11/16: Accessory Digestive Organs Flashcards
(109 cards)
1
Q
What are the major functions of the liver?
A
- Detoxification of metabolic waste (e.g., deamination of AA’s –> urea)
- Metabolism & detoxification of drugs & toxins (e.g., alcohol,
antibiotics) - Destruction of senescent RBC’s
- Recycling of Hb via synthesis & secretion of bile
- Synthesis of plasma proteins (clotting factors, albumin,
lipoproteins) - Miscellaneous metabolic functions (fat, carbohydrate,
proteins, etc.)
2
Q
How do the products of digestion enter the liver via?
A
Hepatic portal vein
3
Q
What percent of blood is carried to the liver via the hepatic portal v?
A
75-80%
4
Q
What else does the hepatic circulation carry?
A
potentially toxic compounds absorbed from diet to liver to be conjugated or detoxified
5
Q
How is oxygenated blood supplied to the liver via?
A
Hepatic artery, a branch of celiac trunk
6
Q
What does the hapatic artery split into?
A
R/L hepatic Aa in hepatic lobules
7
Q
What percent of blood does the hepatic artery carry?
A
20-25% of blood to liver
8
Q
What does the hepatic artery blood mix with?
A
UNoxygenated blood from portal V to perfuse liver cells
9
Q
Describe the liver in regardes to nutrients and O2
A
Nutrient rich, but O2 poor environment
10
Q
What is the venous drainage via?
A
Lobules via central vv -> hepatic v -> IVC
11
Q
What are the cells found in the liver?
A
Hepatocytes
Endothelial cells
Kupffer cells
Stellate cells (Ito cells)
12
Q
What is the main functional cell?
A
Hepatocytes
13
Q
How are hepatocytes arranged?
A
In plates or cords around sinusoids
14
Q
Where are endothelial cells found?
A
Line the sinusoids
15
Q
What are liver-specific macrophages?
A
Kupffer cells
16
Q
What cells store vitamin A?
A
Stellate cells (Ito cells)
17
Q
What is the structure of hepatocytes?
A
Diploid, but some polyploid or binucleate
18
Q
What do hepatocytes contain?
A
Large #s of cytoplasmic granules (rER and lysosomal products) and storage products
19
Q
What do aging hepatocytes accumulate?
A
Brown pigment, lipofuscin
20
Q
Describe the structure and arrangement of individual hepatocytes
A
polygonal, arranged in anastomosing cords
21
Q
What are hepatocytes paralleled by?
A
Venous sinusoids
22
Q
What are sinusoids lined by?
A
Sinusoidal lining cells, a discontinuous endothelium, with gaps between endothelial cells
23
Q
What are hepatic cords and sinusoids supported by?
A
Meshwork of reticulin fibers (Type III collagen)
24
Q
What is found within sinusoids and space of disse?
A
Phagocytic Kupffer cells
25
What is occasionally between hepatocytes?
Stellate or Ito cells
26
What are stellate or Ito cells?
fat- storing cells containing lipid droplets, used for Vit A & D, storage
27
Describe the cytoplasm of a kupffer cell
Packed with black carbon particles
28
How can Kupffer cells be recognized?
by their oval nuclei closely associated with sinusoidal spaces
29
Describe the appearance of endothelial cells
Similar to kupffer, but with thinner (flatter) and denser
nuclei and with less conspicuous cytoplasm
30
What do hepatocytes that comprise the hepatic cords have?
Round nuclei surrounded by abundant cytoplasm
31
What is the function of Kuppfer cells?
remove foreign particles, they also work with the spleen to destroy old RBCs
32
What happens to a stellate cell in liver injury?
Becomes a transitional cell or
myofibroblast-like cellW
33
What is the function of a stellate cell in liver injury?
capable of synthesising collagen types I, III and IV as well as lamini
34
What is a thin, discontinuous, highly fenestrated endothelium that does not rest on a basement membrane?
Hepatic sinusoids
35
What are hepatic sinusoids separated from the hepatocytes by?
The space of Disse or the perisinusoidal space
36
Where are hepatic sinusoids found?
In the liver between a hepatocyte and a sinusoid
37
What do hepatic sinusoids contain?
Blood plasma
38
Where do microvilli of hepatocytes exten?
Into the hepatic sinusoids
39
What does the extension of microvilli allow for?
Proteins and other plasma components from the sinusoids to be absorbed by the hepatocytes
40
What kind of vascular channels are found within hepatic sinusoids?
Low resistance that allow blood to come into contact with hepatocytes over a large surface area
41
What is the flow of bile made by?
Hepatocyte & secreted into bile canaliculi between cells
42
What are the 3 concepts of liver lobules?
Classic hepatic lobule
portal lobule
Hepatic acinus of rappaport
43
What is the organization of hepatic lobules?
Cords of hepatocytes arranged in lobules
44
What is a classic lobule?
Based on blood flow; roughly hexagonal, with central vein in middle of lobule
45
What is the outer margin of each lobule delimited by?
Thin, connective tissue septum
46
What is located at each "corner" of a classic lobule?
Portal tracts/triads
47
What do portal tracts/triads contain?
Hepatic A, br. portal V, L, and bile duct
48
How does blood enter from portal tracts, percolates through?
Sinusoids of lobule
49
What drains portal tracts?
Central vein
50
What is a triangular area; based on bile flow (opposite to blood flow)?
Portal lobule
51
What makes up a portal lobule?
Portal triad in center and central vv at corners
52
What is an acinus?
Diamond shaped region between neighboring central vv
53
Where are central vv located in hepatic acini?
Along longitudinal axis with portal tracts at sides
54
What aspects make up the hepatic ascini?
Blood flow, oxygenation, metabolism and pathology
55
What is an acinus divided into?
3 zones - 1,2,3
56
What do hepaticytes in different zones have?
Different metabolic environments
57
Describe the 3 zones of the hepatic acini
Zone 1—(perilobular zone = periportal)— closest to portal tract
Zone 2—(intermediate zone)
Zone 3—(centrolobular zone)—furthest from portal tract, closest to central V
58
What receives most oxygenated blood;
also most susceptible to toxic injury?
Zone 1
59
What receives least oxygenated blood; most
susceptible to ischemic injury?
Zone 3
60
How does the liver function in detoxification or metabolism of drugs, toxins, metabolites?
Via microsomal mixed function
oxidase system of sER, or peroxidases of peroxisomes (P450 system)
61
What is cirrhosis characterized by?
hepatic degeneration & necrosis, followed by fibrosis & nodular regeneration
62
What is associated
with cirrhosis (due to fibrosis,
blockage of blood flow)?
Portal hypertension
63
Does the liver have the ability to regenerate?
Yes
64
What is the muscular sac located in depression
along surface of liver?
Gallbladder
65
What is the gallbladder used for?
Store & concentrate bile;
volume ~100 ml
66
What is the gallbladder lined by?
Simple columnar epithelium
with apical microvilli
67
What is the microvilli in the gallbladder used for?
Resorption of water
68
What does the gallbladder lack?
A muscularis mucosae
69
What is the lamina propria highly folded with?
Occassional tubuloalceolar mucus glands
70
What stimulates contraction of gallbladder?
CCK (Cholecystokinin)
71
What are components of bile?
Water, ions, electrolytes, cholesterol + phospholipids (= lecithin), bile acids (= bile salts) & bile pigments
72
What is the best known bile pigment?
Bilirubin
73
What is the non-sol breakdown product of Hb
Bilirubin
74
What happens in a failure to absorb bilirubin or failure to conjugate it and secrete?
accumulation of bile
pigments & jaundice
75
What does supersaturation of bile cause?
Gallstones (biliary calculi, cholelithiasis)
76
What does obstruction of bile ducts (choledocolithiasis) cause?
Bile stasis, or jaundice (icterus) if severe
77
What is chronic inflammation of the gallbladder?
Cholecystitis
78
What is the removal of the gallbladder?
Cholecystectomy
79
What happens following a cholecystectomy?
unable to concentrate bile; need to limit ingestion of fats
80
What is a highly lobulated gland with thin, connective tissue capsule, located in bend of duodenum?
Pancreas
81
What components does the pancreas have?
Endocrine and exocrine
82
Where is ductless endocrine pancreatic tissue located?
In islets of langerhans
83
Most of the pancreas is ______
Exocrine (i.e. with ducts) - a compound, acinar, serous gland
84
What is densely packed in the pancreas?
Serous acini contain pyramidal secretory cells surrounding a central lumen (duct)
85
What do acinar cells contain?
Zymogen granules (inactive enzyme precursors)
e.g., trypsinogen (=
protrypsin),
chymotrypsinogen (=
prochymotrypsin),
amylase, lipase
86
What are proteases?
Trypsin and chymotrypsin
87
What breaks down carbohydrates?
Amylase
88
What do lipases digest?
Lipids
89
Where do the secretory acini empty into?
Intercalated ducts
90
What can intercalated ducts differentiate into?
Add bicarbonate and water to pancreatic sections; neutralize acidic chyme from stomach -> optimal pH for pancreatic enzymes
91
What forms the beginning of intercalated ducts?
Duct cells
92
What is sometimes visible in the center of acini?
Centro-acinar cells
93
Where do intercalated ducts empty into?
Larger intralobular ducts
94
Where do intralobular ducts exit into?
Interlobular (=extralobular) ducts
95
How do pancreatic secretions enter the duodenum?
Via pancreatic duct at major duodenal papilla
96
What are the principle regulators of exocrine pancreas?
Polypeptide hormones secreted by enteroendocrine (APUD) cells
97
What is primarily secreted by stomach?
Gastrin
98
What secretes gastrin?
G cells of pyloric stomach
99
What does gastrin do?
Stimulates secretion of pancreatic fluid
100
What 3 things are secreted by duodenum?
Secretin
CCK
Enterokinase
101
What is secretin secreted by?
S cells
102
What does secretin do?
stimulates secretion of bicarbonate by cells of intercalated ducts
103
What is CCK (Cholecystokinin = pancreozymin) secreted by?
I cells
104
What does CCK do?
Stimulates acinar cells to secrete zymogen
105
What does enterokinase do?
converts trypsinogen -> trypsin (within small intestine), which converts chymotrypsinogen -> chymotrypsin (digests proteins)
106
What prevents the pancreas from digesting itself?
Cascade rxn
107
What is an autodigestion of pancreas brought on by alcoholism?
Pancreatitis
108
What does the cascade rxn break down?
Premature conversion of chymotrypsinogen to chymotrypsin & autolysis
109
Is severe, acute pancreatitis fatal?
Yes within hours
