Term
| what are the accessory organs to be covered in GI? |
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Definition
| salivary, liver, pancreas -> all the exocrine function of the particular organ |
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Term
| what is the lining of the exocrine glands involved in the GI continuous with? |
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Definition
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Term
| besides ingestion and digestion, what are other major functions of the GI? |
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Definition
| prehension (limbs bringing food to the mouth), fragmentation, propulsion (mostly via peristalsis) |
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Term
| what is the universal secretion in the GI? |
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Definition
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Term
| what is the most extensive neural network in the body? |
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Definition
| the GI tract's neural network |
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Term
| what are the 2 systems in place for control and regulation of the digestive system? |
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Definition
| external influences (local influences) and extrinsic autonomic nerves (intrinsive nerve plexus, smooth muscle, and GI hormones) |
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Term
| what are the only "true" sphincters in the GI? |
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Definition
| the upper esophageal and the external anal sphincter - b/c they are composed of skeletal muscle, (the other smooth muscle sphincters are not as strong) |
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Term
| what is the difference between control and regulation of the GI? |
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Definition
| control of the GI determines whether the activity will occur, while regulation determines how it occurs (if lost, things will start to happen randomly) |
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Term
| does the extrinsic autonomic nervous system control or regulated the GI? |
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Definition
| regulate (responsible for coordination of segments) |
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Term
| what kind of action does the parasympathetic system generally have on the GI? |
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Definition
| excitatory, *except for the smooth muscle sphincters (b/c there are different kinds of post neuronal fibers, one that secrets NO - inhibitory and one that secretes ACh - excitatory)* |
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Term
| what are the two nerve plexi found in the GI? |
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Definition
| the myenteric plexus, aka auerbach's which is responsible for motor control and the submucosal plexus, aka meissner's which is responsible for secretion control. *these 2 do communicate* |
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Term
| what are the 2 muscle layers found in most of the GI? what is the exception in the stomach? what is the exception in the large intestine? |
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Definition
| most of the GI has an inner circular and and outer longitudinal, but in the stomach there is also an oblique layer that ensures the stomach is completely emptied. in the large intestine, the longitudinal layer is incomplete = haustra |
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Term
| what do the excitatory autonomic neurons secrete? inhibitory? |
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Definition
| excitatory: ACh, substance P. inhibitory: NO, VIP (vasoactive intestinal peptide) |
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Term
| what happens when the outer longitudinal layer of the GI contracts? inner circular muscle layer? |
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Definition
| when the outer longitudinal contracts, the lumen expands but when the inner circular contracts the lumen becomes more occluded and the segment is elongated |
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Term
| what do both the excitatory and inhibitory neurons involve? |
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Definition
| the dorsal motor nucleus (DMN), excitatory is in the rostral portion and the inhibitory is in the caudal portion |
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Term
| how does a single unit of smooth muscle behave like a functional syncytium? |
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Definition
| via gap junctions (areas of low resistance between cells) that spread waves of depolarization from the *cell of cajal* quickly outward |
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Term
| what is the cell of cajal? how does it function? |
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Definition
| the cell of cajal acts as a pacemaker for unified smooth muscle contractions in the GI as it is more sensitive to NTs and depolarizes first. |
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Term
| where is a large formation/nidus of cells of cajal found? |
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Definition
| in the outer curvature of the stomach, where they set the rate of smooth muscle contraction (3/min in stomach) |
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Term
| can smooth muscle cells be self-excitatory? |
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Definition
| yes with irritation (like w/sharp food) |
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Term
| what are slow waves (basic electrical rhythym - BER)? are they found throughout the GI? |
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Definition
| slow waves/ BERs are resting membrane potentials likely due to speeding up and slowing down of the ATP dependent Na+ pump in the membrane along with Ca++ leakiness. they are at different rates depending on the GI segment, yet all require an AP for contraction (*except in the stomach) and all can be regulated by autonomics |
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Term
| what are the 2 kinds of smooth muscle contraction? |
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Definition
| tonic or prolonged contractions, like when a sphincter needs to be shut for a period of time - these are long bursts of spike APs which allow more Ca++ to come in and interact (can obliterate the smooth wave) and phasic contractions which are varying vacillations between contraction/relaxation |
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Term
| what are the types of GI motility? |
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Definition
| peristalsis, rhythmic segmentation, haustration, and tonic contraction (sphincter action, static ring of contraction, and mass movements of the colon) |
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Term
| what is rhythmic segmentation? |
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Definition
| a mixing type of reaction that exposes the surfaces of food to the enzymes within the mucosal layer of the small intestine |
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Term
| what is digestion as opposed to absorption? |
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Definition
| digestion is the breaking down and transforming of things into an absorbable state (can be mechanical, enzymatic, and hormonally indirect) |
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Term
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Definition
| pouches in the large intestine that squeeze food *back and forth* (not ab-oral) like a cement mixer to expose food to the intestinal wall (haustrations and rhythmic segmentation are essentially the same thing) |
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Term
| what direction does peristalsis move food? |
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Definition
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Term
| are mass movements of the colon considered tonic contractions? |
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Definition
| yes - and mass movements of the colon move food in an ab-oral direction |
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Term
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Definition
| a bitten off chunk of food that goes to the stomach |
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Term
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Definition
| semi-liquefied bolus material in the stomach |
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Term
| what does the bolus do in the esophagus? |
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Definition
| sets of a primary wave of peristalsis by either distention of the lumen or mucosal activation |
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Term
| what does the primary wave of peristalsis consist of? |
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Definition
| 2 signals sent to the gut wall: excitation/contraction behind the bolus and relaxation in front |
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Term
| how are mass movements of the colon detected? |
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Definition
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Term
| what does a mass movement of the colon do? |
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Definition
| these are purely propulsive events that move material in one mass contraction from one segment to the next. they are set up by a parasympathetic reflex arc |
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Term
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Definition
| the process of seizing or grasping food to get it into the mouth, it initiates the oral phase and is fundamental in determining diet selection |
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Term
| what is mastication? what structures does it involve? |
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Definition
| a rhythmic reflex that involves the lips, cheeks, tongue, teeth, and muscles of mastication (masseter - crushes, temporalis - ant pressure, medial pterygoid, and lateral pterygoid) |
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Term
| what is peridontal loading? what does it initiate? |
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Definition
| peridontal loading is the placement of food in the mouth which then initiates reflex inhibition in the muscles of masication |
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Term
| what is reflex inhibition? |
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Definition
| reflex inhibition in when *sensory receptors in the the elevator muscles of mastication (masseter and temporalis) are stimulated by peridontal loading and the lower jaw drops |
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Term
| when the lower jaw drops b/c of reflex inhibition, what does this initiate? |
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Definition
| the lower jaw drop due to reflex inhibition initiates a stretch reflex (depolarization of IA sensory fibers) that leads to a rebound contraction. this rebound contraction automatically causes closure of the teeth. once the teeth have closed, the bolus once again is pressed against the lining of the mouth which causes another reflex inhibition, causing the jaw to drop again and rebound again and so on (= chewing) |
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Term
| what kind of pattern is chewing? |
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Definition
| a central pattern generator - a set of reflexes that free the mind to do other things, but can be overridden by voluntary effort |
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Term
| is mastication affected by muscle wasting disease? |
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Definition
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Term
| what actions does the oral preparatory phase depend on? |
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Definition
| 1) lip closure 2) anterior bolus containment by tongue 3) action of mandibular muscles to chew and cheek muscles/tongue keeping bolus on teeth 4) nasal breathing |
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Term
| how is food texture detected? |
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Definition
| perception of texture is based on sensations perceived when food is manipulated in the mouth by superficial structures around roots of the teeth and in muscles and tendons |
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Term
| what would the oral preparatory phase not be possible without? |
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Definition
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Term
| what are the only glands in the body that are not under hormonal control (not regulation)? what are they under control of? |
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Definition
| salivary glands - which are under control of the autonomic nervous system |
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Term
| what happens if saliva is not produced inadequate quantity? |
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Definition
| the ability of the pt to break down food, mix, release flavor, and swallow will be inhibited - the elderly who have this problem often lose interest in food/food related activities |
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Term
| is saliva produced in much higher levels when around meal time? what about during sleep? |
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Definition
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Term
| what are the 3 primary salivary glands? |
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Definition
| the parotid, submandibular, and sublingual |
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Term
| what characterizes the parotid gland? |
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Definition
| the parotid gland is predominately serous acini and secretes a watery saliva w/amylase to break down starches |
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Term
| what characterizes the submandibular gland? |
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Definition
| the submandibular gland has mixed serous and mucous acinii, so its secretions are thicker as well as contain amylase and a higher Ca++ concentration |
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Term
| what characterizes the sublingual gland? |
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Definition
| the sublingual gland has predominately mucous acini and only a small amount of amylase |
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Term
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Definition
| sympathetics drying out the saliva |
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Term
| what kind of glands are salivary glands? what are the functional units? |
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Definition
| salivary glands are exocrine glands and acini are their functional units |
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Term
| what is essential for bringing the raw material necessary for proper salivary gland function? |
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Definition
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Term
| what is the tonicity of saliva just after production in the acini? |
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Definition
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Term
| what is the tonicity of saliva when it flows out of its ducts? |
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Definition
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|
Term
| how does saliva move down the ducts? |
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Definition
| the salivary ducts are lined by myoepithelial cells, which when they contract, push out saliva |
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Term
| how does saliva move down the ducts? |
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Definition
| the salivary ducts are lined by myoepithelial cells, which when they contract, push out saliva |
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Term
| what is the movement of electrolytes in saliva as it moves through the ducts? |
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Definition
| Na+ is reabsorbed and Cl- follows it. K+ is secreted along with HCO3-. |
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Term
| how does the speed of salivary secretion affect the overall electrolyte composition of saliva? |
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Definition
| HCO3- is passively secreted, and if saliva moving through the ducts slowly it won't pull as much HCO3- out with it (fast saliva = low HCO3-). if the saliva is moving quickly, the Na+ and Cl- pumps work less efficiently and less of each is reabsorbed (fast saliva = more Na+ and Cl-). K+ secretion is constant independent of saliva speed |
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Term
| why is saliva still isotonic if the rate of saliva can affect it's tonicity? |
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Definition
| b/c the rate of K+ secretion is constant, even if the rate of saliva production increases |
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Term
| what is unique about control of salivary secretion? |
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Definition
| salivary secretion is under autonomic control *but* both the sympathetics and parasympathetics are excitatory to the production of saliva |
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Term
| what does parasympathetic stimulation of the salivary glands through the vagus nerve do? |
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Definition
| *increases vasodilation, *secretion (contraction of the myoepithelial cells), and *growth (proven by if parasympathetic innervation is removed, the gland will atrophy) |
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Term
| how can prolonged vasoconstriction due to sympathetic innervation lead to increased salivary secretion? |
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Definition
| increased sympathetic stimulation causes blood flow to be cut off to the salivary gland, but past a certain point, local metabolites build up and dilate the blood vessels, leading to increased salivary secretion (biphasic effect) |
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Term
| what is deglutition? what 2 systems comprise it? |
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Definition
| the act of swallowing, which includes both the GI and pulmonary systems |
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Term
| what is the major process for preventing aspiration of food particles into the lungs? |
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Definition
| tight adduction of the true and false vocal cords |
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Term
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Definition
| the audible voiding of gas from the stomach and esophagus through the mouth |
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Term
| what phases can the normal swallow be subdivided into? which of these is under voluntary control? |
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Definition
| the oral preparatory phase, the oral phase, the pharyngeal phase, and the esophageal phase. the first two are under voluntary control and the second two are under reflex control (involuntary) |
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Term
| what is the tongue important for? |
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Definition
| the tongue is very important for propelling the bolus from an anterior to a posterior position in the oral cavity |
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Term
| when does the pharyngeal phase start? |
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Definition
| the pharyngeal phase is starts when the bolus reaches the anterior faucial arch and the swallowing reflex is triggered |
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Term
| what characterizes the swallowing reflex that is triggered during the pharyngeal phase? |
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Definition
| the nasopharynx closes to prevent aspiration into the nasal passages, the larynx closes and elevates due to hyoid bone movement, the true+false vocal cords adduct to prevent aspiration into the lungs and the upper esophageal sphincter relaxes |
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Term
| why is the apnea incurred briefly during the pharyngeal phase (to prevent aspiration) clinically important? |
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Definition
| pts w/borderline lung function may go into a form of respiratory distress while eating, which leads to a more powerful breathing reflex which can cause a breath at an inappropriate time, leading to aspiration and possibly pneumonia |
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Term
| what triggers the gag reflex? what is the neural signal progression? |
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Definition
| the bolus touching the soft palate, which sends an afferent signal to the glossopharyngeal nerve, which then comes back as an efferent signal through the vagus which tells the muscles in the back of the pharynx to contract |
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Term
| about how long should the swallowing reflex take? |
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Definition
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Term
| when does the esophageal phase start? what happens during? |
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Definition
| the esophageal phase starts when the bolus enters the upper esophagus and is then carried by the primary wave of peristalsis inferiorly to the stomach. once this phase has started, the lower esophageal sphincter opens reflexively - allowing the bolus to pass into the stomach |
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Term
| what happens if the primary wave of peristalsis is not enough to carry the bolus all the way down the esophagus? |
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Definition
| a second (or tertiary) wave of peristalsis occurs *at the site of the bolus (no higher) |
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Term
| how do primary and secondary/tertiary waves of peristalsis differ? |
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Definition
| primary waves start at the top of the esophagus and are generally undetectable, secondary/tertiary waves only start at the level of the bolus and can be detected |
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Term
| how does thoracic cavity pressure compare to atmospheric pressure? how does this affect esophageal pressure? |
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Definition
| thoracic cavity pressure is lower than atmospheric and therefore esophageal pressure is also usually lower than atmospheric - *except for when the upper esophageal sphincter is open and communicating with ambient pressure |
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Term
| what is the pressure in the upper and lower esophageal sphincters and the fundus of the stomach at rest? |
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Definition
| UES+ fundus of the stomach: above ambient pressure, LES: above thoracic pressure |
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|
Term
| what is the general pressure wave associated with swallowing? |
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Definition
| at the time of swallowing, pressure decreases, then increases above normal, then levels out to normal |
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Term
| what is the decrease in pressure accompanying the bolus as it travels down the esophagus and into the stomach referred to as? |
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Definition
| receptive relaxation - so that even before primary peristalsis waves get to the stomach, the pressure gradient is already prepared to receive the bolus |
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Term
| what is the neuronal pathway that makes receptive relaxation possible? |
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Definition
| the subdiaphragmatic vagus nerve (which innervates the LES and stomach) sends a signal to the nodose ganglion, which is then carried to the nucleus solitarius tract and then to the dorsal motor nucleus. from the dorsal motor nucleus, parasympathetics signal release of NO- to the areas which should relax (via the vagus nerve) |
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Term
| what is the "swallowing center"? what is it composed of? what is unique about it? |
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Definition
| the swallowing center (located in the medulla) makes it possible for swallowing and respiration to be integrated and is made up of nonvagal nuclei, nucleus ambiguus (innervates striated muscles) and the dorsal motor neurons. this is a unique place in the body because smooth and skeletal muscle have to be coordinated |
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Term
| what is the approximate deposition of skeletal and smooth muscle in the esophagus? |
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Definition
| the upper third is skeletal, the middle third is mixed skeletal and smooth, and the lower third is smooth |
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Term
| how does the vagus innervate both somatically and viscerally the muscles of the esophagus so that peristalsis can occur? |
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Definition
| somatic vagal innervation synapses on the skeletal muscles while vagal visceral innervation synapses on the myenteric plexus |
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Term
| if a peristaltic wave begins in the smooth muscle portion of the esophagus will skeletal muscle be activated? |
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Definition
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