Physiology overview and swallowing Flashcards
What are the sympathetic nerve roots going to the spinal cord? (what levels)
T5- L3
Describe the path of the sympathetic nerves to the GI tract
They exit at T5-L3, pass through the sympathetic trunk without synapsing, then combine to form 3 presynaptic splanchnic nerves. These synapse at 3 ganglia before splitting again to go to their effector tissues
What are the nerve roots of the greater, lesser and least splanchnic nerves?
- greater= T5-9
- lesser= T10-11
- least= T12
What are the names of the ganglia formed by the 3 splanchnic nerves?
greater–> coeliac ganglia
lesser–> Superior mesenteric ganglia
least–> inferior mesenteric ganglia
Which nerves provide parasympathetic stimulation to the upper GI (stomach upwards) and lower GI tracts (stomach downwards)
Upper GI = vagus nerve
Lower GI= pelvic splanchnic nerve
What are the nerve roots of the pelvic splanchnic nerve?
S2-4
What neurotransmitters do parasympathetic post ganglionic fibres release in the GI system?
Ach
gastrin releasing peptides
Where are the main plexuses of the enteric nervous system and what are their names?
- In the submucosa= meisssners plexus
- Between the circular and longitudinal muscle= auerbach’s/ myenteric plexus
Describe the relationship between the autonomic nervous system and the enteric nervous system?
The ANS communicates w/ it an influences it but the enteric NS can function independantly of it.
What do the myenteric and submucosal enteric NS plexuses control?
Myenteric controls motility
Submucosal controls secretions and blood flow
Give two hormones in the gastrin family, state their funcitons
Gastrin- increases HCl secretion in the stomach
CCK- increases pancreatic and bile secretions
Give two hormones in the secretin family, state their functions
Secretin - increases HCO3- release from the pancrease and gall bladder
Gastrin inhibitory peptide- increases insulin, decreases gastric acid secretion
Why is visceral pain reffered in GI injury?
Because the viscera is under sympathetic innervation so is poorly localised, it is reffered to the nerve root which innervated that segment (If greater T5-9, if lesser T10, if least T12)
What are the three types of movement seen in the GI and where?
- peristalsis in oesphagus
- segmentation in the stomach and intestines
- mass movement in the distal colon to propell contents into the rectum
Describe segmentation and its function
Non adjacent segments of the ailmentary canal relax and contract, this moves food backwards and then forwards, mixing food and mechanically breaking it down.
How much fluid per day is secreted into the GI tract and from where?
9L- 2L ingested, 1.5L in saliva, 2.5L of gastric secretions, 1.5L of secretions from pancreas
Whats the difference between the brunners glands and crypts of leiberkun?
Brunners= duodeunum only and compound tubular
Crypts of leiberkun= throughout all intestine and simple tubular
What are the three salivary glands called
Parotid
Sub mandibular
Sub ligual
Which salivary gland is C shaped around a muscle?
Submandibular
Where do the submandibular gland’s ducts open to in relation to the sublingual glands ducts?
Submandibular ducts open medial and anterior to the multiple ducts of the sublingual glands
Which nerves supply the salivary glands?
Subligual and submandubular= lignual branch of the facial nerve
Parotid gland supplied by the glossopharyngeal nerve
Describe the hormonal and nervous control of saliva production
No hormonal control.
Parasympathetic increases saliva production, sympathetic stimulation also causes release of a small quantity of very viscous saliva- it causes vasoconstriction so little dilution of saliva.
Describe production and modification of saliva
Acinar cells secrete the basic, isotoninc solution.
Ductal cells modifiy the solution as it is released, by removing Na+ and Cl- and adding H+, HCO3- and K+.The reduction of ions is greater than gain in ions making thr solution hypotonic.
What affect does slow saliva flow rate have on saliva compositon?
slow flow rate= greatest modification= more hypotonic
What ion is secreted into saliva by ductal cells at a greater rate when flow is faster?
bicarbonate
Describe the structure of salivary glands
Compound acinar
Are secretions from all 3 salivary glands the same?
No, parotid is more serous, sublingual is mucous and submandibular is mixed
What does saliva contain? (7)
Mostly water, HCO3- (basic), K+, mucins, amylases, lingual lipases, immune proteins (IgA, lysozymes)
What is the function of saliva? (5)
Lubricate mouth (important for speaking and swallowing), oral hygene, start digestion, solvent for food molecules to stimulate taste buds, destroy microorgansism
What is xerostomia? What does it present with?
A dry mouth. It presents w/
- Dysphagia
- DIfficulty chewing
- Mouth ulcers
- Oral thrush
- Wrinkled/ cracked tongue
What can cause xerostomia?
- Dehydration
- Anti- muscarinic drugs
- Ageing
- Alcohol
- Diabetes
- Cancer treatments
- Many other causes
How can you differentiate between salivary gland swelling due to mumps and due to stones?
Inject contrast into the ducts and Xray (contrast sialography) to see if a stone is blocking the duct or if the swelling is due to mumps. Also stones pain tends to be made worse by chewing as saliva is produced.
Why are mumps and salivary stones so painful?
Because the salivary gland has a thick fibrous capusle which doesnt expand easily
What causes mumps?
Infection by paramyxovirus
What are the 3 phases of swallowing?
oral preparatory phase
Pharyngeal phase
Oesphageal phase
Describe the oral preparatory phase of swallowing
It is a voluntary phase in which the bolus is pushed back towards the pharygneal wall, which is sensed by the glossopharyngeal nerve and triggers the pharyngeal phase.
Describe the pharyngeal phase of swallowing
- Involuntary
- Soft palate seals off nasopharyngx
- Pharyngeal constrictor muscles push bolus backwards
- Larynx elevates- closing the epiglottis
- Vocal cords adduct (so breathing stops temporarily)
- Upper oesphageal sphincter opens
Describe the oesophageal phase of swallowing
- also involuntary
- Closure of upper oesphageal sphincter
- Peristaltic wave carries bolus down into oesphagus and into the stomach
Why can a baby swallow and breath at the same time?
Because their epiglottis projects higher up into the nasopharynx, this however means they cant speak. As the baby grows and neck elongates the epiglottis descends into place.
Briefly outline the neural control of the gag/ swallow reflex
Mechanoreceptors detect the bolus, and afferent impulse is in the glossopharyngeal nerve. The info is processed in the medulla, where the vagus nerve is stimulated (efferent), and this stimulates the pharyngeal constrictors
What can be inferred about dysphagia of solid food vs dysphagia of liquids?
If dysphagia of liquids- problems coordinating swallowing movements
If dysphagia of solids- physical obstruction
Where are the 4 natural places of oesphageal narrowing?
- junction w/ pharynx
- Where aortic arch pushes on it
- Where left main bronchus pushes on it
- T10 where pierces diaphragm
What natural mechanisms are there to prevent reflux? (5)
- Sphincter of ring of smooth muscle at base of oesphagus
- Diaphragm pinching oesphagus at junction w/ stomach
- Part of oesphagus in abdomen, so is compressed when intra abdominal pressure rises
- Muscles rosette at cardia
- Acute angle of entry of oesphagus
List one cause of liquid and one cause of solid bolus dysphagia
Liquid: Strokes affeccting medulla, CN IX and X legions
Bolus: cancer, large goitre, retropharyngeal abcess, infection, thrush, anything decreasing saliva production
How is dysphagia after stroke treated?
IV fluids and swallowing rehabillitation
