large intestine / histology / discussion / viva / oral / questions

1. What are the four main layers of large intestine?
• 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 large intestine?
• Simple columnar epithelium and numerous goblet cells
4. What is the function of large intestine?
• Water and electrolyte reabsorption
5. Why the goblet cells are more in large intestine?
• The digested food becomes harder and harder as it moves towards large intestine since due to reabsorption of water and electrolytes. Mucus helps the hard substance to move easily further towards anus without damage to the wall.
6. What are the components of lamina propria?
• Loose connective tissue
• Blood vessels
• Lymphatics
• 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. Name the different types of cells in large intestine.
• Columnar absorptive cells
• Goblet cells
• Enteroendocrine / APUD cells
• Mucous cells
• Undifferentiated cell
• Paneth cells
• Lymphocytes
• M cells
9. What is muscularis mucosae?
• Muscularis mucosae is thin layer of smooth muscle arranged as inner circular and outer longitudinal layers around the lamina propria. 
10. What are the components of submucosa?
• Dense connective tissue
• Larger blood vessels
• Submucosal (Meissner's) plexus of autonomic nerves
11. What are the components of muscularis externa? Or what is the arrangement of muscle fibers in muscularis externa?
• Inner circular smooth muscle layer
• Outer longitudinal smooth muscle layer. The muscle fibers are thickened in three places to form bands called taenia coli
• Between two layers is thin connective tissue layer with blood vessels, lymph vessels, myenteric (Auerbach's) plexus of autonomic nerves
12. What are taenia coli?
• Taenia coli are thickenings of outer longitudinal layer of muscularis externa. There are 3 taenia coli which can be traced to root of appendix. 
13. What is serosa?
• Serosa- thin layer of loose connective tissue with numerous blood vessels, lymphatics, adipose tissue lined by mesothelium (simple squamous epithelium)
14. What is mesothelium?
• It is a simple squamous epithelium covering a thin layer of loose connective tissue in the abdomen surrounding the viscera
15. 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
16. What is the function of Myenteric plexus?
• Myenteric plexus supplies the GIT and controls the gastric motility
17. List the characteristic features seen only in large intestine?
• Plicae circularis, Villi are absent
• Numerous Goblet cells
• Crypts of Leiberkuhn are more numerous, connective tissue very less
18. 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

18. 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 of Leiberkuhn 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	Dense irregular connective tissue with large blood vessels, lymphatic vessels, Meissner’s plexus, glands and lymphatic tissue in some parts.	Dense 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.