The endoderm develops into the lining of the digestive tract (except for parts of the mouth and pharynx and the terminal part of the rectum), as well as glands associated with the digestive system (e.g., pancreas, liver, gastric glands, intestinal glands). It also forms the lining of the respiratory tract, urinary bladder, urethra, and certain glands like the thyroid, parathyroid, and thymus.