Nutrition

• Autotrophs

– plants, some protists & bacteria

– producers

Nutrition

• Heterotrophs

– animals, fungi, some protists & bacteria

– consumers

Animal Nutrition

• Most obtain food by ingestion

– take in their food whole or piece by piece

Animal Nutrition

• Classify based on what they eat:

– Herbivores (primary consumers)

• eat autotrophs

– Carnivores (secondary or higher consumers)

• eat heterotrophs

– Omnivores

• eat both

Stages of Food Processing• Ingestion

– eating

• Digestion

– breaking down food into small molecules

– mechanical and chemical (enzymatic hydrolysis)

• Absorption

– body takes in small molecules

• Elimination

– undigested material exits the body

Digestion

• Must take place in specialized

compartments

• to avoid damage to body cells

Food vacuoles

• food enters by endocytosis & then vacuole

merges with lysosome

• Some protists

• Sponges

– only animal with only intracellular digestion

Figure 41.10 Intracellular digestion in Paramecium

Gastrovascular Cavities

• single opening

• serve to both digest & transport nutrients

• extracellular digestion, then intracellular

• Platyhelminthes (planaria) & Cnidarians

(hydra)

What is the advantage of

extracellular digestion?

Eat larger food

Extracellular digestion in a gastrovascular cavity

Alimentary canals

or Complete Digestive Tracts

• two openings: mouth & anus

• food passes in one direction

• Found in all other animals

What is the advantage of one-

way movement of food?

• Allows for specialization of different

regions of the digestive tract

Figure 41.12 Alimentary canals

Types of Digestive Systems

Nematode Earthworm

Mouth

MouthPharynx

Pharynx

Intestine Intestine

Anus

Anus

Crop

Gizzard

Salamander

Mouth

Esophagus

Intestine

AnusLiver

Pancreas

StomachCloaca

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Mammalian Digestive System

• Four-layered wall surrounds the lumen

– Mucosa (epithelial tissue)

– Submuscosa (connective tissue)

– Muscularis (muscle)

– Serosa (connective tissue)

Salivary gland

Salivary

glands

Liver

Oral cavity

Esophagus

Gallbladder

Pharynx

Cecum

Appendix

Anus

Rectum

Small intestine

Pancreas

Stomach

Colon

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Human Digestive System

• Mouth

– teeth mechanically break down food

• Similar in function to the gizzard of birds and worms

– saliva is secreted from salivary glands

• mucous protects mouth

• antibacterial agents

• buffer to neutralize acidity

• salivary amylase – hydrolyzes glucose polymers

Human Digestive System

• Pharynx (throat)

– swallowing

• Esophagus

– peristalsis

Pharynx

Soft palate

Hard palate

Tongue

Epiglottis

Larynx

Trachea

Esophagus

Air

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1. As food moves to the back of the mouth, the soft palate seals offthe nasal cavity.

2. During swallowing, the larynx risesand is sealed off by the epiglottis. This forces the bolus into the esophagus and prevents entry intothe trachea. As the bolus movesinto the esophagus the larynx relaxes.

Swallowing

Esophagus

Food Bolus

Peristalic

movement

Contraction

Relaxation

Relaxation

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Human Digestive System

• Stomach

• stores food (as does the crop in other organisms)

• lining secretes gastric juice

• Pepsinogen (inactive) becomes pepsin (active) in

low pH

• smooth muscles churn the food

• Acid chyme

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Gastric pit

Gastric pit

Muscularis

Pyloric

sphincter

Longitudinal

Circular

Oblique

Muscularis

Longitudinal

Circular

Oblique

Serosa

Serosa

Submucosa

Mucosa

Gastric glands

Chief

cell

Parietal

cell

Mucous

cell

Esophagus

Stomach

Mucosa

Duodenum

The Stomach

Human Digestive System

• Small Intestine

• Longest part of the canal (6 m in humans)

• Duodenum (first 25 cm) – most digestion takes

place

• Jejunum and ileum – mainly absorption

• Very large surface area (300 m2) – folds, villi &

microvilli

– Similar to mycelium in fungi & roots in plants

Small intestine

Villi

Villus

Mucosa

Serosa

Submucosa

Muscularis

Epithelial

cell

Capillary

Lacteal

Vein

Artery

Lymphatic

duct

The Small Intestine

From liver

Gallbladder

Pancreatic

duct

PancreasCommon

bile duct

Duodenum

cell

cell

Pancreatic islet

(of Langerhans)

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Human Digestive System

• Accessory Glands:

– Pancreas

• digestive enzymes

– Lipase-lipids; pancreatic amylase-starch; trypsin - proteins

• Bicarbonate- buffer

Human Digestive System

• Accessory Glands:

– Liver

• produces bile salts which are stored in the

gallbladder until needed

• aid in the digestion of fats by emulsification

– Gallbladder

Human Digestive System

• Large Intestine or Colon

– main function is concentration & storage of

wastes

• absorption of water, sodium, vitamin K

– Feces are moved along by peristalsis and exit

the body through the anus

Hormonal Control of Digestion

• Gastrin

– released by the stomach

– feeds back to cause the secretion of gastric

juices

– Low pH inhibits its production – negative

feedback

( + ) ( + )

( + )( + )

( + )

Gallbladder

Duodenum

Pancreas

Stomach

Proteins

pH

Enzymes

Bicarbonate

Pepsin HCl

Parietal cells

Gastrin

Bile

Acinar

cells

Liver

Chief cells

Secretin

CCK

( – )

GIP

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Hormonal Control of Digestion• Enterogastrones

– Released by duodenum of small intestine

– inhibit peristalsis & secretions in the stomach

– Secretin

• Stimulated by low pH

• causes pancreas to release bicarbonate

– CCK (cholecystokinin)

• Stimulated by high fat content

• Stimulates gall bladder to release bile

– GIP (gastric inhibitory peptide)

• Inhibits emptying of the stomach

( + ) ( + )

( + )( + )

( + )

Gallbladder

Duodenum

Pancreas

Stomach

Proteins

pH

Enzymes

Bicarbonate

Pepsin HCl

Parietal cells

Gastrin

Bile

Acinar

cells

Liver

Chief cells

Secretin

CCK

( – )

GIP

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Evolutionary Adaptations to Diet

• Teeth

– pointed in carnivores, flat in herbivores

MolarsPremolarsIncisors

Canines

Horse Lion Human

Herbivore Carnivore Omnivore

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Mouth and Teeth

Evolutionary Adaptations to Diet

• Length of gut

– longer in herbivores than carnivores

• Cecum

– houses bacteria that aid in digestion

Stomach

Anus

Anus

Spiral

loop

EsophagusRumen

Reticulum

Omasum

Abomasum

Cecum

Insectivore

Short intestine, no cecum

Anus

Esophagus

Cecum

Stomach

CarnivoreShort intestine and

colon, small cecum

Ruminant HerbivoreFour-chambered stomach with large rumen;

long small and large intestine

Anus

Cecum

Small

intestine

Large

intestine

Small

intestine

Large

intestine

Small

intestine

Large

intestine

Small

intestine

Large

intestine

Stomach

Esophagus

Nonruminant Herbivore

Simple stomach, large cecum

Esophagus

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Evolutionary Adaptations to Diet

• Ruminant Stomach- cows, deer

Esophagus

Rumen

Reticulum

OmasumAbomasum

Small intestine

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Evolutionary Adaptations to Diet

• Coprophagy – rodents, rabbits