Anatomy of Upper GI tract Flashcards
What is mastication?
Process of chewing
How is mastication conducted?
Movement of jaw and tongue to breakdown food
What does mastication facilitate?
Taste and digestion by mixing food with saliva
How many teeth do adults have?
32
Describe the teeth types?
2 Incisors 1 canine 2 premolars 3 Molars
Describe the features of the TMJ?
Mandibular fodda Head of condylar process
What supplies the four muscles of mastication?
Mandibular division of trigeminal nerve- CN V3
What is the role of the 4 muscles of mastication?
3 close 1 open
Describe the temporalis m?
Coronioid process of mandible to temporal fossa (close)
Describe the master m?
Angle of mandible to zygomatic arch (close)
Describe the medial pterygoid?
Angle of mandible (medial side) to pterygoid plates of sphenoid bone (close)
Describe the lateral pterygoid?
Condyle of mandible to pterygoid plates of sphenoid bone (open)
What is the superior cavity of the TMJ for?
Translation
What is the inferior cavity of the TMJ for?
Rotation
Describe the course of the CN V3
From pons through foramen ovale to muscles of mastication and sensory area
Label this diagram
Lable this diagram
What do loose teeth pose?
Choking hazard
Aspiration risk
Infection risk
What are two divisions of the tongue?
Posterior 1/3rd
Anterior 2/3rd
Describe the posterior 1/3rd of the tongue?
Vertical
In oropharynx
What is the posterior 1/3rd of the tongue responsible for?
Taste and general sensation (CNIX)
What is the anterior 2/3rds of the tongue responsible for?
Taste CNVII
General sensory CNV3
Describe the anterior 2/3rds of the tongue?
Horizontal part
In oral cavity
Folliate papillae, valiate (in V shape) and fungiform papillae
Filiform papillae
What is the role of Filiform papillae?
Touch, temperature
Describe the functions of the facial nerve
Special sensory, sensory, motor and parasympathetic
Describe the course of the facial nerve?
From pontomedullary junction
Through temporal bone via internal acoustic meatus then stylomastoid foramen
What does the facial nerve supply?
Taste to anterior 2/3rds of the tongue
Muscles of facial expression
Glands in floor of mouth
What is the chorda typami?
CN VII Connects to the lingual nerve CNV3
Descibr the course of the facial nerve?
Intracranial
arises in the pons
- begins as two roots; a large motor root, and a small sensory root (the part of the facial nerve that arises from the sensory root is sometimes known as the intermediate nerve).
- The two roots travel through the internal acoustic meatus, a 1cm long opening in the petrous part of the temporal bone, in very close proximity to the inner ear.
- Still within the temporal bone, roots leave internal acoustic meatus, enter into the facial canal (‘Z’ shaped structure)
- Within the facial canal, three important events occur:
- two roots fuse to form the facial nerve
- nerve forms the geniculate ganglion (a ganglion is a collection of nerve cell bodies).
- nerve gives rise to:
- Greater petrosal nerve – parasympathetic fibres to mucous glands and lacrimal gland.
- Nerve to stapedius – motor fibres to stapedius muscle of the middle ear.
- Chorda tympani – special sensory fibres to the anterior 2/3 tongue and parasympathetic fibres to the submandibular and sublingual glands.
then exits the facial canal (and the cranium) via the stylomastoid foramen. (just posterior to the styloid process of the temporal bone)
Extracranial
the facial nerve turns superiorly to run just anterior to the outer ear
- first extracranial branch to arise is: posterior auricular nerve.
- provides motor innervation to the some of the muscles around the ear.
- Immediately distal to this, motor branches are sent to the posterior belly of the digastric muscle and to the stylohyoid muscle.
- The main trunk of the nerve, now termed the motor root of the facial nerve, continues anteriorly and inferiorly into the parotid gland (note – the facial nerve does not contribute towards the innervation of the parotid gland, which is innervated by the glossopharyngeal nerve).
- Within the parotid gland, the nerve terminates by splitting into five branches:
- Temporal branch
- Zygomatic branch
- Buccal branch
- Marginal mandibular branch
- Cervical branch
- These branches are responsible for innervating the muscles of facial expression.
What does the superior half of oral cavity revienve sensation from?
CN V2
What does the inferioe half of oral cavity revienve sensation from?
CN V3
What is the role of the gag reflex?
protective reflex that prevents foreign bodies from entering the pharynx or larynx
Describe the sensory and motor innervation of the gag reflex?
Sensory limb is carreid by nerve fibres within the CN IX
Motor part is carried by nerve fibres within CN IX and CN X
Describe the course of CN V2?
From pons
Through foramen rotundum
To sensory area
Maxillary division of trigeminal nerve
Describe the function and course of CN IX?
Special sensory, sensory, motor, visceral afferent and parasympathetic
Course
From medulla
Through jugular foramen
To posterior wall of oropharynx (sensory), parotid gland (secretomotor) and posterior 1/3rd of tongue (sensation and taste)
Describt the anatomy of the parotid gland?
Parotid duct crosses face secretes into mouth by upper 2nd molar
Describe the anatomy of the submandibular gland?
Submandibular duct enters floor of mouth and secretes via lingual caruncle
Describe the anatomy of the sublingual gland?
Lays in floor of mouth secretes via several ducts superiorly
How is the tongue suspended in the oral cavity?
By 4 pairs of skeletal muscle
What is the function of extrinsic muscles of the tongue?
Function to change the position of the tongue during mastication, swallowing and speech
What is the function and location of the 4 pairs of intrinsic skeletal muscles?
Located mainly dorsally/posteriorly
Modify the shape of the tongue during function
Describe the innervation of tongue muscles?
INNERVATED BY CNXII (Hypoglossal nerve), EXCEPT PALATOGLOSSUS!
Name the four muscle of the tongue?
Palatoglossus
Styloglossus
Genioglossus
Hyoglossus
Describe the function and course of CN XII?
Motor only
Course
From medulla
Through hypoglossal canal
To extrinsic and intrinsic msucle of tongue (except palatoglossus)
What is the cricopharyngeus?
C6- junction between pharynx and oesophagus
What kind of muscle is found in the pharynx?
outer
- Circular (constrictor) muscles
- Voluntary muscle
- Voluntary but cannot control sequence
inner
- Longitudinal muscles
Describe the structure of outer pharynx musculature?
The external (circular) layer overlap each other and contract sequentially
All insert onto midline raphe
Buccopharyngeal fascia covers muscles
What innervates the muscles of the pharynx?
Outer
CN X
Inner
Supplied mainly by CN X and IX (one muscle)
What are the functions of the pharyngeal muscles?
- Both layers elevate pharynx & larynx
- Attach to larynx
- Contract to shorten pharynx
- Raise the larynx to close over the laryngeal inlet
What would you do when inserting an endoscope?
- ask patient to swallow as you insert
Describe the four steps of swallowing?
- Voluntary- tongue pushes bolus of food towards oropharynx
- Involuntary- soft palate elevated, larynx elevated
- Inovluntary- circular layer of pharyngeal constrictor muscle contracts
- Involuntary- bolus of food enters oesphagus and travels inferiorly by peristalsis
Describe the anatomy of swallowing?
- Close lips = prevent drooling (orbicularis oris & cranial nerve VII)
- tongue (cranial nerve XII) pushes the bolus posteriorly towards the oropharynx
- Sequentially contract the pharyngeal constrictor muscles (cranial nerve X) to push the bolus inferiorly towards the oesophagus
- At the same time the inner longitudinal layer of pharyngeal muscles (cranial nerves IX & X) contracts to raise the larynx, shortening the pharynx and closing off the laryngeal inlet to help prevent aspiration
- The bolus reaches the oesophagus
What is the oesophagus?
Inferior continuation of laryngopharynx
When does the oesophagus begin?
Inferior edge of cricopharyngeus muscle (verterbral level C6)
What is the status of the oesophagus when no food is present?
Muscular tube- walls sit together
Describe the sphincters of the oesophagus?
- anatomical upper sphincter (cricopharyngeus) and a physiological lower oesophageal sphincter
- Aid in controlling food movement
What is the oesophageal plexus?
- plexus runs on surface to supply smooth muscle within its walls (distally)
- Contains parasympathetic nerve fibres (vagal trunks) and sympathetic nerve fibres
- These fibres influence the enteric nervous system to speed up (P) or slow down(S) peristalsis
When does the oesophagus terminate?
By entering the cardia of the stomach
Where is the oesophagus found in the:
- root of neck
- chest
- abdomen
- Posterior to trachea
Anterior to vertebral bodies
- Posterior to heart
In contact with left atrium
- Through diaphragm
Immediately connects with stomach
What are the constrictions of the oesphagus in the;
- cervival region
- thoracic region
- diaphragmatic region
- cricopharyngeus muscle
- arch of aorta, left main bronchus
- result of passing through diaphragm, lower oesophageal sphincter
What factors produce effect of LOS?
- Contraction of diaphragm
- Intrabdominal pressure slightly higher than intragastric pressure
- Oblique angle at which oesophagus enters the cardia of stomach
What does the LOS do?
reduce occurrence of ‘reflux’
What will a hiatus hernia cause?
•reduce effectiveness of LOS
Can lead to symptoms of reflux
Where is the LOS?
- Lies immediately superior to gastro-oesophageal junction
- Abrupt change in type of mucosa lining the wall - Z-line
Where is the stomach?
mainly in the left hypochodrium, epigastric and umbilical regions when the patient is supine
Label this structure
