36 - GI System IV Flashcards Preview

Cell Bio Exam 4 > 36 - GI System IV > Flashcards

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

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


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)


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

Sites where blood vessels and nerves penetrate


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


What portion of the intestines do we commonly see polyps?

Large intestine


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

Colonoscopy procedure via a colonoscope


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

Usually removed


Why do polyps develop in the first place?

Due to the hyperproliferation of cells


What are the two types of polyps we see?

- Tubular adenoma
- Villous adenoma

Note that sometimes we see a mix between the two types


Which type of polyp is more invasive?

Villous adenoma


Is the size of the polyp clinically relevant?

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


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


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

This is a compensatory response to the inflammatory edema that exists


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


What are the two major forms of inflammatory bowel disease?

- Ulcerative Colitis
- Crohn's Disease


Where is ulcerative colitis typically found?

Confined to the large intestine


Where is Crohn's disease typically found?

Anywhere along the GI tract


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


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


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)


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


What areas of the colon are involved?

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


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


What is the capsule that surrounds the liver called?

Glisson's capsule


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


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

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


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

You will see the reticular fibers penetrate into the liver parenchyma


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

Scar tissue formation that can cause problems


What is the classic hepatic lobule?

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


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

Portal canals - each corner has 3-6 portal canals


What do portal canals contain?

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


What is found in the "portal triad"?

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


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


What do the lymph vessels in the periportal space do?

Collect lymph and shunt it back into venous circulation


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


Note that the portal canal is sometimes called the portal space

Just note it


Is the classic liver lobule well supplied with blood?

Yes, very well supplied


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

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


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


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


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

Portal vein - nutrients
Hepatic artery - oxygen


What are Kupffer cells?

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


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


What are sinusoids of the liver?

Discontinuous endothelium with large fenestrations and discontinuous basal lamina


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


What is the perisinusoidal space?

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


What would you find in the perisinusoidal space?

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


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

Hepatic stellate cells (AKA perisinusoidal cells)


What is the signature feature of hepatic stellate cells?

Large lipid droplets


What is stored in the hepatic stellate cells? Why?

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


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


What are the three zones of the hepatic acinus?

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


Describe Zone 1

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


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)


Where would acetominophen toxicity cause necrosis first?

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


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

Fat accumulation
Necrosis of the tissue


Describe a hepatocyte

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


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

1 - Detoxification
2 - Glycogen metabolism


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

1 - Protein synthesis
2 - Carbohydrate storage


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

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


What is the effect of less albumin during injury?



What is the effect of less clotting factors during injury

It takes longer for the blood to clot


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

Liver - this is another key function


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


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

Liver - this is another key function


What type of bilirubin is unconjugated?



What type of bilirubin is conjugated?



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


What is the MDR-2 protein?

A protein found on membrane cells lining the bile collecting system


What is the function of an MDR-2 protein?

Transport conjugated bilirubin into the bile


What is Dubin Johnson Syndrome?

A defect in the MDR-2 protein


What is the clinical presentation of Dubin Johnson Syndrome?

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


What is Gilbert syndrome?

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


What is the clinical presentation of Gilbert syndrome?

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


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


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

Type I = fatal
Type II = can be benign


How fast will the liver begin to regenerate?

Quickly - significant regeneration can be seen in 1 week


What will you see in Alcoholic Liver disease?

- Fatty liver
- Increased collagen deposition
- Damage is REVERSIBLE


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


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

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


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

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


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


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

Bile canaliculus


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

Canal of Hering


What lines the canal of Hering?

- Stem cells
- Cholangiocytes and hepatocytes
- Ductal cells


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)


What layers do we find in a gall bladder?

- Mucosa
- Muscularis
- CT layer of serosa/adventitia


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

1 - Epithelium
2- Basal lamina
3 - Lamina propria


What is cholesterolosis?

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


Do foam cells in the gallbladder cause harm?

No, this is a fairly benign, reversible condition


How do exocrine cells of the pancreas generally function?

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


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

Secrete enzymes


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

Secrete water and ions (HCO3-)


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

- Acute pancreatitis


What will you find in acute pancreatitis?

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