The Digestive System

Nelli Astvatsatrian and Mia StearnPeriod 5 AP Biology

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.

Organs of the Digestive System

● Mouth

● Throat

● Esophagus

● Stomach

● Small Intestine

● Colon (Large Intestine)

● Rectum

● Anus

https://www.brainpop.com/games/buildabodydigestivesystem/

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.

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.

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.

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

Digestion: Video

MAINTAINING HOMEOSTASIS…

homeostasis = the ability of an organism to maintain stability amidst changes

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.

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

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

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

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 diseaseCrohn’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

Work Cited

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