GI Physiology Flashcards
Prehension, mastication and deglutition
prehension?
the act of moving food into the mouth
what is prehension controlled by?
the CNS - primarily the facial nerve, the glossopharyngeal nerve and the motor branch of the trigeminal nerve
mastication?
chewing - the first act of digestion
chewing?
the breakdown of food particles to increase SA for digestion
saliva secretions?
moistens and lubricates food
type of epithelium in mouth lining?
stratified squamous epithelium
which neurones does the mouth contain?
terminal branches of sensory neurone - prepares stomach for type of food it is about to encounter
4 types of salivary glands?
zygomatic, parotid, sublingual and mandibular
describe mucous saliva?
thicker/more viscous
important for binding food into bolus
which glands secrete mucous saliva?
zygomatic and sublingual
describe serous saliva
watery and contains amylase (starches into simple sugars)
which glands secrete serous saliva?
parotid
mostly what type of saliva for birds?
mostly mucous type
dog species specific saliva?
no amylase
salivary gland control?
purely by neurones, no hormonal control
what are salivary glands regulated by?
by the parasympathetic nervous system
describe salivary gland control:
nerve fibres end on the acini
stimulation results in increased saliva production
salivary secretory cells also contain B-adrenergic receptors
What activates the B-adrenergic receptors?
the sympathetic nerve stimulation (fight or flight)
component of saliva that enables the lubrication function?
mucin (glycoproteins) - mix with water to form mucous
component of saliva that enables the pH regulation function?
HCO3-
neutralisation
component of saliva that enables the antibacterial function?
lysozymes and antibodies
keep the amount of bacteria in check
slide 11
what is the pH of the saliva in a ruminant?
alkaline (bicarbonate phosphate)
considering its pH, what is the importance of saliva in ruminants?
necessary for neutralisation of fermentation products
how many litres of saliva can an adult cow excrete?
100-200 litres of saliva a day
slide 12
6 steps of the involuntary phase of deglutition:
Breathing stops momentarily
Soft palate is elevated
The tongue is pressed against the hard palate
The glottis is pulled under the epiglottis
When all openings into the pharynx are closed a wave of muscualr contrxaction passes over the walls of the pharynx
the upper oesophageal sphincter releases
invoiluntary phase of deglutiion controlled by?
by motor neurones in vsrtious centres of the brainstem
drooling lotsd and panting and difficulty swallowing?
facial nerve is impacted - neurological
striated muscle AKA?
skeletal muscle
oesophageal muscle types?
striated and smooth muscle
skeletal muscle in dogs, cattle and sheep?
the entire length of the oesophagus is striated
skeletal muscle in horses primates and cats?
a portion of the oesophagus is smooth muscle
muscle control of striated muscle?
vagus nerve
muscle control for smooth muscle?
ENS (gut specific nervous system)
in many species, what is the action of the lower sphincter aided by?
by the anatomical attachment to the stomach
peristalsis?
exists in all levels of gut, movement of substances throughout the gut all the time, a moving ring of constriction pushing food through
consists of primary and secondary waves
longitudinal muscles contract
food moves forward
circular muscle contract - longitudinal relax?
food moves forward
when does the sympathetic nerve stimulation of the B-adrenergic receptors occur, why and what is produced?
this stimulation has little to do with digestive activity
occurs in carnivores about to attack
produces a smaller quantity of viscous saliva
saliva used for starch digestion in which species and how?
omnivores, single-stomached herbivore and some avian
USING amylase
saliva used for fat digestion in which species and how?
in young calves and USING lingual lipase
saliva used for thermoregulation in which species and how?
in canine and rodent USING panting and spreading saliva (over body - evaporative cooling)
saliva used for binding tannins in which species and how?
in leaf-eaters USING binding proteins
saliva used for providing urea in which species and how?
in animals with fore-stomachs
Urea diffuses from blood into saliva
problems in ruminants (cows) with being able to excrete lots of saliva in one day?
H2O and electrolyres secreted in saliva must be reabsorbed rapidly
cow could become dehydrated
in abnormal circumstances cows become acidotic
two phases of deglutition?
voluntary and involuntary
voluntary stage of deglutition:
chewed food is moulded into a bolus and moved to the pharynx
involuntary stage of deglutition:
initiated by the voluntary
describe the control of deglutition:
efferent nerve fibres travel in the facial, vagus and hypoglossal and glossopharyngeal nerves
clinically, what do problems with prehension, mastication and deglutition frequenctly relate to?
relate from neurological lesions
e.g. laryngeal paralysis - panting and swallowing issues
what does wall of oesophagus consist of?
mucosa, submucosa
muscularis and serosa
what does muscularis layer consist of?
circular
longitudinal
what does mucosa layer consist of?
epithelium
lamina propria
muscularis mucosae
what is happening when deglutition is not taking place?
the body of the oesophagus is relaxed but both sphincters are tightly constricted
what two waves are there in peristalsis?
primary (stronger) and secondary (weaker) waves
