1. Digestive and Excretory Systems
Chapter 38: Biology II

2. Food and Energy Why do you need food to live? Food provides ENERGY
Energy is converted by your cells into glucose and ATP

3. Nutrients
Substances in food that supply the energy and raw materials your body uses for growth, repair and maintenance
Water
Carbohydrates
Fats
Proteins
Vitamins
Minerals

4. Water The most important nutrient!
Every cell in the human body needs water
Many of the body’s processes take place in water
Humans need to drink at least a liter of water each day*
*If you eat lots of fruits and veggies, this amount is reduced. Why?

5. Carbohydrates Main source of energy
Simple sugars: monosaccharrides and disaccharides
Found in fruits, honey and sugar cane

6. Carbohydrates
Complex sugars: polysaccharides; complex carbohydrates, starches
Found in grains, potatoes, and vegetables
Broken down into simple sugars
Some foods contain cellulose, a complex carbohydrate

7. Fats
Provide energy and key components in cell membranes, myelin sheaths for neurons, and certain hormones
Fats protect body organs, insulate the body, and store energy
Lipids: important part of a healthy diet
Formed from fatty acids and glycerol
Essential fatty acids are found in vegetable oils
Saturated versus unsaturated

8. Proteins Wide variety of roles in the body
Supply raw materials for growth and repair
Regulatory and transport functions

9. Proteins Polymers of amino acids
Body produces 12 of the 20 amino acids used to make proteins
Remaining 8 come from food: meat, fish, eggs, milk (vegetarians: combination of beans and rice)

10. Vitamins
Organic molecules that help regulate body processes, often working with enzymes
Some are made by bacteria living digestive tract
Most are obtained from food
Fat soluble vs. water soluble

11. Minerals
Inorganic nutrients that the body needs, usually in a small amount to repair or build tissues
Examples: calcium, iron, magnesium

12. Balancing the Diet Food Guide Pyramid New: USDA “My Plate”
You should eat a variety of foods each day, and limit your intake of fatty, sugary foods

13. The Process of Digestion
Alimentary canal: one-way tube that passes through the body
Mouth  pharynx  esophagus  stomach  small intestines  large intestines
Accessory structures: salivary glands, pancreas and the liver

14. The Mouth
Mechanical Digestion: chewing; physical breakdown of large pieces of food into smaller ones

15. The Mouth
Chemical Digestion: saliva; chemical breakdown of food into simpler molecules
Carbohydrate Digestion
Salivary Amylase: enzyme in saliva

16. The Esophagus
Bolus: the clump of chewed food pushed into the esophagus by the tongue and throat
Peristalsis: rhythmic muscular contractions that squeeze food through the esophagus into the stomach
Cardiac sphincter: a thick ring of muscle that closes the esophagus after food has entered the stomach, and prevents food from coming back up

17. The Stomach Large muscular sac
Mechanical Digestion: contractions of its smooth muscles churn and mix the food you swallow

18. The Stomach
Chemical Digestion: lining of the stomach contains gastric glands that release substances that make the stomach very acidic
Protein Digestion
Pepsin: enzyme
HCl: (hydrochloric acid)

19. The Stomach
Ulcers: powerful acids can damage the lining of the stomach
Peptic ulcer: hole in the wall of the stomach usually caused by a bacterium
Chyme: food digested mechanically; after 1-2 hours it is released through the pyloric valve into the small intestines

20. The Small Intestine
Small intestines: place where most chemical digestion takes place
Duodenum: shorter than the other two parts
Jejunum: together with ileum, about 3 m long
Ileum: longest section
Villi: folded projections that increase the SA of the walls of the small intestines; help absorb nutrients

21. The Small Intestine Further Digestion of Carbohydrates and Proteins
Fat Digestion
Lipase
made by pancreas
Bile
made by liver, stored by gallbladder

22. The Pancreas and Liver
Duodenum: first of three parts of the small intestines
At this point, proteins and carbohydrates are only partially digested and lipid digestion has not begun
Chyme mixes with enzymes and fluids from the (1) pancreas (2) liver and (3) duodenum

23. The Pancreas
Gland that produces the hormone insulin that regulates blood sugar
Also produces enzymes that break down:
Carbohydrates (pancreatic amylase)
Proteins (trypsin and chymotrypsin)
Lipids (lipase)
Nucleic Acids

24. The Liver
Liver: produces bile (stored in the gall-bladder and sent to the duodenum through a duct)
Bile: a fluid loaded with lipids and salts; emulsifies fats (separates it into small droplets)

25. Mechanical and Chemical Digestion

26. Major Digestive Enzymes

27. The Large Intestine/Colon
Leaving the small intestines food is basically nutrient-free
Complex organic molecules have been digested and absorbed, leaving water, cellulose and indigestible substances
Large intestines: removes water from the undigested material

28. Appendix Just below the colon
In some animals it digests cellulose by bacteria
Does no job in digestion in humans
Appendicitis: inflamed appendix; needs to be removed!!!

29. The Excretory System
Skin
Lungs
Kidneys

30. The Kidneys
Located on either side of the spinal column near the lower back
Ureter: tube that leaves each kidney, carrying urine to the urinary bladder
Urinary Bladder: saclike organ where urine is stored before being excreted

31. The Kidneys
Renal Artery: pathway for waste-laden blood to enter the kidney
Renal Vein: pathway for clean, filtered blood to leave the kidney and return to circulation

32. The Kidneys
Nephron: small independent blood-filtering unit in the renal cortex of the kidney
Glomerulus: small network of capillaries encased in the upper end of a nephron
Bowman’s Capsule: cup-shaped structure in the upper end of a nephron that encases the glomerulus

33. The Kidneys
Filtration: process by which fluid from the blood filters in to Bowman’s capsule in the kidneys
Reabsorption: process by which most of the material removed from the blood at Bowman’s capsule makes its way back into the blood

35. Control of Kidney Function
Kidneys play an important role in maintaining homeostasis
Regulate the water content of the blood, blood volume, maintain blood pH, and remove waste products from the blood

36. Homeostasis by Machine
Kidneys are the master chemists of the blood supply
If anything goes wrong humans can survive with one kidney
Both damaged? Transplant from a compatible donor or be hooked up to a dialysis machine