DIGESTIVE SYSTEM

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DIGESTIVE SYSTEM
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GENERAL

• 1st System to Develop
• Tube Within a Tube
• Contents Remain External Until Absorbed Through
  Walls
• Humans are (Anatomical) Omnivores
• Consists of Alimentary Canal/Digestive Tract and
  Accessory Organs

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DIGESTIVE SYSTEM FUNCTIONS

• Ingestion Food Enters Through Mouth
• Digestion Breaking Large Molecules into
  Smaller, Absorbable Molecules
• Mechanical (Physical)
• Chemical (Enzymatic)
• Absorption Passage of Molecules Through GI
  Tract Wall into Blood or Lymph
• Egestion Elimination of Non-digestible
  Substances Through Anal End

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DIGESTIVE SYSTEM ORGANIZATION

• Alimentary Canal (Gastrointestinal or Digestive
  Tract)
• Mouth, Pharynx, Esophagus, Stomach, Small
  Intestine, Large Intestine
• Lumen is part of External Environment
• Accessory Organs
• Salivary Glands
• Liver
• Gall Bladder
• Pancreas

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ALIMENTARY CANAL HISTOLOGY

• Mucosa
• Innermost, Surrounds Lumen
• Mucous Membrane
• Secretes, Absorbs, Protects
• Submucosa
• Below Mucosa
• C.T., Blood Vessels, Lymphatics, Nervous Tissue

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ALIMENTARY CANAL HISTOLOGY continued

• Muscularis (Externa)
• Smooth Muscle
• Inner, Circular, ? Diameter of Lumen
• Outer, Longitudinal, ? Diameter of Lumen
• Propels Substances
• Serosa (Visceral Peritoneum)
• Outermost
• Serous Membrane, Lubricates
• Adventitia outside of Ventral Body Cavity

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MOVEMENT OF FOOD

• Peristalsis - Wave-like Contraction of Circular
  Longitudinal Smooth Muscle for Propulsion
• ANS
• Stimulated by Parasympathetic
• Inhibited by Sympathetic

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ALIMENTARY CANAL ORGANIZATION

• MOUTH
• Oral (Buccal) Cavity Functions in Ingestion
• Digestion
• Mechanical (Teeth, Tongue)
• Chemical (Saliva Begins Carbohydrate Digestion)
• Cheeks
• Hard Palate (Bony)

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MOUTH continued

• Soft Palate (Muscular)
• Blocks Nasopharynx During Swallowing
• Uvula - Dangling end
• Tongue
• Frenulum Anchors to Floor of Mouth
• Skeletal Muscle Tissue covered with Mucosa
• Papillae with Taste Buds
• Lingual Tonsil Sublingual Gland

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MOUTH continued

• Teeth
• Vestibule Space between Teeth Lips
• Two Sets Deciduous (20) Permanent (32)
• Four Types
• Incisors Biting
• Canines Tearing Grasping
• Bicuspids Molars - Grinding

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ALIMENTARY CANAL ORGANIZATION continued

• PHARYNX
• Connects Oral Cavity, Nasal Cavity, Larynx
  Esophagus
• Passageway for Food, Water, Air
• Muscular Walls (Swallowing)
• 3 Regions Nasopharynx, Oropharynx, Laryngopharynx

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ALIMENTARY CANAL ORGANIZATION continued

• ESOPHAGUS
• Collapsible, 10 Tube
• Connects Pharynx Stomach
• Lies Posterior to Trachea
• Lower Esophageal Sphincter Prevents Stomach
  Contents from Entering Esophagus
• Passes Through Neck ? Thoracic Cavity ?
  Esophageal Hiatus ? Abdominal Cavity

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ALIMENTARY CANAL ORGANIZATION continued

• STOMACH
• J-Shaped Organ, Inferior to Diaphragm
• Functions
• Storage
• Digestion (Mechanical Chemical)
• Protein Digestion Begins here
• Absorption of Water, Alcohol, Drugs

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STOMACH continued

• Enters as Bolus Mixture of Food Saliva
• Leaves as Chyme Milky Mixture of Partially
  Digested Food Gastric Juices

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STOMACH continued

• 4 Regions
• Cardia Connects with Esophagus
• Body Principal, Main Part
• Fundus Superior, Bulge, Food Storage
• Pylorus Terminal Part, Pyloric Sphincter
• 2 Curves
• Greater Curvature
• Lesser Curvature

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STOMACH continued

• Wall Modifications
• Rugae Expandable Folds, Accommodate More Food
• Oblique Muscle in Muscularis
• Gastric Glands in Mucosa
• Mucus Cells (Protective Coating)
• Parietal Cells (HCl, pH 2)
• Chief Cells (Pepsinogen HCl ? Pepsin
  (Proteolytic)

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ALIMENTARY CANAL ORGANIZATION continued

• SMALL INTESTINE
• Site of Most Chemical Digestion
• Site of 90 of Absorption
• Monosaccharides ? Blood
• Amino Acids ? Blood
• Fatty Acids Glycerol ? Lymph

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SMALL INTESTINE continued

• 3 Subdivisions
• Duodenum
• First 10-12
• Ampulla of Vater Receives Secretions from Liver
  Pancreas
• Bile through Common Bile Duct
• Pancreatic Juice through Pancreatic Duct
• Jejunum Middle Length
• Ileum Last, Joins with Large Intestine at
  Ileocecal Valve

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SMALL INTESTINE continued

• Wall Modifications
• All Increase Surface Area for Maximum Absorption
• Plicae Circulares Transverse Folds of Mucosa
  Submucosa
• Villi Finger-like Projections of Mucosa,
  contain Capillaries Lacteal
• Microvilli Microscopic Folds of Cell Membrane

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ALIMENTARY CANAL ORGANIZATION continued

• LARGE INTESTINE
• Functions
• Secretes Mucus
• Absorbs Water, Ions, Vitamins (From Bacterial
  Metabolism)
• Forms Compacts Feces (Undigested Food,
  Bacteria, Water)

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LARGE INTESTINE continued

• 3 Divisions
• Cecum
• Blind Pouch
• Appendix Attached
• Colon - Divided into Ascending, Transverse,
  Descending, Sigmoid
• Rectum Anal Canal
• Internal Anal Sphincter (Smooth)
• External Anal Sphincter (Skeletal)

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LARGE INTESTINE continued

• Wall Modifications
• Taenia Coli 3 Bands of Longitudinal Muscle from
  Muscularis of Colon
• Haustra Pouches in Wall of Colon
• No Villi

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ALIMENTARY CANAL MOVEMENTS

• Peristalsis - Wave-like Contraction of Circular
  Longitudinal Smooth Muscle for Propulsion
• Segmentation Mixes Pushes Chyme Against Wall
  of Small Intestine
• Haustral Churning Pouch-to-Pouch Movement in
  Large Intestine
• Reverse Peristalsis

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ACCESSORY ORGANS

• SALIVARY GLANDS
• Exocrine Glands
• Ducts Carry Secretions (Saliva) into Mouth
• Saliva Amylase, Mucous, Water, Antibodies,
  Lysozyme
• 3 Pairs
• Parotid (Most Salivary Amylase)
• Submandibular
• Sublingual

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ACCESSORY ORGANS continued

• LIVER
• Largest Gland in Body (Exocrine)
• Produces Secretes Bile (Fat Emulsifier)
• Nutrient Storage Conversion
• Synthesizes Blood Proteins
• Detoxification

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ACCESSORY ORGANS continued

• GALL BLADDER
• Muscular Sac
• Stores Concentrates Bile
• Receives Bile from Liver via Common Hepatic Duct
  ? Cystic Duct
• Releases into Duodenum via Cystic Duct ? Common
  Bile Duct ? Ampulla of Vater (Sphincter of Oddi)

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ACCESSORY ORGANS continued

• Bile Release
• Chyme Enters Duodenum
• Cholecystokinin (CCK) Secretin Secreted by
  Duodenum, Enters Blood
• Secretin stimulates liver to produce bile
• CCK Stimulates Contractions in Gall Bladder
  Relaxation of Sphincter

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ACCESSORY ORGANS continued

• PANCREAS
• Exocrine ( Endocrine) Gland
• Secretes Pancreatic Juice (Digestive Enzymes
  Buffers)
• Leaves Pancreas Through Pancreatic Duct(s),
  Enters Duodenum Through Ampulla of Vater
• Raises pH of Duodenum (pH 8, Natural Antacid)
  via bicarbonate ions

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