Anatomy: how do we taste, chew, swallow? Flashcards
Where is the GI tract?
It runs from the mouth to the anus. It has structures in the head, neck, chest, abdomen, pelvis and perineum
Where is the separation between the upper and lower GI tract?
The small intestine is the upper GI tract and the large intestine marks the start of the lower GI tract
What is an endoscope used for?
To view inside of the the GI tract
At what joints does jaw opening occur?
At the temporal mandibular joints
What are the 3 pairs of jaw closing muscles?
Masseter
Temporalis
Medial pterygoid
What pair of muscles are for jaw opening?
Lateral pterygoid
What nerves supply the muscles for jaw opening and closing?
Mandibular division of the trigeminal nerve (CN V3)
What does the ‘course
of a nerve describe?
The journey it takes between the CNS and the peripheral structure it supplies
What is the course of CN V3?
Enters/exits the CNS at the pons
Intracranial part of the course
Passes through the foramen ovale and the extracranial part of the course begins
List the surface anatomy of the oral cavity
Upper and lower dental arch Hard palate Soft palate Arches of the soft palate Uvula of soft palate Tongue Palatine tonsil Gingivae
When question should you ask when doing an oral examination?
Have you recently had any dental work?
What is the posterior tongue?
1/3 of the tongue
The back, vertical part
A part that we cannot see
It is not in the oral cavity
What is the anterior tongue?
2/3 of the tongue
Horizontal part
In the oral cavity
What is the function and nerve supply of the posterior tongue?
All sensation
General and taste
supplied by CN IX
What is the function and nerve supply of the anterior tongue?
General sensation supplied by CN V3
Special ‘taste’ sensation supplied by CN VII
What nerve allows general sensation in the superior half of the mouth (gingiva and palate)?
CN V2
What nerve allows general sensation in the inferior half of the mouth (gingiva and floor of mouth)?
CN V3
What is the gag reflex?
It is a protective reflex that prevents foreign bodies tom entering he pharynx or the larynx
Which nerve fibres carry the sensory part of the gag reflex?
CN IX
glossopharyngeal
Which nerve fibres carry the motor part of the gag reflex?
CN IX and CN X
What happens to your pharynx if you touch the posterior wall of your oropharynx?
Pharynx constricts - attempt to close it off as an entry to the body
What does CN V2 supply?
General sensation in the superior half of the oral cavity
What does CN V3 supply?
Muscles for jaw opening and closing
Sensation in the anterior tongue
General sensation in the inferior half of the oral cavity
What does CN VII supply?
Taste in the anterior tongue
What does CN IX supply?
Sensory and motor gag reflex
General and taste sensation in the posterior tongue
What does CN X supply?
Motor gag reflex
Before doing an endoscopy an anaesthetic spray is used. What nerves does this block the sensory action potentials of?
CN V2, CN V3, CN VII, CN IX
What is the course of CN V2?
Enters/exits the CNS at the pons
Intracranial part of the course
Goes through the foramen rotundum
Extracranial part of the course
What is the course of CN VII?
Enters and exits the CNS at junction of pons and medulla
Passes through 2 foramen: internal acoustic meatus (IAM) and stylomastoid foramen (SMF)
What is chorda tympani?
Branch of CN VII
Special sensory ‘taste’ to anterior 2/3rds of tongue
Parasympathetic secretomotor to submandibular and sublingual salivary glands
What is the course of CN IX?
Enters/exitsi the CNS at the medulla
Enters/exits the cranial cavity at the jugular foramen
What salivary glands does CN IX have parasympathetic secretomotor supply to?
Parotid salivary glands
What are the 3 pairs of salivary glands?
Parotid, submandibular and sublingual
What should you ask the patient to do when you insert the endoscope?
Swallow
What is the function of the 4 pairs of extrinsic skeletal tongue muscles/
Originate external to the tongue
Suspend the tongue in the oral cavity
Move the tongue around within the oral cavity during mastication, swallowing and speech
What are the names of the 4 muscles extrinsic skeletal tongue muscles?
Palatoglossus
Styloglossus
Hyoglossus
Genioglossus
What is the function of the 4 pairs of intrinsic skeletal muscles?
Originate within the tongue
(Located mainly dorsally and posteriorly)
Modify the shape of the tongue during function
What is the nerve that supplies all the tongue muscles, apart from palatoglossus?
CN XII (hypoglossal)
What is the course of the hypoglossal nerve?
Enters/exits the CNS at the medulla
Enters/exits the cranial cavity at the hypoglossal canal
What is the structure of the muscles of the pharynx?
Inner longitudinal layer of muscles
Outer circular layer of pharyngeal constrictor muscles (superior, middle and inferior)
What is the function of the inner longitudinal layer of muscles?
Attach to the larynx
Contract during swallowing to shorten the pharynx
Raise the larynx, close the laryngeal inlet
What are the main nerves that supply the inner longitudinal layer of muscles?
CN IX and X
What is the function of the outer circular layer of pharyngeal constrictor muscles?
Sequentially contract to push the food bolus inferiorly into the oesophagus
What nerve supplies the outer circular layer of pharyngeal constrictor muscles?
CN X
What muscle and nerve and involved in closing the mouth for swallowing?
Orbicularis oris and CN VII
After the mouth has closed, what are the steps in swallowing?
Tongue pushes the bolus posterioly towards the oropharynx
Pharyngeal constrictor muscles sequentially contract to push the food inferiorly towards the oesophagus and the inner longitudinal layer of pharyngeal muscles contracts to raise the larynx, shorten the pharynx and close the laryngeal inlet to help present aspiration
Bolus reaches the oesophagus
What is the structure and location of the upper oesophageal sphincter?
Complete circle of muscle
Junction of pharynx and oesophagus
Vertebral level C6
When is constricts it completely blocks the oesophagus
What is the order of nerve involvement in swallowing/
CN VII (facial) CN XII (accessory) CN X and CN IX (vagus and glossopharyngeal)
What is the enteric nervous system?
Extensive network or nerves only found in the walls of the GI tract
Acts independently of other parts of the nervous system (can be influenced by autonomic nerves)
What do the parasympathetic and sympathetic branches do?
Parasympathetic speeds up peristalsis
Sympathetic slows down peristalsis
How many constrictions does the oesophagus have?
3
What test can be done to examine oesophageal constriction?
Barium swallow study
What is the oesophagus a continuation of?
Laryngopharynx
Where does the oesophagus begin?
Interior edge or cricopharyngeus muscle (vertebral level C6)
What is the structure of the oesophagus?
Muscular tube - walls site together when there is no food present
Which sphincter is anatomical and which is physiological?
Upper (cricopharyngeus) is anatomical and lower is physiological
Where does the oesophageal plexus run?
Surface of the oesophagus to supply smooth muscle within its walls
Where does the oesophagus terminate/
Terminates by entering the cardia of the stomach
Where are the three oesophageal constrictions?
Cervical constriction (cricopharyngeus muscle) Thoracic constriction (arch of the aorta and left main bronchus) Diaphragmatic constriction (result of passing through the diaphragm, lower oesophageal sphincter)
What factors produce the effect of the lower sphincter?
Contraction of the diaphragm
Intrabdominal pressure is slightly higher than intragastric pressure
Oblique angle at which oesophagus enters the cardia of the stomach
What will reduce the effectiveness of the lower oesophageal sphincter?
Presence of a hiatus hernia - can lead to symptoms of reflux
Why does the oesophagus enter the cardia of the stomach at an angle?
To try and prevent reflux
What is the Z line?
There is an abrupt change in the type of mucosa lining the wall on either side of the lower oesophageal sphincter
Allows doctors doing an endoscopy to see when they have entered the stomach
When the patient is supine, where does the stomach mainly lie?
Left hypochodrium, epigastric and umbilical regions
What are the names for the folds in the stomach?
Rugae
What is the incisura angularis?
The angle where the body of the stomach becomes the antrum
What is the bed of the stomach?
All of the structures that the stomach lies on:
spleen, kidney, adrenal gland, pancreas, transverse colon and left hemi-diaphragm