B5.005 - GI Physiology 1 Flashcards
parotid gland
salivary gland 20% of saliva largest, serous, releases saliva on the inside of the cheek across from the second upper molars
submandibular gland
70% of saliva mucous and serous, releases saliva through the floor of the mouth behind the bottom front teeth
sublingual gland
5% of saliva mucous and serous, release fluid from under the tongue
stimuli for salivary gland
cephalic activity, chewing, nausea inhibited during sleep. fear, fatigue
major control of salivary secretions
parasympathetic
what causes vasodilation in salivary glands
VIP ACh
acinar serous cells in salivary glands are stimulated by what
ACh, NE, substance P, VIP
duct cells in salivary glands are stimulated by
ACh and NE
describe saliva relative to plasma
hypotonic relative to plasma, help with tasting of foods, diluting of substances like keeping glucose concentration down
what are mucins
lubricate and modulate adhesions of microorganisms
what do amylases do
break down starch to oligosaccharides
what do proline rich proteins do
they are antimicrobials
what does bicarb do
protects erosion of teeth, neutralizes gastric secretions that reflux into the esophagus
how many muscles and nerves are involved in swallowing
50 muscles and 6 cranial nerves for sensory and motor functions
describe the initiation of swallowing
initiation is under voluntary control while the ensuing sequence of events occur as a pattern elicited response (under involuntary control) which is not a true reflex
how is the swallow divided
oral pharyngeal esophageal phases
oral stage of swallowing
mastication/chewing breaks cell wall of plan tmaterial to expose contents the tongue and cheeks facilitate chewing by moving the food between the teeth food is mixed with saliva and formed into a bolus of the correct size and consistency for swallowing
what does the tongue do in the oral stage of swallowing
facilitates formation, containment and propulsion of bolus
describe the propulsion of food
tip of tongue pressed against the palate lateral regions form seals with alveolar ridges and pharyngeal walls tongue moves in a wave motion along central groove pushing the bolus back towards pharynx anterior 2/3 of tongue and negative pressure in pharyngoesophageal segment are primarily responsible for the driving force propelling the bolus towards the pharynx which results in the temporary suppression of respiration
bolus transit is impaired in what scenarios
following a tongue injury or lanryngectomy
describe neural control of swallowing
signals are transmitted along afferent nerves to the swallowing center in the brainstem the pattern of incoming signals is identified and produces an appropriate set of signals to other neurons that in turn coordinate the muscles involved with swallowing, opening of the upper esophagus sphincter, cessation of breathing and peristalsis in the esophagus
what is the cricopharyngeus muscle
a horizontal striated sphincter muscle located a the top of the esophagus makes up the UES together with non-muscular components
what does the cricopharyngeus muscle do
controls the flow of material between the pharynx and esphagus tonically contracted at rest and relaxes during swallowing, vomiting and belching
describe relaxation of cricopharyngeus
not direct inhibitory signals acting on the muscle, rather inhibition of firing that causes tonic contraction
mechanisms involved in preventing aspiration
prevention of premature spill rapid and coordinated movement of the bolus through the oral cavity and pharynx laryngeal elevation to move out of the way, laryngeal closure, epiglottis inversion bolus that does enter trachea triggers a strong cough
what is dysphagia
difficulty/pain/discomfort in swallowing
consequences of dysphagia
asphyxiation, aspiration pneumonia, dehydration, starvation, weight loss
who commonly gets dysphagia
elderly
symptoms in disorders of oropharyngeal dysmotility
drooling gagging trouble swallowing wet voice hoarseness slow eating coughing choking sore through weight loss dyspnea fever, sweats
describe the functional changes in the oral phase with oropharyngeal dysmotility
abnormal bolus control impaired swallow initiation abnormal bolus transport
describe the functional changes in the pharyngeal phase with oropharyngeal dysmotility
muscle weakness or incoordination pharyngeal outflow obstruction
functional deficites of oropharyngeal dysmotility can be categorized by what
phase of swallowing affected 1. difficulty initiating swallow 2. nasopharyngeal regurgitation 3. pulmonary aspiration 4. residual in vallecula (space between post aspect of tongue and epiglottis)
describe how aspiration occurs
during the swallow there is poor opening of the UES and substantial retention of bolus within the hypopharynx. During a subsequent dry swallow some of this material enters the airway
failure of UES relaxation may be caused by what
neuro disorders like parkinsons amyotrophic lateral sclerosis
impaired opening of UES may be caused by what
cricopharyngeal fibrosis, suboptimal pharyngeal propulsion, neural problem zenkers diverticulum
what is zenkers diverticulum
a structural disorder due to fibrosis of cricopharyngeus muscle resulting in increased intrabolus pressure during swallow
hypopharyngeal intrabolus pressure is an indirect measure of what
UES compliance
what is intrabolus pressure
the obstruction (resistance) to flow across the pharyngo-esophageal junction during swallowing
what is nadir UES
the lowest pressure during relaxation; higher than normal can indicate diminished UES relaxation or diminished opening of UES
zenkers diverticulum
herniation between inferior pharyngeal constrictor and cricopharyngeus
presentation of zenkers diverticulum
disphagia
aspiration
regurgitation
halitosis
noisy deglutition
changes in voice
normal cricopharyngeus muscle
muscle dropout due to necrosis, variability in fiber size, increase in fibroadepose tissu
zenkers diverticulum
results in restricted opening of UES
cricopharyngeal bar
associated with failure of teh cricopharyngeus to relax
when suprahyoid muscles contract the lumen of the open UES is obstructed by the contracted circopharyngeus that appears as a bar
what types of muscle make up the esophagus
striated and smooth
describe the layers of the esophageal muscle from superficial to deep
longitudinal muscle
circular muscle
esophagel glands
submucosa
muscularis mucosae
tunica propria
stratified squamus epithelium
lumen
how long does a swallow last
8-10 s
what is primary peristalsis
continued peristaltic wave from that started in pharynx aka stripping wave
what is secondary peristalsis
if residual food in esophagus, initiated by intrsinsic nervous system and vago-vagal responses. Can have the same strenght and speed as primary peristalsis and is generated in absesce of a swallow
in striated esophagus peristalsis is under what control
central control
in the smooth muscle peristalsis is under what control
intrinsic
describe the biochemical signaling happening to produce a swallow
upon swallowing the inhibitory pathway nuerons in the cuadal DMN are activated first, which acuses simultaneous inhibition of all parts of the esophagus. This inhibition lasts longer in the lower parts than the upper parts. As the inhibition ends, sequential activation of excitatory (cholinergic) neruons in the rostarl DMN elicits a contraction wave that is peristaltic in nature.
describe the excitatory pathway in a swallow
includes vagal preganglionic neruons that are locatd in the rostral part of ht eDMN in the brainstem. Thes fiber project inot the excitatory postganglionic neruons that conatin ACh and substance P.
describe the inhibitory pathway in a swallow
includes preganglionic vagal fibers that are located in the caudal part of teh DMN. The fibers project onto the postganglionic inhibitory neurons that contain NO, VIP and ATP and substance P.
what happens when swallows are performed in rapid succession
the pharynx and UES respond on a one to one basis and the LES remains relaxed. peristalsis in the esophagus is inhibited until after the last swallow.
localized esophageal motor disorders
- achalasia like syndromes
- diffues esophageal spansm
- nutcracker esophagus
- hypertensive LES
diffuse esophageal motor disorders
GERD
scleroderma
myopathies
diabetes
parkinsons
idiopathic pseudo obstruction
hypotensive peristalsis
contractions have a decreased strength leading to impaired esophageal transit
also can have impaired clearance of refluxed contents
main symptom is dysphagia although reflux symptoms may be present or predominate
what labs would demonstrate hypotensive peristaltic contractions
espac eof barium bolus in proximal esophagus due to a weak peristaltic contractionw ave. shows a simultatnesou monometry nd fluoroscopy of a barium swallow
scleroderma esophagus
what is scleroderman esophagus
thought to have autoimmune origin
chronic disorder characterized by diffuse fibrosis of skin and internal organs. Damae to smallblood vessesl are often among earliest signs
what is raynauds phenomenon
reducton of blood flow in response to cold or stress resultin gin idscoloration; white can turn to blue followed by flushing resulting in red appearance
what is telangiectasia
dilated blood vessels near the surface of the skin
what is hypertensive peristalsis
nutcracker esophagus
normal sequence of peristalsis on barium swallow, normal appearance on esophagoscophy, but smooth muslce contractions have excessive amplitude or duration as detected by manometry
symptoms include chest pain, dysphagia
what is diffuse esophageal spasm
inhibitory nerves are disrupted leadin to simultaneous contraction in the smooth muslce of esophagus. contractions occur following swallowing or spontaneously. Deglutitive inhibition is also impaired.
symptoms of diffuse esophageal spasm
chest pain, dysphagia, possible regurgitation
what does a barium swallow of diffuse esophageal spasm look like
simultaneous contractions that appear corkscres, multiple ripples or sacculations
what part of the esophagus is affected by esophageal spasm
the lower part (smooth muscle)
what is deglutitive inhibition
A wave of inhibition precedes a swallow-induced peristaltic contraction in the smooth muscle part of the human oesophagus involving both circular and longitudinal muscles in a peristaltic fashion. Deglutitive inhibition is necessary for drinking liquids which requires multiple rapid swallows
