Upper GI Tract Structure and Function Flashcards
5 main constituents of saliva
- water
- mucins
- alpha-amylase
- electrolytes
- lysozymes
what is the purpose of water in saliva
to soften the food and dilute it
purpose of mucins in saliva
create mucousy consistency which acts as a lubricant
purpose of alpha-amylase in saliva
to breakdown polysaccharides
purpose of electrolytes in saliva
to maintain tonicity and pH
purpose of lysozymes in saliva
to kill bacteria by cleaving polysaccharides from their cell wall
3 pairs of glands of saliva secretion
parotid, submandibular and sublingual
what parasympathetic nerves stimulate salivation
facial and glossopharyngeal (VII and IX)
which nervous systems saliva is more watery
parasympathetic
which nervous systems saliva has a higher mucus content
sympathetic
which nervous systems saliva has a lower amylase content
parasympathetic
which nervous system produces a higher volume of mucus
parasympathetic
what stimulus acts on the para/symp systems for salivation
food in the mouth acting on chemoreceptors and pressure receptors
roughly how long is the oesophagus
25cm
four layers of oesophagus wall
mucosa, submucosa, muscularis externa and adventitia
what section of the oesophagus has no adventitia
abdominal (i.e. below diaphragm)
what type of epithelium in the oesophagus
stratified squamous
how does the muscle of the oesophagus change from top to bottom
skeletal in the top 1/3
smooth in the bottom 2/3
where is the swallowing control centre
in the medulla, close to the respiratory control centre
describe the process of swallowing
bolus pushed to back of throat by tongue –> pharyngeal reflex triggered –> pharyngeal muscles contract –> nasopharynx close off by soft palate moving up and back –> upper oesophageal spinchter relaxes –> epiglottis covers trachea –> UOS contracts –> perstaltic wave moves bolus through oesophagus –> LOS relaxes –> bolus enters stomach
what is the voluntary action of swallowing
pushing the bolus to the back of the throat by the tongue
what happens to the stomach when the bolus enters it
vagal reflexes triggered by the LOS relaxing causes the stomach to relax its smooth muscle
how long does the oesophageal phase of swallowing last
about 10 seconds
how can the stomach change volume without changing pressure
because it unpleats its folds in wall (rugae)
what is the pH of the stomach
~2
additional muscle layer of stomach
oblique
how does the oblique muscle layer aid digestion
by ‘ringing out’ the contents to create more mixing
stomach anatomy from top to bottom
LOS –> cardiac region –> fundus –> body –> pyloric region –> pyloric sphincter
innermost stomach muscle layer
oblique
outermost stomach muscle layer
longitudinal
