Question

A possible explanation for a smoker cough that develops when the tracheal epithelium changes from pseudostratified columnar to stratified squamous is that
A. This change is accompanied by tumours that irritate the upper respiratory tract.
B. Stratified squamous epithelium secretes more mucin than pseudostratified columnar
C. The stratified squamous epithelium has no cilia to remove accumulating mucus
D. The two events are unrelated

Answer 1

The skin constantly protects humans from external irritants and pathogens. Similarly, the respiratory epithelium effectively protects and helps clear respiratory airways and lungs from external pathogens and irritants. As humans breathe in air, the functions of the respiratory system are to persistently filter out allergens, inhaled pathogens, to prevent inflammation.

Step by step answer: Epithelial tissues are avascular types of tissues. They comprise cells that have a minuscule extracellular matrix and are connected by strong intercellular adhesions. Epithelial tissue is arguably present on almost every portion of the human body. Several functions of these tissues include sensation, absorption, protection, and secretion. The movement of substances entering or leaving any tissue or organ is either facilitated or inhibited by the epithelium as these substances must pass through it. This makes the epithelium the selective barrier. The epithelium is evidently present in the respiratory system. In the respiratory system, the portion from the nasal cavity to the bronchi is lined by the pseudostratified columnar ciliated epithelium. Among this, the bronchioles are lined by simple columnar epithelium and the cuboidal epithelium. The alveoli are lined by a thin layer of squamous epithelium, which allows for the passage of gas. The respiratory tree’s trunk is known as the trachea, which is lined by the ciliated pseudostratified columnar epithelium. Hair-like projections called cilia are present in the bronchus of the lungs and facilitate the movement of microbes out of the airway. Ciliated cells, goblet cells and basal cells are three vital cell types involved in respiratory epithelium. Goblet cells release mucus. The upper airways and the respiratory tract are extensively lined with ciliated pseudostratified columnar epithelium.
The pseudostratified columnar epithelia’s function includes secretion, absorption and transportation. They have cilia present which facilitates the movement of microbes out of the airway. They consist of a single-cell layer but appear as though they have multiple layers. This is due to the presence of cell nuclei at different levels.
Stratified squamous epithelium is a type of epithelium present in organ systems that are in close contact with the external environment. For instance, skin, respiratory, reproductive, excretory and digestive systems. Their functions include protecting the body from water loss and desiccation. Stratified squamous epithelium embodies the skin’s outermost layer and the inner lining of the vagina, oesophagus and mouth. Some sources debate that the stratified squamous epithelia are limited to the oesophagus of the human foregut.
Everything that enters into the respiratory airway passes through the epithelium. Therefore, any external pathogens, allergens and cigarette smoke that enters through the airways can cause inflammation of the epithelium. The epithelium functions to protect the lungs from the adverse effects of the smoke. These functions can be altered due to a result of smoking abuse. This could result in the alterations or mutations of the cells of the ciliated pseudostratified columnar epithelium. Smoker cough is developed when the tracheal epithelium changes from ciliated pseudostratified columnar epithelium to stratified squamous epithelium. Squamous epithelium lacks the presence of cilia that facilitates both the movement of microbes and mucus up and out the airway. Therefore, the mucus produced by the goblet cells accumulates in the trachea inducing smoker cough.
Hence option C is correct.

Note: The supreme causative factor of COPD is smoking. COPD is a chronic obstructive pulmonary disease and is reported to be the fourth most common cause of death in the United States of America. Up to 30,000 deaths are reported per year in the United Kingdom and an estimate of over one million individuals suffer from COPD.