The DIGESTIVE System

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The DIGESTIVE System
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Digestion defined

• Breakdown of food into useable nutrients
• Two kinds
• Mechanical
• Chemical

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Chemical Vs Mechanical Digestion

• Chemical Enzymes break down for
  absorption--ENZYMES
• Mechanical broken down into smaller
  parts--MASTICATION AND MACERATION

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Alimentary canal

• Tube food passes through
• Begins at mouth - ends with anus
• Food is chewed
• Bolus created
• Bolus swallowed

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Pharynx

• Bolus moves into pharynx
• fancy word for throat
• has three parts
• Nasopharynx
• Oropharynx
• Laryngopharynx

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Esophagus

• 8-12 inches long
• Smooth muscle contractions called
• Peristalsis-rhythmic
• Cardiac (aka Gastroesophageal) sphincter
• Has no mucous membrane to protect from Hcl from
  stomach

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Stomach

• J-shaped
• 3 sets of muscle in different directions
• Hcl chemical breakdown
• Pepsin begins protein disgestion
• Contain rugae to increase surface area
• Change bolus into chyme
• Mucus protects stomach lining

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Small intestine

• 3 parts
• Duodenum--most chemical digestion takes place
  here
• Jejunum-absorption continues
• Ileum absorption continues
• 15-22 ft long
• Absorbs some of the water in food what you
  drink

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Villi

• Nutrients are absorbed through structures called
  villi

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Large intestine

• called the colon
• Main function water absorption Vit K absorption
• Begins with cecum-contains lymphatic organ called
  appendix
• Ascending colon

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Large intestine

• Ascending colon
• Transverse colon-makes hunger sounds
• Descending colon
• Sigmoid colon
• Rectum
• Anal canal
• Anus

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Accessory organs

• CONTRIBUTE to digestion process
• NOT part of the canal or tube
• Food DOES NOT pass through them

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Tongue and teeth

• Teeth break food down into smaller pieces
• Tongue moves food to the back of throat

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Parts of a tooth

• Crown exposed portion above gum line
• Neck between crown root
• Gingivae-gums
• Root one to three-- embedded in mandible
  maxillae

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Parts of a tooth

• Enamel outermost part, protects from wear
  tear
• the hardest substance in the body
• Dentin calcified connective tissue
• Gives tooth its basic shape rigidity

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Parts of a tooth

• Pulp Cavity large cavity enclosed by
  dentin--filled with pulp
• Cementum a bone-like substance covers--dentin
  of roots

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Parts of a tooth

• Periodontal Ligament
• an area of dense fibrous connective tissue
• anchors teeth in position
• serves as a shock absorber when chewing

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Salivary glands

• Saliva is
• Mostly water
• Enzymes that digest carbsAmylasebreaks starch
  into maltose
• Soften and moisten food

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Salivary glands

• 6 total--3 pair
• Parotid, submandibular, and sublingual

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Liver and Gall Bladder

• Liver makes bile
• Bile is stored in gall bladder (sac)
• Bile breaks down fats--emulsification
• Secreted as it is needed
• Eliminated through intestines

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Pancreas

• Located posterior to stomach
• Secretes enzymes to chemically breakdown fats,
  carbs, and proteins
• Increases pH of chyme
• Pancreatic juicethru pancreatic ductthru
  heptopancreatic sphincter

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Mastication

• Chewing--makes bolus
• Teeth mechanically break down food
• Food is mixed with saliva

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Deglutition

• Swallowing
• Tongue pushes food to back of throat
• Oropharynx--second part of throat
• Smooth Muscles contract causing peristalsis
• Voluntary

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Peristalsis

• General term for wave-like contractions in
  esophagus and intestines
• Rhythmic smooth muscle contractions

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Maceration

• Stomach contracts and Bolus mixed with gastric
  juices and Hcl until it is liquid-like
• Bolus is changed to chyme
• Empties through pyloric sphincter

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Segmental contraction

• Each segment of small intestine contracts
• Helps mix bile and pancreatic juices with chyme
• Smooth Muscle contractions peristalsis in each
  segment

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Absorption

• Nutrients absorbed in jejunum and illeum
• Some nutrients water absorbed thru stomach
• Some water absorbed through small intestine
• Most water absorbed through large intestine

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Haustral churning

• Each segment in large intestine is called a
  haustra
• Smooth muscle contractions move contents along
  (type of peristalsis)
• Water is absorbed in large intestine

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Defecation

• Elimination of material that is undigestible
• Plant fiber--necessary for health of the
  intestines
• Formation of feces and elimination of feces

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Nutrients are broken down in different places in
digestive system

• Carbohydrates
• Begin digestion in mouth with enzyme AMYLASE
  from salivary glands
• Amylase breakdown continues in stomach
• Finish breakdown in duodenum (pancreatic juice)

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Fats

• Fats begin mixing with gastric juices in stomach
• Bile from gall bladder goes into small intestine
  to break them down
• Pancreas secretes enzymes (lipase) to finish
  chemical breakdown

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Proteins

• Begin mixing with pepsin in stomach
• Finish with secretions from pancreas into duodenum

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Digestion system End