L6 - Histology of the Gut Tube Flashcards
Describe the common structure of endodermal tube (the layers).
- Lumen
- Mucosa (epithelium, lamina propria)
- Submucosa (nerves and blood vessels)
- Muscularis externa
- Adventitia (anchor) / Serosa (serous membrane)
Describe the histology and related functions of the oesophagus.
Oesophagus layered in stratified squamous epithelium - protection from dry, rough food.
Also has mucous glands in mucosa/submucosa to lubricate passage.
To help food passage, it has skeletal muscle in the upper oesophagus (rapid movement of food past the airway - swallowing) and smooth muscle in the distal end (peristalsis)
What are the 4 regions of the stomach?
Fundus, body, pyloric antrum and pyloric canal.
What is the role of the two sphincters in the stomach?
Cardiac sphincter - Structural - Prevents reflux with help from diaphragm.
Pyloric sphincter - Physiological - Releases chyme into duodenum when appropriate.
Describe the two types of digestion that occurs in the stomach.
Mechanical - oblique muscle layer for ‘churning’
Chemical - Enzymes and acid from gastric glands.
What layer are stomach glands found?
Lamina propria
What are the three sections of the small intestine?
Duodenum, jejunum and ileum.
What are the mucosal/submucosal specialisations of the small intestine that allow for greatest absorption?
- Plicae circulares - submucosal/mucosal folds
- Vili - mucosal folds
- Microvilli - microfolds in cell membrane
Describe the histology of the duodenum
Simple columnar with microvilli.
Has large villi with crypts.
Plicae circularis increase in number towards the jejunum.
BIliary secretions via duodenal papillae. Submucosal glands secrete alkaline mucous
Differentiate between jejunum and ileum.
Jejunum = many plicae circularis, large villi, short crypts.
Ileum = few PC, small villi, deeper crypts
Jejunum is more focused on absorption.
What are lacteals?
Lymphatic vessels that absorb and transport fats in the jejunum.
What do myenteric nerve plexes do ?
Control peristalsis of muscularis externa in the small intestine.
What protection against pathogens exists in the ileum?
Peyer’s patches in the ileum (distinguishes from jejunum) - Lymph nodules of MALT.
Paneth cells in crypts - secrete lysozyme
Name the parts of the large intestine
Caecum → Asc. colon → Transverse colon → Desc. colon → Sigmoid colon → Rectum
Histological features of large intestine
Many goblet cells, no villi, only crypts
Flat luminal surface - no/little absorption, mostly for lubrication for faecal matter.
