Practical demonstration of gross anatomy & histology of Jejunum,

Ileum,Appendix and Colon

By Dr. Abdul Waheed Ansari

Chairperson &Prof. Anatomy, RAKCOMS. RAKMHSU.

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Learning outcomes of the lab are:-

• 1. Identify the different segments of small intestines-Duodenum, Jejunum and Ileum.

• 2. Identify the gross features of large intestines-appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum and anal canal.

• 3. Histological features of ileum, jejunum, appendix and colon.

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Features of duodenum

• It is the first part of small intestines, 25 cms long.

• It is retroperitoneal except first inch of first part of duodenum.

• It has four parts, C shaped.

• Second part has opening of CBD and pancreatic ducts, major duodenal papilla and minor duodenal papilla.

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The Jejunum is the second portion of small intestines

• It starts from duodenojejunal flexure to ileocaecal junction.

• The proximal 1/3rd are the jejunum loops and distal 2/3rd

are the loops of ileum.• The jejunum loops are more

muscular and more vascular where as ileal loops are thin walled and less vascular, interior shows plicae circularis.

• Internally ileum have Payer’s patches.

• The plicae circularis are few in the ileum.

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The arterial supply of jejunum and ileum

• The superior mesenteric artery is the artery of midgut.

• It gives jejunal branches and ileal branches and terminates as ileocaecal artery.

• The accompanying vein joins the splenic vein to form the portal vein.

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Histology of Jejunum• The mucosa of the small

intestine is lined by simple columnar epithelium which evaginates into villi.

• The epithelium of villi is continuous with that of adjacent crypts.

• Lamina propria of the small intestine forms the core of villi and surrounds the crypts.

• The muscularis mucosa of the small intestine forms a thin layer.

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Ileum • The Peyers patches are found

in the ileum.

• They are found at the antimesentreric border.

• Histology of Ileum is characterized by submucosa having lymphoid tissue-Peyer’s patches

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Appendix • The human's appendix averages

11 cm in length but can range from 2 to 20 cm.

• The diameter of the appendix is usually between 7 and 8 mm

• It has no haustrations, no taenia coli and no plicae circularis and no Peyer’s patches and no appendices epiploicae.

• It has a mesentery of its own, carrying the artery to appendix.

• The tip of the appendix can have a variable position within the abdominal cavity :

• retro-caecal (65-70%)

• pelvic (25-30%)

• pre- or post-ileal (5%)

• Inflammation is called as appendicitis.

• Pain will be felt around umbilicus because of referred pain-T10 segment dermatome.

• The arterial supply- appendicular artery, a branch of the ileocolic artery which is a branch of the superior mesenteric artery.

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Normal appendix ultrasound image longitudinally

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Appendicitis –perforation detected by sonography

Sonography of swollen and inflamed appendix longitudinal section

• Appendicitis shows up as a tubular structure that does not push out of the way or compress, often with changes in the adjacent fat from the inflammation.

• This will often cause the patient to say, “Ouch, that is where it hurts.”

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Histology of appendix

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Colon histology

• The mucosa is having simple columnar epithelium with lots of mucus glands-goblet cells. Simple tubular intestinal glands.

• Submucosa having neurovascular bundles.

• Muscularis external having both circular and longitudinal fibers- taenia coli are longitudinal bundles

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The large intestines

• The caecum, appendix , ascending colon, transverse colon, descending colon, sigmoid colon, rectum and anal canal are parts of large intestines.

• It is supplied by branches from superior and inferior mesenteric arteries.

• At the anal canal there is anastomosis between systemic veins and portal veins, hence one of the sites for anal hemorrhoids formation.

• It shows haustrations, taenia coli, appendices epiploicae, all typical features of large intestines, except appendix rectum and anal canal.

• The anal canal has dual epithelial lining, upper part simple columnar and lower part stratified squamous non keratinized.

• The anal canal has two sphincters, external and internal. External anal sphincter is voluntary where as internal is involuntary.

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Large intestines external features

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The anal canal

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References

• http://www.studyblue.com/notes/note/n/anal-triangle/deck/8502291

• http://ect.downstate.edu/courseware/haonline/labs/L39/130202.htm

• http://histologyatlas.wisc.edu/slides/398

• http://quizlet.com/17115737/27-digestive-system-flash-cards/

• http://www.ultrasoundcases.info/Cases-Home.aspx

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