Cardiovascular ANATOMY - Diaphragm and Intercostal Muscles
طب بشري | Medicine
جامعة الفيصل
- 2025-03-28
Diaphragm
The diaphragm is a dome-shaped skeletal muscle that separates the thoracic cavity from the abdominal cavity. It is the primary muscle of respiration and contributes indirectly to cardiovascular function by influencing intrathoracic pressure.
Structure
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Origin: The diaphragm originates from multiple points:
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Xiphoid process of the sternum.
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Lower six costal cartilages.
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Lumbar vertebrae (via the crura).
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Insertion: It inserts into the central tendon, a strong aponeurotic structure.
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Parts:
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Peripheral muscular part.
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Central tendinous part.
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Function
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Respiration: During inspiration, the diaphragm contracts and flattens, increasing the vertical diameter of the thoracic cavity. This creates negative pressure, allowing air to enter the lungs.
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Cardiovascular Impact: The diaphragm's movement affects venous return to the heart by altering intrathoracic pressure, aiding in blood circulation.
Innervation
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Phrenic Nerve: Arises from C3, C4, and C5 spinal nerves ("C3, C4, and C5 keep the diaphragm alive").
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Sensory Innervation: The phrenic nerve provides sensory input to the central part, while the peripheral parts receive sensory innervation from lower intercostal nerves.
Clinical Relevance
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Diaphragmatic Paralysis: Can result from phrenic nerve damage, leading to respiratory distress.
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Hiatal Hernia: Occurs when abdominal organs protrude through the diaphragm.
Intercostal Muscles
The intercostal muscles are located between the ribs and are essential for respiration. They consist of three layers: external, internal, and innermost intercostal muscles.
Structure
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External Intercostal Muscles:
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Fibers run downward and forward.
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Extend from the inferior border of one rib to the superior border of the rib below.
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Function: Elevate ribs during inspiration, increasing thoracic volume.
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Internal Intercostal Muscles:
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Fibers run downward and backward.
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Extend from the subcostal groove of one rib to the upper border of the rib below.
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Function: Depress ribs during forced expiration.
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Innermost Intercostal Muscles:
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Incomplete layer.
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Function: Assist external and internal intercostal muscles.
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Function
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Respiration:
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Contraction of intercostal muscles changes the dimensions of the thoracic cavity.
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External intercostals are active during inspiration, while internal intercostals are active during expiration.
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Innervation
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Intercostal Nerves:
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Derived from the anterior rami of thoracic spinal nerves (T1-T11).
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Provide motor and sensory innervation to the intercostal muscles and overlying skin.
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Clinical Relevance
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Intercostal Neuralgia: Pain along the intercostal nerves, often due to trauma or inflammation.
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Chest Wall Injuries: Can impair the function of intercostal muscles, affecting respiration.
Integration in Cardiovascular Anatomy
While primarily involved in respiration, the diaphragm and intercostal muscles indirectly support cardiovascular function:
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Venous Return: Diaphragmatic movement enhances venous return to the heart.
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Thoracic Pressure Regulation: Changes in thoracic pressure during respiration influence cardiac output and blood flow.
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