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Questions and Answers
Explain how the contraction of the diaphragm and external intercostal muscles leads to air entering the lungs during inspiration.
Explain how the contraction of the diaphragm and external intercostal muscles leads to air entering the lungs during inspiration.
Contraction of these muscles increases the volume of the thoracic cavity, decreasing intra-alveolar pressure. This creates a pressure gradient that allows air to flow into the lungs from an area of higher pressure to lower pressure.
Describe the roles of the diaphragm and external intercostal muscles during inspiration.
Describe the roles of the diaphragm and external intercostal muscles during inspiration.
The diaphragm contracts and moves downwards, expanding the lung bases. The external intercostals contract, lifting the rib cage up and out. Both actions increase thoracic volume.
How does Boyle's Law relate to the process of breathing?
How does Boyle's Law relate to the process of breathing?
Boyle's Law states that at constant temperature, volume and pressure are inversely proportional. During inspiration, increasing the volume of the thoracic cavity decreases pressure, drawing air in. During expiration, decreasing the volume increases pressure, forcing air out.
Explain why patients with a large bowel obstruction may find it difficult to breathe.
Explain why patients with a large bowel obstruction may find it difficult to breathe.
Describe the mechanics of passive expiration, including the roles of the diaphragm and elastic recoil.
Describe the mechanics of passive expiration, including the roles of the diaphragm and elastic recoil.
Explain why individuals with advanced neuromuscular disease might require ventilatory support.
Explain why individuals with advanced neuromuscular disease might require ventilatory support.
List three accessory muscles involved in active breathing and describe their roles.
List three accessory muscles involved in active breathing and describe their roles.
How does the pressure within the thoracic cavity change during inspiration and expiration, and why is this important?
How does the pressure within the thoracic cavity change during inspiration and expiration, and why is this important?
Explain the difference between passive and active expiration. Under what circumstances might active expiration be necessary?
Explain the difference between passive and active expiration. Under what circumstances might active expiration be necessary?
What two factors reduce the intrathoracic volume during expiration?
What two factors reduce the intrathoracic volume during expiration?
In the context of breathing, what is ventilation?
In the context of breathing, what is ventilation?
Explain why a patient with motor neurone disease might experience hypercapnia.
Explain why a patient with motor neurone disease might experience hypercapnia.
What anatomical structures are involved in ventilation?
What anatomical structures are involved in ventilation?
According to Boyle's Law, what happens to the pressure of a gas if the volume of its container is doubled, assuming constant temperature?
According to Boyle's Law, what happens to the pressure of a gas if the volume of its container is doubled, assuming constant temperature?
During inspiration, what changes occur in the intra-alveolar pressure, and why are these changes important?
During inspiration, what changes occur in the intra-alveolar pressure, and why are these changes important?
Describe how the serratus anterior contributes to active breathing.
Describe how the serratus anterior contributes to active breathing.
What is the effect of contraction of the abdominal wall muscles on expiration?
What is the effect of contraction of the abdominal wall muscles on expiration?
Explain how weakness in the intercostal muscles can lead to hypoxia.
Explain how weakness in the intercostal muscles can lead to hypoxia.
Which muscles assist with the elevation of the upper ribcage during active breathing?
Which muscles assist with the elevation of the upper ribcage during active breathing?
During bowel obstruction, why does the inability of the diaphragm to flatten impact inspiration?
During bowel obstruction, why does the inability of the diaphragm to flatten impact inspiration?
Flashcards
Breathing (Ventilation)
Breathing (Ventilation)
The process by which oxygen and carbon dioxide are transported to and from the lungs.
Boyle's Law
Boyle's Law
At a constant temperature, the volume of a gas is inversely proportional to its pressure.
Key Ventilation Anatomy
Key Ventilation Anatomy
Lungs, diaphragm, rib cage, and external intercostal muscles.
Inspiration
Inspiration
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Inspiration Process
Inspiration Process
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Expiration
Expiration
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Expiration Process
Expiration Process
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Active Breathing
Active Breathing
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Accessory Muscles
Accessory Muscles
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Bowel Obstruction Breathing
Bowel Obstruction Breathing
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Neuromuscular Disease & Breathing
Neuromuscular Disease & Breathing
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Study Notes
- Breathing is the process of transporting oxygen to the lungs and carbon dioxide away from them, also known as ventilation.
Physics and Anatomy of Breathing
- Understanding the physics and anatomy is important to understanding the mechanics of breathing.
Boyle's Law
- Boyle’s Law states that at constant temperature, the volume of a gas is inversely proportional to pressure.
- When the volume of a gas container decreases, the pressure increases.
Relevant Anatomy
- Key anatomical structures involved in ventilation:
- Lungs
- Diaphragm
- Rib cage
- External intercostal muscles
Inspiration
- Inspiration is the process of transporting air into the lungs.
- During inspiration:
- The diaphragm contracts, allowing the lung bases to expand.
- The external intercostal muscles contract to move the rib cage and sternum upwards and outwards.
- These actions increase the volume of the thoracic cavity.
- Increased intra-thoracic volume reduces intra-alveolar pressure, allowing air to move into the lungs along a negative pressure gradient.
Passive Expiration
- Expiration is the process of transporting air out of the lungs.
- During expiration:
- The diaphragm relaxes and flattens, reducing the volume of the lung bases.
- Elastic recoil causes the chest wall to move downwards and inwards.
- These actions decrease the volume of the thoracic cavity.
- This decreased intra-thoracic volume increases intra-alveolar pressure, forcing air to move out.
Active Breathing
- Active breathing uses accessory muscles to assist with ventilation, allowing the thoracic cavity to expand and contract more rapidly.
- Active breathing commonly occurs during exertion or in disease states.
- Accessory muscles recruited during active respiration:
- Sternocleidomastoid: assists with the elevation of the sternum.
- Pectoralis major and minor: assist with the expansion of the ribs laterally.
- Serratus anterior: assists with the elevation of the ribcage.
- Latissimus dorsi: assists with the elevation of the lower ribcage.
- Scalenes: assists with the elevation of the upper ribcage.
- Muscles of the abdominal wall
Clinical Relevance: Bowel Obstruction
- Large bowel obstruction prevents the diaphragm from flattening effectively, reducing intrathoracic volume during inspiration.
- Reduced intrathoracic volume reduces the volume of gas that can be inspired.
- Decompression of the bowel via a nasogastric tube can improve the mechanics of breathing.
Clinical Relevance: Neuromuscular Disease
- Degenerative neuromuscular diseases like motor neurone disease can result in inadequate ventilation, due to weakness of the respiratory muscles.
- Weakness of these muscles:
- Reduces the intrathoracic volume generated during inspiration, reducing the pressure gradient for air to be drawn in, leading to inadequate oxygenation (hypoxia).
- Reduces the ability to decrease the intrathoracic volume during expiration, reducing the pressure gradient for air to be expelled, causing a build-up of CO2 (hypercapnia).
- Patients with advanced neuromuscular disease often require ventilatory support.
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