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What is the primary action of the external intercostal muscles?
What is the primary action of the external intercostal muscles?
Inspiration.
Describe the direction of the internal intercostal muscles.
Describe the direction of the internal intercostal muscles.
Downward and backward.
Where do the external intercostal muscles originate?
Where do the external intercostal muscles originate?
From the lower border of the rib above.
What is the insertion point for the internal intercostal muscles?
What is the insertion point for the internal intercostal muscles?
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What distinguishes the action of the transversus thoracic muscle from the other intercostal muscles?
What distinguishes the action of the transversus thoracic muscle from the other intercostal muscles?
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Identify the origin of the sterno-costalis muscle.
Identify the origin of the sterno-costalis muscle.
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What action do the sub-costalis muscles perform?
What action do the sub-costalis muscles perform?
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Explain how the orientation of the innermost intercostal muscles differs from the external intercostals.
Explain how the orientation of the innermost intercostal muscles differs from the external intercostals.
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Where does the typical intercostal nerve originate?
Where does the typical intercostal nerve originate?
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What is the insertion point of the intercostal muscle?
What is the insertion point of the intercostal muscle?
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What is the primary action of the intercostal muscles?
What is the primary action of the intercostal muscles?
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Identify two branches of the typical intercostal nerve.
Identify two branches of the typical intercostal nerve.
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What ligament connects the two crura of the diaphragm?
What ligament connects the two crura of the diaphragm?
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From which vertebrae does the right crus of the diaphragm originate?
From which vertebrae does the right crus of the diaphragm originate?
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What anatomical area lies behind the kidney, filled with fat?
What anatomical area lies behind the kidney, filled with fat?
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What is the consequence of an intercostal nerve block?
What is the consequence of an intercostal nerve block?
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What nerve supplies motor function to the diaphragm?
What nerve supplies motor function to the diaphragm?
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Identify the main structures passing through the vena caval opening of the diaphragm.
Identify the main structures passing through the vena caval opening of the diaphragm.
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At what vertebral level does the esophageal opening in the diaphragm occur?
At what vertebral level does the esophageal opening in the diaphragm occur?
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What is the arterial supply to the diaphragm?
What is the arterial supply to the diaphragm?
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Describe the condition of a hiatus hernia related to the diaphragm.
Describe the condition of a hiatus hernia related to the diaphragm.
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Where does the typical intercostal nerve end after piercing the internal intercostal muscle?
Where does the typical intercostal nerve end after piercing the internal intercostal muscle?
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List the three main origins of the diaphragm.
List the three main origins of the diaphragm.
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What is the role of the rami communicantes associated with the typical intercostal nerve?
What is the role of the rami communicantes associated with the typical intercostal nerve?
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Identify the only intercostal nerves that share in the brachial plexus.
Identify the only intercostal nerves that share in the brachial plexus.
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What are the main structural components of the diaphragm's vertebral origin?
What are the main structural components of the diaphragm's vertebral origin?
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Name the ligament that connects the two crura of the diaphragm.
Name the ligament that connects the two crura of the diaphragm.
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Describe the anatomical area known as the vertebro-costal triangle.
Describe the anatomical area known as the vertebro-costal triangle.
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What sensory function does the lateral cutaneous branch of the intercostal nerve supply?
What sensory function does the lateral cutaneous branch of the intercostal nerve supply?
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What is the role of the phrenic nerve in diaphragm function?
What is the role of the phrenic nerve in diaphragm function?
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Which structures pass through the aortic opening of the diaphragm?
Which structures pass through the aortic opening of the diaphragm?
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What are the three major openings of the diaphragm, and which structures do they permit to pass?
What are the three major openings of the diaphragm, and which structures do they permit to pass?
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At which vertebral level do the structures passing through the esophageal opening align?
At which vertebral level do the structures passing through the esophageal opening align?
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How does a hiatus hernia relate to the diaphragm, and what causes it?
How does a hiatus hernia relate to the diaphragm, and what causes it?
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What is the primary function of the external intercostal muscles during respiration?
What is the primary function of the external intercostal muscles during respiration?
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How do the internal intercostal muscles contribute to the breathing process?
How do the internal intercostal muscles contribute to the breathing process?
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What direction do the fibers of the sterno-costalis muscle run?
What direction do the fibers of the sterno-costalis muscle run?
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What is the anatomical importance of the innermost intercostal muscles?
What is the anatomical importance of the innermost intercostal muscles?
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Where does the origin of the sub-costalis muscle occur?
Where does the origin of the sub-costalis muscle occur?
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Describe the orientation of the transversus thoracic muscles.
Describe the orientation of the transversus thoracic muscles.
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What role does the anterior intercostal membrane play in relation to the external intercostal muscles?
What role does the anterior intercostal membrane play in relation to the external intercostal muscles?
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In terms of rib attachment, where do the internal intercostal muscles insert?
In terms of rib attachment, where do the internal intercostal muscles insert?
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Study Notes
Intercostal Muscles
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External intercostals extend from the tubercle to the costochondral junction and continue as the anterior intercostal membrane.
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They run downward, forward, and medially.
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Origin: lower border of the rib above.
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Insertion: upper border of the rib below.
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Action: inspiration.
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Internal intercostals extend from the sternal margin to the rib angle.
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Continue as the posterior intercostal membrane.
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They run downward, backward.
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Origin: costal groove of the rib above.
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Insertion: upper border of the rib below.
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Action: expiration.
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Innermost intercostals extend through the middle part of the intercostal space.
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They run downward and backward.
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Origin: lower border of the rib above.
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Insertion: upper border of the rib below.
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Action: expiration.
Sternocostalis
- Extension: anterior part of intercostal space.
- Direction: upward and laterally.
- Origin: inner surface of xiphoid process and lower body of sternum.
- Insertion: inner surface of ribs 2-6.
- Action: expiration.
Subcostalis
- Extension: posterior part of intercostal space.
- Direction: downward and medially.
- Origin: inner surface of the rib near the angle.
- Insertion: inner surface of 2 or 3 ribs below.
- Action: expiration.
Intercostal Nerve
- Number: 3rd to 6th.
- Course: passes between pleura and posterior intercostal membrane, internal intercostal, and innermost intercostal.
- Passes in costal groove below intercostal vessels (VAN).
- Ends by piercing the internal intercostal muscle and anterior intercostal membrane, continuing as anterior cutaneous nerves.
- Branches: Rami communicants with the sympathetic chain (white and gray rami), muscular branches (upper and lower parts of intercostal muscles), collateral branches, sensory branches to parietal pleura, anterior cutaneous branches (front of thorax), and lateral cutaneous branches (side and back of thorax). Rami communicants receive gray rami.
- Atypical Intercostal Nerve (ICN): some share in brachial plexus (upper limb), some supply the axilla, and the lower 5 supply the anterior abdominal wall. Some intercostal nerves (2nd) may have a lateral cutaneous nerve called an intercostobrachial nerve. The lowest 5 intercostal nerves supply the anterior abdominal wall.
Diaphragm
- Origin: Sternal origin (back of xiphoid process), costal origin (inner surface of lower 6 ribs), and vertebral origin (upper 3 lumbar vertebrae for right crus, upper 2 for left crus).
- Median arcuate ligament connects the two crura; medial connects crura to T1 vertebra; and lateral connects T1 transverse process to the last rib.
- Vertebra-costal triangle: located between costal, vertebral and last rib. Larger on the left side and often filled with fat; it is a common place for internal hernias.
- Insertion: central tendon.
- Action: Main respiratory muscle.
- Nerve supply: Motor - phrenic nerve (C3, 4, 5). Sensory from lower 6 intercostal nerves.
- Arterial supply: Pericardiophrenic and musclophrenic from internal thoracic artery, superior phrenic from descending thoracic aorta, inferior phrenic from abdominal aorta.
Diaphragmatic Openings
- Major openings: Vena caval opening (costal level 6, vertebral level T8), esophageal opening (costal level 7, vertebral level T10), and aortic opening (costal level 8, vertebral level T12). Structures passing through these openings include inferior vena cava and right phrenic nerve, esophagus and 2 vagi, and aorta, thoracic duct, and azygous vein, respectively.
- Minor openings: Superior epigastric and musclo-phrenic vessels, inferior hemiazygous vein, lower 6 intercostal nerves, left phrenic nerve, quadratus lumborum. Also, the psoas major, sympathetic chain, and splanchnic nerves pass behind the medial arcuate ligament. Quadratus lumborum muscle passes behind the lateral arcuate ligament.
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