Digestion Tract: Accessory Organs

Pancreas function is restricted to two separate structural components:

• Exocrine, which are serous glands that synthesize and secrete enzymes needed for digestion into the duodenum. They closely resemble parotid glands, and their secretory units are acinar or tubuloacinar. These acini contain serous cells that exhibit serous secretory activity. The initial duct is an intercalated duct that begins within the acinus. The ducts cells within the acini are called centroacinar cells, which lack secretory granules and stain very lightly with eosin. Acinar cells are distinctly basophilic in subnuclear cytoplasm. Apical cytoplasm is filled with acidophilic granules called zymogen granules, which are more numerous in fasting humans.
• Endocrine, which allows synthesis and secretion of insulin and glucagon hormones into the blood. They regulate glucose, lipid, and protein metabolism.

Centroacinar cells are continuous with short intercalated ducts situated outside the acini. They secrete fluid rich in Na+ and bicarbonate, which neutralizes chyme and creates an optimal pH for the enzymes. The intercalated ducts merge to form interlobular collecting ducts, which are less prominent in the pancreas than in the parotid salivary gland.