Respiratory Microanatomy

Question 1

recognize the types of epithelium, CT, muscle, and cartilage within the respiratory system

Question 2

recognize the type of epithelium that lines the outer surface of the lungs and recall why it is a serous membrane

Answer 2

covered by mesothelium; is a serous membrane because it is in a body cavity

Question 3

what is the orientation of the abundant elastic fibers in the lamina propria?

Answer 3

longitudinally oriented

Question 4

describe the tunica of the trachea

Answer 4

1. tunica mucosa
   1a. lamina epithelialis: repsiratory epithelium (pseudostratified columnar)
   1b. lamina propria: CT nad longitudinally oriented elastic fibers
   1c. NO lamina muscularis
2. tunica submucosa: submucosal glands
3. tunica muscularis: cartilaginous rings and tracheal muscle
4. tunica adventitia (not body cavity) or tunica serosa (in body cavity)

Question 5

describe the tunica of the bronchi

Answer 5

1. tunica mucosa
   1a. lamina epithelialis: ciliated pseudostratified columnar epithelium with goblet cells
   1b. lamina propria: abundant elastic fibers and areolar (loose irregular) CT
   1c. lamina muscularis: smooth muscle, when contracted narrows diameter of airway
2. tunica submucosa: bronchial glands
3. tunica muscularis: cartilage plates that change shape
4. tunica adventitia: loos CT with elastic fibers

Question 6

describe the tunics of the bronchioles

Answer 6

1. tunica mucosa:
   1a. lamina epithelialis: simple cuboidal/columnar (+/- ciliated and goblet cells), club/clara cels
   1b. lamina propria: loose irregular CT
   1c. lamina muscularis: smooth muscle
2. tunica submucosa: NO submucosal glands
3. tunica muscularis: NO cartilage plates
4. tunica adventitia: loose CT with elastic fibers

Question 7

is there a lamina muscularis in the trachea?

Answer 7

nope!

Question 8

the submucosal glands of the trachea are the sero-mucous glands; what does the serous component do? is there any other source of mucous in the trachea besides the submucosal glands?

Answer 8

the submucosal glands produce the majority of the mucous blanket that covers the tracheal epithelium (and is constantly moving in a one-way direction toward the pharynx due to the action of the cilia-mucociliary escalator)

Question 9

list the 2 major components of the tunica muscularis of the trachea

Answer 9

1. cartilaginous rings: successive C shaped bands of hyaline cartilage that prevent tracheal collapse during normal changes in positive and negative pressure required to move air into and out of lungs
2. trachealis muscle: smooth muscle; capable of narrowing diameter of the trachea when contracted, narrowing can increase velocity of air passing through the trachea (coughing, sneezing), which can be important in clearing airways

Question 10

what type of muscle is the trachealis muscle?

Answer 10

smooth muscle

Question 11

in which direction are the fibers of the trachealis muscle oriented and how does this help the muscle perform its job?

Answer 11

longitudinally

Question 12

would you expect the trachea to have a tunica serosa as it passes through the neck?

Answer 12

no because the neck is not in a body cavity

Question 13

compare the large and small bronchi; what changes are occurring with the cartilage as the bronchi decrease in diameter? are submucosal glands present in all bronchi?

Answer 13

hyaline cartilage plates that gradually change shape with successive branching from C shaped rings in the trachea to plates of irregular shape and decreasing size; present in all?

Question 14

distinguish between bronchi and bronchioles; what structures do bronchi have that are absent in bronchioles?

Answer 14

bronchioles do not have cartilage!! bronchioles are also getting rid of their submucosal glands

Question 15

is there a lamina muscularis present in bronchi and bronchioles?

Answer 15

yes

Question 16

if the smooth muscle contracts tightly within the airways, where in the bronchial tree is there potential for complete closure of the airway lumen?

Answer 16

maybe where there is no cartilage?aka in bronchioles

Question 17

distinguish between conducting and respiratory airways

Answer 17

the conducting airways just transport air; the respiratory airways are where gas exchange occurs

Question 18

describe respiratory bronchioles

Answer 18

lined by simple cuboidal epithelium with some ciliated cells, except where the single alveoli branch from the bronchiole wall

Question 19

distinguish between type I and type II pneumocytes and alveolar macrophages within the alveoli

Answer 19

type I: simple squamous, cover 90-96% of SURFACE area of lungs, but only make up 5-9% of the total cells of the lung

type II: simple cuboidal cells with a large central nucleus and cytoplasm filled with lamellar bodies that contain phospholipid components of surfactant, comprise 12-18% of lung cells but only 3-10% of lung surface area and are progenitor cells for type I pneumocytes

alveolar macrophages: active phagocytes that make up 2-9% of lung cells, derived from blood monocytes but capable of division; maintain a sterile environment in the alveoli and produce growth factors to repair the alveoli

Question 20

distinguish between classic respiratory epithelium and club/clara cells

Answer 20

club/clara cells are in the tunica mucosa of bronchioles, are bronchiolar exocrine cells and have a dome-shaped surface and metabolize pollutants

Question 21

list the layers of the blood air barrier (3)

Answer 21

1. type I pneumocyte
2. adjacent capillary endothelial cell
3. their fused/shared basement membranes