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What are the 3 phases of Swallowing
- Oral: tongue forms bolus - pushes against hard palate
- Pharyngeal: propulsion of bolus from base of tongue to laryngopharynx (primary peristalsis); soft palate pulled up to prevent entry into nasopharynx and epiglottis covers tracheal entrance. Respiration is reflexly inhibited.
- Cricopharyngeal: upper esophageal sphincter (UES: cricopharngeal) relaxes--> bolus enters into esophagus --> sphincter contracts (tracheal entrance opens) --> esophageal (secondary) peristalsis --> lower esophageal sphincter (LES: gastroesophageal) relaxes --> bolus to stomach
The swallowing reflex is controlled by
- trigeminal (V)
- glossopharyngeal (IX)
- vagus (X)
Swallowing reflex pathways
- Afferent Pathway: stimulation of R's in the oropharynx --> sensory impulses to Medulla and Pons (swallowing center)
- Efferent Pathway: motor impulses via "V" and "IX" to pharynx and upper esophagus. Impulses via "X" to rest of esophagus --> relax lower oesophageal sphincter
- Respiration Inhibited - to prevent food entry into trachea
- refers to difficulty eating
- -abnormalities associated with prehension, mastication, and/or swallowing
- -many etiologies: oral pain, masses, foreign objects, trauma, or neuromuscular dysfunction
Functions of Vomition (emesis)
- Protection:-reverse peristaltic movements to rid of toxins before absorption from the GI tract--> ejected material is typically from the stomach or prox intestine
- -projectile vomiting (without retching)
- -true vomiting (with retching)
- -clinically three stages recognised in small animal patients: nausea, retching, vomiting****
- Expel indigestible material -birds (raptors) - "egestion" to rid of bones, fur, feather etc..
- -crocodiles (to rid hairballs etc...)
In which species does vomition occur?
Vomition occurs in carnivores and omnivores (except rodents)
What do rodents have?
- CTA: conditioned taste avoidance
- Pica: consume material without value
Do horses vomish?
Horses: rare- due to tonus of lower esophageal sphincter; inability to retch, may occur with acute gastric dilation, fatal event
Does vomiting occur in ruminants
- ruminants don't vomit
- they "regurgitate" abomasal contents into rumen and/or through mouth
What are the 3 phases of vomition?
- -nausea and hypersalivation
- -increased swallowing, relaxation of LES and proximal stomach
- Retching-retrograde giant duodenal contractions deliver contents to stomach
- -contraction of pylorus and relaxation of fundus
- -rhythmic retching. Inhibition of salivation. Mixing of gastric contents.
- -activation of expiratory intercostal muslces
- -elevation of larynx. increased UES tone. Protection of the nasal cavity
- -increased tone of cervical esophagus and pharynx
- Expulsion- decreased tone of cervical esophagus and pharynx
- -relaxation of diaphragm crura (where esoph goes in). decreased LES
- -contraction of abdominal muscles. Diaphragm squeezes stomach
- -inhibition of breathing. Closure of glottis
- 1) vomiting (emetic) center
- 2) neural pathways
- 3) humoral pathways
Vomiting (emetic) center
retrofacial nucleus (& NTS) in the medulla. It initiates and controls vomition - through neural and humoral pathways
What afferent neural pathways are involved in the vomiting reflex
- Afferent pathways:
- -Vagal afferents: afferent stimuli from GI tract, viscera, peritoneum
- --sympathetic afferents: from urinary and reproductive tracts
- -glossopharyngeal afferents: from pharynx
- -higher brain centers: direct stimulation (inflammation, hydrocephalus, tumors), )
- -chemoR trigger zone (CTZ)
What efferent neural pathways are involved in the vomiting reflex
- -vagal efferents: ENS coordinates GI motility and secretion
- -sympathetic and spinal nerves: diaphragm and abdominal muscles
- -cranial nerves: V, VII, IX, XII: prodromal signs
Humoral pathways in the vomiting reflex
- CTZ (chemoR trigger zone)
- -located on the floor of the 4th ventricle
- -receives afferent input from vestibular system, blood (drugs, infectious agents, metabolic diseases, osmolality, acid/base disturbances) and CSF
- passive retrograde movement of digesta to the level proximal to the upper esophageal sphincter. Characterized by:
- 1) increased intragastric P due to abdominal muscle contractions
- 2) intragastric P > LES P
- 3) reverse peristalsis
Is nausea with associated with passive or active throwing up?
passive and there is no nausea
In small animal species regurgitation is most often associated with...***
In terms of vomiting what do primary or secondary GI diseases refer to?
- Primary GI disease: disease within the GI tract
- Secondary GI disease: systemic disease (*stimulation of the chemoR trigger zone)
*Vomiting Vs Regurgitation**
- Vomiting:active process
- NAUSEA (may include salivation, licking lips, pacing, anxious expression)
- GI material from the stomach of proximal sm intestine
- indicative of GI (bellow the esophagus) or extra intestinal disease
- NO esophageal distention
- Regurgitationpassive process
- not associated with nausea (spontaneous)
- GI material from the esophagus (rarely stomach)
- indicative of swallowing or esophageal problems
- +/- distention of the cervical esophagus (mega esophagus)
etiologies of vomiting in Sm Animal patients
- motion sickness
- ingestion of emetogenic substances
- GIT obstruction
- extraintestinal tract diseases that may stimulate the chemoR trigger zone
- depend on severity, chronicity, underlying etiology
- dehydration, electrolyte abnormalities, weight loss can all occur
What can be used to ID esophageal abnormalities
- -normal esophagus is not visualized radiographically
- -a dilated (weak) or obstructed esophagus can commonly be seen
What are the most significant complications of regurgitation?
- aspiration pneumonia, dehydration and electrolyte imbalances
- if is persistent most patients will suffer weight loss
- *often polyphagic
- aspiration pneumonia is a common complication in sm animal patients
- the esophagus lies dorsal to the trachea
- sphincters at both ends: upper esophageal sphincter, lower esophageal sphincter
***** What is the histological differences of the canine and feline esophagus?
- canine esophagus is entirely skeletal muscle
- feline: distal third is skeletal muscle***
what causes peristalsis?
- peristalsis results from the contraction of circular muscle --> which pushes ingested food bolus toward the stomach
- longitudinal may also play a role
what is peristalsis in the striated muscle of the esophagus dependent on?
central mechanisms - involves sequential activation of vagal lower motor neurons in the vagal nucleus ambiguus
peristalsis in the SMOOTH muscle of the esophagus is dependent on
- BOTH central and peripheral mechanisms
- Central mechanism: involves patterned activation of the preganglionic neurons in the DMV of the vagus that project onto inhibitory and excitatory neurons in the myenteric plexus
- Peripheral mechanisms: involves regional differences in the inhibitory (releasing NO, VIP) and excitatory (release Ach, substance P) enteric nerves
peristaltic waves of contraction migrate from the.... to the.... muscles of the esophagus
striated to smooth muscle
how are striated muscles activated
activation of vagal efferents leads to sequential muscle contractions due to direct vagal efferent innervation (Ach) of the this muscle (motor end plates)
how is smooth muscle activated?
peristaltic wave is induced by myenteric neurons (excitatoru -Ach, inhibitory- VIP NO) which are activated by vagal efferents (centrally mediated dequencing is not necessary)
What contrast medium may be ingested in order to see abnormalities associated with the esophagus?
Regurgitation - in which species is it physiological?
- ruminants - to enhance fermentation of food
Regurgiation can occur due to obstruction as a result of ...?
- acquired (esophageal stricture)
- congenital (persistent right aortic arch)
Regurgitation can be due to what 3 things?
If a patient has a poor BCS, fever, abnormal lung sounds, bulging cervical area, fatigued palpebral reflex, mucoid expelled
- aspiration pneumonia* (key = the lungs)
what are some etiologies for acquired esophageal weakness?
- secondary to inflammation
- disorders of the neuromuscular jxn (effect skeletal muscle)
what is a common cause of acquired esophageal weakness due to neuromuscular junction disease?
- myasthenia gravis
- the weakness worsens with exercise, fatigueable palpebral reflex, diffuse esophageal weakness
What define mega esophagus?
- regurgitation caused by weakness
- congenital ***
If in your radiograph there is lots of air in the intestines and the stomach looks funny what may be a cause?
foreign body obstruction*
What are all the different types of primary GIT gastric obstructions?
- foreign body
- muscular abnormalities
- associated with the outflow tract of the stomach
For primary GI gastric diseases can result from?
- and infectious agents (worms)
- is a telescoping of the intestine upon itself that most commonly happens secondary to diarrhea
- this results in an obstruction
what in the small intestine can cause primary GI disease resulting in vomiting?
- obstruction: i.e. intussusception, tumor, abscess, foreign body
- or infectious* i.e. parvo, parasites, bacteria, fungal intestinal disease
what causes primary GI disease due to large intestinal disease resulting in vomiting?
- *uncommon to vomit with large intestinal disease
- severe inflammation can result in vomiting
Vomiting due to secondary GI disease may be caused by...
renal disease etc..
if a dog has an exophthalmic (bulging) eye with pain, pain opening mouth, palpate fluid pocket associated with the patients soft palate (abscess).... seee
Dysphagia is caused by what 3 things?
pain, neurologic, obstruction
what may be a neurological cause for dysphagia?
- rabies--> fatal zoonotic disease
- Other neurological causes of dysphagia: cranial nerve disease, myositis (inflammatory) of the masticatory muscles (primarily canine)
if a dog has bad breath, is thin, you cant elicite pain anywhere, no neurological signs, has increased submandibular and prescapular lymph nodes thennnnn you open their mouth and find....
- an oral squamous cell carcinoma
- = obstruction*
Do cats have physiological reasons for regurgitation?
what does feeding solid vs liquid barium mixture determine?
obstruction or not on a radiograph
what can you see on a radiograph in an acquired vs a congenital obstruction of the esophagus
- congenital: PRAA --> focal dilation
- acquired: diffuse distention
- persistent right aortic arch
- congenital malformation of the aorta
- embryonic right aortic arch develops rather than the left
- entrapment of the esophagus by: aorta on the right *ligamentum arteriosum dorsolaterally on the left and the heart base ventrally
- esophageal dilation cranial to heart base
what differentiates intraluminal stricture>
- stricture appears as distinct intraluminal fibrous rings that remain static
- vascular ring anomaly, rhythmic pulsations of the great arteries compressing the esophagus externally can be observed
what is dysphagia?
the inability to swallow
How does guttural pouch mycosis cause dysphagia?
secondary dysphagia due to CN damage --> pharyngeal paresis
What kind of complications may arise from dysphagia in horses?