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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
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