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Overview: The Need to FeedFood is taken in, taken apart, and taken up in the process of animal nutrition. In general, animals fall into three categories:Herbivores eat mainly autotrophs (plants and

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Слайд 1Chapter 41
Animal Nutrition

Chapter 41Animal Nutrition

Слайд 2Overview: The Need to Feed
Food is taken in, taken apart,

and taken up in the process of animal nutrition.
In

general, animals fall into three categories:
Herbivores eat mainly autotrophs (plants and algae).
Carnivores eat other animals.
Omnivores regularly consume animals as well as plants or algal matter.
Overview: The Need to FeedFood is taken in, taken apart, and taken up in the process of

Слайд 3An animal’s diet must supply chemical energy, organic molecules, and

essential nutrients
An animal’s diet provides chemical energy, which is converted

into ATP and powers processes in the body.
Animals need a source of organic carbon and organic nitrogen in order to construct organic molecules.
Essential nutrients are required by cells and must be obtained from dietary sources.
An animal’s diet must supply chemical energy, organic molecules, and essential nutrientsAn animal’s diet provides chemical energy,

Слайд 4Essential Nutrients
There are four classes of essential nutrients:
Essential amino acids
Essential

fatty acids
Vitamins
Minerals

Essential NutrientsThere are four classes of essential nutrients:Essential amino acidsEssential fatty acidsVitaminsMinerals

Слайд 5Essential Amino Acids
Animals require 20 amino acids and can synthesize

about half from molecules in their diet.
The remaining amino acids,

the essential amino acids must be obtained from food in preassembled form.
A diet that provides insufficient essential amino acids causes malnutrition called protein deficiency.
Essential Amino AcidsAnimals require 20 amino acids and can synthesize about half from molecules in their diet.The

Слайд 6Meat, eggs, and cheese provide all the essential amino acids

and are thus “complete” proteins.
Most plant proteins are incomplete in

amino acid makeup.
Individuals who eat only plant proteins need to eat specific plant combinations to get all essential amino acids.
Some animals have adaptations that help them through periods when their bodies demand extraordinary amounts of protein.

Meat, eggs, and cheese provide all the essential amino acids and are thus “complete” proteins.Most plant proteins

Слайд 7Essential amino acids from a vegetarian diet
Beans and other legumes
Corn (maize) and

other grains
Lysine
8 Essential amino acids for adults
Tryptophan
Isoleucine
Leucine
Phenylalanine
Threonine
Valine
Methionine

Essential amino acids from a vegetarian dietBeans  and other legumesCorn (maize) and other grainsLysine8 Essential amino

Слайд 8Essential Fatty Acids
Animals can synthesize most of the fatty acids

they need.
The essential fatty acids are certain unsaturated fatty acids

that must be obtained from the diet.
Deficiencies in fatty acids are rare.
Essential Fatty AcidsAnimals can synthesize most of the fatty acids they need.The essential fatty acids are certain

Слайд 9Vitamins
Vitamins are organic molecules required in the diet in small

amounts. Many vitamins function as coenzymes.
13 vitamins essential to

humans have been identified.
Vitamins are grouped into two categories: fat-soluble and water-soluble.
VitaminsVitamins are organic molecules required in the diet in small amounts.  Many vitamins function as coenzymes.13

Слайд 11Minerals
Minerals are simple inorganic nutrients, usually required in small amounts.

Minerals serve a variety of important functions including enzymes cofactors.

MineralsMinerals are simple inorganic nutrients, usually required in small amounts. Minerals serve a variety of important functions

Слайд 13Dietary Deficiencies
Undernourishment is the result of a diet that consistently

supplies less chemical energy than the body requires.
Malnourishment is the

long-term absence from the diet of one or more essential nutrients.
Dietary DeficienciesUndernourishment is the result of a diet that consistently supplies less chemical energy than the body

Слайд 14Undernourishment
An undernourished individual will
Use up stored fat and carbohydrates
Break

down its own proteins
Lose muscle mass
Suffer protein deficiency of the

brain
Die or suffer irreversible damage.
UndernourishmentAn undernourished individual will Use up stored fat and carbohydratesBreak down its own proteinsLose muscle massSuffer protein

Слайд 15Malnourishment
Malnourishment can cause deformities, disease, and death. Malnourishment can be

corrected by changes to a diet.
Insights into human nutrition have

come from epidemiology, the study of human health and disease in populations.
Neural tube defects were found to be the result of a deficiency in folic acid in pregnant mothers.

MalnourishmentMalnourishment can cause deformities, disease, and death. Malnourishment can be corrected by changes to a diet.Insights into

Слайд 16Question: Can diet influence the frequency of birth defects?

Question: Can diet influence the frequency of birth defects?

Слайд 17The main stages of food processing are ingestion, digestion, absorption,

and elimination
Ingestion is the act of eating. There are a

variety of types of eating:
Suspension feeders
Substrate feeders
Fluid feeders
Bulk feeders
The main stages of food processing are ingestion, digestion, absorption, and eliminationIngestion is the act of eating.

Слайд 18Suspension Feeders
Many aquatic animals are suspension feeders, which sift small

food particles from the water.

Suspension FeedersMany aquatic animals are suspension feeders, which sift small food particles from the water.

Слайд 19Humpback whale, a suspension feeder
Baleen

Humpback whale, a suspension feederBaleen

Слайд 20Substrate feeders are animals that live in or on their

food source.
Leaf miner caterpillar, a substrate feeder
Caterpillar

Feces
Substrate feeders are animals that live in or on their food source.Leaf miner caterpillar, a substrate feederCaterpillar

Слайд 21Fluid feeders suck nutrient-rich fluid from a living host.
Mosquito, a

fluid feeder

Fluid feeders suck nutrient-rich fluid from a living host. Mosquito, a fluid feeder

Слайд 22Bulk feeders eat relatively large pieces of food.
Rock python, a

bulk feeder

Bulk feeders eat relatively large pieces of food. Rock python, a bulk feeder

Слайд 23Digestion is the process of breaking food down into soluble

molecules - small enough to absorb.
In chemical digestion, the process

of enzymatic hydrolysis splits bonds in molecules with the addition of water.
Absorption is uptake of nutrients by body cells.
Elimination is the passage of undigested material out of the digestive compartment.

Digestion is the process of breaking food down into soluble molecules - small enough to absorb.In chemical

Слайд 24The four stages of food processing
Ingestion
Digestion

Mechanical & Chemical

Digestion
Absorption
Elimination
Undigested material
Chemical
digestion (enzymatic
hydrolysis)
Nutrient molecules enter body cells
Small molecules
Mechanical digestion
Food
Pieces of food
1
2
3
4

The four stages of food processing IngestionDigestionMechanical & Chemical    DigestionAbsorptionEliminationUndigested materialChemical digestion (enzymatic hydrolysis)Nutrient

Слайд 25Digestive Compartments
Most animals process food in specialized compartments. These compartments

reduce the risk of an animal digesting its own cells

and tissues.
Intracellular digestion, food particles are engulfed by endocytosis and digested within food vacuoles.
Extracellular digestion is the breakdown of food particles outside of cells. It occurs in compartments that are continuous with the outside of the animal’s body.


Digestive CompartmentsMost animals process food in specialized compartments. These compartments reduce the risk of an animal digesting

Слайд 26 Digestion in a hydra
Gastrovascular cavity
Food
Epidermis
Mouth
Tentacles
Gastrodermis

Digestion in a hydra  Gastrovascular cavityFoodEpidermisMouthTentaclesGastrodermis

Слайд 27Animals with simple body plans have a gastrovascular cavity with

only one opening that functions as mouth / anus. This

gastrovascular cavity functions in both digestion and distribution of nutrients.
More complex animals have a digestive tube with two openings, a mouth and an anus.
This one way digestive tube is called a complete digestive tract or an alimentary canal. It can have specialized regions that carry out digestion and absorption in a stepwise, efficient fashion.
Animals with simple body plans have a gastrovascular cavity with only one opening that functions as mouth

Слайд 28 Variation in alimentary canals
Esophagus
Mouth
Pharynx
Crop
Gizzard
Typhlosole
Intestine
Lumen of intestine
Anus
(b) Grasshopper
Foregut
(c) Bird
(a) Earthworm
Midgut
Hindgut
Esophagus
Rectum
Anus
Mouth
Crop
Gastric cecae
Esophagus
Mouth
Crop
Anus
Stomach
Gizzard
Intestine

Variation in alimentary canals EsophagusMouthPharynxCropGizzardTyphlosoleIntestineLumen of intestineAnus(b) GrasshopperForegut(c) Bird(a) EarthwormMidgutHindgutEsophagusRectumAnusMouthCropGastric cecaeEsophagusMouthCropAnusStomachGizzardIntestine

Слайд 29Esophagus
Mouth
Pharynx
Crop -
storage
Gizzard - mechanical digestion

Typhlosole
Increases surface area
for absorption

Intestine

- chemical digestion

Lumen of intestine

Anus

(a) Earthworm

EsophagusMouthPharynxCrop -storageGizzard - mechanical digestion      TyphlosoleIncreases surface area

Слайд 30(b) Grasshopper
Foregut
Mouth
Crop
Gastric cecae
Hydrolytic enzymes produced
Esophagus
Rectum
Anus
Midgut
Hindgut

(b) GrasshopperForegutMouthCropGastric cecaeHydrolytic enzymes producedEsophagusRectumAnusMidgutHindgut

Слайд 31(c) Bird
Stomach
Gizzard
Intestine
Esophagus
Anus
Crop
Mouth

(c) BirdStomachGizzardIntestineEsophagusAnusCropMouth

Слайд 32Organs specialized for sequential stages of food processing form the

mammalian digestive system
The mammalian digestive system consists of an alimentary

canal and accessory glands that secrete digestive juices through ducts.
Mammalian accessory glands are the salivary glands, the pancreas, the liver, and the gallbladder.
Organs specialized for sequential stages of food processing form the mammalian digestive systemThe mammalian digestive system consists

Слайд 33Food is pushed along by peristalsis, rhythmic contractions of smooth

muscles in the wall of the alimentary canal.
Valves called sphincters

regulate the movement of material between compartments.
Food is pushed along by peristalsis, rhythmic contractions of smooth muscles in the wall of the alimentary

Слайд 34human digestive system
Cecum
Anus
Anus
Ascending portion of large intestine
Gall- bladder
Small intestine
Large intestine
Small intestine
Rectum
Pancreas
Liver
Salivary glands
Tongue
Oral cavity
Pharynx
Esophagus
Sphincter
Stomach
pyloric
sphincter
Duodenum of small intestine
Appendix
Liver
Pancreas
Small intestine
Large intestine
Rectum
Stomach
Gall- bladder
A schematic

diagram of the human digestive system
Esophagus
Salivary glands
Mouth

human digestive system CecumAnusAnusAscending portion of large intestineGall- bladderSmall intestineLarge intestineSmall intestineRectumPancreasLiverSalivary glandsTongueOral cavityPharynxEsophagusSphincterStomachpyloricsphincterDuodenum of small intestineAppendixLiverPancreasSmall

Слайд 35Cecum
Anus
Ascending portion of large intestine
Gall- bladder
Small intestine
Large intestine
Small intestine
Rectum
Pancreas
Liver
Salivary glands
Tongue
Oral cavity
Pharynx
Esophagus
Sphincter
Stomach
pyloric
sphincter
Duodenum of small intestine
Appendix

CecumAnusAscending portion of large intestineGall- bladderSmall intestineLarge intestineSmall intestineRectumPancreasLiverSalivary glandsTongueOral cavityPharynxEsophagusSphincterStomachpyloricsphincterDuodenum of small intestineAppendix

Слайд 36 A Schematic Diagram of the Human Digestive System
Anus
Liver
Pancreas
Small intestine
Large intestine
Rectum
Stomach
Gall- bladder
Esophagus
Salivary glands
Mouth

A Schematic Diagram of the  Human Digestive SystemAnusLiverPancreasSmall intestineLarge intestineRectumStomachGall- bladderEsophagusSalivary glandsMouth

Слайд 37The Oral Cavity, Pharynx, and Esophagus
The first stage of digestion

is mechanical and takes place in the oral cavity.
Salivary

glands deliver saliva to lubricate food.
Teeth chew food into smaller particles. This is mechanical digestion that increases the surface area exposed to the enzyme: salivary amylase, initiating breakdown of glucose polymers = carbohydrate digestion.

The Oral Cavity, Pharynx, and EsophagusThe first stage of digestion is mechanical and takes place in the

Слайд 38The tongue shapes food into a bolus and provides help

with swallowing.
The region we call our throat is the pharynx,

a junction that opens to both the esophagus and the trachea (windpipe).
The trachea leads to the lungs.
The tongue shapes food into a bolus and provides help with swallowing.The region we call our throat

Слайд 39The esophagus conducts food from the pharynx down to the

stomach by peristalsis.
Swallowing causes the epiglottis to block entry to

the trachea, and the bolus is guided by the larynx, the upper part of the respiratory tract.
Coughing occurs when the swallowing reflex fails and food or liquids reach the windpipe.
The esophagus conducts food from the pharynx down to the stomach by peristalsis.Swallowing causes the epiglottis to

Слайд 40From mouth to stomach: the swallowing reflex

and peristalsis

Larynx

Trachea

Epiglottis up

Pharynx

Tongue

Glottis

Esophagus

Esophageal sphincter contracted

Food

To stomach

To lungs

From mouth to stomach: the swallowing reflex

Слайд 41From mouth to stomach: the swallowing reflex

and peristalsis

Larynx

Trachea

Epiglottis up

Pharynx

Tongue

Glottis

Esophagus

Esophageal sphincter contracted

Food

To stomach

To lungs

Epiglottis down

Esophageal sphincter relaxed

Glottis up and closed

From mouth to stomach: the swallowing reflex

Слайд 42From mouth to stomach: the swallowing reflex

and peristalsis

Larynx

Trachea

Epiglottis up

Pharynx

Tongue

Glottis

Esophagus

Esophageal sphincter contracted

Food

To stomach

To lungs

Epiglottis down

Esophageal sphincter relaxed

Glottis up and closed

Esophageal sphincter contracted

Sphincter relaxed

Relaxed muscles

Contracted muscles

Relaxed muscles

Stomach

Glottis down and open

From mouth to stomach: the swallowing reflex

Слайд 43Chemical Digestion in the Stomach
The stomach stores food and secretes

gastric juice, which converts a meal to acid chyme.
Gastric juice

is made up of hydrochloric acid and the enzyme pepsin.
Parietal cells secrete hydrogen and chloride ions separately.
Chief cells secrete inactive pepsinogen, which is activated to pepsin when mixed with hydrochloric acid in the stomach.
Mucus protects the stomach lining from gastric juice.

Chemical Digestion in the StomachThe stomach stores food and secretes gastric juice, which converts a meal to

Слайд 44 The stomach and its secretions
Interior surface of stomach
Esophagus
Chief cells
Small intestine
Epithelium
Stomach
Sphincter
Parietal cell
Pepsinogen


and HCl are secreted.
HCl converts pepsinogen to
pepsin.
Pepsin activates more pepsinogen.
Chief cell
Folds of epithelial tissue
Pepsin
Sphincter
Pepsinogen
HCl
H+
Cl–
Parietal

cells

Mucus cells

Gastric gland

1

2

2


3.


3

3

1

5 µm

The stomach and its secretionsInterior surface of stomachEsophagusChief cellsSmall  intestineEpitheliumStomachSphincterParietal cellPepsinogen and HCl are secreted.HCl

Слайд 45Gastric ulcers, lesions in the lining, are caused mainly by

the bacterium Helicobacter pylori.
Coordinated contraction and relaxation of stomach muscle

churn the stomach’s contents.
Sphincters prevent chyme from entering the esophagus and regulate its entry into the small intestine.



Gastric ulcers, lesions in the lining, are caused mainly by the bacterium Helicobacter pylori.Coordinated contraction and relaxation

Слайд 46Digestion in the Small Intestine
The small intestine is the

longest section of the alimentary canal.
It is the major organ

of digestion and absorption.

Digestion in the Small Intestine The small intestine is the longest section of the alimentary canal.It is

Слайд 47Enzymatic hydrolysis in the human digestive system
Oral cavity, pharynx, esophagus
Stomach
Lumen of small

intestine
Epithelium of small intestine (brush border)
Carbohydrate digestion
Polysaccharides
Smaller polysaccharides, maltose
Polysaccharides
Maltose and other disaccharides
Disaccharides
Protein digestion
Nucleic acid digestion
Fat digestion
Proteins
Small

polypeptides

Pepsin

Pancreatic amylases

Salivary amylase

Disaccharidases

Monosaccharides

Small peptides

Amino acids

Amino acids

Polypeptides

Smaller polypeptides

Pancreatic trypsin and chymotrypsin

Pancreatic carboxypeptidase

Dipeptidases, carboxypeptidase, and aminopeptidase

DNA, RNA

Pancreatic nucleases

Fat globules

Nucleotides

Fat droplets

Nucleosides

Nitrogenous bases, sugars, phosphates

Nucleotidases

Nucleosidases and phosphatases

Glycerol, fatty acids, monoglycerides

Bile salts

Pancreatic lipase

(starch, glycogen)

(sucrose, lactose)

Enzymatic hydrolysis in the human digestive system Oral cavity, pharynx, esophagusStomachLumen of  small intestineEpithelium of small

Слайд 48The first portion of the small intestine is the duodenum,

where acid chyme from the stomach mixes with digestive juices

from the pancreas, liver, gallbladder, and the small intestine itself.
The first portion of the small intestine is the duodenum, where acid chyme from the stomach mixes

Слайд 49Hormonal control of digestion
Secretin and CCK
Stomach
Gallbladder
Liver
+
Duodenum
of small intestine
Bile
Gastrin
Secretin
Pancreas
CCK
CCK
Key
Stimulation Inhibition
+

+
+
+

Hormonal control of digestion Secretin and CCKStomachGallbladderLiver+Duodenum of small intestineBileGastrinSecretinPancreasCCKCCKKeyStimulation Inhibition+–+++–

Слайд 50Pancreatic Secretions
The pancreas produces proteases trypsin and chymotrypsin, protein-digesting enzymes

that are activated after entering the duodenum.
Its solution is alkaline

and neutralizes the acidic chyme.
Pancreatic SecretionsThe pancreas produces proteases trypsin and chymotrypsin, protein-digesting enzymes that are activated after entering the duodenum.Its

Слайд 51 Bile Production by the Liver
In the small intestine,

bile aids in digestion and absorption of fats. Bile emulsifies

fat. This is physical NOT chemical digestion. Fat emulsification increases the surface area for chemical digestion of fats by lipases.
Bile is made in the liver and stored in the gallbladder.

Bile Production by the LiverIn the small intestine, bile aids in digestion and absorption of

Слайд 52Secretions of the Small Intestine
The epithelial lining of the duodenum,

called the brush border, produces several digestive enzymes.
Enzymatic digestion is

completed as peristalsis moves the chyme and digestive juices along the small intestine.
Most digestion occurs in the duodenum; the jejunum and ileum function mainly in absorption of nutrients and water.

Secretions of the Small IntestineThe epithelial lining of the duodenum, called the brush border, produces several digestive

Слайд 53Absorption in the Small Intestine - Villi
The small intestine has

villi and microvilli that increase the surface area for absorption.

Villi and microvilli are exposed to the intestinal lumen = space / cavity.
The enormous microvillar surface area greatly increases the rate of nutrient absorption.
Absorption in the Small Intestine - VilliThe small intestine has villi and microvilli that increase the surface

Слайд 54Structure of the small intestine
Muscle layers
Microvilli (brush border) at apical (lumenal) surface
Vein

carrying blood to hepatic portal vein
Villi
Intestinal wall
Key
Nutrient absorption
Large circular folds
Blood capillaries
Epithelial cells
Villi
Lymph vessel
Basal surface
Lacteal
Epithelial cells
Lumen

Structure of the small intestine Muscle layersMicrovilli (brush border) at apical (lumenal) surfaceVein carrying blood to hepatic

Слайд 55Small Intestine
Muscle layers
Vein carrying blood to hepatic portal vein
Villi
Intestinal wall
Key
Nutrient absorption
Large circular folds

Small IntestineMuscle layersVein carrying blood to hepatic portal veinVilliIntestinal wallKeyNutrient absorptionLarge circular folds

Слайд 56Small Intestine
Microvilli (brush border) at apical (lumenal) surface
Key
Nutrient absorption
Blood capillaries
Epithelial cells
Villi
Lymph vessel
Basal surface
Lacteal
Epithelial cells
Lumen

Small IntestineMicrovilli (brush border) at apical (lumenal) surfaceKeyNutrient absorptionBlood capillariesEpithelial cellsVilliLymph vesselBasal  surfaceLactealEpithelial cellsLumen

Слайд 57Each villus contains a network of blood vessels and a

small lymphatic vessel called a lacteal.
After glycerol and fatty acids

are absorbed by epithelial cells, they are recombined into fats within these cells.
These fats are mixed with cholesterol and coated with protein, forming molecules called chylomicrons, which are transported into lacteals.

Each villus contains a network of blood vessels and a small lymphatic vessel called a lacteal.After glycerol

Слайд 58Amino acids and sugars pass through the epithelium of the

small intestine and enter the bloodstream.
Capillaries and veins from the

lacteals converge in the hepatic portal vein and deliver blood to the liver and then on to the heart.
Amino acids and sugars pass through the epithelium of the small intestine and enter the bloodstream.Capillaries and

Слайд 59Absorption in the Large Intestine
The colon of the large intestine

is connected to the small intestine.
The cecum aids in the

fermentation of plant material and connects where the small and large intestines meet.
The human cecum has an extension called the appendix, which plays a very minor role in immunity.
Absorption in the Large IntestineThe colon of the large intestine is connected to the small intestine.The cecum

Слайд 60Digital image of a human colon

Digital image of a human colon

Слайд 61A major function of the colon is water reabsorption, recovering

water that has entered the alimentary canal.
Wastes of the digestive

tract, the feces, become more solid as they move through the colon
Feces pass through the rectum and exit via the anus.

A major function of the colon is water reabsorption, recovering water that has entered the alimentary canal.Wastes

Слайд 62The L.I. colon houses strains of the bacterium Escherichia coli,

some of which produce vitamins ++.
Feces are stored in the

rectum until they can be eliminated.
Two sphincters between the rectum and anus control bowel movements.
The L.I. colon houses strains of the bacterium Escherichia coli, some of which produce vitamins ++.Feces are

Слайд 63Evolutionary adaptations of vertebrate digestive systems correlate with diet
Digestive systems

of vertebrates are variations on a common plan. There are

intriguing adaptations, often related to diet.
Dentition, an animal’s assortment of teeth, is one example of structural variation reflecting diet. Mammals have varying dentition that is adapted to their usual diet.
The teeth of poisonous snakes are modified as fangs for injecting venom. All snakes can unhinge their jaws to swallow prey whole.

Evolutionary adaptations of vertebrate digestive systems correlate with dietDigestive systems of vertebrates are variations on a common

Слайд 64Dentition and diet
Incisors
(c) Omnivore
Molars
(b) Herbivore
(a) Carnivore
Canines
Premolars

Dentition and dietIncisors(c) OmnivoreMolars(b) Herbivore(a) CarnivoreCaninesPremolars

Слайд 65Stomach and Intestinal Adaptations
Herbivores generally have longer alimentary canals than

carnivores, reflecting the longer time needed to digest vegetation.

Stomach and Intestinal AdaptationsHerbivores generally have longer alimentary canals than carnivores, reflecting the longer time needed to

Слайд 66 Alimentary canals of a carnivore (coyote) and herbivore (koala)
Cecum
Small intestine
Herbivore
Carnivore
Colon (large intestine)
Stomach
Small

intestine

Alimentary canals  of a carnivore (coyote)  and herbivore (koala)CecumSmall

Слайд 67Mutualistic ++ Adaptations
Many herbivores have fermentation chambers, where symbiotic microorganisms

++ digest cellulose.
The most elaborate adaptations for an herbivorous diet

have evolved in the animals called ruminants.
Mutualistic ++ AdaptationsMany herbivores have fermentation chambers, where symbiotic microorganisms ++ digest cellulose.The most elaborate adaptations for

Слайд 68 Ruminant digestion
Esophagus
Omasum
Abomasum
Intestine
Rumen
Reticulum
1
2
4
3

Ruminant digestion  EsophagusOmasumAbomasumIntestineRumenReticulum1243

Слайд 69Homeostatic mechanisms contribute to an animal’s energy balance
Food energy balances

the energy from metabolism, activity, and storage.
Nearly all of an

animal’s ATP generation is based on oxidation of energy-rich molecules: carbohydrates, proteins, and fats.
Animals store excess calories primarily as glycogen in the liver and muscles.
Energy is secondarily stored as adipose, or fat, cells.
When fewer calories are taken in than are expended, fuel is taken from storage and oxidized.

Homeostatic mechanisms contribute to an animal’s energy balanceFood energy balances the energy from metabolism, activity, and storage.Nearly

Слайд 70Homeostatic regulation of cellular fuel
Homeostasis: 90 mg glucose/
100 mL blood
Stimulus: Blood glucose level

rises after eating.
Stimulus: Blood glucose level drops below set point.

Homeostatic regulation of cellular fuelHomeostasis: 90 mg glucose/100 mL bloodStimulus: Blood glucose level rises after eating.Stimulus: Blood

Слайд 71Overnourishment and Obesity
Overnourishment causes obesity, which results from excessive intake

of food energy with the excess stored as fat.
Obesity contributes

to diabetes (type 2), cancer of the colon and breasts, heart attacks, and strokes.
The complexity of weight control in humans is evident from studies of the hormone leptin.
Mice that inherit a defect in the gene for an appetite regulation hormone, leptin, become very obese.


Overnourishment and ObesityOvernourishment causes obesity, which results from excessive intake of food energy with the excess stored

Слайд 72Researchers have discovered several of the mechanisms that help regulate

body weight.
Homeostatic mechanisms are feedback circuits that control the body’s

storage and metabolism of fat over the long-term.
Hormones regulate long-term and short-term appetite by affecting a “satiety center” in the brain.
Researchers have discovered several of the mechanisms that help regulate body weight.Homeostatic mechanisms are feedback circuits that

Слайд 73appetite-regulating hormones
Leptin
PYY
Insulin
Ghrelin

appetite-regulating hormones LeptinPYYInsulinGhrelin

Слайд 74Obese mouse with mutant ob gene (left) next to wild-type mouse.
EXPERIMENT
RESULTS

Obese mouse with mutant ob gene (left) next to wild-type mouse.EXPERIMENTRESULTS

Слайд 75Obesity and Evolution
The problem of maintaining weight partly stems from

our evolutionary past, when fat hoarding was a means of

survival.
A species of birds called petrels become obese as chicks; in order to consume enough protein from high-fat food, chicks need to consume more calories than they burn.
Obesity and EvolutionThe problem of maintaining weight partly stems from our evolutionary past, when fat hoarding was

Слайд 76A plump petrel chick

A plump petrel chick

Слайд 77Fat cells from the abdomen of a human
100 µm

Fat cells from the abdomen of a human100 µm

Слайд 78Review
Bloodstream
Veins to heart
Lymphatic system
Small intestine
Esophagus
Stomach
Lipids
Mouth
Hepatic portal vein
Absorbed food (except lipids)
Absorbed water
Secretions from the gastric

glands of the stomach
Secretions from the pancreas and the liver
Liver
Rectum
Anus
Large intestine

ReviewBloodstreamVeins to heartLymphatic systemSmall intestineEsophagusStomachLipidsMouthHepatic portal veinAbsorbed food (except lipids)Absorbed waterSecretions from the gastric glands of the

Слайд 79You should now be able to:
Name the three nutritional needs

that must be met by an animal’s diet.
Describe the four

classes of essential nutrients.
Distinguish among undernourishment, overnourishment, and malnourishment.
Describe the four main stages of food processing.
Distinguish between a complete digestive tract and a gastrovascular cavity.
You should now be able to:Name the three nutritional needs that must be met by an animal’s

Слайд 80Follow a meal through the mammalian digestive system:
List important enzymes

and describe their roles
Compare where and how the major types

of macromolecules are digested and absorbed
Relate variations in dentition with different diets.
Explain where and in what form energy-rich molecules may be stored in the human body.
Follow a meal through the mammalian digestive system:List important enzymes and describe their rolesCompare where and how

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