Duodenum, histology, discussion, viva, oral, questions

1. What are the four main layers of duodenum?
• From within (lumen) outwards
• Mucosa (mucous membrane)
• Submucosa
• Muscularis externa
• Serosa or adventitia
2. What are the layers of mucosa?
• From lumen outwards
• Epithelial lining
• Lamina propria
• Muscularis mucosae
3. What is the epithelial lining in duodenum?
• Simple columnar epithelium with striated border and few goblet cells
4. What are the modifications of mucosa?
• Plicae circularis, villi, microvilli       
5. What are the functions of modifications of mucosa?
• Modifications of mucosa increases the surface area of absorption      
6. What are the components of lamina propria?
• Loose connective tissue
• Blood vessels
• Lymphatics
• Lymphocytes
• Nerves
• Crypts of Leiberkuhn or intestinal glands
7. What are crypts of Lieberkuhn?
• Intestinal glands or crypts of Lieberkuhn are the invaginations of surface epithelium (simple columnar epithelium) into lamina propria
8. What are lacteals?
• Lacteals are dilated blind ending lymphatic capillary present in the core of lamina propria of the villus
9. What are the plicae circularis, villi, microvilli?
• Plicae circularis is the permanent fold of 3 layers of mucosa with core of submucosa
• Villi are the surface projections of epithelial layer with core of lamina propria
• Microvilli are the projections of cell membrane with core of cytoplasm
10. Name the different types of cells in intestinal glands.
• Columnar absorptive cells
• Goblet cells
• Enteroendocrine / APUD cells
• Mucous cells
• Undifferentiated cell
• Paneth cells
• Lymphocytes
• M cells
11. What is muscularis mucosae?
• Muscularis mucosae is a thin layer of smooth muscle arranged as inner circular and outer longitudinal layers around the lamina propria
12. What are the components of submucosa?
• Dense connective tissue
• Larger blood vessels
• Submucosal (Meissner's) plexus of autonomic nerves
• Duodenal or submucosal glands
13. What are duodenal glands?
•  Duodenal glands also called as submucosal  glands present in the submucosa are mucus secreting cells  lining the branched tubuloacinar glands
14. What are the components of muscularis externa?
• Inner circular smooth muscle layer
• Outer longitudinal smooth muscle layer
• Between outer two layers is thin connective tissue layer with blood vessels, lymph vessels, myenteric (Auerbach's) plexus of autonomic nerves
15. What is serosa?
• Serosa- thin layer of loose connective tissue with numerous blood vessels, lymphatics, adipose tissue covered by simple squamous epithelium (mesothelium)
16. Difference between serosa and adventitia

Serosa	Adventitia
Thin layer of loose connective tissue with numerous blood vessels, lymphatics, adipose tissue covered by mesothelium (simple squamous epithelium)	Loose connective tissue with numerous blood vessels, lymphatics, adipose tissue which merges with surrounding tissues. Mesothelium is absent

17. What is mesothelium?

• It is a simple squamous epithelium covering a thin layer of loose connective tissue in the abdomen surrounding the viscera

18. What is the function of Meissner's plexus?

• Meissner’s plexus regulates the configuration of the luminal surface, controls glandular secretions, alters electrolyte and water transport and regulates local blood flow

19. What is the function of Myenteric plexus?

• Myenteric plexus supplies the GIT and controls the gastric motility

20. List the characteristic features seen only in duodenum?

• Goblet cells are few
• Villi are tall, broad and numerous
• Duodenal glands in submucosa

21. Name the differences between the duodenum, jejunum and ileum?

	Duodenum	Jejunum	Ileum
Mucosa Epithelium	Striated columnar with few goblets cells.	Striated columnar with more goblet cells.	Striated columnar  with a high number of goblet cells.
Villi	Leaf shaped.	Tall, tongue shaped.	Short, finger shaped.
Lamina propria	Crypts with argentaffin cells. Loose lymphatic tissue.	Crypts with less argentaffin cells. Diffuse lymphatic nodules.	Crypts with less argentaffin cells. Lymphatic nodules aggregated to form Peyer’s patches.
Muscularis mucosa	Continuous.	Interrupted.	Interrupted.
Submucosa	Presence of Brunner’s glands. Connective tissue with blood vessels and nerves.	Connective tissue with blood vessels and nerves.	Presence of Peyer’s patches. Connective tissue with blood vessels and nerves.
Muscularis externa	Inner circular and outer longitudinal smooth muscle   layers with myenteric (Auerbach’s) nerve plexus, blood and lymph vessels.	Inner circular and outer longitudinal smooth muscle   layers with myenteric (Auerbach’s) nerve plexus, blood and lymph vessels.	Inner circular and outer longitudinal smooth muscle   layers with myenteric (Auerbach’s) nerve plexus, blood and lymph vessels.
Serosa	Loose connective tissue with blood and lymph vessels covered by mesothelium.	Loose connective tissue with blood and lymph vessels covered by mesothelium.	Loose connective tissue with blood and lymph vessels covered by mesothelium.

22. Name the differences between the small intestine and large intestine.

	Small Intestine	Large Intestine
Mucosa	Plicae circularis and villi present.	Absent.
Epithelium	Goblet cells less in number and columnar cells more in number.	Goblet cells more in number and few columnar cells.
Lamina Propria	Crypts of Leiberkuhn are few and consist of columnar cells, goblet cells, more number of Paneth and argentaffin cells.	Crypts are more numerous, deeper and consists of less number of columnar cells, numerous goblet cells, very rarely Paneth and argentaffin cells.
Muscularis mucosa	Smooth muscle: inner circular and outer longitudinal layers. Interrupted in some regions.	Smooth muscle: inner circular and outer longitudinal layers.
Submucosa	Irregular connective tissue with large blood vessels, lymphatic vessels, Meissner’s plexus, glands and lymphatic tissue in some parts.	Irregular connective tissue with large blood vessels, lymphatic vessels, Meissner’s plexus, lymphatic tissue.
Muscularis externa	Inner circular and outer longitudinal smooth muscle   layers with myenteric (Auerbach’s) nerve plexus, blood and lymph vessels. Longitudinal coat uniformly thick.	Inner circular and outer longitudinal smooth muscle   layers with myenteric (Auerbach’s) nerve plexus, blood and lymph vessels. Longitudinal coat, thickened to form three bands, the taenia coli.
Serosa	Loose connective tissue covered by mesothelium, has blood and lymph vessels.	In some parts absent, which are covered by adventitia.