Digestion

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Digestion

• Anatomy Physiology II
• Tony Serino, Ph.D.
• Biology Department
• Misericordia University

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Digestion

• The reduction through mechanical and chemical
  means (hydrolysis) of complex food substances
  into simple monomers and their absorption into
  the internal environment.

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Functions of Digestive System

• Motility(Propulsion)
• Ingestion food enters tract
• Mastication -chewing
• Deglutition -swallowing
• Transportation through tract (peristalsis)
• Mixing
• Egestion (Defecation)
• Secretion
• Endocrine and Exocrine secretions
• Digestion
• mechanical and chemical breakdown of food
• Absorption
• Passage of food particles from external to the
  internal environment

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Major Organs of System
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Accessory Organs
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GI Tract Development
Post-gastrula
Late Gastrulation
Pylorus
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Basic Histology of Digestive Tract
(Auerbachs)
(Meissners)
(LOCI)
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Peristalsis
Tube Movements
Segmentation
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Retroperitoneal Position
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Peritoneal Cavity
Lesser Peritoneal Cavity
Greater Peritoneal Cavity
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Mesenteries
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Mesenteries
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Control of Overall GI Tract Activity
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Oral Cavity (sagittal)

• Mucosa Stratified Squamous epithelia
• Muscularis Skeletal muscle overlying bone
• Functions
• Ingestion
• Mastication
• Hydration of food
• Begins chemical digestion
• Formation of bolus

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Oral Cavity (anterior)
(Red Margin)
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Tongue
Functions mixing, speaking, and
swallowing Intrinsic and extrinsic muscles
Foliate papillae
Three layers of skeletal muscle.
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Major Salivary Glands
Secrete saliva mixture of water, mucus,
electrolytes, antibodies and enzymes. Enzyme is
salivary amylase which breaks down starches.
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Teeth
Function mastication (chewing and grinding of
foodinto a paste consistency)
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Primary Dentition
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Adult (Permanent) Dentition
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Tooth Anatomy
Odontoblasts secrete dentinAmeloblasts secrete
enamel
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Pharynx
Function deglutitionMucosa Str.
SquamousMuscularis Skeletal
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Esophagus

• Function Deglutition
• Two sphincters upper and lower esophageal
  sphincters (lower is physiological only)
• Retropleural position (therefore, covered by
  adventitia)
• Mucosa stratified squamous with many mucus
  glands (esophageal glands)
• Muscularis changes from skeletal to smooth
  muscle

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Esophagus Histology
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Deglutition (Swallowing)
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Deglutition (contd)
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Stomach (cadaver)

• J-shaped muscular pouch
• Receives bolus and produces chyme
• Liquefies food by mixing it with HCl and vigorous
  churning

• Low pH stops amylase activity, but secretes
  pepsinogen (pepsin) that begins break down of
  proteins
• Absorbs little except imbibed water,
  electrolytes, and some drugs (ie. alcohol and
  aspirin)

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Stomach Anatomy

• Mucosa
• simple columnar folded into rugae
• No villi
• Openings leading to gastric pits and glands
• Muscularis
• Has three layers

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Rugae of Stomach
Temporary longitudinal foldings of the mucosa
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Stomach Histology
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Gastric Gland
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Regulation of Gastric Juice
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Gastric Emptying
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Gastric Emptying
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Inhibition of Gastric Emptying
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Small Intestine
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Small Intestine
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Duodenum and Accessory Organs
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Small Intestine Structures to Increase Surface
Area
Plica Circularis
Villi
Long Length of SI
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Small Intestine Histology
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Histology Changes in Intestine
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Villi Histology
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Large Intestine (x-ray)
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Large Intestine (Colon)
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Large Intestine Histology
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Anal Canal
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Defecation Reflex
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Upper Abdominal XS
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Liver
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Liver (inferior surface)
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Liver Lobule
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Bile Ducts
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Bile and Pancreatic Ducts
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Duodenal Papilla
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Secretion of Bile
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Pancreas
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Pancreas Histology
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Pancreatic Acinus
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Exocrine Secretions of Pancreas
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Secretion of Pancreatic Juice
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Micelle Formation (Emulsifying Fat)
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(No Transcript)
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Fatty Acid Absorption
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Amino Acid Absorption
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Food Digestion Summary
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Food digestion Summary