larynx?

Answer 2

Vocal cords: Stratified squamous

Rest of larynx: pseudostratified columnar

Question 3

Discuss the epithelium of the trachea

Answer 3

1. Respiratory epithelium
2. Lamina propria is vascular w/ BALT
3. Submucosa is dense, irregular CT w/ mucous glands
4. Adventitia

Question 4

Describe the Adventitia of the trachea

Answer 4

Made of C-shaped cartilage rings that separate it from submucosa. End of rings are attached by smooth muscle (trachealis m.)

Question 5

What is the function of the adventitia in the trachea?

Answer 5

Keeps airway open and accomadates expansion of the esophagus w/ swallowing

Question 6

Discuss the epithelium of the Primary bronchi

Answer 6

SAME AS TRACHEA

Question 7

Discuss the epithelium of the secondary (lobar) bronchi

Answer 7

1. Mucosa contains respiratory epithelium; Lamina propria has BALT
2. Smooth muscle for constriction/dilation
3. Cartilage

Question 8

Describe the cartilage of the secondary bronchi

Answer 8

Discontinous plates

Question 9

Describe the epithelium of the bronchioles

Answer 9

1. Epithelium is simple columnar that transitions to simple cuboidal
2. Ciliated cells
3. Goblet cells
4. Club cells

Question 10

What is the function of club cells?

Answer 10

non-ciliated columnar/cuboidal cells w/ dome-shaped surface

secrete a lipoprotein which prevents walls from sticking

Question 11

Is there cartilage in the bronchioles?

Answer 11

NO; elasticity of surrounding alveolar walls prevent collapse

Question 12

How do the airways change from primary bronchi to respiratory bronchioles?

Answer 12

Epithelium: pseudostratified columnar (bronchi) – ciliated columnar (bronchiole) – sparsely ciliated cuboidal (terminal/respiratory bronchiole) – simple squamous (alveoli)
o Goblet cells: absent beginning in terminal bronchioles
o Clara cells: increase in # beginning @ bronchioles
o Cartilage: plates in bronchus to none in bronchioles
o Smooth m.: spiral bundles throughout
o Glands: decrease from bronchus to none in terminal bronchioles
o Elastic fibers: high presence throughout

Question 13

How thick are the walls of alveoli? Why is that important?

Answer 13

The walls are 1 micrometer thick; Allows diffusion of oxygen and Carbon dioxide

Question 14

How are respiratory bronchioles different from terminal bronchioles?

Answer 14

Smooth muscle layer is interrupted by alveoli

Question 15

What type of epithelium is in the respiratory bronchioles?Are there glands or cartilage?

Answer 15

Simple cuboidal; No glands or cartilage

Question 16

What is the purpose of alveolar knobs?

Answer 16

Reinforces the interalveolar walls with CT and smooth muscle

Question 17

What are the cell types in the alveolar wall?

Answer 17

1. Type 1 pneumocyte: squamous epithelial cell
2. Type 2 pneumocyte: Cuboidal cell with surfactant
3. Capillary endothelium (continous); also converts Ang 1 - Ang 2
4. Fibroblasts (elastin and collagen)
5. Macrophages (heart failure/dust cells)
   .Pore of Kohn

Question 18

Describe the thin alveolar wall

Answer 18

Type 1 pneumocyte, endothelium and basement membrane; Gas exchange surface

Question 19

What is the function of the thick alveolar wall?

Answer 19

Stability; Accomodates ISF during edema

Question 20

Discuss the pulmonary circulation

Answer 20

1. Pulmonary aa acompany bronchi & bronchioles; Pulmonary veins DO NOT
2. Pulmonary veins and lymphatics travel in CT between pulmonary lobules
3. Venous drainage from bronchioles go into pulmonary veins WITHOUT becoming oxygenated (R to L shunt)