Wk 7: GI Tract Flashcards
What organs are part of the alimentary canal (GIT) (6)
- Oral cavity
- Pharynx
- Oesophagus
- Stomach
- Small intestine
- Large intestine
Structure of the tongue (accessory organ)
Skeletal muscle covered with a layer of stratified squamous epithelium
What are the projections of the tongue epithelium called & how many types are there
Papillae
4 types
What are the 4 types of papillae
- Filiform (no taste buds)
- Fungiform
- Circumvallate
- Foliate papillae
What are the 4 layers that most regions of the alimentary canal contain
- Mucosa - inner epithelium
- Submucosa - layer of CT
- Muscularis externa - layer of SM
- Serosa - outer layer of CT
What are the 3 components of the mucosa layer
- Epithelium - faces lumen
- Lamina propria
- Muscularis mucosae
What is the epithelium of the mucosa composed of - epithelial type & cells
- Simple columnar epithelium from stomach to large intestine
- Goblet cells
What is the lamina propria of the mucosa composed of - muscle type & others
- Thin layer CT
- Blood
- Lymphatic vessels
- Glands
- MALT
What is the muscularis mucosae of the mucosa composed of - muscle type
- 2 thin layers of SM arranged in different directions
- Inner layer is circular
- Outer layer is longitudinal
Composition of the submucosa of the alimentary canal
- Dense irregular CT
- Blood, lymphatic vessels & submucosal glands
- Nerve clusters of enteric nervous system (branch of nervous system that governs GIT)
What are the nerve clusters of enteric nervous system calles
Submucosal plexus/ Meissner’s plexus
Function of submucosal plexus
Each plexus regulates secretion from & blood flow to area of AC
Composition of the muscularis externa of the alimentary canal
- Compose of 2 SM layer
- Inner circular & outer longitudinal layer
- Groups of nerves of enteric NS regulate motility
What are the nerve clusters of enteric NS found in the muscularis externa called
Myenteric plexus/Auerbach’s plexus
Serosa composition - epithelium & muscle
- Simple squamous epithelial tissue
- Loose CT
Function of serosa
Support & anchor digestive organs
Oesophagus function
To transport bolus from pharynx to stomach
Components of the mucosa in the oesophagus
- Stratified squamous non-keratinised epithelium
- Mucous glands
Components of the submucosa of the oesophagus
- Mucous glands
- Elastic fibres
Components of the muscularis externa of the oesophagus
- 2 layers of muscle (skeletal & smooth)
What happens histologically at the esophagus-stomach junction (gastro-oesophageal junction)
Epithelium changes from stratified squamous epithelium in oesophagus to simple columnar epithelium of stomach
What are rugae
Folds in the stomach so stomach can expand when food is consumed
What is the sphincter entering the stomach & what is the sphincter exiting the stomach
- The sphincter entering the stomach is the gastroesophageal sphincter
- The sphincter exiting the stomach is the pyloric sphincter
Whag does the mucosa of the stomach contain (2)
- gastric pits (columnar cells, goblet cells)
- gastric glands
the 4 main types of cells in the gastric glands
- Enteroendocrine cells
- Chief cells
- Parietal cells
- Mucous neck cells
Functions of the SI
- Secretion
- Digestion
- Absorption
- Propulsion
The 3 divisions of the small intestine
- Duodenum
- Jujunum
- Ileum
What cells line the SI & produce digestive enzymes
Enterocytes
What lymphoid tissue can be found in the SI (small intestine)
Peyer’s patches
What are the 3 types of folding in the SI & where are they found
- Circular folds - mucosa & submucosa
- Villi (mucosa) & Intestinal crypts
- Microvilli
What kind of epithelium are villi & crypts lined with
Simple columnar epithelium
Functions of the folds in the SI
- Slow down movement of chyme - increases time for nutrient absorption
- Increase surface area for absorption
What are the cells in the SI (6)
- Enterocytes
- Goblet cells
- Paneth cells
- Neuroendocrine cells
- Stem cells
- Intraepithelial lymphocytes
Function of enterocytes
Intestinal absorptive cells
Function of goblet cells
Secrete mucous that protects lining of SI
Function of paneth cells
- Located in intestinal crypts
- Secrete abundance of antimicrobial peptides that regulate composition of microbiota
FUnction of neuroendocrine cells
Neuro immune function
Function of stem cells
Restore the cells that need replacing over time
What are the 4 regions of the large intestine
- Caecum
- Colon
- Rectum
- Anus
Function of the caecum
Absorption of water & salts
Composition of colon
- Simple columnar epithelium
- Goblet cells
