Biology 250: Human Anatomy

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Biology 250 Human Anatomy

• Spring 2005
• Digestive System

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Overview Of Digestive System

• Alimentary System (Canal)
• Also Gastrointestinal (GI) Tract
• Continuous muscular digestive tube
• Digestion and absorption
• Mouth, pharynx, esophagus, stomach, intestines
• Accessory Digestive System
• Contribute to the digestion of food
• Teeth, tongue, gallbladder, liver, pancreas

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Digestive Processes

• Ingestion
• Propulsion peristalsis
• Mechanical Digestion segmentation
• Chemical Digestion
• Absorption
• Defecation

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Layers of the Alimentary Canal

• Lumen central canal where food is transported
• Mucosa (Mucous Membrane)
• Innermost layer moist epithelial membrane
• Secretion, absorption, protection
• Submucosa just external to mucosa
• Contains blood vessels, nerve fibers
• Gives walls its elastic characteristic

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Layers of the Alimentary Canal (Cont.)

• Muscularis Externa external to submucosa
• Contains smooth muscle
• Inner circular layer, Outer Longitudinal Layer
• Responsible for peristalsis segmentation
• Serosa protective outermost layer
• Composed of connective tissue epithelium

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The Mouth

• Also called oral cavity, buccal cavity
• Oral Orifice anterior opening
• Stratified Squamous Epithelium
• Helps to withstand friction forces
• Only organ involved with Ingestion

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The Lips and Cheeks

• Lips (Labia)
• Orbicularis Oris Muscle
• Red Margin, Labial Frenulum
• Cheeks
• Buccinators Muscles
• The two combined help keep food between teeth,
  help with speech

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The Palate

• Forms the roof of the mouth
• Hard Palate
• Food forced against it by the tongue
• Soft Palate
• Uvula prevents food from traveling to the nasal
  cavity

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The Tongue

• Occupies the floor of the mouth
• Helps to reposition food between teeth
• Occupies the taste buds
• Intrinsic Muscles
• Changes shape of tongue, not position
• Extrinsic Muscles
• Changes position of tongue, not shape

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The Salivary Glands

• Produces Saliva
• Functions of Saliva
• Cleanses the mouth
• Dissolves food chemicals for taste
• Moistens food, aids in bolus formation
• Begins chemical digestion of food

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The Teeth

• Adults contain 32 teeth
• 8 incisors, 4 canines, 8 premolars, 12 molars
• Crown portion exposed above gums
• Covered by enamel (hardest substance in body)
• Root portion embedded in jaws
• Teeth initiate the breakdown of food
• Chewing

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The Pharynx

• Oropharynx, Laryngopharynx
• Common passageway for air food
• Contain two layers of skeletal muscle
• Inner Longitudinal Muscle
• Outer Pharyngeal Constrictor Muscles
• Muscles propel food into the Esophagus

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The Esophagus

• Muscular tube collapsed when no food
• Lies posterior to the trachea
• Epiglottis directs food into esophagus
• Joins the stomach at the Cardiac Orifice
• Gastroesophageal Sphincter
• GERD

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Mouth, Pharynx, Esophagus

• Mastication (Chewing)
• Lips, cheeks, tongue keep food between teeth
• Deglutition (Swallowing)
• Tongue blocks off the mouth
• Uvula rises to block of nasopharynx
• Larynx rises so allow epiglottis to block off the
  trachea and the lower airways

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The Stomach

• Temporary storage tank of food
• Coverts food into creamy paste (Chyme)
• Anatomical Regions of Stomach
• Cardiac Region
• Gastroesopageal Sphincter
• Fundus
• Body
• Pyloric Region
• Pyloric Sphincter
• Greater / Lesser Curvatures
• Gastric Ulcers

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The Small Intestine

• Bodys Major Digestive Organ
• Digestion completed, absorption occurs
• Subdivisions of Small Intestine
• Duodenum
• Jejunum
• Ileum

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The Liver

• Role in digestion is to produce Bile
• Helps to break down fat
• 4 Lobes of the Liver
• Right Lobe
• Left Lobe
• Caudate Lobe
• Quadrate Lobe
• Hepatitis inflammation of liver viral
• Six types A-F

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The Gallbladder

• Rounded structure, connected to liver
• Acts as storage site for bile
• Reason for its green color
• Gallstones crystallization of bile
• Causes tremendous shooting pain in abdomen
• Rx drugs, lasers, surgery

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The Pancreas

• Found in the greater curvature of stomach
• Aids in the digestion of all foods
• Uses pancreatic juices for food digestion

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The Large Intestine

• Larger diameter than small intestine
• Almost half as long as small intestine
• Absorbs water, eliminates waste (feces)
• Large Intestine Subdivisions
• Cecum
• Appendix
• Colon ascending, transverse, descending, sigmoid
• Rectum
• Anal Canal

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