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Biology 250: Human Anatomy. Spring 2005 Digestive System. 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

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biology 250 human anatomy

Biology 250: Human Anatomy

Spring 2005

Digestive System

overview of digestive system
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
digestive processes
Digestive Processes
  • Ingestion
  • Propulsion: peristalsis
  • Mechanical Digestion: segmentation
  • Chemical Digestion
  • Absorption
  • Defecation
layers of the alimentary canal
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
layers of the alimentary canal cont
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
the mouth
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
the lips and cheeks
The Lips and Cheeks
  • Lips (Labia)
    • Orbicularis Oris Muscle
    • Red Margin, Labial Frenulum
  • Cheeks
    • Buccinators Muscles
  • The two combined help keep foodbetween teeth, help with speech
the palate
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
the tongue
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
the salivary glands
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
the teeth
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
the pharynx
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
the esophagus
The Esophagus
  • Muscular tube; collapsed when no food
  • Lies posterior to the trachea
    • Epiglottisdirects food into esophagus
  • Joins the stomach at the Cardiac Orifice
    • Gastroesophageal Sphincter
  • GERD
mouth pharynx esophagus
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
the stomach
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
the small intestine
The Small Intestine
  • Body’s Major Digestive Organ
    • Digestion completed, absorption occurs

Subdivisions of Small Intestine

  • Duodenum
  • Jejunum
  • Ileum
the liver
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
the gallbladder
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
the pancreas
The Pancreas
  • Found in the greater curvature of stomach
  • Aids in the digestion of all foods
    • Uses pancreatic juices for food digestion
the large intestine
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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