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 are
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 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
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.
.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.
.Pepsin – Excreted by the stomach with Hydrochloric acid to convert protien into
peptides.
.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.
.Maltase – Produced by the small intestine which breaks down maltose into
glucose.
.Peptidase - Breaks down peptides into amino acids
- 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.
.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.
.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.
.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.
.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
- 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.
WORKS CONSULTED
"Appendicitis." OSUMC. Web. 27 Mar. 2012.
<http://medicalcenter.osu.edu/patientcare/healthcare_services/digestive_disorders/appendicitis/P
ages/index.aspx>.
"Barrett’s Esophagus." OSUMC. Web. 27 Mar.
2012.http://medicalcenter.osu.edu/patientcare/healthcare_services/digestive_disorders/barretts_e
sophagus/Pages/index.aspx
"IBS." OSUMC. Web. 27 Mar.
2012.http://medicalcenter.osu.edu/patientcare/healthcare_services/digestive_disorders/irritable_b
owel_syndrome/Pages/index.aspx
"How the Body Works : The Digestive System." Youtube.com. 3 Aug. 2007. Web. 30 Mar. 2012.
http://www.youtube.com/watch?v=sCn5uvvc3WE
.Mader, Sylvia S., and Sylvia S. Mader. Biology: Tenth Edition. New York [NY: McGraw-Hill, 2008.
Print.