1. The Digestive System
Group of organs working together to convert food into energy and basic nutrients to feed the body
Carbohydrates, proteins, fats, vitamins, minerals

2. Digestive System – 4 Stages
Description
Location(s) in Human Body
Ingestion
Food enters digestive system
Mouth
Digestion
Mechanical
Chemical
Food is physically broken down into small pieces
Digestive enzymes break food pieces into smaller, microscopic molecules
Mouth, stomach
Mouth, stomach, small intestine
Absorption
Water and digested food enter the bloodstream from digestive system
Small intestine (food), large intestine (water)
Excretion
Undigested food leaves the system in the form of feces
Anus

3. Gastrointestinal Tract
Long tube that begins at the mouth and ends at the anus
Mouth→ Pharynx→ Esophagus→ Stomach→ Small Intestine→ Large Intestine→ Rectum→ Anus
Also called the alimentary canal

4. Accessory Organs
Play a direct role in digestion but are not a part of the GI tract
Salivary Glands (parotid, submandibular, sublingual)
Secrete saliva, which contains enzymes that initiate breakdown of carbohydrates
Liver
Produces bile to help emulsify fats in the small intestine
Gall Bladder
Stores bile that the liver produces
Pancreas
Secrete bicarbonate ions to help buffer acid concentration of chyme
Secretes digestive enzymes

5. Mechanical Digestion Mouth, teeth, tongue, stomach
Food enters the mouth via ingestion
Food is prepared for chemical digestion by chewing, mixing, churning
Tongue pushes food back to prepare for swallowing
Bolus
Mass of food that has been chewed at the point of swallowing

6. Propulsion Process of moving food through the GI tract Swallowing
Peristalsis
Smooth muscle contraction and relaxation
Esophagus, stomach
Sphincter (valves)
Circular muscle that controls movement of food throughout the GI tract

7. Heartburn Faulty sphincter
Gastric juice coming up from stomach causing damage to the esophagus
Causes
Smoking, alcohol, ibuprofen, aspirin, caffeine, large meals
Treatment
Zantac, Gaviscon, Pepcid, Pepto Bismol, Prilosec, Acidopholous
Can Lead to GERD
Gastroesophageal reflux disease

8. Chemical Digestion (Enzymes)
Salivary Glands
Secrete amylase – breakdown carbohydrates
Stomach
Secrete pepsin – breakdown protein
Pancreas
Secrete trypsin – breakdown protein
Secrete lipase – breakdown fat
Small Intestine
Secrete lactase – breakdown lactose

9. Stomach Bolus enters the stomach through the esophageal sphincter
Gastric juice
HCl – kills or inhibits bacteria and provides acidic pH of 2
Enzymes – chemical digestion
Mucus – protects lining of stomach from acidic environment
Bolus is converted into chyme by gastric juice

10. Helicobacter pylori Bacteria that is found in the stomach
Causes gastritis, gastric ulcers by preventing mucus from forming
Also linked to stomach cancers

11. Small Intestine Site of nutrient absorption
Villi – increase surface area for absorption
Fingerlike projections that protrude from small intestine
Each villi contain a network of capillaries and microvilli
Nutrients are transported into capillaries via diffusion
Mesenteric arteries supply blood to small intestine

12. Large Intestine Absorbs water from remaining indigestible food matter
Transmits waste matter from body
Houses over 700 species of bacteria
Digest polysaccharides
Produce vitamin K and biotin (B vitamin)

13. Excretory System (Kidneys)
Removes waste
Balances blood pH
Maintain body’s water balance
Blood is supplied to kidney via renal artery
Blood re-enters circulatory system via renal vein

14. Nephrons Functional unit of the kidney (~1 000 000 per kidney)
Regulate water balance
Conduct excretion

15. Urinary Bladder
Renal pelvis connects the kidney to the ureter which fills the bladder
Holds ~300mL-400mL of urine before exiting the urethra

16. Filtration Fluid and dissolved substances enter the nephron from blood
Smaller molecules pass through
Blood, platelets stay in bloodstream
1400L of blood pass through kidneys every day
~1.5L is excreted as urine daily

17. Reabsorption
Water, glucose, some ions (Na⁺, Cl⁻) and other useful substances return to blood from nephron
Active and Passive transport across membrane

18. Secretion
Toxins and unwanted ions (H⁺) are secreted from the blood and into nephron for removal as urine

19. Kidney Stones Small, hard deposits that form inside the kidney
Crystallization of calcium when urine becomes supersaturated
Symptoms
Excruciating pain, nausea, vomiting
Causes
Dehydration, high protein diet, refined sugars
Treatment
Pass through urinary tract
Ureteroscopy

20. Renal Dialysis
Process used to remove waste and excess water from the blood
Artificial replacement for people who experience kidney failure
Works on principles of diffusion across a semi-permeable membrane

21. Insufficient, excessive, or imbalanced consumption of nutrients
Gravest single threat to global public health
Iodine
used to produce hormones that regulate thyroid gland
Deficiency
Impaired mental abilities
Goiter – swelling of thyroid
Vitamin A
Immune system uses to help fight infection
Impaired vision
Zinc
Healing of wounds, growth and repair of tissue, metabolism of macromolecules, alcohol
Retarded growth, recurrent infections
Malnutrition