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Nutritional requirementsAnimals are heterotrophs
need to take in foodWhy? fulfills 3 needs…
fuel = chemical energy for production of ATP raw materials = carbon sources for biosynthesisessential nutrients = substances animals cannot
make themselves• elements (N, P, K, Fe, Na, K, Ca, etc.), NAD, FAD, etc.
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Energy budget
food intake
ATPproduction
biosynthesis
• basal (resting) metabolism
• activity• temperature
regulation
• growth• reproduction
{{
storage• glycogen• fat{
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A body functions properly only when the needs of the organisms (water, food, heat, oxygen and pressure) remain within the narrowly required limits.
Homeostasis: The tendency to maintain a stable internal environment.Ex: Furnace and air conditioner unit to maintain
constant temperature
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Negative feedback mechanism:Negative feedback occurs when an increase in
some factor is sensed and is lowered
A response the body has to an occurrence that disturbs the homeostasis of the body. As the body reacts to that occurrence and moves closer to homeostasis, the receptors are shut down, thus causing fewer effectors to produce a product that’s needed to bring the body back to homeostasis, in the end having a “negative” effect on the production. The purpose of this is to stop overproduction or overreaction.
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Homeostatic mechanism in regulating body temperature:
Shivering – in a cold environment muscles will contract involuntarily producing heat
Sweating - in an overheated environment the brain triggers a changes that promotes the increased loss of body heat
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Managing glucose levelsHuman body regulates the use & storage of
glucose, a major cellular fuel insulin reduces blood glucose levels
when glucose levels rise above set point, pancreas secretes insulin
promotes transport of glucose into cells & storage of glucose as glycogen in liver & muscle cells
dropping blood glucose levelsglucagon increases blood glucose levels
when glucose levels drop below set point, pancreas secretes glucagon
promotes breakdown of glycogen & release of glucose into the blood
increasing blood glucose levels Show PDF of insulin
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• Regulation: Maintaining Homeostasis Balancing glucose levels in blood
pancreas
pancreas
insulin
glucose storage
glucose uptake
glucose release
depress appetite
stimulatehungerglucagon
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Essential Nutrients
What happens if an animal’s diet is missing an essential nutrient?deficiency diseases
scurvy — vitamin C (collagen production)rickets — vitamin D (calcium absorption)blindness — vitamin A (retinol production)anemia — vitamin B12 (coenzyme function)
kwashiorkor — protein deficiency
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DigestionThe reduction of large food molecules into
smaller absorbable units and conversion of insoluble units into soluble ones.
This is accomplished by mechanical action, chemical and enzymatic action.
Enzymes are synthesized by cells in the mouth, stomach, pancreas and small intestine
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Normally 92- 95% of a diet is digested and absorbed, but the process varied for each nutrient
http://www.ama-assn.org/ama/pub/category/7155.html
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Types of digestive action
MechanicalMovement of the teeth grinding the food in the
mouth
ChemicalChanging the food molecules into new and
different moleculesLipids Lipase Fatty acids + glycerol
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Alimentary Tract
Alimentary canalA muscular tube about 9 meters long
Appendage organs include:Liver, biliary tree and pancreas
Extends from the mouth to the anus
Receives food . . . Digestion/absorption occurs . . .transport to cells . . .excretion of waste
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Diagram of Alimentary canal
Peristalsis – propelling movements which are a forward motion that is wavelike
Peristalsis pushes tubular contents ahead of it through the alimentary canal
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MouthTeeth mechanically grind and crush food
Saliva moistens and binds food mass
Salivary amylase begins digestion of starch
Chewed food mass bolus
Passes from mouth into esophagus
Movement is controlled by peristalsis
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Approximately 1.5 liters of saliva are produced daily by salivary glands (~ 6 cups) Figure 12.1
Amylase is a digestive enzyme It splits starch and glycogen (both carbohydrates) into
disaccharides via hydrolysis
Mucus binds food particles and acts as a lubricant in swallowing
Esophagus – straight tube that provides a passageway between the pharynx and stomach
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Stomach
Chemical digestion begins in the middle of the stomach mixing food with gastric juices
Gastric juices contain HCl, intrinsic factor, pepsinogen, gastric lipase & mucus
Food becomes semi-liquid chyme (50% water)
Stomach is emptied in 1 – 4 hoursSphincter–valves at either end of stomach
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The lining of the stomach is covered with numerous small holes. These are the openings of gastric pits which extend into the mucosa forming gastric glands.
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Stomach helps to initiate the digestion of proteins, but also helps speed up the digestion of carbohydrates and fatsPepsin is the most important digestive enzyme
in the stomachPepsin is a protein-splitting enzyme
It carries on a limited amount of absorption
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The pyloric sphincter (pylorus) is a muscle that acts as a valve to prevent regurgitation of food from intestines back into the stomach
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Pancreas
Functions as an endocrine glandReleases hormones
Functions as an exocrine glandSecretes digestive juicesPancreatic juices move into the intestine
(duodenum)
Contains enzymes that digest carbohydrates, fats, proteins and nucleic acids
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Viewing the digestive system in the anatomical position, the pancreas is found in under the stomach in the left hypochondriac & epigastric regions
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Liver
Located below the diaphragm in the right hypochondriac and epigastric regions of the abdominal area.
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The liver metabolizes carbohydrates lipids and proteins
Stores glycogen, vitamins A, D, B12 and iron
Filters blood Detoxifies bloodSecretes bileAn Introduction to the Liver – PDF File
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Other functions of the liver Producing quick energy when it is needed; Manufacturing new body proteins; Preventing shortages in body fuel by storing certain vitamins, minerals, and
sugars; Regulating transport of fat stores; Regulating blood clotting; Aiding in the digestive process by producing bile; Controlling the production and excretion of cholesterol; Neutralizing and destroying poisonous substances; Metabolizing alcohol; Monitoring and maintaining the proper level of many chemicals and drugs in
the blood; Cleansing the blood and discharging waste products into the bile; Maintaining hormone balance; Serving as the main organ of blood formation before birth; Helping the body resist infection by producing immune factors and by
removing bacteria from the bloodstream; Regenerating its own damaged tissue; and Storing iron.
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Bile - Yellowish, green liquid made of bile salts, bile
pigments, water, cholesterol and electrolytes
Bile salts aid the digestive enzymes and enhance the absorption of fatty acids and fat-soluble vitamins
Bile salts act as emulsifiers, breaking up fat into droplets, allowing lipases to digest them better 5.1.3 state source of one lipase – substate,
source and optimum pH
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Bile is stored in the gall bladder until a hormone stimulates its release into the small intestines
http://www.foxriverwatch.com/liver_hepatic_damage_pcbs_1a.html
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Small Intestine
Approx. 20 -25 feet long with villi and microvilli for a total surface area of 25 sq meters
3 areas:DuodenumJejunum Ileum
Most digestion occurs in the duodenumMost absorption occurs in the jejunum and ileum
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The intestines are lined with villi Increase the surface area of the intestinal lining Increase the absorption of digestive productsCapillaries carry away absorbed products from villi
Nutrients are absorbed by several meansSimple diffusion (higher to lower concentration area)
Facilitated diffusion (Against the gradient using channel or carrier proteins)
Active transport (diffusion with ATP)
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As chyme enters duodenum it stimulates the release of pancreatic juices and mixes with enzymes from the pancreas and small intestine as well as with bile, fluid and bicarbonates
All the gastric, small intestinal secretions and pancreatic secretions are controlled by the nervous system and by hormones
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Digestive enzymes in sm. intestine
Enzymes are specific to a particular substrate
ProteinsPeptidases break peptides into amino acids
LipidsLipases break lipids into glycerol and fatty acids
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Carbohydrate Digestion
Begins in mouth with salivary amylase
Halted by hydrochloric acid
Digestion mostly occurs in small intestine by pancreatic amylase
Passes through intestinal wall in monosaccharide form (ex: glucose)
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They quickly move through the digestive system
Some carbohydrates cannot be digested by humans and are excreted
They provide short term energy
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Protein DigestionBegins in stomach by proteolytic enzymes
Most of digestion takes place in the duodenum by pancreatic and intestinal enzymes: Protein hydrolysis
Final phase occurs in the “brush border” of the microvilli
Absorbed in the amino acid form
Allergic reactions can occur when intact proteins pass through intestinal wall
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Proteins move through digestive system 2nd fastest after carbohydrates
Once protein is broken down into amino acids, these are reassembled into 1º,2º,3º and 4º proteins the body needs:Hemoglobin – blood proteinAlbumin – in plasma; aids in blood clottingFibrinogen – blood clotting agent
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Lipid Digestion
Begins in stomach with gastric lipaseMajor digestion occurs in small intestineBile and action of stomach/small intestine
break down large globules into smaller pieces
Lipase breaks down particles into fatty acids.
Cholesterol and fat soluble vitamins follow similar process
Lipids move slowly through the digestive system
They are stored as long term storage in the form of adipose tissue
http://www.sunyniagara.cc.ny.us/val/adipose2.html
http://www.gen.umn.edu/courses/1135/lab/kidneylab/kidneylab.html
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Vitamins, Minerals and Fluids
Absorbed in the intestineEight liters of fluid are passed back and
forth across the membrane of small intestine to keep nutrients in solution
Vitamins and water pass unchanged from small intestinal wall into the blood stream
Absorption of mineral occurs in stages in small intestine
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Large Intestine
Includes:Ascending colon transverse colondescending colonsigmoid colonrectum
http://www.fruit-eze.com/education/colon/
Large intestine primarily absorbs water, electrolytes and some vitamins
Bacteria break down undigested materialFormation and absorption of vitamin KFormation and excretion of waste products
http://www.fujinon.com/product/medical/ed0114.htm
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Little digestion now occurs as it is mostly completed by this time.
Large intestine are about 5 feet long
Mixing movement and peristalsis occur but are much slower here.
Peristalsis occurs only 2 to 3 times/day.
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