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9/3/2019
1
Website:
websites.rcc.edu/halama
Lecture 2
Digestive System
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Lecture 3
1. Introduction
2. Digestive System
3. Nutrition Basics
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Introduction
Some Ecology
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Mr. Sun
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Nuclear Fusion
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Light energy from Sun…
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…radiates across space.
Light energy from Sun…
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…radiates across space.
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strikes the Earth’s surface… 9
A very small percentage…
Light Energy Absorbed…10
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Photosynthesis
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Energy stored here
Plants! Important!
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Consumers
Digestive System
• Begins the process of “harvesting” the solar
energy, and other things, contained within food.
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Digestive System
Breaks down ingested food (large molecules) into
small molecules, via mechanical and chemical means.
Digestive System
The material is absorbed by the body and used for
various functions where needed.
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Digestive System
• Begins the process of “harvesting” the solar
energy, and other things, contained within food.
• Breaks down ingested food (large molecules) into
small molecules, via mechanical and chemical
means.
• The material is absorbed by the body and used for
various functions where needed.
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Digestive System
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Digestive System, Five Functions
1. Breaks up food into small pieces
2. Transports food through the alimentary canal
(gut) via rhythmic muscular contractions
(peristalsis)
3. Secrets digestive enzymes to breakdown food
4. Absorbs nutrients into the bloodstream
5. Excretes solid wastes of digestion (whatever
is left over).
Digestive System
1. Mouth (Buccal Cavity)
2. Esophagus
3. Stomach
4. Small Intestines
5. Large Intestine (Colon)
6. Secretory Glands (Salivary Glands, Liver,
and Pancreas)
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Mouth
• Teeth, mechanical
breakdown:
• Salivary Glands - Saliva,
mixes with food and
begins chemical
breakdown.
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Teeth!
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Esophagus…
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Esophagus
• Connecting tube between the pharynx and
the stomach, or between pharynx and
intestine.
• Peristalsis
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Muscles
Contracted
Peristaltic Contractions – waves of rhythmic relaxation and
contraction of the muscles in the alimentary canal that move
along the canal and act to push the contents from the mouth
toward the rectum.
Muscles
Relaxed
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Esophagus Specialization:
Egg Eating Snake
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Stomach
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Stomach Cardiac Sphincter
Pyloric Sphincter
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Lining of the Stomach: Gastric Pits
Cells secrete Hydrochloric Acid (HCl)
Lining of the Stomach: Goblet Cells
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These cells secrete mucous - protects the
stomach lining
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Stomach
Cardiac Sphincter
Pyloric Sphincter
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When empty, the stomach is contracted and the lining is
“bunched up” into distinct folds called Rugae; when distended
with food, the rugae flatten out.
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Stomach - ingest Cardiac Sphincter,
Open
Pyloric Sphincter, Closed
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Cardiac Sphincter,
Closed
Pyloric Sphincter, Closed
Stomach - peristalsis
Chyme
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Gastroesophogeal Reflux Disease
(GERD)Cardiac Sphincter,
Open
Pyloric Sphincter, Closed
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Bird Stomach
ProventriculusGizzard
Sphincter Sphincter
Posterior EndAnterior End
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?
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Dinosaur
Gastroliths
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Intestines
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Intestines Serve Three Main
Functions:
1. Continues the digestive process begun by
the mouth and stomach
2. Selectively absorbs final products of
digestion
3. Moves the food through the system via
peristalsis.
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Intestine Regions
1. Small Intestine – where digestion and
nutrient absorption takes place.
2. Large Intestine (Colon):
A. Reabsorb water
B. Consolidate feces.
C. Synthesizes Vitamin K which is necessary for
blood clotting.
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Small Intestine:
Three Sections
1. Duodenum – chemical digestion
2. Jejunum – absorption
3. Ileum - absorption
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Duodenum
• shortest part of the small
intestine (~ 25 - 30 cm),
• site of most chemical digestion
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Duodenum
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Jejunum
• Jejunum - Second longest part
of the small intestine (~ 2 - 3
meters),
• Main site of nutrient
absorption in Small Intestine
• Most of the nutrients present in
food are absorbed by the
jejunum before being passed on
to the ileum for further
absorption.
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Ileum
• Ileum - longest part of
the small intestine (~ 2 -
4 meters),
• Absorbs vitamins (B12)
and water,
• And anything not
absorbed by the illium.
Absorption?
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Absorption?
Villi and Microvilli increase surface area!
~250 square meters (almost 2,700 square
feet) – the size of a tennis court!
Without Villi and Microvilli, surface area
would be about 15 -20 square feet.
Large Intestine (Colon)
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Large Intestine (Colon)
1. Primary Function – water absorption and
feces consolidation.
2. Vitamin K produced by bacteria
What about the appendix?
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A thin tube about four inches long, located at the junction of
the small intestine and large intestine in the lower right
abdomen.
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What about the appendix?
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Once thought to be a “vestigial” organ – an organ that once
served a purpose in our evolutionary past, but no longer
serves any function.
What about the appendix?
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NOW, is believed to serve an important function – a haven for
useful gut bacteria when illness flushes those bacteria from
the rest of the intestines.
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What about the appendix?
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Appendicitis - for unclear reasons, the appendix often becomes
inflamed, infected, and can rupture. This causes severe pain in
the right lower part of the belly, along with nausea and vomiting.
Secretory Organs
Salivary Glands, Liver, and
Pancreas
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Salivary Glands
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Saliva – enzymes that begin carbohydrate digestion
Liver and Gall Bladder
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Does lots of different stuff !
Produces Bile. Stored in the Gall Bladder. Bile
aids in fat digestion.
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Pancreas
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