Histopathology And Cellular Function ✅ Flashcards
Describe the structure of the GI tract, from mouth to anus?
Tubular structure with 4 layers
What are the layers of the GI tract?
- Mucosa
- Submucosa
- Muscularis externa
- Serosa
What is the mucosa of the GI tract made up of?
- Epithelium
- Connective tissue
- Thin smooth muscle
What is the submucosa of the GI tract made up of?
Connective and supportive tissue
What is the muscularis externa of the GI tract made up of?
Two thick layers of smooth muscle
What is the serosa of the GI tract made up of?
Thin outer layer of connective and supportive tissue
What epithelium does the oesophagus have?
Non-keratinised stratified squamous epithelium
What is the function of the muscularis externa in the oesophagus?
Peristaltic contractions of the muscuarlis externa propel the food boluses forward into the stomach
What epithelium is present in the stomach?
Columnar epithelium
What does the columnar epithelium of the stomach contain?
- Mucus-secreting cells
- Many immune cells
What do the mucus secreting cells in the stomach mucosa form?
Gastric pits
How do the mucus secreting cells in the gastric mucosa form gastric pits?
By invaginating down
What happens to the gastric pits from the fundus to the pylorus?
They become deeper
What immune cells are present in the gastric mucosa?
- Plasma cells
- Lymphocytes
What is the inner lining of the small intestine formed of?
- Plicae circularis
- Villi
- Mucosal epithelium
What are plicae cirecularis?
Transverse ridges
What are villi?
Tall finger-like projections of mucosa
What is found between the villi in the small intestine?
Crypts of Lieberkuhn
What kind of epithelium is found in the small intestine?
Columnar
What is the function of microvilli in the small intestine?
They greatly increase the surface area
What is the surface area of the small intestine in adults?
250m2
How can the duodenum be distinguished histologically?
By presence of Brunner’s cells
Where are Brunner’s cells found?
At the hepato-pancreatic sphincter (sphincter of Oddi)
What is the function of Brunner’s cells?
They produce an alkaline substance to aid digestion
Which portion of the small intestine has the tallest villi?
Jejenum
Where do the villi extent from in the jejunum?
The permanent circular fold of the mucosa and submucosa
How is the ileum identified histologically?
Presence of aggregated lymphoid follicles, known as Peyer’s patches, which are found in the submucosa
What is the predominant immune cell found throughout the GI system?
Lymphocytes
Where are lymphocytes found in the GI tract?
In the surface epithelium and in the lymphoid follicles
What do the lymphocytes found in the GI tract collectively make up?
Gut-associated lymphoid tissue (GALT)
What other immune-mediating cells are found in the small intestine?
Paneth cells
Where are Paneth cells located?
In the crypts
What do Paneth cells contain?
Granular material important in lysis of microorganisms
What is present in the colon when viewed microscopically?
A number of microscopic crypts that extend down to the muscularis mucosa
What is found within the crypts of the colon?
Goblet cells
What is the function of the goblet cells of the colon?
Production of mucus
What GI abnormalities can be diagnosed with histopathology?
- Coeliac disease
- Inflammatory bowel disease
- Eosinophilic diseases
- Oesophagitis, gastritis, and gastro-oesophageal reflux
What is coeliac disease?
A multi-system disease, including a small intestinal enteropathy secondary to exposure to gluten
What are the classic histological findings of coeliac disease?
- Flattened duodenal mucosa with loss of crypt architecture
- Intraepithelial lymphocytosis
- Glandular hyperplasia
Are the histological findings in coeliac disease reversible?
Yes
How can the histological findings in coeliac disease be reversed?
Gluten exclusion diet
Where can changes be demonstrated histologically in Crohn’s disease?
Anywhere from mouth to anus
What is found histologically in Crohn’s disease?
- Areas of chronic inflammation, comprising increased lamina propria plasma cells and lymphocytes
- Skip lesions including patchy erosions or ulcers, vertical fissures, and fistulas
- Transmural inflammation with multiple lymphoid aggregates and granulomas
Where does UC affect?
Only the large bowel
What is found histologically in UC?
- Alteration of crypt architecture, including cryptitis and crypt abscesses
- Increased chronic inflammatory cells in the lamina propria, including lymphocytes and plasma cells
Are eosinophils normally found in the GI tract?
Yes
What happens in eosinophilic disease of the GI tract?
There is a markedly increased eosinophilic infiltrate in the mucosa
What do the symptoms of eosinophilic diseases of the GI tract depend on?
The site of the disease
How does eosinophilic oesophagitis present?
- Dysphagia
- Retrosternal chest pain
- Bolus dysphagia (food bolus lodged in oesophagus)
How does eosinophilic intestinal disease present?
- Recurrent abdominal (often epigastric) pain
- Vomiting
- Dysphagia
- Diarrhoea
When can inflammation of the oesophagus and stomach occur?
When there is excess secretion of gastric acid, and if the contents of the stomach reflux back into the oesophagus
Who is gastro-oesophageal reflux common in?
Infants
Why is gastro-oesophageal reflux common in infants?
Due to the immaturity of the lower oesophageal sphincter
How does gastro-oesophageal reflux differ in infants compared to adults?
In infants, it is rarely associated with the formation of dysplastic cells, such as those seen in Barrett’s oesophagus in adults
What are the other causes of oesophageal and gastric inflammation?
- Ingestion of caustic material
- Presence of H. Pylori
- General severe systemic illness such as sepsis
