- Fold of peritoneum attached to stomach, fatty layer containing lymphatics, blood vessels, nerves - Localises on groin on the right hand side Infections contained within the omentum

Small intestine Flashcards by Michaela Netto

What is the small intestine also called?

The small bowel

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What are the 3 parts of the small intestine?

Dueodenum
Jejenum
Ileum

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What is the function of the small intestine?

The small intestine is the primary site for digestion and absorption

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The small intestine is partially retro-peritoneal. What does this mean?

Part of it is (duodenum) behind the peritoneum

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How long is the small intestine?

6.5m

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How long is the large intestine?

1.5m

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The small intestine is longer than the large intestine. Why is it termed the small intestine?

The diameter of the small intestine is smaller than that of the large intestine

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What are the 2 parts of the peritoneum?

Visceral (around the organs) and parietal (outer aspect)

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What is the peritoneum?

Serous membrane that lines the abdominal cavity

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What is the mesothelium?

Cells of the peritoneum (serous membrane), produces a watery fluid

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Describe the endothelium lining the peritoneum

Mesothelium: simple squamous layer of cells

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What are double folds of the peritoneum termed?

Mesentery

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What is the omentum?

Fold of peritoneum attached to stomach, fatty layer containing lymphatics, blood vessels, nerves
Localises on groin on the right hand side
Infections contained within the omentum

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Where does chyme pass from?

From the stomach to the duodenum of the small intestine

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Describe features of the duodenum

Short length
Contains Brunner’s glands: alkaline secretion
Receives common bile duct (sphincter of Oddi) - bile and pancreatic juice enter here
Ends at the duodenojejunal junction

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What is the purpose of Brunner’s glands in the duodenum?

Produce alkaline secretions for protection (gastric fluid is very acidic, pH 1-2)

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What is bile for?

Fat digestion

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What do pancreatic juices do?

Protein digestion

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What is pancreatitis?

Inflammation of the pancreas

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Which vertebrae does the duodenum lie between?

L1-L4

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What shape is the duodenum?

C shaped

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What is the spinchter of Oddi?

Surrounds the major duodenal papilla

Bile and pancreatic juices enter the duodenum at the major duodenal papilla

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What percentage of people also have a minor duodenal papilla in addition to a major duodenal papilla?

20%

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Which hormone controls bile secretions from the gallbladder?

Cholecystokinin (CCK)

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Which cells secrete CCK?

Cells lining the duodenum

What do cells lining the duodenum secrete CCK in response to?

High fat content in the diet

What is the advice for patients who have had their gallbladder removed?

Eat less fat in the diet

What are the 4 parts of the duodenum?

Superior, descending, inferior, ascending

What does the superior mesenteric artery supply?

The midgut Structures like the small intestine, the large intestine Comes straight from the abdominal aorta - largest artery in the body

What is the largest artery in the body?

Abdominal aorta

What is the first major branch of the abdominal aorta?

Coeliac trunk/coeliac artery

Which structures does the superior pancreaticoduodenal artery supply?

The pancreas and the duodenum

How many blood supplies does the duodenum have?

2 | C shaped: 1 at top, 1 at bottom

What does the inferior pancreaticoduodenal artery supply?

Pancreas and duodenum

What are the 2 blood supplies for the duodenum?

1. Superior pancreaticoduodenal artery (from the coeliac trunk of the abdominal aorta) 2. Inferior pancreaticoduodenal artery (from the superior mesenteric artery)

What is a duodenal ulcer and where does it arise?

- Most develop in the posterior wall of the superior part of the duodenum (where the stomach acid comes in) - Ulcer is a breakdown of epithelium Possibility of perforation - Can cause peritonitis - life-threatening

What is peritonitis?

Inflammation of the peritoneum

What might a duodenal ulcer indicate?

Cancer

What does air in the abdominal cavity indicate (on an X-ray)?

Something has burst | There should not be air in the abdominal cavity

Which part of the small intestine is retro-peritoneal?

Duodenum

Which part(s) of the small intestine are within the peritoneum?

Jejenum and ileum

What is the function of the duodenum?

Mainly digestion | Pancreatic enzymes and bile

What is the function of the jejenum?

Digestion (brush border enzymes) | Absorption

What is the function of the ileum?

Mainly absorption

Describe the structure/layers of the jejenum and ileum

Lumen, mucosa, submucosa, muscularis externa, adventitia

What are the layers of the mucosa?

Epithelium, lamina propria, muscularis mucosae

What are the layers of the muscularis externa?

``` Innermost oblique (stomach ONLY) Inner circular Outer longitudinal ```

Which nerves supply the small intestine?

Submucosa plexus (meissner plexus) and the myenteric plexus (auerbach plexus)

Where is the submucosa plexus located?

In the submucosa

Where is the myenteric plexus located?

Between the inner and outer layers of the muscularis externa

What can happen is nerves don't develop properly in the small intestine?

Can't contract, can't digest properly, can't absorb properly

What are plicae circulares?

Transverse folds | Big folds of the mucosa that can be seen with the naked eye

What is the function of plicae circulares?

Increase the surface area of the jejenum and ileum by 1.6-2x Almost doubles the surface area of the small intestine

What do microvilli do?

Small projections that increase the surface area by up to 200x for absorption Found in the duodenum, jejenum and ileum

What are vasarecta and where are they found?

Straight blood vessels found at the top of the small intesitne

Why are the blood vessels more complex/more bendy at the bottom of the small intestine compared to the top?

More absorption going on, increases absorption

Infections in the bowel can destroy microvilli. What effect will this have on small bowel function?

Reduced absorption

What are Peyer's patches?

Collections of inflammatory tissue | More in the ileum compared to duodenum and jejenum

What are enterocytes?

Cells of the intestinal lining

What do enterocytes do in the small intestine?

- Digestion (brush border enzymes on microvilli) | - Absorption (carrier proteins)

What can malabsorption syndromes cause?

Deficiencies that affect blood e.g. anaemia

What is Meckel's diverticulum?

An outpouching in the small intestine | Rule of 2's: 2% of the population affected, get them at 2 years old, 2 feet away from ileocaecal valve, 2 inches long

What type of mucosa does Meckel's diverticulum affect?

Mostly ileal mucosa

What type of mucosa may be present in the outpouching in Meckel's diverticulum?

Acid producing gastric, pancreatic or colonic type mucosa