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					Digestion C

 Chapter 22
       Accessory Structures
• Last week we talked about
  – Teeth
  – Tongue
  – Salivary glands
• Today we will cover
  – Pancreas
  – Gall bladder
  – Liver
                         Pancreas
• Assists in chemical digestion
    – Enzyme secretion
•   Assists in neutralizing acid chyme
•   ~15 cm long
•   Secretes into duodenum
•   Exocrine (99%) & Endocrine gland (1%)
•   Structure
    – Head
       • Broad portion residing w/in loop of duodenum
    – Body
       • Elongated portion inferior to stomach
    – Tail
       • Blunt end adjacent to spleen
Pancreas
Pancreas
         Pancreas Function
• Produce pancreatic juice
• Sodium bicarbonate
  – Neutralizes acid chyme
• Enzymes
  – Pancreatic Amylase- Carbohydrates
  – Pancreatic lipases- lipids
  – Trypsin & chymotrypsin- proteins
  Pancreatic Secretory Structures
• Secretion enter duodenum via ducts
• 2 ducts
  – Pancreatic duct
    • Main delivery duct
    • Joins common bile duct from liver
    • Duodenal (aka Hepatopancreatic) ampulla
  – Accessory duct
    • Smaller, superior duct
Pancreatic & Accessory Duct
Hepatopancreatic ampulla
             Pancreas Histology
• Lobulated gland
• Glandular epithelial cells
• 99% exocrine
   – Acinar cells- secrete digestive enzymes
• 1% endocrine- hormones
   –   Islets of Langerhans
   –   Beta cells (60%)- Insulin
   –   Alpha Cells (25%)- Glucagon
   –   Delta Cells (15%)- Somatostatin
Lobulate
Acinar Cells
Endocrine
                    Liver
•   Hepat= liver
•   Largest abdominal organ (~3 lbs)
•   Aids in digestive function
•   Lobed structure
•   Highly vascularized
Liver
     Liver Digestive Function
• Metabolic regulation
• Hematological Function
• Bile synthesis & secretion
        Metabolic Regulation
• Regulates carbohydrate, lipid, & protein
• All blood leaving digestive tract travels
  directly to liver
  – Hepatic portal vein
  – Hepatocytes- liver cells
     • Monitor & adjust blood nutrients
     • Remove & store excess nutrients
     • Detoxify blood
      Hematological Function
• Regulates blood composition
  – Kupffer cells- phagocytic cells
     • Remove old or damaged blood cells, cellular
       debris & pathogens
     • Heavy metals
• Produce blood proteins
    Bile synthesis & secretion
• Breakdown product of hemoglobin
  pigment (RBC)
• Functions
  – Neutralize acid chyme
  – Emulsify lipids
     • Breaks lipids into smaller lipid units
• Products stored in Gall Bladder
           Liver Anatomy
• 4 Lobes
• Large right & left lobes
• Small caudate & quadrate lobes
Right & Left Lobes
Right & Left Lobes
Caudate & Quadrate lobes
Caudate & Quadrate lobes
                  Blood Supply
•   High rate of profusion
•   25% of total cardiac output
•   2 blood sources
•   Hepatic artery
    – Blood supply from heart to liver
    – Oxygen rich
• Hepatic portal vein
    – Blood from the intestines to liver
    – Nutrient rich, oxygen poor
    – Liver processes incoming blood from GI tract
            Liver Histology
• Hepatocytes- liver cells
• Arranged into columns around large
  central vein
• Hexagonal shaped cell grouping
  – “spokes on a wheel”
• Lobule
  – Functional unit of liver
  – Hexagonal arrangement
  – 100,000 lobules/ liver
Central Vein
Hepatocyte functional unit
              Sinusoids
• Extensions of blood vessels between
  columns of hepatocytes
• Carries blood to be processed past
  hepatocytes
• Site of Kupffers cells
• Extend between the cells inside the
  lobules
         Liver Fluid Movement
• Blood enters via
   – Hepatic portal vein (GI tract)
   – Hepatic artery (heart)
• Both vessels branch into smaller vessels to
  supply each liver lobule
   – Blood enters lobules at periphery
   – Travels down sinusoids passing hepatocytes
• Processed blood drains into central vein
• All central veins unite to form hepatic vein
   – Delivers processed blood to the heart
            Bile Canaliculi
• Narrow intercellular channels draining Bile
  produced by hepatocytes
• Bile flows away from central vein toward
  lobule perifery
• Collected by bile duct
              Hepatic Triad
• “portal triad”
• Arrangement of vessels at lobule
  periphery
• Branch of
  – Hepatic portal vein
  – Hepatic artery
  – Bile duct
              Hepatic Triad
• Hepatic Artery
• Bile Duct
Gall Bladder
                     Bile Drainage
• Right hepatic ducts
   – Collects bile from ducts on right side of liver
• Left hepatic ducts
   – Collects bile from bile ducts on left side of liver
• Common hepatic duct
   – Union of rt & lt hepatic ducts
• Cystic duct
   – Duct from gall bladder
• Common bile duct
   – Union of cystic duct & common hepatic duct
   – Drains into duodenum
   – Hepatopancreatic ampullae
Bile Drainage
                   Gallstones
• Bile contains water, cholesterol, fats, bile salts,
  proteins, bilirubin (waste)
• Bile with high concentrations of cholesterol, bile
  salts, or bilirubin can harden into gallstones
   – Cholesterol stones- yellow green (80%)
   – Pigment stones- bilirubin
Gallstones
         Clinical Application
• Liver Cirrhosis
• Scarring of liver
• Formation of fibrous scar tissue
  associated with destruction of normal liver
  architecture
• Only 30% of patients survive 5+ yrs past
  diagnosis
• Most common reason for liver transplants
           Leading Causes
• 2001 7th leading cause of death
• Alcoholism
  – ~50% of all Cirrhosis
• Hepatitis C
  – 1/70 persons
  – 30% will develop cirrhosis
Liver Cirrhosis

				
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