Digestion

Digestive System

• Mouth – teeth, tongue, salivary glands • Esophagus- muscular tube that contracts in waves to move food into the stomach.

• Stomach – a muscular J-shaped organ packed full of gastric glands • Small Intestine – divided into three regions 1)

duodenum 2) jejunum 3) ileum

• Large Intestine- consisting of the caecum, colon, rectum, and anal canal.

Two Types of Digestion

•

Mechanical Digestion –

the initial stage of physically breaking down food into smaller more manageable pieces.

•

Chemical Digestion –

is the separation of food into its molecular components by chemical means.

Mechanical Digestion

• Begins in the mouth with the teeth and tongue manipulating the food into manageable sized pieces • Food is moved down the esophagus in a wave like movement called

Peristalsis.

• http://www.innerbody.com/anim/mouth.ht

ml

Mechanical Digestion

• For the rest of the system Involuntary muscle movements grind food into smaller pieces.

Chemical Digestion

• • Chemical Digestion occurs simultaneously with mechanical digestion.

• When food enters the mouth, saliva is secreted by salivary glands to chemically breakdown food and moisten the food for an easy passage down the esophagus.

Salivary amylase –

is the enzyme to breakdown starch and other complex sugars into a more manageable sugar, maltose (a double sugar).

Chemical cont.

• Food then travels down the esophagus.

• Once in the stomach, harsh hydrochloric acid

Pepsin –

an enzyme to breakdown proteins into smaller peptides, works to chemically breakdown food.

Small Intestine

• The area of enzymatic breakdown of lipids by

Lipase

and carbohydrates by

carbohydrase

.

• ALSO- major site of absorption of nutrients into the blood stream

Small Intestine

Large Intestine

• Final stage of Digestion • Point where water and electrolytes (Sodium and Chloride) are re-absorbed back into the body.

• Waste products at this point are mixed with bacteria and mucus to form feces.

• http://www.whfoods.com/genpage.php?tna

me=faq&dbid=16#digestion • http://www.can do.com/uci/ssi2002/digestivesystem.html

Chemical Digestion & Enzymes

Essential Nutrients

• There are basic raw materials organisms need to make their own structures, perform functions, and obtain energy for survival • There are six (6) Essential Nutrients: – Carbohydrates – Proteins – Vitamins - Fats (Lipids) - minerals - water • Our body functions best when we get the correct portions satisfying a

balanced diet.

Carbohydrates

• Consists of atoms of carbon, hydrogen and oxygen (CHO). Carb’s are broken down to simple sugars during digestion (glucose, fructose, galactose). – Main function is to provide a source of energy – Excess carbohydrates are converted to fat or glycogen and stored.

– Sources would be: sugar, rice, bread, pasta etc…

Fats (Lipids)

• Are made up of fatty acids and glycerol – Main functions include: providing a source of energy, insulating the body from the cold, and protecting the organs from injury.

– Used as the main component in building cell membranes and some hormones.

– They are broken down to fatty acids and glycerol by the digestive system – Sources include: butter, meat, cheese, nuts, eggs

Protein

• They are made up of individual amino acids joined by peptide bonds forming chains of peptides. (there are 8 essential amino acids) – Main functions include: cell growth and repair, enzymes in your body are all proteins, minor energy source.

– Sources include: meat, milk, poultry, fish, eggs, etc…

Vitamins

• Our bodies require small amounts of these in our diets. They act as

coenzymes

(chemicals needed to make enzymes function) • Ex. Vitamin A, B, C, D, E, and K • SEE TABLE 11.1 on Page 358

Minerals

• These are inorganic compounds that your body needs in small amounts.

– Main functions include: helping to build bones and cartilage, enabling certain chemical reactions, and helping to maintain acid-base balance within the body

Water

• The ‘life’ solvent.

• Most chemical reactions in the body require water.

• Main source is food and water.

• Regardless of an organisms food source, nutrients acquired by an organism must be in a form that can readily pass through the organisms cell membrane.

Chemical Digestion

• The chemical breakdown of food occurs ar the molecular level where a water molecules break the bonds of complex compounds through the process of

hydrolysis.

• Hydrolysis does occur naturally but at too slow of a rate. This is where enzymes assist by speeding up the process.

Enzyme action

• Many enzymes end in ‘ase’, and act on a single

substrate

(the item being broken down), and are named using the subtrates name. Lactase  lactose

Three Broad Classes

• Carbohydrases- breakdown carbohydrates • Lipases – breakdown lipids • Proteinases (Proteases) – breakdown proteins

Function

• Enzymes are extremely specific for the job they were designed to do.

– ‘Lock and key fit ‘ analogy • Some work in acidic environments (pepsin), while some like a neutral or alkaline environment.

• High temperatures usually change the shape of the ‘lock’ and prevent them from working.

• Some need coenzymes to function properly (vitamins or minerals)

Overview

• Begin in the mouth where

amylase

breaks starch down to a dissacharide.

• Gastric acid and activated pepsin in the stomach begin to break down proteins. Amylase continues until the low pH destroys it.

• The

chyme

passes into the small intestine where enzymes from the duodenum, pancreas, and liver continue digestion.

Duodenum - busy place

• Secretions from the liver and pancreas are used for digestion in the duodenum.

• The pancreas secretes digestive enzymes and stomach acid-neutralizing bicarbonate. It neutralizes the chyme (stopping the action of pepsin), and continues peptide breakdown.

• The liver produces bile, which is stored in the gall bladder. Bile salts emulsify (surround) fat droplets so they can be absorbed by the intestine.

• Most absorption occurs in the ileum and jejeunum.

Liver and Gall Bladder

• The liver produces bile and helps to detoxify of blood • synthesis of blood proteins • destruction of old erythrocytes • storage of glucose as glycogen • De-amination amino groups and ammonia. (this produces urea, less toxic)

Glycogen-Glucose

• Low glucose levels in the blood cause glucagon to stimulate breakdown of glycogen into glucose. • Insulin helps store glucose and glycogen in the liver • When no glucose or glycogen is available, amino acids are converted into glucose in the liver.

The Large Intestine what to do with left overs!

• The large intestine produces an alkaline mucus that neutralizes acids produced by bacterial metabolism. • Water, salts, and vitamins are absorbed, the remaining contents in the lumen form feces (mostly cellulose, bacteria, bilirubin). • Bacteria in the large intestine, such as E. coli, produce vitamins (including vitamin K) that are absorbed.

Digestive Disorders

Overview

• Problems with the digestive system can range from minor inconveniences (heartburn) to a major impediment to a normal lifestyle (bleeding ulcers) • We will discuss the following 6 digestive disorders.

– 1.

Ulcers

– 2.

Gallstones

– 3.

Ileitis

– 4.

Colitis

– 5.

Anorexia Nervosa

– 6.

Bulimia Nervosa

Ulcers • Are slow healing sores in the linings of the stomach and intestines.

• Causes: – – –

Acids

– Cause breakdown of mucus layer of stomach and intestines

.

Heliobacter pylori

– Acid resistant bacteria that causes mucus production to stop.

Lifestyle

– Stress, smoking, alcohol/beverage consumption • Cures/Treatments range from medications to reduce acid production to an overall change in lifestyle.

Ulcers

Gallstones

• Hard masses that form in the gall bladder. Cholesterol in the bile “precipitates” out as a solid forming crystals.

• Causes: – Obesity – Alcohol – Heredity • Treatments: – Ultrasound (busts up the gall stone so it can pass) – Diet Changes (lower fat content diet – reduce cholesterol) – Surgery (Removal of gall bladder).

Gallstones

Ileitis

• Inflammation of the Ileum causing severe pain. The inflammation causes the intestine to empty often causing diarrhea.

• Causes: – Relatively unknown – Does run in families • Treatments/Cures: – There is no cure. Treatment includes drugs to reduce swelling or surgical removal of affected area

Crohn’s & Colitis

• Inflammation and ulceration of the lining of the Colon, Colitis affects the innermost lining of the colon, where Crohn’s affects the entire thickness of the colon. Both conditions can cause bleeding, diarrhea and abdominal pain.

• Causes: – Relatively unknown – Does run in families • Treatments/Cures: – Again, no cure so treatment includes drugs to reduce swelling and surgical removal of affected area

Anorexia Nervosa

• Eating disorder where a person has a fear of gaining weight so they go on very restrictive diets.

• The person often loses excessive amounts of weight and has a lack of nutrients to the cells of body.

Many complications

Bulimia Nervosa

• Eating disorder where a person has episodes of binge eating followed by “purging” through vomiting or taking laxatives.

• This is very dangerous because it affects several organs. Damage to heart, kidneys, esophagus and teeth are common.