Respiratory Histology Hardest Trivia Quiz

This is not an activity that occurs in the nasal cavity. Gas exchange between air and blood occurs in the alveoli of the lung.

This is the correct answer because gas exchange does not occur at the level of the terminal bronchioles.

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.

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.

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.

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.

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.

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.

Type II pneumocytes are not phagocytic cells. Alveolar macrophages phagocytose particulates that erach the alveoli.

Clara cells are NOT found in association with alveoli. Clara cells are found within the epithelium of bronchioles.

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.

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.

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).

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.

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.

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.

Alveolar capillaries, like all continuous capillaries, possess a basal lamina, which lies between the endothelial cells of the capillaries and the Type I pneumocytes

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.

Elastic fibers are found throughout the respiratory tract, both in the conducting and gas exchange portions.