Location of motoneurons innervating the musculus sphincter cloacae in the domestic fowl.

Horseradish peroxidase was injected into the musculus (m.) sphincter cloacae through the mucosa from the lumen side of the cloaca in the domestic fowl. Labeled neurons were found in the ventrolateral area of the ventral horn from the lumbosacral segments 7-9. The craniocaudal distribution of labeled neurons overlapped with that of hindlimb motoneurons. The m. sphincter cloacae is innervated by motoneurons sending axons to the sphincter cloacae either through the connexus caudalis branching from the caudal coxal nerve of the sacral plexus or through the lateral caudal nerve arising from the pudendal plexus.