Statement A : Larger bronchioles (initial bronchioles ) are lined by simple columnar ciliated epithelium
Statement B : Smaller bronchioles lined by simple cuboidal ciliated epithelium
answer if the statements are true or false and what are larger bronchioles, smaller bronchioles
Answers
Answer:
The respiratory system is constantly filtering through the external environment as humans breathe air. The airways must maintain the ability to clear inhaled pathogens, allergens, and debris to maintain homeostasis and prevent inflammation.
The respiratory system subdivides into a conducting portion and a respiratory portion. The majority of the respiratory tree, from the nasal cavity to the bronchi, is lined by pseudostratified columnar ciliated epithelium. The bronchioles are lined by simple columnar to the cuboidal epithelium, and the alveoli possess a lining of thin squamous epithelium that allows for gas exchange.
Structure
There are four main histological layers within the respiratory system: respiratory mucosa, which includes epithelium and supporting lamina propria, submucosa, cartilage and/or muscular layer and adventitia. Respiratory epithelium is ciliated pseudostratified columnar epithelium found lining most of the respiratory tract; it is not present in the larynx or pharynx. The epithelium classifies as pseudostratified; though it is a single layer of cells along the basement membrane, the alignment of the nuclei is not in the same plane and appears as multiple layers. The role of this unique type of epithelium is to function as a barrier to pathogens and foreign particles; however, it also operates by preventing infection and tissue injury via the use of the mucociliary elevator.
The Conducting Portion
The conducting piece of the respiratory system consists of the nasal cavity, trachea, bronchi, and bronchioles. The luminal surfaces of this entire portion have a lining of ciliated pseudostratified columnar epithelium and contain goblet cells. Their role is to secrete mucus that serves as the first line of defense against incoming environmental pathogens. Cilia move the mucus-bound particulate up and away for expulsion from the body. The various types and abundance of cells are dependent on which region of the airway they are.[1]
In the most proximal airway, hyaline cartilage rings support the larger respiratory passages, namely, the trachea and bronchi, to facilitate the passage of air. Three major cell types are found in this region: ciliated, non-ciliated secretory cells, and basal cells.
Ciliated cells, each lined with 200 to 300 cilia, account for more than half of all epithelial cells in the conducting airway. As the degree of branching within the airway tree continues, the epithelium gradually changes from pseudostratified to simple cuboidal; and the predominant cells become non-ciliated cells, Clara cells.
The Gas-Exchange Portion
The respiratory or gas-exchange region of the lung is composed of millions of alveoli, which are lined by an extremely thin, simple squamous epithelium that allows for the easy diffusion of oxygen and carbon dioxide. Additionally, cuboidal, surfactant-secreting cells, Type II pneumocytes, are also found lining the walls of alveoli. Surfactant, which is primarily composed of dipalmitoylphosphatidylcholine, has a vital role in lowering the surface tension of water to allow for effective gas exchange.[1]
Type I pneumocytes are flattened cells that create a very thin diffusion barrier for gases. Tight junctions are found connecting one cell to another.[2] The principal functions of Type I pneumocytes are gas exchange and fluid transport. Type II Pneumocytes secrete surfactant, which decreases the surface area between thin alveolar walls, and stops alveoli from collapsing during exhalation. These cells connect to the epithelium and other constituent cells by tight junctions. Type II pneumocytes also play a vital role in acting as progenitor cells to replace injured or damaged Type I pneumocytes.[3]
Function
Just as the skin protects humans from external pathogens and irritants, the respiratory epithelium acts to protect and effectively clear the airways and lungs of inhaled pathogens and irritants.
The division of the respiratory system into conducting and respiratory airways delineates their function and roles. The conducting portion, consisting of the nose, pharynx, larynx, trachea, bronchi, and bronchioles, which all serve to humidify, warm, filter air. The respiratory portion is involved in gas exchange. There are three major types of cells found in respiratory epithelium, and each holds a vital role in regulating how humans breathe. If any of these components of the barrier are not properly functioning, the body becomes susceptible to acquiring infections, pathogens or inducing inflammation, and disturbing hemostasis.
Explanation:
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