Unit 6 A Flashcards
what are the 3 wordy functions of the GI system
- be able to digest macromolecules but not itself
- allow entry for nutrients but not pathogens
- maintain water balance
what are 5 protection methods the Gi tract uses to prevent pathogens from getting in
- epithelial barrier
- mucus
- digestive enzymes
- acid
- Gut Associated Lymphoid Tissue (GALT)
what are peptic and duodenal ulcers?
no barrier or sores on GI lining
what 4 things make up the GI and what is the order for the intestines
stomach
small intestine: duodenum -> jejunum -> ileum (the most digestion occurs here)
large intestine- colon -> rectum
esophagus
what are the four layers in the GI tract wall ?
- Mucosa
- Submucosa
- Smooth muscle layers
- Serosa
what is the serosa and what is it made up of ?
its the outermost covering of the GI tract wall made up of epithelium
what is the smooth muscle layer of the GI tract and what is it made up of ?
its the 2nd outer wall of the GI made up of the circular and longitudinal muscle and auerbach plexus nerve
what is the submucosa and what is it made up of ?
is it the middle layer of the wall and it is made up of connective tissue and contains the meissner plexus nerve (yellow) and large blood vessels
what is the mucosa and what is it made up of ?
the mucosa is the most inner lining of the GI and it is made up of the epithelium, lamina propria which holds the epithelium in place and muscularis mucosa
what are 4 main functions of the GI tract ?
- motility
- secretion
- digestion
- absorption
what are 3 patterns of gut motility contraction and explanation?
- peristalsis- moving food from mouth to anus
- segmental- mixing/churning
- migrating motor complexes-sweeps tract
what is the mechanisms for peristaltic contraction ?
continuous pinching and relaxation of the muscle that pushes the bolus fowards to the anus
what is the mechanisms for segmental contraction ?
alternate segment of contraction that has little or net forward movement that allows for mixing of the intestinal content
what type of muscles mainly makes up the GI tract and what are the two types of controls over the muscle
single unit smooth muscle has tonic and phasic contraction
what is the tonic controls and affect of the single unit muscles and where it occure
it is contracted for minutes to hours and occur in smooth muscle sphincters and keeps food from moving backwards
what is the phasic control and affect on the single unit muscles and where it occurs
it is for a few seconds and happens in the posterior stomach and small intestines
what happens between meals ?
migrating motor complexes sweep down the tract when it is largely empty with a series of contraction for 90 minutes from stomach to large intestine
what happens during/after meals ?
peristaltic and segmental contractions
what attaches smooth muscles to becomes single unit muscles ?
they are coupled by gap junction
what are slow wave potentials ?
its depolarization and repolarization controls the cycles of smooth muscles contraction as it fires APs
what happens to slow waves below and above threshold
blow threshold there is no contraction
above threshold voltage ca channels open and Aps are fired and contraction occurs
how is the amount of contraction determined ?
it is dependant on the amount of Ca that enters which is a longer wave larger contraction
what are the 3 things the influences calcium volume?
- neurotransmitters
- hormones
- paracrine factors
what 4 things are secreted ?
- water and ions -secreted in lumen and reabsorbed
2.enzymes - mucus
- saliva
how acid secreted and where is it done ?
acid (H+) is secreted in into the lumen of the stomach whilst biocarb is moved to the interstital fluid and this all occurs in parital cells
what the difference of pH between the lumen and parietal cells ?
the lumen is low as pH1 and parietal is approx 7.2 ph
what is the 4 step pathway for NACL secretion ?
where does NaCl secretion occur ?
small intestine,colon,salivary glang
