Lecture 20 - Alimentary 1

Question 1

What is meant by the term dysphagia?

Answer 1

Difficulty or disorder eating

Question 2

State the following 1. What is the function of the gap reflex? 2. How is the gag reflex stimulated? 3. What are the afferent nerves and where do they go? 4. What is the efferent reaction? 4. What signals may be exhibited concurrently and why?

Answer 2

1. Normal defense mechanism preventing entrance entrance of foreign bodies into trachea, larynx or pharynx 2. Intraoral stimulation 3. Medulla - CN 5, 9, 10 4. Efferent causes brief elevation of soft palate together with contraction of pharyngeal restrictors 5. Medullary center - close to vasomotor and vomiting centers so these may be stimulated concurrently

Question 3

What are the four basic clinical signs that are associated with dysphagia?

Answer 3

1. Reduced or no food intake 2. Excessive salivation (pytalism) 3. Gagging 4. Halitosis

Question 4

Briefly describe the basic clinical approach to animal with dysphagia:

Answer 4

1. Can animal prehend - if not look at lips facial muscles etc. 2. Is the animal able to masticate - if not evaluate teeth, tongue, jaws etc. 3. Is the animal able to swallow - if not evaluate pharyngeal and esophageal function

Question 5

What are the motor and the sensory nerves that are involved in prehension?

Answer 5

CN 5, 7 and 12 - motor innervation to muscles of jaw, lips and tongue Sensory - CN 7, 9, 10 - taste, olfaction is CN 1, vision is CN 2, signals from rostral oral mucosa, lips and teeth -CN 5)

Question 6

What are the nerves that are involved in mastication?

Answer 6

Trigeminal nerve - CN 5 - sensory to oral mucosa and motor to jaw muscles

Facial nerve CN 7 - motor to facial muscles and sensory to rostral 2/3 of tongue

Glossopharyngeal - CN 9 - sensory to caudal 1/3 tongue

Hypoglossal nerve (CN XII) - motor to tongue

Question 7

Name the condition and cause of lesionshown below:

Answer 7

Uremic ulcers - caused by uremia

Question 8

Below is trauma to mouth of a cow. What is a possible cause?

Answer 8

Trauma - bones, wire, grass seeds, poor dentition

Question 9

Name the cause of the condition that is causing difficulty eating in the sheep below:

Answer 9

Poor dentition

Question 10

What is colloquial name for the condition shown below and what bacterial agent caused it?

Answer 10

Wooden tongue - Actinobacillus ligniersi

Question 11

What is the name of the condition shown in the calf below and what caused it?

Answer 11

Necrotic stomatitis/calf diphtheria - caused by fusobacterium necrophorum

Question 12

Name the condition that is shown below and provide three potential viral agents:

Answer 12

Erosive stomatitides - BVDV, Rinderpest, MCF

Question 13

Name the condition that is shown below and provide a potential aetiologic agent:

Answer 13

Vesicular stomatitis (Foot and mouth disease) - normally ulcerated by the time the vet gets to see it

Question 14

Name the fungal infection that is shoen in the glottis of the foal below:

Answer 14

Foal “thrush” - candida glossitis

Question 15

Name the fungal infection that has caused the condition seen in the foal below:

Answer 15

Fungal infection - conidiobolus (horse)

Question 16

What is the name of the neoplasm seen in the dogs tonsil below?

Answer 16

Lymphosarcoma

Question 17

What is the name of the condition that is seen in the horse below:

Answer 17

Fibrosarcoma

Question 18

What are the stages that are involved in deglutition?

Answer 18

1. The oral phase
2. The pharyngeal phase
3. The cricopharyngeal phase
4. Osephageal phase
5. Gastro-oesophageal phase

Question 19

What are the afferent pathways that are involved in degluttion?

Answer 19

1. Sensory nerve - posterior pharynx, base of tongue, epiglottis
2. Afferent pathway - trigeminal nerve (maxillary branch), glossopharyngeal nerve –> trachtus solitaris
3. CNS - nucleus solitarius and reticular formation –> swallowing centre (pons and medulla) –> cranial nerve nuclei

Question 20

What are the efferent pathways that are invovled in degluttion?

Answer 20

1. Trigeminal V - pharynx
2. Facial VII - oral voluntary muscles
3. Glosspharyngeal IX - pharynx
4. Vagus X - pharyngeal branch, recurrent laryngeal br, esophageal branch
5. Hypoglossal XII - tongue

Question 21

What is involved in the pharyngeal phase?

Answer 21

Pharynx is converted from an air channel to a food channel - the epiglottis covers glottis and the soft palate is elevated

Question 22

Provide and examples of pharyngeal dysfunction and state what clinical signs would be likely to be seen:

Answer 22

Pharyngeal paralysis - soft palate is permanently displaced over epiglottis. The clinical signs that are seen would be nasal discharge and aspiration pneumonia

Question 23

What is invovled in the cricopharyngeal phase? Provide an example of a pathological condition that can occur in this phase:

Answer 23

During swallowing vagal inhibition opens upper oesphageal sphincter allowing for the passage of the bolus into the oesphagus. After bolus has passed the sphincter closes preventing aspiration of the contents.

Failure of the oesophageal sphincter to open is referred to as “achlasia” - it is uncommon and generally breed related e.g. cocker spaniels

Question 24

What are the four main layers of oesphageal anatomy and describe the species difference?

Answer 24

wall has 4 main layers:

1. inner mucosa
2. submucosa
3. muscularis
4. outer connective tissue

Dogs and ruminants - muscularis is entirely striated

Horse, cat and pig - muscularis is striated at origin and changes to smooth muscle as oesphagus passes through thorax

Question 25

Briefly describe the nerve supply of the oesphagus:

Answer 25

Innervated by vagus: * Somatic to striated muscle * Autonomic to smooth muscle * Afferent nerves from sensory receptors Sympathetic nerves accompanying blood vessels also innervate oesphagus Oesphagus has submucosal and myenteric plexuses

Question 26

What are the steps that are involved in the oesphageal phase?

Answer 26

1. As the bolus enters the oesphagus - the primary peristaltic wave is generated at 2-6 cm/sec forcing bolus towards stomach 2. If the primary wave fades before bolus reaches the stomach - then a secondary peristaltic wave is generated by local oesphageal distention

Question 27

What are the stages invovled in the gastro-intestinal phase?

Answer 27

1. The gastro-oesphageal sphincter acts as a sphincter preventing reflux of contents 2. Normally, the region is tonically closed 3. Opens to allow the passage of the bolus or the erruction of gas

Question 28

What is the condition that is shown in the oesphagus below?

Answer 28

BVDV - Bovine Viral Diarrhoea Virus

Question 29

What is the condition that is shown below in the dogs oesphagus?

Answer 29

Dog - Lymphosarcoma

Question 30

Name the condition that is shown below and provide examples of some potential sequalae:

Answer 30

1. Condition is called choke - caused by ostruction of a food bolus 2. Pressure necrosis causing ulceration 3. Stricture developing

Question 31

Name the condition that is shown in the oesphagus of the dog below:

Answer 31

Foreign body with necrosis (dog)

Question 32

Name the condition that is shown below and briefly explain the physiology of it:

Answer 32

Persistant right aortic arch - connection between the aorta and the pulmonary artery that traps the oesphagus preventing food from going through it

Question 33

Name the condition that is shown below:

Answer 33

Megaoesphagus

Question 34

What is regurgitation and what conditions is it typically associated with?

Answer 34

Passive expulsion of fluid, undigested food, or other material from the pharynx or the oesphagus. Most commonly associated with oesphegal disease (e.g. hypomotility or obstruction) With regurgitation - NO nausea, no abdominal contraction, concious effort, or bile

Question 35

Define the term retching:

Answer 35

Forceful contractions of abdominal muscles and diaphragm against a closed glotti s - produces increased pressure in GIT - usually precedes vomiting

Question 36

What are the events that are associated with vomiting?

Answer 36

1. Prodromal events - hypersalivation, cardiac rythym changes, maybe defectation 2. Salivation stimulates swallowing 3. Antiperistalsis beginning in small intestine 4. Dudodenum is initially relaxed but then undergoes retrograde giant contraction moving contents into stomach 5. Immediately after RGC - duodenal activity 6. Retching ebgins shortly after the movement of contents into the stomach 7. Retrograde antral contractions and relaxation of the upper oesphageal sphincter 8. Vagally mediated contraction of oesphagus longitudinal muscle moves intra-abdominal oesphagus into throax facilitating entry of gastric contents 9. Gastric cotents are forcefiully expelled by contraction of abdominal muscle and the diaphragm 10. As vomitis passes up phaynx, glottis and nasopharynx region close --\> preventing aspiration and nasal regurgitation

Question 37

Where does the emetic centre receive input from?

Answer 37

peripheral visceral receptors, chemoreceptor trigger zone (CTZ) in 4th floor of ventricle, vestibular appartatus and cortical centres

Question 38

What are the ways in which the emetic centre can be activated?

Answer 38

1. Directly via GIT afferents acting on emetic centres (bacterial toxins, upper GI irritation/distention) 2. Indirectly via stimulation of the CTZ by blood borne chemicals (uraemia, endotoxins, apomorphine) 3. Indirectly via other pathways (cerebral cortex, brain stem and the vestibular apparatus)

Question 39

What are the main components of the "emetic centre"?

Answer 39

1. DMV = dorsal motor nucleus of vagus 2. NTS = nucleus tractus solitarus 3. RFN = retrofacial nucleus

Question 40

What are the consequences of continued vomiting?

Answer 40

1. Malnutrition 2. Hypovolaemia/dehydration 3. Hypochloraemia 4. Hypokalemia 5. Metabolic alkalosis