Transcript File - G. Scott`s Bio Page

• Chapter 41 – Animal
Nutrition
Food Types / Feeding Mechanisms
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Opportunistic
Herbivore: eat autotrophs
Carnivore: eat other animals
Omnivore: both
Feeding Adaptations
Suspension-feeders: sift
food from water (baleen
whale)
• Substrate-feeders: live in or
on their food (leaf miner)
(earthworm: deposit-feeder)
• Fluid-feeders: suck fluids
from a host (mosquito)
• Bulk-feeders: eat large
pieces of food (most
animals)
Homeostasis & Energy Budget
• “Budget” – flow of energy
into and out of an animal’s
body
• Regulated through
homeostatic mechanisms,
ex. Glucose
• Blood glucose rises,
pancreas secretes insulin,
enhances transport of
glucose into body cells and
stimulates liver and muscle
to store glucose as
glycogen
• Blood glucose falls,
pancreas secretes
glucagon, promotes
breakdown of glycogen in
liver and release into the
blood stream
Caloric Imbalance
• Undernourishment – stores of fat and glycogen used up,
body breaks down proteins for fuel, caloric deficiency
• Overnourishment – body hoards fat instead of using it for
fuel
• Malnourishment – essential nutrient deficiency
• Obesity – a global problem, lead to a variety of health
problems
• Science currently conducting research to discover
homeostatic mechanisms for food intake
Appetite Regulation
• Most appetite regulatory hormones
are proteins, dozens of genes have
been identified that code for these
hormones
• Leptin – produced by adipose tissue,
suppresses appetite as fat increases
• PYY – small intestine, after meals,
suppresses appetite
• Insulin – pancreas, rise in sugar
levels after a meal, suppresses
appetite
• Ghrelin – stomach wall, triggers
feelings of hunger as mealtime
approaches, as diet/lose weight,
ghrelin levels increase
• Many of these are feedback
mechanisms that prevent people from
becoming overweight or obese
Nutritional Requirements
• Essential nutrients: materials that must be
obtained in preassembled form
• Essential amino acids: the 8 amino acids that
must be obtained in the diet
• Essential fatty acids: unsaturated fatty acids
• Vitamins: organic coenzymes
• Minerals: inorganic cofactors
Essential Vitamins
Food Processing
• 1-Ingestion: act of eating
• 2-Digestion: process of food break down
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enzymatic hydrolysis
intracellular: breakdown within cells (sponges)
extracellular: breakdown outside cells (most animals)
alimentary canals (digestive tract)
• 3- Absorption: cells take up small molecules
• 4- Elimination: removal of undigested material
The Alimentary
Canal
• Primitive inverts have
gastrovascular cavity – a
digetive sac with a single
opening, functions in
digestion and distribution
of nutrients (cnidarians
and flatworms)
• All others have an
alimentary canal – a
digestive tube extending
between two openings, a
mouth and an anus
Mammalian digestion, I
• Peristalsis: rhythmic waves of contraction by smooth muscle
• Sphincters: ring-like valves that regulate passage of material
• Accessory glands: salivary glands; pancreas; liver; gall bladder
Mammalian digestion, II
• Oral cavity: salivary amylase (hydrolyzes starch), bolus (ball of
chewed food
• Pharynx (the throat): epiglottis - a cartilaginous flap that moves up to
cover the trachea (windpipe) during swallowing
• Esophagus: conducts food from the pharynx down to the stomach
by peristalsis
Mammalian digestion, II cont.
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Stomach – stores food and performs
preliminary steps of digestion
Churning and enzymes convert food
to nutrient broth called acid chyme
Secretion of enzymes – controlled by
nerve impulses and hormone gastrin
3 types of secretory cells:
Mucous cells, secrete mucin (thin
mucous layer protects stomach
lining) and gastrin (stimulates further
secretion of gastric juice)
Chief cells, secrete pepsinogen
(inactive precursor of pepsin,
becomes active when mixed with
acid)
Parietal cells, secrete HCl
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gastric juice (HCl and pepsin)
HC I- acidity (pH 1-4) kills bacteria,
starts conversion of pepsinogen to
pepsin
pepsin – begins to split peptide
bonds of large polypeptide chains
Mammalian digestion, III
• Small intestine – more than 6
meters in length in humans;
where most enzymatic hydrolysis
and absorption of nutrients
occurs
• 3 sections:
– duodenum – 25 cm, acid chyme
mixes with digestive juices from
the pancreas, liver, gall bladder,
and intestinal wall
• pancreas – protease for protein
digestion and bicarbonate to
buffer the acid chyme
• liver – bile for fat emulsification
(stored in the gall bladder)
• brush border – epithelial lining of
duodenum, secretion of several
different digestive enzymes
– jejunum - begin the absorption of
amino acids, sugars, fatty acids
and glycerol
– Ileum – significant absorption
due to large number of villi
Mammalian digestion, IV
• Villi (large circular folds) contain microvilli – increase surface area to
increase nutrient absorption; each villus contains microscopic blood
vessels (capillaries) and a lacteal (a small lymphatic vessel)
• Nutrients are absorbed across the intestinal epithelium and across the
epithelium of the capillaries or lacteal
• Hepatic portal vein – carries nutrient rich blood away from villi directly
to the liver (can interconvert various organic molecules)
Mammalian digestion, V
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Hormonal Action:
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gastrin – stomach, gastric
juice production
secretin – small intestine,
stimulates pancreas to
release buffer (sodium
bicarbonate)
cholecystokinin (CCK) –
small intestine, triggers
release of bile from gall
bladder and enzymes from
the pancreas
enterogastrone – small
intestine, assists in fat
hydrolysis by stopping
peristalsis when fat rich
acid chyme reaches the
duodenum
Mammalian digestion, III cont.
Mammalian digestion, VI
• Large intestine (colon) – site of water
absorption
• Cecum
• Appendix
• Feces
• Rectum/anus
Evolutionary adaptations
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Dentition: an animal’s assortment of teeth
Digestive system length
Symbiosis
Ruminants