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.
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.
Слайд 4Essential Nutrients
There are four classes of essential nutrients:
Essential amino acids
Essential
fatty acids
Vitamins
Minerals
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.
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.
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
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.
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.
Слайд 11Minerals
Minerals are simple inorganic nutrients, usually required in small amounts.
Minerals serve a variety of important functions including enzymes cofactors.
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.
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.
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.
Слайд 16Question: 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
Слайд 18Suspension Feeders
Many aquatic animals are suspension feeders, which sift small
food particles from the water.
Слайд 19Humpback whale, a suspension feeder
Baleen
Слайд 20Substrate feeders are animals that live in or on their
food source.
Leaf miner caterpillar, a substrate feeder
Caterpillar
Feces
Слайд 21Fluid 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
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.
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
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.
Слайд 26
Digestion
in a
hydra
Gastrovascular
cavity
Food
Epidermis
Mouth
Tentacles
Gastrodermis
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.
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
Слайд 29Esophagus
Mouth
Pharynx
Crop -
storage
Gizzard - mechanical digestion
Typhlosole
Increases surface area
for absorption
Intestine
- chemical digestion
Lumen of intestine
Anus
(a) Earthworm
Слайд 30(b) Grasshopper
Foregut
Mouth
Crop
Gastric cecae
Hydrolytic enzymes produced
Esophagus
Rectum
Anus
Midgut
Hindgut
Слайд 31(c) Bird
Stomach
Gizzard
Intestine
Esophagus
Anus
Crop
Mouth
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.
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.
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
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
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
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.
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.
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.
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
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
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
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.
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
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.
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.
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)
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.
Слайд 49Hormonal control of digestion
Secretin
and CCK
Stomach
Gallbladder
Liver
+
Duodenum
of
small intestine
Bile
Gastrin
Secretin
Pancreas
CCK
CCK
Key
Stimulation
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.
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.
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.
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.
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
Слайд 55Small Intestine
Muscle layers
Vein carrying blood
to hepatic portal vein
Villi
Intestinal wall
Key
Nutrient
absorption
Large
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
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.
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.
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.
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.
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.
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.
Слайд 64Dentition and diet
Incisors
(c) Omnivore
Molars
(b) Herbivore
(a) Carnivore
Canines
Premolars
Слайд 65Stomach and Intestinal Adaptations
Herbivores generally have longer alimentary canals than
carnivores, reflecting the longer time needed to digest vegetation.
Слайд 66
Alimentary canals
of a carnivore (coyote)
and herbivore (koala)
Cecum
Small intestine
Herbivore
Carnivore
Colon
(large
intestine)
Stomach
Small
intestine
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.
Слайд 68 Ruminant digestion
Esophagus
Omasum
Abomasum
Intestine
Rumen
Reticulum
1
2
4
3
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.
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.
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.
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.
Слайд 73appetite-regulating hormones
Leptin
PYY
Insulin
Ghrelin
Слайд 74Obese mouse with mutant
ob gene (left) next to wild-type
mouse.
EXPERIMENT
RESULTS
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.
Слайд 77Fat cells from the abdomen of a human
100 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
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.
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.