Chapter 46 - Animal Nutrition

Nutrient

Substance needed for survival, growth, and tissue repair

Nutrition

Process of consuming food and using nutrients

Ingestion

Phase where food enters the body

Digestion

Process of breaking down food into smaller molecules

Absorption

Movement of ions and small molecules into the circulatory system

Egestion

Elimination of undigested materials from the body

Carbohydrates

Organic nutrients including sugars and starches

Proteins

Organic nutrients essential for growth and repair

Lipids

Organic nutrients like fats and oils

Nucleic acids

Organic molecules like DNA and RNA

Vitamins

Organic nutrients serving as coenzymes

Water

Inorganic nutrient essential for life

Minerals

Inorganic ions with various functions in the body

Herbivores

Animals that eat only plants

Carnivores

Animals that consume animal flesh

Omnivores

Animals that eat both plant and animal material

Essential amino acids

Amino acids that must be obtained from diet

Essential fatty acids

Unsaturated fatty acids vital for health

Coenzymes

Molecules assisting enzymes in chemical reactions

Gastrovascular cavity

Simplest form of extracellular digestion in invertebrates

Alimentary canal

Tube with openings at both ends for digestion

Simple diffusion

Passive absorption of nutrients through cell membranes

Facilitated diffusion

Absorption with the help of specific proteins

Active transport

Energy-requiring absorption mechanism

Functional regions

Alimentary canal sections with distinct roles in digestion

Storage organs

Organs like crop, gizzard, and stomach for food storage or initial digestion

Peristalsis

Involuntary muscle contractions moving food through the esophagus

Ruminants

Animals like cows with specialized stomachs for digesting cellulose

Villi

Finger-like projections in the small intestine increasing surface area for absorption

Lacteal

Part of the lymphatic system absorbing fat particles in the small intestine

Bile

Liver-produced fluid aiding in fat digestion by breaking up fat droplets

Chyme

Partially digested food in the stomach reduced to a solution

Micelles

Structures formed by bile salts and phospholipids to aid lipid absorption

Chylomicrons

Aggregates of lipids released into lacteals for absorption

Amylase

Enzyme in saliva initiating carbohydrate digestion

Pepsinogen

Inactive enzyme in the stomach converted to pepsin for protein digestion

Hydrochloric acid

Stomach acid killing microbes and aiding in digestion

Proteases

Enzymes breaking down proteins into amino acids

Lipase

Pancreatic enzyme breaking down lipids into fatty acids and glycerol

Emulsification

Process breaking down large lipid droplets into smaller ones

Capillary

Vessel absorbing nutrients into the blood from villi

Rumen

Chamber in ruminants' stomach containing cellulose-digesting microbes

Omasum

Chamber in ruminants absorbing water and ions from cud

Abomasum

True stomach in ruminants containing acid and proteases

Cecum

Part of the large intestine storing and concentrating fecal matter

Colon

Large intestine section absorbing ions and water from fecal matter

Rectum

Last part of the large intestine before feces are expelled

Vitamins, minerals and water

Do not require digestion and are absorbed in complete form. Water-soluble vitamins are absorbed by diffusion or active transport, while fat-soluble vitamins (A, D, E, and K) follow the pathway for lipid absorption. Small amounts of water are absorbed through the stomach, but most are absorbed from the small intestine.

Neural and Endocrine Control of Digestion

Involves nervous system effects with local control of muscular and glandular activity by neurons in the alimentary canal. Signals up and down the canal move digestion along. Long-distance regulation is done by the brain in response to stimuli such as stress or the sight and smell of food. Hormones are mainly secreted by cells scattered throughout the epithelium of the stomach and small intestine.

Impact on Public Health

Includes conditions like diarrhea, heartburn (acid reflux), and ulcers. Diarrhea affects over 2 billion cases worldwide each year, with cholera being a significant concern. Heartburn affects 1 in 4 individuals in the U.S. Ulcers, erosion of the alimentary canal, are most common in the lower esophagus, stomach, and small intestine, with approximately 20 million Americans affected.

Marshall and Warren's Discovery

Demonstrated a link between bacterial infection and ulcers. They observed active colonies of Heliobacter pylori in some ulcer patients, hypothesizing that this infection caused gastritis and ulcers. Their study showed that bismuth plus antibiotic cleared the infection from 74% of patients, with a lower relapse rate compared to antacid-plus-placebo treatment.

Liver

Produces bile; cone-shaped organ at the top

Bile Ducts

Merge to form common hepatic duct

Gallbladder

Stores bile; pear-shaped organ beneath liver

Common Bile Duct

Carries bile from liver to small intestine

Sphincter

Regulates entry of bile and enzymes into small intestine

Pancreas

Secretes enzymes and bicarbonates; flat pear-shaped organ on the left

Duodenum

Digests most food and absorbs most nutrients and water

Small Intestine

Where most digestion and absorption of nutrients occur

Pancreatic Amylase

Digests polysaccharides into disaccharides

Facilitated Diffusion

Transport mechanism for fructose absorption

Secondary Active Transport

Involves sodium ions for glucose and galactose absorption

Trypsinogen

Converted to trypsin by enzyme enterokinase

Polypeptides

Small proteins cleaved by trypsin and other proteases

Amino Acids

Absorbed by secondary active transport and facilitated diffusion

Gastrin

Secreted by the stomach in response to a meal

Cholecystokinin (CCK)

Stimulates the secretion of digestive enzymes and bicarbonate ions from the pancreas

Secretin

Stimulates the secretion of bicarbonate ions from the pancreas

H. pylori

Bacterium causing ulcers in humans

Endoscope

Instrument for visualizing ulcers and H. pylori

Antibiotic

Treatment to kill bacteria

Bismuth

Element with bacteria-killing properties

Ulcer

Lesion in the lining of the stomach or duodenum