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What is Digestion?
The breaking down of food.
- Big food parts into smaller ones (mechanical)– Involves muscles and nerves
- Big nutrients into smaller ones (chemical)– Involves acid, enzymes, and hormones
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What is an Enzyme?
Protein that catalyze metabolic reactions,and are necessary for most biochemical reactions to occur.
Examples include: amylase for carbohydrate, protease for protein, and lipase for Lipids/Fat.
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Digestive enzymes specifically break down
food substances.
Examples include: amylase for carbohydrate, protease for protein, and lipase for Lipids/Fat.
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What is a Hormone?
Chemicals produced by cells (typically in an endocrine gland), and are secreted, then affect the behavior of cells at distal sites in the body.
Examples of hormones indigestion include:cholecystokinin and secretin.
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Mechanical digestion:
chewing (mastication)
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Chemical digestion:
saliva(lubrication) and amylase (breaks down digestible carbohydrate)
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What is a bolus?
ball of food in the esophagus
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Peristalsis is a
muscular wave action that occurs throughout the intestinal tract. It is controlled by the central nervous system and facilitates excretion by propelling food stuff through the body.
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The Esophagus is where
Peristalsis begins.
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The Stomach is a
muscular organ & storage reservoir.
• Mechanically digests food by mixing & churning.
• Chemically digests food with acid and some enzymes (pepsin).
• Here, the bolus becomes chyme.
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The Small Intestine is where absorption occurs at
Sites of Absorption:
Duodenum: many nutrients
Jejunum: Many nutrients
Colon (large Intestine): water
Ileum: only a selected nutrients
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Why do we signal the accessory organs?
for assistance in digesting the food stuff.
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How do we signal our accessory organs?
By hormones.
- The cells of the intestinal wall produce the hormones cholecystokinin and secretin which enter the blood stream and signal the accessory organs.
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The Accessory Organs
• The Liver– Makes bile
• The Gallbladder– Stores bile
• The Pancreas
– Makes enzymes for the chemical digestion of carbohydrates, proteins,and fats
– Makes sodium bicarbonate to neutralize stomach acid
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The Function of Bile
Emulsifier
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Mechanisms of Absorption
Passive (Simple) Diffusion (Transport):
Nutrients like water & lipid byproducts pass freely across membranes via a concentration gradient.
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Mechanisms of Absorption
Facilitated Diffusion (Transport):
Nutrients like water soluble vitamins diffuse across membranes using a specific/selective transport proteins.
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Mechanisms of Absorption
Active Transport:
Nutrients like glucose & amino acids move across membranes against a concentration gradient using a specific/selective transport protein & energy/ATP.
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Transportation of Nutrients
• Blood vessels: water soluble nutrients
• Lymphatic vessels: fat soluble nutrients
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Cellular Storage
- • Short term
- • Intermediate
- • Long term
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Catabolic reactions:
Breaking down(things get smaller). Involve hydrolysis reactions. Are degrading or destructive in nature.
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Anabolic reactions:
Building up (things get bigger). Involve condensation reactions.Are synthesizing or constructive in nature.
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Homeostasis:
The balance of catabolic and anabolic reactions in a person so a relatively stable internal environment or equilibrium is achieved.
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Excretion
The Kidney:
Water and water soluble waste.
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Excretion
The Skin:
Water and water soluble waste.
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Excretion
The Lung:
Carbon dioxide and water.
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Excretion
The Colon (large intestine):
Water is removed and waste (bacteria, fiber, sloughed cells, and undigested food) is compacted.
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