Histology of GI Glands Flashcards
Digestive glands have lubricating, protective, digestive, and absorptive functions mediated by their secretory products. What are the 3 main digestive glands?
Major salivary glands: associated with oral cavity through independent excretory ducts
Exocrine pancreas: secretes alkaline aqueous and enzymatic product into the duodenum
Liver: endocrine and exocrine gland with extensive access to blood circulation
______ glands may exist as simple invaginations of the epithelium or may have no contact with epithelial surface. They secrete mucus, hormones, enzymes, and wastes.
Exocrine
_________ = part of exocrine glands that acts as passageway for glandular secretions to be released
________ = cellular part of exocrine glands that synthesize and release secretory product
Excretory duct
Secretory units
Secretory cells of exocrine glands are organized in an _______
Acinus
______ acini = cloudier looking cytoplasm, produce thick, glycoprotein rich product
______ acini = clear-staining cytoplasm, produce a water-based product
_______ = contain a core of mucous cells surrounded by serous demilune
Mucous
Serous
Mucoserous
The secretory component of exocrine glands may be _____ or ________, both of which may be coiled or branched
The duct system may be a _____ gland or _____gland
Tubular; alveolar
Simple (unbranched); compound (branched)
3 possible mechanisms of secretion from exocrine glands. What is the most common for the GI system?
Merocrine = exocytosis of apical end of secretory cells (sweat glands)
Holocrine = disintigration of the secretory cell (sebaceous glands)
Apocrine = release of membrane-enclosed vesicles (sweat glands)
most GI glands are merocrine
Describe general histology of a salivary gland
Secretory (epithelial) cells line the ducts and produce saliva (release controlled by ANS)
CT capsule with septa divides gland into lobes (interlobar septa), and smaller lobules (interlobular), providing rout for neurovasculature
What are the 3 types of salivary glands? Which one is largest?
Parotid (largest)
Sublingual
Submandibular
Which salivary gland is often confused histologically with the pancreas? How can the 2 be differentiated?
Parotid
Differentiated based on presence of adipocytes in parotid gland tissue, as well as presence of islets of langerhans in pancreas
The parotid gland is formed by acini containing exclusively ______ cells with a basal nucleus and an apical cytoplasm with secretory granules.
Granules are rich in proteins, including _____-rich proteins, enzymes, and proteins with ______ activity like cystatins and hystatins.
The parotid gland has the longest _____ ducts. ______ cells can be visualized at the periphery of each acinus
Serous
Proline; antimicrobial
Intercalated; myoepithelial
Which of the salivary glands is considered mixed, but it is predominantly mucous?
Sublingual gland
Describe histological characteristics of the sublingual gland
Lacks defined capsule but is divided by CT into small lobes
Intercalated and striated ducts are poorly developed
Which of the salivary glands has both serous and mucous cells but serous cells predominate?
Submandibular gland
Describe histological features of submandibular gland
Mucous cell-containing acini are capped by serous demilunes (surrounding myoepithelial cells control serous secretions)
Intercalated ducts are shorter and striated ducts are longer than those in parotid gland
Hepatic _____ = polygonal structures that comprise functional unit of the liver
_______ = liver cells that function in metabolism, storage, and bile production (similar to acinar cells in that they secrete an exocrine product but they are organized in columns)
Lobules
Hepatocytes
Components of hepatic lobules
Central venule in core of hepatic lobule - collects blood in hepatic sinusoids
Hepatocytes
Sinusoids
Portal triad = branches of hepatic a. and portal v. and bile duct
While looking at a liver slide you note the following things:
_____ ____ delineated on all sides by CT
_____ ______ = brown staining stick-like structures located in between hepatocytes
_____ ____ including portal vein branches, hepatic a. branches, and bile ductules
Hepatic lobule
Bile canaliculi
Portal triad
There are 3 ways to reference the functional organization of the liver:
______ = based on structural units of the liver
_____ = based on bile drainage pathway from adjacent lobules toward the same bile duct
______ = based on [O2] gradient along sinusoids of adjacent lobules
Hepatic lobule
Portal lobule
Liver acinus
Describe the hepatic lobule functional organization of the liver
Hexagonal in shape and centered on central venule
Portal triads are positioned at angles of hexagon
[this is classic organization]
Describe portal lobule functional organization of the liver
Portal triad is the central axis, draining bile from the surrounding hepatic parenchyma
Describe the liver acinus functional organization of the liver
Boundaries are determined by a terminal branch of the hepatic a.
Flow of arterial blood creates gradient of O2/nutrients
Establishes zones 1, 2, and 3; cells within each zone have different metabolic functions
Describe the 3 zones delineated in the liver acinus functional organization of the liver
Zone 1 = closest to portal triad; hepatocytes actively synthesize glycogen and plasma proteins, O2 concentration is high
Zone 2 = intermediate
Zone 3 = furthest from portal triad; poor O2 concentration, this zone important for detoxification. Hepatocytes here are susceptible to hypoxic damage
The hepatocyte is the exocrine and endocrine cell of the liver. They form anastomosing ____-cell thick plates which limit sinusoidal spaces
The _________ is what separates the hepatocyte plates from the blood sinusoidal space. Blood from the portal vein and hepatic a. flows into the sinusoids and is drained by the _____ _____. Excess fluid in this space is collected in the ________ (periphery of hepatic lobule), drained by lymphatic vessels.
One
Perisinusoidal space of Disse; central venule; Space of Mall
The apical domain of hepatocytes borders the ______ ______, a trench-like depression lined by microvilli that is sealed at the sides by occluding junctions to prevent leakage of ____, the exocrine product of the hepatocyte
Bile canaliculus; bile
The basolateral domain of the hepatocyte has abundant microvilli facing the space of _____. It is important for absorption of ________-borne substances and secretion of plasma proteins
Disse; blood
Specialized macrophages found along the endothelial lining of hepatic sinusoids (larger than the endothelial cells). these cells detect and phagocytose aging erythrocytes
Kupffer cells
The pancreas has both endocrine and exocrine gland functions but is primarily exocrine. The exocrine pancreas is what type of gland?
Branched tubuloacinar gland
[organized into head, neck, body, and tail]
Arterial supply to pancreas
Vessels derived from celiac trunk/artery, SMA, and splenic a.
Venous drainage of pancreas
Venous drainage flows into portal venous system and splenic v.
Efferent innervation of pancreas
Through vagus and splanchnic nn
Does the pancreas have a capsule? How are its lobules separated?
Pancreas is surrounded by CT but does not have a capsule proper
Lobules are separated by CT septa carrying blood and lymphatics, nerves, and excretory ducts
What is the functional unit of the exocrine pancreas?
Serous acinus
The functional unit of the pancreas is the serous acinus. The lumen of the acinus begins the secretory-excretory duct system, and is lined with what cell type unique to the pancreas?
Centroacinar cells - continuous with low cuboidal epithelium and secrete bicarb, sodium, and water to alkalinze secretions
What are the 3 identifying characteristics of a pancreatic acinar cell?
Well developed RER
Prominent golgi apparatus
Apical domain of zymogen granules
How does the content of the zymogen granules of pancreatic acinar cells change with a protein-rich diet vs. a carb-rich diet?
Protein rich diet —> increased synthesis of proteases
Carb-rich diet —> increased synthesis of amylases, decreased synthesis of proteases
Zymogen granules contain inactive proenzymes normally activated in the duodenum. Premature activation of these enzymes may result in what condition?
Acute Pancreatitis
Premature activation of pancreatic enzymes results in autodigestion of pancreatic gland following their release, particularly with _______ —> _________, and inactivation of _____ inhibitor
Trypsinogen; trypsin; trypsin
What are some triggers for acute pancreatitis attacks? What are the symptoms?
Usually follows trauma, heavy meals or excessive alcohol ingestion, or biliary tract disease
Symptoms: severe abdominal pain, nausea, and vomiting
Condition characterized by fibrosis and partial or total destruction of pancreatic tissue, of which alcohol is a major cause
Chronic pancreatitis
______ from the duodenum binds to receptors of pancreatic acinar cells and stimulates granule release
Cholecystokinin
What is the pathway of secretion from the pancreas, starting at the intercalated ducts?
Intercalated ducts —> interlobular ducts** —> main pancreatic duct directly into hepatopancreatic ampulla
**note that exocrine pancreas lacks striated ducts
Which of the following glands specific to the GI system is characterized by a straight tubular lumen, simple columnar secretory cells, and is found in the large intestine?
A. Simple tubular glands B. Simple coiled tubular glands C. Simple branched tubular glands D. Compound branched tubular glands E. Compound alveolar/acinar glands F. Compound tubulo-alveolar/acinar glands
A. Simple tubular glands
Which of the following glands specific to the GI system is characterized by multiple tubular portions connecting to single unbranched duct, simple columnar secretory cells without goblet cells, and are found in the stomach?
A. Simple tubular glands B. Simple coiled tubular glands C. Simple branched tubular glands D. Compound branched tubular glands E. Compound alveolar/acinar glands F. Compound tubulo-alveolar/acinar glands
C. Simple branched tubular glands
Which of the following glands specific to the GI system is characterized by branched duct system, acinar secretory portion, and are found in the pancreas?
A. Simple tubular glands B. Simple coiled tubular glands C. Simple branched tubular glands D. Compound branched tubular glands E. Compound alveolar/acinar glands F. Compound tubulo-alveolar/acinar glands
E. Compound alveolar/acinar glands
Which of the following glands specific to the GI system is characterized by single tube coiled in 3D, simple cuboidal secretory cells, and are typical integumentary sweat glands?
A. Simple tubular glands B. Simple coiled tubular glands C. Simple branched tubular glands D. Compound branched tubular glands E. Compound alveolar/acinar glands F. Compound tubulo-alveolar/acinar glands
B. Simple coiled tubular glands
Which of the following glands specific to the GI system is characterized by branched ducts with tubular, acinar, and tubular with acinar demilunes, secrete a mucoserous product, and are characteristic of submandibular salivary gland?
A. Simple tubular glands B. Simple coiled tubular glands C. Simple branched tubular glands D. Compound branched tubular glands E. Compound alveolar/acinar glands F. Compound tubulo-alveolar/acinar glands
F. Compound tubulo-alveolar/acinar glands
Which of the following glands specific to the GI system is characterized by branched duct system, tubular secretory portion, and are characteristic of Brunner’s glands in the duodenum?
A. Simple tubular glands B. Simple coiled tubular glands C. Simple branched tubular glands D. Compound branched tubular glands E. Compound alveolar/acinar glands F. Compound tubulo-alveolar/acinar glands
D. Compound branched tubular glands
Trace saliva flow from acinus to main duct; include changes in epithelium along the way
Acinus —> intercalated duct (squamous to low cuboidal epithelium) —> striated duct (cuboidal to columnar epithelium) —> interlobular duct (pseudostratified columnar) —> lobar duct (stratified columnar) —> main duct
Organelles in hepatocytes
RER = synthesis of plasma proteins
SER = synthesis of glycogen, lipids, and detox mechanisms
Golgi = glycosylation of secretory proteins and sorting of lysosomal enzymes
Lysosomes = degradation of aged plasma glycoproteins, iron storage
Peroxisomes = contain oxidases and catalases for beta-ox of FA’s and production/breakdown of hydrogen peroxide, also contain peroxins which are proteins involved in peroxisome biogenesis
Pathology of liver characterized by increased iron absorption and accumulation in lysosomal hepatocytes. complications include cirrhosis and cancer of liver
Hereditary hemochromatosis
Hereditary disorder of copper metabolism in which excessive deposits of copper in liver and brain lysosomes produce chronic hepatitis and chronic liver disease
Wilson’s disease
In chronic liver disease, perisinusoidal cells remain in quiescent, nonproliferative state but can proliferate when activated by ____ cells and _______
This leads to ______ and inflammatory cells in distorted portal space
Kupffer; hepatocytes
Fibrosis
What 3 conditions may result from long-term consumption of ethanol?
Fatty liver - reversible if EtOH consumption discontinued
Steatohepatitis - fatty liver + inflammatory reaction
Cirrhosis - collagen proliferation or fibrosis
Acute vs. chronic hepatitis
Acute = characterized by loss of appetite, nausea, vomiting, jaundice
Chronic = defined by presence of fibrosis, together with hepatocyte necrosis and inflammatory lymphocytic activity
Different types of viral hepatitis
HAV = caused by spread through ingestion of contaminated food/water; causes acute hepatitis that rarely becomes chronic
HBV = via sexual contact, blood/serum transfer thru shared needle in drug abuse; 10% develop chronic hepatitis
HCV = largely caused by blood transfusion; 50-70% develop chronic hepatitis. Therapy available via antiviral agents
