Digestive SystemGabriel Tan 1i120Timothy Lee 1i113Elton Ching 1i106

Edgar Foo 1i105Bryan Yan 1i102

Content

•What is digestion and what can be?•What makes up the digestive system?•Myths: Some things you never

knew…

Definition of Digestion

• The catabolic process in the digestive tract where ingested food is converted into simpler, soluble and diffusible substances that can be assimilated by the body.

What food is digestible

• Fats• Carbohydrates• Protein• Amino acids• Food Phenolics

What organs are in the digestive system

• Esophagus•Mouth• Liver• Pancreas• Stomach• Gall Bladder

• Small Intestine• Large Intestine• Rectum

Mouth

• First in Food Tract – Buccal cavity•Mechanical digestion and

mastication (chewing)• Breaks food into smaller substances

to ease digestion in the later parts of the food tract

Esophagus

• Contains MUSCULAR tube- muscle contracts and relaxes to push food down to stomach• Upper part of the oesophagus is under

conscious control until a point when it becomes involuntary.• 4-8 sec - food to travel from mouth to

stomach.

Stomach

• Mechanical digestion (churning of the stomach) – breaks food down & mix with gastric juice • Extra smooth muscles inside

the circular layer of walls aid in performance of complex grinding motions• Gastric Enzymes secreted

by stomach aids digestion

Gall Bladder

• Concentrates Bile:• Bitter, dark green - yellowish brown• Emulsifies fats to facilitate digestion and absorption• Allows for absorption of fat-soluble vitamins• Neutralizes excess acid from

stomach• Alkaline nature also kills harmful

microbes

Pancreas

• Gland located deep in the abdomen• Two functions performed by two different groups

of cells:• Islets of Langerhans: Secrete hormones insulin

and glucagon to maintain optimal level of sugar, glucose, in the blood stream

• Actinar cells: Produces enzymes for food digestion

Liver

• Largest and heaviest internal organ of the body (1.6 kg)• Susceptible to diseases –

Hepatitis A & B, Cancer• Ability to regenerate to

restore function

Liver

• Performs 500 different functions:• Produces bile (stored in gall bladder,

transported by the bile duct), which emulsifies fat

• Produces substances such as urea, amino acids and cholesterol

• Filters blood• Stores vitamins and minerals

Small Intestine

• Absorbs nutrients and minerals + Big• Proteins + peptides = amino acids• Fats = fatty acids + glycerol• Some carbohydrates = simple sugars

a.k.a monosaccharides (e.g. glucose)

Large Intestine

• Second-to-last part of the digestive tract-no more digestion

• Compacts fecal matter, absorbs water (by osmosis), minerals and vitamins.

• Houses over 700 bacteria types (the good kind…)• The large intestine absorbs

Rectum

• Final Destination• Gives you “the desire”

Myths unraveled

•5 things you never knew about the human digestive system…

Myth: Spicy food stomach ulcers

• caused either by infection with a bacterium called Helicobacter pylori (H. pylori) or by use of pain medications such as aspirin

• Spicy foods may aggravate existing ulcers in some people, but they do not cause ulcers.

Myth: Beans and farting

• The main culprit of this gaseous release are dairy products

• As we age and our bodies are less able to absorb the sugar in milk (lactose), causing the gas build-up

Myth: Aging constipation

• Medication for other illnesses can cause constipation

• less likely to be exercising enough, eating well, and taking in sufficient fluids, all of which contribute to constipation.

Myth: Less food stomach shrinkage

• You will reach a certain age when the size of the stomach stops changing. 

• For adults, the only way to shrink the stomach is through surgery. 

• Eating less can only help reset your appetite so it becomes easier and faster to satisfy your hunger

Myth: Thin people = small stomach

• Weight does not determine a person’s stomach size. 

• There are people who have had weight battles for most of their life whose stomachs are smaller than or are the same size as people who are naturally thin.

Interesting Facts

• We eat about 500kg of food per year. 1.7 litres of saliva is produced each day. 

• The small intestine is 3 grown men tall and two fingers wide.

• Every 2 weeks, the human stomach produces a new layer of mucous lining, otherwise the stomach will digest itself

Credits

• Know Your Body - Digestive System http://www.medindia.net/know_ur_body/interesting-body-facts-about-digestive-system.asp#ixzz1WW115CzJ

• http://library.thinkquest.org/J0112205/interesting_facts.htm• http://homepage.mac.com/seisenelem/bodysystems/Digestive/interesting.

html• http://www.biology-online.org/dictionary/Digestion• http://www.worldofmolecules.com/foods/• http://www.webmd.com/digestive-disorders/slideshow-digestive-myths• http://healthy-lifestyle.most-effective-solution.com/2009/08/25/9-stomac

h-myths-and-facts/

THANK YOU

notes

• Carbohydrates. The Dietary Guidelines for Americans 2005 recommend that 45 to 65 percent of total daily calories be from carbohydrates. Foods rich in carbohydrates include bread, potatoes, dried peas and beans, rice, pasta, fruits, and vegetables. Many of these foods contain both starch and fiber.

• The digestible carbohydrates—starch and sugar—are broken into simpler molecules by enzymes in the saliva, in juice produced by the pancreas, and in the lining of the small intestine. Starch is digested in two steps. First, an enzyme in the saliva and pancreatic juice breaks the starch into molecules called maltose. Then an enzyme in the lining of the small intestine splits the maltose into glucose molecules that can be absorbed into the blood. Glucose is carried through the bloodstream to the liver, where it is stored or used to provide energy for the work of the body.

• Sugars are digested in one step. An enzyme in the lining of the small intestine digests sucrose, also known as table sugar, into glucose and fructose, which are absorbed through the intestine into the blood. Milk contains another type of sugar, lactose, which is changed into absorbable molecules by another enzyme in the intestinal lining.

• Fiber is undigestible and moves through the digestive tract without being broken down by enzymes. Many foods contain both soluble and insoluble fiber. Soluble fiber dissolves easily in water and takes on a soft, gel-like texture in the intestines. Insoluble fiber, on the other hand, passes essentially unchanged through the intestines.

• Protein. Foods such as meat, eggs, and beans consist of giant molecules of protein that must be digested by enzymes before they can be used to build and repair body tissues. An enzyme in the juice of the stomach starts the digestion of swallowed protein. Then in the small intestine, several enzymes from the pancreatic juice and the lining of the intestine complete the breakdown of huge protein molecules into small molecules called amino acids. These small molecules can be absorbed through the small intestine into the blood and then be carried to all parts of the body to build the walls and other parts of cells.

notes

• Fats. Fat molecules are a rich source of energy for the body. The first step in digestion of a fat such as butter is to dissolve it into the watery content of the intestine. The bile acids produced by the liver dissolve fat into tiny droplets and allow pancreatic and intestinal enzymes to break the large fat molecules into smaller ones. Some of these small molecules are fatty acids and cholesterol. The bile acids combine with the fatty acids and cholesterol and help these molecules move into the cells of the mucosa. In these cells the small molecules are formed back into large ones, most of which pass into vessels called lymphatics near the intestine. These small vessels carry the reformed fat to the veins of the chest, and the blood carries the fat to storage depots in different parts of the body.

• Vitamins. Another vital part of food that is absorbed through the small intestine are vitamins. The two types of vitamins are classified by the fluid in which they can be dissolved: water-soluble vitamins (all the B vitamins and vitamin C) and fat-soluble vitamins (vitamins A, D, E, and K). Fat-soluble vitamins are stored in the liver and fatty tissue of the body, whereas water-soluble vitamins are not easily stored and excess amounts are flushed out in the urine.

• Water and salt. Most of the material absorbed through the small intestine is water in which salt is dissolved. The salt and water come from the food and liquid you swallow and the juices secreted by the many digestive glands.