What is the overview of the structure GI tract?
- pharynx
- oesophagus
- liver
- stomach
- duodenum
- transverse colon
- ascending colon
- descending colon
- small intestine
- caecum
- appendix
- sigmoid colon
- rectum
- anus
What is an overview of the internal GI tract from in to out?
MUCOSA:
- epithelium
- lamina propria
- muscular mucosa
SUBMUCOSA
- nerves
- blood vessels
- supporting connective tissue
MUSCULARIS PROPIA
- inner circular layer
- outer longitudinal layer
- third inner oblique layer (stomach only)
ADVENTITIA
What are the types of mucosa that can be found in the GI tract?
- protective
- secretory
- absorptive
Where can the protective mucosa be found?
- oesophagus
- anal canal
Where can the secretory mucosa be found?
- stomach
- small intestine
- large intestine
Where can the absorptive mucosa be found?
- small intestine
What is special about the whole large intestine?
- it contains both absorptive and protective mucosa
What kind of epithelia does protective mucosa have?
- stratified squamous epithelia
What adaptations does absorptive mucosa have?
- microvilli which increase the surface area
What is the oesophagus?
- a muscular tube that transports food from the mouth to the stomach
- it is lined by non-keratinised squamous epithelium
How does the oesophagus move?
- transport is driven by peristaltic contractions
- the upper and lower oesophageal sphincter contribute to food movement control
What type of muscle does the oesophagus contain?
- skeletal muscle = voluntary control at the top
- smooth muscle = involuntary control as you go further down
Where are the mucus secreting glands within the oesophagus?
- within the sub-mucosa there are oesophageal glands which are mucus secreting glands
- near the stomach, oesophageal cardia glands in the lamina propria secrete mucus
Why is the epithelium in the oesophagus so folded in?
- so that it can stretch when transporting food
What is the gastric-oesophageal junction?
the junction between the oesophagus and the stomach mucosa, which abruptly changes from protective mucosa to glandular secretory
What are the changes in epithelium?
It changes from stratified squamous epithelium in the oesophagus to simple columnar epithelium in the stomach until the anus
What are some of the regions of the stomach?
- the cardia
- the fundus
- the pylorus
What is the gastric cardia?
- a narrow circular band <1.5-3cm
- Mucosa contains simple or branched cardiac glands, coiled with large lumens
- Most of the glands produce mucus and lysozyme (attacks bacterial walls/breaking down pathogens)
- A few parietal cells are also found (HCl secreting)
- The glands are similar to the cardiac glands of the oesophagus
What does the cardia contain?
- the cardia contains mucus secreting glands.
- The glands secrete two types of mucus and associated endocrine cells secrete gastrin.
- Glands secrete acid - pepsin as well as mucus
What is the fundus?
- contains the lamina propria
- which contains gastric glands
What are the main areas of the gastric glands?
- isthmus
- neck
- base
