Anatomy pearls Flashcards
What is the distinguishing difference between CNIII and horners
- Pupil:
- CNIII - dilated, unopposed sympathetic (CNIII parasympathetic supply is lost)
- Horner’s - constricted, unopposed parasympathetic,
- CNIII: eye is down and out - unopposed superior oblique (trochlear) and lateral rectus (abducence)
- Horner’s: ptosis, enophthalmus, anhydrosis, small pupil (miosis)
Which nerve supplies sensation to the tongue?
- Tase:
- Glossopharyngeal IX - posterior 1/3rd
- Corda tympani, branch of VII - anterior 2/3
- Somatic sensation:
- glossopharyngeal IX
- Lingual nerve, branch of mandibular division of trigeminal Viii
Which nerve supplies motor sensation to the tongue?
XII, pharyngeal plexus of IX, X
What is the course of CN VII
VII (facial nerve) originated at junction between pons and medulla, crosses posterior cranial fossa, passing into temporal bone in the facial canal and exiting via the stylomastoid foramen
Tell me about the trigeminal nerve?
3 branches: ophthalmic, maxillary, mandibular
sensation to the face + motor supply to muscles of mastication
What do you know about the cranial sutues?
Usually ossify 18-24mo
Before this time the fontanelles are open, they can be seen to bulge in times of increased ICP
when they fuse at birth = craniosyntosis
What is the pterion?
junction of 4 bontes; frontal, parietal, temporal, sphenoidal
Middle meningeal artery runs behind the pterion - injury may damage this and result in extradural H’gge
What are the base of skull foramina?
- Anterior cranial fossa:
- cribriform plate - olfactory n, emissary veins and arteries
- middle cranial fossa:
- optic canal - optic nerve, 3 layers of dura, opthalmic artery and sympathetic
- Superior orbital fissure - CN III, IV, VI, ophthalmic division of CNV, ophthalmic veins; sympathetic; br of middle meningeal & lacrimal arteries
- Foramen rotundum; maxillary division of CN V
- Foramen ovale - mandibular br of CN V, petrosal n, accesory meningeal art
- F Spinosum - middle memningeal artery, meningeal br of mandibular n
- F lacerum - artery and nerve of pterygoid canal, (via carotid canal - internal carotid art and n
- posterior cranial fossa
- F magnum - medulla oblongata surrounded by meninges, spinal roots of accessory n, vertebral arteries with surrounding sympathetic plexus, anterior and posterior spinal arteries, apical ligament of dens, tectoral membrane
- Jugular F - IJV, CN IX, X, XI, inferior petrosal sinus
- Hypoglossal canal - CN XII, meningeal br of ascending pharyngeal artery
- Internal auditory meatus - CN VII, VIII, labyrinthine artery
What passes through the foramen lacerum?
artery and nerve of pterygoid canal
The internal carotid artery passes from the carotid canal in the base of the skull, emerging and coursing superior to foramen lacerum as it exits the carotid canal. The internal carotid artery does not travel through foramen lacerum. The segment of the internal carotid artery that travels above foramen lacerum is called the lacerum segment.
What are the boundaries of the middle cranial fossa?
Anterior = posterior margin of lesser wing, anterior clinoid process and anterior margin of chiasmatic groove of sphenoid
Posterior = crest of petrous temporal bone and dorsum sellae of sphenoid bone, squamous temportal bone, greater wings of sphenoid
Temporal lobe lies inside the middle cranial fossa
Where can the pituitary gland be found?
Sella turcica
What passes through the foramen magnum?
Blood vessles - vertebral arteries, anterior and posterior splinal arteries
Nerves - spinal roots of accessory nerve, sympathetic plexus around the vertebral artery
Tissues - medulla, meninges, tectorial membrane, apical ligament of dens
What runs through the optic canal?
optic nerve, 3 laters of dural, opthalmic artery, sympathetics
What are the contents of the jugular foramen?
IVJ, IX, X, XI, inferior petrosal sinus
What are the branches of the ICA?
no branches in the neck, intracranial -> middle cerebral and posterior communicating arteries
What is the cavernous sinus?
2 cavernous sinuses in the skull- each lying laterally on either side of the sella turcica
contain venous blood
draining the superficial middle cerebral, superior and inferior opthalmic veins & sphenoparietal sinuses
joined by the intercavernous sinuses and themselves drain into the superior and inferior petrosal sinuses
What are the contents of the cavernous sinus?
- ICA (with sympathetic plexus)
- venous blood
- CN VI
- within the lateral wall: CNIII, CNIV, Va, Vb
how does cav sinus thrombosis occur?
- infections of the danger area of the face i.e. those drained via the facial and opthalmic veins - may spread into the cavernous sinus as the draining veins are valveles -> thrombosis
- Sx: painful swelling of the eye, gradual loss of vision, CNIII, IV, V, VI palsies
- infection spreads rapidly due to the intercavernous sinuses
- DDx= CVA
What are the 4 layers of deep cervical fascia?
carotid sheath
prevertebral fascia
pre-tracheal fascia
investing layer of deep cervical fascia - outer layer, deep to platysma
What are the carotid sheath contents?
common carotid artery, IJV, with vagus in between
+ LN
embeded in the wall = ansa cervicalis
What are the contents of pretracheal fascia?
thyroid gland, trachea, oesophagus
what level does common carotid artery bifurfacte?
C4 -> internal and external carotid
surface marking - superior thyroid notch
What are the branches of external carotid artery?
superior thyroid, ascending pharyngeal, lingual, fascial, occipital, posterior auricular, maxillary, superficial temporal
what muscles are contained within the pre-vertebral fascia?
Scalenus anterior, medius, posterior
levator scapulae
splenius capitis
What are the boundaries of the posterior triangle?
Anteriorly - posterior border of SCM
Posteriorly - anterior border of trapezius
Base - middle 3rd of clavicle
Roof = investing layer of deep cervical fascia
floor = prevertebral fascia
What are the contents of the posterior triangle of the neck?
- Vessels - subclavian artery (3rd part); transverse cervical, suprascapular, occipital arteries, transverse cervical, suprascapular & external cervical veins
- Nerves - spinal root of accessory nerves and branches of brachial plexus, phrenic
- muscle - omohyoid
- LN
- Surface marking of spinal bn of CNXI (accessory nerve) - at risk in op in post triangle of neck (1/3 way down SCM), (1/3 way up trapezius) -> weakness in both
Tell me about the anatomy of the thyroid
located below the thyroid cartilage with thyroid isthmus below cricoid cartilage invested in pretracheal fascia
attached to 2nd-4th tracheal rings
during development thyroid gland descends from foramen caecum (2/3rds along length of the tongue from the tip) to loop around beneath the hyoid bone
descent too far results in a retrosternal thyroid
incomplete descent, can lead to a lingual or pyramidal thyroid gland
or result in a thyroglossal duct cyst which can become infected
during removal the middle 1/3rd of the hypod bone should also be excised to prevent recurrence
What is the blood supply of the thyroid?
Superior: superior thyroid artery, branch of external carotid artery
Middle/thyroid ima artery from brachiocephalic trunk
Inferior: inferior thyroid artery, thyrocervical trunk, off subclavian artery
Venous drainage of the thyroid?
Superior and middle thyroid -> ipsilateral IJV
Inferior thryoid -> brachiocephalic vein
How to perform a needle cricothyroid puncture?
emergency procedure
steril conditions as poss
locate cricothyroid membrane; thyroid notch - depression - cricothyroid cartilage
12/14 guage canula to syringe containing 1ml of air, inject air to displace skin plug,
remove needle, secure cannula in place
connect to O2 supply using Y connector -> jet insufflation
1 sec on, 4 sec off
ensure held on it’s way for definitive airway
Thyrohyoid - depresses the hyoid and elevates the larynx
innervated by ansa cervicalis C1
What is the cause of a horse voice following total thyroidectomy?
Operative damage to Recurrent Laryngeal Nerve -> paralysis of ipsilateral cord -> horse voise
RLN runs close to interior thyroid artery
(ELN, external, @risk during ligation of superior thyroid artery)
Semon’s law dictates that if both RLN are damaged -> aiway compromise as both cords will lie in the midline
RLN -> all muscles of the larynx except cricothyroid (ELN, branch of SLN)
How does damage to ELN present?
Change in the patient’s voice/lack of pitch
monotonous speach
cricothyroid -> increasing tension of the vocal cords -> higher pitch
What is the sensory supply to the larynx?
- Above vocal folds = internal laryngeal - branch of SLN*
- Below vocal cords = branch of RLN*
- ILN = sensation above vocal cords, br of SLN
- ELN = cricothyroid muscle
- RLN = sensation below vocal cords + muscles of larynx (except cricothyroid)
What is the corresponding level and pharyngeal arch:
1) Hyoid bone
2) Thyroid cartilage
3) Cricoid cartilage
1) Hyoid bone - C3 - pharyngeal arch 4
2) Thyroid cartilage - C4 - pharyngeal arch 4
3) Cricoid cartilage - C6 - pharyngeal arch 6
What muscle opens the vocal cords?
Posterior cricoarytenoids externally rotate the arytenoids opening the vocal cords
What muscle closes the larynx when swallowing?
Lateral cricoarytenoids
Tell me about the strap muscles
AKA infrahyoid muscles
innervated by parts of ansa cervicalis, except thyrohyoid = C1
sternothyroid, sternohyoid, theyrohyoid, omohyoid
Depress the hyoid bone and larynx during swallowing and speaking
Ansa cervicalis - loop of nerves C1-3 that forms part of the cervical plexus, superficial to internal jugular vein in carotid sheath
Where are the parathyroids found?
Posterior aspect of the thyroid fland
2 on each side
blood supply = inferior thyroid artery = branch of thryocervical trunk = branch of sternoclavicular artery
Inferior parathyroids = 3rd branchial arch embryologicall (along with the thymus)
Superior parathyroids = 4th branchial arch
Sensory supply to the leg
