Endocrine system observed in all animals with a nervous system and all vertebrates have an hypothalamus-pituitary axis. All vertebrates have a thyroid, which in amphibians is also crucial for transformation of larvae into adult form. All vertebrates have adrenal gland tissue, with mammals unique in having it organized into layers. All vertebrates have some form of a renin–angiotensin axis, and all tetrapods have aldosterone as a primary mineralocorticoid. Endocrine system The endocrine system is a chemical messenger system consisting of hormones, the group of glands of an organism that secrete those hormones directly into the circulatory system to regulate the function of
Gastric glands neck cells" that produce mucus. This is thought to be different from the mucus produced by the gastric mucosa. Fundic glands found in the fundus and also in the body have another two cell types–gastric chief cells and parietal cells (oxyntic)). The chief cells are found in the basal regions of the gland and release a zymogen – pepsinogen, a precursor to pepsin. The parietal cells ("parietal" means "relating to a wall") are found in the walls of the tubes. The parietal cells secrete hydrochloric acid–the main component of gastric acid. This needs to be readily available for the stomach