Serratus posterior inferior muscle
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The serratus posterior inferior is a broad irregular-shaped back muscle that lies underneath the latissimus dorsi. It is positioned in the lower back at the junction of the thoracic and lumbar regions. The serratus posterior inferior extends between the lower thoracic and upper lumbar vertebrae and lower ribs. It is larger than the serratus posterior superior muscle. Both serratus posterior muscles are located relatively far from each other.