GI 2 Flashcards
What is digestion?
a)the absorbtion of water and various other substances into the body
b)the mechanical and chemical breakdown of food
c) the movement of food through the digestuve system
d) all of the above
the mechanical and chemical breakdown of food
what are the 4 functions/processes of the digestive system
digestion
secretion
absorbtion
motility
what are some challenges of the digestive system
Avoiding Autodigestion: not damaging our own cells
Mass Balance: we secrete a lot more than we ingest
Defense: absorbing stuff without bacteria and viruses (lyphocytes protect us)(80% in small intestine)
name 3 fluid secretions
water
digestive enzymes
mucus (goblet cells in intestine)
motility
refers to the movement of material through the GI tract as a result of muscle contraction
two purposes of motility
- moves food from mouth to aus
- mechanically mixing food breaks it into uniformly small particles
where do you see tonic contrations
sphicters
where are you most likey to see phasic contractions?
esophagus, posterior region of stomach, small & large intestines
slow waves
slow waves are modified by chemical input from nerons, hormones, paracrine signals. THER ARE CONTINUIOUS
which layer of the GI tract contains the portion of the ENS that interacts with epithelial cells lining the lumen?
mucosa
sub,ucosa
muscularis extarna
serosa
submucosa -
there are 2 nerve networks that make the the ENTERIC NERVOUS SYTEM (ENS)
intersitial cells of Cajal (ICC)
they found pacemaker cells in the GI tract
they called it Interstitial cells of CAJAL
they serve to slow wave activity and will spontaneuosly depolarize
3 main patterns of motility
1) MIGRATING MOTOR COMPLEX (motilin)
2) PERISTALTIC CONTRACTIONS
3) SEGMENTAL CONTRACTIONS
1) MIGRATING MOTOR COMPLEX (motilin)
cycles/contrations that empty the GI tract between meals. begins at stomach and ends at ileum
-2hours after eating (first quiescent 45-60mins)
-20-30min period of infrequent peristalitic contactions (procced in a forward diretion)
-5-15min cycle rapid forceful contractions
2) PERISTALTIC CONTRACTIONS
wave pushing everything forward.
3) SEGMENTAL CONTRACTIONS
small segments alternatively contact and relax circular and longitudinals (churns and mixes stuff)
Which can GI REGULATE??
motility
absorbtion
secretion
digestion
motility and digestion
secretion and motility
secretion and motility - regulated by NEURAL & GI PEPTIDES
Enteric Nervous system
made of 1. submucosal and 2. myenteri plexus form the ENS
500 mill nerons (HUGE) largest part of peripheral ervous system that controls GI tract
is a part of the peripherical NS but acts more like the Central NS
short reflexes
short relfexes integtrate into the ENS
this is why people call it its own nervous system - cuz it dont need a brain (autonomous)
there are also long relexes
GI PEPTIDES
alter motility and secretion (inhibit and excite)
inculdes
-hormones (some can act as paracrine signals)
-neuropeptides
-cytokines
commonalities with ENS and CNS
intrinsic neruons: entirly within the GI tract - smililar to the interneurons in the Central NS
neurotransmitters and neuromodulators - many identical to CNS
glial support cells - similar to astrocytes
diffusion barrier - like blood gut barrier
*intergrating center - can function autonomously
myenteric plexus
motility part of the ENS
submucosal plexus
secretion from GI secretory cells part of the ENS
cephailc reflex
a long relfex the begins in the brain - can happens from smelling food, seeing food, thinking about food.
this stimulus can effect motility in the GI tract
_____ nervous system enhances GI functioning
parasymathetic NS
_____ nervous system inhibits GI functioning
sympathetic NS
Which region of the GI tract contains a very large amount of bacteria?
esophagus
stomach
small intestine
large intestine
large intestine! - cuz it is less leaky and HUGE
