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Respiratory System Cheat Sheet (DRAFT) by

This is a cheatsheet for the respiratory system

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Vocabulary

Respir­atory Airways - tubes that carry air between the atmosphere and the alveoli.
Conducting zone - top of the trachea to the respir­atory bronch­ioles, provides a low-re­sis­tance pathway for airflow.
Respir­atory Zone - where the gas exchange occurs.
Total Alveolar Surface - large surface that enables rapid exchange of large quantities of O2 and CO2 by DIFFUSION.
Type I cells - form the walls of the aveoli
Type II cells - secrete a pulmonary surfactant that acts to reduce surface tension of water INSIDE the alveoli.
Surfactant - reduces cohesive forces between water molecules on alveolar surface. This lowers the surface tension -> increases lung compliance and makes it easier to expand lungs.
Surface Tension - tendency of liquid surfaces at rest to shrink into the minimum surface area possible.
Pleural Sacs - pair of thin, fluid-­filled, membranes that enclose the lungs. Parietal pleura and Visceral pleura make up the sacs.
Pleural Cavity - space between the pleural sacs, is filled with intrap­leural fluid.
Pressure Gradient - Air tends to move from an area of higher pressure to an area of lower pressure
Atmosp­heric Pressure - pressure exerted by the weight of the gas in the atmosphere on objects on Earth's surface (760 mm Hg at sea level).
Intra-­alv­eolar Pressure - pressure within the alveoli
Intrap­leural Pressure - pressure within the pleural sac
Boyle's Law - at a constant temper­ature, the pressure of gas varies INVERSELY with its volume.
Transmural Pressure Gradient = intra-­alv­eolar pressure - intrap­leural pressure
Pneumo­thorax - air enters the pleural cavity, transmural pressure gradient is lost and lungs collapse.
Passive Expiration - ribs, sternum, and diaphragm return to resting position upon relaxation of inspir­atory muscles.
Active Expiration - CONTRA­CTION of abdominal muscles. Diaphragm is pushed upwards. Contra­ction of internal interc­ostal muscles flatten the ribs and sternum. REDUCES the size of the thoracic cavity.
Elastin - protein which facili­tates the stretching and recoiling of struct­ures.
Pulmonary Ventil­ation - volume of air breathed in/out per minute.
Pulmonary Ventil­ation - volume of air breathed in/out per minute.
Gas Transport - process by which O2 and CO2 are transp­orted between the systemic tissues and the lungs
 

Respir­atory Mechanics

During INSPIR­ATION, Palv < Patm
During EXPIRA­TION, Palv > Patm
Remember BOYLE'S LAW: pressure and volume are inversely related so as the volume decreases the pressure will increase
Example: Inspir­ation: 1. the thoracic wall expands 2. the lungs expand 3. Boyle's law: Palv decreases
4 Pressures Important for Ventil­ation
1. Atmosp­heric Pressure - serves as a reference point for pressure changes
2. Intra-­alv­eolar Pressure - changes during breathing, is a factor that drives air movement
3. Intrap­leural Pressure - helps prevent lung collapse
4. Transmural Pressure Gradient - pushes out on lungs and stretches them to fill the larger thoracic cavity

What is Pneumo­thorax?

- extremely dangerous: occurs when air is allowed to enter the plural cavity
- can occur either by a puncture wound to the chest or a hole in the lung
- RESULT: transmural pressure gradient LOST, lungs and thorax separate and assume own dimensions
- THIS MEANS: 1. lungs collapse - air in pleural space removes suction that keeps inflation -> recoil and collapse AND 2. Thoracic wall expands - no lung pull = chest wall recoils on its own

Inspir­ation and Expiration

Inspir­ation
Expiration
- The diaphragm CONTRACTS -> INCREASES vertical dimensions of thoracic cavity
- PASSIVE expira­tion: ribs, sternum, and diaphragm return to RESTING position upon RELAXATION of inspir­atory muscles
- External interc­ostal muscles CONTRACT = ELEVATED rib cage
- ACTIVE expira­tion: abdominal muscles CONTRACT -> diaphragm pushes upwards = reduction vertical dimension of thoracic cavity

Inspir­ation and Expiration

Inspir­ation
Expiration
- The diaphragm CONTRACTS -> INCREASES vertical dimensions of thoracic cavity
- PASSIVE expira­tion: ribs, sternum, and diaphragm return to RESTING position upon RELAXATION of inspir­atory muscles
 

What is Surfactant

- Surfac­tant: reduces COHESIVE forces between water molecules on alveolar surface. Lowers the SURFACE TENSION = INCREASE lung compliance
- Secreted by type II alveolar cells
- Effect is GREATER in smaller alveoli
- Deep breath increases secretion by stretching type II cells
- Concen­tration DECREASES when breaths are SMALL