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Metabolics > The GI Tract > Flashcards

The GI Tract Flashcards

1
Q

Criteria for a healthy gut

A
  • effective digestion and absorption of food
  • absence of GI illness
  • normal and stable intestinal microbiota
  • effective immune system
  • status of well-being
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2
Q

Digestive tract

A
  • oral cavity
  • esophagus
  • stomach
  • small intestine
  • large intestine
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3
Q

Accessory organs

A
  • pancreas
  • liver
  • gallbladder
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4
Q

Saliva

A

water (99%), electrolytes, mucus, enzymes, antibacterial and antiviral compounds

  • enzymes
  • mucins
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5
Q

Enzymes of the oral cavity secretions

A
  • Salivary amylase (hydrolyzes a 1-4 bonds in starch)
  • Lingual lipase (hydrolyzes dietary triglycerides)
  • Lysozyme (antibacterial enzyme)
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6
Q

Mucins

A

glycoproteins that lubricate food and protect the oral mucosa

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7
Q

Brushing teeth

A
  • oral bacteria
  • dental carries, periodontal diseases, oral cancer
  • diabetes
  • Cardiovascular disease -oral microbiota in atherosclerotic plaques/ bacteria linked to cholesterol levels
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8
Q

Stomach functions

A
  • produces acid, enzymes and intrinsic factor and hormones
  • regulates hunger and satiety
  • relaxes and accommodates
  • protects itself from exogenous agents
  • mixes, grinds, and empties
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9
Q

Damaging factors of the stomach

A
  • systemic diseases
  • H. pylori
  • NSAIDS, asparin, SSRI
  • toxic foods
  • alcohol
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10
Q

Structure of the stomach

A

-GI motility dependent on contractility pattern

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11
Q

Cells of the stomach

A
  • Neck/mucous cells
  • chief cells
  • parietal cells
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12
Q

Neck/mucous cells

A
  • secretes mucus and lubricates the ingested GI contents

- protect the gastric mucosa from mechanical and chemical damage (bicarbonate release, pH 6-7 at mucosa

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13
Q

Chief Cells

A
  • Release pepsinogen
  • degraded to pepsin in the presence of acid
  • main proteolytic enzyme in the stomach (optimal pH ~3.5)
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14
Q

Parietal Cells

A

-secretes hydrochloric acid (HCl)

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15
Q

Parietal cells Important in:

A
  • activation of the zymogen pepsinogen to pepsin
  • denaturation of proteins
  • killing many bacteria ingested along with food
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16
Q

Within parietal cell, HCl released by:

A
  • gastrin released by G cells into the blood
  • acetylcholine released from vagus nerve
  • histamine released from GI mast cells
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17
Q

Gastroesophageal Reflux Disease

A
  • Reflux of stomach contents back into esophagus

- relaxation of gastroesophageal sphincter

18
Q

GERD can cause:

A
  • Barrett’s esophagus
  • Chronic inflammation of esophagus
  • gastroesophageal reflux
  • is the cause of abou 1/3 of esophageal cancers
19
Q

Symptoms of Gerd

A

heart burn

20
Q

Regulatory peptides: Gastrin

A
  • synthesized by enteroendocrine cells called G-cells in the stomach and proximal small intestine
  • Stimulates the release of HCl
  • stimulates pepsinogen release
21
Q

What response leads to release of Gastrin?

A

Released in response to vagal stimulation, ingestion of specific substances or nutrients, gastric distention, Hl in contact with gastric mucosa, local and circulation hormones

22
Q

Ghrelin

A
  • produced in stomach
  • orexigenic hormone
  • elevated in the fasted state
  • increases appetite and food intake
  • rises after diet - induced weight loss
  • Annorexia & obese- dysregulaiton of ghrelin pathway
  • Gastric bypass - decrease
23
Q

Nutrients of Ghrelin

A
  • CHO - suppresses
  • protein - suppresses?
  • Fat - no effect
24
Q

Orexigenic hormone

A

stimulates food intake through hypothalamus, brainstrem

25
Q

Gut-Brain Axis

A
  • Communication between the gut and the brain through nutrients,hormones, and nerves
  • also intestines
26
Q

Meal related signals: Gut-brain axis

A
  • direct effect of food - increase in aa, glucose, and fa act directly on hypothalamus
  • visual - activats hypothalamus
  • neuronal - signals from physical measures - stomach distension
  • humoral- gut derived hormones
27
Q

Neuronal signal

A
  • Signals from physical measures - stomach distension
  • the weight or volume of food determined by meal size
  • stretch receptors signal brain through vagus nerve to brainstem
  • neurons integrate sensory information from mouth GI tract, organs
  • forwarded to hypothalamus and integrated with long-term regulators
28
Q

Response to Nutrient Ingestion

A
  1. food intake
  2. gastric accommodation: intra-gastric pressure drop
  3. further filling: intra-gastric pressure rise
  4. activation of tension receptors in the proximal stomach
  5. triggering of TLESRs
  6. Meal induced satiety –> Termination of food intake
29
Q

Helicobacter Pylori

A
  • Gram neg bacteria

- primary cause of ulcers

30
Q

H pylori symptoms

A
  • pain
  • weight loss
  • loss of appetite
  • vomiting
31
Q

causes of ulcers

A
  • smoking
  • high alcohol intake
  • stress
  • NSAIDS
32
Q

The small intestine

A

-Chyme moving from the stomach into the duodenum (initial pH 2)

33
Q

How is the duodenum protected against the gastric acidity?

A
  • pancreati secretion of bicarbonate with buffering capacity
  • mucus containing secretions from Brunner’s glands
  • viscous, alkaline (pH 8.2 - 9.3), protect the epithelial mucosa form damage
34
Q

4 tissue layers of the GI tract

A
  • Mucosa (epithelial cells that live 2-5 days)
  • Submucosa- connective tissue (has blood vessels and nerves)
  • Muscularis - smooth muscle, mixes food
  • Serosa (connective tissue) - support and protection
35
Q

Function of the Gut Interface

A
  • Filter with selective permeability – allows for movement of needed nutrients from lumen into circulation
  • Barrier with selective permeability – prevention of penetration by harmful microorganisms
36
Q

Components of the Intestinal Barrier

A
  • unstirred water layer (rate-limiting step in transport of nutrients and drugs)
  • adhesive mucous gel layers (physical friction, chemical digestion, bacterial adhesion, diffusion barrier)
  • Water: mucosal surface interface (phospholipids, NSAIDS)
37
Q

Paracellular Uptake

A
  • paracellular
  • unmediated passive diffusion
  • intestinal permeability increases following ingestion of hypertonic solution (food)
38
Q

Intestinal permeability

A
  • the facility with which the intestinal epithelium allows molecules to pass through by non-mediated passive diffusion
  • paracellular
39
Q

Increase Permeability

A
  • Ethanol and oxidants –> disrupt microtubules
  • TPN –> mucous gel layer is disrupted, hyperpermeability
  • saturated fat
  • green and black pepper extracts, MCT, chitosan
40
Q

Decrease permeability

A
  • EGCG (reduced inflammaiton)
  • fermented soy milk
  • probiotics and prebiotics
41
Q

Microbiota

A
  • large, functionally stable community of bacteria
  • ~100 trillion microbial cells
  • ~1,000 bacterial species in the GI microbiota
  • unique to the individual
  • nutrient metabolism, barrier funciton, immunity
  • impacted by diet
42
Q

Factors impacting metabolic disease

A
  • environment
  • Microbiota
  • genetics

Metabolics (4 decks)

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