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Anatomy 2FF3 > Stomach > Flashcards

Stomach Flashcards

1
Q

Layers of the stomach (x4)

A

Mucosa: epithelium, 2 layers

  • Lamina propria: glues mucosa down to muscularis mucosa
  • Muscularis mucosa: puts the mucosa into folds

Submucosa: glues mucosa to muscularis level
- Where BVs, nerves + lymphatics come in

Muscularis: two layers = peristalsis

  • Inner circular
  • Outer longitudinal

Serosa/adventitia: secretes serosal fluid
- Glues epithelium to muscularis

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2
Q

Enteric nervous system + components

A
  • Coordinates peristalsis

2 components

  • Myenteric plexus: muscular contractions, mechanical digestion (between circular + longitudinal muscles)
  • Submucosal plexus: regulates secretions (in submucosa)
  • Interstitial cells of Cajal: pacemakers of the gut
    • Sets a rhythm for contractions to occur, ANS has an effect on how fast/slow
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3
Q

ANS and ENS connection

A
  • Para + sym can both regulate myenteric plexus (signals for contractions) and submucosal plexus (release enzymes)
  • Parasympathetic = increased
  • Sympathetic = decreased (constricts BVs that go to the gut)
  • Parasympathetic NS can also go directly to the end muscles for fine tuning (ganglia sit in organs)
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4
Q

Where are sympathetic GI tact ganglia located?

A

In collateral ganglia (sits on the arteries)

- Celiac, superior/inferior mesenteric ganglia

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5
Q

Parasympathetic ganglia

A
  • Located in organ walls

- Sigmoid colon + rectum are controlled by pelvic splanchnic nerves (sacral parasympathetic output)

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6
Q

The peritoneum

A
  • Parietal peritoneum: lines the abdominal pelvic cavity
  • Mesentery: fold of peritoneum, suspends SI from dorsal abdominal wall
    • This is how nerves/BVs get in and out of the small intestine
  • Visceral peritoneum: serosa of SI
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7
Q

Folds of the peritoneum

A

Falciform ligament: divides liver in half
- Only one that originates form ant. abdominal wall

Lesser omentum: connects lesser surface of stomach to inferior surface of liver

Greater omentum: yellow (full of fat cells), goes across SI

  • Hangs off greater curvature of stomach + attaches to large intestine
  • Lots of BVs & lymphatic tissue here (creates antibodies & the fat cells are a good place to store excess energy)

Mesentery: suspends the small intestine

Mesocolon: part of mesentery that attaches colon to abdominal wall

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8
Q

Alterations of layers in the stomach

A
  1. Rugae: specialized foldings of the mucosa, allows stomach to expand
  2. Innermost oblique muscle layer: additional layer of the muscularis, helps in mechanical digestion
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9
Q

Regions of the stomach

A
  1. Cardia region: closest to heart & LES
  2. Fundus: holding area for semi-solid food
  3. Body: where the 3 layers of muscularis are well-developed, intense rugae (flattens to expand stomach)
  4. Pyloric region: 3 regions
    • Pylorus: where pyloric sphincter is, controls chyme –> SI
    • Pyloric canal: leads to sphincter
    • Pyloric antrum: opening to pyloric canal
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10
Q

Why is intrinsic factor important?

A
  • Stomach produces intrinsic factor
  • Intrinsic factor binds to Vit B12 (this is absorbed later on)
  • Vit B12 is necessary for DNA synthesis
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11
Q

Stomach blood supply

A

Celiac trunk: supplies most of the blood to the stomach
- R/L gastric a. come off of celiac trunk to form an anastomosis, ensures BF to stomach

R/L gastro-mental a. also come off of celiac trunk to form an anastomosis
- Services greater curvature + greater omentum

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12
Q

Stomach venous drainage

A

**All veins eventually drain into the hepatic portal vein

  • L/R gastric drains lesser curvature
  • L/R gastro-mental dump into superior mesenteric v. (drains most of SI and some of LI)
  • Splenic v. drains left gastromental + short gastric
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13
Q

What is a gastric pit?

A
  • Invaginations of the stomach mucosa
    • Where mucus is produced
    • Deeper in the pit is where HCl is produced & enzymes (pepsin + gastric lipase)
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14
Q

Mucous cells

A

Produce mucus (mucin + water + bicarb anion), how stomach protects itself from HCl

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15
Q

Parietal cells

A

Secretes HCl & intrinsic factor (to absorb Vit B12)

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16
Q

Chief cells

A

Secrete pepsinogen & gastric lipase (enzymes of gastric juice)

17
Q

G cells

A

Secretes gastrin (endocrine hormone, released locally & gets into BS to act on distal cells)

18
Q

What happens when G cells get activated?

A
  • Increased parietal cell activity (more HCl)
  • Increased chief cell activity (more digestive enzymes)
  • Tightening of LES (so HCl doesn’t enter esophagus)
  • Increase of motility (more churning from 3 muscle layers)
  • Relaxation of pyloric sphincter (so chyme can exit)
19
Q

How is HCl made?

A
  • Transport protein used for H+ (facilitated)
    • ATPase H+ pump is used to pump H+ into the gut lumen (switches with K+)
  • Bicarb anion goes through an anti porter (secondary active transport)
    • Allows it to move and Cl- is brought in
    • Bicarb enters BS and pH of blood goes up
  • Cl- leaves into gut lumen via ion channel
20
Q

What increases the production of HCl?

A
  • Gastrin: from G cells
  • ACh: from parasympathetic nerve fibers
  • Histamine: from mast cells (lamina propria)
    • Released onto parietal cells to get them to keep making HCl
21
Q

Hyper secretion of HCl

A
  • Increased HCl production but same amount of mucus

- Erosion of mucosa

22
Q

3 phases of digestion

A
  1. Cephalic phase
  2. Gastric phase
  3. Intestinal phase
23
Q

Cephalic phase

A
  • Preparation for food (parasympathetic output)
  • Talks to submucosal plexus (increased enzymes), G cells (more gastrin) & myenteric plexus (more contractions)
    • Gastrin is also able to ramp up both plexi by talking directly to the epithelium
24
Q

Gastric phase

A
  • Caused by distention of stomach from food (stretch receptors)
  • Chemoreceptors detect increased pH cause by the food
    • Activates neural parasympathetic impulses
    • Local reflex to the plexi and G cells
25
Q

Intestinal phase

A
  • Stretch receptors sense distention of the duodenum
  • Chemoreceptors sense the presence of partially digested food (fatty acids + glucose)
  • Signals back to stomach (via neural + hormonal responses) to tell the stomach to slow down
    • Secretin released by endocrine cells (from duodenum): tells submucosal plexus to make less enzymes and less HCl acid
    • CCK is released & acts on myenteric plexus to lower contractions
  • Enterogastric reflex: less para and more sym (reduces stomach’s chemical digestion)
    • Long acting neural reflex involving the brainstem

Anatomy 2FF3 (26 decks)

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