Exocrine Pancreas and Salivary Gland Physiology Flashcards
Salivary Glands
3 pairs of glands: parotid, submandibular and sublingual
Produce a serous (proteinaceous) or mucus product, or both
Constituents of Saliva and their Functions
Water: Facilitates taste and dissolution of nutrients; aids in swallowing and speech
Bicarb: Neutralizes refluxed gastric acid
Mucins: Lubrication
Amylase: Strach digestion
Lysozyme, lactoferrin, IgA: innate and acquired immune protection
Epidermal and nerve growth factors: Assumed to contribute to mucosal growth and protection
What is the secretory unit of the Salivary Gland
Acinus
Acinar cells make the saliva and striated duct cells modify its ionic content
Salivary Secretion Regulation by ANS
Parasympathetic – increased acinar cell secretion and vasodilation of blood vessels surrounding the acini (results in protein rich & fluid/ion rich solution)
Sympathetic – increased acinar cell secretion (results in high protein/low fluid solution); less water (think gross, crusty running mucus)
Myoepithelial cells
help squeeze acinar cells and force them to secrete into the acinus
Pancreatic gland DONT have them
What downregulates salivary secretions
Sleep
Fatigue
Fear
What upregulates salivary secretion
Smell, taste, sound, and sight of food
Pressure in mouth
Which system primarily facilitates salivary secretion?
Parasympathetic through octic gangion (parotid gland) and submandibular ganglion (submandibular gland)
Saliva formation
Formation by passive filtration
Content and secretion rate is dependent on blood flow
Mechanism of Salivary Secretion: Fast vs. Slow Flow Rate
Low flow rate: duct cells absorb Na+ and Cl- and secrete K+ and HCO3-
High flow rt: Don’t have time to modify it so much more NaCl present in the secretions and less K Bicarb
Are acinar secretions hypertonic, hypotonic, or isotonic?
Close to isotonic
What allow movement of ions and water from the blood into saliva?
Tight junctions
Movement of water in salivary ducts
is restricted by TJs, leaving the saliva hypotonic
What establishes a concentration gradient in salivary duct cells?
Na+/K+ ATPase
Pancreas and Pancreatic Secretions
Acinar cells produce a variety of enzymes (proteases, lipases and amylases)
Ductal cells produce a bicarbonate solution to help liquefy and neutralize acidic chyme in the duodenum
Endocrine organ
Secretory Products of the Pancreas
Proteases: Trypsinogen, Chymotrypsinogen, Proleastase, Procarboxypeptidase A, Procarboxypeptidase B*
Amylases: Amylase
Lipases: Lipase, Nonspecific esterase, Prophospholipase A2*
Nucleases: Deoxyribonuclease, Ribonuclease
Others: Procolipase*, Trypsin inhibitors, Monitor peptide,
*= stored and secreted in inactive forms
Regulation of Pancreatic Secretion
Acetylcholine (ACh) – released from the vagus and ENS nerves; stimulates the release of digestive enzymes from acinar cells (mostly cephalic stage)
Secretin – released from endocrine cells in the proximal small intestines in response to acid; stimulates the release of a bicarbonate rich solution from pancreatic duct cells
Cholecystokinin (CCK) – released from endocrine cells in the proximal small intestines in response to fats & proteins; stimulates the release of digestive enzymes from acinar cells but has other effects in the duodenum
Structure of the Exocrine Pancreas
Acinar cells make the enzymes and duct cells secrete a water/bicarbonate rich solution
Effects of Cholecystokinin Cluster Unit in the Duodenum
Gallbladder contraction, pancreatic acinar secretion, reduced emptying of stomach, relaxation of sphincter of Oddi
Protein, carbohydrate, lipid absorption and digestion
Matching of nutrient delivery to digestive and absorptive capacity
cAMP and Ca2+ have what eddect on pancreatic acinar cell secretion?
Phosphorylation of structural and regulatory proteins causing fusion of granules with with apical membrane and discharge of contents
Trypsin
The bulk of the enzymes released by the pancreas are proteases
Trypsin is secreted from the pancreas in an inactive, pro-enzyme form called trypsinogen. Also released is a trypsin inhibitor.
Trypsin becomes activated in the duodenal lumen when trypsinogen is cleaved by enzymes (enterokinases) located on the surface of enterocytes
Activated trypsin then autoactivates more trypsinogen along with most of the other pancreatic enzymes
Effect of Secretin
Secretin acts by increasing cAMP levels in the duct cells. The release of secretin is enhanced by CCK
Pancreatic secretion regulation
ANS and hormones
Salivary is just ANS
Pancreatic acini compared to salivary acini
Pancreatic acini are not as vascular and respond to ACh and CCK. Ductal cells actively secrete a water and a bicarbonate rich solution in response to secretin.
The salivary acinus is very vascular and increased blood flow results in a dilute saliva that is modified by duct cells. Salivary ducts, on the other hand, are fairly impermeable to water.
Saliva vs pancreatic juice
Saliva is rich in KHCO3 whereas pancreatic juice is rich in NaHCO3.
Salivary Gland Diseases
Mumps Cytomegaloviral Sialadenitis Bacterial Sialadenitis Sarcoidosis Sjögren’s Syndrome Salivary Lymphoepithelial Lesion Xerostomia or dry mouth Halitosis
Benign Neoplasms
Mixed Tumor (pleomorphic adenoma)
Monomorphic Adenomas
Ductal papilloma
Endocrine Pancreatic Cancer
Gastrinoma (Zollinger-Ellison Syndrome)
Glucagonoma – usually large, often mets, 70% malignant
Insulinoma – the most common pancreatic neuroendocrine tumors
Nonfunctional islet cell tumors (NICT) – Usually malignant and hard to detect
Somatostatinoma – occur anywhere in the pancreas or doudenum
VIP-Releasing Tumor – usually in the body and tail of the pancreas
Pleomorphic Adenoma
The diverse microscopic pattern of this lesion is one of its most characteristic features.
Islands of cuboidal cells arranged in ductlike structures is a common finding.
Warthin’s Tumor
Warthin’s tumor (benign papillary cystadenoma lymphomatosum)
the second most common benign tumor of the parotid gland
It accounts for 2-10% of all parotid gland tumors
Bilateral in 10% of the cases
may contain mucoid brown fluid in FNA
Oncotic epithelial Component (fronds) and Lymphoid Component
BOTH must be present to diagnose
Monomorphic Adenoma
Similar to Pleomorphic Adenoma except no mesenchymal stromal component
Basal Cell Adenoma
A monomorphic adenoma is composed of uniform basaloid epithelial cells with a monomorphous pattern.
Histologically, these tumors are distinguished from pleomorphic adenomas by their absence of stroma and the presence of a uniform epithelial pattern.
Malignant Neoplasms
Mucoepidermoid Carcinoma (mucin+) Polymorphous Low-grade Adenocarcinoma Adenoid Cyctic Carcinoma Clear Cell Carcinoma Acinic Cell Carcinoma (no glycogen, fat & mucin, 3% maligant and bilateral)
Features Suggestive of Malignancy
Induration (hardness) Fixed to Overlying Skin or mucosa Ulceration of skin or mucosa Rapid Growth; Growth Spurt Short Duration Pain, often severe Facial N. Palsy
Mucoepidermoid Carcinoma
MECs contain two major elements: mucin-producing cells and epithelial cells (Epidermoid and Mucinous components)
Adenoid Cystic Carcinoma
Adenoid cystic carcinoma with Swiss cheese pattern.
It is the second-most common malignant tumor of the salivary glands.
ACC is the most common malignant tumor found in the submandibular, sublingual, and minor salivary glands.
Exocrine Pancreatic Cancer
Acinar Cell Carcinoma – Rare, leads to overproduction of lipase
Adenocarcinoma – 90% of all pancreatic cancer starts in duct
Adenosquamous carcinoma - forms glands that flatten as it grows
Intraductal Papillary-Mucinous Neoplasm – fingerlike projections into the duct, prelude to malignancy
Mucinous Cystadenocarcinoma – rare malignant spongy cystic tumor
Pancreatoblastoma – Rare, occurs in kids
