Download The Human Digestive System

THE DIGESTIVE
SYSTEM
SNC2D
Phases of Digestion
Mechanical (physical)
• Phases Include
1.
Ingestion
2.
Movement
3.
Mechanical and
Chemical Digestion
4.
Absorption
5.
Elimination
Chew
Tear
Grind
Mash
Mix
Chemical
Enzymatic reactions to improve
digestion of
Carbohydrates
Proteins
Lipids
The Digestive Tract
The Digestive tract is…
•a series of hollow
organs which may be
thought of as a long
twisting tube connecting
the mouth to the anus,
and other organs that
produce or store
chemicals that help
break down or absorb
food.
The Mouth
Digestion begins in the mouth where an enzyme (a
chemical that speeds up other chemical reactions) in the
saliva produced by the salivary glands start to break down
those carbohydrates known as starches. This enzyme is
called amylase.
The Mouth Cont’d
• 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.
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.
Peristalsis
Once the food is swallowed, it is moved
through the digestive tract by
peristalsis, involuntary muscle
contractions triggered by the nervous
system.
To The Stomach
Food travels down the esophagus to the stomach.
Between the esophagus and the stomach there is
a muscle called the lower esophageal
sphincter, which opens to let food pass through.
If it opens when it shouldn't’t, you get acid reflux
(heartburn).
In the Stomach
Glands in the stomach lining produce stomach acid and an
enzyme to break down proteins. A thick layer of mucus
helps protect the lining of the stomach from its own acids.
Bacterial infections can thin
the mucus so that the
stomach eats away at its
own lining: this is an ulcer.
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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.
Muscle action of the stomach mixes
the food with the digestive juices, and
this mixture is then emptied into the
small intestine through the pyloric
sphincter.
The Small Intestine
The first part of the small intestine, where the
chemicals produced by the other organs enter
the digestive process, is called the duodenum.
Nutrients from the food pass into the blood stream
through the small intestine walls.
Absorbs :
- 80 % of ingested water
- Vitamins
- Minerals
- Carbs
- Proteins
- Lipids
The Small Intestine
The small intestine is roughly 7 meters long, folded into fingerlike
projections called villi. This folding increases the surface area of the
small intestine through which food molecules are absorbed into the
bloodstream. Villi are covered in microvilli which further increases
surface area for absorption!
The Large Intestine (colon)
Is about 5 ft long, accepts
what small intestine don’t
absorb
Functions include
- bacterial digestion
(fermenting carbohydrates
and protein breakdown )
- Absorption of water
- Concentrating Wastes
Accessory Organs
• Not part of the path of food,
but play a critical role.
• Include: Liver, gall bladder,
and pancreas
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Liver
• Directly affects digestion by
producing bile
• Bile helps digest fat
• filters out toxins and waste
including drugs and alcohol
Gall Bladder
• Stores bile from the
liver, releases it into
the small intestine.
• Fatty diets can cause
gallstones
Pancreas
• Produces digestive enzymes
to digest fats, carbohydrates
and proteins
• Regulates blood sugar by
producing insulin
The Body’s Defences
The digestive system’s first defence against
contaminants is vomiting, which can
forcibly remove contents from the middle of
the small intestine and up.
Really, you don’t want any images here.
Fun Facts
• HOW LONG ARE YOUR INTESTINES? At least 25 feet
in an adult. Be glad you're not a full-grown horse -- their
coiled-up intestines are 89 feet long!
• 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!!