chapter 41 animal nutrition. nutritional requirements undernourishment: caloric deficiency...
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• Chapter 41
Animal Nutrition
Nutritional requirements• Undernourishment: caloric
deficiency• Overnourishment (obesity):
excessive food intake• Malnourishment: essential
nutrient deficiency• Essential nutrients: materials
that must be obtained in preassembled form
• Essential amino acids: the 8-10 amino acids that must be obtained in the diet (Arginine, Histidine – Infants)
• Essential fatty acids: unsaturated fatty acids
• Vitamins: organic coenzymes
• Minerals: inorganic cofactors
Food types/feeding mechanisms• 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)
Overview of food processing• 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
Mammalian digestion• 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
• Oral cavity•salivary amylase •bolus
• Pharynx•epiglottis
• Esophagus• Stomach
•gastric juice•pepsin/pepsinogen
(HCl) •acid chyme•pyloric
sphincter
Figure 41.3 Homeostatic regulation of cellular fuel
STIMULUS:Blood glucose
level risesafter eating.
Homeostasis:90 mg glucose/100 mL blood
STIMULUS:Blood glucose
level dropsbelow set point.
When blood glucose level rises, a gland called the pancreas secretes insulin,a hormone, into the blood.
1
Insulin enhances the transport of glucose into body cells and stimulates the liver and muscle cells to store glucose as glycogen. As a result, blood glucose level drops.
2
When blood glucose level drops, the pancreas secretes the hormone glucagon, which opposes the effect of insulin.
3
Glucagon promotes the breakdown
of glycogen in the liver and
there lease of Glucose into the blood,increasing
blood glucose level.
4
Figure 41.19 The duodenum
Liver Bile
Acid chyme
Stomach
Pancreatic juice
Pancreas
Intestinaljuice
Duodenum of small intestine
Gall-bladder
Mammalian digestion
• Hormonal Action:• Gastrin food---> stomach
wall ---> gastric juice• Enterogastrones
(duodenum)• 1-Secretin
acidic chyme---> pancreas to release bicarbonate
• 2-Cholecystokinin (CCK) amino/fatty acids---
> pancreas to release enzymes and gall bladder to release bile
• Large intestine (colon)• Cecum• Appendix• Feces• Rectum/anus
Figure 41.22 Hormonal control of digestion
Amino acids or fatty acids in the duodenum trigger the release of
cholecystokinin (CCK), which stimulates the release of digestive
enzymes from the pancreas and bile from the gallbladder.
Liver
Gall-bladder
CCK
Entero-gastrone
Gastrin
Stomach
Pancreas
Secretin
CCK
Duodenum
Key
Stimulation
Inhibition
Enterogastrone secreted by the duodenum inhibits peristalsis and acid secretion by the stomach, thereby slowing digestion when acid chyme rich in fats enters the duodenum.
Secreted by the duodenum, secretin stimulates the pancreas to release sodium bicarbonate, which neutralizes acid chyme from the stomach.
Gastrin from the stomach recirculates via the bloodstream back to the stomach, where it stimulates the production of gastric juices.
Mammalian digestion• Small intestine •duodenum •bile• Intestinal digestion: a-carbohydrate b-protein c- nucleic acid
d-fat
Mammalian digestion• Villi / microvilli• Lacteal (lymphatic)• Chylomicrons (fats mixed with cholesterol)• Hepatic portal vessel
Evolutionary adaptations• Dentition: an animal’s assortment of teeth• Digestive system length• Symbiosis• Ruminants
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