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Digestive System
Introduction
• Universe Within
• http://www.cbsnews.com/video/watch/?id=2072234n
Celiac Disease
Healthy Cecum
Crohns Disease
Organs of the Digestive System
Figure 14.1
Digestive System: Functions
• Oral Cavity: transforms food to bolus
• chemical digestion – action of salivary amylase on starches
• physical digestion - chewing
• Pharynx: common passageway for food and air
• Esophagus: conducts food by peristalsis to stomach
• Stomach: chemical and physical digestion
• food enters stomach through esophageal sphincter and
exits through the pyloric sphincter
• contains rugae (folds which help mash up food)
• Produces HCl and pepsin
• food is called chyme after it has been in stomach
Digestive System Functions
Small intestine
• surface area is increased greatly by the microvilli,
villi and circular folds for maximum absorption;
extends from the pyloric sphincter to the ileocecal
valve
• Duodenum: 25 cm long
• Jejunum: 2.5 meters long
• Ileum: 3.6 meters long
Digestive System Parts
Large intestine
• primarily for water absorption
• Cecum
• Appendix
• Colon (ascending, transverse and descending)
• Contains haustra (pocket-like sacs)
• Sigmoid Colon
• Rectum
• Anal canal
• Anus
Accessory Organs
• Salivary glands (aid in chemical digestion)
• Produce saliva which moistens and binds food
together into a mass called the bolus
• Contains the enzyme salivary amylase which starts
process of starch digestion in the mouth
• Three pairs
• Parotid (inflammation of this is called mumps)
• Submandibular
• Sublingual
• Teeth (mechanical digestion)
• Carries out mastication
Accessory Organs
• Pancreas (aids in chemical digestion)
• Produces enzymes for digestion
• secretes enzymes into the duodenum in an
alkaline fluid that helps neutralize acidic chyme
from stomach
• Liver (aids in chemical digestion)
• Produces bile which emulsifies fats in the
duodenum so enzymes can act on them
• Gall Bladder
• Stores and concentrates bile