Accessory Digestive Organs
description
Transcript of Accessory Digestive Organs
Accessory Digestive Organs
Salivary glandsPancreasLiverGallbladder
Salivary Glands
• Function: produce saliva– Wets and lubricates the oral mucosa and the
ingested food (→ bolus)– Initiates digestion of carbohydrates and lipids
(amylase and lingual lipase)
Salivary Glands
• Minor salivary glands – 10% of total volume of saliva, 70% mucus
• Major salivary glands– Parotid– Submandibular (submaxillary)– Sublingual
Ductal System
• Lobes and lobules separated by connective tissue septa
• Secretory alveoli + ducts• Secretory alveoli: round, sac-like structures,
simple cuboidal epithelium resting on a basal lamina
• Ducts: intralobular, interlobular, lobar, main excretory ducts
Ductal System
• Intralobular ducts – located within the lobule– 2 segments:1.Intercalated duct – directly drains an
acinus/secretory lobule2.Striated (secretory) duct – union of intercalated
ducts
Ductal System
1. Intercalated duct• Simple squamous or simple cuboidal epithelium• Contain myoepithelial cells2. Striated duct • Simple cuboidal or simple columnar
epithelium• Exhibit basal striations• Contain myoepithelial cells
Ductal System
• Interlobular ducts – union of striated ducts, located in the connective tissue septa (between lobules)– Stratified cuboidal → stratified columnar
• Lobar ducts – drain an entire lobe– Stratified columnar epithelium
• Main excretory duct – opens into the oral cavity– Stratified squamous epithelium
Salivary Glands
Parotid Submandibular Sublingual
Location Below and anterior to the pinna of the ear, at the region of the angle of the mandible
Submandibular fossa of inner aspect of mandible, below the floor of the oral cavity
Floor of mouth, underneath the tongue (between the mandible and genioglossus muscle)
Type of Gland
Paired
Compound alveolar
Serous gland
Paired
Compound tubuloalveolar
Mixed gland
Paired
Compound tubuloalveolar
Mainly mucous gland
Salivary Glands
Parotid Gland Submandibular Sublingual
Description Connective tissue septa divide the gland into lobes
Contain adipose cells in lobes
Smaller than parotidCT septa thinner than parotid, divide the gland into lobes and lobules
Very few adipose cellsHave serous demilunes
Smallest salivary glandDuct system not as extensive as parotid and submandibular
Have some serous demilunes
Main duct Stensen’s duct Wharton’s duct Ducts of RivinusDuct of Bartholin
Serous vs Mucous Cells
Serous Cells Mucous Cells
•Pyramidal•Broad base resting on the basal lamina •Narrow apical surface•Short microvilli facing the small lumen in the center•“Grape attached to its stem”
(stem corresponds to the duct system)
•Cuboidal to columnar•Oval nuclei, pressed toward the bases•Most often organized as tubules, consisting of cylindrical arrays of secretory cells surrounding a lumen
Parotid Gland
Submandibular Gland
Sublingual Gland
Pancreas
• Pinkish, soft organ • 12-15 cm • Stretched transversely
across the posterior abdominal wall from the duodenum to the spleen
• Posterior to stomach• Mostly retroperitoneal
Pancreas
• Head• Tail• Body• Main pancreatic duct
(duct of Wirsung)• Accessory pancreatic
duct (duct of Santorini)
Pancreas
• Main functions: – Exocrine: produces digestive enzymes that act in
the small intestine (cells arranged in acini)– Endocrine: synthesizes and secretes hormones
(insulin and glucagon) into the bloodstream (islets of Langerhans)
Exocrine Pancreas
• Thin connective tissue septa divide the pancreas into lobules
• Acini surrounded by a basal lamina that is supported by a delicate sheath of reticular fibers
• Has rich capillary network (essential for the secretory process)
Pancreatic Acini
• 40-50 closely packed low columnar or pyramidal cells
• Narrow lumen, rest on basal lamina• Nucleus: round with 1 or more nucleoli• Cytoplasm:– Supranuclear – eosinophilic granules (zymogen
granules)– Infranuclear (basal) – abundant rough ER
Pancreas vs. Parotid
• Pancreas: – Absence of striated ducts– Presence of the islets of Langerhans – Initial portions of intercalated ducts penetrate the
lumens of the acini (centroacinar cells – constitute the intra-acinar portion of the intercalated duct
Pancreas
Pancreas