11) Respiratory system Flashcards
What are the two parts of the respiratory tract?
The upper respiratory tract (nasal cavity, paranasal sinuses, nasopharynx) and the lower respiratory tract (larynx, trachea, bronchi, bronchioles, alveoli).
What is the primary function of the respiratory system?
To provide oxygen for cellular oxidation and remove carbon dioxide generated as a waste product of cell metabolism.
What is the difference between the conducting and respiratory portions of the respiratory system?
The conducting portion conditions and carries air to the lungs (nasal cavity, trachea, bronchi, bronchioles), while the respiratory portion is where gas exchange occurs (respiratory bronchioles, alveolar ducts, alveolar sacs, alveoli).
What functions do the components of the conducting portion of the respiratory system serve?
They warm, humidify, and filter the air to prepare it for gas exchange in the lungs.
What type of epithelium lines the conducting portion of the respiratory system?
Pseudostratified columnar epithelium with cilia and goblet cells, which secrete mucus to trap particles.
What is the structure of the trachea?
The trachea has C-shaped hyaline cartilage rings, a pseudostratified ciliated epithelium, goblet cells, and smooth muscle (trachealis) to control its diameter.
What are the three histological layers of the trachea?
1) Mucosa: pseudostratified ciliated epithelium and goblet cells,
2) Submucosa: serous glands,
3) Adventitia: dense connective tissue with hyaline cartilage.
How does the bronchus differ from the trachea?
The bronchus has irregular cartilage plates (not rings), smooth muscle, and a smaller diameter compared to the trachea. It also has a pseudostratified ciliated epithelium.
What are the main branches of the bronchial tree?
Primary bronchi → secondary bronchi → tertiary bronchi → terminal bronchioles.
What is the histology of bronchioles?
Bronchioles are lined with ciliated columnar epithelium that becomes cuboidal as they get smaller. They do not have cartilage, and goblet cells are replaced by Clara cells.
What is the function of Clara cells in the bronchioles?
Clara cells secrete glycoproteins that protect the bronchiolar epithelium and have an anti-inflammatory role.
Where does gas exchange occur in the respiratory system?
Gas exchange occurs in the alveoli, which are out-pockets of the respiratory bronchioles, alveolar ducts, and alveolar sacs.
What are the key features of alveoli?
Alveoli have simple squamous epithelium, are covered by capillaries, and are the site of gas exchange. They are lined with type 1 and type 2 pneumocytes.
What is the function of type 1 pneumocytes in the alveoli?
Type 1 pneumocytes form part of the thin barrier for gas diffusion and cover 95% of the alveolar surface.
What is the function of type 2 pneumocytes?
Type 2 pneumocytes secrete surfactant, which reduces surface tension in the alveoli and prevents their collapse during expiration.
