Case 1 Histology Flashcards
what are the 4 layers of the wall of the GI tract? what is in each?
• Mucosa = innermost layer which consists of an epithelium, an underlying lamina propria and a layer of smooth muscle (muscularis mucosa)
- epithelium (protective, secretive and/or absorptive)
- lamina propria = connective tissue containing vessels, glands & lymphoid tissue
- muscularis mucosa smooth muscle (inner circular, outer longitudinal), moves the mucosa – this muscular layer is only for local movements
• Submucosa = a (dense irregular) connective tissue layer that contains blood vessels, lymphatics and Meissner’s plexus (submucosal plexus)
- supports mucosa
- glands in some regions
• Muscularis externa = a smooth muscle layer, whose inner fibres (squeezes gut) are arranged circularly and outer ones longitudinally (shortens gut) – contains the myenteric plexus
- responsible for GI movements (peristalsis, segmentation)
• Adventitia = outer, connective tissue layer which contains blood vessels and lymphatics – it’s referred to as a serosa if it is covered by a mesothelial layer
- Serosa is a serous membrane that covers those structures within the peritoneal cavity (if it is intraperitoneal, it is classed as serosal as the serous membrane is visceral peritoneum)
- Extraperitoneal structures are attached to surrounding structures by connective tissue fibres that form the adventitia (if it is extraperitoneal, then it has an adventitia and the extraperitoneal structures are attached to surrounding structures by connective tissue fibres that form the adventitia)
what is the epithelium stained like?
stained dark purple due to the high proportion cellular material
what is the epithelium of the oesophagus?
non-keratinised stratified squamous
what does the submucosa of the oesophagus contain? what staining like? what is muscularis externa layer like? what about outer layer?
- many elastic fibres which allows the oesophagus to distend during swallowing
- seromucous glands whose secretions aid lubrication
- they are particularly numerous at the distal end of the oesophagus as the mucous that they secrete protects the oesophageal mucosa from gastric acid reflux
- blood vessels, lymphatics, nerves
- pale staining
- muscularis externa - layer in the top third of the oesophagus contains skeletal muscle, in the middle, it is a mixture of smooth and skeletal muscle and in the bottom third it is entirely smooth
- adventitia but the last part is serosa
what is the mucosa of the stomach packed with?
branched tubular glands which penetrate through the lamina propria
what extends form the luminal surface to the gastric glands? what is at the base of the gastric glands? what type of epithelium present? what cells are present in the gastric gland?
- gastric pits
- thin muscularis mucosa
- (mucous columnar cells), simple columnar epithelium
Cells present:
- Surface lining
- Mucous neck
- Parietal
- Chief
- Neuroendocrine
what’s in the submucosa of the stomach?
loose connective tissue and contains numerous blood vessels
what is the arrangement of the fibres of the muscularis mucosa in the stomach?
arranged in three layers; inner oblique, middle circular and outer longitudinal = more muscle for churning
what can be seen between the muscle layers in the stomach?
blood vessels and nerves (myenteric plexus)
what forms the outer layer of the stomach wall?
thin serosa
how can the pyloric end of the stomach be distinguished?
presence of the gastric glands and the thick muscle of the pyloric sphincter
describe the mucosa of the duodenum
- the villi projection into the lumen are covered with simple columnar epithelium
- with goblet cells
- crypts of Lieberkhuhn are short tubular gland that are continuous with the base of the villi
when the crypts of Lieberkhuhn are cut in cross section, what do they look like?
circular spaces that are surrounded by tall columnar epithelial cells
what separates the mucosa from the submucosa?
muscularis mucosa
what’s in the submuscosa of the duodenum?
- in the area close to the gastric junction, numerous Brunner’s glands are present
- these glands project into the mucosa
- they secrete mucous and HCO3- for protection against acid and to increase pH
- they are only found in duodenum
- (they secrete an alkaline fluid composed of mucin, which exerts a physiologic anti-acid function by coating the duodenum epithelium, therefore protecting it from the acid chyme of the stomach)