Sensory Flashcards
What bones make up the anterior skull?
Frontal Nasal Zygomatic Maxilla Mandible
What bones make up the lateral skull?
Frontal Parietal Temporal Occipital Zygomatic Nasal Sphenoid Maxilla Mandible
Where do the different sutures occur on the skull?
The coronal suture is the articulation by frontal and parietal
Saggital is between the two parietals
Lamboid is between parietals and occipital
Squamous is between temporal and parietal
Sphenoparietal is between sphenoid and parietal bones
Occipitomastoid is between Temporal and occipital
What is the pterion and why is it important?
It’s the articulation between the frontal, parietal, temporal and sphenoid bones. It is the weakest part of the skull, and covers the anterior middle meningeal artery. This is a major site of extradural hematoma.
It can also compress CIII, and cause herniation into the brain base.
It’s difficult to determine its location, and there are different frequencies depending on ethnicity.
It also may encapsulate the middle meningeal artery, rather than simply cover it. It lies within a 1cm circle 2cm behind and 1cm above the posterolateral margin of the frontozygomatic suture.
What bones make up the base of the skull?
The maxilla, hard palate, zygomatic, sphenoid, vomer, temporal and occipital bones.
What are the paired bony prominences of the skull?
The mastoid processes, occipital condyles and styloid processes.
What are the main foraminae of the skull and what passes through them?
Incisive foramen: nasopalatine nerves, sphenopalatine vessels
Greater palatine foramen
Foramen ovale (V2)
Foramen spinosum: middle meningeal artery
Carotid canal: int. carotid artery
Jugular foramen: C IX, X, XI, int. jugular vein
Foramen magnum: spinal cord and vertebral arteries
What foramen can you not see in a live skull, but can see in a live skull?
Foramen lacerum: it is filled with cartilage in life.
What bones make up the anterior fossa of the skull?
Frontal bone
Body and lesser wings of sphenoid bone
Ethmoid bone
What bones make up the middle fossa?
Chiasmatic sulcus of body of sphenoid bone and greater winds of sphenoid
Posterior edges of dorsum sellae of sphenoid, petrous part of temporal bone
What bones make up the posterior fossa?
Sorsum sellae of sigmoid, squamous part of occipital bone
Sup petrous temporal bones, parietal bones
What are the main intracranial foraminae of the skull?
Foramen rotundum Foramen ovale Carotid canal Foramen spinosum Jugular foramen Foramen magnum Hypoglossal canal Inf accoustic meatus Foramen lacerum Sup orbital fissure Optic canal Cribiform plate
What are the sinuses of the skull and what is their function?
Frontal sinus Ethmoidal cells Maxillary sinus Nasal cavity Sphenoid sinus These lighten the face, humidify and head inspired air, and increase the resonance of speech
What are the bones that make up the orbit?
Palatine Ethmoid Lacrimal (make up the medial wall) Maxilla (makes up the floor) Zygomatic (makes up the lateral wall) Frontal (makes up the roof) Spehnoid
What are the layers of the eyelid? (From superficial to deep)
Skin Subcutaneous tissue Orbiculus oculi Orbital septum Conjunctiva Tarsus
What is orbiculus oculi?
A nerve that allows us to forcefully shut our eyes. It is supplied by CNVII. It has two parts- the orbital and palpebral parts.
What is the orbital septum?
An extension of the periosteum. It is an attachment point for the tarsus, levator palpebrae superioris, and the superior tarsal muscle.
What is the tarsus?
A plate of dense connective tissue, which protects the eye and has glands to help moisten the eye itself.
What is the blood and nervous supply to the eyelid?
Opthalmic, facial and superior temporal arteries
Sensory nerves are the opthalmic and maxillary
Motor is sympathetics, CNIII and CNVII
Describe the conjunctiva
It is a thin cell layer running around from the skin to the eye surface. It is very vascular, and is responsible for eye redness when injured.
Describe raccoon eyes
The skin and subcutaneous tissue of the eyelid is a potential space, which accumulates blood after injury to the eyes. It can also be due to extradural hematoma, where the blood escapes from the dura elsewhere, and ends up in the eyes even if this is not the site of injury
Describe the muscles that raise the eyelid
Two muscles raise it: Levator palpebral superioris and superior tarsal muscle. They are innervated by CNIII and the sympathetic nervous system, respectively
Loss of function as in horner’s syndrome can cause drooping of the upper eyelid, called ptosis.
What are the three points at which structures enter and leave the orbit?
Superior orbital fissure
Inferior orbital fissure
Optic canal
What structures travel through the optic canal?
Optic nerve
Opthalamic artery
What structures travel through the superior orbital fissure?
Superior opthalmic vein CIV Frontal nerve (CV1) Nasocilliary nerve (CV1) CIII (inf ans sup) CVI Lacrimal nerve (CV1)
What structures travel through the inferior orbital fissure?
Inferior opthalmic vein
Infra orbital vein
Infra orbital artery
Maxillary nerve.
Name the extra-ocular muscles and their nerve supply
Superior, inferior and medial rectus, inf. oblique (CNIII)
Lateral rectus muscle (CNVI)
Sup oblique (CNIV)
Levator palpebrae superioris (CNVII)
What is the common tendinous ring?
A thickening of the periorbita in the posterior part of the orbit, around the orbit and central superior orbital fissure. It is the origin of the extraocular muscles.
How does the lacrimal apparatus work?
Lacrimal gland secretes tear film onto the eye, which then enters the canaliculi, lacrimal sac, and nasolacrimal duct to be excreted from the nose. If you have a closed sac, this can lead to an inability to remove tears
Where does the opthalmic artery arise from?
It comes from the internal carotid artery, wihc then gives off the opthalmic artery before it runs through the optic canal
What veins drain the orbital cavity?
The superior and inferior opthalmic veins
What is the danger triangle of the face?
The sommissures of the mouth to the naison- this is be cause the opthalmic vein communicates with the facial vein at this point, allowing infections to spread from the face to the cranial cavity.
What are the features of the different meninges of the cranium?
The dura mater is the outermost layer. There is a periosteal layer and an inner meningeal layer. The two separate to form intracranial venous structures and the spinal cord
The arachnoid mater is thin and avascular, and doesn’t enter any grooves of the brain save for the longitudinal fissure
The pia mater is a thin membrane that invests in all of the brain’s grooves.
Describe the spinal cord - cranial meninge transition
The meningieal layer of the dura extends down to form the dura mater of the spinal cord, while the periosteal layer ends at the foramen magnum.
Describe the arterial supply of the meninges
The ant, post and middle meningeal arteries, of which the middle is most crucial.
This enters through the foramen spinosum and travels just deep to the pterion. It has ant and post divisions.
Describe the venous drainage of the brain
Cerebellar veins drain into venous sinuses, and eventually to the internal jugular veins.
Diploic veins run between the internal and external bone, and emissary veins run from outside to inside the skull (important for infection)
Describe the sinus dranage of the brain
The sup sagittal sinus runs aong the falx cerebri, and drains into the straight sinus with the inf sagittal sinus. This then drains into the confluence of sinuses, to the Left and right trasverse (along with the sigmoid), and then to the sup. petrosal sinus, and then into the cavernous sinuses either side of the pituitary gland. These then drain into the internal jugular vein, and leave the brain.
What are the paired structures in the cavernous sinus, and do they run in the sinus itself or the walls?
In the sinus are the internal carotid artery and the abducent nerve
In the walls are the trochlear nerve, the maxillary nerve, the occulomotor nerve and the opthalmic nerve.
This means that thrombosis in the cavernous sinus is crucial due to the structures needing to be preserved. Fluid buildup here can crush the nerves and carotid artery
What are the partitions of the brain made by the dura mater?
The falx cerebri (separates hemispheres)
Tendorium cerebellum (separates cortex from cerebellum)
Falx cerebelli (separates halves of the cerebellum)
Diaphragm sellae
How can you tell what is causing a haemorrhage based on its location?
An extradural haemorrhave appears between the dura and the calvarium, and appears lemon shaped. It is classical from a torn middle meningeal artery, assoc. with skull fracture
A subdural haemorrhage forms between the layers of the dura, and is assoc with cerebral veins, particularly in those with atrophy or on anticoagulants
A subarachnoid haemorrhage is a bleed into the subarachnoid space, usually from a ruptured cerebral artery aneurysm of the circle of willis.
Describe the protective features of the eye
It is set in a socket for protection. It is in between bones for growth and development and entry and exit of structures
Has lacrimal glands to flush out water, and is surrounded by fat
The tear film also keeps the eye moist
What are the components of the tear film?
It has the eye epithelium, then mucosa secreted by lacrimal glands, aqueous part secreted by lacrimal glands, and finally oil secreted by meibomian glands
What is subconjunctival haemorrhage?
Common condition, mostly after severe coughing, sneezing or vomiting. Rarely seen with anticoagluants or blood pressure
What is ptosis?
Dysfunction of levator palpebrae superioris. Can be congenital, involuntary, mechanical, myogenic, traumatic or neurogenic- ie due to CNIII palsy or horners syndrome
What are some common refractive errors in the cornea?
Can be myopia- image focussed in front of retina (eye too long)
Can be hyperopia- image focussed behind retina (eye too short)
Can be stigmatism: 2 different planes of focus between horizontal and vertical
What is the cornea and what is its function?
It’s the refractive surface of fixed power, for clarity, protection, ocular rigidity. It does 2/3 of the light focussing. It also sees the image upside down
What is the lens and what is its function?
It’s the refractive surface of variable power, and has a smooth interface with the aqueous part. It’s almost completely made of fibre cells, and has an inner nucleus in the middle. The fibres are laid down in layers after birth, allowing development of sight. It can have cataracts form on the nucleus or the cortex
What is the ciliary body/epithelium and what is its function?
It is used for lens attachment, production of aqueous humour. The ciliary body surrounds the lens, and can contract, causing the lens to thin.
Where does aqueous humour flow in the eye?
It flows through the angle of the eye between the ciliary body and lens to the trabecular network in the anterior chamber. It can get blocked, which causes a spike in ntraocular pressure.
What is an orbital haemorrhage?
Bleeding behind the orbital septum, which increases pressure and can block the orbital nerve
What are some signs of blowout fracture?
Black eye, infraorbital nerve anaesthesia. Can’t fully look up or down
Describe thyroid eye disease
Lid changes- lag, retraction, lagopthalms
- Coular surface inflammation
- Proptosis
- Squint
- Optic neuropathy
How is light and colour received by the eye?
Light enters the eye and hits the fovea and macula. Light is detected by rods (night vision) and cones (colour vision), These then transfer info to connecting and processing cells, and then to ganglion cells in the brain
Where is the blind spot of the eye?
It covers the exit point of the optic nerve, as no photoreceptors overlie it.
Describe glaucoma
Optic neuropathy with specific axonal loss, associated with increased intraoptic pressure. It usually presents with upper and lower eye being lost first
You can have closed angle, where the angle of the eye is closed by the iris, or open angle, with a predisposition to reduced drainage
95% of glaucoma is open angle, so you can see it using gonioscopy. Half of the nerve may be lost before symptom development
Can be associated with diabetes and macular degeneration
What are the layers of the cornea?
Epithelium
Bowman’s membrane
Stroma (collagen lamellae)
Descement’s layer
Endothelium
It’s avascular unles pathological, but the most highly innervated structure in the body
The stroma is regularly spaced, and has an endothelial pump to remove water- this prevents oedma
What is Keratoconus?
Multifactorial but partly genetic, partly environmental aetiology. Causes a steep, thin cornea, usually in late puberty. It can have rapid, gradual or intermittent progression.
What are some common diseases of the lens?
Phacodoneis- wobbly lens and capsule
Cateracts- less opacity and acuity of cornea (can be age, congenital, metabolic, traumatic, toxic causes)
What are zonules?
Microfibres connecting the lens with the ciliary muscle.
What are the five fascias held within the posterior triangle of the neck?
Superficial fascia- fatty tissue with platysma muscle (CVII)
Deep fascia:
- Investing layer. Surrounds neck like a stocking, holding the peripheral muscles around the neck
- Pretracheal layer- engloses the thyroid, larynx/trachea and pharynx/oesophagus. Called buccopharyngeal in the posterior aspect
- Prevertebral: Encompasses the vertebral column and paravertebral muscles. Forms 2 layers with a potential space between them in the anterior aspect
- Carotid sheath- surrounds internal carotid artery, jugular vein and vagus nerve. Made up of the other fascias.
What are the three cervical spaces of the posterior triangle of the neck?
- Pretracheal space is the region between investing and pretracheal layer. It enxtends down from the pharynx/larynx to the ant. mediastinum
-Retropharyngeal space is post- to pharynx oesophagus and ant to prevertebral layer. Extends inferiorly from base of skull to post mediastinum - Prevertebral space- space between layers of the prevertebral fascia, running from the base of the skull to the diaphragm.
You only see these on MRI when there is a pathology (eg. infection)
What are the boundaries of the posterior triangle of the neck?
Ant: Post border of sternocleidomastoid Post: ant border of trapezius Base: Middle third of clavicle Apex: Base of skull on sup. nuchal line Roof: Investing deep fascia Floor: Prevertebral fascia covering semispinalis capitis, spenius capitis, levator scapulae, and scalenus post and med
What are the contents of the post triangle of the neck?
- Occipital artery and greater occipital nerve
- Lymph nodes
- Accessory nerve (about 1.5 cm deep to greater auricular nerve)
- Cutaneous branches of cervical plexus (C1-4)
- Omohyoid muscle
- Transverse cervical and supraclavicular arteries
- Third part of subclavian artery
- Ext. jugular vein
- Some brachial plexus
How does the posterior triangle help in central venous catheterization?
- Catheters may be used for central venous pressure monitoring, administering irritant or chemotherapy or for long term venous access. They are inserted in the internal jugular, subclavian or their junction. The patient is in the trendelenburg position with contralateral head rotation, to dilate the internal jugular. The point where the vein crosses the post sternocleidomastoid is a key landmark
Why do we need to ultrasound the accessory nerve before surgery?
It is easy to damage it especially in lymph node biopsy, and there is a lot of variation between patients
Patients may be left with the inability to rotate their heads or lift their arms up.
What are the components of the external ear?
The auricle is the visible part, and consists of the helix (outer rim), antihelix (inner rim), tragus (pointy cartilage), antitragul, and lobule.
The external acoustic meatus extends between the deepest part of the concha and the tympanic membrane, but not in a straight course.
Its lateral third is cartilaginous, while its inner 2/3s are bony.
What is the innervation of the external ear?
The auricle is innervated superficially by the cervical plexus and V3, and the deeper parts by VII and X
The external acoustic meatus is innervated by V3, X and VII
The tympanic membrane’s outer surface is innervated by V3, VII, IX and X, while its inner surface is by IX
What are some issues that can arise with the external ear? How do you view it using otoscopy?
Swimmers ear is an infection of the external acoustic meatus
Surfers ear is cole water in the ear, making the bony part grow
Otoscopy required us to pull the ear back and up to straighten the EAM
In babies, we pull the ear downwards
