36 - GI System IV Flashcards Preview

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Flashcards in 36 - GI System IV Deck (95):
1

What is colonic diverticula?

A "pouching out" of mucosa and submucosa that is found in the large intestine at a site of weakness between tinea coli

2

Why would we only see colonic diverticula in the large intestine and not in the rectum?

Because the rectum has a complete and continuous muscularis externae (no sites of weakness)

3

What areas of the large intestine are even more susceptible to colonic diverticula?

Sites where blood vessels and nerves penetrate

4

Is a colonic diverticula a true diverticula or a false diverticula? Why?

A false diverticula because a true diverticula would include all layers of the wall whereas a colonic diverticula only involves the mucosa and submucosa

5

What portion of the intestines do we commonly see polyps?

Large intestine

6

What procedure allows us to see polyps of the GI tract?

Colonoscopy procedure via a colonoscope

7

Are polyps usually removed when they are found or are they usually left?

Usually removed

8

Why do polyps develop in the first place?

Due to the hyperproliferation of cells

9

What are the two types of polyps we see?

- Tubular adenoma
- Villous adenoma

Note that sometimes we see a mix between the two types

10

Which type of polyp is more invasive?

Villous adenoma

11

Is the size of the polyp clinically relevant?

Yes - the larger the polyp, the more likely it is to be invasive

12

Which statement regarding lymphatic vessels in the lamina propria of the large intestine is true?

a. Is well endowed with lymphatic vessels
b. Is poorly developed
c. Is better developed in the presence of inflammatory bowel disease

a. Is well endowed with lymphatic vessels = FALSE
b. Is poorly developed = TRUE
c. Is better developed in the presence of inflammatory bowel disease = TRUE

13

Why is there an increased density of lymphatic vessels in inflammatory bowel disease?

This is a compensatory response to the inflammatory edema that exists

14

What are some tissue modifications that you will see in inflammatory bowel disease?

- The architecture of the wall will be modified
- Lamina propria will be full of dark blue inflammatory cells
- The lamina propria will contain an increase density of lymphatic vessels

15

What are the two major forms of inflammatory bowel disease?

- Ulcerative Colitis
- Crohn's Disease

16

Where is ulcerative colitis typically found?

Confined to the large intestine

17

Where is Crohn's disease typically found?

Anywhere along the GI tract

18

Which form of inflammatory bowel disease is more likely to form fissures and fistulas that invade neighboring organs?

Crohn's disease - because it is found anywhere along the GI tract

19

What is the difference between a fissure and a fistula?

A fissure will open into the peritoneal cavity and leak the intestinal contents into this space

A fistula will open into a neighboring organ and leak the intestinal contents into this organ

20

What is Hirschsprung's disease?

AKA congenital megacolon
- A condition caused by neural crest cells failing to properly migrate into the affected segment of the colon
- The result is that there will be a lack of both plexuses in that segment of the colon (myenteric and submucosal plexuses)

21

What does the lack of plexuses in Hirschprung's disease lead to?

The area lacking the plexuses will remain constricted, which causes the proximal area to dilate (megacolon) in order to compensate for the damming effect

22

What areas of the colon are involved?

The rectum is ALWAYS involved and the more proximal segments may also be involved

23

Case study: patient has difficult/painful swallowing for 3 years and a long history of irritable bowel syndrome - a CT scan shows a large thickening of the esophagus explaining the swallowing problems... What is this from?

A fissure that extends into the submucosa of the esophagus - the fissure as well as the endoscopy and biopsy are indicative of Crohn's disease

24

What is the capsule that surrounds the liver called?

Glisson's capsule

25

What is Glisson's capsule composed of?

- Outermost layer is visceral peritoneum (mesothelium of simple squamous epithelium)
- Fibrous connective tissue
- Type III collagen reticular fibers

26

Is Glisson's capsule innervated? How would we know?

Yes, richly innervated - we know this because distension of the liver causes pain

27

What pattern will you see of the reticular fibers of Glisson's capsule?

You will see the reticular fibers penetrate into the liver parenchyma

28

What does an excessive amount of connective tissue in the liver indicative of?

Scar tissue formation that can cause problems

29

What is the classic hepatic lobule?

The pattern of liver cell architecture that is seen histologically - Hexagonal plates of hepatocytes and sinusoids

30

What structures are found at the corners of the hexagonal lobules?

Portal canals - each corner has 3-6 portal canals

31

What do portal canals contain?

- Connective tissue
- The portal triad
- Lymphatic vessels
- Autonomic nerve fibers

32

What is found in the "portal triad"?

1 - Hepatic artery
2 - Portal vein
3 - Bile duct

33

What is the periportal space?

AKA space of Mall
- the area between the hepatic lobule and the portal triad
- believed to have originated from lymphatics

34

What do the lymph vessels in the periportal space do?

Collect lymph and shunt it back into venous circulation

35

Can you see a clear delineation between each liver lobule in humans?

No - it isn't as well defined in humans, but you can see some borders and the portal canals at the corners

36

Note that the portal canal is sometimes called the portal space

Just note it

37

Is the classic liver lobule well supplied with blood?

Yes, very well supplied

38

There is "dual blood supply" to the liver. What are the two sources?

Portal vein (75%)
Hepatic artery proper (25%)

39

Describe the blood flow from the portal vein

- Blood enters the lobule via the inlet venule
- The inlet venule dumps the blood into the hepatic sinusoidal capillaries between hepatocytes
- The liver is supplied with rich nutrients from the GI tube

40

Describe the blood flow from the hepatic artery proper

- Blood enters the lobule via the arteriosinusoidal branch
- The arteriosinusoidal branch dumps into the hepatic sinusoidal capillaires between the hepatocytes
- This blood supply is rich in oxygen

41

What is the portal vein blood rich in? What is the hepatic artery proper blood rich in?

Portal vein - nutrients
Hepatic artery - oxygen

42

What are Kupffer cells?

Phagocytic cells of the liver that remove pathogens and worn-out RBCs from the blood

43

What is normally the main site of blood filtering pathogens and worn-out RBCs?

The spleen
- The liver can take over if the spleen is removed

44

What are sinusoids of the liver?

Discontinuous endothelium with large fenestrations and discontinuous basal lamina

45

Why is the basal lamina absent in the sinusoids of the liver?

The basal lamina would be a barrier to rapid exchange of materials from the blood to the tissue of the liver

46

What is the perisinusoidal space?

AKA Space of Disse
- The space between epithelial cells and hepatocyte cytoplasm

47

What would you find in the perisinusoidal space?

Numerous hepatocyte microvilli which function to increase the surface area for rapid exchange

48

What else would you find in the perisinusoidal space (cells types)?

Hepatic stellate cells (AKA perisinusoidal cells)

49

What is the signature feature of hepatic stellate cells?

Large lipid droplets

50

What is stored in the hepatic stellate cells? Why?

Vitamin A - we don't know why (function unknown)

51

What is the hepatic acinus?

A diamond shaped area that extends from a central vein to a hepatic canal then back to the original central vein

The diamond shaped area is divided into zones that represent the areas that receive blood supply first

52

What are the three zones of the hepatic acinus?

Zone 1 (closest to blood supply)
Zone 2
Zone 3 (furthest from blood supply)

53

Describe Zone 1

AKA perilobular region
- More oxygen
- More extrahepatic hormones
- More enzymes for glucose-liberation
- More enzymes for fatty-acid lxidation

54

Describe Zone 3

AKA centrolobular region
- Closest to central vein
- More enzymes for glycolysis
- More enzymes for fatty-acid synthesis
- More waste products
- Most susceptible to damage (during detoxification)

55

Where would acetominophen toxicity cause necrosis first?

Zone 3
- More waste products
- Less access to filtering blood supply, detoxification

56

What will you see in ischemic-induced necrosis of Zone 3?

Fat accumulation
Necrosis of the tissue

57

Describe a hepatocyte

- Involved in numerous functions
- Large variety of organelles
- rER for protein synthesis
- sER for detox
- Mitochondria for fuel

58

What are two main functions of the liver that require a well developed sER?

1 - Detoxification
2 - Glycogen metabolism

59

What are two main functions of the liver that require a well developed rER?

1 - Protein synthesis
2 - Carbohydrate storage

60

What happens to colloid osmotic pressure and blood clotting with severe injury?

Albumin and clotting factors (fibrinogen and prothrombin) are made by the liver

61

What is the effect of less albumin during injury?

Edema

62

What is the effect of less clotting factors during injury

It takes longer for the blood to clot

63

What organ is responsible for the synthesis and secretion of bile acids?

Liver - this is another key function

64

How is bile produced and/or processed

Most of the bile is actually reabsorbed from the intestine and reused, but some is freshly synthesized in the sER

65

What organ is responsible for the conjugation and secretion of bilirubin?

Liver - this is another key function

66

What type of bilirubin is unconjugated?

indirect

67

What type of bilirubin is conjugated?

direct

68

What is the difference between unconjugated and conjugated bilirubin?

Unconjugated (indirect) bilirubin is insoluble
- Released from lysed RBCs
- Before it is processed by liver

Conjugated (direct) bilirubin is soluble
- After it has been processed by liver
- The liver makes it soluble

69

What is the MDR-2 protein?

A protein found on membrane cells lining the bile collecting system

70

What is the function of an MDR-2 protein?

Transport conjugated bilirubin into the bile

71

What is Dubin Johnson Syndrome?

A defect in the MDR-2 protein

72

What is the clinical presentation of Dubin Johnson Syndrome?

- Elevated levels of conjugated (direct) bilirubin
- Fairly benign condition

73

What is Gilbert syndrome?

A defect in the enzyme involved in conjugation of bilirubin within the liver (UGT1A1)

74

What is the clinical presentation of Gilbert syndrome?

- Decreased levels of conjugated (direct) bilirubin
- Fairly benign condition

75

What is Crigler-Najjar syndrome/Neonatal Hyper-bilirubinemia?

There are two types
- Type I: the conjugation of bilirubin is completely absent
- Type II: the conjugation of bilirubin is decreased

76

What are the clinical presentations of Crigler-Najjar syndrome/Neonatal Hyper-bilirubinemia Type I and II?

Type I = fatal
Type II = can be benign

77

How fast will the liver begin to regenerate?

Quickly - significant regeneration can be seen in 1 week

78

What will you see in Alcoholic Liver disease?

- Fatty liver
- Increased collagen deposition
- Damage is REVERSIBLE

79

What will you see in Alcoholic Cirrhosis of the liver?

- Continued abuse leads to cirrhosis
- Cirrhosis is IRREVERSIBLE
- Liver nodules will be seen
- Liver becomes highly dysfunctional

80

Why do liver nodules form in alcoholic cirrhosis of the liver?

Nodules
- Collections of hepatocytes
- Liver is trying to regenerate
- Connective tissue has proliferated and confines the dividing hepatocytes to nodules

81

What are stellate cells? How do they change during cirrhosis?

Normal stellate cells are quiescent (dormant) but injury/assult activates stellate cells

82

What do activated stellate cells do during cirrhosis?

- stellate cells proliferate and begin producing CT components
- the CT components become contractile and constrict blood flow
- active stellate cells are damaging to the liver

83

What do we call the beginning portion of the bile collecting system?

Bile canaliculus

84

Bile flows through a system of channels. What are they called?

Canal of Hering

85

What lines the canal of Hering?

- Stem cells
- Cholangiocytes and hepatocytes
- Ductal cells

86

What two types of cells can regenerate liver cells?

- Stem cells (activation can stimulate liver cell recovery)
- Periductular null cells (sit in the periportal space)

87

What layers do we find in a gall bladder?

- Mucosa
- Muscularis
- CT layer of serosa/adventitia

88

What three components of the mucosa will we find in the gall bladder?

1 - Epithelium
2- Basal lamina
3 - Lamina propria

89

What is cholesterolosis?

Elevated cholesterol levels that lead to the formation of foam cells in the gallbladder

90

Do foam cells in the gallbladder cause harm?

No, this is a fairly benign, reversible condition

91

How do exocrine cells of the pancreas generally function?

First they synthesize enzymes, then they store them until they receive a signal

92

What is the role of acinar cells of the exocrine pancreas?

Secrete enzymes

93

What is the role of ductal cells of the exocrine pancreas?

Secrete water and ions (HCO3-)

94

Case study: abdominal pain in epigastric region, radiation to back, nausea, vomiting, recent history of binge drinking, fever, tachycardia

Lab findings
- Elevated serum amylase
- Elevated lipase

Diagnosis
- Acute pancreatitis

95

What will you find in acute pancreatitis?

- Enlargement of pancreas
- Shaggy margins of pancreas
- Fat infiltration of peripancreatic area
- Peripancreatic fluid