Transcript Digestive System - Effingham County Schools

The Digestive System
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Major Functions
• Digestion- Break down food into the
nutrients the body can absorb.
• Absorption- Take out nutrients out of the
food we eat and deliver it to the cells in our
body.
• Eliminate solid wastes that is not needed
by the body.
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Digestion
• Processing of food
• Types
– Mechanical (physical)
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•
•
Chew
Tear
Grind
Mash
Mix
Examples of
Mechanical
Digestion
– Chemical- uses catabolic reactions and enzymes to
break down food
• Saliva
• Stomach Acids
• Bile used to break down fats
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Digestion
• Phases
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Ingestion
Movement
Digestion
Absorption
Further digestion
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Digestive System Organization
• Gastrointestinal (Gl) tract
– Tube within a tube
– Direct link/path between organs
– Major Organs:
MouthPharynx Esophagus Stomach  Small Intestines
Large Intestines Rectum
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Digestive System Organization
• Accessory Organs
– Not in tube path
– Organs
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Teeth
Tongue
Salivary glands
Liver
Gall bladder
Pancreas
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Mouth- where digestion begins
Teeth- Mechanical Digestion
Salivary Glands- Chemical digestion of compounds such as
starch
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Teeth- Mechanical Digestion
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Surface of the Tongue
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The Major Salivary Glands
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__________________
Peristalsis
Deglutition (swallowing)
• Sequence
– A. Voluntary stage
• Push food to back of
mouth
– B. Pharyngeal stage
• Raise pallate
- C. Esophageal stage- Contract
pharyngeal muscles, open
esophagus, start peristalsis
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Esophagus
• Usually collapsed
(closed)
• Functions
– Secrete mucous
– Transport food to the
stomach
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Peristalsis
Contractions of smooth muscles
that push food down the
digestive tract
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Esophagus
• Sphincters
– Upper
– Lower
• Abnormalities
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Achalasia
Atresia
Hernia
Barret’s esophagus
Esophageal varices
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Stomach
• Usually “J” shaped
• Mucous membrane
– G cells – make gastrin
– Goblet cells – make mucous
– Gastric pit – Oxyntic gland – Parietal cells – Make
HCl
– Chief cells – Zymogenic cells
• Pepsin
• Gastric lipase
Very Acidic, but the cells are produced faster than they die
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Anatomy of the Stomach
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Stomach
• Functions
1. Mix food- Mechanically
2. Reservoir- Store food
3. Start chemical digestion of
• Protein
• Nucleic acids
• Fats
5. Absorbs
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Alcohol
Water
Lipophilic acid
B 12
4. Destroy some bacteria
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Stomach
Function- To mix, break
down (chemically and
mechanically), and store
food.
• Inner surface thrown into
folds – Rugae
• Contains enzymes that work
best at pH 1-2 (VERY
ACIDIC)
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Stomach
• Food leaves the
stomach as a soupy
mixture called chyme
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Small Intestine
• Function- Major site
of chemical digestion
and absorption.
• Movements
– Peristalsis
• Absorbs
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–
–
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80% ingested water
Vitamins
Minerals
Carbonates
Proteins
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Structure of the Villi in the
Small Intestine
Villi- Increase
surface area for
absorption.
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Small Intestine- Accessory
Organs
• Liver- Creates bile
that is used to break
down fats.
• Gal bladder- Stores
bile and releases it
into the small
intestines
• Pancreas- Creates
pancreatic juices that
neutralize the chyme.
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Anatomy of the Large Intestine
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Large Intestine
Function- To reabsorb water from digested
wastes to make solid wastes.
- No villi
– No permanent circular folds
– Smooth muscle
•Chyme dehydrated to form feces
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Feces Formation and Defecation
“whats in it?”
• Chyme dehydrated to
form feces
• Feces composition
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Water
Inorganic salts
Epithelial cells
Bacteria
Byproducts of digestion
Defecation
– Peristalsis pushes feces into
rectum
– Rectal walls stretch until full
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Anatomy of the Large Intestine
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The Organs and Positions in the
Abdominal Cavity
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Video of the digestion of food- The whole picture
http://highered.mcgrawhill.com/sites/0072495855/stude
nt_view0/chapter26/animation__
organs_of_digestion.html
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Digestive Disorders
Chrone’s Disease (inflammatory bowel syndrome)Inflammation of the intestines
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Digestive disorders
Blind loop syndromeDiarrhea- increased
Blind loop syndrome
frequency of watery
occurs when part of the
feces. Causing
intestine becomes
dehydration and
bypassed, so that digested
food slows or stops moving
abdominal pain.
through the intestines. This
causes bacteria to grow too
much in the intestines and
leads to problems in
absorbing nutrients.
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Digestive Disorders
Phenylketonuria (PKU)- is a rare condition in which a
baby is born without the ability to properly break down
an essential amino acid called phenylalanine.
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Symptoms
•Lighter skin and hair color
•Delayed mental and social
skills
•Bad breath and odor from
skin and urine.
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PKU is a recessive trait and therefore both parents must
carry the allele to pass the trait.
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Mouth
Salivary gland
Esophagus
Liver
Gal Bladder
Small Intestines
Stomach
Pancreas
Large Intestines
Rectum
Anus
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