TBL10 - Conducting Airways

Question 1

What are the distal parts of the air-conducting portion of the respiratory system?

Answer 1

The trachea, bronchi, and bronchioles are distal parts of the air-conducting portion of the respiratory system

Question 2

What are 3 important functions of conducting airways before air can reach the alveolar sacs? What is epithelium of the trachea and bronchi called? What are two key components of connective tissue underlying the respiratory epithelium?

Answer 2

1) Conducting airways contribute to moistening, warming, and filtering of inspired air before it reaches the alveolar sacs
2) Epithelium of the trachea and bronchi is called respiratory epithelium
3) Connective tissue underlying the respiratory epithelium contains a dense microcirculation and glandular acini that secrete mucus onto the apical surface of the epithelium

Question 3

What two types of cells does respiratory epithelium contain? What do they contain?

Answer 3

Respiratory epithelium contains basal cells and tall columnar cells, which are either ciliated or filled with mucus to become goblet cells i.e., cells shaped like goblet glasses

Question 4

Where is mucus secreted in respiratory epithelium? What is its function?

Answer 4

1) Ducts of the glands in the lamina propria open onto the luminal surface
2) Mucus secreted onto the apical surface of the respiratory epithelium creates a sticky layer that entraps inspired particulate matter

Question 5

What allows mucus to move along the respiratory epithelium? What stimulates and inhibits mucus production?

Answer 5

1) Motile cilia move the mucus layer along the apical surface toward the oral cavity for elimination or swallowing
2) Parasympathetic and sympathetic fibers of the pulmonary plexuses stimulate and inhibit mucus production, respectively

Question 6

What is the respiratory mucosa characterized by?

Answer 6

The respiratory mucosa is characterized by longitudinal folds formed by dense collections of longitudinally oriented elastic fibers in the lamina propria

Question 7

What prevents the collapse of airways during respiration? Recognize the C-shaped cartilaginous rings external to the mucosa and longitudinal elastic fibers cut in the lamina propria.

Answer 7

Trachea and main bronchi contain 16-20 C-shaped rings of hyaline cartilage that prevent collapse of the airways during respiration

Question 8

What spans the posterior ends of the cartilaginous rings of the respiratory tract? What is the function of this structure?

Answer 8

1) The trachealis muscle (bundles of smooth muscle fibers) spans the open posterior ends of the cartilaginous rings
2) During forced expiration (e.g., coughing or sneezing), the trachealis contracts to prevent the rings from flaring open posteriorly

Question 9

Where do the respiratory epithelium and mucous glands extend to? What type of connective tissue is found in the lobar bronchi? Where do these structures terminate?

Answer 9

1) Respiratory epithelium and the mucous glands extend into the lobar and segmental bronchi
2) In the lobar bronchi, hyaline cartilage is organized as discontinuous plates
3) The plates become progressively smaller and terminate in the distal ends of the segmental bronchi

Question 10

What do bronchioles lack? What lies external to the bronchiolar mucosa? Where does the circumferential smooth muscle layer begin? What does it function in?

Answer 10

1) Bronchioles lack cartilage and mucous glands
2) A circumferential layer of smooth muscle resides external to the bronchiolar mucosa
3) The circumferential smooth muscle layer begins in the lobar bronchi
4) It functions in bronchoconstriction and bronchodilation

Question 11

What is the functional relevance of the histological observation that bronchioles lack goblet cells and mucous glands? (Check if this is correct)

Answer 11

1) Alveolar gas exchange would be impeded by the presence of mucus
2) Instead of having mucous glands and goblet cells to produce mucus, bronchioles contain clara cells to breakdown mucus that comes from the upper respiratory tract
3) This prevents mucus from entering the alveoli and hindering gas exchange

Question 12

What is the pathogenesis of asthma?

Answer 12

1) Asthma is a disorder characterized by a heightened response of the tracheobronchial tree to numerous stimuli
2) Pathologic features include mucosal and submucosal edema in bronchi and bronchioles, thickening of the basement membrane, hypertrophy of smooth muscle, and profuse infiltration of leukocytes, chiefly eosinophils

Question 13

What type of fibers reside in the tracheal mucosa? How are these fibers arranged?

Answer 13

1) Elastic fibers reside in the tracheal mucosa

2) The longitudinally oriented meshwork of elastic fibers extends distally into the walls of the pulmonary alveoli

Question 14

How do elastic fibers in lobar and segmental bronchi, bronchioles, and stroma of the interalveolar septa contribute to normal respiration? (Check if this is right)

Answer 14

1) Elastic fibers allow for expansion during inspiration and elastic recoil during expiration
2) Elastic fibers are embedded in circumferential smooth muscle within lobar and segmental bronchi as well as in bronchioles, which assists in bronchoconstriction and bronchodilation

Question 15

What type of cells line the bronchioles? What are Goblet cells of the respiratory epithelium replaced by?

Answer 15

1) Simple columnar epithelium (i.e., column-shaped cells often ciliated) lines the bronchioles
2) Goblet cells of the respiratory epithelium are replaced by Clara cells

Question 16

Define functions of the Clara cells

Answer 16

1) The SER is believed to play a role in detoxification, because Clara cells can detoxify many inhaled noxious substances such as nitrogen dioxide
2) Clara cells also secrete a surfactant-like protective material that coats the bronchiolar epithelial surface; proteolytic enzymes that break down mucus produced in the upper tracheobronchial tree; a leukocyte protease inhibitor that may be important in maintaining the integrity of the bronchiolar epithelium; and lysozymes
3) These cells are involved in transport of water and electrolytes, especially release of chloride ions
4) They act as progenitor (stem) cells for normal renewal of nonciliated and ciliated bronchiolar epithelial cells, particularly in response to injury

Question 17

Where do pulmonary arteries and veins travel in relation to the respiratory tract?

Answer 17

1) Branches of the pulmonary arteries are closely aligned with the bronchi and bronchioles
2) The pulmonary veins course toward the hilum in thin sleeves of connective tissue independent of the airways

Question 18

How are thin-walled arteries and veins distinguished in histological images?

Answer 18

The thin-walled arteries and veins are distinguished in histological images by their locations rather than differences in thickness of their circumferential smooth muscle layers

Question 19

Are the two designated blood vessels arteries or veins?

Answer 19

No idea

Question 20

What is the lamina propria? What is designated as the mucosa?

Answer 20

1) Connective tissue underlying an epithelium that lines a lumen is generically called lamina propria
2) The lamina propria plus the epithelium are generically designated the mucosa