The Gastrointestinal System  and its functions

Retrieved from Images from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates and WH Freeman .

The human digestive system

Click icon to add picture

Functions of Digestive System.

The mechanical and chemical breakdown of food .

Absorption of digested nutrients.Supplying essential nutrients to fuel the other organs and body system.

 

  Movement: propels food through the digestive

system Secretion: release of digestive juices in response to

a specific stimulus Digestion: breakdown of food into molecular

components small enough to cross the plasma membrane

Absorption: passage of the molecules into the body's interior and their passage throughout the body

Elimination: removal of undigested food and wastes

Stages in the Digestive Process

The Gastrointestinal Tract Organs

The Mouth The Pharynx and

Esophagus The Stomach and

Small Intestine The Colon,

Rectum, and Anus

Pancreas  Liver  Gallbladder

The GI tract or alimentary canalThe accessory glands and organs

 

Ingestion of food. Propulsion of food and wastes

from the mouth to the anus Secretion of mucus, water

and enzymes Mechanical digestion of food

particles Chemical digestion of food

particles. Absorption of digested food. Elimination of waste products

by defecation.

The Liver, gall bladder and exocrine pancreas all secrete enzymes for the digestion of chyme.

The GI tract or alimentary canal The accessory glands and

organs

The Gl Tract Organs functions

The mouth

The mouth is the beginning of the digestive system.

Chewing and salivation soften, make it easy to swallow.

An enzyme in saliva, ptyaline, converts starches to sugars.

The tongue  rolls the masticated food into a ball, known as bolus and pushes it to the posterior end of the mouth into the pharynx.

Retrieved from Image from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates and WH Freeman .

 Structure of the throat and the mechanics of swallowing. 

The Pharynx and Esophagus

The esophagus is a muscular tube connecting the pharynx to the stomach that is part of the upper gastrointestinal tract.

Mucus moistens food and lubricates the esophagus. Bicarbonate ions in saliva neutralize the acids in foods.

Swallowing moves food from the mouth through the pharynx into the esophagus and peristaltic waves propel  food to the stomach.

The Stomach

a hollow organ, or "container, "holding food, it serves as the mixer and grinder of food.

Secretes acid and powerful enzymes that continue the process of breaking the food down and changing it to a consistency of liquid or paste.

Small Intestine

Made up of three segments -- the duodenum, jejunum, and ileum 

the 'work horse' of digestion, as this is where most nutrients are absorbed. Peristalsis moving food through and mixing it up with the digestive secretions from the pancreas and liver, including bile.

Carbohydrates, lipids and proteins are broken down and digested.

Large Intestine

made up of the ascending (right) colon, the transverse (across) colon, the descending (left) colon and the sigmoid colon.

is responsible for processing waste so that defecation (excretion of waste) is easy and convenient.

 absorb water and mineral salts from the digested food

 Rectum, and Anus 

the rectum is to receive waste material or feces from where the sigmoid colon is stored, until it is excreted out of the body via the anus.

Stool is stored in the sigmoid (S-shaped) colon until a "mass movement" empties it into the rectum, usually once or twice a day.

Accessory Digestive Organs

Liver :chemical "factory”  the raw materials absorbed by the intestine. second largest organ. Weighs around 3 pounds.

make and secrete bile. detoxifies potentially harmful chemicals.

It breaks down and secretes many drugs. Gallbladder  a storage sac for excess

bile, and then releases it into the duodenum to help absorb and digest fats.

Retrieved from  Images from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates and WH Freeman

The liver and associated organs

Accessory Digestive Organs

Pancreas : the chief factory for digestive enzymes that are secreted into the duodenum. These enzymes break down protein, fats, and carbohydrates.

more than 1000 ml of digestive enzymes daily.

production of several hormones, such as glucagon and insulin.

  Retrieved from Images from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates and WH Freeman

The liver and associated organs

Regulation of Appetite

The hypothalamus in the brain has two centers controlling hunger.

 the appetite center. the satiety center.

Regulation of Appetite

The presence of protein in the stomach stimulates secretion of gastrin , which causes increased stomach acid secretion and mobility of the digestive tract to move food.

Food passing into the duodenum causes the production of secretin, which  promotes release of alkaline secretions from the pancreas, stops further passage of food into the intestine until the acid is neutralized.

Cholecystokinin (CCK) is released from intestinal epithelium in response to fats, and causes the release of bile from the gall bladder and lipase (a fat digesting enzyme) from the pancreas.

 

Retrieved from Images.search.yahoo.com/images/view

Structures and functions of Gastrointestinal tract.

References

McCance, K.L., Heather, S.E., Brasher, V.L., & Rote, N.S. (Eds.). (2006). Structure and Function of Digestive System.  Pathophysiology: The Biologic Basis for Diseases in Adults and Children (5th ed.). St. Louis, MO: Elsevier Mosby.

Margaret Eckman, Debra Share(Eds.) (2013).Gastrointestinal System. Pathophysiology made Incredibly Easy (5thed.) Wolters Kluwer, Lippincott Williams & Wilkins

References

Digestive system. Retrieved from  http://www.webmd.com

Digestive system .Retrieved from http://www.buzzle.com/articles/digestive-system-fuction

Digestive system. Retrieved from http://www.cchs.net/health/healthinfo/docs/1600/1699.asp?index=7041function.html

Digestive system. Retrieved from http://www.estrellamountain.edu/facutly/farebee/biobk/BioBook DIGEST.html