The Digestive System! :D
ZANE SMITH
Homeostasis and Interdependence
 The Digestive System is necessary for maintaining
homeostasis because it breaks food down into means
of energy that can be used by cells.
 The nutrients provided from food is transported to
cells all around the body.
Forms of Digestion
 Mechanical Digestion
 Physical breakdown of food due to movement of organ
 Ex. Chewing and Stomach movement
 Chemical Digestion
 Breakdown of food facilitated by enzymes
 Ex. Stomach acids
Evolution of the Digestive System
 Incomplete Digestive Tract
 No specialized organs/parts. Only a single orifice for food
intake and food waste.
 Ex. Planarians – Digestive cavity takes up majority of internal
volume. Cells receive nutrition through Diffusion
 Complete Digestive Tract
 Contains specialized organs/parts. Has a mouth for food
consumption and an anus for food waste.
 Ex. Annelids
Evolutionary Adaptations with Diet
 Dentition (Teeth)
 Different types of teeth are attributed to diet
Carnivores – Pointed and jagged teeth for
tearing/cutting/scraping food
 Herbivores – Sharp anterior teeth for clipping, flat posterior teeth
for chewing/crushing food
 Omnivores – Combination of the two; flat posterior teeth, sharp
and pointed anterior teeth
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The System
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1. Mouth
2. Esophagus
3. Stomach
4. Small Intestine
5. Large Intestine
6.Anus
7. Uhhhh…
8. Pancreas
9. This guy can’t count
10. Liver
http://www.youtube.com/watch?v=sCn5uvvc3WE
Organs of the Digestive System
 Mouth/Oral Cavity
 Beginning of the digestive tract
 Saliva Amylase breaks down starch into maltose
 When food (bolus) is swallowed, the soft palate of the mouth
closes off the nasopharynx (The opening of the nasal cavity)
 The epiglottis covers the opening of the Tracheal passage.
Organs of the Digestive System
 Pharynx – Where the Tracheal and Esophageal
passages separate.
 Esophagus – Tubular structure that transports food
into the stomach by way of Peristalsis. Food passes
the Gastroesophageal sphincter
 Stomach – Thick-muscled organ that breaks down
food into Chyme. It contracts vigorously and excretes
enzymes and acids.
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Pepsin – Excreted by the stomach with Hydrochloric acid to
convert protien into peptides.
Organs of the Digestive System
 Small Intestine – A long tubular organ that
facilitates the absorption of nutrients and the
breakdown of fats. Juices from the liver and
pancreas are mixed into the small intestine.
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Maltase – Produced by the small intestine which breaks down
maltose into glucose.
Peptidase - Breaks down peptides into amino acids
Organs of the Digestive System
 Small Intestine (continued)
 The intestine has a large surface area which is increased by
Villi. Nutrients are absorbed through villi.
The Outer layer is composed of columnar epithelial cells. Each cell
is covered in microvilli and contains intestinal enzymes.
 Sugars and amino acids enter the blood stream within the villi.
 Glycerol and fatty acids are absorbed into a lymphatic capillary
after being converted into lipoprotein droplets
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Organs of the Digestive System
 Large Intestine – Long, tubular organ similar to the
small intestine. It absorbs water from what’s left over
of the food to create waste, which is stored until it
can be removed through the anus. No digestion
happens here.
Accessory Organs to Digestion
 Pancreas – Regulates glucose in the blood and
creates enzymes necessary to digestion.
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Pancreatic Amylase - digests starch into maltose in the small
intestine
Trypsin - digests protein into peptides in the small intestine
Lipase – digests fat from fat droplets, that were emulsified in
the small intestine, into glycerol and fatty acids.
Accessory Organs to Digestion
 Liver – Large gland that filters blood, stores iron and
vitamins, helps maintain glucose in the blood, and
creates bile for digestion in the small intestine.
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Bile – Emulsifies fat and breaks down proteins.
 Appendix – Small organ attached to the large
intestine. May serve to fight infection, but is
generally seen as a vestigial organ
 Gallbladder
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Stores bile produced by the liver
Diseases of the Digestive System
 Appendicitis
 Infection of the appendix. Can cause nausea, vomiting, fever,
swelling, and even death if untreated. Can be easily treated and
removed through surgery.
 Irritable Bowel Syndrome
 Digestive distress caused by stress or an irregular diet. Can
cause pain and discomfort, but doesn’t worsen
 Barrett’s Esophagus
 Damaged esophageal cells (caused by excessive acid damage or
infection) mutate into columnar cells. This causes strictures in
the esophagus that have to be removed through surgery