Histology of the Accessory Organs of the GI Tract Flashcards

1
Q

Functions of Digestive Glands:

A
  • Lubrication
  • Protection
  • Digestion
  • Absorption
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2
Q

3 Main Digestive Glands:

A

(1) Major Salivary Glands
(2) Exocrine Pancreas
(3) Liver

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3
Q

Digestive Gland: Major Salivary Glands

A

Associated with the oral cavity through independent excretory ducts

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4
Q

Digestive Gland: Exocrine Pancreas

A

Secretes its alkaline aqueous and enzymatic product into the duodenum

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5
Q

Digestive Gland: Liver

A

Endocrine and exocrine gland with extensive access to the blood circulation

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6
Q

Salivary Glands

A
  • Connective tissue capsule with septa, dividing the gland into lobes and smaller lobules – provides route for neurovasculature
  • Contains secretory cells and myoepithelial cells
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7
Q

Salivary Glands: Secretory Cells

A
  • Organized in an acinus
  • Produce salvia via ANS control
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8
Q

Salivary Glands: Myoepithelial Cells

A

Aid in release of secretions

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9
Q

Pathway of Saliva Flow:

A

(1) Acinus
(2) Intercalated Duct (low cuboidal epithelium)
(3) Striated Duct (simple cuboidal to columnar epithelium)
(4) Excretory Duct (simple cuboidal –> pseudostratified columnar or stratified cuboidal)

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10
Q

What is the largest salivary gland?

A

Parotid Gland

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11
Q

Parotid (Serous) Gland

A
  • Salivary gland
  • Acini consist of serous secretory cells
  • Pyramidal cells with a basally located nucleus
  • Prominent RER in basal region
  • Secretory granules visible in apical region
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12
Q

Parotid Gland: Duct Lengths

A

Equal lengths of excretory, striated, and intercalated ducts

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13
Q

Sublingual Gland

A
  • Branched tubule-alveolar gland
  • Acini consists of both serous and mucous cells, but is predominantly mucous
  • Lacks defined capsule but is divided by connective tissue into small lobes
  • Intercalated and striated ducts are poorly developed
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14
Q

Sublingual Gland: Duct Lengths

A

Ducts vary in length; Excretory Duct is longest and Striated Duct is shortest

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15
Q

Submandibular Gland

A
  • Acini consists of both serous and mucous cells, but predominantly serous cells
  • Mucous cell-containing acini are capped by serous demilunes
  • Intercalated ducts are shorter and striated ducts are longer than those in parotid gland
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16
Q

Submandibular Gland: Duct Lengths

A

Ducts vary in length; Excretory Duct is longest and Intercalated Duct is shortest

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17
Q

Pancreas

A
  • Large gland with endocrine and exocrine functions, but bulk of gland is exocrine
  • Thin layer of connective tissue forms capsule
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18
Q

Pancreas: Capsule

A
  • Thin layer of loose connective tissue
  • Divides gland into ill-defined lobules
  • Provides pathway for neurovasculature and ducts
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19
Q

Pancreas: Exocrine Component

A

Synthesizes and secretes enzymes that are essential for digestion in the intestine

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20
Q

Pancreas: Endocrine Component

A

Synthesizes and secretes hormones (insulin and glucagon) into the blood – regulate glucose, lipid and protein metabolism

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21
Q

Exocrine Pancreas: Serous Acinus

A
  • Functional unit of exocrine pancreas
  • Contains Pancreatic Acinar Cells (produce digestive enzymes)
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22
Q

In the exocrine pancreas, the intercalated duct begins as:

A

Centroacinar cells within the acinus

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23
Q

Centroacinar Cells

A
  • Duct cells located in the center of the pancreatic acinus
  • Continuous with the low cuboidal epithelium of intercalated duct
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24
Q

Centroacinar Cells secrete:

A

HCO3-, Na+, H2O

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25
Q

Histological Hallmarks of Exocrine Pancreas:

A
  • Acinar cells stain intensely
  • Centroacinar cells stain lightly
  • Islets are pink
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26
Q

Pancreatic Acinar Cell is Characterized by:

A
  • Well-developed RER
  • Prominent Golgi apparatus
  • Apical domain of zymogen granules
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27
Q

Zymogen Granules in the Pancreatic Acinar Cell

A

Contain about 20 different pancreatic proenzymes including trypsinogen, chymotrypsinogen, amylolytic enzymes (alpha amylase), lipases, deoxyribonuclease, and ribonuclease

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28
Q

Role of Trypsinogen and Chymotrypsinogen:

A

Digest proteins

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29
Q

Role of Amylolytic Enzymes (alpha amylase):

A

Digest carbohydrates

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30
Q

Role of Lipases:

A

Digest lipids

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31
Q

Role of Deoxyribonuclease and Ribonuclease:

A

Digest nucleic acids

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32
Q

Pancreatic Acinar Cells increase synthesis of Proteases with a ___-___ diet

A

Protein-rich

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33
Q

Pancreatic Acinar Cells increases synthesis of Amylases and decrease synthesis of proteases with ____-___ diet

A

Carbohydrate-rich

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34
Q

Pancreatic endocrine cells are organized into clusters called:

A

Pancreatic Islets (Islets of Langerhans)

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35
Q

Cells of the Endocrine Pancreas:

A
  • Alpha Cells
  • Beta Cells
  • Delta Cells
  • F-Cells
36
Q

Histology Hallmarks of Endocrine Pancreas

A
  • Acinar cells stain intensely
  • Centroacinar cells stain lightly
  • Islets are pink
37
Q

Intercalated Duct

A

Continuation of the centroacinar cells into the connective tissue stroma

38
Q

Endocrine Pancreas: Alpha Cells

A

Secrete Glucagon

39
Q

Endocrine Pancreas: Beta Cells

A

Secrete Insulin

40
Q

Endocrine Pancreas: Delta Cells

A

Secrete Somatostatin

41
Q

Endocrine Pancreas: F-Cells

A

Secrete pancreatic polypeptide

42
Q

Liver: Capsule

A
  • Enclosed in thin connective capsule lined with mesothelium of visceral peritoneum
  • Lacking where directly adheres to diaphragm/other organs
43
Q

Hepatocytes

A
  • Function in metabolism, storage, and bile production
  • Large polygonal shaped cells with eosinophilic cytoplasm and microvilli
  • Large spherical nuclei; many cells are binucleate, most are tetraploid
  • Contain numerous peroxisomes and lysosomes, extensive sER and large golgi
  • Cells are arranged in cellular ‘cords’
44
Q

Functional Units of the Liver

A
  • Hepatic Lobule
  • Portal Lobule
  • Liver Acinus
45
Q

Bile: Composition

A

Mixture of H2O, bile salts & pigments, phospholipids and electrolytes

46
Q

Bile: Function

A
  • Fat absorption
  • Excretion of cholesterol, bilirubin, iron, and copper
47
Q

Bile drains into:

A

Bile Canaliculus

48
Q

Bile Canaliculus

A
  • Structure bile drains into
  • Interconnected channels formed by hepatocyte plates and tight junctions
49
Q

Hepatic Lobule

A
  • Hepatocytes form irregular plates radiating from a central vein
  • Plates are supported by stroma of reticular fibers and are separated by sinusoids
50
Q

Peripheral angles of each hepatic lobule contain:

A

Portal Triad
- Venule branch of the portal vein
- Arteriole branch of the hepatic artery
- Bile ductules (branches of bile conducting system)

51
Q

Hepatic Lobule: Portal Triad - Branch of Portal Vein

A
  • Supplies nutrients and low O2 to hepatocytes
  • Drains into central vein
52
Q

Hepatic Lobule: Portal Triad - Arteriole Branch of Hepatic Artery

A
  • Supplies O2 to hepatocytes
  • Drains into central vein
53
Q

Hepatic Lobule: Portal Triad - Bile Ductules

A
  • Branches of bile conducting system
  • Bile travels away from the central vein
54
Q

Blood and Bile flow in ___ directions

A

Opposite

55
Q

Bile flows from center of the lobule to the periphery end near Portal Triads:

A

(1) Bile Canaliculi
(2) Canals of Hering
(3) Bile Ductules
(4) Bile Ductules merge & enlarge
(5) Right and Left Hepatic Ducts

56
Q

Canals of Hering

A

Composed of Cholangiocytes

57
Q

Cholangiocytes

A

Cuboidal epithelial cells of bile ducts

58
Q

Hepatic Sinusoids

A

Anastomosing capillaries that perfuse hepatocytes with portal and arterial blood

59
Q

Kupffer Cells

A
  • Stellate macrophages within endothelium of sinusoids
  • Larger than the endothelial cells
  • Detect and phagocytose effete (old and tired) erythrocytes
60
Q

Distinguishing feature of Hepatic Sinusoids:

A

Kupffer Cells

61
Q

Hepatic Stellate Cells (Ito Cells)

A
  • Cells with small lipid droplets that store Vitamin A and other fat-soluble vitamins
62
Q

Perisinusoidal Space

A
  • Located between hepatocytes and the sinusoidal endothelium
  • Facilitates uptake/release of nutrients, proteins, and potential toxins
  • Creates a potential space for exchange of materials between blood and hepatocytes
63
Q

Components of Perisinusoidal Space

A
  • Microvilli project into space
  • Plasma fills space and directly bathes the mircovilli
64
Q

Periportal Space

A
  • Where excess fluid from the perisinusoidal space is collected; fluid is then drained by lymphatic vessels
  • Located at edges of canals between stromal connective tissue and hepatocytes
  • Ito cells found here
65
Q

Portal Lobule: Organization

A
  • Central axis is bile duct (portal triad)
  • Triangular block of tissue that outlines bile drainage pathway from adjacent lobules into same bile duct
66
Q

Hepatic Acinus: Organization

A
  • Diamond-shaped
  • Occupies parts of adjacent classic lobules
  • Hepatocytes are arranged in concentric zones around a short axis
67
Q

Hepatic Acinus arrangement is based on:

A

O2 gradient along sinusoids of adjacent lobules

68
Q

Hepatic Acinus: Cells in Each Zone

A

Different metabolic functions and distribution of hepatic enzymes; explains liver damage resulting from ischemia and/or exposure to toxic substances

69
Q

Structure-Function Relationships of the Liver: Classic Lobule

A
  • Emphasizes endocrine function of hepatocytes as blood flows toward the central vein
  • Drains blood from portal vein and hepatic artery to the hepatic or central vein
70
Q

Structure-Function Relationships of the Liver: Portal Lobule

A
  • Emphasizes hepatocytes’ exocrine function and flow of bile from classic lobules towards bile duct in portal triad
  • Drains bile from hepatocytes to the bile duct
71
Q

Structure-Function Relationships of the Liver: Hepatic Acinus

A
  • Emphasizes different oxygen and nutrient contents of blood at different distances along the sinusoids
  • Supplies oxygenated blood to hepatocytes
72
Q

Hepatic Acinus: Periportal Cells of Zone I

A
  • Receive most oxygen and nutrients
  • Closest to Portal Vein and Hepatic Arteriole
73
Q

Hepatic Acinus: Periportal Cells of Zone II

A
  • Receive moderate oxygen and nutrients
74
Q

Hepatic Acinus: Periportal Cells of Zone III

A
  • Receive least oxygen and nutrients
  • Closest to Central Vein
75
Q

Biliary Tree

A
  • Consists of hepatic, cystic, and common bile ducts
  • Lined with mucous membrane having a simple columnar epithelium of cholangiocytes
  • Many variations
76
Q

Cystic Duct has some areas with:

A

Mucous Glands

77
Q

All ducts of biliary tree have:

A

Thin Lamina Propria and Submucosa surrounded by a thin muscularis externa

78
Q

Muscularis layer of biliary tree becomes thicker near the ____ and forms a sphincter that regulates ___ flow into the ___

A
  • Duodenum
  • Bile
  • Duodenum
79
Q

Gallbladder: Mucosal Layer

A

Highly folded mucosa lined with simple columnar epithelium of cholangiocytes with microvilli

80
Q

Gallbladder: Lamina Propria

A

Sits deep to the mucousa

81
Q

Gallbladder does that have ___ ____ or ___ layers

A
  • Muscularis Mucosae
  • Submucosal
82
Q

Gallbladder: Muscularis Externa

A
  • Bundles of muscle fiber oriented in all directions
  • Facilitate emptying of the organ
83
Q

Gallbladder: External Adventitia & Serosa

A

External Adventitia is against the liver but serosa is where the liver is exposed to the peritoneal cavity

84
Q

Rokitansky-Aschoff Sinuses

A

Deep diverticula of mucosa that may extend through muscularis externa

85
Q

Rokitansky-Aschoff Sinuses develop as a result of:

A

Hyperplasia and herniation of epithelial cells through the muscularis externa

86
Q

Rokitansky-Aschoff Sinuses may experience bacteria accumulation which causes:

A

Chronic inflammation and increased risk for gallstones