The Gastrointestinal Tract Flashcards
(37 cards)
What is digestion?
the mechanical and enzymatic process whereby ingested food is converted into simpler, soluble molecules that can be absorbed
What are zymogens?
inactive precursors which are produced initially before digestive enzymes.
They are activated by the cleavage (proteolysis) of a portion of the enzyme, which inhibits the catalytic core of the protein.
What is the pancreas made up of?
- ducts
- lobules
- acini
Where is the Parotid Salivary gland?
behind the tongue
Where is the submandibular salivary gland?
below mandibles
Where is the sublingual salivary gland?
below the tongue
What is the pharynx?
- A complete muscular organ
- Keeps air and digestive tracts separate
- directs food into the oesophagus
What is bolus?
chewed food mixed with saliva
How does stomach acidification work in parietal/oxyntic cells?
-Water and carbon dioxide combine to form carbonic acid, which disassociate to genetarate H+ AND BICARBONATE
-Bicarbonate is exported in exchange for chloride. Chloride and potassium ions are exported in the gastric lumen by conductance channels
H+ are actively pumped out into the gastric lumen in exchange for potassium through the action of the proton pump
What is the inactive version of pepsin?
pepsinogen
how many cleavages are needed to remove the pro-segment?
2
How do you activate pepsinogen?
remove the pro-segment
What keeps the pro-segment in pepsin in place?
electrostatic interactions
What causes the electrostatic attraction in pepsinogen to be lost?
acidic conditions so a pH less than 5
this causes a conformational change that leads to a proteolytic cleavage of the pro-segment
What is the pancreas?
A fundamental digestive gland whose products are poured into the duodenum (small intestine) and are essential for digestion
What counteracts stomach acidity?
Pancreatic fluids
Where is bile produced, stored and what is it produced by?
Liver
gallbladder
hepatocytes
What happens to old red blood cells?
they are eaten by macrophages in a process called phagocytosis
How is bilirubin produced and removed?
- The haem group of haemoglobin is “opened up” and generates: IRON and BILLIVERDIN
- Biliverdin is reduced to bilirubin and released into circulation
- The liver removes bilirubin from the blood and releases it into the bile for excretion
- Bacteria in the gut metabolise bilirubin to urobilinogen
- Urobilinogen can be partially reabsorbed by the gut into circulation
- reabsorbed urobilinogen is filtered by the kidney and excreted in the urine
- it is removed by the liver and released in the bile once again
What is jaundice?
- a yellowish colouring of the skin and sclera
- accumulation of bilirubin in the body
- a sign if liver damage
- caused by haemolysis, obstruction of the bile ducts, dysfunctional liver
What are the 4 different types of bile salts?
- cholic
- deoxycholic
- chenodeoxycholic
- lithocholic acids
How can bile salts be synthesized?
- cholesterol
- extracted from the bloodstream by the liver
What is the function of bile salts?
- detergents to emulsify fats once they reach the small intestine
- prepare fats for the action of pancreatic and intestinal fat-splitting enzymes
What is the pyloric sphincter?
-the sphincters or valves of the digestive system which are muscular rings that control the unidirectional flow of food and digestive juices through the GI tract
