GI tract overview Flashcards
What are the different cavities in the body?
What are the standard 4 layers of the GI tract?
Mucosa= lining of the tract
Submucosa= connective tissue where blood vessels and nerves lie
Muscularis= layers of smooth musclr and nerves
Serosa= smooth visceral layer
What can be absorbed in the mouth and why is that important?
GTN spray and alcohol
Important as the bloodstream connects straight to the systemic circulation, which is different to the rest of the gut which goes into the portal system to the liver
What purpose does the mouth have?
Key for mastication, speech, starts digestion (amylase) and some absorption
What 3 areas is the pharynx divided into?
Nasopharynx
Oropharynx
Laryngopharynx
What is peristalsis?
Process by which a food bolus gets from one end of the GI tract to the other
It is involuntary
Muscles contract and push food down while muscles in front of the bolus relax and allow it to pass
Not based on gravity
What cells line the oesophagus?
Lined with stratified squamous epithelium (thick and robust) until the last 1cm when it becomes columnar epithelium
Seperated by the z line
SE= paler, CE= pinker
Are the muscles voluntary or involuntary in the oesophagus?
Voluntary (striated) in upper 1/3
Involuntary (smooth) in lower 1/3
Mixed in middle
What are the functions of the upper and and lower oesophageal sphincter?
Upper= stops air getting into gut
Lower= prevents food/acid reflux
What are the two types of hiatal hernia?
Sliding= more common, sphincter has loosened and stomach as moved up into thoracic cavity
PO= less common, separate diaphragmic defect where the stomach moves up next the oesophagus
They are not worrying, but does increase the chance of reflux
What is the function of the stomach?
Breaks down food into a slurry/chyme
What is the wall of the stomach like?
The mucosa is folded into rugae (folds) and within these are gastric pits
What are different parts of the stomach?
What are the different elements that are secreted into the stomach?
Glands= secrete mucous to protect the wall from the acid
Chief cells= secrete pepsin (enzyme that breaks down proteins)
Parietal cells= secretes HCl and intrinsic factor
Endocrine cells= secrtes grelin and gastrin (digestive hormone)
What is grelin?
A hormone which promotes appetite
What does intrinsic factor allow?
Intrinsic factor is a protein that helps your intestines absorb vitamin B12
What are the 3 parts of the small intestine?
Duodenum= first
Jejunum= second
Ileum= third
What are the 4 areas of the duodenum?
4 sections- directions
Straight (superior) then descending (this is where pancreas exits at sphincter of oddi) then horizontal and ascending then the DJ (duodenum jejunum) flexure
Where does the ileum end?
The ileo-caecal valve in the right iliac fossa
What is the mucosa of the small intestine folded into?
Villi
What is found between the villi in the small intestine?
Crypts of pluripotent cells which replenish the villi cells in an upwards conveyer belt fashion
What are enterocytes?
Enterocytes, or intestinal absorptive cells, are simple columnar epithelial cells which line the inner surface of the small and large intestines
Have microvilli on them- known as the ‘brush border’
What are the different sections of the colon/large intestine?
-Caecum
-Colon (ascending, transverse, descending and sigmoid)
-Rectum
-Anal canal
When does the columnar epithelium start and end in the GI tract?
Start- z line in oesophagus
End- anal canal
Before and after= squamous
