# Digestive Glands > Digestive glands for NEET Biology: salivary glands and lysozyme, liver bile 800-1000 ml, sphincter of Oddi, pancreatic zymogens and enterokinase activation. - Canonical URL: https://prepelephant.com/topics/neet-ug/biology/digestive-glands - Exam / course: NEET-UG · Subject: Biology - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Digestive Glands", PrepElephant, https://prepelephant.com/topics/neet-ug/biology/digestive-glands ## Direct answer The digestive tract is served by three pairs of salivary glands (parotid, submandibular and sublingual) secreting about 1000-1500 mL of saliva daily with salivary amylase and antibacterial lysozyme; by the liver, the largest gland, which secretes 800-1000 mL of bile per day — bile contains salts, pigments and cholesterol but no enzymes and is stored in the gall bladder; and by the pancreas, whose exocrine acini pour pancreatic juice with trypsinogen, chymotrypsinogen, procarboxypeptidases, amylase, lipase and nucleases into the duodenum. The bile and pancreatic ducts open jointly as the hepatopancreatic duct guarded by the sphincter of Oddi, and gastric glands within the stomach wall add mucus, pepsinogen, and hydrochloric acid with intrinsic factor from parietal cells. ## What you must remember - **Salivary glands:** three pairs — parotid, submandibular (submaxillary) and sublingual; saliva (1000-1500 mL/day) carries electrolytes, salivary amylase (ptyalin) and lysozyme, which lyses bacteria. - **Liver:** largest gland in the body; secretes 800-1000 mL of bile daily; bile has bile salts, bilirubin, biliverdin, cholesterol and phospholipids but no enzymes; the gall bladder stores and concentrates it. - **Bile's job:** emulsification of fats — breaking large globules into smaller droplets — and activation of lipase are its digestive claims, not digestion itself. - **Duct anatomy:** bile duct and pancreatic duct unite as the common hepatopancreatic duct opening into the duodenum, guarded by the sphincter of Oddi. - **Gastric glands:** mucus neck cells (mucus), chief or peptic cells (pepsinogen), and parietal or oxyntic cells (HCl and intrinsic factor). - **Pancreatic juice:** proteases secreted as inactive zymogens — trypsinogen, chymotrypsinogen, procarboxypeptidases — plus active pancreatic amylase, lipase and nucleases. - **Activation cascade:** enterokinase from the intestinal mucosa converts trypsinogen to active trypsin; trypsin then activates chymotrypsinogen and procarboxypeptidase, and also more trypsinogen. - **Pancreas is dual:** exocrine acini plus endocrine Islets of Langerhans — the same organ appears again in the chemical coordination chapter. ## The activation cascade at the duodenum The pancreas manufactures some of the most aggressive protein-digesters in the body, so it ships them disarmed. Trypsinogen, chymotrypsinogen and procarboxypeptidase leave the acini as harmless precursors and meet their key in the duodenum: enterokinase, an enzyme released by the intestinal mucosa, cleaves trypsinogen into trypsin. Trypsin is a convertor by temperament — it activates the remaining zymogens, including more of its own precursor, creating a self-amplifying cascade that switches digestion on precisely where food is, not on the road there. The design is protective: if trypsinogen activated inside the pancreas, the organ would digest itself, the logic underlying pancreatitis in clinical medicine. Around this cascade the gland plumbing matters as much as the chemistry. Bile made in the liver flows down the bile duct; when the sphincter of Oddi is closed, bile diverts into the gall bladder for storage and concentration. A fatty meal in the duodenum prompts the sphincter to relax, and bile and pancreatic juice enter together through the hepatopancreatic duct. Emulsified fat, now spread across a vastly greater surface, falls to pancreatic lipase — which is why "bile digests fats" remains the exam's most seductive false statement: bile prepares fat; enzymes digest it. Pair that with the volumes — 1000-1500 mL of saliva and 800-1000 mL of bile per day — and the numerical one-liners of this chapter are already banked. ## Where students lose marks Three losses recur. First, "which of the following enzymes is absent from bile" — all of them; bile contains no enzymes, only salts, pigments, cholesterol and phospholipids. Second, enterokinase's employer: students assign it to the pancreas; it comes from the intestinal mucosa, while trypsin (not enterokinase) activates chymotrypsinogen. Third, cell-type matching in the stomach — mucus neck, chief (peptic), parietal (oxyntic) — with HCl and intrinsic factor attributed jointly to parietal cells. A quiet but real viva angle: intrinsic factor's role in vitamin B12 absorption explains why gastric problems can surface years later as anaemia, a connection worth one hedged sentence rather than a wrong certainty. ## Frequently asked questions ### Which gastric cells secrete hydrochloric acid? Parietal or oxyntic cells of the gastric glands, which also secrete intrinsic factor needed for vitamin B12 absorption. ### What activates trypsinogen and where does the activator come from? Enterokinase, secreted by the intestinal mucosa, converts trypsinogen to trypsin, which then activates other pancreatic zymogens. ### Why is bile called a digestive juice when it contains no enzymes? Because its bile salts emulsify fats into small droplets and help activate lipase, enabling enzymatic fat digestion in the small intestine. ### What is the hepatopancreatic duct and which sphincter guards it? The common channel formed by the bile duct and pancreatic duct opening into the duodenum, guarded by the sphincter of Oddi. ### How much saliva and bile are secreted per day per NCERT? About 1000-1500 mL of saliva by the three pairs of salivary glands and 800-1000 mL of bile by the liver.