Digestive Tract Histology Flashcards
What is the epithelium covering the oral cavity, oropharynx and laryngopharynx?
Non-karatinized stratified squamous
What is the epithelium covering the nasal cavity and nasopharynx?
Respiratory epithelium
Describe the epithelium of the anterior 2/3rd of the tongue?
Stratified squamous epithelium, thin on ventral surface, thick and with papillae on the dorsal surface.
Describe the epithelium of the posterior 1/3rd of the tongue?
Covered by smooth stratified squamous epithelium which, except for the circumvallate papillae, lacks papillae but does have substantial lymphoid aggregates in the submucosa
What are the 4 different types of tongue papillae?
Filiform - no taste buds
Fungiform
Foliate
Circumvallate - vallate
Describe the layers of the digestive tract?
Mucosa
Submucosa
Muscular externa
Serosa/adventitia
Describe the mucosa further?
Mucosa
- epithelium - sits on basal lamina
- lamina propria - loose connective tissue
- muscular mucosal - thin layer of smooth muscle
Describe the submucosa further?
Loose connective tissue
Describe the muscular externa further?
Two thick layers of smooth muscle, an inner circular layer and outer longitudinal layer
Describe the serosa/adventitia further?
Outer layer of connective tissue that either suspends the digestive tract or attached it to organs
Describe what happens at the gastro-oesophageal junction?
There is an abrupt transition from stratified squamous epithelium of the oesophagus to columnar epithelium of the cardia of the stomach
What are gastric pits?
Pits in the stomach, at the bottom of the gastric pit is a gastric gland.
What are gastric pits lined by?
Surface mucous cells
Describe what cells are in the gastric gland?
Isthmus
Neck
Base
Isthmus - mostly parietal cells
Neck - mostly mucous cells and stem cells
Base - mostly chief cells with a few parietal cells and endocrine cells
What do chief cells produce?
Digestive enzymes
What do parietal cells produce?
HCL
Describe the mucosa differences in the different regions of the stomach?
Cardia
Body
Pylorus
Cardia - Deep gastric pits that branch into loosely packed, tortuous glands.
Body - Shallow gastric pits with long straight gastric glands.
Pylorus - Shallow gastric pits with long straight gastric glands.
What is found in some areas of the stomach in relation to the muscular externa?
An extra layer is found oblique to the circular and longitudinal layers and is located internal to the circular layers
It aids the churning action of the stomach
Describe the transition at the gasproduodenal junction?
From stomach mucosa to duodenal mucosa
Describe the surface of the small intestine?
Finger like projections - villi and between the villi are pits called the crypts of lieberkuhn
What type of glands does the duodenum contain?
Brunners glands in the submucosa
What is the ilium characterised by?
Aggregations of lymphoid follicles called Peyer’s patches found in the submucosa and sometimes extending into the lamina propria
What do the Brunner’s glands do int he duodenum?
They are stimulated by the presence of chyme and they produce a thin, alkaline mucous to neutralise the chyme
Where are Peyer’s patches most commonly found?
In the Ileum
What are the two principle types of cells found in the large intestine?
Absorptive cells - for removal of salts and water
Goblet cells - for the secretion of mucus to lubricate the colon
How are the 2 principle types of cells in the large intestine arranged?
In straight, tubular glands, referred to as crypts that extend down to the muscular mucosae
Describe the outer longitudinal smooth muscle of the large intestine?
It is found in 3 muscular distinct strips called teniae coli
Describe the structure of the appendix?
Similar to the rest of the colon - crypts are less abundant
Describe the transition at the rectoanal junction?
Mucosa of the rectun to the stratified squamous epithelium of the anal cancel
Where do the neurones in the myenteric plexus live?
In the layers of the muscles of the muscular externa
Where do the neurones in the submucosal plexus live?
In the submucosa
What 2 plexus make up the ENS?
myenteric plexus and submucosal plexus
What is the function of the submucosal plexus?
To control the muscle of the muscular mucosa and also help regulate secretion in the epithelium
What is the function of the myenteric plexus?
Controlling gut motility
What do the enter-endocrine cells break down into?
Different cells, such as K, G, I, S cells
What do I cells secrete?
CCK and they are located in the duodenum and jejunum. They modulate bile secretion, exocrine pancreas secretion, and satiety
What to G cells secrete?
Gastrin, and stimulate gastric acid secretion found in the stomach
