1. Digestive System

2. Food Processing Food is processed in 4 stages: Ingestion Digestion
Absorption
Elimination

3. Digestion
Digestion: the process that breaks down food into small molecules so they can be absorbed and move into the blood
2 types:
Mechanical: when food is chewed, mixed, and churned
Chemical: chemical reactions break down large molecules into smaller ones

4. Chemical Digestion Made possible through enzymes
Enzyme: protein that speeds up the rate of a chemical reaction in the body
Reduce the amount of energy needed for chemical reactions to begin
Aid with chemical digestion without being used up

5. Enzyme Examples
Amylase (produced by glands near mouth) speeds up breaking down complex carbs into simple carbs
Pepsin in stomach aids with chemical reactions that break down proteins
Enzymes in small intestine aid in breaking down proteins into amino acids
Pancreas releases enzymes into small intestine to help break down sugars and fats

6. Digestive System
2 types of organs: digestive tract and accessory organs
Digestive tract: organs that food passes through
Mouth, esophagus, stomach, small intestine, large intestine, rectum, anus
Accessory organs: food doesn’t pass through them but they are essential for digestion
Tongue, teeth, salivary glands, liver, gallbladder, pancreas

7. The Mouth Mechanical digestion: Chemical digestion:
Chew food with your teeth
Mix food with your tongue
Chemical digestion:
Salivary glands release saliva, which mixes with food
Enzyme in saliva begins to break down starch into sugar
Food is swallowed and ingestion is complete

8. The Esophagus
Epiglottis covers windpipe to ensure food enters esophagus and prevent choking
Esophagus: muscular tube about 25 cm long
Peristalsis moves food down esophagus
Peristalsis: waves of muscular contractions that move food through the digestive system
No digestion (mechanical or chemical) takes place

9. The Stomach Mechanical digestion: Chemical digestion:
Peristalsis causes food to mix
Chemical digestion:
Strong digestive solutions such as hydrochloric acid mix with food to break it down
Pepsin works with hydrochloric acid to digest protein

10. The Stomach Mucus makes food slippery and protects stomach from acid
Takes 2-4 hours for food to move through stomach and change into thin, watery liquid called chyme
Chyme then enters small intestine

11. The Small Intestine
Most digestion takes place in the first part of the small intestine, called the duodenum
Mechanical digestion:
Peristalsis continues to mix chyme
Chemical digestion:
Bile from liver breaks up large fat particles
Digestive solution from pancreas containing enzymes and bicarbonate ions aids digestion of carbohydrates, proteins, and fats
Bicarbonate ions neutralize stomach acid that is mixed with chyme

12. The Small Intestine Entire small intestine is 4-7m long
Villi increase surface area and allow absorption of nutrients to take place
Villi: fingerlike projections covering walls of the small intestine
Gives nutrients more places to be absorbed
Peristalsis moves undigested and unabsorbed materials into large intestine

13. The Large Intestine Main job: absorb water from remaining chyme
Helps maintain homeostasis in body
Homeostasis: regulation of an organism’s internal, life-maintaining conditions
Peristalsis slows down here – chyme may stay for as long as 3 days
Remaining undigested materials become solid
Rectum (last section of large intestine) and anus control release of solid waste as feces

14. Accessory Organs Tongue Teeth Salivary glands Liver Gallbladder
Pancreas

15. Accessory Organs in the Mouth
Tongue: moves food around (mechanical digestion)
Teeth: chew food into smaller parts that can be swallowed (mechanical digestion)
Salivary glands: produce saliva containing enzymes that help with the beginning of chemical digestion
Ex: saliva contains amylase, which breaks down starch into simpler carbohydrates

16. The Liver
Largest solid organ in the body and largest gland in the body
Gland: part of the body that makes and secretes (releases) a substance
Liver is a gland because it makes and secretes bile, a fluid that aids digestion and transports fats and waste
Liver releases bile into small intestine, and bile helps with digestion of fat and fat-soluble vitamins (A, D, E, K)

17. The Liver Also helps store some fats and carbohydrates
Eliminates harmful chemicals produced by the body, such as bilirubin
Bilirubin: harmful substance produced by the breakdown of red blood cells
Handles detox and removal of alcohol, drugs, and other toxins

18. The Gallbladder
Gallbladder: small organ located just below liver that stores bile secreted by the liver
Transports bile from liver to small intestine
You can live without a gallbladder
Surgery can connect liver directly to small intestine, and a steady stream of less-concentrated bile will flow directly from liver to duodenum
Less efficient but will still work

19. The Pancreas
Pancreas: produces hormones that aid in digestion, such as insulin
Insulin: hormone that regulates the amount of glucose (sugar) in the bloodstream and helps break down glucose into usable energy
Diabetes: pancreas no longer produces insulin

20. The Appendix Contains large numbers of B-cells and T-cells
“Reboots” the digestive system by ensuring it has the bacteria needed to protect the body from harmful food
Aids the immune system
You can survive without it