1. Digestion INGESTION DIGESTION PERISTALSIS ABSORPTION DEFECATION
Bio 391
2.9 – 2.11
Answer: QUESTION #1

2. DIGESTION  breakdown of large food molecules into smaller ones Why is it necessary?
CHEMICAL
MECHANICAL
Physical change
Breaking food into smaller parts by ripping, churning
Increases surface area
TEETH  tear & crush
STOMACH  churns
BILE  separates
Gizzard  grinds
Chemical change
Enzymes break bonds of food molecules
Enzymes are made and used by organs
Not always the same
Each enzyme is specific to a type of macromolecule
Carb, fat or protein

3. Where does digestion occur?
INTRACELLULAR
EXTRACELLULAR
Inside the cells
Plants – make own food, process within same cell
Single-celled organisms and simple animals
Hydra
Alimentary canal / GI tract
Most animals, us too
More complex = 1 way
Carnivore vs. herbivores
Venus fly trap
Bread mold

4. Why specialized?

5. Human Anatomy

6. 1. Mouth Physical digestion Chemical digestion Saliva, salivary glands
Starts carbohydrate digestion
Amylase
Starch  complex smaller sugars (maltose)
Saliva’s pH at
Short time in mouth  lots left undigested
Answer Q#2

7. 2. Esophagus & Epiglottis
Esophagus connects mouth to stomach
Peristalsis – wavelike contrxns force food down
Mucus secreted
Epiglottis
“trap door” prevents food “going down the wrong way”

8. 3. Stomach Q4, Q5 Physical digestion Chemical digestion Chyme
Presence of food triggers gastrin release
Hormone, controls juice prodxn
Gastric juice
HCl + mucus + pepsinogen
pH 1.0 – 3.5
Pepsinogen  pepsin once in acid (inactive) (active)
Protein digestion begins
Proteins  polypeptides
Chyme
Mucus lining
Sphincters

9. 4. Small Intestine Q3 All digestion completed, nutrients absorbed
S.I. secretions
Secretin – presence of acid stimulates SI cells to release hormone to pancreas via blood stream
Stimulates pancreas to release NaHCO3
Carbohydrases (ex: maltase)
Carbo digestion completed
Maltose  glucose
Left over starch  glucose
Liver & Gallbladder
Adds bile to the mix
Emulsifies fats

10. S. I. Digestion via pancreatic secretions
Pancreas adds pancreatic juice
Shifts pH from acidic to basic – WHY?
Protein digestion completed
Trypsinogen  trypsin (inactive) (active)
Polypeptides  amino acids
Fat digestion completed
Lipases
Lipids  fatty acid + glycerol
Pancreatic amylase
Carbo’s (maltose)  glucose

11. S.I. Absorption Large surface area Villi & Microvilli
Capillaries enter each

12. 5. Large Intestine Waste condensation Bacterial symbionts
Water absorption
Feces
Bacterial symbionts
Synthesize vitamins
Vitamins absorbed
Also has villi
Diarrhea & constipation
Undigested food leaves through anus
Cellulose, fiber, etc.

13. DISORDERS
Heartburn  stomach acid enters esophagus because of weak cardiac sphincter
Peptic Ulcer  Hole in stomach wall caused by Helicobacter pylori. The pain is caused by the acid.
Diarrhea  Not enough water is absorbed
Constipation  Too much water is absorbed
Diabetes  Glucose cannot enter cells of body very well, therefore glucose cannot get turned into energy!!

14. Diabetes 6th killer in America (and rising)
Pancreas cannot produce insulin or the body does not use it properly
Insulin is a hormone that decreases the amount of sugar in the blood by helping it enter the cells of the body.
Glucose does not enter cells easily, insulin must “act like a butler” and bind to a cell membrane protein to help it in.

15. SUMMARY QUESTIONS What are the 2 types of digestion?
Where does digestion begin?
Where does MOST digestion happen?
Where do nutrients enter the rest the of the body? (i.e.  leave the GI tract)

16. Where does Digestion occur? What Nutrient is Digested?
ORGAN
TYPE OF DIGESTION
NUTRIENT DIGESTED
Mouth
Mechanical
Chemical
Stomach
Small Intestine

17. ENZYMES OF DIGESTION
ENZYME
SITE OF ACTION
SITE of PRODUCTION
NUTRIENT DIGESTED
Amylase
Pepsin
Lipase
Trypsin
Peptidase
Maltase
Sucrase
Lactase

18. OTHER SUBSTANCES INVOVLED IN DIGESTION
SITE OF ACTION
ACTION
Saliva
Moistens Food
Mucus
Esophagus, Stomach
Sm. & Lg. Intestines
Gastrin (H) 
Hydrochloric Acid (HCl)
Helps breakdown food
Kills bacteria
Secretin (H) 
Sodium bicarbonate
Bile
Bacteria