1. Digestive System Digestive System
Function: to breakdown food for energy and to absorb nutrients.
Components: see drawing
Maintains homeostasis: allows nutrients and energy to be absorbed

2. Digestive System Mouth - Chewing is the first step of digestion.
- Salivary glands around your mouth produce amylase, an enzyme that breaks starch and glycogen into dissacharides.

3. Digestive System Esophagus Moves food into the stomach.
Lower esophageal sphincter prevents food and chemicals from moving up and out of the stomach.

4. Digestive System Stomach
Pouch-like organ with about a 1 Liter capacity
Filled with gastric juice, a very acidic fluid containing hydrochloric acid (HCl)
HCl activates digestive enzymes, such as pepsin, to help break down proteins.
Muscles churn food to help break it down.

5. Digestive System Pancreas
Secretes pancreatic juice, which digests fats, proteins, and carbohydrates
Creates insulin, which helps cells absorb glucose

6. Digestive System Liver Creates bile, which help break down fats
Maintains normal concentration of blood glucose
Stores iron and vitamins
Removes toxic substances from the blood

7. Digestive System Small Intestine Completes digestion of nutrients
Secretes chemicals to break down food and carry nutrients in the blood (absorption)

8. Digestive System Large Intestine
Secretes mucus to protect the wall against abrasion
Re-absorbs water and passes along material that was not digested
Contains bacteria to break down cellulose (plant fiber)
Final stage of digestion (exit of waste)

9. Excretory System Excretory System
Function: to eliminate waste products from the body
Components: skin, lungs, see image
Maintains homeostasis: Prevents waste from building up in the body and maintains correct levels of salt.
Kidney

10. Excretory System Kidney
Blood enters through renal arteries and leaves through renal veins.
Ureters (tubes) carry waste (urine) from kidneys to the bladder
Urine contains uric acid, urea, and salts
Uric acid: nucleic acid breakdown
Urea: amino acid breakdown

11. Excretory System Nephron (in the kidney)
The nephron is the basic structural unit of the kidney
The nephron is a long tubule with blood vessels
The nephron regulates the concentration of water and salt by filtering the blood. What is not needed is excreted as urine.

12. Excretory System Variables that Affect Kidney Function
- Diet: if you eat large amounts of protein, more urea will be produced.
- Weather: on a hot day, a body will retain water for sweating and cooling, so the amount of urine is reduced.
- Hormones: Humans produce a hormone called antidiuretic hormone (ADH). It regulates the amount of urine by controlling the rate of water absorption in the nephron tubules.