Junqueira’s Basic Histology Text and Atlas, 16th Edition
Mescher, A.L., 2021
Jay Ryan Erbito
Bachelor of Science in Biology
University of the Philippines Mindanao
Chapter 16 Organs Associated with the Digestive Tract • Interlobular excretory ducts
• Organs associated with the digestive tract include the major salivary glands, o Larger duct arising from the fusion of ducts from each lobule.
pancreas, liver, and gallbladder. • The main duct of each gland is lined with nonkeratinized stratified squamous
• Facilitate transport and digestion of food. epithelium before emptying into the oral cavity.
Salivary Glands • Parasympathetic stimulation, through smell or taste of food, results to the
• Digestive, lubricating, and protective functions. production of watery secretions while sympathetic stimulation inhibit such
• Normal pH of 6.5 - 6.9. secretion.
• Important buffering function and in some species is also important in evaporative • Specific features of the major salivary glands:
cooling. o Parotid glands
• Major salivary glands: parotid, submandibular, sublingual. ▪ Located in each cheek near the ear.
• CT capsule surround each major salivary gland. ▪ Branched acinar glands.
• Parenchyma consists of the secretory units on a branching duct system arranged in ▪ Secretion is abundant in α-amylase.
lobules, separated by septa. o Submandibular glands
• Parotid is exclusively serous while the sublingual and submandibular are ▪ Produce 2/3 of all saliva.
seromucous. ▪ Branched tubuloacinar glands, primarily serous.
• Saliva is modified by the cells of the duct system, much Na+ and Cl- are reabsorbed ▪ Grouped serous cells occur distally on short mucous tubules as
and certain growth factors and digestive enzymes are added. serous demilunes.
▪ Serous cells secrete lysozyme for bacterial cell wall hydrolysis.
• Epithelial cell types in salivary secretory units:
o Sublingual glands
o Serous cells
▪ Smallest of the major salivary glands.
▪ Protein-secreting cells (enzymes).
▪ Branched tubuloacinar glands, primarily mucous.
▪ Pyramidal cells with round nuclei.
▪ Form a spherical unit called an acinus with very small central ▪ Main product is mucus.
Pancreas
lumen.
o Mucous cells • A mixed exocrine-endocrine gland.
▪ More columnar in shape with compressed basal nuclei. • Produces both digestive enzymes and hormones.
▪ Apical granules with hydrophilic mucins (poor staining). • Elongated retroperitoneal organ, with large head and more narrow body and tail.
▪ Organized as cylindrical tubules. • Has a thin CT capsule from which septa extend to separate the parenchyma into
o Myoepithelial cells lobules.
▪ Found inside the basal lamina surround acini, tubules, and • Endocrine function is carried out by clusters of smaller cells called the pancreatic
proximal ends of the duct system. islets or islets of Langerhans.
▪ Important for moving secretory products into and through the • The digestive enzymes are produced by the exocrine portion of the pancreas made
ducts. up of cells of serous acini. Resembles the parotid gland histologically but lacks
• Intralobular duct system striated ducts and parotid lacks islet of Langerhans.
o Secretory acini and tubules empty into short intercalated ducts with • Pancreatic acini lack myoepithelial cells. At the center of the acini, pale staining
cuboidal epithelial cells. centroacinar cells are present that secrete fluid rich in bicarbonate ions.
o Intercalated ducts join to form striated ducts with columnar epithelial cells. • The intercalated ducts of each acinus are lined with simple squamous or low
o Striations of the striated ducts is due to the infoldings of the basolateral cuboidal epithelium. These ducts merge with intralobular ducts and larger
membrane lined with mitochondria. Striated ducts reabsorb Na+ ions interlobular ducts before joining the main pancreatic duct.
using ion transporters located in the striated basolateral membranes. • Exocrine pancreas produces 1.5 L of alkaline pancreatic juice per day and neutralize
o Plasma cells in the surrounding CT release IgA that forms complex with the acidic chyme in the duodenum.
secretory components. IgA complexes provide defense against pathogen • Digestive enzyme includes protease, α-amylase, lipases, and nucleases.
in the oral cavity.
1 | Organs Associated with the Digestive Tract
Mescher, A.L., 2021
Jay Ryan Erbito
Bachelor of Science in Biology
University of the Philippines Mindanao
Chapter 16 Organs Associated with the Digestive Tract • Interlobular excretory ducts
• Organs associated with the digestive tract include the major salivary glands, o Larger duct arising from the fusion of ducts from each lobule.
pancreas, liver, and gallbladder. • The main duct of each gland is lined with nonkeratinized stratified squamous
• Facilitate transport and digestion of food. epithelium before emptying into the oral cavity.
Salivary Glands • Parasympathetic stimulation, through smell or taste of food, results to the
• Digestive, lubricating, and protective functions. production of watery secretions while sympathetic stimulation inhibit such
• Normal pH of 6.5 - 6.9. secretion.
• Important buffering function and in some species is also important in evaporative • Specific features of the major salivary glands:
cooling. o Parotid glands
• Major salivary glands: parotid, submandibular, sublingual. ▪ Located in each cheek near the ear.
• CT capsule surround each major salivary gland. ▪ Branched acinar glands.
• Parenchyma consists of the secretory units on a branching duct system arranged in ▪ Secretion is abundant in α-amylase.
lobules, separated by septa. o Submandibular glands
• Parotid is exclusively serous while the sublingual and submandibular are ▪ Produce 2/3 of all saliva.
seromucous. ▪ Branched tubuloacinar glands, primarily serous.
• Saliva is modified by the cells of the duct system, much Na+ and Cl- are reabsorbed ▪ Grouped serous cells occur distally on short mucous tubules as
and certain growth factors and digestive enzymes are added. serous demilunes.
▪ Serous cells secrete lysozyme for bacterial cell wall hydrolysis.
• Epithelial cell types in salivary secretory units:
o Sublingual glands
o Serous cells
▪ Smallest of the major salivary glands.
▪ Protein-secreting cells (enzymes).
▪ Branched tubuloacinar glands, primarily mucous.
▪ Pyramidal cells with round nuclei.
▪ Form a spherical unit called an acinus with very small central ▪ Main product is mucus.
Pancreas
lumen.
o Mucous cells • A mixed exocrine-endocrine gland.
▪ More columnar in shape with compressed basal nuclei. • Produces both digestive enzymes and hormones.
▪ Apical granules with hydrophilic mucins (poor staining). • Elongated retroperitoneal organ, with large head and more narrow body and tail.
▪ Organized as cylindrical tubules. • Has a thin CT capsule from which septa extend to separate the parenchyma into
o Myoepithelial cells lobules.
▪ Found inside the basal lamina surround acini, tubules, and • Endocrine function is carried out by clusters of smaller cells called the pancreatic
proximal ends of the duct system. islets or islets of Langerhans.
▪ Important for moving secretory products into and through the • The digestive enzymes are produced by the exocrine portion of the pancreas made
ducts. up of cells of serous acini. Resembles the parotid gland histologically but lacks
• Intralobular duct system striated ducts and parotid lacks islet of Langerhans.
o Secretory acini and tubules empty into short intercalated ducts with • Pancreatic acini lack myoepithelial cells. At the center of the acini, pale staining
cuboidal epithelial cells. centroacinar cells are present that secrete fluid rich in bicarbonate ions.
o Intercalated ducts join to form striated ducts with columnar epithelial cells. • The intercalated ducts of each acinus are lined with simple squamous or low
o Striations of the striated ducts is due to the infoldings of the basolateral cuboidal epithelium. These ducts merge with intralobular ducts and larger
membrane lined with mitochondria. Striated ducts reabsorb Na+ ions interlobular ducts before joining the main pancreatic duct.
using ion transporters located in the striated basolateral membranes. • Exocrine pancreas produces 1.5 L of alkaline pancreatic juice per day and neutralize
o Plasma cells in the surrounding CT release IgA that forms complex with the acidic chyme in the duodenum.
secretory components. IgA complexes provide defense against pathogen • Digestive enzyme includes protease, α-amylase, lipases, and nucleases.
in the oral cavity.
1 | Organs Associated with the Digestive Tract
