Gastrointestinal Tract Flashcards
Organs of upper GI
Salivary gland
Esophagus
Stomach
Small intestine (ending at duodenum)
Lower GI organs
Small intestine (jejunum and ileum)
Large intestine
Rectum
And accessory organs - liver, pancreas, gall bladder
What are the four layers of the GI?
1) Mucosa - consists of mucous membrane, lamina propria, and muscularis mucosa
2) Submucosa
3) Muscularis externa - consists of inner circular muscle and outer longitudinal muscles
4) serosa (or adventitia)
Structure of the mucosa
Consists of:
1) epithelium
2) lamina propria
3) muscularis mucosa - allowing for localized movement of mucosa, not peristalsis
Has the most variability in the GI tract
Function of the mucosa
Is the innermost layer that surrounds the lumen and is in direct contact with food and products of digestion
Therefore function is protection, absorption and secretion
It is highly specialized in each GIT organ
- e.g. in stomach must produce mucus to withstand pH, in large intestine it must absorb water and produce mucus
Specializations that exist in the mucosa of the GIT?
Villi, glands/crypts, lymph nodules (GALT and MALT as well as Peyer’s patches in the ileum)
Structure and function of the Submucosa
It is dense irregular CT containing large blood vessels, lymphatics and nerves
- has Submucosa glands in some locations, and Submucosa plexus (division or enteric nervous system)
Structure of muscularis externa of GI tract
Has a layer of inner circular muscle and outer longitudinal muscle
Function of Muscularis externa of GI
Inner circular layer - unidirectional movement (pinches and segments things)
Outer longitudinal layer - shortens the tract
Together = peristalsis
Between the two layers if the myenteric plexus (enteric division of ANS)
Serosa of GTI - structure and function
Is a layer of CT covered by mesothelium (a single layer of squamous cells)
- secretes serous fluid that lubricates and reduces friction between parts of GI
- equivalent to visceral peritoneum
- most of GI organs have a serosa
Adventitia of GI:
- structure
- function
- prognosis of cancer
A layer of CT without mesothelium
- functions to bind structures together (such as in the oral cavity, ascending and descending colon, and rectum)
- cancers in tissues with adventitia are usually poor in comparison to serosa tissues due to the fact that its easier for cancers to spread through them as there is no layer of cells with a BM
Staging of Esophageal cancer:
PT1
- pT1a
- pT1b
PT2
PT3
PT4
PT1 - tumour invades lamina propria, muscularis mucosae or submucosa
- PT1a - tumour invades lamina propria or muscularis mucosae
- PT1b - tumour invades submucosa
PT2 - tumour invades muscularis propria
PT3 - tumour invades adventitia
PT4 - tumour invades adjacent structures
Esophagus - structure and function
- epithelium type
Has a mucosa that is stratified squamous non-keratinized epithelium
Has a submucosa that contains mucus glands (but no mucus layer exists)
Muscularis externae
Serosa or adventitia
Stomach - structure and function
- epithelium type
Has:
1) mucosa - columnar epithelium with glands and pits
2) submucosa - Submucosa plexus
3) muscularis externae - myenteric plexus
4) serosa
Stomach - Gastric Glands
- what type of cells exist here?
- functions of these cells
Surface mucous cells - secrete mucus
- also extends into the put itself
parietal cells - produce HCl
Chief cells - produce pepsinogen
