Bird, isthmus (LM, Low)

Structure List Muscularis mucosa Circular layer of muscle Glands A fold of mucosa Tract Diagram View

ISTHMUS OF THE BIRD. The oviduct has five parts. The shortest part is the isthmus. The glands of the isthmus produce the shell membranes. These are keratin-forming glands and are high in sulfur-containing proteins. The egg is in the isthmus for about 1.5 hours where it receives the shell membranes. The isthmus is lined by pseudostratified, ciliated epithelium . The mucosa is thrown into folds. The muscularis portion is tightly applied to the epithelial layers. Tubular glands produce the membranes.