chapter 41 animal nutrition. 3 main categories of feeding: herbivores – plants & algae...
TRANSCRIPT
Chapter 41
Animal Nutrition
3 main categories of feeding:
Herbivores – Plants & algae
Carnivores – Meat
Omnivores – Both
3 needs:Fuel (ATP)
Organic matter for biosynthesis
Essential nutrients - vitamins
Four Main Feeding Mechanisms of Animals
Baleen
SUSPENSION FEEDERS
Feces
SUBSTRATE FEEDERS
BULK FEEDERS
FLUID FEEDERS
Caterpillar
FeedersSuspension – Sift food from H20
(strainer)
Substrate – Live in or on food
Fluid – Suck nutrients from host
Bulk – Large pieces
Glucose regulationLiver and muscle cells store
energy in the form of glycogen (extra stored as fat)
Regulation – Negative feedback Thermostat in house
STIMULUS:Blood glucose
level risesafter eating.
Homeostasis:90 mg glucose/100 mL blood
STIMULUS:Blood glucose
level dropsbelow set point.
When blood glucose level rises, a gland called the pancreas secretes insulin,a hormone, into the blood.
1
Insulin enhances the transport of glucose into body cells and stimulates the liver and muscle cells to store glucose as glycogen. As a result, blood glucose level drops.
2
When blood glucose level drops, the pancreas secretes the hormone glucagon, which opposes the effect of insulin.
3
Glucagon promotes the breakdown
of glycogen in the liver and
there lease of Glucose into the blood,increasing
blood glucose level.
4
41.2 Animal’s diets must supply carbon skeleton and essential nutrients
Make Carbohydrates, Proteins and lipids from sugar and nitrogen.
Essential nutrients – can’t make must get from food pre-madeAmino acids – 20 (meat, cheese, animal products)Fatty acids – unsaturated easily attained in diet Vitamins – 13 essential – H20 soluble & fat soluble
C, A, D, E , KMinerals - Inorganic nutrients – Calcium, Phosphate,
Iron, Zinc
Obtaining essential nutrients
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
41.3 Stages of food processing
Organic material in food – fats, proteins, and carbohydrates
Steps of digestion:1. Ingestion – Eating2. Digestion – Breaking down
food into molecules small enough for the body to absorb
The four stages of food processing
Piecesof food
Smallmolecules
Mechanicaldigestion
Food
Chemical digestion(enzymatic hydrolysis)
Nutrient moleculesenter body cells
Undigested material
INGESTION1 DIGESTION2 ELIMINATION4ABSORPTION3
3. Absorption – Cells take up small molecules
4. Elimination – Undigested material passes
Risk of digesting one’s self?
No – Specialized compartments
Intracellular – One cell/Sponges
Extracellular – Breaking down food outside cells
Digestion in a hydra
Gastrovascularcavity
Food
Epidermis
Mesenchyme
Gastrodermis
Mouth
Tentacles
Mesenchyme
Food vacuoles
Gland cells
Flagella
Nutritivemuscularcells
Gastrovascular Cavity - Sac with a single opening – Hydras, Jellies & flatworms
Variation in alimentary canals
Esophagus
Mouth
Pharynx
Crop GizzardIntestine
Anus
Typhlosole
Lumen of intestine
Esophagus
Anus
Rectum
Mouth
CropGastric ceca
Anus
Intestine
Gizzard
Crop
Stomach
Mouth
Esophagus
Foregut Midgut Hindgut
(a) Earthworm. The digestive tract ofan earthworm includes a muscular pharynx that sucks food in through themouth. Food passes through the esophagus and is stored and moistened in the crop. The muscular gizzard, whichcontains small bits of sand and gravel, pulverizes the food. Digestion and absorption occur in the intestine, which has a dorsal fold, the typhlosole, that increases the surface area for nutrient absorption.
(b) Grasshopper. A grasshopper has several digestive chambers grouped into three main regions: a foregut, with an esophagus and crop; a midgut; and a hindgut. Food is moistened and stored in the crop, but most digestion occurs in the midgut. Gastric ceca, pouches extending from the midgut, absorb nutrients.
(c) Bird. Many birds have three separate chambers—the crop, stomach, and gizzard—where food is pulverized and churned before passing into the intestine. A bird’s crop and gizzard function very much like those of an earthworm. In most birds, chemical digestion and absorption of nutrients occur in the intestine.
Complete digestive system or alimentary canal
Nematodes, annelids, mollusks, arthropods, echinoderms & chordates
Mouth Anus
Specialized compartments
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
Pharynx
Esophagus
Stomach
Pyloricsphincter
Cardiacorifice
Mouth
Esophagus
Salivaryglands
Stomach
Liver
Pancreas
Gall-bladder
Large intestines
Small intestines
RectumAnus
Parotid glandSublingual gland
Submandibular gland
Salivaryglands
A schematic diagram of the human digestive system
The human digestive system
Pancreas
Peristalsis – rhythmic waves of contraction and relaxation
Smooth Muscles pushes the food along the tract
Sphincters – Regulate the passage of material between chambers (Drawstring)
From mouth to stomach: the swallowing reflex and esophageal peristalsis
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
Stomach
1 When a person is not swallowing, the esophageal sphincter muscle is contracted, the epiglottis is up, and the glottis is open, allowing air to flow through the trachea to the lungs.
The swallowingreflex is triggeredwhen a bolus offood reaches thepharynx.
2
The larynx, theupper part of therespiratory tract,moves upward andtips the epiglottisover the glottis,preventing foodfrom entering thetrachea.
3
Waves of muscularcontraction (peristalsis)
move the bolus down the esophagus
to the stomach.
6
After the foodhas entered theesophagus, the
larynx movesdownward and
opens thebreathingpassage.
5
The esophagealsphincter relaxes,allowing thebolus to enter theesophagus.
4
Accessory GlandsSalivary Glands – Deliver saliva with
salivary amylase to begin chemical digestion
Pancreas – Digestive juices that mix with chyme in the small intestine
Liver – Produces bile. Bile salts aid in the break down of fats
Gall Bladder – Bile is stored here until needed
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 µ
m
Small intestine
Cardiac orifice
Stomach Stores food and does preliminary
digestion.
Coating of mucus to not self digest.
Mixing makes acid chyme. Every 20 seconds due to smooth muscles.
Pyloric sphincter squirts the acid chyme to the small intestines. 2 to 6 hours for a meal to empty.
The duodenumLiver Bile
Acid chyme
Stomach
Pancreatic juice
Pancreas
Intestinaljuice
Duodenum of small intestine
Gall-bladder
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
Proteins
Pepsin
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
Nucleosides
Nucleosidasesandphosphatases
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
Small IntestineAbsorption of nutrients takes place
6 meters
Duodenum - beginning of S.I.
Chyme
Villi – increases SA for more absorption
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
Large Intestine (Colon)Recover water that has
entered the alimentary canal
Feces (waste) becomes more solid as it moves through
Flora of bacteria – E. Coli
Colon bacteria secrete methane and hydrogen sulfide
41.5 ModificationsTeeth – Structural variation
reflecting dietsFangs – modified teeth &
unhinged jaw
Dentition and diet
(a) Carnivore
(b) Herbivore
(c) Omnivore
Incisors
Canines
Premolars
Molars
The digestive tracts of a carnivore (coyote) and herbivore (koala) compared
Carnivore Herbivore
Colon(largeintestine)
Cecum
StomachSmall intestine Small intestine
*Stomach – Expandable - Carnivores*Length of alimentary canal – Herbivores longer