Respiratory Histology

Question 1

What are the two ‘divisions’ of the pulmonary tree?

Answer 1

conducting division and respiratory division

Question 2

What are the structures associated with the conducting division of the pulmonary tree?

Answer 2

nasal cavities all the way down to terminal bronchioles (includes pharynx, larynx, trachea, 1 bronchi, 2 bronchi, 3 bronchi, bronchioles, and the terminal bronchioles

Question 3

What are the structures associated with the respiratory division of the pulmonary tree?

Answer 3

respiratory bronchioles, alveolar ducts, alveoli

Question 4

Where do you see a change from ring shaped to plate shaped cartilage on the pulmonary tree?

Answer 4

intrapulmonary bronchi

Question 5

What are some distinguishing characteristics of intrapulmonary bronchi?

Answer 5

-cartilage changes from rings to plates-there is lamina propria containing criss-crossing bundles of spirally arranged smooth muscle and elastic fibers -lymphoid tissue becomes more abundant

Question 6

The mucosa layer of the respiratory system contains what kinds of cells?

Answer 6

ciliated columnar cells, goblet cells, brush (chemosensory) and basal (stem cells for the epithelium) cells, lymphocytes

Question 7

What layers of the pulmonary tree have epithelium?

Answer 7

ALL layers.

Question 8

What layers of the pulmonary tree have goblet cells?

Answer 8

all the way down to segmental bronchi (i.e. no terminal bronchi or lower)same abundance all the way until the main bronchi start, then tapers down

Question 9

What layers of the pulmonary tree have ciliated cells?

Answer 9

all the way down to respiratory bronchioles (i.e. no alveolar ducts or further)same abundance all the way until the terminal bronchi, then tapers down

Question 10

What layers of the pulmonary tree have glands?

Answer 10

all the way down to segmental bronchi (i.e. no terminal bronchi or lower)same abundance all the way until the lobar bronchi, then tapers down

Question 11

What layers of the pulmonary tree have hyaline cartilage?

Answer 11

all the way down to segmental bronchi (i.e. no terminal bronchi or lower)tapers down in abundance from the start of the trachea to where it ends

Question 12

What layers of the pulmonary tree have smooth msucle?

Answer 12

all the way down to alveolar ducts (i.e. no alveolar sacs or further)same abundance all the way until the terminal bronchi, then tapers down

Question 13

What layers of the pulmonary tree have elastic fibers?

Answer 13

ALL layerssame abundance all the way until the alveolar ducts, then tapers down

Question 14

How does/can smoking affect the trachea and bronchi in terms of epithelial?

Answer 14

1) smoking can introduce chronic irritants to the PSCC epithelium in these structures.2) chronic irritants can cause the epithelial cells to lose their coordinated patterns, which can impact mucous removal, and eventually chronic coughing as a result3) chronic coughing causes PSCC epithelium to undergo columnar-to-startfied squamous metaplasia (reversible but damaging particularly in trachea)NOTE: squamous cell carcinomas have their origin in metaplastic epithelium

Question 15

What kinds of characteristics of bronchioles distinguish them?

Answer 15

only the mucosa layers remain (no muscularis externa or adventitia) submucosa layer and its glands are gonefew or no goblet cellshas Clara cells epithelial cells are more cuboidal than columnar (PSCC cells still present)- more so toward terminal bronchiolesmuscularis mucosa is well developed

Question 16

What do Clara cells secrete in bronchioles?

Answer 16

a surface active agent and clara cell protein (CC16)- if CC16 levels are low, it means there is damage to that part of the bronchiole

Question 17

What does the muscularis mucosa do in bronchioles?

Answer 17

it is a major player in determining the diameter of the bronchiole (has a high elastic content of smooth muscle)

Question 18

What is the main kind of epithelial cell in terminal bronchioles?

Answer 18

cuboidal

Question 19

What is the main kind of epithelial cell in bronchioles?

Answer 19

PSCC (

Question 20

What kind of epithelium do respiratory bronchioles have?

Answer 20

ciliated cuboidal (very hard to see the cilia because they are small)

Question 21

Do respiratory bronchioles have smooth muscle and elastic CT?

Answer 21

Yes. They also have clara cells

Question 22

Alveolar ducts are lined by what?

Answer 22

alveoli and alveolar sacs

Question 23

the knobs that are part of the lining of alveolar ducts contain what?

Answer 23

smooth muscle, collagen, and elastic fibers

Question 24

What is the role of the knobs that help line the alveolar ducts?

Answer 24

they help support the structure of the wall

Question 25

What kinds of cells do alveoli contain?

Answer 25

Type 1 and 2 pneumocytes (aka alveoli cells)macrophages

Question 26

What do Type 1 pneumocytes do in alveoli?

Answer 26

make up to 95% of the alveolar lining (squamous shaped)

Question 27

What do Type 2 pneumocytes do in alveoli?

Answer 27

cuboidal shaped (or round)1) they serve as stem cells for type 1 2) They secrete surfactant (to reduce surface tension) and other proteins that contribute to immune function3) make up to 5% of alveoli lining

Question 28

Which are more numerous, Type 1 or Type 2 peunocytes?

Answer 28

they are present in equal abundance

Question 29

What is the alveoli septa?

Answer 29

type 1 (and some 2) pneumocytes and their basal lamina and the endothelial and basal lamina of the capillary

Question 30

What are the two regions of the alveolus?

Answer 30

thick and thin

Question 31

Where is the thick region of the alveolus and what does it contain?

Answer 31

where fibroblasts, macrophages, and fibers intervene between the epithelium of the alveolus and the capillarycontains type 2 epithelial cells

Question 32

What happens in the thin layer of the alveolus?

Answer 32

gas exchange

Question 33

What are the contents of the thin region of the alveolus?

Answer 33

thin layer of surfactanttype 1 epithelial cell and its basal laminaan endothelial cell and its basal lamina(these two basal laminas are often fused)

Question 34

What to alveoli macrophages do?

Answer 34

aka dust cellsscavenge inhaled particulate matter

Question 35

How does collateral circulation of alveoli work?

Answer 35

alveolar pores (of Kohn) are in the inter alveolar septa and they allow passage of air to occur between alveoli when normal pathways are constricted

Question 36

What are the functions of mucosa in the upper respiratory tract?

Answer 36

1) mucus of goblet cells trap particulate matter2) epithelial ciliated cells filter air and carry particulate matter to the oropharynx to swallow or spit out3) warm inhaled air through goblet cells in epithelium and vessels in the lamina propria