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Dental Histology - Digestive
Exam 3
48
Medical
Professional
11/04/2008

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Cards

Term
Pancreas
Definition
-both exocrine and endocrine
-exocrine = production and release of digestive                             enzymes 
-digestive hormones produced in aggegates of cells             called: ISLETS OF LANGERHANS
              -eventually released into bloodstream
 
 
Term

Exocrine component of Pancrease

 

6 enzymes 

Definition
1. lipase = breaks down fats
2. carboxypeptidase = breaks down peptide bonds
3. trypsin = hydrolyzes peptide bonds
4. chymotrypsin = cleaves carboxyl links of AA
5. amylase = breaks down startch and glycogen
6. elastase = hydrolyzes elastin 
Term
Pancreatic Secretion of Exocrine Component
Definition
-controlled by 2 hormones and a neurotrasmitter
-hormones are synthesized by enteroendocrine cells
           -in duodenum
 
Hormones:
      -secretin
      -cholecystokinin
Neurotransmitter:
      -acetylcholine
Term

Secretin in Pancreas

(Exocrine) 

Definition
-produced by enteroendocrine cells of small intestine
 
-causes buffer to be released by ductal cell
 
-insulin release 
Term

Cholecystokinin in Pancreas

 

(Exocrine) 

Definition
-produced by APUD cells of small intestine
 
-causes gall bladder contraction
-slows gastric emptying time
-stimulates pancreas enzyme secretion 
Term

Acetylcholine in Pancreas

 

(Exocrine) 

Definition
-released from postganglionic parasympathetic fibers
Term
Exocrine Structure of Pancreas
Definition
-compound acinar gland (similar to parotid)
-acini made of:
    -acinar
    -centroacinar cells
           -(intra-acinar extension of intercalated ducts) 
-NO striated ducts
    -intercalated ducts merge into columnar                             interlobular ducts
-Interlobular ducts lead to 2 main ducts of pancreas
    1. duct of Santorini (accessory but really main) 
    2. duct of Wirsung (main) 
Term
Interlobular ducts lead to 2 main ducts of pancreas
   
Definition
1. duct of Santorini (accessory but really main) 
     2. duct of Wirsung (main) 
 
-duct cells produce bicarbonate-rich buffer solution             which neutralizes the acidic gastric contents             going into duodenum 
Term
Endocrine Component of Pancreas
Definition
-consists of ISLETS OF LANGERHANS
    -islets distributed throughout pancreas 
                    BUT
    -more numerous in the tail of gland
Term

Structure of Endocrine Pancreas

 

(Islets of Langerhans) 

 

 

Definition
-round to polygonal in shape
-surrounded by rich capillary network
-thin capsule of reticulin fibers seperae each islet             from exocrine pancreatic parenchyma 
 
Term
5 types of cells comprise the islets
Definition
1. α (A) cells
 
2. β (B) cells 
 
3. δ (D) cells
 
4. F (PP) cells
 
5. G cells
Term
α (A) cells
 
Definition
-large cells with dark cytoplasm
-found on periphery of islet
-constitute 20% of islet cells
-secrete glucagon (increase blood sugar)
 
Term
Glucagon from α (A) cells
Definition
-released when blood glucose levels are low
-acts on hepatocytes
        -breaks down glycogen into glucose
        -releases it into bloodstream
-activates gluconeogenesis
 
Term
β (B) Cells
Definition
-comprise 70% of islet
-smaller in cell and granule size than α cell
-secrete insulin (decreases blood sugar) 
Term
Insulin from β (B) Cells
Definition
-binds to insulin receptors on cell
    (especially skeletal muscle, liver and adipose)
-allows glucose to be taken into cell
-encourages glucose utilization by cells
-increases protein synthesis
-formation and storage of neutral lipids 
Term
δ (D) Cells
Definition
-5% of islets cells
-secrete somatostatin
     
Term
Somatostatin in δ (D) Cells
Definition
-both paracrine and endocrine function
 
Paracrine = inhibit hormone release in adjacent α and β
                 cells of pancrease
 
Endocrine = reduces smooth muscle contractions of                      alimentary tract and gall bladder
Term
F (PP) Cells
Definition
- 1% of islet
-secrete pancreatic polypeptide
        -inhibits exocrine pancreatic secretions
 
Term
G Cells
Definition
- 1% of islet cells
-secrete gastrin
    -stimulate production of HCl by parietal cells in                     stomach 
Term
Liver
Definition
-2nd largest organ 
-processes and stores the nutrients absorbed by                 digestive tract 
 
Term
Liver Structure
Definition
-surrounded by a thin capsule (Glisson's capsule)
 
Capsule extends into orgad subdividing it into
            lobes and lobules 
 
 
Term

Majr Divisions of Liver

(3) 

Definition
1. Liver Lobule
2. Portal Lobule
3. Hepatic Acinus 
Term
Liver Lobule
Definition
-classic lobule 
-poorly-demarcated hepatocytes form hexogonal struc
-contains portal triad
        =point where 3 lobules contact each other
-center of lobule has central vein
   -has converging plates of anastomosing                         hepatocytes enclosing sinusoids
 
Term
Portal Triad of Liver Lobule
Definition
=point where 3 lobules contact each other 
 
Contains:
-connective tissue
-branches of hepatic artery
-portal vein
-bile duct
-sometimes lymphatics 
Term
Portal Lobule
Definition
-bile drainage
-triangular structure
-portal triad at the center
-central vein at the tip of each angle 
Term
Hepatic Acinus
Definition
-diamond shaped
-supplied by terminal branch of distributing veins
        -from protions of 2 adjacent liver lobules
-divided into zones based on proximity to distributing         veins
 
zone I
zone II
zone III 
Term
Hepatic Acinus - Zone I
Definition
-closest to distributing vein
-first to affect or be affected by the passing blood
-actively synthesizing proteins 
Term
Hepatic Acinus - Zone II
Definition
Middle Zone
Term
Hepatic Acinus - Zone III
Definition
-encountes blood on its way to central vein
    =blood has been altered by zones I and II
             -largely deoxigenated blood
-hepatocytes play a role in detoxification
Term
Liver Blood Supply
Definition
-recieves blood from 2 sources
     1. portal vein
     2. hepatic artery
Term
Liver Blood Supply from Portal Vein
Definition
-80% blood supply
-oxygen poor
-nutrient rich
-from pancreas, spleen, and intestines
 
Term

Liver Blood Supply from Portal Vein

 

(the flow) 

Definition
-in triads: branches of portal vein called:
                    portal venules
-branches that surround periphery of lobues called:
                    distributing veins
-distributing veins have inlet venules emerging which                     lead to sinusoids
-sinusoids lead to central vein
-central vein merges with sublobular vein at base of                     lobule
-sublobular vein joins with other sublobular vains to                     form hepatic veins
Term
Liver Blood Supply from Hepatic Artery
Definition
- 20% blood
- oxygen rich
- branches to form interlobular arteries
        - some occupy portal area
        - some empty directly into sinusoids
 
Term
Blood In Sinusoids
Definition
Contain BOTH arterial and venous blood!!!
Term
Hepatocyte (Liver)
Definition
-polyhedral cells
-1-2 nuclei form anastomosing plates
        -converge towards central vein
-exposed at several points to walls of sinusoids or                 adjacent hepatocytes
*space between adjacent hepatocytes is called:
           Bile Canaliculus
 
Term
Functions of Hepatocyte
Definition
1. Storage - vitamins (mostly A,D,B12)
2. Transformation and Detoxification -
                            inactivation on drugs and toxins 
3. Protein Synthesis - mainly blood proteins 
              (for coagulation, immune system, transport)
4. Metabolism - lipids, carbohydrates, proteins
5. Excretion - bilirubin
                       (breakdown products of hemoglonin)
6. Bile Production - absorbs fats, eliminates most of             the cholesterol produced by liver, excretes                 the breakdown products of blood 
Term
Sinusoids
Definition
Space of Disse: seperate endothelial cells of the                                 sinusoids from the hepatocytes
Contains:
-hepatocyte microvilli
-nonmyelinated nerve fibers
-Ito cells (fat storage)
-pit cells (type of NK cell)
 
phagovytic Kupffer cells - reside within sinusoids
(macrophages) 
Term
Bile
Definition
Composed of:
    -cholesterol
    -lecithin
    -fatty acids
    -bilirubin glucuronide
    -bile salts
    -water
 
-most of the componets are absorped in intestine and         transported via blood to bile canaliculi 
Term
Bile Canaliculi
Definition
-initial part of bile duct system
-consist of narrow channels b/w adjacent hepatocytes
-microvilli protrude into the spaces b/w hepatocyes 
-reach endpoint near portal areas
    =bile flows in opposite direction of blood
-at periphery of liver lobule, bile moves in bile                 ductules (clear cuboidal cells), then continues to         bile ducts of portal triad
-numerous bile ducts converge to form right and left         hepatic ducts 
Term
Gall Bladder
Definition
-hollow organ
-rests along underside of liver

Term
Gall Bladder Function
Definition
-bile storage
-bile concentration
-bile release 
Term
Gall Bladder Communication
Definition
Communicates with hepatic duct via cystic duct to form common bile duct
Term
Mucosa of Gall Bladder
Definition
-highly folded
-simple columnar epithelium
-lamina propria composed of:
    -areolar connective tissue
    -discontinuous muscularis externa
    -serosa
-NO muscularis mucosa 
Term
Gall Bladder and Tubuloacinar Galnds
Definition
-tubuloacinar glands near cystic duct
-produce and release mucose into bile 
Term
Gall Bladder Contraction
Definition
-produced with cholecystokinin
        -CCK released by enteroendocrine cells of small             intestine 
                 -CCK stimulated by dietary fat present                             within lumen
 
Term

ampulla of Vater

(Gall Bladder) 

Definition
-empties into duodenum
Term
sphincter of Oddi
Definition
-surrounds junction of common bile duct and                         pancreatic duct
-smooth muscle
-governs amount of bile being pushed through 
Term

Rokitansky-Aschoff Sinuses

(Gall Bladder) 

Definition
-technically don't exist
-just an extension of the lumen
    (a recesses / inpocketing)
-communicates with lumen 
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