BIOL-2230 Lecture Notes - Lecture 15: Pleural Cavity, Serous Membrane, Bronchiole
Thursday, March 15, 2018
1
BIOL 2230: Anatomy II, Test 3 (Lecture 15, Respiratory
System)
Lungs
- The left lung is smaller than the left
- Hilum
• Indent where blood vessels, bronchi, lymphatic vessels, and nerves enter the lung
- Pleural cavities
• Area where the lungs reside
• Lined with serous membrane
- Cardiac notch
• The concave portion of the left lung that accommodates the heart
- Lobes
• The left lung has 2 lobes
- The superior and inferior lobes
- Separated by the oblique fissure
• The right lung has 3 lobes
- Separated by the oblique and horizontal fissure
- Alveoli (alveolar sacs)
• The respiratory bronchioles house the alveoli
• Alveoli are the structure involved in gas exchange
• The alveoli would be one grape while the alveolar sacs would be the bunch
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Thursday, March 15, 2018
2
Alveolar Structure
- Type I cells
• Super thin
• Make up the wall of the alveoli as squamous epithelium
- Pulmonary capillaries
• Make up the external surface (look like a cobweb)
- Respiratory membranes
• The pulmonary capillaries and Type I cells make up the respiratory membrane
• Blood flow is on one side, and gas flow on the other side
- Type II cells
• Scattered between Type I cells and secrete surfactant and antimicrobial proteins
• The surfactant will coat gas-exposed surfaces
- Alveolar pores
• Connect alveoli to help equalize air pressure in the lungs
- Alveolar macrophages
• Crawl on the alveolar surface for protection
- Dead/diseased macrophages sweep into the pharynx for disposal
Pleurae
- Double-layered serous membrane
• Parietal pleura covers the thoracic wall and diaphragm.
- Goes in between the lungs
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Thursday, March 15, 2018
3
• Visceral pleura covers the external lung surface
• Pleural cavity is between these two membranes
• Pleural fluid is what fills the cavity. The fluid is used to reduce friction during
breathing
Pulmonary Ventilation
- Inspiration: Air into the lungs
- Expiration: Gas exits the lungs
- Regulated by:
• Pressure (all types)
• Volume
• Resistance (friction)- inverse relationship
• Surface tension of the alveoli
- H20 wants alveoli to be very small in size
• Surfactant prevents alveoli from collapsing due to surface tension
• Compliance
- Change in lung volume and pressure
- High lung compliance leads to easy expansion of the lungs
• Determined by flexibility of lung tissue and alveolar surface tension
Pressures
- Atmospheric pressure is the pressure exerted by air on the body
• Typically about 1 atm
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