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Digestive Processes
PowerPoint presentation prepared by:
Shanta Adeeb
Digestive Processes
1.
2.
3.
4.
Mechanical Breakdown (Ingestion)
Digestion
Absorption
Excretion
Mechanical Breakdown

Mostly in the mouth. Also in the
stomach

The first of the four stages
Digestion

Breaks down food into molecules
small enough to be absorbed



Proteins to peptides and amino acids
Complex carbohydrates to simple sugars
Lipids to fatty acids
Absorption

Nutrients are taken up by cells that
line the digestive tract


Different nutrients are taken up at
different rates
Nutrients are converted to energy that
may be immediately used or stored


Fat
Glycogen
Excretion
The last stage of food processing in
the body
 Undigested wastes pass out of the
digestive tract


Role of insoluble fiber and water
Digestive Components
Processes take place in specific organs:
 Mouth
 Esophagus
 Stomach
 Small Intestine
 Large Intestine
Mouth

Food enters and is reduced in size by
teeth and tongue

Salivary glands secrete saliva, which
lubricates and buffers food (bolus),
amylase (enzyme) starts starch
digestion
Esophagus
Food passes through on its way to
the stomach
 No functional role, it’s just a pipe

Stomach



Stores and digests
food
One quart (4 cup)
capacity – can be
stretched
Food retention is 2
to 3 hours at
capacity
Stomach

Mucus produced protects lining from
acid

Ulcers are caused by a specific
bacterium, Hilobacter pylori
Secretes hydrochloric acid (HCl)
 Produces enzyme pepsin (protein
digestion)

Small Intestine

10 ft long

Very large surface area ~200 m2

(15 x 15 yards) due to villi
and microvilli

Retains food 3 to 10 hours
Small Intestine

Receives enzymes from pancreas

Site of most digestion and absorption
Large Intestine

3 ½ ft long
Retains food up to 72 hours (less w/
insoluble fiber).
(72 h is not good.)
 “The beet test.”

“The beet test”
Learning objective: Student will gain experiential
understanding of “intestinal transit time.”
Was once amusing, not it’s just gross.
Other Components

Esophageal sphincter: blocks acid
reflux

Liver: produces bile salts which
emulsifies fats
Other Components

Gallbladder: stores bile salts

Pancreas: secretes digestive
enzymes and insulin
VIDEO
(Can read full screen from web site
This is an excellent review.
Food industry addresses supplement issues using
country specific marketing tools.
Sex sells both here and aboard.