WARM-UP

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WARM-UP

1. (Ch. 40) What is the principle of countercurrent
   exchange?
2. (Review) What are the 4 classes of
   macromolecules?
3. (Ch. 41) You eat a piece of candy. List the
   structures it passes through as it travels
   through your alimentary canal.
4. Where does most of the digestion of the candy in
   3 happen?

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Chapter 41 Animal Nutrition
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What you need to know

• Major compartments of alimentary canal (organs)
  and their contributions to animal nutrition.
• Digestive glands salivary, pancreas, liver, gall
  bladder and their contributions to animal
  nutrition.
• Digestion of carbs, proteins, fats, nucleic acids.

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Essential Nutrients required by cells, obtained
through food

• Four classes of essential nutrients
• Essential amino acids (8)
• Essential fatty acids
• Vitamins (13) - fat-soluble, water-soluble
• Minerals

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Dietary Deficiencies

• Undernourished diet is deficient in calories,
  not enough energy
• Malnourishment missing 1 essential nutrients

Herbivore licks exposed salts and minerals
lacking in plants.
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The main stages of food processing

• Ingestion eating
• Digestion breakdown of food into small molecules
• Mechanical (chewing, grinding)
• Chemical (enzymes)
• Absorption cells take up nutrients
• Elimination pass undigested materials from
  digestive system

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Digestive Compartments

• Most animals process food in specialized
  compartments
• Intracellular digestion of food inside cells by
  food vacuoles
• Ex. phagocytosis, pinocytosis, sponges
• Extracellular food broken down outside of cells
• Gastrovascular cavity (simple) or alimentary
  canal (complex)

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Intracellular Digestion Sponges
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Extracellular Digestion

• Compartments are outside of the animals body
• Gastrovascular cavity simple animals
  single-opening, two-way digestion (food in, waste
  out)

Digestion in a hydra
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• Alimentary canal more complex, one-way tubes
  with mouth and anus

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Specialized organs for digestion in Humans

• Digestive system alimentary canal glands
• Glands salivary glands, pancreas, liver, and
  gallbladder
• Q Can you name the organs of the human
  alimentary canal in order?

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• Peristalsis push food through rhythmic
  contractions of muscles in the wall of the canal
• Sphincters valves regulate the movement of
  material between compartments
• Digestion of Macromolecules
• Mouth carbs
• Stomach proteins
• Small Intestine carbs, proteins, fats, nucleic
  acids

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Digestion in the Mouth

• Oral cavity mechanical, chemical digestion
• Salivary glands saliva lubricates food
• Teeth chew food into smaller particles
• Salivary amylase breakdown glucose polymers
• Saliva contains mucus, a viscous mixture of
  water, salts, cells, and glycoproteins
• Pharynx back of throat
• Epiglottis flap of cartilage, covers trachea
  when swallowing
• Esophagus food tube (pharynx ? stomach)

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Digestion in the Stomach

• The stomach stores food and secretes gastric
  juice, which converts a meal to acid chyme
• HCl pH 2, kills bacteria denatures proteins
• Pepsin enzyme (protease) that hydrolyze proteins
  into smaller peptides
• Pepsinogen (inactive) ? pepsin (active) by HCl
• Mucus protects lining of stomach
• Gastric ulcers lesions in the lining, caused
  mainly by bacterium Heliobacter pylori

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Digestion in the Small Intestine

• SI major organ of digestion and absorption
• Duodenum first section, digestive juices, major
  chemical digestion
• Digestive juices
• Pancreas bicarbonate (basic), trypsin
  chymotrypsin (proteases) lipase (fats) amylase
  (carbs) nuclease (DNA, RNA)
• Bile made in liver, stored in gall bladder
• Emulsify fats (make smaller droplets)

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• Hormones that coordinate digestion
• Gastrin produced by stomach, ?production of
  gastric juices
• Entrogastrin produced by SI (duodenum),
  ?peristalsis to allow time for fat digestion
• Secretin CCK (cholesystokinin) secreted by SI
  (duodenum), ?flow of digestive juices from
  pancreas gall bladder

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Absorption in the Small Intestine

• Villi and microvilli increase surface area

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• Villi ? capillaries ? hepatic portal vein ? liver
  ? heart
• Liver distribute nutrients, detox, glucose
  storage (glycogen)

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Absorption in the Large Intestine

• LI colon
• Function compact waste, reabsorb water
• Cecum pouch where SI LI meet, ferment plant
  material
• Appendix extension of cecum, role in immunity
• Rectum end of LI, feces stored until elimination

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Evolutionary adaptations of vertebrate digestive
systems correlate with diet

• Dentition teeth correlate with diet
• Herbivores longer alimentary canal, longer cecum

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Mutualistic Adaptations

• Many herbivores have fermentation chambers, where
  mutualistic microorganisms digest cellulose
  (ruminants)

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Homeostatic Mechanisms

• Vertebrates store excess calories as glycogen in
  the liver and muscle cells, and as fat in adipose
  tissue
• Overnourishment can lead to obesity
• Leptin hormone, suppresses appetite

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Glucose Homeostasis