USMLE Step 1 Respiratory Physiology Review 60 03 Mechanics of Breathing

USMLE Step 1 Respiratory Physiology Review 60 03 Mechanics of Breathing

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Play USMLE Audio MP3 60 03 Mechanics of Breathing Below

Begin 60 03 Mechanics of Breathing Transcription

Moving now to the mechanics of breathing. Respiratory mechanics deals with the mechanical processes necessary to effectively ventilate alveoli. It is the study of how ventilation of the lungs occurs and the factors that regulate or determine lung volume. Along with the heart, the main organs of the respiratory system are contained within a flexible bone and cartilage cage. What is this flexible cage called? It begins with the letter T.

  • The thorax is the bone and cartilage cage that contains the heart and the main organs of the respiratory system.

The lungs are located in a cavity within the thorax. What is this cavity called? It starts with the letter P.

  • The pleural cavity.

What membrane covers the outside of the lungs? The two word answer starts with V – P.

  • The visceral pleura covers the outside of the lungs.

And what membrane covers the diaphragm and lines the inside of the thorax?

  • Parietal pleura.

Between the visceral pleura and the parietal pleura there is a small potential space that contains a lubricating fluid. What is this potential space called?

  • The small potential space that exists between the visceral pleura and the parietal pleura is called the pleural or intrapleural space. The pleural space is like two sacs encasing each lung separately.

Is there communication between the two pleural sacs?

  • No. there is no communication between the pleural sacs. Unless something goes wrong, the pleural space is only a potential space.

Under normal circumstances does the pleural space contain any air?

  • No. Normally, the pleural space contains no air.

What abnormal condition is the presence of air in the pleural space? It starts with the letter P.

  • Pneumothorax is the presence of air in the pleural space.

What is the lubricating fluid within the pleural space called?

  • Pleural fluid.

What are the two apparently paradoxical functions that pleural fluid serves? One begins with an L and the other with an A.

  • Pleural fluid serves as both a lubricant and an adhesive between the lungs and the thorax. So although the outside surface of the lungs adheres to the inside of the thorax, the two pleural layers can move easily against each other during ventilation.

Student doctor please pause the tape and summarize what has been discussed about the pleural cavity, the two pleurae, the pleural space, pneumothorax, and the two functions of the pleural fluid.

The thorax is the bone and cartilage cage that contains the heart and the main organs of the respiratory system. The lungs are located in the pleural cavity. The visceral pleura is the membrane that covers the outside of the lungs. And the parietal pleura covers the diaphragm and lines the thorax. The small potential space that exists between the visceral pleura and the parietal pleura is called the pleural or interpleural space. The pleural space is like two sacs encasing each lung separately and between the two pleural sacs there is no communication. Unless something goes wrong, the pleural space contains no air. The abnormal condition, pneumothorax, is the presence of air in the pleural space. Pleural fluid serves as both a lubricant and as an adhesive between the lungs and the thorax. So although the outside surface of the lungs adheres to the inside of the thorax, the two layers can move easily against each other during ventilation.

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