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8/8/2019 21 Lectures PPT (1)

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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

PowerPoint Lectures for Biology: Concepts and Connections, Fifth Edition

– Campbell, Reece, Taylor, and Simon

Lectures by Chris Romero

Chapter 21Chapter 21

Nutrition and Digestion

8/8/2019 21 Lectures PPT (1)



Getting Their Fill of Krill• The enormous humpback whale eats small

fishes and crustaceans called krill

– Creates "bubble nets" to corral prey

– Strains food from seawater using largeplates of baleen on the upper jaws

• Whales feed in polar regions during thesummer

• In the fall they migrate to warmer oceans,where they live off body fat and breed

8/8/2019 21 Lectures PPT (1)


8/8/2019 21 Lectures PPT (1)



OBTAINING AND PROCESSING FOOD

21.1 Animals ingest their food in a variety of

ways• All animals eat other organisms

• Animals fall into three dietary categories

– Herbivores: eat plants

– Carnivores: eat other animals

– Omnivores: eat both plants and other animals

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• Animals obtain and ingest their food in avariety of ways

– Suspension feeders

• Extract food particles suspended in the

surrounding water • Examples: whales, clams, tube worms

– Substrate feeders

• Live in or on their food source and eat their way through it

•

Example: caterpillar

8/8/2019 21 Lectures PPT (1)


8/8/2019 21 Lectures PPT (1)


LE 21-1b

Caterpillar Feces

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• Fluid feeders

– Suck nutrient-rich fluids from a living plantor animal host

– Examples: mosquito, aphid

• Bulk feeders

– Must ingest relatively large pieces of food

– Use diverse structures to kill prey, tear off pieces, take mouthfuls

– Examples: birds, mammals

8/8/2019 21 Lectures PPT (1)


8/8/2019 21 Lectures PPT (1)


Video: Lobster Mouth PartsVideo: Lobster Mouth Parts

Video: Shark Eating a SealVideo: Shark Eating a Seal

http://media/21_01D_LobsterMouthParts_SV.mpg


http://media/21_01D_SharkEatSeal_SV.mpg




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21.2 Overview: Food processing occurs in four stages

• Ingestion: the act of eating

• Digestion: the breaking down of food into

molecules small enough for the body to absorb – First mechanically broken into pieces

– Polymers chemically broken down tomonomers by hydrolysis

• All animals need amino acids,monosaccharides, nucleotides, and fattyacids

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LE 21-2b

Polymer Monomers

Protein Amino acids

Protein-digestingenzymes

Carbohydrate-digestingenzymes

Polysaccharide

Disaccharide Monosaccharides

Nucleic acid-digestingenzymes

Nucleic acid Nucleotides

Fat-digestingenzymes

Fat Glycerol Fatty acids

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• Absorption: molecules taken up by cells liningthe digestive tract

– Transported in blood to body cells

– Formed into body's macromolecules,

broken down for energy, or converted to fatfor storage

• Elimination: passage of undigested material

out of the digestive tract

LE 21 2

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LE 21-2a

Piecesof food

Mechanicaldigestion

Food

Chemical digestion

(enzymatichydrolysis)

Smallmolecules

Nutrientmoleculesenter bodycells

Undigestedmaterial

Ingestion Digestion Absorption Elimination

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21.3 Digestion occurs in specializedcompartments

• Most animals have an internal compartment inwhich digestion occurs outside of cells

– Enables eating of food larger than could beingested by phagocytosis

• Cnidarians and flatworms have agastrovascular cavity with a single opening

– Digests and absorbs food

– Undigested materials expelled through

mouth

LE 21 3

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LE 21-3a

Tentacle

Mouth

Food(Daphnia ,a water flea)

Gastrovascular cavity

Soft tissuesdigested

Food particleengulfed

Food particledigested in

food vacuole

Digestiveenzymesreleased froma gland cell

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• Most animals have an alimentary canal runningfrom mouth to anus, with specialized regions – Mouth: entrance for food – Pharynx: throat; receives food

– Esophagus: channels food

– Crop: stores food – Stomach, gizzard: churn and grind food

– Intestine: locus of chemical digestion andabsorption

– Anus: expels food

LE 21 3b

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LE 21-3bMouth

PharynxEsophagus

Crop

Gizzard

Earthworm

Esophagus

Intestine

Mouth

Dorsal fold

Interior of intestineWall of intestine

Stomach

Anus

IntestineGastricpouches

Crop

Grasshopper

Stomach

Gizzard

Anus

Crop

Esophagus

Mouth Intestine

Bird

Anus

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Video: Hydra Eating Daphnia (time lapse)Video: Hydra Eating Daphnia (time lapse)

http://media/21_03A_HydraEating_SV.mpg



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HUMAN DIGESTIVE SYSTEM

21.4 The human digestive system consists of an

alimentary canal and accessory glands• Digestive glands secrete digestive juices that

enter the alimentary canal through ducts

– Salivary glands, pancreas, liver • Muscles propel food through the alimentary

canal by rhythmic contractions (peristalsis)

• Pyloric sphincter regulates passage of food outof stomach and into small intestine

LE 21 4

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LE 21-4

Oralcavity

Tongue

Mouth

Salivaryglands

Pancreas

Liver

Gall-bladder

Smallintestine

Largeintestine

Rectum

Anus

Esophagus

Esophagus

Constriction

Stomach

Pyloricsphincter

Smallintestine

Pharynx

8/8/2019 21 Lectures PPT (1)



21.5 Digestion begins in the oral cavity•

Teeth break up food• Salivary glands secrete saliva

– Saliva protects lining of mouth and lubricates

food – Salivary enzymes begin the hydrolysis of

starch• Tongue

– Forms chewed food into bolus and pushesbolus into the pharynx

LE 21-5

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LE 21-5

Tongue

Salivaryglands

Opening of asalivary gland duct

Teeth

Incisors

Canine

Premolars

Molars

8/8/2019 21 Lectures PPT (1)



21.6 The food and breathing passages both openinto the pharynx

• Most of the time, the esophageal opening isclosed, and air enters the trachea

• Food entering the pharynx triggers theswallowing reflex

– Esophageal sphincter relaxes, letting food

enter

– Larynx closes the tracheal opening

LE 21-6-3

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LE 21 6 3

Tongue

Pharynx

Larynx

Trachea (windpipe)Esophagus

Esophagealsphincter

Epiglottisup

Bolus of food

Sphincter contracted

Larynxup

Sphincter relaxed

Epiglottisdown

Esophagus

Sphincter contracted

Larynxdown

Epiglottisup

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CONNECTION

21.7 The Heimlich maneuver can save lives

• The Heimlich maneuver can dislodge foodfrom the pharynx or trachea during choking

LE 21-7

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LE 21 7

From behind, wrap your arms around the victim’s

waist.Make a fist and place thethumb side of your fistagainst the victim’sabdomen, below the ribcage and above the navel.

Grasp your fist with your

other hand and press intothe victim’s abdomen witha quick upward thrust.

Repeat until object isexpelled.

Follow these 4 steps to clear theblocked airway safely and quickly:

A choking person can’t speak or breathe and needs your help now.Don’t slap the victim’s back. (This could make matters worse.)

save a CHOKING victim

It could save your life!

HEIMLICH MANEUVERHEIMLICH MANEUVER

1.

2.

3.

4.

®

8/8/2019 21 Lectures PPT (1)



21.8 The esophagus squeezes food along to thestomach by peristalsis

• Muscles at the top of the esophagus begin theact of swallowing voluntarily

• Involuntary contractions by smooth muscle inthe rest of the esophagus-peristalsis-movefood into the stomach

LE 21-8

8/8/2019 21 Lectures PPT (1)


Bolus of food

Muscles relax,allowingpassagewayto open

Stomach

Musclescontract,

constrictingpassagewayand pushingbolus down

Musclesrelax

Muscles contract

Muscles relax

Muscles contract

8/8/2019 21 Lectures PPT (1)



21.9 The stomach stores food and breaks it down withacid and enzymes

• The stomach surface is highly folded and dotted withpits leading to gastric glands

• Gastric glands secrete three components of gastric juice

– Mucus lubricates and protects stomach lining

– Pepsinogen, an inactive form of the digestiveenzyme pepsin

– Hydrochloric acid converts pepsinogen to pepsin

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• Secretions of gastric glands are regulated by acombination of nerve signals and hormones – Presence of food stimulates secretion of

gastric juice

– Negative feedback inhibits secretion of gastric juice when stomach contents are tooacidic

• Stomach contents are mixed by churning action

of muscles in stomach wall – Food becomes nutrient-rich acid chyme – Pyloric sphincter helps regulate passage of

acid chyme into small intestine

LE 21-9

8/8/2019 21 Lectures PPT (1)


Lumen(cavity)of stomach

Interior surfaceof stomach

Release of gastric

juice

Foodparticle

Pyloric

sphincter

Stomach

Gastricgland

PitsRelease of juice(mucus, HCl, and

pepsinogen)Epithelium

Mucouscells

Chief cells

Parietal cells

HCl

Pepsinogen Pepsin(activeenzyme)

ColorizedSEM 2,500

CONNECTION

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CONNECTION

21.10 Bacterial infections can cause ulcers

• Mucus normally protects the stomach wall fromthe corrosive effects of digestive juice

• When it fails, gastric ulcers can develop

– Infection by the bacteria Heliobacter piloriresults in localized loss of mucus

– Pepsin and hydrochloric acid destroy cellsfaster than they can regenerate

• The duodenum and esophagus are alsosusceptible to ulcers

LE 21-10

8/8/2019 21 Lectures PPT (1)


Bacteria

Mucouslayer of stomach

Colorized SEM 10,000

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21.11 The small intestine is the major organ of chemical digestion and nutrient absorption

• Most chemical digestion of macromoleculestakes place in the small intestine, aided byother organs

– Pancreas produces alkaline pancreatic juice• Neutralizes the acid chyme• Contains digestive enzymes

– Liver produces bile• Emulsifies fat for attack by enzymes

8/8/2019 21 Lectures PPT (1)



– Gallbladder stores bile

– Acid chyme from stomach mixes with bile,pancreatic juice, and digestive enzymes inthe duodenum of the small intestine

•

All four types of macromolecules are digestedin the small intestine by a variety of enzymes

LE 21-11a

8/8/2019 21 Lectures PPT (1)


Liver Bile

Gall-bladder

Bile

Duodenum of small intestine

Acid chyme

Pancreatic juice

Intestinal enzymes

Stomach

Pancreas

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8/8/2019 21 Lectures PPT (1)



• The small intestine has a huge surface area,resulting from folds and projections

– Fingerlike villi, with surface microvilli,contain lymph vessels and capillaries

•

Nutrients are absorbed into the epithelium andpass to blood or lymph

– Fatty acids and glycerol are first combined

into fats; other nutrients leave unprocessed• Nutrients in blood flow to the liver, where they

are processed and stored

LE 21-11b

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Veinwith blooden route tothe liver

Musclelayers

Lumen

Largecircular folds

Villi

Nutrientabsorption

Lymphvessel

Intestinal wall

Villi

Bloodcapillaries

Epithelialcells

Nutrientabsorption

Lumen of intestine

Epithelial cells

Lymph

Blood

Fats

Aminoacidsand

sugars

Fattyacidsand

glycerol

Nutrient absorptioninto epithelial cells

Microvilli

8/8/2019 21 Lectures PPT (1)



21.12 The large intestine reclaims water andcompacts the feces

• The large intestine, or colon, is about 1.5 mlong, joined to the small intestine by asphincter

– Appendix is a small extension of the cecum

• The main function of the large intestine is toreabsorb water from undigested material

• Feces, the waste products of digestion, arestored in the rectum along with prokaryotes

– E. Coli produce important vitamins

LE 21-12

8/8/2019 21 Lectures PPT (1)


Largeintestine(colon)

Sphincter

Endof smallintestine

Nutrientflow

Appendix

Cecum

Anus

Rectum

Smallintestine

DIETS AND DIGESTIVE ADAPTATIONS

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DIETS AND DIGESTIVE ADAPTATIONS

21.13 Adaptations of vertebrate digestivesystems reflect diet

• Herbivores and omnivores have longer alimentary canals than carnivores

– Allow more time and surface area for digesting plant material

• Most herbivores also have special chambers

containing cellulose-digesting microbes• Some herbivores obtain more nutrients by

eating their feces

LE 21-13a

8/8/2019 21 Lectures PPT (1)


Small

intestineStomach

Cecum

Smallintestine

Colon(largeIntestine)

Carnivore Herbivore

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• Ruminant mammals have an elaborate systemfor digesting cellulose

– Four-chambered stomach containingmicrobes

– Cud-chewing

LE 21-13b

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Intestine Omasum Rumen

Esophagus

ReticulumAbomasumRumen

NUTRITION

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NUTRITION

21.14 Overview: A healthful diet satisfies threeneeds

• A healthy diet provides

– Fuel for an organism's activities

– Raw materials for biosynthesis

– Essential nutrients the animal cannot make

itself

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21.15 Chemical energy powers the body•

Every activity requires fuel in the form of chemical energy• Nutrients are oxidized by cellular metabolism to

generate energy in the form of ATP• The energy content of food is measured in

kilocalories – Basal metabolic rate: number of kilocalories

a resting animal needs to fuel only basicbody functions

• Excess kilocalories are stored as glycogen or fat

8/8/2019 21 Lectures PPT (1)


8/8/2019 21 Lectures PPT (1)



21.16 An animal's diet must supply essential nutrients

•

Essential nutrients are those that an animal mustobtain from its diet

– Essential fatty acids, essential amino acids,vitamins, and minerals

– Animal's cells cannot make them from any rawmaterials

• Undernourishment: chronic deficiency of calories

• Malnourishment: lacking one or more essentialnutrients

CONNECTION

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CONNECTION

21.17 Vegetarians must be sure to obtain alleight essential amino acids

• The eight essential amino acids can beobtained from the proper combination of plantfoods

LE 21-17

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Essentialamino acids

Methionine

Valine

(Histidine)

Threonine

Phenylalanine

Leucine

Isoleucine

Tryptophan

Lysine

Corn

Beans andother legumes

8/8/2019 21 Lectures PPT (1)



21.18 A healthy diet includes 13 vitamins

• A vitamin is an organic nutrient required insmall quantities

– Must be obtained from diet

• Most vitamins function as coenzymes

– Absolutely necessary for healthy bodyfunctioning

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8/8/2019 21 Lectures PPT (1)



21.19 Essential minerals are required for manybody functions

• Minerals are inorganic nutrients required insmall amounts

– Must be obtained from diet

– Play a variety of crucial roles in bodyfunctioning

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8/8/2019 21 Lectures PPT (1)


CONNECTION

8/8/2019 21 Lectures PPT (1)



21.20 Do you need to take vitamin and mineralsupplements?

• A healthy diet usually contains enoughvitamins and minerals to meet the MinimumDietary Allowances

– Quantities are the subject of much debate

– Supplements ensure a sufficient quantity if

they are not obtained through diet• Megadoses may be dangerous

CONNECTION

8/8/2019 21 Lectures PPT (1)



21.21 What do food labels tell us?

• Food labels provide nutritional information

– Ingredients, in order by amount (greatestfirst)

– Energy content (calories)

– Selected nutrients and daily values

• Emphasis on nutrients that are of healthconcern

LE 21-21

8/8/2019 21 Lectures PPT (1)


Ingredients: whole wheat flour,water, high fructose corn syrup,wheat gluten, soybean or canola oil,molasses, yeast, salt, cultured whey,vinegar, soy flour, calcium sulfate(source of calcium).

CONNECTION

8/8/2019 21 Lectures PPT (1)



21.22 Obesity is a human health problem

• The World Health Organization has recognizedobesity as a global health problem

– Contributes to a number of serious diseases

– Caused by sedentary lifestyle, fatteningfoods

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• Researchers have studied the genetic basis of obesity

– Inheritance is one factor

– Many genes code for weight-regulatinghormones

• A defect in the gene for the appetite regulator leptin, produced by adipose cells, causesobesity in mice

•

Function of leptin in humans is not clear • In our feast-or-famine evolutionary past, natural

selection may have favored genes for fatstorage

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8/8/2019 21 Lectures PPT (1)


CONNECTION

8/8/2019 21 Lectures PPT (1)



21.23 What are the health risks and benefits of fad diets?

• The effectiveness and health benefits of anydiet are tied to how weight loss occurs

– Low-carb diets• Quick weight loss

• Lost weight quickly regained

• Reduce intake of vitamins, minerals, andfiber

•

Fatty foods may contribute to disease

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– Low-fat diets

•

Healthy diet requires some fat• Often lack adequate protein and fatty acids

• The body requires a balance of nutrients for good health and long-term weight control

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CONNECTION

8/8/2019 21 Lectures PPT (1)



21.24 Diet can influence cardiovascular diseaseand cancer

• Diet plays an important part in risk for disease

• Cardiovascular disease is linked to diets high

in saturated fats – Found in animal products, hydrogenated

fats

– Trans fats produced by hydrogenated fats

– Correlate with high levels of cholesterol

LE 21-24

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Behavioral

risk factors

• Fatty diet

• Lack of exercise

• Smoking

High blood cholesteroland high blood

pressure

Cardiovascular disease

Unavoidable

risk factors

• Aging

• Familyhistory

• Beingmale

8/8/2019 21 Lectures PPT (1)



• Cholesterol travels through the body in bloodlipoproteins

– Low-density lipoproteins (LDLs) correlatewith blocked blood vessels, high bloodpressure, heart attacks

• Increased by diet high in saturated fats

– High-density lipoproteins (HDLs) may

decrease risk of vessel blockage• Increased by exercise; decreased by

smoking

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• Diet seems to be involved in some forms of cancer

– High levels of dietary fat and low levels of dietary fiber may be linked to cancer

– Antioxidants may help prevent cancer • Help protect cells from damaging free

radicals

8/8/2019 21 Lectures PPT (1)


21 lectures ppt (1)

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