1.
Emphysema is associated with defects in the function of:
Correct Answer
D. Elastic fibers
Explanation
Emphysema is associated with destruction of elastic fibers by the enzyme elastase. Elastase is normally released by macrophages in the lungs. This elastase is normally kept under control by the inhibitor alpha1-antitrypsin. However, stimuli which inhibit alpha1-antitrypsin or stimuli that increase the amount of elastase (for instance influx of neutrophils, which also secrete elastase, into the lung) then the elastase can overwhelm the elastase inhibitor and result in destruction of elastic fibers.
2.
Which of the following portions of the respiratory tract lack smooth muscle?
Correct Answer
E. Alveoli
Explanation
Alveoli lack any smooth muscle and hence is the correct answer for this question. The trachea has a bundlke of smooth muscle cells (trachealis muscle) spanning the open side of the C-shaped cartilages. Bronchi and bronchioles have spiraling bundles of smooth muscle cells. Even alveolar ducts can have a few smooth muscle in small knobs (covered by epithelium) at the jucntions between outpocketing of alveoli.
3.
All of the following are characteristics of capillaries found within the alveolar septa EXCEPT:
Correct Answer
E. They lack a basal lamina
Explanation
Alveolar capillaries, like all continuous capillaries, possess a basal lamina, which lies between the endothelial cells of the capillaries and the Type I pneumocytes
4.
A unique feature of the olfactory epithelium is the presence of:
Correct Answer
B. Neurons that are replaced throughout life
Explanation
This is indeed a unique feature of the olfactory epithelium, which is a sensory epithelium in which the actual sensory receptor cells are bipolar neurons located within this pseudostratified epithelium. Unlike most other neurons in the human body, these sensory bipolar neurons can be replaced throughout adult life.
5.
Which of the following statements about the respiratory tract is true?
Correct Answer
D. As one moves from the beginning to the end of the brochiolar tree, Goblet cells disappear before ciliated cells disappear
Explanation
This is a true statement and reflects an important concept. The action of the cilia on ciliated epithelial cells is necessary to move the mucus (secreted byt he goblet cells) upwards through the airways to the oro-pharynx, where it can be swallowed and thus disposed of in the digestive tract. To insure that mucus from goblet cell secretions does not accumulate in the respiratory tract, the goblet cells disappear before the ciliated epithelial cells disappear (as you go deeper into the airway system). Both of these cell types disappear at the level of the bronchioles.
6.
Larynx, trachea, bronchi, bronchioles and alveolar septa have which of the following in common:
Correct Answer
D. Elastic fibers
Explanation
Elastic fibers are found throughout the respiratory tract, both in the conducting and gas exchange portions.
7.
All of the following represent cells involved in the protective mechanisms of the respiratory tract EXCEPT:
Correct Answer
E. Type I pneumocytes
Explanation
Type I pneumocytes are very flattened squamous cells that provide a lining for the alveoli but do not perform any secretory or phagocytic functions that play a direct role in protection of the respiratory tract.
8.
Respiratory epithelium and olfactory epithelium are alike in which of the following properties?
Correct Answer
B. Both are pseudostratified epithelia
Explanation
Although the olfactory epithelium is different in terms of having bipolar sensory neurons, both the olfactory epithelium and the "respiratory epithelium) are true pseudostratified columnar epithelium.
9.
Which of the following is NOT involved in gas exchange?
Correct Answer
A. Terminal bronchioles
Explanation
This is the correct answer because gas exchange does not occur at the level of the terminal bronchioles.
10.
All of the following cells are found associated with alveoli EXCEPT:
Correct Answer
C. Clara cells
Explanation
Clara cells are NOT found in association with alveoli. Clara cells are found within the epithelium of bronchioles.
11.
All of the following are characteristics of Type II pneumocytes EXCEPT:
Correct Answer
C. pHagocytize particulates reaching the alveoli
Explanation
Type II pneumocytes are not phagocytic cells. Alveolar macrophages phagocytose particulates that erach the alveoli.
12.
Which of the following is NOT a significant activity of the nasal cavity?
Correct Answer
C. Absorption of oxygen into blood
Explanation
This is not an activity that occurs in the nasal cavity. Gas exchange between air and blood occurs in the alveoli of the lung.
13.
In order for oxygen in the inspired air to reach hemoglobin, it must diffuse across all of the following structures EXCEPT:
Correct Answer
D. One or more smooth muscle cells
Explanation
The very thin alveolar wall or septum does not contain any smooth muscle cells and thus oxygen does not have to diffuse across smooth muscle cells in order to reach hemoglobin AND capillaries do not have smooth muscle.
14.
In order for oxygen to diffuse from the alveolar air spaces to the site of its binding to hemoglobin, it must diffuse across how many plasma membranes?
Correct Answer
D. 5
Explanation
The minimum gas diffusion barrier in the alveolar septum includes the highly flattened cytoplasm of a Type I pneumocyte, the fused basement membrane, the highly flattened cytoplasm of an endothelial cell making up the capillary wall, the blood plasma and finally the plasma membrane of the erythrocyte. There is a plasma membrane on each side of the flattened Type I pneumocyte and each side of the flattened endothelial cell. Therefore, there are a total of five (5) plasma membranes that must be crossed in order for the oxygen molecule to diffuse from the alveolar air space to the hemoglobin inside the cytoplasm of the erythrocyte (RBC). Two contributed by the Type I cell, 2 contributed by the endothelial cell and one by the erythrocyte.
15.
There are some interesting similarities and contrasts in the structural organization of the glomerular filtration barrier versus the alveolar gas diffusion barrier. In this regard, which of the following is NOT a true statement?
Correct Answer
C. Alveolar capillaries have a smaller diameter and a higher hydrostatic pressure than glomerular capillaries
Explanation
Alveolar capillaries are larger diameter than most other capillaries and have a high flow but low resistance and low hydrostatic pressure because one does not want to force fluid out of these capillaries into the alveolar air spaces. On the other hand, one wants to have high resistance and high hydrostatic pressure in the glomerular capillaries since the point of the glomerulus is to force fluid out of the capillaries and into the Bowman's (urinary) space in order to create the initial kidney filtrate.
16.
Which of the following statements about the respiratory system is not correct?
Correct Answer
B. Elastic fibers are absent from alveoli
Explanation
Elastic fibers play an important role in the alveoli and are found in the alveolar septa. They help reduce the diameter of the alveoli during exhalation and hence helps to minimize the volume of the "anatomical" dead space.
17.
Smoking can lead to emphysema through a decrease in the activity of which one of the following?
Correct Answer
D. α1-antitrypsin
Explanation
Components of smoke can inactivate the natural inhibitors (such as α1-antitrypsin) of elastase and hence result in an increase in elastase activity and hence increased damage to elastin in the respiratory system. Smoking can also lead to migration of neutophils into the respiratory system contributing an additional source of elastase (beyond that secreted by the alveolar macrophages).
18.
The diameter of bronchioles is regulated by ________ while the length of bronchioles can be regulated by ________.
Correct Answer
A. Smooth muscle; elastic fibers
Explanation
The diameter of bronchioles is regulated by smooth muscle, which can contract or relax to control the size of the airways. On the other hand, the length of bronchioles can be regulated by elastic fibers, which provide flexibility and allow the bronchioles to expand or contract as needed.
19.
Infant Respiratory Distress Syndrome (also called Hyaline Membrane Disease) results from the lack of function of which of the following cell types in the lung?
Correct Answer
B. Type II pneumocyte (Type II alveolar cell)
Explanation
Infant or neonatal Respiratory Distress Syndrome (Hyaline Membrane Disease) is a result of the lack of production of surfactant in the alveoli of the lung. Surfactant reduces surface tension and reduces the energy necessary to inflate the alveoli during inhalation. Surfactant is produced by the Type II pneumocytes (also called Type II alveolar cells or foam cells) associated with the alveolar septa. If neonates are born prematurely, the Type II cells may not have matured enough to be producing and secreting sufficient surfactant. Type I pneumocytes (Type II alveolar cells) are squamous cells that create most of the lining of the alveolar lumen. Their morphology is designed to help minimize gas diffusion distances. The tight junctions between these cells help prevent entry of fluid into the air spaces of the alveoli. Clara cells are found within the epithelium of bronchioles and assist in detoxification of gases as well as secreting certain substances to coat the bronchiolar epithelium. Goblet cells are found in the respiratory epithelium lining the trachea and bronchi and the mucus they secrete into the airways assists in the process of mucociliary clearance.