GI 1 Flashcards
what are the FOUR functions of the GI tract
digestion. absorption, excretion and host defence
where does digested food go to after the intestine
blood or lymphatic system
what is excreted
non absorbable components of food, drugs, steroids, cholesterol
true or false - the immune system of the GIT is highly developed
true
what makes up the small intestine
duodenum, jejunum and ileum
pick the odd one out
-> the accessory organs are the pancreas, bladder and esophagus
esophagus -> liver
what is the mucosa made up of
epithelium, lamina propria and muscularis mucosa
what are the 4 structures of the GIT
mucosa, submucosa, muscularis externa and serosa
what kind of junctions make up the epithelial layer
tight junctions
how is the epithelial layer polarized
one surface is different compared to the other - basolateral and apical arrangement -> different transport proteins
the epithelial layer provides selective uptake of _______
nutrients, electrolytes and water
what can pass through tight junctions
water and small ions
describe the lamina propria
made of connective tissue, small blood vessels, lymphatic vessels and immune cells
what kind of muscle is the muscularis mucosa made up of
smooth muscle
true or false - muscularis mucosa is involved in contraction of the GIT
false
true or false - the submucosa is made up of connective tissue
true
what are the similarities between submucosa and lamina propria
made up of connective tissue, blood and lymphatic vessels
what is the importance of the submucosa
contains nerve cell bodies that relay information to and away from the mucosa
which part of the GI tract regulates muscle function
the muscularis externa
how are the fibres in the inner and outer layer of muscle in the muscularis externa oriented
inner layer - fibres oriented to cause narrowing of lumen
outer layer - fibres oriented to shorten tube
describe the serosa
made up of connective tissue, covers the intestine and forms a connection point to the abdominal wall
how does the blood flow to the liver
through the portal vein
what are the two purposes for the portal circulation
remove wastes and process nutrients
true or false - the liver receives a lot of oxygenated blood
false - it carries more nutrient rich blood and less oxygenated blood
what are the 4 ways the GI reflexes are initiated
- distension of wall
- pH of contents
- osmolarity
- concentration of digestion contents
what are the three receptors important to the GIT
mechano, osmo and chemo
what is the name of the two nerve networks in the GI process
myenteric and submucosal plexus
true or false - the submucosal plexus influences the smooth muscle
false - it influences secretion
true or false - the myenteric plexus influences smooth muscle
true
match the description to the correct chemical messenger
hormone secreting gland cell -> target cells in one or more distant places in the body
endocrine
how do the autocrine chemical messengers work
autocrine substance acts on same cell that secreted the substance
how do paracrine chemical messengers work
target cells in close proximity to site of the release of paracrine substance
name the four GI hormones
secretin, CCK, gastrin and glucose dependent insulinotropic peptide
true or false - most GI hormones affect only one type of target cell
false - they affect more than one type
what are the functions of CCK
stimulates pancreas to increase digestive enzyme secretion and gall bladder contraction
describe the negative feedback control system of CCK
fatty acids and amino acids triggers secretion of CCK into blood -> absorption of fatty acids and AAs which stops secretion of CCK
match the major release site to the major hormone
gastrin
stomach antrum / G cells
match the major release site to the major hormone
secretin
small intestine
match the major release site to the major hormone
CCK
small intestine / I cells
match the major release site to the major hormone
Glucose dependent insulinotropic peptide
small intestine / K cells
gastrin -> increase or decrease motility/HCl
increase HCl and motility
secretin -> increase or decrease motility/HCl
decrease HCl and motility
CCK -> increase or decrease motility/HCl
decrease HCl and motility
what is the major action of GIP
increases insulin
what causes the movement of contents of the stomach
contraction and relaxation of the two outer smooth muscle layers of the GIT
explain pacemaker cells
-> found in the GIT
-> constantly undergoing spontaneous depolarization/repolarization cycles
the slow waves of the pacemaker cells are the _________
basic electrical rhythm
what kind of neurotransmitters further depolarize the membrane
excitatory neurotransmitters
how is the frequency of contraction maintained
through the basic electrical rhythm
true or false - the number of action potentials fired is proportional to the force of contraction
true
