Warm Up:

• If a solution has a pH of 4 it is_________• If a solution has a pH of 7 it is __________• If a solution has a pH of 11 it is _________

Digestive System

(Gastrointestinal Tract)

Digestion

• Process of breaking down food into smaller forms which can be absorbed or excreted

• Intracellular digestion: (unicellular) digestion occurs in vacoules inside the cell

• Extracellular digestion: (Multicellular) digestion takes place outside the body cells in organ systems

• Ingestion: consumption of a substance by an organism

• Egestion: removal of undigested food or feces from the gut (solid waste)

• Excretion: removal of wastes from cell’s activities (liquid and gas waste)

Mouth Has three major weapons for starting the

breakdown of food so that our bodies can use it as energy:

• Teeth- responsible for grinding, mashing and chewing the food (mechanical).

• Tongue- main player in swallowing and has power to move and mush the food (mechanical).

• Saliva- mixed with the food to help it continue its journey into the esophagus (chemical).

Mechanical Digestion

• Breaks food into smaller pieces• Surface area increases• Enzymes have more surfaces to work on and

complete break down faster

Salivary Amylase

• Enzyme which breaks down carbohydrates in mouth

• Carbs finish being digested in small intestine

Esophagus

• The esophagus is like a stretchy pipe that's about 10 inches long.

• It connects the mouth to the stomach • Contraction of muscles to

move the food (bolus) through the esophagus= peristalsis

Swallowing• Swallowing

Choking

• In the back of the mouth are two openings.• One is the esophagus, which leads to the stomach;

food goes down this pathway.• The other is the trachea, which is the opening air

must pass through to get to the lungs. • When swallowing occurs, the trachea is covered by a

flap called the epiglottis, which prevents food from entering the lungs.

Stomach• Squeezes and churns the food mixing it with

digestive juices (acids and enzymes) and forms chyme

• Hydrochloric Acid

Proteases

• Enzymes which break down proteins into amino acids are located in the stomach

Ulcers

• small erosion (hole) in the gastrointestinal tract

• The direct cause of peptic ulcers is the destruction of the gastric mucosal lining of the stomach by hydrochloric acid

• Infection with the bacterium Helicobacter pylori is thought to play an important role in causing both gastric ulcers

Acid Reflux• Acid reflux occurs when

the stomach churns up acid or refluxes it into the esophagus, causing a burning sensation in the chest or throat.

• Too much acid can push back through a valve between the stomach and the esophagus

Small Intestine• Named for small diameter• 20 to 25 feet long• As the thick liquid paste

travels through your small intestine, the nutrients (vitamins, minerals, proteins, carbohydrates and fats) from the food can finally pass through the wall of the small intestine into your blood

Villi in small intestine

• IncreaseSurfaceAreaFor AbsorptionMost chemical Digestion Occurs in SI

Emulsification of Fats

Lipases break down smaller particles into glycerol and fatty acids

Accessory Glands

• Pancreas, the liver and the gallbladder help by sending different juices to the first part of the small intestine.

• The pancreas makes juices that help the body digest fats and protein.

• A juice from the liver called bile helps to absorb fats into the bloodstream.

• The gallbladder is like a warehouse for this bile, holding onto extra amounts of it when the body needs it.

Liver

• First place that the nutrients from food go.• Processes the nutrients by filtering out any

harmful substances or wastes.

Cirrhosis

• Causes– Alcoholic liver disease. – Chronic hepatitis B,C, D– Autoimmune– Inherited disease

Gall bladder

• Stores bile• Buildups of bile harden=

gallstones

Large Intestine• ~ 5 feet long• Most of the water that is left in the

liquid mix is absorbed into the blood.

• As the water leaves the mix, the waste that's left gets harder as it moves along, until it becomes a solid.

• Waste then collects in the rectum at the end of the large intestine and finally leaves the body through an opening called the anus.

Roughage

• Indigestible portion of plant foods• Also known as dietary fiber• Keeps digestive system functioning properly

because it moves food along

Appendix

• Colon absorbs too much water and the feces are hard= constipation

• Colon absorbs too little water and feces are soft= diarrhea

• Animated Guide to the Digestive System

How does your body digest food?

• Nutrition

• MovieSource: The Digestive System

• Digestive System Game