1. The Digestive System

2. The Digestive System 4 steps for processing nutrients from food
Ingestion
Digestion
Absorption
Elimination

3. Ingestion & Digestion Ingestion: Eating or drinking
Digestion: the breaking down of food into molecules that are small enough to be absorbed by the body
Mechanical digestion: Chewing and grinding food into smaller pieces, increasing the surface area
Chemical digestion: Breaking chemical bonds of macromolecules (carbs, proteins and lipids) into monomers (sugars, amino acids, glycerol & fatty acids)
Hydrolysis reactions that are carried out by enzymes

4. Absorption & Elimination
Cells absorb small molecules (monomers) allowing them to enter into the circulatory system for immediate use or be transported to storage organs for later use
Elimination:
Removing undigested waste (feces)

5. Digestive System Digestive Tract Accessory Glands & Organs
A.k.a. an alimentary canal (2 openings)
The mouth, pharynx, esophagus, stomach, small intestine, and large intestine
Accessory Glands & Organs
Aid in digestion, but not a part of the digestive tract
Salivary glands, pancreas, liver, gallbladder.
Secrete digestive juices and enzymes into the digestive tract

6. What’s Your Size? Predicted Length (m) Actual Length (m) Mouth 0.15
Pharynx
0.05
Esophagus
0.25
Stomach
Duodenum
0.2
Jejunum
2.8
Ileum
4.2
Large Intestine
1.5
Total ~9

7. Chewed up food is now called a bolus
Mouth
Plays a role in ingestion and digestion
Teeth, tongue, hard palate aid in mechanical digestion
Tongue moves food down to the esophagus
Salivary glands aid in chemical digestion
Release saliva (~1L/day), a watery liquid containing digestive enzymes
Salivary amylase begins to break down starch into smaller carbohydrates
Lubrication
Chewed up food is now called a bolus

8. Esophagus Located behind the trachea
As you swallow, the epiglottis closes over the trachea and the food bolus passes through pharynx into the esophagus
The bolus is pushed through the esophagus by a series of muscle contractions called peristalsis

9. Heart Burn
After food passes into the stomach, the cardiac sphincter closes the esophagus
If the sphincter opens at an inappropriate time, stomach acid can flow back into the esophagus
Esophagus does not have the same protective lining as the stomach

10. I ate too much…I’m STUFFED!
Stomach
Elastic, muscular sac with a protective lining that contains millions of gastric glands
Can ~ 2 L
Mechanical and chemical digestion
I ate too much…I’m STUFFED!

11. Stomach Chemical Digestion:
The hormone, gastrin, stimulates gastric glands to release gastric juice
Hydrochloric acid breaks apart cells and kills bacteria
Enzymes e.g. pepsin
Mucus lubrication and protection
Mechanical Digestion:
Stomach muscles churn
Bolus becomes an acidic, nutrient-rich liquid called chyme

12. Small Intestine
Chyme passes through the pyloric sphincter and enters the small intestine (peristalsis)
Long, narrow tube where digestion is completed and absorption begins
3 parts:
Duodenum
Jejunum
Ileum

13. Duodenum
Bile from the liver and gallbladder are secreted into the duodenum to help with lipid digestion
Pancreas secretes pancreatic juice into the duodenum
Neutralizes acidic chyme
Pancreatic amylase
Trypsin & chymotrypsin (protein digestion)
Pancreatic lipase
Small intestine releases enzymes too

15. Jejunum & Ileum Jejunum Contains more villi, therefore more absorption
Breakdown of remaining polypeptides and carbohydrates
Ileum
Absorption
Push remaining undigested material into the large intestine

16. Large Intestine
Undigested material passes through the sphincter between the ileum and the cecum
Absorption of water and dissolved minerals
Intestinal bacteria produce vitamins
Indigestible material (feces) passes through the rectum to the anus
Anal sphincters help control timing of elimination

17. Increased Surface Area
The small and large intestine are folded to  surface area and therefore  absorption
Within the folds, there are finger-like projections called villi
Lacteal absorbs fats and fat-soluble vitamins
Capillaries absorb glucose, amino acids, minerals and water-soluble vitamins

18. Regulation of Digestive Processes

19. http://www. neok12. com/php/watch. php