Lecture GI tract

Lecture the gastrointestnal system
 Overview of functon GI tract : 
o Chew the food,
o Lubricate saliva
o Transported
o Stomach acid mixes with food.
o Digeston and reabsorpton in
intestnes.




 Fluid in the small intestne:
o 2 L food
o 1,5 L saliva
o 2 L gastric juice
o 2 L pancreatc juice /bile
o 1 L small intestnal secreton
 Big load of small intestne from -10 litres
o Reabsorbed: 6.5 L
o Presented to colon: 2 L
o Reabsorbed: 1.9 L
o Colon excreton feces) +/- 200 g
 On average you consume 2 litres of food, includes fuids.



 Structure of the lecture:
o Digestve secretons
o GI motlity
o Neural and hormonal regulaton
 Digestve secretons
o Starts in the mouth  saliva  lubricaton in
mouth, otherwise our mouth is very dry and it is
difcult to mix with the food.
o Lubricaton is do due the mucins in saliva: these
are glycoproteins.
o The digeston starts because there is some
amylase produced and a litle bit of lipase.  litle bit of fat digeston.
o We do also have a lot of antmicrobial proteins in our saliva, this is to protect
us against for example bacteria. also the water content helps with
protecton)
o Ph is litle bit basic to protect us against acid food.
 Parotd  serous amylase and lipase)
 Sublingual  mainly mucous, bit serous glycoproteins)

,  Submandibular  serous/ mucous
 Ions, water, mucins, a amylase, lipase, antmicrobial proteins.
 Lubricaton, dissolving, start
digeston, protecton.
o Secretory unit of saltatory gland 
o The head of the gland is visible `9 the upper part
with the bigger cells, and the acinus.
o The head is responsible for the primary secreton:
 Ions, mucous proteins, enzymes and the
antmicrobial proteins
o Then we have the duct cells:
 Rate of secreton is slow, tme for
reabsorpton in the duct cells.
 Sodium and chloride
o Sodium is absorbed in
exchange for potassium.
o Chloride is absorbed in
exchange for Bicarbonate.
 Slow secreton rate: hypotonic
 High secreton rate: hypertonic  actve secretng of. Bicarbonate.
Less acid.
o Secreton in the stomach:
 Stomach depicted: Stomach upperpart; fundus part.
 The big corpus: The body, we also call it the oxyntc mucosa.
 Oxyntc: the acid secreton part
 The antrum part.
 Diferent regions in the stomach: the region where the acid is secreted
and the region with the more regulatory functons.
 Folds in the layer and glands.
 A lot of cell types in glands:
o Superfcial epithelial cell bicarbonate, mucous
 Bicarbonate to countract the acid

,  Very watery mucous secreton.
o Mucous neck cells/ goblet cells  mucous
 protecton
o Parietal cells/oxyntc  HCl, intrinsic factor,
gastroferrin
 Intrinsic factor is needed for the absorpton of
vitamin B12, this is needed for maturaton of red
blood cells.
o Chief cells  pepsinogen and lipase
 Actvated to pepsin
o Endocrine cells  gastrin, histamine, somatostatn
 Peptde hormones for regulaton

 Functon of gastric acids
o Protecton of gastric mucosa.
o Acid: ph below 2
 Actvates pepsinogen
 Denaturaton proteins
 Protecton against bacteria
o Mucosa needs to be protected against the acid.  Alkaline mucus layer
 Mucous secreted by neck cells.
 Chemical and mechanical protector.
o Inhibits prostaglandin synthesis  paracetamol /
ibuprofen.
 Prostaglandin: stmulated the mucous secreton
and acid secreton.
 small intestne: