Digestive Tract

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Digestive Tract

• Associated Organs

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Pancreas

• Pancreas thin capsule (thin DICT) forms septa
  covered with visceral peritoneum.
• Exocrine Pancreas - majority of the organ acini
  of 8-15 cuboidal cells in delicate reticular CT
  no myoepithelium.
• Acini are irregular arranged and separated by
  vessels, nerves, and ducts.

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Pancreas

• Duct System
• a) centroacinar - simple squamous
  epithelium that extends up into the acinus.
• b) intercalated - simple cuboidal epithelium
• c) intralobular - simple cuboidal to simple
  columnar epithelium
• d) interlobular - simple columnar epithelium,
• in septa.

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C condensing vacuole S secretory (zymogen)
granule
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Endocrine Pancreas

• Islets of Langerhans
• Islets separated from exocrine parenchyma by
  thin reticular CT.
• Cuboidal cells in cords with blood capillaries
  between.
• Cell Types
• a) A or alpha - glucagon, increases blood
  sugar level.
• b) B or Beta - most numerous cell insulin,
  decreases blood sugar.
• c) D or delta - somatostatin, inhibits A's and
  B's.

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Liver

• Liver largest gland in the body (1 to 1.5 Kg)
• a) maintains blood glucose
• b) converts fats into lipoprotein
• c) stores vitamins A, D, E, K, and heparin
• d) secretes bile salts, fibrinogen, and plasma
  albumins.
• e) synthesizes cholesterol
• f) excretes bile pigments
• g) produces urea in N metabolism
• h) detoxifies blood toxins
• I) phagocytizes particulate material in blood
  Kupffer's cells.
• j) hematopoiesis in fetus and newborn.

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Liver

• Liver has a DICT capsule Glisson's Capsule.
• Vessels enter and leave organ only on ventral
  surface Porta Hepatis.
• The major part of the liver is covered with
  visceral peritoneum.
• The basic functional unit of the liver is the
  Liver Lobule.
• Each lobule is usually 6-sided a central venule
  drains blood from the center of the lobule.

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Liver

• Vessels enter and leave the lobule via Portal
  Spaces (triads) at three corners.
• Portal Spaces contain
• a) hepatic arteriole
• b) hepatic portal venule
• c) lymph vessel
• d) bile ductule (Canal of Hering)
• e) nerves

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Liver

• Hepatic parenchyma is of vertical plates of
  simple cuboidal epithelium radiating from the
  periphery toward the central venule.
• Parenchymal plates have 2 free surfaces internal
  cell membranes form tubular canals Bile
  Canaliculi (capillary).
• Each free surface has prominent microvilli that
  project into the Perisinusoidal Space (Space of
  Disse).

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Liver

• Afferent Vessels feed hepatocytes a) hepatic
  artery (25) -gt capillary sinus -gt central
  venule.
• b) hepatic portal vein (75) -gt capillary sinus
  -gt central venule.
• Efferent Vessels- Ducts
• a) lymph vessels not present in lobule lymph
  collects at periphery in Spaces of Mall next to
  portal space (triad).
• b) bile canaliculus (center of hepatocyte plate)
  -gt bile ductule -gt bile duct -gt right/left
  hepatic duct -gt common hepatic duct -gt cystic
  duct -gt gall bladder.

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Liver

• Hepatocytes are commonly bi-nucleate have
  prominent microvilli are of variable shapes and
  sizes cells at periphery are larger.
• Central Venule feeds sublobular veins -gt
  collecting veins -gt hepatic veins (no valves).
• Hepatic portal veins carry all absorbed nutrients
  except fats to liver.

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Hepatocyte
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Gall Bladder

• Gall bladder - three layers, no submucosa.
• Mucosa - simple columnar epithelium simple
  glands present.
• - lamina propria of delicate reticular and
  areolar CT forms prominent finger-like
  extensions.
• - no muscularis mucosa.
• Muscularis Externa - 2 mixed layers.
• Serosa and Adventitia -

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Gall Bladder

• Stores bile and absorbs liquid thus concentrating
  the bile
• Muscularis Externa and Mucosa forms the Spiral
  Valve of Heister.
• Gallbladder is emptied by the Cystic Duct into
  the Common Bile Duct to the Ampulla of Vater.
• The bile duct is controlled by the lower
  Sphincter of Boyden.

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