Idiopathic pulmonary fibrosis

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Idiopathic pulmonary fibrosis

Respiratory system

Apnea and hypoventilation

Apnea of prematurity

Sleep apnea

Pleura and pleural space disorders


Pleural effusion



Idiopathic pulmonary fibrosis


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USMLE® Step 1 questions

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High Yield Notes

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Idiopathic pulmonary fibrosis

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USMLE® Step 1 style questions USMLE

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A 52-year-old man presents to the clinic with a dry cough and shortness of breath. He reports worsening symptoms for months and states he is otherwise healthy and does not take any medications daily. He usually drinks two beers everyday after he finishes his work as a sandblaster for the city government. Vitals are within normal limits. His physical examination is unremarkable. He undergoes spirometry which demonstrates an increased FEV1/FVC ratio. Which of the following radiographic features is most likely to be observed based on this patient’s clinical presentation?  

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Idiopathic pulmonary fibrosis p. 700


Idiopathic pulmonary fibrosis can be broken down into idiopathic which means a disease without a known cause or mechanism, pulmonary which refers to the lungs, and fibrosis which refers to excess collagen in connective tissue, or interstitial tissue between cells, usually after tissue damage.

So idiopathic pulmonary fibrosis is the ongoing repair process of having excess collagen or scar tissue in the interstitial tissue of the lung.

What triggers the repair process is unknown, but it’s a chronic process that leads to a progressive loss of lung tissue.

Normally, gas exchange happens between the alveoli which carry air and capillaries which carry blood.

The alveoli are lined by type I and type II alveolar epithelial cells, also called type I and type II pneumocytes.

Type I pneumocytes make up the majority of cells - they’re simple squamous cells that form a nearly continuous barrier between the air and underlying connective tissue.

Type II pneumocytes are studded throughout the type I - they’re shaped like cubes, have microvilli to sweep away invading particles, and secrete surfactant, an oily mixture of proteins, phospholipids, and neutral lipids which prevent the alveoli from collapsing during exhalation.

Type II pneumocytes also have the ability to divide to make more type II pneumocytes and can also divide and become type I pneumocytes as well.

Now, between the type I and type II pneumocytes and the capillaries is interstitial tissue of the lung, which has macrophages and fibroblasts.

When the alveolar lining is damaged, type I pneumocytes release transforming growth factor beta1, which gets the type II pneumocytes to stimulate fibroblasts to proliferate and develop into myofibroblasts, which are fibroblasts with some smooth muscle cell properties.


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