29 Questions
What is the shape of the diaphragm?
Dome-shaped
What happens to the ribs when the diaphragm contracts?
They move downward and rotate toward the horizontal plane
What is expiration?
A passive event due to elastic recoil of the lungs
Why do the internal intercostal muscles and the anterior abdominal muscles contract during expiration?
To accelerate expiration
How are the lungs attached to the chest wall?
They are indirectly attached to the chest wall through a thin layer of liquid
What type of coupling exists between the lungs and the chest wall?
Liquid coupling
What is the shape of the thoracic cage?
Conical
How many apertures (openings) does the thoracic cage have?
Two
What happens to the diaphragm during inspiration?
It contracts and moves downward
What is the name of the movement of the ribs during normal inspiration?
Pump handle movement
Which muscle is the most important inspiratory muscle?
Diaphragm
What is the name of the joint that bounds the inferior opening of the thoracic cage anteriorly?
Xiphisternal joint
Which muscle increases the antero-posterior diameter of the thoracic cavity during forced inspiration?
Pectoralis major
Which of the following muscles acts as a rib depressor during forced expiration?
Internal intercostal
Which nerve supplies the intercostal muscles?
Intercostal nerves
Where do the intercostal vessels and nerve lie in relation to the internal intercostal muscle?
Behind the internal intercostal muscle
Which of the following muscles helps in compression of abdominal viscera to aid in ascent of the diaphragm during forced expiration?
Rectus abdominis
What is the origin of the sternal part of the diaphragm?
Xiphoid process of sternum
Which muscle is responsible for elevating the 1st and 2nd ribs during inspiration?
Scalene muscles
What is the nerve supply of the diaphragm?
Phrenic nerve (C3, 4, 5)
What is the action of the diaphragm during contraction?
Increase vertical diameter of thoracic cavity
What is the insertion of the diaphragm?
Central tendon
What is the direction of the fibers of the external intercostal muscle?
Downward, forward, and medially
What is the maximal volume of air inhaled after a normal expiration?
3.6 L
What is the volume of gas that remains in the lung at the end of a passive expiration?
2-2.5 L
What is the volume of gas that remains in the lung after maximal expiration?
1-1.2 L
What is the maximal lung volume that can be achieved voluntarily?
5-6 L
What is the volume of air moved between TLC and RV?
4-5 L
What is the technique used to measure Functional Residual Capacity (FRC) and Residual Volume (RV)?
Helium Spirometry
Study Notes
Muscles of Respiration
- Pectoralis major: involved in forced inspiration, origins from sternum and costal cartilages, inserts into humerus, and increases antero-posterior diameter of thoracic cavity when arm is fixed
- Scalenus posterior: involved in forced inspiration, origins from cervical vertebrae, and inserts into 1st and 2nd ribs
- Rib depressors: involved in forced expiration, includes internal intercostal, innermost intercostal, subcostals, and transversus thoracis muscles
- Anterior abdominal wall muscles: involved in forced expiration, includes external oblique, internal oblique, transversus abdominis, and rectus abdominis muscles
Inspiration and Expiration
- Inspiration: active process involving contraction of diaphragm and rib elevators, increases vertical and antero-posterior diameter of thoracic cavity
- Expiration: passive process due to elastic recoil of lungs, but can be active during forced expiration involving contraction of internal intercostal and anterior abdominal muscles
Diaphragm
- Structure: dome-shaped, separates thoracic and abdominal cavities, and is the most important muscle of inspiration
- Action: contraction moves downward and rotates ribs, increasing vertical diameter of thoracic cavity
- Origin: costal (lower 6 ribs and costal cartilages), sternal (xiphoid process), and vertebral (upper 3 lumbar vertebrae)
- Insertion: central tendon
- Nerve supply: phrenic nerve (C3,4,5)
Thoracic Cage
- Structure: conical in shape, formed by sternum and costal cartilages anteriorly, ribs and intercostal spaces laterally, and thoracic vertebrae posteriorly
- Apertures: superior (thoracic outlet) and inferior (closed by diaphragm)
Respiratory Movements
- Diaphragm movement: inspiration (contraction and descent), expiration (relaxation and ascent)
- Rib movement: pump handle (elevation of ribs, increasing antero-posterior diameter of thoracic cavity) and bucket handle (elevation of ribs, increasing lateral diameter of thoracic cavity)
Lung Volumes and Pulmonary Function Tests
- Total Lung Capacity (TLC): 5-6 L, maximum lung volume achieved voluntarily
- Vital Capacity (VC): 4-5 L, volume of air moved between TLC and RV
- Functional Residual Capacity (FRC): 2-2.5 L or 40% of TLC, volume of gas remaining in lung at end of passive expiration
- Residual Volume (RV): 1-1.2 L, volume of gas remaining in lung after maximal expiration
- Inspiratory Capacity (IC): 3.6 L, maximum volume of air inhaled after normal expiration
- Total Minute Volume: 6 L/min at rest, increases to 100-200 L/min during exercise
Learn about the diaphragm's role in inspiration, its movement during contraction, and the process of expiration in the respiratory system.
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