human digestive system. the digestive system purpose of the digestive system: breaks down food into...
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Human digestive system
The Digestive System
Purpose of the Digestive system:• Breaks down food into substances that cells can absorb
and use.
How is food digested?– Breaking down of food into smaller piece– The mixing of food– Movement through the digestive tract– Chemical breakdown of the large molecules of food
into smaller molecules
Nutrition Process by which organisms obtain and utilize their food.
There are two parts to Nutrition:1. Ingestion- process of taking food into the digestive system so that it may be hydrolized or digested.2. Digestion- the breakdown of food (either chemically or mechanically) in order to utilize nutrients
Types of Nutrients • Micronutrients- vitamins, minerals, & water
• Macronutrients- proteins, lipids, carbohydrates, etc…
Mouth• Mechanical digestion - teeth• Chemical digestion – saliva• Chewing mixes the food with
saliva, from salivary glands around the mouth and face, to make it moist and easy to swallow = BOLUS
• Enzymes in the saliva begin digestion of carbohydrates.
• Epiglottis – flap of cartilage that blocks trachea when swallowing
Esophagus
• Muscular tube• It moves food by waves
of muscle contraction called peristalsis.
• Physically moving the food along to the stomach.
• Mechanical Digestion
Stomach• The stomach lining
produces strong digestive juices (HCl, pepsin)– chemical digestion
• These create chemical reactions in the stomach, breaking down and dissolving its nutrients = CHYME
• Digests proteins and fats in the stomach
• Peristalsis = mechanical digestion
Small Intestine• Enzymes continue the
chemical reactions on the food – chemical digestion
• The nutrients are broken down small enough to pass through the lining of the small intestine, and into the blood (diffusion).
• Digests proteins, fats, and carbohydrates.
• Peristalsis = mechanical digestion
Absorption by Small Intestines• Absorption through villi & microvilli
– finger-like projections– increase surface area for absorption
VILLI
Pancreas
• Accessory organ• Food does not go
through the pancreas• Produces chemicals to
help break down macromolecules = chemical digestion
• Also produces insulin = helps control blood sugar levels
Liver
• Produces bile to help digest fat – Mechanical Digestion, fats are broken into smaller “fat globules”
• Bile is stored in the Gall Bladder and released into the small intestine
Large intestines (colon)
• Function– re-absorb water – (NO DIGESTION)
• use ~9 liters of water every day in digestive juices
• > 90% of water reabsorbed– not enough water absorbed
» diarrhea – too much water absorbed
» constipation
Large Intestine• Solid materials pass
through the large intestine.• These are undigestible
solids (fibers).• Water is absorbed.• Vitamins K and B are
reabsorbed with the water.• Rectum- solid wastes exit
the body.
You’ve got company!• Living in the large intestine is a community
of helpful bacteria– Escherichia coli (E. coli)
• produce vitamins – vitamin K; B vitamins
• generate gases– by-product of bacterial metabolism – methane, hydrogen sulfide
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