Stomach anatomy and motility Flashcards
(90 cards)
Describe the path taken by the cervical oesophagus
- upper aspect is on the midline
- Passes to left as approaches thoracic inlet
Describe the thoracic oesophagus
- Begins at thoracic inlet
- Covered by serosa
- Passes through inlet on left
- Moves back to previous position dorsal to trachea
- Runs in mediastinum
Describe the abdominal oesophagus
- following passage through oesophageal hiatus of diaphragm
- very short
- terminates at cardiac of stomach
List the related structures at the cervical portion of the oesophagus
- Common carotid artery
- Internal jugular vein
- Tracheal duct
- Cervical lymph nodes
- Vagosympathetic trunk
- Recurrent laryngeal nerve
What happens to the thickness of the wall of the oesphagus going from cranial to caudal?
- The wall thickens
What are the layers of the oesophageal wall?
- Connective tissue adventitia (outer layer)
- Muscular layer
- Mucuous membrane (stratified squamous epithelium, tight junctions)
Describe the muscular coats of the oesophagus
- Striateed intially in all species
- In cat, pig, horse becomes smooth distally
- get circular and longitudinal muscle neaer to stomach
Describe the tunica mucosa of the oesophagus
- Stratified squamous epi
- cornified in herbivores
- lamina propria without glands
- Lamina muscularis incomplete, most extensive in caudal aspect
- Submucosa well developed
- loosely binds mucosa and muscularis layers
What is different in the tunica mucosa of the oesophagus in dogs, pigs, cats and horses?
- Dogs: mucous glands over entire length
- Pig: glands only cranially
- Cat and horse: glands only at pharyngo-oesophageal junction
Describe the tunica muscularis of the oesophagus
- Inner and outer layers
- Continuous cranilly with pharyngeal muscles
- Mid-region, muscle layers arranged in intercrossing spirals
- Caudally the outer fibres more longitudinal, inner circular and thicker
What are the 3 phases of swallowing?
- Oropharyngeal
- Oesopharyngeal
- Gastro-oesophageal
Outline the process of swallowing
- food to base of tongue
- Pharyngeal muscles contract to push food to laryngopharynx
- after contraction of pharyngeal muscles, cricopharyngeal and thyropharyngeal muscles relax
- Opens oesophagus - bolus can pass
- After bolus passage, muscles contract once more (duration of relaxation determined by sensory input from pharyngeal filling)
- High sphincter pressure prevents aspiration or reflux of oesophageal contents
- Peristaltic wave continues along oesophagus carrying bolus to lower oesophageal sphincter
- if bolus not carried to stomach, secondary wave from local stimulation and carries bolus along
What is the difference in control of pharyngeal and oesophageal phases of swallowing?
- pharyngeal controlled by central pattern generator- no peripheral feedback
- Oesophagus works by peripheral feedback
Explain why conditions can affect pharyngeal or oesophageal phases of swallowing independently?
2 distinct pattern generators for the 2 regions
What is the blood supply to the cervical region of the oesophagus?
- Thyroid and subcalvian arteries
- Branches from left and right common carotids
What is the blood supply to the thoracic region of the oesophagus?
Broncho-oesophageal artery
What is the blood supply to the abdominal region of the oesophagus?
Left gastric and splenic arteries
What is the venous drainage of the cervical portion of the oesophagus?
External jugular veins
What is the venous drainage of the thoracic portion of the oesophagus?
- Oesophageal vein
- In dogs and cats, pair of oesophageal veins drain into azygous via bronchooesophageal veins
- In horse, oesophageal vein drains directly into azygous vein
Describe the lymphatics of the oesophagus
- Cranial aspect into cervical, middle and caudal deep cervical nodes
- Thoracic lymph from oesophagus drains into cranial and caudal mediastinal lymph nodes
where does the sympathetic innervation of the oesophagus come from?
From cervico-thoracic ganglion
where does the parasympathetic innervation of the oesophagus come from?
Branches of the vagus nerve
Where are the ganglia supplying the oesophagus found?
Between the internal and external muscle layers
Describe the physiological characteristics of teh GI tract smooth muscle
- Unitary (syncitial)
- Mass of many fibres, contract as single unit
- Arranged in sheets or bundles
- Cells in contact, joined by gap junctions = free movement of ions between each muscle cell
- Nerves innervating smooth mm branch over many fibres
- Nerves do not make direct contact, diffuse junctions = transmitter secreted into local environment of muscle
- Contraction and relaxation due to transmission of ACh and noradrenaline
- Stretch of lumen = contraction of muscles (peristalsis)
- Local tissue factors and hormones also influence activity
- Some areas have spontaneous activity