Digestion

1
Digestion

• School of Education - CCNY

2
Introduction

• Digestion is defined as the breakdown of
  nutrients
• We consume
• Proteins
• Carbohydrates
• Fats
• These are broken down into their simplest forms

3
From Beginning to End

• Mouth
• Esophagus
• Stomach
• Small intestine
• Large intestine
• Anus

4
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

5
Esophagus

• Long tube through which bolus moves down into
  the stomach
• The contraction of muscles pushes the food down
  known as PERISTALSIS

6
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

7
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
• Chemical gt Mechanical

8
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, 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

9
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, by
  the process of ELIMINATION