How do we get from this…

…to this.

Digestive System Parts Mouth – chewing, lubrication, digestion Pharynx and Esophagus - swallowing Stomach - some digestion Small intestine – most digestion and absorption (of

water and nutrients) Large intestine – some absorption Colon and Rectum - packaging Liver and Gall Bladder - produces bile - aids in fat

digestion Pancreas - produces many digestive enzymes

Food Processing

Food Processing Most food consists of what

macromolecules? Carbohydrates, lipids, and proteins

Why is food chemically broken down? The macromolecules are too large to pass

through cell membranes They must be broken down into monomers, so

that the organism can make their own polymers

Human Digestion System

Human Digestion: Mouth At sight or smell of food, salivary glands

secrete saliva On part helps protect & lubricate lining of mouth Antibacterial agents – help prevent us from

getting sick Amylase (enzyme) to begin digesting starch

Why do you chew your food? Easier to swallow Expose more surface area to enzymes

Tongue pushes mass of food (bolus) to back of oral cavity & into pharynx

Human Digestion: the epiglottis

How does the epiglottis prevent food from moving into the trachea?

Human Digestion: into the esophagus

Heartburn – nothing to do with your heart

- This organ is a stretchy sack shaped like the letter J. Has lots of fold inside.

- It has three important jobs: temporarily stores the food you've eaten breaks down the food into a liquid mixture (called

CHYME) Begins protein digestion by gastric

juices

The Stomach

Inside the Stomach

Small intestine

Long, narrow, intricately folded and twisted compartment of the digestive tube. All chemical digestion is completed and nutrients are

absorbed through the villi of the lining

Almost 90% of our daily fluid intake is absorbed in the small intestine.

Villi - increase the surface area of the small intestines, thus providing better absorption of materials

Human Digestion: small intestine Protein digestion

Pancreas and small intestine secretes enzymes that break polymer into monomers (amino acids)

Fat digestion Liver and gall bladder secrete enzymes to help

break down fat. Nucleic acid digestion

Pancreas and small intestine secrete enzymes which breakdown DNA & RNA polymers into

Nitrogenous bases, sugars, phosphates

Human Digestion: small intestine Lipid digestion

Lipids reach stomach almost completely undigested

Why? Fats are hydrophobic

Bile salts from gallbladder coat tiny fat droplets that keep them separated from each other

Why is the separation of fats into small droplets beneficial for digestion?

More surface area is exposed, which allows the enzyme to breakdown the fats quickly

Human Digestion: small intestine

Human Digestion: small intestine

Human Digestion: small intestine Capillaries that drain away from the small

intestine converge into larger blood vessels and eventually into a main vessel that leads directly to liver Converts many of nutrients into new

substances the body needs Liver removes excess glucose and stores it as?

Glycogen in liver cells

Blood is then transported to heart, which pumps blood and nutrients to all parts of the body

Human Digestion: large intestine Colon absorbs water –approximately 90% of the 7

liters of fluid that enters the canal a day are reclaimed (most in small intestine)

Remains of undigested food become more solid as water is absorbed Feces

Consists mainly of plant fibers and bacteria Diarrhea occurs when the colon is irritated and is less

effective at reclaiming water Constipation occurs when muscle contractions move the

feces too slowly Colon reabsorbs too much water and feces becomes too

compacted Diet low in plant fiber or lack of exercise

Human Digestion: large intestine

Nutrition There are 3 needs which demand a

healthy diet Fuel to power our bodies Organic raw materials needed to make our own

molecules Essential nutrients that we cannot make

ourselves and must obtain in a prefabricated form

So, what happens when something harmful gets past all the acids and enzymes??You would think with a pH of 0 and nasty

enzymes floating around, your stomach would kill anything you swallow. This is not the case. Some bacteria and protists can survive your stomach’s defenses and cause you misery or worse!!Ex: Salmonella, E.coli, Giardia, campylobacter, amoebic dysentery, botulism, and listeria are a few.

Digestive Homeostasis Disorders

ULCERS – erosion of the surface of the digestive canal

APPENDICITIS – an inflammation of the appendix due to infection

Inflammatory Bowel Disease (IBD) Is an inflammation of the small intestine,

large intestine, and/or the colon. Can have a variety of causes including

Crohn’s and Celiac Diseases Produces constipation, diarrhea, nausea,

vomiting, skin rashes, weight loss or gain, impaired nutrient absorption and a variety of other symptoms.

DiabetesDisease in which the pancreas

does not produce enough insulinBlood sugar is too highCan take insulin injections

Sugar Regulation in bloodBody regulates amount of blood

sugar using hormones Insulin--converts sugar into glycogen (how

animals store glucose) Glucagon--converts glycogen into sugar

Overview - digestion