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GI Midterm > Digestive Glands > Flashcards

Digestive Glands Flashcards

1
Q

functions of digestive glands

A

lubricate, protective, digestive, and absorptive functions

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2
Q

major digestive glands

A

i. salivary—parotid, submandibular sublingual

ii. exocrine pancreas and liver (and gallbladder)

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3
Q

how to classify exocrine glands

A

a. Structure of the excretory duct: divided into simple (unbranched duct) and branched or compound (branched duct)
b. Structure of the secretory units:
i. Tubular
ii. Alveolar (acinar)
c. Secretory:
i. Mucous
ii. Serous—water fluid with zymogen or proenzyme granules
d. Secretory mechanism:
i. Merocrine—exocytosis
ii. Holocrine—whole cell
iii. Apocrine—gland releases its products together with a small amount of the apical cytoplasm of the secretory cell

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4
Q

functions of saliva

A

a. Lubrication—mucus and water in saliva lubricate the mucosa of the tongue, cheeks, and lips during speech and swallowing, dissolve food for the function of the taste buds, and moisten food for easy swallowing
b. Protective function—depends on the antibacterial function of 3 constituents of saliva
- lysozyme, lactoferrin, IgA
c. Digestive function—relies on…
i. Amylase—initiates the digestion of carbohydrates in the oral cavity
ii. Lingual lipase—participates in the hydrolysis of dietary lipids

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5
Q

lysozyme

A

attacks the walls of bacteria

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6
Q

lactoferrin

A

chelates iron necessary for bacterial growth

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7
Q

IgA

A

neutralizes bacteria and viruses

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8
Q

parotid gland

A

i. Exclusively serous acini
ii. Enzymes: amylase, peroxidase, lysozyme
1. Antimicrobial proteins , including proline rich proteins, histatins, cystatins, and statherin, have important implications for bacterial clearance, selective bacterial aggregation on the tooth surface, and control of mineralization and demineralization

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9
Q

mumps, rabies, tumors

A
  1. Parotid gland is the primary target of the rabies and mumps virus transmitted in saliva containing the virus
  2. Mumps virus causes transient swelling of the parotid gland and confers immunity
  3. 2 complications of mumps:
    a. orchitis
    i. bilateral orchitis caused by mumps virus can cause sterility in males
    b. meningitis
  4. the parotid gland is the most frequent site for slow growing benign salivary gland tumors
    a. surgical removal is complicated by the need to protect the facial nerve
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10
Q

submandibular gland

A

i. Mixed serous and mucous
ii. Serous demilunes
iii. Pure mucous acini rare
iv. Mucous cells secrete mucin which aids in the lubrication of the food bolus as it travels thru the esophagus
v. In addition, the serous cells produce salivary amylase, which aids in the breakdown of starches

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11
Q

sublingual gland

A

i. Mixed serous and mucous
ii. Mucous acini predominate
iii. Sublingual gland is a branched tubuloalveolar gland with both serous and mucous cells
iv. Most secretory units are mucous
v. Exit directly from 8-20 excretory ducts

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12
Q

endocrine pancreas

A
  1. Endocrine component is the islet of Langerhans
    a. Surrounded by serous acini
  2. The main function of the endocrine pancreas is the regulation of glucose metabolism by hormones secreted into the bloodstream—signals go here to release insulin
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13
Q

exocrine pancreas

A
  1. The functional histologic unit of the exocrine pancreas is the acinus
    a. The lumen of the acinus is the initiation of the secretory-excretory duct system and contains centroacinar cells that are unique to the pancreas
    i. Centroacinar cells are continuous with the low cuboidal epithelial lining of the intercalated duct
    ii. Found at the center of the pancreatic acinus
    iii. Centroacinar cells are spindle shaped and they are known as duct cells
    iv. Secrete a bicarbonate solution under stimulation by the hormone secretin
    v. Secrete mucin
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14
Q

CCK and secretin

A

i. cholecystokinin (CCK) and secretin increases the flow of pancreatic fluid
1. CCK produced in enteroendocrine cells of the duodenal mucosa, binds to specific receptors of acinar cells and stimulate the release of zymogen

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15
Q

amylase

A

i. A carbohydrate rich diet results in the selective synthesis of amylases and a decrease in the synthesis of proteases
1. Amylase gene expression is regulated by insulin—internal circulation within the pancreas is very important

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16
Q

acute pancreatitis

A

i. Zymogen granules contain inactive proenzymes that are activated within the duodenal environment
ii. A premature activation of pancreatic enzymes (trypsinogen to trypsin) and the inactivation of trypsin inhibitor results in the auto digestion of pancreatic acini
iii. Condition usually follows heavy meals or excessive alcohol ingestion
iv. Clinical features include: severe abdominal pain, nausea, vomiting, and rapid elevation of amylase and lipase in serum (within 24-72 hours)

17
Q

blood supply to the liver

A

i. Portal V—transports blood from GI tract, spleen, and pancreas
ii. Hepatic A—to liver via interlobar and interlobular As.
1. Blood from branches of the Portal A and Hepatic A mixes in the sinusoids of the liver lobules and converges at the central venule of the liver lobule
a. Central venules converge to form the sublobular veins, and blood returns to the IVC following the collecting Vs and hepatic Vs. pathway

18
Q

hepatic lobule

A

i. Structural and functional unit of the liver is the hepatic lobule
ii. Hepatic lobule consists of anastomosing plates of hepatocytes limiting blood sinusoidal spaces
iii. A central venule in the core of the hepatic lobule collects the sinusoidal blood containing a mixture of blood supplied by branches of the portal V and the hepatic A

19
Q

classic hepatic lobule

A

a. hexagonal lobule
b. surrounding a central V
c. portal triads at the angles

20
Q

portal lobule

A
  1. based on bile drainage with the portal triad at the center of the lobule
    a. triangular arrangement
    b. center of the triangle is bile duct collecting from 3 hepatic lobules
    c. angles are the central Vs of 3 hepatic lobules
21
Q

liver acinus

A
  1. based on the zone gradient distribution of hepatic A—derived oxygenated blood along the sinusoidal spaces
    a. based on oxygen gradient of venous sinusoids of adjacent lobules
    b. divided into 3 zones based on the blood supply to the hepatocytes from the branch of the hepatic A
22
Q

kupffer cells

A

macrophages of the liver involved in recycling old RBCs

23
Q

portal triad and the draining of bile

A
  1. at the corner of each lobule is the portal triad, composed of branches of the hepatic portal V, hepatic A, bile duct, and nerve
    a. bile drains from the hepatocytes by many small bile ducts that unite to form the main bile duct of the liver, the hepatic duct
    i. this joins the cystic duct which leads from the gall bladder to form the common bile duct which drains into the duodenum
24
Q

space of Disse

A
  1. endothelium which lines liver sinusoids is fenestrated and lacks a continuous basement membrane (discontinuous capillaries)
  2. the space b/w the fenestrated endothelium and the cords is named the space of Disse
  3. the fenestrations permit blood plasma to wash freely over the exposed surface of the hepatocytes thru the space of Disse
  4. microvilli of hepatocytes extend into this space, allowing proteins and other plasma components from the sinusoids to be absorbed by the hepatocytes
25
Q

ito cells

A
  1. Ito cells are stellate cells of the liver—located at intervals within the space of Disse
  2. These cells function as storage sites for fat and vitamin A
26
Q

metabolism of bilirubin

A

i. end product of heme catabolism
ii. originates from senescent RBCs destroyed in the spleen by macrophages
iii. macrophages convert heme into biliverdin, which is transformed into unconjugated bilirubin released into the blood circulation
1. in blood circulation, bilirubin forms a complex with albumin
2. when the bilirubin albumin complex reaches the hepatic sinusoids, albumin detaches and bilirubin is internalized by hepatocytes

27
Q

alcoholism and fatty liver

A

i. hepatocytes participate in the metabolism of ethanol
ii. long term consumption of ethanol results in fatty liver
1. this is a reversible process is alcohol ingestion is discontinued
iii. gives predisposition to cirrhosis (collagen proliferation of fibrosis of the liver) and hepatocellular carcinoma (malignant transformation of hepatocytes)

28
Q

gallbladder

A

a. main functions: storage, concentration, release of bile
i. dilute bile form the hepatic ducts is transported thru the cystic duct into the gallbladder
ii. after concentration, bile is discharged into the common bile duct then to the duodenum
1. but a sphincter has to be open for bile to go thru
2. if the sphincter is closed, bile moves up cystic duct and up into the gallbladder to be stored

GI Midterm (12 decks)

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