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