Upper GI Tract Structure and Function Flashcards
Why chew
Prolong taste experience
Defence against respiratory failure
Voluntary control of chewing
Somatic neves control the skeletal muscle of the mouth and jaw
Reflex control of chewing
Contraction of jaw muscles => pressure of food against gums, hard palate and tongue => mechanoreceptors => inhibition of jaw muscles => reduced pressure => contraction => etc
Salivary glands
Parotid
Submandibular
Sublingual
Components of saliva
Water Mucins Alpha amylase Electrolytes Lysozyme
Water
Softens, moistens, dilutes particles
Solvent
Mucins
Major protein component
Mucins + water = mucus
Viscous solution
Alpha amylase
Catalyses breakdown of polysaccharide (starch, glycogen) into disaccharide (maltose) + glucose
Electrolytes
Tonicity/pH
Lysozyme
Bacteriocidal - cleaves polysaccharide component of bacterial cell wall
Control of salivary secretion
By sympathetic and parasympathetic NS
Both stimulatory
Parasympathetiic control of salivary secretion
Cranial nerves VII (facial) & IX (glossopharyngeal)
Stimulation => profuse watery salivery secretion
Sympathetiic control of salivary secretion
Stimulation => small volume, viscous salivary secretion
High mucus content (alpha1 adrenoceptors)
High amylase content (beta2 adrenoceptors)
Reflex control of salivary secretion
Presence of food in mouth => chemoreceptors/pressure receptors (walls of mouth/tongue)
Swallowing
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