The great Serengeti migration: A quest for minerals

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The great Serengeti migration A quest for
minerals
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Digestive system

• Functions
• Organs

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Organs of alimentary canal
Figure 23.2
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MonthEsophagusStomachSmall intestineLarge
intestineAccessory organsSalivary glands,
liver, pancreas, gall bladder
Figure 23.1
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Digestive tracts of various vertebrates
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Digestive tracts of invertebrates and vertebrates
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Figure 4.1 The composition of the adult human
body
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Nutrition

• Proteins
• Lipids
• Carbohydrates
• Vitamins and minerals

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Figure 4.2 Amino acid chemistry (Part 1)
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Figure 4.2 Amino acid chemistry (Part 2)
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Figure 4.3 Fatty acids and triacylglycerols
(Part 1)
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Figure 4.3 Fatty acids and triacylglycerols
(Part 2)
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Figure 4.4 Carbohydrate chemistry
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Figure 4.5 Vitamin structures
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Feeding

• Examples of feeding adaptations
• Food chains

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Figure 4.6 Some species feed by targeting and
subduing individual food items (Part 1)
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Figure 4.7 Specialization of a vertebrate
feeding apparatus
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Dentition
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Figure 4.8 Specialization of an invertebrate
feeding apparatus (Part 1)
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Figure 4.8 Specialization of an invertebrate
feeding apparatus (Part 2)
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Figure 4.10 The feeding apparatus of a baleen
whale
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Figure 4.12 Reef-building corals of warm waters
need light because they are symbiotic with algae
(2)
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Figure 4.9 Short food chains deplete energy less
than long food chains do
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Digestive systems of insects and crustaceans

• Crustaceans digestive system is separate from
  the excretory system
• Insects the Malpighian tubules excretory
  system is connected at the junction of the midgut
  and hindgut

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Figure 4.16 The digestive systems of two types
of arthropods insects and crustaceans
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Figure 23.1
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Stomach (continued)

• Contractions of the stomach churn chyme.
• Mix chyme with gastric secretions.
• Push food into intestine.

Insert fig. 18.5
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Small Intestine

• Each villus is a fold in the mucosa.
• Covered with columnar epithelial cells
  interspersed with goblet cells.
• Epithelial cells at the tips of villi are
  exfoliated and replaced by mitosis in crypt of
  Lieberkuhn.
• Lamina propria contain lymphocytes, capillaries,
  and central lacteal.

Insert fig. 18.12
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Histology of the Alimentary Canal
Figure 23.6
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Sensors of the GI tract regulatory mechanisms

• Mechanoreceptors and chemoreceptors involved
• Located in the walls of the tract organs
• Sensors respond to
• Stretching
• Osmolarity
• pH
• Presence of substrates and end-products

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Regulatory mechanisms (2)

• Receptors initiate reflexes
• Activate of inhibit glands that secrete digestive
  juices
• Stimulate smooth muscle of GI tract
• Move food along the tract
• Mix lumen content

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Peristalsis and Segmentation
Figure 23.3
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Adaptation associated with animals diet

• Microbe-assisted digestion animals in
  hydrothermal vents-trophosomes
• Dentition/mouth parts
• Length of digestive tract
• Herbivores
• Carnivores
• Omnivores
• Sharks
• Birds

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Microbe-dependent digestion

• Digestion assisted by microbes

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Animals maintain symbiosis with three categories
of microbes

• Heterotrophic microbes
• Organic compounds of external origin
• Autotrophic microbes
• Synthesize organic molecules from inorganic
  precursors
• Chemosynthetic
• Photosynthetic

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Figure 4.13 Hydrothermal-vent worms are
symbiotic with chemoautotrophic bacteria (Part 1)
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Hydrothermal-vent worms

• Symbiotic with chemoautotrophic bacteria-
  trophosomes
• Worms have not mouth, gut, or anus
• Food comes from sulfur-oxidizing chemoautotrophic
  bacteria
• Organic molecules from bacteria meets nutritional
  needs
• Vents- source of H2S

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Hydrothermal-vent worms

• Symbiotic with chemoautotrophic bacteria-
  trophosomes
• Worms have not mouth, gut, or anus
• Food comes from sulfur-oxidizing chemoautotrophic
  bacteria
• Organic molecules from bacteria meets nutritional
  needs
• Vents- source of H2S

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Figure 4.13 Hydrothermal-vent worms are
symbiotic with chemoautotrophic bacteria (Part 2)
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Comparison of the digestive tracts of carnivores
and herbivores

• Carnivores- foregut digestion
• Herbivores
• Hindgut
• Foregut

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Figure 4.14 The digestive tract of ruminants
(Part 1)
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Stomach of ruminants

• Several chambers
• Rumen first chamber/fermentation occurs
• Regurgitate fermenting materials from the rumen
  into mouth
• Further grinding and reswallow
• From rumen ?reticulum ?omasum ?abomasum (true
  stomach)

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Functions of microbes in ruminants

• Synthesize B vitamins, essential amino acids
• Fermentative breakdown of compounds that animals
  cannot digest cellulose
• Recycle waste nitrogen from animal metabolism
• Make ammonia so other microbes can use it as
  nitrogen source

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Figure 4.14 The digestive tract of ruminants
(Part 2)
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Figure 4.15 The digestive tracts of two hindgut
fermenters
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Hind and midgut fermenters

• Enlarged cecum/colon
• Rabbits, horses, zebras, rhinos, apes, elephants
• Break down of cellulose and carbohydrates
• Forms short-chain fatty acid
• B vitamins- not utilized, lost in feces
• Coprophagy rabbits eat special soft feces

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A comparison of the digestive tracts of a
carnivore (coyote) and a herbivore (koala)
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Digestion and absorption

• Digestive enzymes in 3 spatial contexts
• Intraluminal enzymes
• Membrane-associated enzymes
• Intracellular enzymes

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Intracellular and extracellular digestion

• Intraluminal and membrane-associated enzymes are
  responsible for extracellular digestion
• Intracellular enzymes are responsible for
  intracellular digestion
• Advantages and disadvantages of intra- and
  extracellular digestions?

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Figure 4.17 The stomach of a clam (Part 2)
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Carbohydrate digestion  
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Figure 4.19 Absorption of monosaccharides in the
vertebrate midgut (Part 2)
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Protein digestion  
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Figure 4.18 The digestion of a short protein by
three pancreatic peptidases
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  Fat digestion
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Chemical Digestion Fats
Figure 23.35
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Figure 4.19 Absorption of monosaccharides in the
vertebrate midgut (Part 1)
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Chemical Digestion Carbohydrates

• Carbohydrates absorption via cotransport with
  Na, and facilitated diffusion
• Enter the capillary bed in the villi
• Transported to the liver via the hepatic portal
  vein

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Chemical Digestion Proteins

• Absorption similar to carbohydrates
• Enzymes used pepsin in the stomach
• Enzymes acting in the small intestine

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Chemical Digestion Fats

• Absorption Diffusion into intestinal cells where
  they
• Combine with proteins and extrude chylomicrons
• Enter lacteals and are transported to systemic
  circulation via lymph

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Coordination of digestion neural and endocrine
control

• Controls of digestive activity
• Extrinsic
• Central nervous system and autonomic nervous
  system
• Intrinsic
• Hormone-producing cells in stomach and small
  intestine
• Distributed via blood and interstitial fluid to
  target cells

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Endocrine control

• Endocrine control
• Gastrin
• Secretin
• CCK
• GIP
• Where?
• When?
• Why?
• How?

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Figure 4.20 GI function after a meal is
coordinated in part by hormones secreted by cells
in the gut