1. CHAPTER 21
Nutrition & Digestion

2. Ingestion of Food Omnivore – ingests both plant & animals (humans)
Herbivore – ingests only plants (cattle, deer, many aquatic species)
Carnivore – ingests animals (lions, sharks, hawks, spiders)
Sect 21.1

3. Methods of Ingestion
Sect 21.2
Suspension feeders – extract food particles suspended in water
Substrate feeders – live in or on their food source & eat their way through
Fluid feeders – suck nutrient rich fluids from their living hosts
Bulk feeders – use tentacles, claws, or jaws & teeth to kill & eat their prey

4. Stages of Food Processing
Ingestion–act of eating
Digestion – breaking
down food (polymers)
into molecules
(monomers) small
enough for the body
to absorb

6. 3. Absorption – cells lining the digestive tract take up (absorb) small nutrient molecules
4. Elimination – undigested material
passes out the digestive
tract,…
(a chance to get some
reading done)

7. Human Digestive Tract Oral Cavity Saliva - buffers to protect teeth
- salivary amylase – digestive enzyme that hydrolyzes starch
Sect 21.5

8. Oral Cavity (cont.)
Teeth – cut, smash, grind solid food
- incisors: bite off food
- canines: tear loose a piece of food
- premolars & molars: grind, crush the piece of food
Tongue – used to taste & to manipulate food while we chew – helps shape food into a ball called a bolus

9. Region commonly known as the throat
Pharynx
Sect 21.6
Region commonly known as the throat
An intersection that leads either to the esophagus or trachea
As we swallow, the larynx (voice box) moves upward & tips the epiglottis (flap of cartilage) over the opening of the trachea

10. Heimlich Maneuver

11. Esophagus Conducts food from the pharynx down to the stomach
Sect 21.8
Esophagus
Conducts food from the pharynx down to the stomach
Peristalsis – wavelike contraction of the smooth muscles of the digestive tract that squeezes the bolus down to the stomach (sect 21.4)

12. Stomach
Sect 21.9
Highly elastic and can stretch to accommodate about 2 L of food & liquid
Rugae are ridges or folds in lining to allow for expansion
Gastric glands - release gastric juice (breakdown of protein begins)

13. Gastric Juice Contents
Mucus – coats & lubricates stomach lining
HCl – acid that breaks apart the food
Pepsinogen – inactive form of the enzyme pepsin
- HCl converts pepsinogen into pepsin (pepsin breaks down proteins into smaller chains)

14. Stomach (cont.)
Contraction of the muscles in stomach wall aid chemical digestion
- contents of stomach are churned every 20 seconds
- mixture is called acid chyme

15. Sphincter Valves on Stomach
Cardiac sphincter is at the top of the stomach
Prevents backflow into esophagus
Pyloric sphincter is at the bottom of the stomach
Regulates passage of chyme into small intestine

16. Stomach (cont.) Takes about 2-6 hours to empty the stomach of a meal
Mucus coats stomach & protects it from the corrosive effects of digestive juices

17. Stomach Ulcers
Gastric ulcers are open sores that develop on stomach wall
Some ulcers develop from too much pepsin &/or acid, or too little mucus
Some ulcers develop from bacterial infections that cause a loss of mucus & damage the stomach lining
Sect 21.10

19. Small Intestine
Most of the chemical digestion of macromolecules in food take place
Nutrients are absorbed into the blood
Sect 21.11

20. Pancreas produces digestive enzymes & an alkaline solution rich in
bicarbonate

21. Liver performs
wide variety of
functions:
-bile salts that
make fat more
susceptible to
enzyme attack
-gallbladder
stores bile until
it is needed
LIVER

22. Parts of the Small Intestine
DUODENUM
-1st 25 cm
-Where acid chyme
mixes w/bile and
digestive enzymes
-Follow along w/
Table on p. 438

23. Carbohydrate Enzymes
Pancreatic amylase – hydrolyzes starch into a disaccharide
Different disaccharidases – are specialized to hydrolyze different disaccharides
- maltase, sucrase, lactase

24. Protein Enzymes
Trypsin & Chymotrypsin – break polypeptides into smaller chains
Carboxypeptidase & Aminopeptidase – splits off one amino acid at a time working opposite ends of the polypeptide
Dipeptidase – hydrolyzes fragments only 2 or 3 amino acids long

25. Nucleic Acid Enzymes
Nucleases – hydrolyze nucleic acids into
their component nucleotides
What are nucleic acids?
What is a nucleotide?

26. Fat Enzymes
Fats are 1st coated w/bile salts to keep them separated from one another - known as emulsification
Lipase then breaks down fat droplets into fatty acids & glycerol

27. Parts of Small Intestine (Jejunum & Ileum)
Specialized in absorbing nutrients,
wrinkles w/in the small intestine give
it a large surface area, wrinkles are
covered by small, fingerlike projections
called villi

28. - each villus has tiny surface projections called microvilli
- microvilli extend into the interior of the intestine
Tiny lymph vessels extend directly into core of the villus along w/the capillaries (lymph vessels & capillaries pick up nutrients)
- known as the lacteal
p. 439

29. Capillaries that drain nutrients away from the villi converge into larger blood vessels, which eventually lead to the liver
the liver converts many nutrients into new substances that the body needs

30. Large Intestines - Colon
-Is about 1.5 m long
& 5 cm in diameter
-connected to small
intestine at a
T-shaped junction
(a sphincter valve
regulates movement)
Sect 21.12

31. One arm of the T is a blind pouch - cecum
- appendix (a small fingerlike projection of the cecum) has a minor contribution to immunity
- appendix is prone to infection itself

32. Function of the colon is to reabsorb water
if water used during digestion is not reclaimed, severe dehydration would result
wastes are called feces
feces are stored in the rectum until they can be eliminated

33. Healthful Diet
Sect 21.15
ATP
energy content in food is measured in Kilocalories (1 kcal = 1000 calories)
BMR (basal metabolic rate)
- about cal a day
- minimal numbers, any activity consumes kcal in addition to BMR

34. Fad diets are often ineffective & harmful
balanced diet is adequate amounts of all nutrients
Recommended Dietary Allowance (RDA) for nutrients - minimal standards
Sect 21.20

35. Essential Nutrients
Sect 21.16
The body cannot make 9 of the 20 amino acids needed to make proteins
- must be obtained from the diet and cannot be stored in excess
- meat & animal by-products (eggs, milk, cheese)

36. Undernourished- deficient calories
Malnourished- missing essential nutrients

37. Vegetarian Diet
- cannot make all aa
- must eat more than 1 type of plant
- beans & corn together

38. Nutrients (cont.)
Most of the required fatty acids are made from simpler molecules
some must be obtained from our diet NOT A PROBLEM!!

39. Nutrients (cont.)
Sect & 21.23
Vitamin - organic nutrient that is essential but required in small amounts
- coenzymes (catalytic functions)
- water soluble vitamins (B, C)
- fat soluble vitamins (A, D, E, K)
Table on p.444

40. Nutrients (cont.) Minerals - chemical elements other than C, H, O, N
Sect 21.19
Nutrients (cont.)
Minerals - chemical elements other than C, H, O, N
ex: Calcium, Iron, Phosphorus, Sodium
Table on p.445

41. choice of diet may reduce the risk of cardiovascular disease & cancer
Sect & 21.24
Food label provide important nutritional information about packaged foods
choice of diet may reduce the risk of cardiovascular disease & cancer
- diets rich in saturated fats high cholesterol cardiovascular disease

42. Cholesterol
Low-density lipoproteins - have a tendency to cause blocked blood vessels & high blood pressure (found in saturated fats)
High-density lipoproteins - may decrease the risk of vessel blockage (found in unsaturated fats)