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GI Final > Histology of GI Glands > Flashcards

Histology of GI Glands Flashcards

1
Q

Digestive Glands

A
  • have lubricating, protective, digestive, absorptive functions mediated by their secretory products
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2
Q

What are the 3 main digestive glands?

A

1) Major salivary glands
2) Exocrine pancreas
3) Liver

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3
Q

Major Salivary glands

A

associated with the oral cavity through independent excretory ducts

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4
Q

Exocrine pancreas

- digestive glands

A

secretes its alkaline aqueous and enzymatic product into the duodenum

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5
Q

Liver

-main digestive glands

A

endocrine and exocrine gland with extensive access to the blood circulation

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6
Q

Exocrine glands

A
  • secrete mucus, hormones, enzymes

- simple invagination of epithelium, or may lack contact with epithelial surface

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7
Q

Parts of exocrine glands

A
  1. Acinus

2. Duct

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8
Q

Acinus exocrine glands

A

blind-sac of secretory cells that synthesize and release product

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9
Q

Duct exocrine glands

A

conducting passageway for product to be released

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10
Q

Salivon

- what does it include?

A

basic secretory unit of salivary glands

- includes acinus, intercalated duct, excretory duct

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11
Q

Salivary Glands

  • histology
  • nerve innervation
A
  • secretory cells produce saliva
  • controlled by ANS

-CT capsule with SEPTA, dividing the glands into LOBES (interlobar septa) and smaller lobules ( interlobular septa)

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12
Q

Saliva

A
  • lubricates and cleanses the oral mucosa, protecting it from dryness
  • contains immunoglobulins, minerals, electrolytes, buffers, enzymes and metabolic waster
  • aids in digestion of food via enzymes and maintenance of tooth integrity
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13
Q

How are secretory cells organized?

A

in an ACINUS

1) mucous acini
2) serous acini
3) mucoserous
4) myoepithelial cells

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14
Q

Mucous acini

A

cloudier-looking cytoplasm

- produce thick, glycoprotein-rich product

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15
Q

Serous acini

A

clear-staining cytoplasm

- produce a water-based product

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16
Q

Mucoserous

A

contain a core of mucous cells surrounded by serous demilune

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17
Q

Myoepithelial cells

A

located between epithelial cells & basal lamina

- assisted in moving secretory products toward the excretory duct

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18
Q

Mixed acini

A

contain serous and mucus-producing cells

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19
Q

Conventional fixation

A

serous cells have comprised the Demilune but this is an artifact of fixation

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20
Q

Rapid fixation

A

both mucous and serous cells are aligned in the same row to surround the lumen of secretory acinus

NO serous demilune is present

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21
Q

Effects of expansion of mucous cells during fixing

A
  • increases volume

- displaces serous cells from their original position

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22
Q

Pathway of Saliva Flow

A

Acinus-> intercalated duct (low cuboidal epithelium)-> striated duct (simple cuboidal to columnar epithelium)-> excretory duct (simple cuboidal-> psuedostratified columnary or stratified cuboidal)

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23
Q

Parotid (Serous) Gland

- hallmarks

A

Largest salivary gland
- adipocytes scattered throughout

Acini consist mainly of serous secretory cells

  • pyramidal cells with basally located nucleus
  • Prominent RER in basal region
  • Secretory granules visible in apical region

HALLMARK: SEROUS ONLY, LARGE AMOUNTS OF ADIPOSE TISSUE, CN VII PASS THROUGH

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24
Q

Sublingual Gland

A
  • branched tubule-alveolar gland with both serous and mucus cells
  • mixed gland, but predominantly mucous
  • lack defined capsule, but is divided by CT into small lobes
  • intercalated and striated ducts are poorly developed
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25
Q

Submandibular Gland

A
  • serous cells are predominant, but mucous cells are present
  • Mucous cell- containing acini are capped by serous demilunes (bonnet)
  • Myoepithelia cells control serous secretions
  • intercalated ducts are shorter and striated ducts are longer than those in parotid gland
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26
Q

Pancreas

  • define
  • description
  • components
A

large gland with endocrine and exocrine functions (mostly exocrine)

thin layer of loose CT forms capsule

Divides glands into ill-defined lobules, neurovasculature &ducts extend within the septa

1) Exocrine component- synthesize / secretes enzymes that are essential for digestion in intestine
2) Endocrine component synthesize/secretes hormones (insulin & glucagon) into the blood -> regulate glucose, lipid, & protein metabolism

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27
Q

Pancreatic Histology

  • characteristics
  • cells
  • Hallmarks
A

Serous acinus

  • functional unit of exocrine pancreas and structurally unique
  • contains pancreatic acinar cells

Intercalated duct begins within the acinus

Centroacinar cells: duct cells inside of the acinus

  • continuous with the low cuboidal epithelium of intercalated duct
  • cells secrete HCO3-, Na+, and H2O alkalinizes secretions

Hallmarks: acinar cells stain intensely, centroacinar cells stain lightly, pancreas often confused with parotid

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28
Q

Pancreatic Acinar Cells

  • characteristics (3)
  • hormones (4)
  • effects
A

Characterized by

1) well developed RER
2) prominent Golgi apparatus
3) apical domain of zymogen granules

Granules contain ~20 different pancreatic proenzymes

1) Trypsinogen, chymotrypisinogen : digest proteins
2) Amylolytic enzymes (alpha-amylase) : digest carbohydrates
3) Lipases: digest lipids
4) Deoxyribonuclease, ribonuclease: digest nucleic acid

increase synthesis of proteases with protein rich diet

increase of amylases, decreases in proteases with carbohydrate-rich diet

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29
Q

Pancreatitis

  • describe
  • cause
  • results
A

-Zymogen granules contain inactive proenzymes normally activated in duodenum

  • Premature activation of pancreatic enzymes, results in autodigestion of the pancreatic gland following their release
    • particularly with trypsinogen-> trypsin and inactivation of trypsin inhibitor

Results in

1) acute pancreatitis
2) chronic pancreatitis

30
Q

Acute Pancreatitis

  • cause
  • symptoms
A

usually following trauma, heavy meals, and excessive alcohol ingestion or bilary tract disease

symptoms:
severe abdominal pain, nausea, vomiting

31
Q

Chronic Pancreatitis

A

characterized by fibrosis and partial/total destruction of pancreatic tissue

Cause
- alcoholism

can lead to permanent loss of pancreatic function (endocrine and exocrine)

32
Q

Liver

- cells ( and function)

A
  • enclosed in fibrous CT capsule
  • serous covering surrounds the capsule, except where directly adheres to diaphragm/ other organs
  • hepatocytes function in metabolism, storage, bile production ( exocrine)
  • arranged in cellular cords
33
Q

Functional unit of liver

A

1) hepatic lobule
2) portal lobule
3) liver acinus

34
Q

Blood Supply to Liver

  • transport (2)
  • where they mix
  • pathway for duct
A

1) Portal Vein ( 75-80% afferent blood volume)
- transports blood from GI tract, spleen, and pancreas
2) Hepatic artery
- supplies 2025% of oxygenated blood via the interlobar artery and interlobular arter pathway

Blood from branches of portal vein & hepatic artery mixes in the sinusoid of the lobules

  • converges at the central venules-> sublobular veins
  • blood returns to IVC ( via collecting and hepatic veins)

Right and left hepatic bile duct -> hepatic duct-> common bile duct-> gallbladder

35
Q

Hepatocytes

  • cell characteristics
  • function
A

large polygonal cells with large spherical nuclei

  • most are tetraploid
  • many are binucleate

Functions:

  • secrete bile, mixture of H2O, bile salts and pigments, phospholipds, electrolytes
  • drains into bile canaliculus (canal lined with cholangiocytes, located btw adjacent hepatocytes)
  • canaliculi join to eventually contribute to biliary tree
36
Q

Bile

- function

A

fat absorption

excretion of cholesterol, bilirubin, iron, and copper

37
Q

Bile and Lymph flow relationship

A

bile and lymph flow in the same direction, OPPOSITE of blood

38
Q

Hepatocyte plates

A

separated by anastomosing sinusoids-> perfuse cells with portal and arterial blood

39
Q

Terminal hepatic venule

  • nickname
  • function
A

aka central vein

collects blood from the sinsoids

40
Q

Portal area/ portal canals

-position

A

positioned at angles of the hexagon, loose CT house portal triads

41
Q

Periportal space of Mall

-location

A

located at edges of canals btw stromal CT and hepatocytes

- excess fluid in space of DIssee is collected here and is drained by lymphatic vessels

42
Q

Hepatic Sinusoid

A
  • lined with a thin discontinuous endothelium and discontinuous basal lamina
  • large fenestrae, without diaphragms
  • large gaps between neighboring cells
43
Q

Kupffer Cells

A

specialized macrophages found along endothelial lining of hepatic sinusoid

  • larger than endothelial cells
  • detect and phagocytose effete erythrocytes
  • distinguishes hepatic sinusoids
44
Q

Bile Canaliculi

A

brown staining stick like structures located in between hepatocytes

45
Q

Hepatic Lobule components

A
  1. central venule
  2. hepatocytes
  3. sinusoids
46
Q

Portal Triad components

A
  1. bile ductules
  2. branches of hepatic a.
  3. branches of portal v.
47
Q

Perisinusoidal Space

  • nickname
  • describe
  • location
A

aka Space of Disse

  • site of exchange of materials between blood and liver cells
  • found btw basal surfaces of hepatocytes and those of endothelial cells and Kupffer cells lining the sinusoids
    • microvilli project into this space from the basal surface of the hepatocytes
  • Because of the large gaps in the endothelial layer and the absence of a continuous basal lamina, no significant barrier exists between the blood plasma in the sinusoid and the hepatocyte plasma membrane
  • protein and lipoproteins synthesized by hepatocytes are released into the blood in the perisinusoidal space
48
Q

Portal Lobule

  • how to find it ( 3 steps)
  • signficance
A

Central axis is bile duct (portal triad)

ID portal triad-> draw imaginary lines between 3 central veins-> portal lobule

  • triangular block of tissue
  • outlines bile drainage pathway from adjacent lobules into the same bile duct
  • provide a description comparable to that of other exocrine glands
49
Q

Liver Acinus

A
  • diamond-shaped and occupies part of adjacent classic lobules
  • hepatocytes are arranged in concentric zones around short axis
  • based on O2 gradient along sinusoids of adjacent lobules
  • flow of arterial blood creates gradient of O2/nutrients
  • Cells within each zone have different metabolicc functions and distribution of hepatic enzymes
  • Explains distribution of liver damage resulting from ischemia and/or exposure to toxic substances
50
Q

What pathological changes do you see in Congestive heart failure?

  • zones
  • cell type
A

ischemic necrosis

  • most severe in hepatocytes in zone 3
  • presence of multiple round vacuoles, which indicates extensive lipid accumulation

No noticeable changes are seen in the periphery of the lobule which is zone 1 and much of zone 2

51
Q

Classic Lobule

A

emphasizes endocrine function of hepatocytes as blood flows toward the central vein

52
Q

Portal Lobule

A

emphasizes hepatocytes exocrine function and flow of bile from the classic lobules toward bile duct in portal triad
- area drained by each bile duct is roughly triangular

53
Q

Hepatic Acinus

A

emphasizes different oxygen and nutrient contents of blood at different distances along the sinusoids (blood from each portal area supplies 2+ classic lobules)

  • major activity of each hepatocyte is determined by location along oxygen/nutrient gradient: periportal cells of zone 1
  • increase [oxygen/nutrients] in zone 1 AND 2 AND 3
54
Q

Hereditary Hemachromatosis

A

pathology characterized by increased iron absorption and accumulation in lysosomal hepatocytes
- complications include cirrhosis and cancer of the liver

55
Q

WIlson’s disease

A

hereditary disorder of copper metabolism in which excessive deposits of copper in liver and brain lysosomes produce chronic hepatitis

56
Q

Chronic liver disease

A

perisinusoidal cells remain in quiescent, nonproliferative state, but can proliferate when activated by Kupffer cells and hepatocytes

leads to fibrosis and inflammatory cells (lymphocytes and macrophages) in distorted portal space

57
Q

Long-term consumption of ethanol

A

can result in fatty liver (reversible if EtOf consumption is discontinued)

  • steatohepatitis
  • cirrhosis
58
Q

Steatohepatitis

A

fatty liver accompanied by an inflammatory reaction

59
Q

Cirrhosis

A

collagen proliferation of fibrosis

60
Q

Hepatitis

A

inflammatory condition due to viruses, but can also result from bacteria and parasites

61
Q

Acute hepatitis

A

characterized by loss of appetite, nausea, vomiting, jaundice

62
Q

Chronic hepatitis

A

presence of fibrosis, together with hepatocyte necrosis and inflammatory lymphtocytic activity

63
Q

Viral hepatitis

A

caused by hepatitis virus A, B, C

64
Q

HAV

A

hepatitis virus A

infections caused by spread through ingestion of contaminated food/water
- causes acute hepatitis that rarely becomes chronic

65
Q

HBV

A

Hepatitis Virus B

via sexual contact and blood/serum transfer through shared needles in drug abused

~10% of individuals develop chronic hepatitis

66
Q

HCV

A

Hepatitis Virus C

largely caused by blood transfusion (~90% of the cases)
- 50-70% of the affected individuals develop chronic hepatitis

Therapy
-oral administration of antiviral agents

67
Q

Gallbladder

A

Sac-like structures that stores and concentrate bile

-releases it into duodenum after a meal

68
Q

Gallbladder Histology

- think four layers

A

highly folded mucosa with simple columnar epithelium with microvilli overlying a lamina propria

Muscularis with bundles of muscle fibers oriented in all directions to facilitate emptying of the organ

** external adventitia where it is against the liver

Serosa exposed to peritoneal cavity

69
Q

Rokitansky-Aschoff sinuses

A

deep diverticular of the mucosa that may extend through muscularis externa

  • develop as the result of hyperplasia and herniation of epithelial cell through muscularis externa
  • bacteria may accumulate, causing chronic inflammation
  • increased risk for gallstones
70
Q

Perisinusoidal space of Disse

A

separates hepatocyte plates from blood sinusoidal space

-site of material exchange

GI Final (15 decks)

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