Chapter 41: Animal Nutrition
1. Why do we eat?- Fuel (chemical energy)- To get organic material for biosynthesis (carbon skeletons)- Essential nutrients (substances that can’t be made from scratch)
2. What are the 4 main feeding mechanisms of animals?- Suspension feeders- Substrate feeder- Fluid feeders - Bulk feeders
Figure 41.2 Four Main Feeding Mechanisms of Animals
Baleen
SUSPENSION FEEDERS
Feces
SUBSTRATE FEEDERS
BULK FEEDERS
FLUID FEEDERS
Caterpillar
Chapter 41: Animal Nutrition
1. Why do we eat?2. What are the 4 main feeding mechanisms of feeding?3. When our bodies need energy, what is the order of fuel usage?
(fat- protein- carbs- )4. How is appetite regulated in the body?
- Hormonessource fcn
- PYY S. intestine suppresses appetite(after meals)
- Insulin pancreas suppresses appetite ↑blood sugar=↑insulin- Ghrelin stomach triggers hunger ↓weight = ↑ghrelin
(+) makes dieting difficult
- Leptin adipose suppresses appetite- ↑ Fat = ↑ leptin = ↓ appetite- ↓ Fat = ↓ leptin = ↑ appetite
1st 2nd 3rd
Figure 41.5 A few of the appetite-regulating hormones
Produced by adipose (fat) tissue, leptin suppresses
appetite as its level increases. When body fat decreases,
leptin levels fall, and appetite increases.
LeptinPYY
Insulin
Ghrelin
Secreted by the stomach wall, ghrelin is one of the signals that triggers feelings of hunger as mealtimes approach. In dieters who lose weight, ghrelin levels increase, which may be one reason it’s so hard to stay on a diet.
The hormone PYY, secreted by the small intestine after meals,
acts as an appetite suppressant that
counters the appetite stimulant ghrelin.
A rise in blood sugar level after a meal stimulates the pancreas to secrete insulin (see Figure 41.3). In addition to its other functions, insulin suppresses appetite by acting on the brain.
Chapter 41: Animal Nutrition
1. Why do we eat?2. What are the 4 main feeding mechanisms of feeding?3. When our bodies need energy, what is the order of fuel usage?
(fat- protein- carbs- )4. How is appetite regulated in the body?
- Hormonessource fcn
- PYY S. intestine suppresses appetite(after meals)
- Insulin pancreas suppresses appetite ↑blood sugar=↑insulin- Ghrelin stomach triggers hunger ↓weight = ↑ghrelin
makes dieting difficult
- Leptin adipose suppresses appetite- ↑ Fat = ↑ leptin = ↓ appetite- ↓ Fat = ↓ leptin = ↑ appetite
5. What happens if there is a mutation in the leptin system?
1st 2nd 3rd
Figure 41.6 A ravenous rodent
Chapter 41: Animal Nutrition
1. Why do we eat?2. What are the 4 main feeding mechanisms of feeding?3. When our bodies need energy, what is the order of fuel usage?4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system?6. What are essential nutrients & what are the 4 classes?
- Nutrients our bodies cannot make- Essential amino acids (8)- Essential fatty acids – certain unsaturated FAs – linoleic acid- Vitamins- Minerals
Figure 41.10 Essential amino acids from a vegetarian diet
Corn (maize)and other grains
Beansand other legumes
Essential amino acids for adults
Methionine
Valine
Threonine
Phenylalanine
Leucine
Isoleucine
Lysine
Tryptophan
Table 41.1 Vitamin Requirements of Humans
Table 41.2 Mineral Requirements of Humans
Chapter 41: Animal Nutrition
1. Why do we eat?2. What are the 4 main feeding mechanisms of feeding?3. When our bodies need energy, what is the order of fuel usage?4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system?6. What are essential nutrients & what are the 4 classes?
- Nutrients our bodies cannot make- Essential amino acids (8)- Essential fatty acids – certain unsaturated FAs – linoleic acid- Vitamins- Minerals
7. What is the difference between malnourished & undernourished?- Under – get all essentials…just not enough- Mal – missing some essentials
8. How is food processed?
Figure 41.12 The four stages of food processing
Piecesof food
Smallmolecules
Mechanicaldigestion
Food
Chemical digestion(enzymatic hydrolysis)
Nutrient moleculesenter body cells
Undigested material
INGESTION1 DIGESTION2 ELIMINATION4ABSORPTION3
Chapter 41: Animal Nutrition
1. Why do we eat?2. What are the 4 main feeding mechanisms of feeding?3. When our bodies need energy, what is the order of fuel usage?4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system?6. What are essential nutrient & what are the 4 classes?7. What is the difference between malnourished & undernourished?8. How is food processed?9. What is the path that food takes through us?
Mouthesophagusstomachsmall intestinelarge intestinerectumtoilet
IIeumof small intestine Duodenum of
small intestine
Appendix
Cecum
Ascendingportion of large intestine
Anus
Small intestine
Large intestine
Rectum
Liver
Gall-bladder
Tongue
Oral cavity
PharynxEsophagus
Stomach
Pyloricsphincter
Cardiacorifice
Mouth
Esophagus
Salivaryglands
Stomach
LiverPancreas
Gall-bladder
Large intestines
Small intestines
RectumAnus
Parotid glandSublingual gland
Submandibular gland
Salivaryglands
A schematic diagram of the human digestive system
Figure 41.15 The human digestive system
Pancreas
Chapter 41: Animal Nutrition
1. Why do we eat?2. What are the 4 main feeding mechanisms of feeding?3. When our bodies need energy, what is the order of fuel usage?4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system?6. What are essential nutrient & what are the 4 classes?7. What is the difference between malnourished & undernourished?8. How is food processed?9. What is the path that food takes through us?
Mouthesophagusstomachsmall intestinelarge intestinerectumtoilet10. Let’s find out what happens along the way?
Esophagus
Tongue
Pharynx
GlottisLarynx
Trachea
Bolus of food
Epiglottisup
To lungs To stomach
Esophageal sphinctercontracted
Figure 41.16 From mouth to stomach: the swallowing reflex and esophageal peristalsis (layer 1)
Figure 41.16 From mouth to stomach: the swallowing reflex and esophageal peristalsis (layer 2)
Esophagus
Epiglottis down
Tongue
Pharynx
GlottisLarynx
Trachea
Bolus of food
Epiglottisup
To lungs To stomach
Esophageal sphinctercontracted
Glottis upand closed
Esophageal sphincterrelaxed
Figure 41.16 From mouth to stomach: the swallowing reflex and esophageal peristalsis (layer 3)
Esophagus
Epiglottis down
Tongue
Pharynx
GlottisLarynx
Trachea
Bolus of food
Epiglottisup
To lungs To stomach
Esophageal sphinctercontracted
Glottis upand closed
Esophageal sphincterrelaxed
Glottisdown and open
Esophageal sphinctercontracted
Epiglottisup
Relaxedmuscles
Contractedmuscles
Relaxedmuscles
Figure 41.21 Flowchart of enzymatic digestion in the human digestive system
Oral cavity,pharynx,esophagus
Carbohydrate digestion
Polysaccharides(starch, glycogen)
Disaccharides(sucrose, lactose)
Salivary amylase
Smaller polysaccharides,maltose
Stomach
Protein digestion Nucleic acid digestion Fat digestion
ProteinsPepsin
Small polypeptides
Lumen of small intes-tine
Polysaccharides
Pancreatic amylases
Maltose and otherdisaccharides
Epitheliumof smallintestine(brushborder)
Disaccharidases
Monosaccharides
Polypeptides
Pancreatic trypsin andchymotrypsin (These proteasescleave bonds adjacent to certainamino acids.)
Smallerpolypeptides
Pancreatic carboxypeptidase
Amino acids
Small peptides
Dipeptidases, carboxypeptidase, and aminopeptidase (These proteases split off one amino acid at a time, working from opposite ends of a polypeptide.)
Amino acids
DNA, RNA
Pancreaticnucleases
Nucleotides
Nucleotidases
NucleosidesNucleosidasesandphosphatases
Nitrogenous bases,sugars, phosphates
Fat globules (Insoluble inwater, fats aggregate asglobules.)
Bile salts
Fat droplets (A coating ofbile salts prevents small drop-lets from coalescing intolarger globules, increasingexposure to lipase.)
Pancreatic lipase
Glycerol, fattyacids, glycerides
Figure 41.17 The stomach and its secretions
Pepsin (active enzyme)
HCl
Parietal cellChief cell
Stomach
Folds of epithelial tissue
Esophagus
Pyloric sphincter
Epithelium
Pepsinogen
3
2
1
Interior surface of stomach.The interior surface of the
stomach wall is highly folded and dotted with pits leading
into tubular gastric glands.
Gastric gland. The gastric glands have three types of cells
that secrete different components of the gastric juice: mucus cells,
chief cells, and parietal cells.
Mucus cells secrete mucus,which lubricates and protects
the cells lining the stomach.
Chief cells secrete pepsino-gen, an inactive form of the
digestive enzyme pepsin.
Parietal cells secretehydrochloric acid (HCl).
1 Pepsinogen and HCIare secreted into thelumen of the stomach.
2 HCl convertspepsinogen to pepsin.
3 Pepsin then activatesmore pepsinogen,starting a chainreaction. Pepsinbegins the chemicaldigestion of proteins.
5 µm Small
intestine
Cardiac orifice
- stomach epithelium secretes gastric juice- parietal cells secrete HCl & chief cells secrete pepsinogen- pH = 2
Figure 41.19 The duodenum
Liver Bile
Acid chyme
Stomach
Pancreatic juice
Pancreas
Intestinaljuice
Duodenum of small intestine
Gall-bladder
Figure 41.21 Flowchart of enzymatic digestion in the human digestive system
Oral cavity,pharynx,esophagus
Carbohydrate digestion
Polysaccharides(starch, glycogen)
Disaccharides(sucrose, lactose)
Salivary amylase
Smaller polysaccharides,maltose
Stomach
Protein digestion Nucleic acid digestion Fat digestion
ProteinsPepsin
Small polypeptides
Lumen of small intes-tine
Polysaccharides
Pancreatic amylases
Maltose and otherdisaccharides
Epitheliumof smallintestine(brushborder)
Disaccharidases
Monosaccharides
Polypeptides
Pancreatic trypsin andchymotrypsin (These proteasescleave bonds adjacent to certainamino acids.)
Smallerpolypeptides
Pancreatic carboxypeptidase
Amino acids
Small peptides
Dipeptidases, carboxypeptidase, and aminopeptidase (These proteases split off one amino acid at a time, working from opposite ends of a polypeptide.)
Amino acids
DNA, RNA
Pancreaticnucleases
Nucleotides
Nucleotidases
NucleosidesNucleosidasesandphosphatases
Nitrogenous bases,sugars, phosphates
Fat globules (Insoluble inwater, fats aggregate asglobules.)
Bile salts
Fat droplets (A coating ofbile salts prevents small drop-lets from coalescing intolarger globules, increasingexposure to lipase.)
Pancreatic lipase
Glycerol, fattyacids, glycerides
Figure 41.20 Protease activation
PancreasMembrane-boundenteropeptidase
Trypsin
Active proteases
Lumen of duodenum
Inactivetrypsinogen
Other inactiveproteases
Chapter 41: Animal Nutrition
1. Why do we eat?2. What are the 4 main feeding mechanisms of feeding?3. When our bodies need energy, what is the order of fuel usage?4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system?6. What are essential nutrient & what are the 4 classes?7. What is the difference between malnourished & undernourished?8. How is food processed?9. What is the path that food takes through us?10. Let’s find out what happens along the way?11. What hormones control digestion?
- CCK – cholecystokinin- Secretin- Gastrin - Enterogastrone
Figure 41.22 Hormonal control of digestion
Amino acids or fatty acids in the duodenum trigger the release of cholecystokinin (CCK), which
stimulates the release of digestive enzymes from the pancreas and bile
from the gallbladder.
Liver
Gall-bladder
CCK
Entero-gastrone
Gastrin
Stomach
Pancreas
Secretin
CCK
Duodenum
Key
StimulationInhibition
Enterogastrone secreted by the duodenum inhibits peristalsis and acid secretion by the stomach, thereby slowing digestion when acid chyme rich in fats enters the duodenum.
Secreted by the duodenum, secretin stimulates the pancreas to release sodium bicarbonate, which neutralizes acid chyme from the stomach.
Gastrin from the stomach recirculates via the bloodstream back to the stomach, where it stimulates the production of gastric juices.
This ensures enzymes are only present when needed.
Chapter 41: Animal Nutrition
1. Why do we eat?2. What are the 4 main feeding mechanisms of feeding?3. When our bodies need energy, what is the order of fuel usage?4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system?6. What are essential nutrient & what are the 4 classes?7. What is the difference between malnourished & undernourished?8. How is food processed?9. What is the path that food takes through us?10. Let’s find out what happens along the way?11. What hormones control digestion?12. How & where are nutrients absorbed?
- Facilitated diffusion & active transport of monomers- Microvilli of small intestine
Figure 41.23 The structure of the small intestine
Epithelialcells
Key
Nutrientabsorption
Vein carrying blood to hepatic portal vessel
Villi
Largecircularfolds
Intestinal wall Villi
Epithelial cells
Lymph vessel
Bloodcapillaries
Lacteal
Microvilli(brush border)
Muscle layers
Chapter 41: Animal Nutrition
1. Why do we eat?2. What are the 4 main feeding mechanisms of feeding?3. When our bodies need energy, what is the order of fuel usage?4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system?6. What are essential nutrient & what are the 4 classes?7. What is the difference between malnourished & undernourished?8. How is food processed?9. What is the path that food takes through us?10. Let’s find out what happens along the way?11. What hormones control digestion?12. How & where are nutrients absorbed?13. How & where are fats absorbed?
- Fats are emulsified by bile salts- Absorbed into the lacteal w/in the villi – lymph system
Figure 41.24 Digestion and absorption of fats
Large fat globules are emulsified by bile salts in the duodenum.
Fat globule
Lacteal
Epithelialcells ofsmallintestine
Micelles madeup of fatty acids,monoglycerides,and bile salts
Fat dropletscoated withbile salts
Bile salts
Digestion of fat by the pancreatic enzyme lipase yields free fatty acids and monoglycerides, which then form micelles.
Fatty acids and mono-glycerides leave micelles and enter epithelial cells by diffusion.
Chylomicrons containing fattysubstances are transported out of the epithelial cells and into lacteals, where they are carried away from the intestine by lymph.
1
2
3
4
Chapter 41: Animal Nutrition
1. Why do we eat?2. What are the 4 main feeding mechanisms of feeding?3. When our bodies need energy, what is the order of fuel usage?4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system?6. What are essential nutrient & what are the 4 classes?7. What is the difference between malnourished & undernourished?8. How is food processed?9. What is the path that food takes through us?10. Let’s find out what happens along the way?11. What hormones control digestion?12. How & where are nutrients absorbed?13. How & where are fats absorbed?
- Fats are emulsified by bile salts- Absorbed into the lacteal w/in the villi – lymph system
14. What is the purpose of the large intestine?- Absorption of water – makes feces solid- Home of endosymbiotic bacteria
Chapter 41: Animal Nutrition1. Why do we eat?2. What are the 4 main feeding mechanisms of feeding?3. When our bodies need energy, what is the order of fuel usage?4. How is appetite regulated in the body? 5. What happens if there is a mutation in the leptin system?6. What are essential nutrient & what are the 4 classes?7. What is the difference between malnourished & undernourished?8. How is food processed?9. What is the path that food takes through us?10. Let’s find out what happens along the way?11. What hormones control digestion?12. How & where are nutrients absorbed?13. How & where are fats absorbed?14. What is the purpose of the large intestine?15. What are some evolutionary adaptations of the vertebrate digestive system?
- Teeth shape- Intestinal length- Symbiotic adaptations for fermentation in herbivores- Storage chambers
Figure 41.26 Dentition and diet
(a) Carnivore
(b) Herbivore
(c) Omnivore
Incisors
Canines
Premolars
Molars
Figure 41.27 The digestive tracts of a carnivore (coyote) and herbivore (koala) compared
Carnivore Herbivore
Colon(largeintestine)
Cecum
StomachSmall intestine
Small intestine
Figure 41.28 Ruminant digestion
Reticulum. Some boluses also enter the reticulum. In both the rumen and the reticulum, symbiotic prokaryotes and protists (mainly ciliates) go to work on the cellulose-rich meal. As by-products of theirmetabolism, the microorganisms secrete fatty acids. The cow periodically regurgitates and rechews the cud (red arrows), which further breaks down thefibers, making them more accessible to further microbial action.
Rumen. When the cow first chews andswallows a mouthful of grass, boluses(green arrows) enter the rumen.
1
Intestine
2
Omasum. The cow then reswallowsthe cud (blue arrows), which moves tothe omasum, where water is removed.
3 Abomasum. The cud, containing great numbers of microorganisms, finally passes to the abomasum for digestion by the cow‘s own enzymes (black arrows).
4
Esophagus