The document discusses the human digestive system, including the five phases of digestion: ingestion, mechanical digestion, chemical digestion, absorption, and elimination. It describes the two types of digestion - mechanical and chemical - and the major organs involved, including the mouth, esophagus, stomach, small intestine, large intestine, liver, gallbladder and pancreas. The small intestine absorbs nutrients from digested food while the large intestine absorbs water and solidifies waste before it is eliminated from the rectum.

2. Digestion
• Phases Include
1. Ingestion
2. Mechanical Digestion
3. Chemical Digestion
4. Absorption
5. Elimination

3. Types of Digestion
• Types
– Mechanical (physical)
• Chew
• Tear
• Grind
• Mash
• Mix
– Chemical
• Enzymatic reactions to improve digestion of:
– Carbohydrates
– Proteins
– Lipids

4. Digestive System Organization
• Gastrointestinal (Gl)/Digestive tract
–Direct path between organs
–Structures include, in this order:
• Mouth
• Pharynx
• Esophagus
• Stomach
• Small intestine
• Large Intestine
• Rectum
4

5. Mouth:
• Teeth mechanically
break down food into
small pieces.
• The tongue mixes food
with saliva to start
chemical digestion
(contains amylase,
which helps break down
starch).
• Epiglottis is a flap-like
structure at the back of
the throat that closes
over the trachea
preventing food from
entering it when
swallowing.

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7. Esophagus:
• Approximately 10” long
• Functions include:
1.Secrete mucus
2.Move food from the throat to
the stomach using wave-like
muscle movement called
peristalsis.
• If acid from the stomach gets
in the esophagus it causes
what we call heartburn.

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9. Stomach:
• J-shaped muscular bag that stores the food
you eat, breaks it down into smaller pieces.
• Mixes food with digestive secretions that
contain the enzyme pepsin to break down
proteins and starts the breakdown of lipids.
• Hydrochloric Acid in the stomach attempts
to kill incoming bacteria, parasites, viruses,
fungi, etc and is indirectly responsible for
some chemical digestion. It’s main function
is to lower the pH of the stomach so that
pepsin can function efficiently.
• Food found in the stomach mixed with
these secretions is called chyme. 9

10. Small Intestine:
• Small intestines are approximately 20 feet
long in an adult.
• The lining of intestine walls have finger-
like projections called villi, to increase
surface area.
• The villi are then covered in microvilli
which further increases surface area for
absorption.
• Divided into 3 segments:
1. Duodenum
2. Jejunum
3. Illeum
10

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12. Small Intestine:
• Nutrients from the digested food pass
into the bloodstream by diffusing
across the walls of the small intestine.
• Absorbs:
– 80% ingested water
– Vitamins
– Minerals
– Carbohydrates
– Proteins
– Lipids
• Secretes the digestive enzyme
lipase. 12

13. Large Intestine:
• Approximately 5 feet in length.
• Absorbs remaining water for reuse
by the body.
• Includes the Rectum, which is the
last segment of the large intestine
and serves as short term storage by
holding the feces until it can
expelled.
• Divided into 3 segments:
1. Ascending colon
2. Transverse colon
3. Descending colon

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15. Large Intestine:
• Functions:
– Digestion further aided by
bacteria
• Ferment remaining
carbohydrates
• Additional protein
breakdown
– Absorbs more water
which further concentrates
and solidifies the fecal
matter.

16. Accessory Organs:
• Not part of the path
that food follows,
but still play a critical
role.
• Include: Liver, Gall
Bladder and
Pancreas

17. Liver:
• Stores extra blood (~10% of body’s
blood volume)
• Filters out toxins
• Metabolism of fats for energy
• Production of clotting proteins
• Breakdown in ”old” RBCs
• Production of necessary cholesterols
• Modification of steroid hormones
• Maintain electrolyte balance
• Maintain blood pH
• Produces bile
– Bile helps digest fat 17

18. Liver continued…
• Storage of essential vitamins and minerals
• Functions as part of the immune system via
Kupffer cells, which are fixed macrophages.
• Filters approximately 1.4 liters of blood per
minute!
• Has been shown to regenerate up to 75% of
its original structure.
• Regulation of blood sugar.
• Etc…
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19. Gall Bladder:
• Stores bile from the
liver, releases it into the
small intestine.

20. Pancreas
• Produces digestive
enzymes to aid in the
digestion of fats,
carbohydrates and
proteins.
• Regulates high blood
sugar by producing
insulin. (Beta cells)
• Regulates low blood
sugar by releasing
glucagon. (Alpha cells)

21. Fun Facts
• HOW LONG ARE YOUR INTESTINES? An
average of 25 ft in an adult.
• Be glad you're not a full-grown horse -- their coiled-
up intestines are 89 ft long!
• Food passing through the large intestine can
take anywhere from 18 hours to 2 days!
• In your lifetime, your digestive system handles
about 50 tons!!