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Section 5A, 5B and 5C Abdominal Anatomy and Digestive System > Small Intestine > Flashcards

Small Intestine Flashcards

1
Q

What are the 3 components of the small intestine?

A

Duodenum (proximal)
Jujenum (middle)
Ileum (distal)

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2
Q

What are the 4 functions of the small intestine?

A
  1. mechanical breakdown and propulsion (via segmentation and peristalsis)
  2. mechanical and chemical digestion
  3. absorption of nutrients
  4. transportation of undigested material to large intestine
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3
Q

Which organs does the small intestine receive digestive enzymes and bile from, and via which pathways?

A

Digestive enzymes from pancreas (via main pancreatic duct, hepatopancreatic ampulla and sphincter, and major duodenal papilla)

Bile from liver (via left and right hepatic ducts, common hepatic duct, bile duct, hepatopancreatic ampulla and sphincter, and major duodenal papilla)

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4
Q

Describe the pathways of the ducts entering the small intestine from the liver and pancreas

A

Pancreas:

  • major pancreatic duct
  • unites with bile duct to form hepatopancreatic ampulla
  • through hepatopancreatic sphincter
  • through major duodenal papilla into D2

From Liver:

  • via right and left hepatic duct
  • unite to form common hepatic duct
  • unite with cystic duct (from gallblader) to form bile duct
  • unites with pancreatic duct to form hepatopancreatic ampulla
  • through hepatopancreatic sphincter
  • through major duodenal papilla into D2
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5
Q

Whereabouts in the small intestine do secretions from the pancreas and liver enter, and how?

A

D2 segment of the duodenum

  • major duodenal papilla
  • secretions enter via hepatopancreatic sphincter, from hepatopancreatic duct, from bile duct (liver) and major pancreatic duct (pancreas)
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6
Q

In which component of the small intestine do the most digestive processes take place?

A

The duodenum

- pancreatic enzymes (via pancreatic duct) begin chemical digestion of chyme

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7
Q

What is the function of bile in the small intestine?

A
  • emulsifies fats

- enhances digestion

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8
Q

What marks the borders of the small intestine?

A

The pyloric sphincter marks the border between the stomach and the duodenum

The ileocaecal junction marks the border between the ileum and the caecum of the large intestine

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9
Q

What are the 4 components of the duodenum, their major features, and their anatomical position?

A

D1:

  • 5cm
  • superior
  • direct continuation of pylorus
  • cap (first 2cm) is the only mobile and intraperitoneal component of the duodenum

D2:

  • descending
  • 10cm
  • between superior and inferior duodenal flexures
  • major duodenal papilla (where hepatopancreatic ampulla/duct enters)
  • sphincter of Oddi / hepatopancreatic sphincter: muscular valve at major duodenal papilla controlling entry of pancreatic and liver secretions into D2
  • minor duodenal papilla (where accessory pancreatic duct enters in embryos and some adults)

D3:

  • 8cm
  • horizontal
  • level of L3

D4:

  • 5cm
  • ascending
  • runs along left side ofo aorta
  • angles sharply at L2 (duodenojujenal flexure between duodenum and jujenum)

D1-3: right upper quadrant
D4: left upper quadrant

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10
Q

which components of the small intestine are intraperitoneal, and which are extraperitoneal?

A

Intraperitoneal:

  • D1 duodenal cap (first 2cm)
  • jujenum and ileum

Extraperitoneal:
- D2-4

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11
Q

What are the arteries that supply the small intestine?

A

Duodenum:

  • gastroduodenal (from common hepatic, from celiac trunk)
  • superior pancreaticduodenal (from common hepatic, from celiac trunk)
  • inferior pancreaticoduodenal (from superior mesenteric)

Ileum and Jujenum:

  • 15-18 intestinal arteries (branch from superior mesenteric)
  • ileocolic supplies terminal ileum and ileocolic canal (from superior mesenteric)
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12
Q

What are the two major arteries that provide branches that supply the small intestine?

A

Common Hepatic (from celiac trunk)

  • gastroduodenal
  • superior pancreataicduodenal

Superior Mesenteric

  • inferioro pancreaticoduodenal
  • intestinal arteries
  • ileocolic
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13
Q

Which lymphatic nodes does the small intestine drain into?

A

Pancreaticoduodenal

Superior mesenteric

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14
Q

What is the innervation of the small intestine?

A

PNS: CNX Vagus via dorsal motor nucleus of vagus in the medulla

SNS: Greater and lesser splanchnic nerves (T5-9) via celiac and superior mesenteric plexi

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15
Q

What is the venous drainage of the small intestine?

A

Duodenum:
- duodenal v (drain into portal)

Ileum and Jujenum:
- SMV (unites with splenic v to form portal v)

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16
Q

What are 3 histological features of the small intestine designed to aid nutrient absorption?

A
  1. Circular folds
    - mucosa and submucosa are arranged in circular folds
    - slows down movement of chyme through lumen
    - increases surface area
  2. Villi
    - fingerlike projections of mucosa
    - in the core of each villus: dense capillary bed and a lymphatic capillary
  3. Microvilli
    - on the villi
    - cytoplasmic extensions of mucosal absorptive cells
    - brush border cells perform digestion of food
17
Q

What is located inside each villi?

A

Vascular and lymphatic vessels projecting from submucosal layer:

  • dense capillary bed
  • lymphatic capillary
    (allows for absorption of nutrients from small intestine into bloodstream)
18
Q

What are the layers of the small intestine wall?

A

Mucosa (deep)

  • in circular folds
  • with villi projections

Muscularis mucosae
- gentle contractions create vibrations in small intestinal wall

Submucosa

  • contribute to circular folds
  • connective tissue
  • contains blood vessels and nerves

Muscularis
- inner circular layer
- outer longitudinal layer
(contractions create peristalsis)

Serosa

  • membranous connective tissue
  • intraperitoneal (except D2-4)
19
Q

What is the function of the circular folds?

A
  • increase surface area for absorption
  • slow down movement of chyme to allow more time for absorption
  • make chyme spiral through lumen to mix with intestinal juice
20
Q

What are microvilli?

A

Absorptive cells embedded on villi

  • absorb nutrients from small intestine
  • sometimes called brush border
21
Q

What are the 5 cell types in a villi?

A
  1. Enterocytes:
    - absorptive cells endowed with microvilli
    - crypt enterocytes secrete intestinal juice
  2. Enteroendocrine cells
    - secrete hormones (CCK, secretin)
  3. Goblet cells
    - produce alkaline mucous
    - relies on prostaglandin
  4. Paneth cells
    - release antimicrobial agents
  5. Stem cells
    - renew the epithelium every 3-5 days
22
Q

What is the importance of prostaglandin in the small intestine?

A

Necessary for the goblet cells in the villi to produce alkaline mucous

  • prostaglandin inhibition (ie: from NSAID use) can inhibit the production of alkaline mucous from the goblet cells of the villi and cause damage to the mucosal layer
23
Q

Which cells produce mucous in the small intestine?

A

Goblet cells (on villi) - rely on prostaglandin for mucous production

24
Q

What are enterocytes?

A

Absorptive cells on villi

  • endowed with microvilli
  • crypt enterocytes secret intestinal juice
25
Q

Which cells secrete intestinal juice?

A

Crypt enterocytes

26
Q

What do paneth cells release?

A

Antimicrobial agents (role in immune function, c apble of phagocytosis)

27
Q

How often are the epithelial cells of the mucosa in the small intestine renewed?

A

3-5 days (epithelial cells produced by stem cells in villi)

28
Q

Which hormones are released by the enterocytes?

A

CCK (cholecystokinin)

Secretin

Section 5A, 5B and 5C Abdominal Anatomy and Digestive System (10 decks)

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