Saliva is secreted from:
Parotid glands acini are serous they form about 25%.
Sublingual glands acini are mucous they form about 5%.
Submandibular glands acini are mixed they form about 75%

The buccal glands secrete only mucous

The first stage of secretion of the saliva: the acini secrete a primary secretion that contains ptylain and mucins in a solution of ions which shows no great difference from the extra cellular fluid.

In the second stage: Na is actively reabsorbed.
K,bicarbonate (hco3) are actively secreted.
Cl is passively reabsorbed.

Proline-rich protiens protect teeth enamel and bind toxic tannins.

Stimulation of salivary secretion is entirely under neural control.

Salivary secretion under unconditioned reflexes is because of impulses that excite superior and inferior salivary nuclei.

The stomach parasympathetic supply comes from two vagi and its sympathetic supply from the celiac plexus

Stomach secrete 2.5 L/day of acidic juice.

Active pepsin further activates pepsinogen by positive feedback mechanism

Chronic gastritis caused damage to the acid-producing cells of the stomach, so the patient develops achlorhydria and pernicious anemia because of the lack of the vitamen b12, because lack of the intrinsic factor

Insolube mucous forms a layer 1.5 mm in thickness.

Intrinsic factor & HCL are secreted from parietal cell (oxyntic cells)

pepsinogen is secreted from cheif (peptic) cells

soluble mucous is secreted from mucous neck cells

Insoluble mucous is secreted from Epithelium of the gastric body, esophageal &pyloric junctions, and the fundus.

1500 ml of pancreatic juice is secreted per day.

Pancreatic secretion is regulated by both nervous and hormonal mechanisms, but the hormonal regulation is the main mechanism.

In the nervous regulation of pancreatic secretion: the acetylcholine exerts its effects by activating phospholipase C. , the same as CCK hormone.

The effect of secretin on duct cells is due to increased intracellular c-AMP