Ch. 41

Need to FeedAnimal nutrition• Food being taken in, taken apart, and taken upHerbivores• Dine mainly on plantsCarnivores• Dine mainly on other animals Omnivores• Regularly dine on animals, plants, and algaeOpportunistic Feeders• Eat outside normal diet when usual foods are

unavailable

Essential NutrientsMaterials that an animal’s cells require but

cannot synthesizeEssential Amino Acids• Must be obtained from food (8)Essential Fatty Acids• Most are synthesizedVitamins• Organic molecules that have diverse functions

and are required in the diet in very small amounts

• Water soluble vs. fat solubleMinerals• Inorganic nutrients required in small amounts• cofactors

Essential Nutrients

Essential Nutrients

Dietary DeficienciesDiet that lacks one or more essential

nutrients or consistently supplies less chemical energy than the body requires

Malnourished• Failure to obtain adequate nutritionUndernutrition• A diet that fails to provide adequate

sources of chemical energyOvernourished• obesityAssessing Nutritional Needs

Ingestion, Digestion, Absorption, Elimination

1. Ingestion– act of eating/feeding

2. Digestion– Food is broken down

into molecules small enough for the body to absorb

– Mechanical and chemical

3. Absorption– uptake of small

molecules from digestion

4. Elimination– undigested material

passes out of the digestive compartment

Four Main Feeding Mechanisms of Animals

Suspension feeders and filter feeders

• Eat small organisms or food particles suspended in the water– clams, oysters

• Use a filtering structure to strain food from water– Baleen whale

Substrate feeders• live on or in their food

source• leaf miners

Feeding AdaptationsDeposit feeders

• substrate feeder that ingests partially decayed organic matter

• EarthwormsFluid feeders• suck nutrient rich fluids from a

living host• aphids, hummingbirds, bees,

leeches, mosquitoes

Bulk feeders• eat relatively large pieces of food• adaptations to kill prey or tear

off vegetation

Digestive Compartments

Intracellular Digestion• Hydrolysis of food inside

vacuoles• Begins with phagocytosis

or pinocytosisFood vacuoles• organelle that digests its

food without hydrolytic enzymes mixing with the cell’s cytoplasm

• Fuse with lysosomes• Sponges

Digestive CompartmentsExtracellular digestion• Digestion occurs within

compartments that are continuous, with the outside of the body

Gastrovascular cavity• digestive sac with a single

opening; functions in both digestion and nutrient absorption

• More complex animals have alimentary canals

Digestive CompartmentsAlimentary canal

(complete digestive tract)

• digestive tube running between two openings: mouth and anus

• organized into compartments for digestion and absorption (increases efficiency)

• unidirectional passage of food

Mammalian Digestion

Organs Specialized for Sequential Food Processing

Alimentary Canal and Accessory Organs

Peristalsis• Alternating waves of

contraction and relaxation in the smooth muscles lining the canal

Sphincters• junctions b/w

specialized compartments that act like ringlike valves

Oral Cavity, Pharynx, Esophagus

Oral Cavity• Beginning of physical and

chemical digestion– chewing– secretions from salivary

glands

Saliva contains…– mucin, buffers, antibacterial

agents, amylase

Bolus– chewed food that enters the

pharynx

Pharynx• intersection for

both digestive and respiratory systems

• epiglottis blocks trachea during swallowing

Esophagus• conducts bolus

from pharynx to stomach via peristalsis

Oral Cavity, Pharynx, Esophagus

Digestion in the StomachFood storage• elastic wall with rugae to hold

up to 2L of foodChurning• contraction of stomach muscles• mixed about every 20 minutes;

takes 2-6 hours to pass to the small intestine

• Begins digestion of protein• bolus chyme• passes to small intestine

through pyloric sphincter

Digestion in the StomachSecretion• controlled by the

hormone, gastrin• mucous cells (secrete

mucin & gastrin)• chief cells (release

pepsinogen or zymogen)

• parietal cells (secrete HCl & intrinsic factor)

• HCl + pepsinogen pepsin (a protease – a protein digesting enzyme)

Digestion in the Small Intestine• Cholecystokinin• Major organ of digestion

and absorption• Pancreas, liver, gall

bladder, and small intestine all contribute to what occurs here

• Products released into duodenum– 1st part of the small

intestine• Jejunum and ileum

– Villi and microvilli

Pancreatic Secretions

Exocrine glandSecretes hydrolytic enzymesProduces bicarbonate solution to

neutralize stomach acid

Bile Production and Secretions by LiverBile

• Mixture of substances made in the liver that act as emulsifiers of fat

• Stored and concentrated in the gall bladder

Epithelial lining• Source of many digestive enzymes

Absorption in the Small IntestineVilli

• Fingerlike, epithelial projections• Microvilli – epithelial projections

on each villus cellHepatic portal vein• Blood vessel that leads to

directly to the liver• Liver regulates distribution of

nutrients and allows toxins to be removed

Absorption in the Small IntestineChylomicrons

• Water soluble fat globules made of triglycerides coated in phospholipids, cholesterol and proteins

Lacteal• Vessel at the end of each

villus• Part of lymphatic system

Absorption in the Large Intestine

Cecum, colon, rectumAppendix is an extension of the cecum• lymphoid tissueWater reabsorptionFeces moved along by peristalsis• Becomes increasingly solidIntestinal bacteria• Methane, hydrogen sulfide, vitamin K,

biotin, folic acidTwo sphincters (one voluntary and one

involuntary) control the exiting of the feces

Digestive System

Digestive System

Dental Adaptations•carnivores: pointed canines & incisors

•herbivores: broad, ridged surfaces

•omnivores: unspecialized

•snakes: fangs

Length of tract and diet

–herbivores and omnivores have a longer tract b/c cell walls are more difficult to digest

Stomach and Intestinal Adaptations

Mutualistic AdaptationsSymbiotic bacteria

and protozoa

• Produce cellulase• Horses: in large

cecum• Rabbits and

some rodents: in cecum and colon– Corophagy

(”dung eating”)

• Ruminants– Deer sheep cattle

Regulation of Digestion1. Gastrin2. Cholecystokinin and secretin

Glucose Homeostasis1. High blood

glucose– insulin

2. Low blood glucose– glucagon

Regulation of Appetite and Consumption

Ghrelin• Triggers

feelings of hunger

Insulin• Suppresses

appetiteLeptin• Suppresses

appetitePYY• Appetite

suppressant; counters ghrelin