Histology of the Respiratory System

Question 1

List the functions of the respiratory system

Answer 1

• Supplies oxygen, gets rid of carbon dioxide
• Phonation (voice)
• Olfaction (smell)
• Blood pressure control
• Acid-Base Balance

Question 2

List the functions of the nasal cavity

Answer 2

• Warms air
• Moistens air
• Filters air
• Site for olfaction

(Has turbulent airflow due to conchae)

Question 3

Describe the epithelium found in the nasal vestibule

Answer 3

Keratinised stratified squamous epithelium

Question 4

Describe the epithelium that lines the nasal cavity (except for the vestibule and olfactory region)

Answer 4

Respiratory epithelium

• pseudostratified ciliated columnar epithelium with goblet cells

Question 5

Describe respiratory epithelium

Answer 5

• Pseudostratified ciliated columnar epithelium
• Goblet cells
• Basal Cell
• Club cells

Question 6

Describe what you would see in a birds eye view of respiratory epithelium

Answer 6

• Majority ciliated cells

- Significant non-ciliated regions (Goblet cells)

Question 7

What type of epithelium is found in the oropharynx?

Answer 7

Non-keratinised stratified squamous epithelium

Question 8

What type of epithelium is found in the larynx and trachea?

Answer 8

Respiratory epithelium

Question 9

What type of epithelium is found on the epiglottis?

Answer 9

The posterior (larynx facing) side:

• Respiratory epithelium

The anterior (tongue) side:

• Stratified squamous epithelium (non-keratinised)

Question 10

Describe the mechanism by which the nasal cavity gets blocked

(question NOT referring to soft palate erection)

Answer 10

• The venous sinuses of the the lamina propria in the conchae engorge with blood
• Increased mucus production

Question 11

What type of epithelium is found in the laryngopharynx?

Answer 11

• Stratified squamous epithelium

Question 12

Describe the lamina propria found under the respiratory epithelium in the nasal cavity

Answer 12

• Under the epithelium
• Band of connective tissue
• Has seromucous glands
• Has thin-walled venous sinuses
• Has a small amounts of bone

Question 13

Describe the histology the larynx?

Answer 13

The walls of the larynx:
- Cartilage

The muscles of the larynx:
- Respiratory epithelium

Vocal folds & adjacent structures:
- Stratified squamous epithelium

Question 14

Where on the larynx can you find stratified squamous epithelium?

Answer 14

The vocal folds

and adjacent structures

Question 15

Describe the rings of cartilage found on the trachea

Answer 15

• 15-20 rings
• Hyaline cartilage
• Not complete circles (Have a small opening, “C” shaped)
• The opening is spanned by fibroelastic tissue and smooth muscle (trachealis muscle)

Question 16

What fills the gap in the tracheal cartilage rings?

Answer 16

• fibroelastic tissue

- trachealis muscle (smooth muscle)

Question 17

Describe the layers of tissue found in the trachea

Answer 17

Respiratory epithelium
-->
Basal lamina
-->
Lamina propria - (connective tissue and elastic fibres)
-->
Submucosa - (connective tissue and seromucous glands)
-->
Cartilage

Question 18

Name the 2 divisions of the trachea

Name the cartilaginous ridge that separates them

Answer 18

• The primary (main) bronchi

- The carina

Question 19

Describe the structure of a bronchus

Answer 19

Respiratory epithelium
-->
Lamina propria
-->
Muscularis (ring of smooth muscle)
-->
Submucosa
-->
Cartilage (interconnected flat plates, rather than "C" shapes)

Question 20

Describe the cartilage that surrounds bronchi

Answer 20

• Hyaline cartilage
• Irregular plates
• Fully surrounds the bronchial lumen

Question 21

Describe the changes in abundance of cartilage as you go down the bronchial tree

Answer 21

Trachea:
- Rings of hyaline cartilage

Bronchi:

• Irregular plates of hyaline cartilage
• Get more discontinuous deeped down

Bronchioles:
- No cartilage (none past segmental bronchi)

Question 22

Describe the lining of a bronchiole

Answer 22

• Epithelium height decreases from columnar to cuboidal as you go down
• Ciliated epithelium
• Initially some goblet cells

Question 23

What is the name of the smallest bronchioles to lack respiratory function?

Answer 23

Terminal bronchioles

Bronchioles –> Terminal –> Respiratory bronchioles

Question 24

Name the first part of the respiratory tree to have respiratory function

Answer 24

Respiratory bronchioles

they have alveoli in their walls

Question 25

Describe the lumen diameter of bronchioles

Answer 25

Less than 1mm

Question 26

Do bronchioles have cartilage?

Answer 26

No

Question 27

List what stimulates the smooth muscle of bronchioles to contract

Answer 27

- Parasympathetic stimulation (M3 muscarinic) - Histamine - Other factors (doesn't matter)

Question 28

Describe the lining of terminal bronchioles

Answer 28

- Cuboidal ciliated epithelium - Club cells (project above epithelium) - Have a layer of smooth muscle

Question 29

Describe the role of Club (Clara) cells

Answer 29

Club cells are non-ciliated - Produce surfactant (a little) - Detoxification - Immune modulation - Stem cells

Question 30

Describe respiratory bronchioles

Answer 30

- Ciliated cuboidal epithelium - Club cells - Lots of envagination by alvioli

Question 31

Describe alveolar ducts

Answer 31

- Split off from respiratory bronchioles | - Lined with alveoli and alveolar sacs

Question 32

Describe alveolar sacs

Answer 32

- Split off of alveolar ducts | - Groupings of alveoli

Question 33

Describe the lining of alveoli

Answer 33

- Type 1 alveolar cells | - Type 2 alveolar cells

Question 34

Describe Type 1 alveolar cells (type 1 pneumocytes)

Answer 34

- Simple squamous epithelium - Lines the alveolar surfaces - covers about 90% of the alveolar surface

Question 35

Describe Type 2 alveolar cells (type 2 pneumocytes)

Answer 35

- Polygonal in shape (found at the joins between alveoli) - Free surface is covered in microvilli - Produces surfactant (exocytosis of lamellar bodies)

Question 36

Describe alveolar macrophages (dust cells)

Answer 36

- Free cells - Phagocytose foreign bodies - Usually migrate up the respiratory tree (mucociliary escalator) to be swallowed - But may move to the septal connective tissue

Question 37

Describe how type 2 pneumocytes coat the alveolar surface in surfactant

Answer 37

- Surfactant in lamellar bodies in the cytoplasm - Lamellar bodies are exocytosed - Surfactant released

Question 38

Describe the blood-air barrier

Answer 38

The tissue between the alveolar lumen and the pulmonary blood vessels that permeate the alveolar septa - 2 cells thick - Type 1 pneumocyte --> Basal lamina (shared) --> Endothelium

Question 39

List the surfactant producing cells

Answer 39

- Type 2 pneumocytes (main) | - Club cells (minor)

Question 40

List the layers of the air-blood barrier

Answer 40

``` Type 1 pneumocyte --> Basal lamina --> Endothelial cell ```

Question 41

Describe the layers of the visceral pleura

Answer 41

``` Outer layer (mesothelium): - simple squamous epithelium ``` Inner layers: - fibrous connective tissue - elastic connective tissue ``` Mesothelium --> Fibrous and elastic connective tissue --> Alveolar wall ```

Question 42

Describe the respiratory tree

Answer 42

``` Trachea --> Primary Bronchi --> Bronchi --> Bronchioles --> Terminal Bronchioles --> Respiratory Bronchioles --> Alveolar ducts --> Alveolar sacs --> Alveoli ```