Blood Supply to the Head & Orbit Flashcards
What is the ascending aorta?
The ascending aorta arises from the aortic orifice from the left ventricle and ascends to become the aortic arch. It is 2 inches long in length and travels with the pulmonary trunk in the pericardial sheath.
What does the right common carotid feed into?
Head & Neck
What does the right subclavian artery feed into?
Right upper limb
What does the left common carotid artery supply?
Left side of the head and neck
What does the left subclavian artery supply?
Left upper limb
Sometimes doesn’t have a name as it has multiple branches on it such as the left axillary artery and left brachial artery.
What is the thoracic aorta?
The thoracic (descending) aorta spans from the level of T4 to T12. Continuing from the aortic arch, it initially begins to the left of the vertebral column but approaches the midline as it descends. It leaves the thorax via theaortic hiatus in the diaphragm, and becomes the abdominal aorta
Where do the carotid arteries extend?
Up the neck lateral to the oesophagus and trachea
Where do the carotid arteries split?
2 become 4 at C4. Internal deeper and closer to the midline, external common carotid is on the outside.
What do the carotid arteries border?
Superior border is jawline/mandible, lateral border is the SCM, medially is midline of neck so carotid triangle and the Anterior triangle are the same
Where are baroreceptors?
Baroreceptors are in this area (carotid bodies) and if massaged it can help slow heart rate down by stimulating the baroreceptors by pressing on the common carotid
What is it called where arteries meet and balloon?
Sinus
What is the carotid triangle the same as?
The anterior triangle of the neck
Superiorly– inferior border of the mandible (jawbone).
Laterally– anterior border of the sternocleidomastoid.
Medially– sagittal line down the midline of the neck.
What is the carotid sinus?
Where the internal carotid and common carotid are dilated. This is where baroreceptors are.
What does the external carotid artery supply?
Most lateral, supplies areas of the head and neck external to the cranium
What is the mnemonic to remember the external carotid arteries?
Some
Anatomy
Lecturers
Freak
Out
Poor
Medical
Students
What are the branches of the External Carotid Arteries?
Some -
Superior Thyroid Artery
Anatomists -
Ascending Pharyngeal Artery
Like -
Lingual Artery
Freaking -
Facial Artery
Out -
Occipital Artery
Poor -
Posterior Auricular Artery
Medical -
Maxillary Artery (largest)
Students -
Superficial Temporal Artery
What are the two terminal branches (end arteries) of the external carotid arteries?
Maxillary Artery & Superficial Temporal Artery
What does the Maxillary artery supply?
Mandibular (1st part)
Pterygoid (2nd part)
Pterygopalatine (3rd part)
What does the superficial temporal artery supply?
It’s a branch of the external carotid arteries that supplies superficial structures of the face
What do the internal carotid arteries supply?
Entering the cranial cavity via the carotid canal in the petrous part of the temporal bone. Within the cranial cavity, the internal carotid artery supplies:
- The brain
- Eyes (ipsilateral)
- Forehead
Where are the internal carotid arteries in the neck?
Deeper in the neck
What are the vertebral arteries?
Paired vessels arising from the subclavian arteries.
Thinner than the carotid arteries = more fragile. They run up the neck on the side of the vertebra in a ring to make them more protected as encased in a bit of bone from the cervical vertebra.
Where do the vertebral arteries ascend?
Posterior (behind) the carotids, encased in transverse processes of the cervical vertebrae
Travel up and enter the cranium through the foramen magnum
Where do the vertebral arteries meet? What do they form?
Meet at the base of the brainstem to form the basilar artery. This sits on the pons.
What is the Circle of Willis?
A circular anastomoses that supplies blood to the brain and surrounding structures.
Small variations can exist however the general composition is 3 cerebral arteries and 2 communicating arteries
Bunch of blood vessels that meet together in a ring, called an anastomoses
Why does the Circle of Willis exist?
The arrangement of the brain’s arteries into the circle of Willis is believed to create redundancy (analogous toengineered redundancy) for collateral circulationin thecerebral circulation. If one part of the circle becomes blocked or narrowed (stenosed) or one of the arteries supplying the circle is blocked or narrowed, blood flow from the otherblood vessels can often preserve the cerebral perfusion well enough to avoid the symptoms ofischemia
Where is the Circle of Willis?
Tucked in against the brainstem with the lobes surrounding it
What structures are included in the Circle of Willis?
Anterior spinal arteries =
Dive back to feed the anterior part of the spine
Anterior inferior cerebellar artery = Front, lower part of the cerebellum
Pontine arteries =
Arteries that feed the pons – cranial nerves come from here and the pontine respiratory group etc
Superior cerebellar arteries =
Goes to top of cerebellum
Posterior Cerebral =
Goes to back of the cerebrum
Posterior communicating arteries = Link lower arteries into the circle
Middle cerebral artery =
Commonly affected in strokes, contralateral blood supply
Ophthalmic artery =
Part of the eyes
Anterior communicating artery = Link left and right together
What’s included in the ACA (Anterior Cerebral Artery)?
- Medial frontal lobe
- Superomedial parietal lobe
- Internal capsule (carries both ascending and descending pathways to and from the cerebral cortex from the brainstem
Where does the Middle Cerebral Artery supply?
The most of lateral surface of hemisphere i.e temporal lobe, part of parietal and frontal lobes
What does the Posterior Cerebral Artery supply?
- Midbrain and thalamus
– Occipital lobe and visual cortex - Inferomedial temporal lobe
- Brainstem
What is total circulation stroke (TACS)?
Anterior cerebral artery
How is TACS diagnosed?
Total Anterior Circulation Stroke (TACS)
Anterior and Middle Cerebral Arteries
All 3;
- unilateral weakness or sensory deficit of the face, arm and leg
- Homonymous Hemianopia
- Higher cerebral dysfunction (dysphasia, visuospatial disorder)
How is Partial Anterior Circulation Stroke (PACS) diagnosed?
2 of these 3;
- unilateral weakness or sensory deficit of the face, arm and leg
- Homonymous Hemianopia
- Higher cerebral dysfunction (dysphasia, visuospatial disorder)
What is PACS?
Partial Anterior Circulation Stroke
If furrowing of the vessels, not enough blood to keep them all functioning from Anterior Middle cerebral arteries
Infarct, that’s a big clot, that disintegrates clots, but it disintegrates all other clots but we have microclots everywhere that we need = bleed
What is Lacunar Syndrome (LACS)?
internal structures of brain that communicate with other lobes, between the lobes are communications called internal capsules. If these (Internal capsule) are affected it is a Lacunar Stroke.
How do we diagnose Lacunar Syndrome (LACS)?
One of the following;
- Pure sensory stroke
- Pure motor stroke
- Sensori-motor stroke
- Ataxic hemiparesis
What is Posterior Circulation Syndrome (POCS)?
Issue with the posterior cerebral artery issue
How is What is Posterior Circulation Syndrome (POCS) diagnosed?
One of the following:
- Cranial nerve palsy and contralateral motor/sensory deficit
- Bilateral motor/sensory deficit
- Conjugate eye movement disorder e.g. gaze palsy
- Cerebellar dysfunction e.g. ataxia, nystagmus, vertigo
- Isolated homonymous hemianopia or cortical blindness`
What is the Ophthalmic Artery?
First branch of the ICA once it leaves the cavernous sinus
Where does the Ophthalmic Artery enter the orbit?
Through the optic canal inferior and lateral to the optic nerve
What’s the pathway of the Ophthalmic Artery?
At its origin from the internal carotid artery, the ophthalmic artery lies within the subarachnoid space. As the ophthalmic artery runs forward within the space through the optic canal, it lies within the dural-arachnoid sheath of the optic nerve. On emerging from the optic canal, the artery pierces the meningeal sheath and comes to lie outside it.
In the orbital cavity the artery runs forward for a short distance lateral to the optic nerve and medial to the lateral rectus muscle, the abducent and oculomotor nerves, and the ciliary ganglion.
The artery then turns medially and crosses above the optic nerve, accompanied by the nasociliary nerve. Here it lies inferior to the superior rectus muscle.
On reaching the medial wall of the orbit, it runs forward with the nasociliary nerve above the medial rectus muscle and below the superior oblique. At the medial end of the upper eyelid the ophthalmic artery divides into the supratrochlear and dorsal nasal arteries
What are the 11 branches of the Ophthalmic artery?
Central retinal a.
Ciliary arteries
Lacrimal a.
Muscular branches
Supraorbital a.
Posterior ethmoidal a.
Anterior ethmoidal a.
Meningeal a.
Medial palpebral a.
Supratrochlear a.
Dorsal nasal a.
What’s the central retinal artery?
The first branch of the Ophthalmic artery.
Burrows into optic nerve and travels with the optic nerve. Comes out and splits into superior and inferior retinal arteries. Can get complete occlusion which is called Central Retinal Artery Occlusion.
Where is the central retinal artery?
It’s the first branch of the ophthalmic artery and lies inferolateral to the optic nerve close to the optic canal. It runs forward beneath the optic nerve and turn upward to pierce the dura and arachnoid sheaths of the optic nerve. Runs forward within the optic nerve, with the central retinal vein. Enters the eyeball and divides into a superior and inferior branch. Each of these branches then divides into a superior, inferior, nasal and temporal branch.
What do the long posterior ciliary arteries supply?
Long = front of the eye
Usually 2, pierce sclera and run forward to ciliary body/UVEA structures (anterior part of the eye)
Supply choroid, ciliary body, iris = UVEA.
Middle Vascular Layer
What do the short posterior ciliary arteries supply?
Short = back of the eye
Pierce sclera around entrance of Optic Nerve (ON)
Supply choroid
15-20% cilioretinal artery
What is the anterior ciliary artery?
Supplies the sclera and conjunctiva via tendon insertions of the EOMs
Comes from the Muscular Artery
What does the Lacrimal artery supply?
Lacrimal gland and then moves forward to the eyelids and conjunctiva.
What does the Lacrimal artery run near?
Runs in close association with the LR and runs with the Lacrimal Nerve (CN V, Ophthalmic branch)
Where does the lacrimal artery arise?
Arises from the ophthalmic artery before entering the orbital cavity. Runs forward with the lacrimal nerve, on the superior border of lateral rectus.
What do the Muscular branches of the Ophthalmic artery supply?
Supply the EOM’s. There’s normally 2 to each EOM apart from the SR where there’s only one.
Which are the highly examined branches of the Ophthalmic Artery?
Central Retinal
Ciliary Arteries
Lacrimal
Muscular
What ciliary artery comes off of the muscular branches?
Anterior ciliary arteries - the arteries to the rectus muscles give origin to the anterior ciliary arteries
What nerve runs alongside the supraorbital artery?
Supraorbital nerve
What does the supraorbital artery supply?
Roof of orbit and most superior parts of the orbit (not the recti to obliques, lacrimal supplies eyelids) such as the LPS. And skin and soft tissue around the temporal side of the eye.
The supraorbital artery supplies the levator palpebrae superioris, the diploe of the frontal bone, the frontal sinus, the upper eyelid, and the skin of the forehead and the scalp.
How does the Supraorbital artery travel?
Arises from the Ophthalmic artery as it crosses the optic nerve. It passes superiorly round the medial borders of the superior rectus and levator palpebrae superioris muscles. The artery then runs forward with the supraorbital nerve between the levator and the roof of the orbit.
How does the supraorbital artery leave the orbit?
It leaves the orbit by passing through the supraorbital notch or foramen and ascends to the scalp deep to the frontalis muscle.
Its terminal branches anastomose with branches of the supratrochlear and superficial ternoral arteries
Where does the posterior ethmoidal artery arise from?
The ophthalmic artery when the latter reaches the medial wall of the orbit.
How does the posterior ethmoidal artery travel?
Passes medially between the upper border of the medial rectus muscle and the SO to enter the posterior ethmoidal canal.
What does the Posterior Ethmoidal artery supply?
The posterior ethmoidal air sinuses, the dura of the anterior cranial fossa and the upper part of the nasal muscosa
What does the Anterior Ethmoidal Artery supply?
During this long course the artery supplies the anterior and middle ethmoidal air cells, the frontal air sinus, the meninges, the mucous membrane of the anterior part of the nasal cavity, and the skin of the nose.
Which is larger, the anterior or posterior ethmoidal artery?
Posterior ethmoidal artery
Where does the Anterior Ethmoidal Artery arise? & what route does it follow?
It arises from the ophthalmic artery and enters the anterior ethmoidal canal accompanied by the anterior ethmoidal nerve. The artery then enters the anterior cranial fossa and passes into the nose through the cribriform plate of the ethmoid. It then descends in a groove on the deep surface of the nasal bone to enter the face between the nasal bone and the upper nasal cartilage.
What is the Meningeal artery?
This small artery runs posteriorly through the superior orbital fissure to supply the meninges in the middle cranial fossa (middle of head / around the eye)
When on a slit lamp, what needs to be lined up with the black dot on the lamp?
The lateral canthus
What artery is near the medial canthus?
Near medial canvas are palpebral ligaments where the eyelids are attached at each end (one medial and one lateral). The medial palpebral supplies the medial ligament.
How do the Medial Palpebral arteries travel?
The two medial palpebral arteries arise from the anterior part of the ophthalmic artery below the pulley for the superior oblique muscle. They descend behind the lacrimal sac and pierce the orbital septum above and below the medial palpebral ligament. Each artery passes laterally to enter the upper and lower eyelid and divides into two branches, which form the peripheral and marginal arterial arches. The arches run laterally between the orbicularis oculi muscle and the tarsal plates.
What does the medial palpebral artery supply?
The medial ligament and branches supply the eyelids and conjunctiva
Where is the supratrochlear artery?
Runs above the trochlea, above the SO. Continues into lids and supplies the blood flow to eyelid (but mainly this comes from lacrimal artery) and does blood supply around the trochlea.
How does the supratrochlear artery leave the orbit?
Leaves the orbit by piercing the orbital septum above the pulley for the superior oblique muscle
Which structure is immediately inferior to the supratrochlear artery?
The Trochlea
What does the supratrochlear artery supply?
It is accompanied by the supratrochlear nerve and supplies the skin of the forehead and scalp
& blood supply around the trochlea
What are the features of the dorsal nasal artery?
The dorsal nasal artery, a terminal branch of the ophthalmic artery, pierces the orbital septum. It passes above the medial palpebral ligament and then descends to the side of the nose. It gives off branches to the lacrimal sac and anastomoses with the facial artery.
What are the two terminal branches of the Ophthalmic artery?
Supratrochlear & Dorsal Nasal
What is the blood-ocular barrier system?
The blood–aqueous barrier
&
The blood–retinal barrier (BRB).
What are tight junctions in the blood retinal barrier called?
Zona Occludens Inner
Zona Adherans Outer
What is the Blood Retinal Barrier?
A particularly tight and restrictive physiological barrier that regulates ion, protein and water flux into and out of the retina.
What does the BRB consist of?
Consists of inner and outer components, the inner BRB being formed of tight junctions between retinal capillary endothelial cells and the outer BRB of tight junctions between retinal pigment epithelial cells.
What are the two most frequent and relevant retinal diseases?
Diabetic Retinopathy
Age-Related Macular Degeneration (AMD)
How is Diabetic Retinopathy initiated?
Initiated by an alteration of the inner BRB and neovascular AMD is a result of an alteration of the outer BRB
What happens in macular degeneration (wet form)?
Blood vessel structures start to break down and thus get bleeding
Can you reverse macular degeneration or diabetic retinopathy?
No - can manage them to stop them from getting worse
How do we manage the treatment of retinal disease?
Treatment of retinal diseases must also deal with the BRB either by using its specific transport mechanisms or by circumventing it through intravitreal injections.
Athernosclerosis is what?
Swelling at the bifurication of the common carotid arteries, carotid sinus, produces turbulent flow. Increase risk of Atheronma (fatty material that clogs arteries) formation in this area with the internal carotid most susceptible.
What is Atheroslcerotic?
Atherosclerotic thickening of thetunica intimaof the carotid arteries will reduce blood flow to thebrain, resulting in the variety ofneurologicalsymptoms;
