1. Ch 21 Digestion and Nutrition

2. Ingestion methods….. All animals consume energy Herbivores Carnivores
Omnivores

3. Suspension feeders – particles suspended in water or air (clams, oysters, humpback whale)
Substrate feeders – live in or eat their way through (earthworm, maggot)

4. Fluid Feeders: obtain food by sucking nutrient-rich fluids from a living host
Ex: mosquitoes, ticks, butterflies
Bulk Feeders: ingest large pieces of food
Ex: snake, human

5. 4 stages of Food Processing:
Ingestion  Digestion  Absorbtion  Elimination

6. Some organisms only have one opening, a gastrovascular cavity, they eat and eliminate out of the same opening.
Most have 2 openings, Alimentary canal, made up of a mouth and an anus.

7. Breaking down of Organic Molecules:
Lipids (Fat)  glycerol + fatty acid
Polysaccharide  Monosaccarides
Proteins  Amino acids
Nucleic acids  nucleotides

8. The Human Digestive system consists of an alimentary canal and accessory glands
Glands secrete digestive juices through ducts
Peristalsis: smooth muscle contractions that propel food through the digestive tract
Sphincters: muscle rings that regulate passage of food into and out of the stomach
Nutrient absorption occurs in the small intestine
Water is absorbed in the large intestine

10. Digestion begins in the oral cavity Salivary glands secrete:
glycoprotein: slippery; protection of oral cavity and lubrication of food
Buffers: neutralize food acids
Antibacterial agents to kill bacteria
Amylase: digestive enzyme most active against carbohydrates
Both mechanical and chemical digestion start in the oral cavity
Tongue: used to taste food and to form a bolus for swallowing

12. After swallowing, peristalsis moves food through the esophagus to the stomach
Swallowing process:
Tongue pushes the food into the pharynx
Esophageal sphincter
relaxes
Epiglottis covers larynx
Peristalsis pushes the
food toward the
stomach

14. Stomach stores and breaks down food with acids and enzymes
Chemical digestion - gastric juice which contains mucus, enzymes (pepsin), and HCl (pH~2)
Stomach interior is highly folded
Human stomach lining is fully replaced every three days
Gastrin: hormone stimulating the secretion of gastric juice
Chyme: nutrient rich “broth” formed after digestion of foods in the stomach
Leaves the stomach only a little at a time

15. Pancreas: secretes digestive enzymes and buffer solution
The small intestine is the major organ of chemical digestion and nutrient absorption
3 Parts
Pyloric sphincter 1. Duodenum 2. Jejunum3. illium
Nutrients that result from digestion are absorbed into the blood from the small intestine
Pancreas: secretes digestive enzymes and buffer solution
Liver produces bile to break down fats
Bile is stored in the gallbladder
Most digestion occurs in the duodenum
Nutrient absorption occurs in the jejunum and ileum
Villi and microvilli: fingerlike projections that increase the surface area of the small intestine lining

17. The large intestine reclaims water and compacts the feces
The small intestine empties into the cecum of the large intestine
-The appendix - minor immune fnt. and attaches to the end of the cecum
Large intestine functions:
1. Absorb water resulting in solidification of feces
Inflammation of the lining cells may impair this function and result in diarrhea
2. Absorb vitamins produced by bacteria

19. Rectum, holds feces till elimination through anus.

20. Adaptations of vertebrate digestive systems reflect diet
Carnivores often have large, expandable stomachs to accommodate large and infrequent meals
Herbivores &
omnivores have longer
canals to allow for digestion
and absorption

21. Most herbivores have extra chambers to house digestive microbes
May involved an enlarged cecum

22. Ruminants: four-chambered stomach found in herbivorous mammals
Produces “cud” which is further breakdown of the cellulose in plants.
Chambers contain symbiotic microbes
Digest the microbes along with the nutrients produced

24. Urinary System: Eliminates waste products from the body and maintains fluid/salt balance.

25. - The blood, which carries waste enters the kidneys through the Renal Artery

26. - blood moves through the kidneys, and is fitered by nephrons.

27. Excess salts, water, urea, glucose, and amino acids make urine.
Stored in the medulla in tubes
Blood moves through kidneys 20 times an hour.

28. Urine in kidneys  Ureters (tubes)  bladder  Urethra  toilet

29. Overview: A healthy diet satisfies 3 needs
All animals must obtain:
1. Fuel to power all body activities
2. Organic molecules to build the animal’s molecules
3. Obtain essential nutrients the animal cannot make for itself

30. Chemical energy powers the body
Cellular metabolism produces the body’s energy currency, ATP, by oxidizing organic molecules digested from food
The richest energy source is fat

31. The energy content of foods is measured in kilocalories
Rate of energy consumed by the body is called metabolic rate
Basal metabolic rate: the number of kilocalories a resting animal requires for basic living
Breathing, beating heart, maintain body temperature
Any excess energy is stored as glycogen or fat

32. Diet must supply essential nutrients
Essential nutrients: must be obtained in preassembled form b/c cannot make
minerals
Malnourishment: results of long-term absence of one or more essential nutrients
8 of the 20 amino acids are essential and must be obtained in the diet

34. A healthy diet includes 13 vitamins and many essential minerals
Vitamin: organic nutrient
Helps activate enzymes during Chem Rxns
Ex: Vit. K – helps with blood clotting
Minerals: inorganic nutrients usually required in small amounts
Ex: calcium, phosphorus
You can have to much!!

36. Food Labels

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