Gastrointestinal Lecture 1 Part 4 The Mouth and Stomach Flashcards

1
Q

Anatomy of the digestive system

A
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2
Q

Functions of the mouth

A

Mechanical breakdown of food

  • Mastication (chewing)
  • teeth and facial muscles help to move jaw for chewing

Preparation for swallowing

  • Moistening of food bolus
  • saliva produced by salivary glands

Onset of digestion

  • Enzymatic breakdown of carbohydrates
    • minor contribution
    • salivary amylase
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3
Q

What is swallowing?

A

Reflex response under control of the autonomic nervous system which includes includes closure of the glottis and inhibition of respiration

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4
Q

Phases of respiration

A
  • oral phase
  • pharyngeal phase
  • esophageal phase
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5
Q

oral phase of swallowing

A
  • Initiated by voluntary collection of food bolus into the pharynx by the tongue (oral phase)
    • Tongue pushes food to bolus to back of mouth
    • conscious act of swallowing triggers reflex
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6
Q

Pharyngeal phase of swallowing

A

Triggers involuntary contraction of pharyngeal muscles, pushing bolus into esophagus

  • Soft palate elevates to prevent food entering the nasal passage
  • Epiglottis covers the glottis, preventing bolus entry into the trachea, upper esophageal sphincter relaxes
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7
Q

Esophageal phase of swallowing

A

Bolus driven down esophagus by peristaltic contraction (speed = ~4 cm/s)

  • Foods descends the esophagus
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8
Q

What is extreme mastication called?

A

fletchication

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9
Q

What is fletchication?

A

Coined by Horace Fletcher

  • Food faddist
  • Targeting economic hardship (not weight loss!)
  • Advocated for “Fletcherizing”: chewing food until it is liquified to enhance nutrient absorption (100s chews/bite)
  • Claimed to decrease food consumption by 1/3 and decreased feces production by 1/10! Unsubstantiated.
  • Ignored millions of years of evolution that optimized the gut for nutrient absorption, including the stomach’s role in breaking down and liquifying ingested food
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10
Q

Anatomy of the stomach

A
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11
Q

FUnctions of the stomach

A
  • Stores ingested material
  • Continues digestion (dissolves and breakdowns food bolus and macromolecules)
  • Regulates emptying into small intestine and makes sure it is not overwhelmed by the food
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12
Q

How does digestion occur within the stomach?

A

mechanical and chemical

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13
Q

Mechanical digestion in the stomach

A

facilitated by folded surface (rugae) which facilitate mixing and grinding

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14
Q

Chemical digestion of food

A

HCl

  • acidity denatures proteins (more soluble) cleaves pepsinogen → pepsin

Pepsin

  • Enzyme that breaks down protein
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15
Q

Purpose of different parts of the stomach

A
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16
Q

What does ingested food leave the stomach as?

A

`chyme