Histology of the Small and Large Intestine Flashcards
How do nerves, blood vessels and lymphatic vessels reach the alimentary canal?
- Mesenteries
- Adjacent connective tissue (tunica adventitia in retroperitoneal organs)
Where are mucosal glands found in the alimentary canal?
- Throughout length
- Sparingly in oral cavity + oesophagus
Where are submucosal glands found in the alimentary canal?
- Oesophagus
- Duodenum
Where are villi found in the alimentary canal?
Small intestine
Where are lymphoid tissue/nodules found in the alimentary canal?
Lamina propria of entire length
General tissue layers of alimentary canal
- Epithelium
- Lamina propria
- Muscularis mucosa
- Submucosa
- Inner circular muscular layer
- Outer longitudinal muscular layer
- Serosa
Distinct features of the duodenum
- Brunner’s glands (submucosa)
- Broad, leaf-like villi
- Plicae circulares not obvious
- Paneth cells not readily observed
- Low number of goblet cells
- Lymphoid tissue fairly inconspicuous
Distinct features of the jejunum
- Submucosal glands absent
- Long, finger-like villi
- Plicae circulares begin to appear
- Paneth cells found at base of glands of Lieberkühn
- Moderate number of goblet cells
- Moderate amount of lymphoid tissue
Distinct features of the ileum
- Submucosal glands absent
- Short, finger-like villi
- Prominent plicae circulares
- Paneth cells found at base of glands of Lieberkühn
- Goblet cell numbers highest
- Prominent lymphoid tissue seen in Peyer’s patches
What type of epithelium lines the mucosa of the small intestine?
Simple columnar epithelium
Major cell types contained in the epithelium of the small intestine
- Enterocytes
- Goblet cells
- Enteroendocrine cells
- Paneth cells
- Tuft cells
- Intestinal stem cells
Features/functions of enterocytes
- Absorptive
- Columnar with apical microvilli
- Glycocalyx coats microvilli (glycoproteins involved in digestive process)
Features/functions of enteroendocrine cells
Produce gastrin, secretin + cholecystokinin
Features/functions of Paneth cells
Produce several antimicrobial proteins (AMPs)
Features/functions of tuft cells
Increase in number in response to intestinal parasite infection
What are intestinal villi surrounded by?
At least 6 crypts of Lieberkühn
What do crypts of Lieberkühn contain and for what purpose?
- Intestinal stem cells (ISCs)
- Maintain epithelial lining of villus + crypt
What do Brunner’s glands secrete and into where?
- Mucous
- Crypts of Lieberkühn via excretory ducts
Degrees of folding in the small intestine
- 1st = plicae circulares
- 2nd = villi
- 3rd = crypts of Lieberkühn
- 4th = microvilli
What does the mucosa of the large intestine contain?
Crypts of Lieberkühn
Cells present in the mucosa of the large intestine
- Simple columnar absorptive enterocytes with apical microvilli
- Predominantly goblet cells
- Enteroendocrine cells
What does the outer longitudinal muscular layer of the large intestine form and what for?
- 3 band of smooth muscle called taeniae coli
- Aid in peristaltic movement of faeces
Epithelial change from rectum to anus
Simple columnar –> stratified squamous
Where does the longitudinal muscle layer of the alimentary canal stop, and what is it replaced by?
- At pelvic diaphragm
- Replaced by external anal sphincter
