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Digestion

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Introduction

Digestion is defined as the breakdown of nutrients

We consume: Proteins Carbohydrates Fats These are broken down into their simplest

forms

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From Beginning to End

Mouth Esophagus Stomach Small intestine Large intestine Anus

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Mouth

Mechanical digestion: the act of chewing Carbohydrate digestion begins here Saliva moistens food and contains the enzyme

Salivary Amylase – breaks down complex carbs into simple sugars

Chemical Digestion: enzymes breaking down carbohydrates

Ball of moistened, partially digested food, known as the “BOLUS”, moves into the esophagus

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Esophagus

Long tube through which “bolus” moves down into the stomach

The contraction of muscles pushes the food down – known as PERISTALSIS

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Stomach

Protein digestion begins here Gastric Glands: Parietal Cells Chief Cells Chief Cells release HCl, the acidity kills foreign

material and bacteria Parietal Cells release the inactive enzyme

Pepsinogen. This combines with HCl to create active form: Pepsin

Pepsin breaks down proteins into smaller polypeptide chains or amino acids

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Just a Reminder… Both types of digestion are occurring in

the stomach: Mechanical and Chemical The churning of the stomach is considered

mechanical digestion The enzyme activity is considered

chemical digestion

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Small Intestine

Continuation of Carbohydrate and Protein Digestion; beginning of Fat digestion

LIVER: releases bile that breaks down fats into fatty acids

PANCREAS: releases pancreatic juices, one of which completes protein digestion (proteins to amino acids) and carbohydrate digestion (complex sugars into simple monosaccharides)

Absorption of simple nutrients through villi occurs here

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Large Intestine

Unabsorbed material moves through large intestine, where water and salt are absorbed

This removal of liquid forms solid-like feces

Feces is stored in the colon Feces is removed from the body, via the

anus

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