physiology - general Flashcards
what is motility
mechanical activity mostly involving smooth muscle (skeletal muscle is involved in mouth to upper oesophagus and anal sphincter)
what is digestion
chemical breakdown by enzymatic hydrolysis of cole foodstuffs to smaller, ABSORBABLE units
what is absorption
transfer of the absorbable products of digestion from the digestive tract to the blood or lymph
what does circular muscle contraction cause in the GI tract
lumen becomes narrower and longer
what does longitudinal muscle contraction cause in the GI tract
intestine becomes shorter and fatter
what does muscularis mucosa contraction cause in the GI tract
change in absorptive and secretory area of mucosa (mixing activity)
how many sphincters are there? name them
- upper oesophageal (UOS)
- Lower oesophageal (LOS)
- pyloric sphincter
- ileocaecal valve
- internal anal sphincter
- external anal sphincter
which sphincters are comprised of smooth muscle
Lower oesophageal (LOS) pyloric sphincter ileocaecal valve internal anal sphincter
which sphincters are comprised of skeletal muscle
upper oesophageal (UOS) external anal sphincter
what are the organs associated with the alimentary canal
mouth and oropharynx
oesophagus
stomach
small intestine (duodenum, jejunum, ileum)
large intestine (caecum, appendix, colon)
rectum and anus
what are the accessory structures associated with the alimentary canal
salivary glands
pancreas
liver and gall bladder
what are the major motility patterns in the GI tract (5)
peristalsis segmentation colonic mass movement migrating motor complex tonic contractions
what is peristalsis
a wave of relaxation followed by contraction that normally proceeds along the gut in an aboral direction
what triggers peristalsis
distension of the gut wall
what is tonic contractions
sustained contractions
low pressure = organs with major storage function (e.g stomach)
high pressure = sphincters
what is migrating motor complex
powerful sweeping contractions from stomach to terminal ileum
what is colonic mass movement
powerful sweeping contraction that forces faeces into the rectum
what is segmentation
(mixing/churning)
rhythmic contractions of the circular muscle layer that mix and divide luminal contents
stimulation of the parasympathetic innervation of the GI tract causes what
increased gastric, pancreatic and small intestinal secretion
increased blood flow
increased smooth muscle contraction
inhibition of the parasympathetic innervation of the GI tract causes what
relaxation of some sphincters
receptive relation of the stomach
stimulation of the sympathetic innervation of the GI tract causes what
increased sphincter tone
inhibition of the sympathetic innervation of the GI tract causes what
decreased motility
decreased secretion
decreased blood flow
who does electrical activity occur in the stomach, small and large intestine
slow waves
detailed: rhythmic patterns of membrane depolarisation and repolarisation that spreads from cell to cell via gap junctions
what does the slow wave electrical activity determine
max frequency, direction and velocity of rhythmic contractions
basic electrical rhythm (BER)
what is the slow wave electrical activity driven by
interstitial cells of cajal (ICCs)
pacemaker cells are also interspersed between the smooth muscle cells
when would contraction occur (in relation to slow wave)
if the slow wave amplitude is sufficient to trigger SMC AP
where is the enteric nervous system (ENS) located within the GI system
myenteric (Auerbach’s) plexus
submucous (Meissner’s) plexus
where is the enteric nervous system (ENS) located within the GI tissue
intrinsic
