Transcript Chapter 41

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Chapter 41 ~
Animal Nutrition
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Food types/feeding mechanisms
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Opportunistic
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Herbivore: eat autotrophs
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Carnivore: eat other animals
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Omnivore: both
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Feeding Adaptations
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Suspension-feeders: sift food
from water (baleen whale)
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Substrate-feeders: live in or on
their food (leaf miner)
(earthworm: deposit-feeder)
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Fluid-feeders: suck fluids from a
host (mosquito)
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Bulk-feeders: eat large pieces of
food (most animals)
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Homeostasis
Digestion Example
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Glucose Regulation - 90mg glucose/100ml blood
– Levels rise = insulin produced to move glucose into
cells (muscle/liver)
– Levels drop = glucagon produced stimulates release of
glucose from muscle/liver
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Undernourishment: caloric deficiency
Overnourishment (obesity): excessive food intake
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Nutritional requirements
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Malnourishment: essential
nutrient deficiency
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Essential nutrients:
materials that must be
obtained in pre-assembled
form
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Essential amino acids: the 8
amino acids that must be
obtained in the diet
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Essential fatty acids:
unsaturated fatty acids
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Vitamins: organic
coenzymes
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Minerals: inorganic
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Overview of food processing
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1-Ingestion: act of eating
2-Digestion: process of food break down
– 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
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Mammalian digestion, I
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Peristalsis: rhythmic waves of contraction by smooth muscle
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Sphincters: ring-like valves (smooth muscle) that regulate passage of
material
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Accessory glands: salivary glands; pancreas; liver; gall bladder
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The Oral Cavity
Lips and Cheeks, composed of skeletal
muscle, form boundary.
 Teeth cut, smash, and grind food into smaller pieces with a
larger surface area.
 Salivary Glands release saliva (more than one liter per day!)
after being stimulated.
 Parotid
 Submandibular
 Sublingual
 Saliva contains mucin (a slippery glycoprotein), antibacterial
agents, and salivary amylase (breaks down starch and glycogen)
 Tongue is responsible for tasting and shaping food into a ball
shape called a bolus. Also a skeletal muscle!
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The Pharynx and Esophagus
The Pharynx
- Opens to Esophagus and Trachea (windpipe)
- The Glottis, visible as the “Adam’s Apple”, is
covered by a flap (epiglottis) to prevent passing
food from going down the “wrong pipe”.
The Esophagus (25 cm long). [Lined with stratified squamous]
- controls the passage of food from the pharynx
to the stomach by Peristalsis, rhythmic waves
caused by muscle contractions
- Esophageal Sphincter is a ring shaped stopper
between the pharynx and esophagus.
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- Stomach
Folded, elastic and can hold about two liters of food and fluid!
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Gastric juice - secreted by
epithelium that lines stomach
walls.
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Parietal Cells: secrete HCl
making stomach contents pH 1.5
– 3.5
Gastric Pits
Chief Cells: secrete
pepsinogen which become
activated (by removal of small
peptide, exposing active site) by
HCl to become pepsin. Can also
be activated by pepsin.
Mucus coats the stomach wall
for protection, prevents leakage
of chyme between cells,
damaged cells quickly shed and
replaced.
Surface epithelium renewed
every 3-6 days!
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Functions of Hydrochloric
Acid in Gastric Juices
• Acid disrupts extracellular
matrix that keeps cells
together in meat and plant
material
• Kills most bacteria swallowed
with food
• Activates pepsinogen
• Gastric secretions controlled
by hormone  Gastrin.
• Gastrin released by aroma,
sight, thought of food and
by food reaching the
stomach
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Passing through the
Stomach…
- A bolus will come to the
stomach from the esophagus
by way of peristalisis
- The stomach churns and
mixes, and in cooperation
with enzymes, creates acid
chyme
- From here, the chyme goes
through the pyloric
sphincter into the small
intestine.
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Mammalian digestion, III
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Small intestine - hydrolysis and absorption
– •duodenum •bile
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Intestinal digestion: carbohydrate, fat, protein, nucleic acid
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Please notice where each type of molecule is digested
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The Duodenum
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Mammalian digestion - small intestine
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Villi / microvilli- increase absorption (How??)
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Lacteal (lymphatic)
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Chylomicrons (fats mixed with cholesterol)
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Hepatic portal vessel - Blood goes to liver for “processing”
3-6 hrs for
chyme to travel
through sm.
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intestine
Mammalian digestion - Hormones
Regulate running of digestive system
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Hormonal Action:
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Gastrin food---> stomach wall
---> gastric juice
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Enterogastrones (duodenum)
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1-Secretin
acidic chyme --->
pancreas to release bicarbonate
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2-Cholecystokinin (CCK)
amino/fatty acids --->
pancreas to release enzymes
and gall bladder to release bile
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Mammalian Digestion - Large
Intestine (colon)
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Is connected to small intestine at a pouch
called the cecum (aka. Appendix)
Function - reabsorb water from digestion
Movement from paristalsis
• Bacterial flora consume cellulose and produce about
500 ml of dimethyl sulfide, H2, N2, CH4, and CO2;
aka flatus. Also synthesize vitamin K to be used by
liver.
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Rectum - storage/end of colon
Anus - opening
• between voluntary and involuntary
sphincters
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Structural Adaptations
to Diet
- Dentition
1. Carnivores
have large canines
and incisors
2. Herbivores
have small canines
3. Omnivores have
medium sized
everything
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Structural Adaptations Due
to Diet
- Length of
digestive system
1. Carnivore is
smaller
2. Herbivore is
longer due to
cell walls
- Ruminant digestion
– symbiosis
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