Duodenum
•It has four layers-mucosa, submucosa, muscularis externa, adventitia/serosa.
•1. Mucosa-lined by simple columnar cells with microvilli and goblet cells.
-Mucosa thrown into folds called villi for increasing the surface area-broad tongue shaped.
-Each villus has a core of lamina propria with a central lacteal and blood vessels.
-Lamina propria filled with intestinal glands-crypts of Leberkühn.
-Cells present are columnar cells for absorption-enterocytes.
-Mucus secreting goblet cells, paneth cells which secrete lysozymes, undifferentiated cells and neuroendocrine cells.
-Muscularis mucosae made of inner circular and outer longitudinal smooth muscle layers.
•2. Submucosa-loose connective tissue with numerous blood vessels, lymphatics and nerve fibers.
Also contains tubuloalveolar mucus glands called as Brunner's
glands. The secretions from the glands help in neutralizing the acidic contents from the stomach.
•3. Muscularis externa - inner circular, outer longitudinal smooth muscle
Jejunum
•It has four layers-mucosa, submucosa, muscularis externa, serosa.
•1. Mucosa-lined by simple columnar cells with microvilli and goblet cells.
-Mucosa thrown into folds called villi for increasing the surface area--tall leaf shaped.
-Each villus has a core of lamina propria with a central lacteal and blood vessels.
-Lamina propria filled with intestinal glands--crypts of Lieberkühn.
-Cells present are columnar cells for absorption-enterocytes.
-Mucus secreting goblet cells, paneth cells which secrete lysozymes, undifferentiated cells and neuroendocrine cells.
– Muscularis mucosae made of inner circular and outer longitudinal layers of smooth muscles.
•2. Submucosa-loose connective tissue with numerous blood vessels, lymphatics and nerve fibers.
•3. Muscularis externa-inner circular, outer longitudinal smooth muscle.
•4. Serosa--peritoneal covering made of flat squamous cells.
Ileum
•It has four layers--mucosa, submucosa, muscularis externa, serosa.
•1. Mucosa-lined by simple columnar cells with microvilli and goblet cells.
-Mucosa thrown into folds called villi for increasing the surface area-small finger like.
-Each villus has a core of lamina propria with a central lacteal and blood vessels
-Lamina propria filled with intestinal glands-crypts of Lieberkühn.
-Cells present are columnar cells for absorption-enterocytes.
-Mucus secreting goblet cells, paneth cells which secrete lysozymes, undifferentiated cells and neuroendocrine cells.
-Lamina propria shows aggregations of lymphoid follicles called Peyer's patches each containing 10-200 follicles
- Muscularis mucosae made of inner circular and outer longitudinal layers of smooth muscles.
•2. Submucosa-loose connective tissue with numerous blood vessels, lymphatics and nerve fibers,
•3. Muscularis externa-inner circular, outer longitudinal smooth muscle.
•4. Serosa-peritoneal covering made of flat squamous epithelium.
Large Intestine
•It has four layers-mucosa, submucosa, muscularis externa, adventitia/serosa
•1. Mucosa-lined by simple columnar cells with microvilli Goblet cells are numerous.
-No villi are seen
-Lamina propria filled with intestinal glands-crypts of Lieberkühn.
-Cells present are columnar cells for absorption, mucus secreting goblet cells, undifferentiated cells and neuroendocrine cells. No paneth cells.
-Solitary lymphoid follicles are seen.
-Muscularis mucosae made of inner circular and outer longitudinal layers of smooth muscles.
•2. Submucosa-loose connective tissue with numerous blood vessels, lymphatics and nerve fibers,
•3. Muscularis externa-inner circular, outer longitudinal smooth muscle.
Outer longitudinal layer is thickened at three areas forming taenia coli.
•4. Serosa–peritoneal covering made of flat squamous cells. Adventitia-connective tissue in areas not covered by peritoneum.
Appendix
•It has four layers-mucosa, submucosa, muscularis externa, serosa.
•1. Mucosa-lined by simple columnar cells with microvilli. Goblet cells are numerous.
- Lamina propria contains few intestinal glands-crypts of Lieberkühn.
- It also contains numerous lymphoid follicles which extend into submucosa and bulge into the lumen making it irregularly narrow,
- Muscularis mucosa is discontinuous
•2. Submucosa-loose connective tissue with numerous blood vessels, lymphatics and nerve fibers. Also contains lymphoid aggregates which has extended from mucosa.
•3. Muscularis externa-inner circular, outer longitudinal smooth muscle.
•4. Serosa--peritoneal covering made of flat
squamous cells.