Lecture 12 Flashcards
What are the main structures of the lower respiratory tract? What is the main overall function of these?
Trachea, bronchi, bronchioles and alveoli.
Overall they complete the cleaning, warming and humidification of inhaled air and transport it to the alveoli, where gas exchange occurs.
What is the structure and function of the trachea?
Structure: Rigid tube which extends from the larynx to the primary bronchus, has respiratory mucosa lining with C shaped cartilages (layered as cartilage, smooth muscle to mucosa) which are shut by the trachealis, a smooth muscle on the posterior aspect.
The trachea is anterior to the oesophagus.
Function: Maintains open(patent) airway for conduction of air, cleans, warms and humidifies inhaled air. Also has cilia which form the mucociliary escalator, which will remove debris to the pharynx, which redirects it to the stomach.
What does smoking do to lung function?
Inhibits and destroys the tracheal cilia, this means coughing becomes the only way to clear the respiratory system of mucus.
What is the general location of parts of the lungs relative to each other?
Lungs laterally, heart and pulmonary veins and arteries medially. Apex of the lung is the pointy part superiorly, base is the inferior more flat part. The costal surface of the lungs is the surface which faces the ribs.
Which primary bronchus is larger? Why? What is the middle point called?
The primary bronchi are seperated by the carina into the left and right primary bronchus, the right one is larger, this means inhaled food is more likely to end up in the right one and ensures at least one side of the lungs is functioning.
What is the branching pathway of the bronchiol tree? What does this mean about the surface area?
Trachea diverges into primary bronchi, these branch into the secondary (lobar) bronchi, which branch into the tertiary (segmental) bronchi ( >1mm), bronchioles (
What part of the bronchi branches into the two seperate lungs? Where do they start?
The primary bronchi, they start outside the lungs.
What is the pattern for cartilage and smooth muscle as the bronchi get smaller?
As the bronchi get smaller smooth muscle starts to make up more of the outside than the cartilage. Smooth muscle disappears once we reach the air exchange zone.
Describe the anatomy of the lungs.
Right and left lungs situated within different (right and left) pleural cavities, apex is superior (near the clavicle), base is inferior, sitting on diaphragm. The costal surface is the outer surface and is against the ribs, the medial aspect is known as the hilum is where structures enter/exit.
The right lung has 3 lobes seperated by two fissures.
The left lung has 2 lobes seperated by one fissure.
What part of the lungs is the respiratory zone? Describe these.
Alveolar sacs are arranged in bundles which contain many alveoli, these alveoli make up most of the lung volume and the walls of these are composed of a single layer of thin flattened epithelial cells with a thin basal lamina layer around them.
They are ‘pocket like’ being open at one side and are made up of primarily type I and II pneumocytes
On their external surface is a fine network of pulmonary capillaries, these three parts (capillaries, alveoli and basal lamina) comprise the respiratory membrane (blood-air barrier), through which gas exchange occurs by simple diffusion.
What are type I and II pneumocytes? Describe their relationship. What other cells can we find?
These are lung epithelial cells. Type I are squamoud epithelial cells, type II are cuboidal, surfactant-secreting cells)
The type II are rarer, being scattered around the type I cells.
Surfactant is a complex glycolipid/phospholipid that acts to reduce the surface tension of the alveolar fluid.
Macrophages can also be found in the lungs.
What is lower respiratory tract epithelium? What does it rest on and what do they secrete?
Respiratory mucosa (pseudostratified, ciliated, columnar epithelium containing many goblet cells. It rests on a lamina propria (a thin layer of loose connective tissue, or dense irregular connective tissue), the mucous cells secrete mucus and serous glands secrete a watery fluid containing enzymes. they also secrete lysozyme and defensins.
What are the structural changes as you get lower in the respiratory tract?
Epithelium gets much thinner, containing less cells.
