The document discusses the human digestive system, including its main phases, types of digestion, organization, and key organs. The phases are ingestion, movement, mechanical and chemical digestion, absorption, and elimination. Mechanical digestion involves physical breakdown through chewing, tearing, etc. while chemical digestion uses enzymes to break down carbohydrates, proteins, and lipids. The main organs discussed are the mouth, esophagus, stomach, small intestine, large intestine, liver, gallbladder, and pancreas. The small intestine absorbs most nutrients with finger-like villi and microvilli increasing surface area for absorption. The pancreas produces enzymes and regulates blood sugar.

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

3. 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) tract
– Tube within a tube
– Direct link/path between organs
– Structures
• Mouth
• Pharynx
• Esophagus
• Stomach
• Small intestine
• Large Intestine
• Rectum
4

5. Mouth
• Teeth mechanically
break down food into
small pieces. Tongue
mixes food with saliva
(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.

6. Esophagus
• Approximately 10” long
• Functions include:
1. Secrete mucus
2. Moves food from the throat to
the stomach using muscle
movement called peristalsis
• If acid from the stomach gets in
here that’s heartburn.

7. Stomach
• J-shaped muscular bag that stores the food
you eat, breaks it down into tiny pieces.
• Mixes food with digestive juices that
contain enzymes to break down proteins
and lipids.
• Acid in the stomach kills bacteria.
• Food found in the stomach is called chyme.
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8. Small Intestine
• Small intestines are roughly 7 meters long
• Lining of intestine walls has finger-like
projections called villi, to increase surface
area.
• The villi are covered in microvilli which
further increases surface area for
absorption.
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10. Small Intestine
• Nutrients from the food pass into the
bloodstream through the small
intestine walls.
• Absorbs:
– 80% ingested water
– Vitamins
– Minerals
– Carbohydrates
– Proteins
– Lipids
• Secretes digestive enzymes
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11. Large Intestine
• About 5 feet long
• Accepts what small intestines don’t
absorb
• Rectum (short term storage which
holds feces before it is expelled).

12. Large Intestine
• Functions
– Bacterial digestion
• Ferment carbohydrates
• Protein breakdown
– Absorbs more water
– Concentrate wastes

13. Accessory Organs
• Not part of the path
of food, but play a
critical role.
• Include: Liver, gall
bladder, and
pancreas

14. Liver
• Directly affects digestion by producing
bile
– Bile helps digest fat
• filters out toxins and waste including
drugs and alcohol
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15. Gall Bladder
• Stores bile from the
liver, releases it into the
small intestine.
• Fatty diets can cause
gallstones

16. Pancreas
• Produces digestive
enzymes to digest fats,
carbohydrates and
proteins
• Regulates blood sugar
by producing insulin

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Organ Function
Mouth Chewing, Digestion of starch by salivary amylase
Esophagus
transport of food from mouth to stomach; lubricated by
mucus
Stomach
Storage of food and initial digestion of proteins + fats;
production of the hormone gastrin (response to protein)
that stimulates stomach's gastric glands to release gastric
juice (including pepsin and HCl)
Small intestine
Continued digestion of carbohydrates, proteins, lipids; most
absorption of nutrients; production of the hormone secretin
(response to HCl) that stimulates pancreas to release
bicarbonate; production of the hormone CCK (response to
fat) that stimulates gall bladder to release bile
Pancreas
Production of digestive enzymes that act in small intestine;
production of the hormones insulin and glucagon which
regulate blood sugar; production of bicarbonate that
neutralizes stomach acid in small intestine
Large intestine
Absorption of water; Production of some vitamins; storage
of undigested food

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Organ Secretion and Function
Salivary glands
salivary amylase - converts starch (a polysaccharide) to maltose (a
disaccharide)
Esophagus mucus - helps movement of food
Stomach
HCL- Converts pepsinogen to pepsin and kills microbes
Pepsinogen - Pepsin, digests proteins to polypeptides & peptides
Lipase - Converts lipids into glycerol and fatty acids
Mucus - Protects stomach from pepsin and HCl
Renin - Coagulates proteins in milk to slow movement
Pancreas;
Small intestine Pancreatic amylase - Converts starch to maltose
Bicarbonate - Neutralizes HCl from stomach
Enterokinase - Converts trypsinogen to trypsin
Trypsinogen - Trypsin, converts proteins into peptides
Erepsin - Converts peptides into amino acids
Lipase - Converts lipids into glycerol and fatty acids
Maltase - Converts maltose (a disaccharide) into two glucose
sucrase - Converts sucrose into glucose and fructose
Lactase - Converts lactose into glucose and galactose
Liver / Gall
bladder
Bile - Emulsifies fat (large globules into smaller ones for lipase to
work)
Large intestine Mucus - helps movement of food
Table 2: Substances Involved in Digestion
Organ Secretion and Function
salivary glands
salivary amylase - converts starch (a
polysaccharide) to maltose (a
disaccharide)
esophagus mucus - helps movement of food
stomach
hydrochloric acid - converts
pepsinogen to pepsin and kills
microbes
pepsinogen - when converted to
pepsin, initiates digestion of proteins
(long chains of amino acids) to
polypeptides and peptides (shorter
chains of amino acids)
lipase - converts lipids (eg.
triglycerides) into glycerol and fatty
acids
mucus - protects stomach from pepsin
and HCl
renin - coagulates proteins in milk to
slow movement
pancreas; small intestine
pancreatic amylase - converts starch
(a polysaccharide) to maltose (a
disaccharide)
bicarbonate - neutralizes HCl from
stomach
enterokinase - converts trypsinogen to
trypsin
trypsinogen - when converted to
trypsin, converts proteins into peptides
erepsin - converts peptides into amino
acids
lipase - converts lipids (eg.
triglycerides) into glycerol and fatty
acids
maltase - convets maltose (a
disaccharide) into two glucose (a
monosaccharide)
sucrase - convets sucrose (a
disaccharide) into glucose and
fructose (monosaccharides)
lactase - convets lactose (a
disaccharide) into glucose and
galactose(monosaccharides)
liver
bile - emulsifies fat (large globules into
smaller ones for lipase to work)
gall bladder
bile - stores concentrated bile from
liver
large intestine mucus - helps movement of food

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20. Facts
• HOW LONG ARE YOUR INTESTINES? At least 25 feet
in an adult!
• Food drying up and hanging out in the large intestine
can last 18 hours to 2 days!
• In your lifetime, your digestive system may handle
about 50 tons!!

22. On a sheet of paper, write the name of
each colored organ:
• Green:
• Red:
• Pink:
• Brown:
• Purple:
• Green:
• Yellow:

23. How’d you do?
• Light Green: Esophagus
• Red: Stomach
• Pink: Small Intestine
• Brown: Large Intestine
• Purple: Liver
• Dark Green: Gall Bladder
• Yellow: Pancreas
Great Job!