1. Nelli Astvatsatrian and Mia Stearn Period 5 AP Biology
The Digestive System
Nelli Astvatsatrian and Mia Stearn
Period 5 AP Biology

2. What is it?
The digestive system is a series of organs whose purpose it is to convert food into nutrients that are absorbed into the body and eliminate waste.
It is essential to good health because if the digestive system shuts down, the body cannot be nourished or rid itself of waste.

3. Organs of the Digestive System
Mouth
Throat
Esophagus
Stomach
Small Intestine
Colon (Large Intestine)
Rectum
Anus

5. From the Mouth to the Stomach
The digestive system begins with the mouth where the food enters: 32 teeth grind up the food, three salivary glands produce saliva to soften food while the tongue(a muscle) also helps food to be swallowed.
An enzyme called amylase in saliva begins to break down carbohydrates.
The pharynx, or the throat, connects the mouth to the esophagus.
The esophagus is a muscular tube that connects the throat to the upper gastrointestinal tract of stomach.
Peristalses are muscle contractions in the esophagus that push food to the stomach.
The food ends up in the cardiac sphincter, which closes the end of the esophagus so that the food enters the stomach to be stored.
Food is stored in the stomach for proper digestion with hydrochloric acid.

6. The Small Intestine
After the food has been properly digested in the stomach, it enters the lower gastrointestinal tract through the pyloric sphincter beginning with the small intestine.
Chyme = acidic digested food
Chyme mixes with bile and pancreatic juice to neutralize its acidity.
The duodenum connects the stomach to the jejunum.
The middle of the small intestine is the jejunum, which absorbs some essential nutrients through intestinal mucosa.
Chyme enters the 10-foot long ilium to enter the cecum of the large intestine.

7. The Large Intestine
The small intestine connects to the large intestine through the ileocecal sphincter.
The large intestine absorbs nutrients, water, and vitamins.
Releases nutrients to blood stream
It is “larger: because it is thicker in diameter than the small intestine.
It goes from across the abdomen across the abdominal cavity.
It is made up of four layers: mucosa, which lubricates the innermost part of the large intestine for protection, then a structural support system of nerves, tissue, and blood vessels called submucosa, surrounded by the muscularis that contracts the large intestine, and outermost is the thin protective lubricant layer of serosa.
Beneficial bacteria builds up to mix with the chyme that is passing through the cecum.
These bacteria also digest components of the chyme that could not be digested otherwise.
This is a process of fermentation that releases vitamins.

8. The Large Intestine (cont.)
ascending colon - carries feces to the transverse colon
transverse colon - largest portion that connects ascending and descending colons
descending colon - leads to sigmoid
sigmoid colon - last segment that leads to rectum
rectum - stores feces
anus - ejects feces

9. Digestion: Video

10. MAINTAINING HOMEOSTASIS…
homeostasis = the ability of an organism to maintain stability amidst changes

11. How pH Balance Helps Maintain Homeostasis
A balance of pH in the digestive system is crucial- both acidic and basic pHs are needed
Saliva in the mouth is mildly acidic for breaking down food
The small intestine have to have a high pH (basic) because the enzymes used in digestion cannot work in an acidic environment
The stomach must be highly acidic to start the breakdown process and defend the body against harmful bacteria, etc.

12. How Bacteria Helps Maintain Homeostasis
the average human digestive track has around 500 species of helpful bacteria
helpful bacteria are mostly in the large intestine
help digestion by producing vitamins, forming feces, and shielding against potentially harmful bacteria
When the bacteria population in a digestive tract is thrown off or decimated, the host will notice a change in the pace and quality of digestion
There are many products to help digestion by promoting intestinal microflora's growth

13. How the Liver helps Maintain Homeostasis
food is broken down to nutrient molecules absorbed by villi in small intestine.
digestive tract and pancreas produce digestive enzymes
produces bile, which digests fats
breaks down toxic substances like alcohol and other drugs
produces urea
stores glucose as glycogen after eating
releases glucose in between eating so that the blood glucose concentration remains constant
destroys old blood cells and breaks down hemoglobin

14. Diseases of the Digestive System
Gastroesophageal Reflux Disease (GERD) –Severe “heartburn” (chest pain) caused by reflux of stomach acid into the esophagus
Jaundice – Yellowing of the skin and whites of the eyes from a backup of bile metabolic by-products from the blood into body tissues
Diverticulosis – Small pouches on walls of the large intestine causing discomfort
Cirrhosis – degenerative disease of the liver that develops in alcoholics

15. Diseases of the Digestive System (continued)
Celiac disease- immune system reacts to gluten, damages lining of small intestine, difficult for body to absorb nutrients from food
Inflammatory bowel disease
Crohn’s Disease – a chronic inflammatory disease of the intestine, symptoms of abdominal pain, weight loss, diarrhea
Ulcerative colitis- similar to Crohn’s disease, but it affects only the colon (large intestine).
Irritable bowel syndrome- affects large/small intestine, makes food move through the colon too slowly/ quickly and can lead to diarrhea or constipation
Diseases of the Digestive System (continued)

16. Work Cited
"Body Systems and Homeostasis." Mader. N.p., n.d. Web. 23 May <
"Digestive System Diseases - Des Moines University." Des Moines University Digestive System Diseases Comments. N.p., n.d. Web. 23 May
"For Optimal Print Results, Please Use Internet Explorer, Chrome or Safari. Digestive System Disorders." Digestive System Disorders - AboutKidsHealth. N.p., n.d. Web. 23 May
Zimmermann, By Kim Ann. "Digestive System: Facts, Function & Diseases." LiveScience. TechMedia Network, 22 Apr Web. 24 May

17. "Large Intestine. " InnerBody. N. p. , n. d. Web. 24 May 2015
"Large Intestine." WebMD. WebMD, n.d. Web. 24 May
"What Is the Transverse Colon?" WiseGEEK. N.p., n.d. Web. 24 May
"Rectum." Anatomy, Diagram & Function. N.p., n.d. Web. 26 May
Hall, Christina, and Lauren Fritsky. WiseGeek. Conjecture, n.d. Web. 26 May
Carson, Nacie. "How Does the Digestive System Maintain Homeostasis?" EHow. Demand Media, 28 Oct Web. 26 May <

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