5 When a person is in respiratory distress, the origin and insertion of the serr

Question

5 When a person is in respiratory distress, the origin and insertion of the serratus anterior muscle may actualily switch, and the part of the muscle attached to the medial border of the scapula acts as the origin. How will this change the muscle's action? Neuromuscular diseases may lead to a condition called drop foot, in which a patient is unable to dorsiflex his or her foot. Which muscle(s) do you think would be involved in this condition? Which muscles may have to compensate for lack of dorsiflexion during walking? Explain. 6 10

Explanation / Answer

5. The normal origin of serratus anterior is 1st to 8th ribs and insertion is on the medial border of scapula. The origin point of muscle is always fixed i.e. ribs are fixed and insertion is moving i.e. is medial border of scapula. In respiratory distress, the volume of thoracic cage needs to be increased. During this time the medial border of scapula becomes fixed and contraction of serratus anterior muscle moves and pulls the ribs.

6. Foot drop occurs due to paralysis of dorsiflexors of foot i.e. tibialis anterior, extensor hallucis longus and extensor digitorum longus. To compenste for foot drop knee flexion is increased during walking and knee flexors have to work more.This gait is called high steppage gait.

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