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Questions and Answers
Which of the following nerves pierces the left dome of the diaphragm?
Which of the following is NOT a weak point of the diaphragm?
Which artery is a branch of the internal thoracic artery?
Which of the following is responsible for motor innervation of the diaphragm?
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Which of the following hernias occurs in the anterior part of the diaphragm?
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Which of the following is NOT an arterial supply of the diaphragm?
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Which of the following nerves passes posterior to the medial arcuate ligament?
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Which of the following is NOT a branch of the aorta?
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Which of the following is responsible for sensory innervation of the central part of the diaphragm?
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Which of the following is a weak point of the diaphragm?
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Study Notes
The Diaphragm
- The diaphragm is the principle muscle of respiration, forming the floor of the thoracic cavity and the roof of the abdominal cavity.
- It consists of a peripheral muscular part and a central tendinous part.
Relations of the Diaphragm
- Superior relations: pleura, base of the left and right lung, pericardium, and the diaphragmatic surface of the heart.
- Inferior relations: on the right, the lobes of the liver, right kidney, and right suprarenal gland; on the left, the left lobe of the liver, fundus of the stomach, left kidney, left suprarenal gland, and spleen.
Parts of the Diaphragm
- Sternal part: originates from the posterior surface of the xiphoid process and inserts into the central tendon.
- Costal part: originates from the lower 6 ribs and costal cartilages and inserts into the central tendon.
- Posterior vertebral or lumbar portion:
- Right crus: arises from the bodies of lumbar vertebrae 1-3 and the corresponding intervertebral discs.
- Left crus: arises from the sides of the first two lumbar vertebrae and the corresponding intervertebral discs.
- Medial arcuate ligament: connects the medial borders of the right and left crura.
- Lateral arcuate ligament: extends from the tip of the transverse process of L1 to the lower border of the 12th rib.
Actions of the Diaphragm
- Muscle of inspiration: pulls the central tendon down, increasing the vertical diameter of the thoracic cavity.
- Weight lifting muscle: fixes the diaphragm to rise the intra-abdominal pressure, supporting the vertebral column and preventing flexion during lifting.
- Muscle of abdominal straining: aids the contraction of anterior abdominal wall muscles, rising the intra-abdominal pressure to evacuate the pelvic content.
- Thoraco-abdominal pump: descent of the diaphragm decreases intra-thoracic pressure, increasing intra-abdominal pressure, compressing blood in the IVC and forcing it upwards.
Openings of the Diaphragm
- Aortic Opening (T12): aorta, thoracic duct, and azygos vein.
- Esophageal Opening (T10): esophagus, left and right vagus nerves, esophageal branch of left gastric vessels, and lymphatics from the lower 1/3 of the esophagus.
- Caval Opening (T8): IVC, terminal branch of the right phrenic nerve.
Additional Features
- Greater, lesser, and lowest splanchnic nerves pierce the crura.
- Sympathetic trunk passes posterior to the medial arcuate ligament.
- Superior epigastric vessels pass between the sternal and costal portions of the diaphragm.
- Left phrenic nerve pierces the left dome of the diaphragm.
Weak Points of the Diaphragm
- Lumbocostal trigone
- Sternalcostal trigone
- Esophageal opening
- Aortic opening
- Caval opening
Arterial Supply of the Diaphragm
- Superior phrenic artery (branch of the descending aorta)
- Inferior phrenic artery (branch of the abdominal aorta)
- Pericardiacophrenic artery (branch of the internal thoracic artery)
- Musculophrenic artery (branch of the internal thoracic artery)
Innervation of the Diaphragm
- Motor innervation: phrenic nerves (C 3, 4, 5)
- Sensory innervation:
- Peripheral part: intercostal nerves (T5-T11)
- Central part: phrenic nerve (C3, 4, 5)
Diaphragmatic Hernias
- Bochdalek's Hernia: posterior
- Morgagni Hernia: anterior
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Description
This quiz covers the anatomy of the diaphragm, including its location, functions, and relations to other organs in the thoracic and abdominal cavities.
