Podcast
Questions and Answers
What is the total surface area of a typical pair of human lungs?
What is the total surface area of a typical pair of human lungs?
What percentage of the alveolus's surface area is covered in capillaries?
What percentage of the alveolus's surface area is covered in capillaries?
How many lobes does the right lung have?
How many lobes does the right lung have?
What is the function of the pleura?
What is the function of the pleura?
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What is the most important respiratory muscle?
What is the most important respiratory muscle?
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What happens to the size of the thoracic cavity during inspiration?
What happens to the size of the thoracic cavity during inspiration?
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What is the sequence of events during normal breathing?
What is the sequence of events during normal breathing?
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What is the function of the visceral pleura?
What is the function of the visceral pleura?
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What is the average diameter of an adult alveolus?
What is the average diameter of an adult alveolus?
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How many alveoli are present in a typical pair of human lungs?
How many alveoli are present in a typical pair of human lungs?
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Study Notes
Mechanism of Respiration (Breathing)
- Movement of air in and out of lungs occurs by changes in size of thoracic cavity and followed by lung changes.
- Changes take place by activity of a group of muscles called “Respiratory Muscles" including:
- Diaphragm (most important)
- Inter-costal muscle (less important)
- Abdominal muscles
Respiratory Muscles
- Diaphragm muscle:
- Descends 1-5 cm during quiet respiration, up to 7cm during deep respiration
- Contracts and pushes up into thoracic region, increasing length of thoracic cavity
- Relaxes and ascends, decreasing length of thoracic cavity
- External intercostal muscles:
- Contract, raising ribs and increasing transverse diameter of thorax
- Relax, passing downwards and forwards from their articulation
- Internal intercostal muscles:
- Relax, passing downwards and forwards from their articulation
- Contract, pulling ribs downwards and decreasing transverse diameter of thorax
- Abdominal muscles:
- Relax, pushing abdominal contents down
- Contract, pushing abdominal contents up and into inside (regaining tone)
Volume of Respiratory Air
- Measured by "Spirometer"
- Types of volumes:
- Tidal air volume (TV): 500 ml (C.C.)
- Inspiratory Reserve volume (IRV): 3000 ml (C.C.) = 3 liter
- Expiratory Reserve volume (ERV): 1200 ml
- Residual air volume (RV): 1200 ml (can't be measured by spirometer)
Lung Capacity
- Total Lung Capacity: 6000mL = 6 Liter (TV + IRV + ERV + RV)
- Functional Residual Capacity: 2-3 liter (ERV + RV)
- Inspiratory capacity: 3500 ml (TV + IRV)
- Expiratory Capacity: 1700 ml (TV + ERV)
- Vital capacity: 4700 ml (TV + IRV + ERV)
Factors affecting vital capacity
- Condition of respiratory muscles
- Elasticity of lung
- Posture of body
- Expansion and recoil of thoracic cage
- Volume of blood in pulmonary circulation
- Resistance to air flow in respiratory passage
Lungs
- Paired organs in the chest that perform respiration
- Right lung has 3 lobes and 2 fissures, while the left has 2 lobes and 1 fissure
- Each alveolus has an average diameter of 200 micrometres, increasing during inhalation
- 700 million alveoli, producing 70m2 of surface area
- Alveoli are wrapped in a fine mesh of capillaries covering about 70% of its area
The Pleura
- Thin double membrane: fibro-elastic and invest lung
- Parietal pleura: lined on outside lung by simple squamous epithelium
- Visceral pleura: lined on inside lung by simple squamous epithelium
- Separated by thin film of fluid for lubrication of sliding movements
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Description
This quiz assesses understanding of the diaphragm and its movements during respiration, including contraction and relaxation. It covers the role of the diaphragm in breathing and the changes in the thoracic cavity.
