Respiratory Microanatomy

Question 1

respiratory epithelium

Answer 1

*pseudostratified ciliated columnar epithelium
*lines most of the respiratory tract (starting in the nasopharynx)
*contains:
-ciliated columnar cells
-goblet cells
-basal cells (mitotically active stem cells near basement membrane)
-brush cells
-small granule cells

Question 2

olfactory epithelium

Answer 2

*pseudostratified ciliated columnar epithelium in the apical aspect of the nasal cavity
*olfactory neurons: bipolar neurons (one dendrite and one axon) between the epithelial cells; non-motile cilia chemoreceptors
*supporting (sustentacular) cells: maintain the healthy environment for the olfactory neurons
*basal cells: stem cells for both olfactory neurons and supporting cells

Question 3

epithelia of the nasal cavities, pharynx, and larynx

Answer 3

*nasopharynx: mucosa resembles classic respiratory epithelium (pseudostratified ciliated columnar)
*oropharynx & laryngopharynx appears non-keratinized stratified squamous

Question 4

elements of the conducting zone of the airway

Answer 4

*primary bronchus
*secondary (lobar) bronchus
*tertiary bronchus (bronchopulmonary segments)
*bronchioles
*terminal bronchioles

Question 5

elements of the respiratory zone of the airway

Answer 5

*respiratory bronchioles
*alveolar ducts
*alveolar sacs
*alveoli

Question 6

trachea - histology

Answer 6

*4 layers:
1. mucosa - ciliated pseudostratified columnar epithelium & glands
2. submucosa - glands & lymphoid tissue
3. hyaline cartilage: - C-shaped ring; trachealis muscle bridging the end of the C-shaped cartilage rings
4. adventitia

Question 7

large bronchi (primary, secondary, and tertiary) - histology

Answer 7

*layers like the trachea (mucosa, submucosa, cartilage, adventitia)
*ISOLATED PLATES OF HYALINE CARTILAGE
*abundance of glands
*smooth muscle bundles and elastic fibers are more prominent in smaller bronchi
*lymphoid tissues (MALT)

Question 8

bronchioles - histology

Answer 8

*ciliated pseudocolumnar
*NO CARTILAGE!!
*fewer glands than bronchi
*more smooth muscle cells
*more elastic fibers

Question 9

terminal bronchioles - histology

Answer 9

*ciliated simple CUBOIDAL epithelium
*smooth muscle cells and elastic fibers
*fewer glands
*CLUB CELLS:
-non-ciliated and dome-shaped in the mucosa lining
-secretion of surfactant-like substance
-detoxify the harmful substance
-stem cell to regenerate epithelial cells

Question 10

club cells

Answer 10

*non-ciliated and dome-shaped in the mucosa lining of the TERMINAL AND RESPIRATORY BRONCHIOLES
*secretion of surfactant-like substances
*detoxify harmful substances
*stem cell to regenerate epithelial cells

Question 11

respiratory bronchioles - histology

Answer 11

*ciliated cuboidal epithelium (similar to terminal bronchioles), except for the presence of numerous alveoli along its length

Question 12

alveolar ducts - histology

Answer 12

*transition from simple cuboidal to simple SQUAMOUS epithelium with NO CILIA
*branch off respiratory bronchioles and lead to alveolar sacs

Question 13

alveolar sacs - histology

Answer 13

*large clusters of alveoli
*form the ends of alveolar ducts distally
*the lamina propria is extremely thin and consists of a network of ELASTIC and RETICULAR fibers that encircle the alveolar openings:
-elastic fibers: help the recoil during expiration
-reticular fibers: prevent overextension of the alveoli during inspiration

Question 14

alveoli - cell types

Answer 14

*type I pneumocytes & type II pneumocytes
*alveolar macrophages

Question 15

type I pneumocytes

Answer 15

*simple squamous (flat) cells that thinly line the alveoli for OPTIMAL GAS EXCHANGE

Question 16

type II pneumocytes

Answer 16

*septal cells (CUBOIDAL CELLS) that serve 2 functions:
1. produce SURFACTANT to reduce surface tension of the alveoli and prevent collapse
2. stem cell precursors for type I and type II pneumocytes when they are damaged

Question 17

alveolar macrophages

Answer 17

*phagocytose foreign materials
*release cytokines and alveolar proteases
*biggest cells in the alveoli
*participate in non-specific immunity

Question 18

pulmonary vasculature - microanatomy

Answer 18

*pulmonary arterioles are closer to the airway, while pulmonary venules are more in the parenchyma, away from the airway