The Digestive System
• The digestive
system consists
of an
alimentary
canal and
several
accessory
organs.
The Digestive System
• The digestive system mechanically and chemically
breaks down food.
• Mechanical digestion includes chewing and
peristalsis.
• Chemical digestion includes the use of enzymes.
The Digestive System
Digestion =
Nutrients =
Big
Little
Food
Nutrients
carbohydrates
sugars
fats
fatty acids + glycerol
proteins
amino acids
The Digestive System
• Essential
nutrients are
absorbed into the
body and the
unused waste
material is
excreted out of
the body.
The Digestive System
The Alimentary Canal
The Digestive System
III. The Alimentary Canal
A. Wall Layers
1. Mucosa
Structure: composed of
epithelial, connective, and
smooth muscle tissue; mucus
secreting glands present
Function: protection,
absorption, secretion
2. Submucosa
Structure: composed of loose
connective tissue; glands, blood
and lymph vessels present
Function: nourishment
The Digestive System
III. The Alimentary Canal
A. Wall Layers
3. Muscular layer
Structure: composed of 2 layers
of smooth muscle; circular and
longitudinal shaped fibers
Function: movement
4. Serosa
Structure: composes the outer
layer of the canal
Function: secretion of fluid to
lubricate so tube can slide feely
The Digestive System
IV. The Oral Cavity
The Digestive System
V. The Teeth
The Digestive System
VI. The Pharynx
The Digestive System
VII. The Salivary Glands
The Digestive System
VIII. The Stomach
The Digestive System
IX. The Small Intestine
The Digestive System
X. The Large Intestine
The Digestive System
XI. The Liver
The Digestive System
XII. The Gall Bladder and Pancreas
Overview
Salivary Glands
Oral Cavity
(amylase)
Esophagus
Stomach
Pancreas
(lipase, amylase, trypsin,
chymotrypsin,
carboxypeptidase: pancreatic
juice)
(HCL and pepsinogen = pepsin)
Small Intestine
(peptidase, lipase, sucrase,
maltase, lactase)
Blood
(fatty acids, glycerol, amino
acids, monosaccharides)
Liver/Gall Bladder
(bile/bile salts)
Large
Intestine
Blood
(bacteria = intestinal flora)
(water, electrolytes, vitamins)
Rectum
The Digestive System
Digestion =
Nutrients =
Big
Little
Food
Nutrients
carbohydrates
sugars
fats
fatty acids + glycerol
proteins
amino acids
Chemical Digestion and Nutrients
Carbohydrates
•
Uses in the Body:
used primarily to supply energy for cellular processes
Chemical Digestion and Nutrients
Carbohydrates
•
Dietary Sources:
- starch from grains and vegetables
- glycogen from meats
- monosaccharides from honey and fruits
•
Dietary Requirements:
- Varies among individuals
- Depends on amount of physical activity, body size and
metabolic rate.
Chemical Digestion and Nutrients
Carbohydrate Digestion (starch to monosaccharide)
Pancreas
Chemical digestion by
pancreatic amylase (breaks
down carbohydrates into
disaccharides)
Mouth
Mechanical digestion
Chemical digestion
by salivary amylase (breaks down
carbohydrates into disaccharides)
Stomach
Small Intestine
Mechanical digestion
Chemical digestion by
sucrase, maltase + lactase
(break down disaccharides
into monosaccharides:
sucrose…)
Small Intestine
Glucose absorbed into blood
Chemical Digestion and Nutrients
Lipids
•
Uses in the Body:
-supplies energy for cellular processes and for building
cellular structures
Chemical Digestion and Nutrients
Lipids
•
Dietary Sources:
- saturated fats found in meats, eggs and milk
- unsaturated fats found in seeds, nuts and plant oils
- monosaturated fats found in olive, peanut and canola
oils
•
Dietary Requirements:
- Recommended to be less than 30% of total calories
- Depends on amount of physical activity, body size and
metabolic rate.
Chemical Digestion and Nutrients
Lipid Digestion (fat to glycerol + fatty acid)
Pancreas
Liver/
Gall Bladder
Chemical digestion by Mechanical digestion by bile
pancreatic lipase (breaks (bile crystallizes into bile salts
down lipids)
and aid in lipid breakdown)
Mouth
Stomach
Small Intestine
Mechanical digestion
Mechanical digestion
Chemical digestion by
intestinal lipase (breaks
down lipids)
Small Intestine
Glycerol and fatty acids
absorbed into lymphatic
system.
Chemical Digestion and Nutrients
Proteins
•
Uses in the Body:
- all cells in your body make proteins. In order to
synthesize proteins, body needs a supply of amino acids
(from food).
- enzymes, clotting factors, keratin of skin and hair,
collagen of connective tissue, plasma proteins, muscle
proteins, hormones and antibodies.
Chemical Digestion and Nutrients
Protein
•
Dietary Sources:
- meats, fish, poultry, cheese, eggs and cereals
•
Dietary Requirements:
- Between 60 to 150 grams per day
- Depends on amount of physical activity, body size and
metabolic rate.
Chemical Digestion and Nutrients
Protein Digestion (protein to amino acids)
Pancreas
Chemical digestion by
trypsin, chymotrypsin +
carboxypeptidase (break
specific bonds between
amino acids)
Stomach
Mouth
Mechanical digestion
Mechanical digestion
Chemical digestion by
HCl acid and pepsin 
pepsinogen (breaks
specific bonds between
amino acids)
Small Intestine
Chemical digestion by
peptidase (breaks specific
bonds between amino
acids)
Small Intestine
Amino acids absorbed