histology of Digestive system 3

1. Digestive System-3
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2. Large Intestine
• Comprises of
– Caecum
– Colon
– Rectum
• Common Characteristics
– no plicae circulares
– Absence of Villi
– Longer less coiled, simple tubular glands with
many goblet cells.

3. Large Intestine (Colon)
• Mucosa:
– Epithelium: Simple columnar Epithelium with goblet cells,
– Lamina Propria with Intestinal Glands
– Muscularis mucosae
• Sub-Mucosa:
– Connective tissue, cells and fibers with blood vessels and nerves.
• Muscularis Externa
– Inner circular layer of smooth muscles
– Outer Longitudinal muscles, condensed to from three longitudinal
bands (Taeniae coli).
• Serosa

7. Rectum
• Same as of colon except that muscularis
externa doesn't have taenie coli bands.
Muscularis externa inner circular layer and
outer longitudinal muscles.

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10. Accessory organs of the digestive
system
• Located outside of the digestive tube.
• deliver their secretory products to the oral
cavity or small intestine by excretory ducts.
– Salivary glands (Covered)
– liver,
– gallbladder,
– Pancreas.

11. Liver
• The liver is covered by a thin connective tissue
capsule (Glisson's capsule) that becomes thicker at
the hilum.
• The Liver Lobule
– Sheets of connective tissue divide the liver into thousands
of small units called lobules. A lobule is roughly hexagonal
in shape, with portal triads at the vertices and a central
vein in the middle.
– from Central vein radiate plates of liver cells, called
hepatocytes, and sinusoids having Kupffer cells(capillaries)
toward the periphery.
– Connective tissue make the boundary of each lobule
(extensions of capsules inside liver).
– In connective tissue forms portal areas, where branches of
the hepatic artery, hepatic portal vein and bile duct.

12. Liver

16. Gallbladder
• A muscular sac, its wall composed of three tunics.
• Mucosa
– Epithelium: Simple columnar Epithelium
– Lamina propria
• Muscularis Externa
– muscularis externa (muscle layer) contains bundles of
smooth muscle cells, collagen and elastic fibres.
• Adventitia/ Serosa

19. Pancreas
• The pancreas is the main enzyme producing accessory
gland of the digestive system. It has both exocrine and
endocrine functions.
• Exocrine Pancreas
– Its forms majority of pancreas, consist of serous acini having
zymogen cells.
– Acini opens into intercalated ducts (ducts lined by simple
Cuboidal epithelium).
– Intercalated ducts opens into interlobular duct (located in
inter lobular connective tissue).
• Endocrine Pancreas
– Between serous acini are located small lightly stained Islets
(Islets of Langerhans), the endocrine part of Pancreas.
– Islets composed of Alpha, Beta and Delta cells).