Anatomy - general Flashcards
Where is the midpupillary line (MPL)?What landmarks does it locate?What structures do these carry?
The MPL is 2.5cm lateral to the midline
Supraorbital foramen
Infraorbital foramen - 1cm below the inferior margin of the orbit
Mental foramen
each carry a nerve, artery and vein of the same name as the foramen they traverse
What structures are located by the anterior border of the masseter (ABM)?
Stenson’s (parotid) duct
Facial artery
Marginal mandibular nerve
How is Stenson’s duct located?
It pierces the buccinator at the ABM at the point where the ABM is intersected by the tragolabial line
The ABM is in line with the lateral canthus
Where does the tragolabial line run?
Tragolabial line runs from the upper lip vermilion in the midline to the middle of the tragus
What is the course of the facial artery and vein?
Comes onto the face at the lower boarder of the ramus of the jaw just anterior to the ABM
Travels supero-medially passing the commissure of the mouth
Becomes the angular artery which continues and terminates at the medial canthus
Facial vein runs just lateral to the artery
Which muscle traverses the ABM
zygomaticus major
a muscle of facial expression
What is the course of the marginal mandibular nerve?where is it most vulnerable?what muscles does it innervate?
Exits the parotid at the angle of the mandible and runs over the superficial surface of the masseter along the undrside of the jaw
Comes over jaw onto face just posterior to the facial artery; NBA nerve behind artery
Most vulnerable here as it comes over the jaw
Innervates lip depressors - depressor labii inferioris and depressor anguli oris, platysma, mentalis
What is the approximate course of the temporal branch of the facial nerve?What muscle(s) does it innervate?Where is it most at risk?What are the boundaries of the Danger Zone for this nerve?
Temporal nerve approximated by a line from 0.5cm below the tragus to 1.5cm above the lateral eyebrow
Supplies frontalis, upper portion of orbicularis oculi and corrugaor supercillii and procerus (usually)
also some auricular muscles
Most at risk as it crosses the zygomatic arch (as it is most superficial)
Danger zone is between a line from the upper tragus to the top forehead wrinkle and from 0.5cm below the tragus to the most lateral aspect of the eyebrow
What is the course of the spinal accessory nerve?What muscle(s) does it innervate?What are the boundaries of the Danger Zone for this nerve? what are the consequences of injury to the SAN?
SAN emerges into the posterior triangle about midway up the posterior boarder of the SCM muscle at Erbs point
SAN lies on the levator scapulae muscle deep to the deep fascia of the triangle
It innervates the trapezius
An imaginary line from the thyroid notch posteriorly across the posterior triangle.
The area of the posterior triangle 2cm above and below this line is the Danger zone for the SAN
Injury; (DAPI-W)
Dropped shoulder
Aching shoulder
Paraesthesia in the arm
Inability to ABduct shoulder >80 degrees
Winging of the scapula can occur
What are the boundaries of the posterior triangle of the neck?
SCM anteriorly
Trapezius posteriorly
Clavicle inferiroly
Where is Erb’s point?What structures are associated with Erb’s point?
Erbs point is found by drawing a line from the angle of the jaw to the mastoid process. From the midpoint of this line drop a line (6cm) down to the posterior boarder of the SCM
The SAN + 4 cutaneous branches of cervical plexus;
Greater auricular n.
Lesser occipital n.
Supraclavicular nerves
Transverse cervical n.
and the external jugular vein
Where on the face are the fibres of the zygomatic and buccal branches of the facial nerve most at risk?
medial to the ABM and lateral to a line between the outer canthus and the commisure of the mouth
What is the Trigeminocardiac reflex?
Risk of triggering this if operating in the distribution of the ophthalmic or maxillary divisions (close to the orbit) due to the connection of the trigeminal nucleus receiving input from these divisions to the motor fibres of the vagus nerve in the brainstem
Can trigger bradycardia, asystole, apnoea, hypotension or death
