Alimentary Canal Flashcards
mouth and oropharynx function
chops and lubricates food, starts carbohydrate digestion, delivers food to oesophagus
Oesophagus function
propels food to stomach
stomach function
stores/churns food, continues carb digestion, initiates protein digestion, regulates delivery of chyme to duodenum
small intestine parts
duodenum > jejunum > ileum
small intestine function
principle site of digestion and absorption of nutrients
large intestine parts
caecum > appendix > ascending colon > transverse colon > descending colon
large intestine function
colon reabsorbs fluids and electrolytes, stores faecal matter before delivery to rectum
correct order of structures in digestive tract wall (inside>out)
villus > lamina propria > muscularis mucosae > submucosa > circular muscle > longitudinal muscle > serosa
4 main functions of A.C.
motility
secretion
digestion
absorption
circular muscle contraction…
lumen gets narrower and longer
longitudinal muscle contraction
intestine gets fatter and shorter
how does electrical current get from cell to cell
synchronous wave via
gap junctions
slow waves determine what of the intestinal contractions
their:
frequency
direction
velocity
what drives slow waves
ICCs- interstitial cells of cajal
force of contraction relates to
NUMBER of action potentials sent off
parasympathetic excitatory stimuli =>
increased:
secretion
blood flow
contraction
parasympathetic inhibitory stimuli =>
relaxation of:
specific sphincters
stomach
sympathetic excitatory stimuli =>
increased sphincter tone
sympathetic inhibitory stimuli =>
decreased:
motility
secretion
blood flow
myenteric plexus : location and function?
between circular and longitudinal muscle layers
regulates:
- motility
- sphincters
submucosal plexus : location and function?
between submucosa and circular muscle
regulates:
- epithelia
- blood flow
local reflex
-> myenteric plexus
doesn’t leave gi system
short reflex
-> prevertebral ganglion
long reflex
->brain or spinal cord
during peristalsis what do the muscles do in the PROPULSING segment
longitudinal muscle: RELAXES
- due to VIP and NO
circular muscle: CONTRACTS
- due to ACh and substance P
during peristalsis what do the muscles do in the RECIEVING segment
longitudinal muscle: CONTRACTS
- due to ACh and substance P
circular muscle: RELAXES
- due to VIP and NO
Motility patterns
segmentation/haustration
colonic mass movement
migrating motor complex (MMC)
tonic contractions
segmentation/haustration
circular muscle
rhythmic contractions
mix and divide contents
colonic mass movement
colon
powerful sweeping contraction
forces faeces into rectum
couple times/day
migrating motor complex (MMC)
stomach -> terminal ileum
powerful sweeping contraction
housekeeping role
tonic contractions
sustained contraction
low pressure - organs w storage function eg stomach
high pressure - sphincters
