Anatomy 1- The Eye and Orbit Flashcards
Name the 6 bones which form the orbit?
- Frontal
- Zygomatic
- Maxilla
- Sphenoid
- Ethmoid
- Lacrimal
What bone is closely associated to the orbit but doesn’t actually contribute to it?
Nasal bone
What bone are the optic canal and superior orbital fissure found in?
Sphenoid bone
The supraorbital notch/foramen is found in which bone?
Frontal bone
The infraorbital foramen is found in which bone?
Maxilla
What shape is the bony orbit said to be?
Pyramidal
What is the apex of the bony orbit?
Where is this apex located in relation to the opening of the orbit?
Optic canal- located medially to the opening of the orbit
What bone mainly forms the roof of the orbit?
What bone mainly forms the floor of the orbit?
Roof- frontal bone
Floor- maxilla
What bone mainly forms the lateral wall of the orbit?
What bone mainly forms the medial wall of the orbit?
Lateral- Sphenoid
Medial- Ethmoid
What is the base of the orbit known as? What forms this?
The orbital rim- formed from the superior, inferior, medial and lateral orbital margins
How are the eyes protected from a direct blow?
They are protected by the orbital rim, as anything larger than the diameter between the superior and inferior orbital margins cannot fit
Which is more anterior, the superior or inferior margin?
Superior
Which parts of the orbit are very thin and can be affected by orbital blowout fractures?
Medial wall and orbital floor
Is the orbital rim affected by orbital blowout fractures?
No
What are some complications of orbital blowout fractures?
The orbital contents can become trapped, and the infraorbital NVB can be damaged (causing a sensory deficit to the facial skin)
Fractured zygoma tend to rotate in what direction?
What does this result in?
They rotate medially, towards the floor. This can result in diplopia (double vision)
What is the first layer of the eyelid, beyond the skin?
Orbicularis oculi muscle
What are the two parts of the orbicularis oculi known as?
Which part is directly on the eyelids?
Orbital and palpebral parts- the palpebral part lies directly over the eyelids
What type of muscle is the orbicularis oculi?
What nerve supplies it?
Skeletal muscle, supplied by the facial nerve
What is the orbital septum?
A sheet of fascia which helps prevent spread of infection from superficial to deep
What are tarsi?
Dense connective tissue bands
What do tarsal glands secrete?
What is their function?
They secrete lipids which stop the eyes from sticking together and prevent overflowing of tears
Where does the tendon of the levator palpebrae superioris attach?
What type of muscle is this?
What is its action?
What can it also be known as?
Superior tarsus
Smooth muscle
Elevates the eyelid
Muller’s muscle
What covers the iris?
Cornea
Does the conjunctiva have vessels within it?
Where does it cover?
Yes it has vessels
Covers the sclera
Is there vasculature in the cornea?
No
At what aspect of the eye are lacrimal glands found?
Where does fluid from here pass into?
Lateral aspect
Puncta
What is the coloured part of the eye known as?
Iris
What is the black circle in the middle of the iris known as?
What is the function of this structure?
What type of nervous system supplies this?
Pupil
Light passes through to reach the retina
Autonomic
What is the nerve supply to the lacrimal glands?
Facial nerve (parasympathetics)
Once lacrimal fluid has passed through the lacrimal puncta, where does it eventually reach?
Inferior meatus
Where does the nasolacrimal duct drain into?
The nasal cavity
What are the names of the three layers of the eye, from outer to inner?
- Fibrous
- Uvea (vascular)
- Retina
What two things are found in the fibrous outer layer of the eye?
Sclera (muscle attachment)
Cornea
What three things are found in the uvea of the eye?
Iris, ciliary body, choroid
What are some functions of the ciliary body?
Controls the iris, shape of the lens and secretion of aqueous humour
What is the function of the choroid?
Allow nutrition and gas exchange
What are 3 structures found in the retina layer of the eye which are important to know?
Retina, macula, optic disc
The eye is divided into two segments, what are these?
Where are each of them found?
Anterior- in front of lens
Posterior- behind lens
What is the anterior segment further divided into?
Anterior and posterior chambers
Where is the anterior chamber found?
Where is the posterior chamber found?
Anterior- between cornea and iris
Posterior- between iris and suspensory ligaments
What is the function of the suspensory ligaments?
Attach the lens to the ciliary body
What type of humour does the anterior segment contain?
Aqueous
What type of humour does the posterior segment contain?
Vitreous
A slit lamp views what part of the eye?
Anterior segment
What is a cataract?
Clouding of the lens
What is the ciliary body composed of?
Ciliary (smooth) muscles and blood vessels
What specific part of the ciliary body secretes aqueous humour?
Ciliary processes (internal foldings)
Aqueous humour circulates through which chamber of the eye first? What structure does it nourish here?
Posterior- nourishes the lens
What structure does aqueous humour nourish in the anterior chamber?
Cornea
Where is aqueous humour reabsorbed?
Scleral venous sinus at the iridocorneal angle
Constant production and reabsorption of aqueous humour controls what?
Intra-ocular pressure
The ophthalmic artery is a brach of what?
Internal carotid artery
What is an end artery?
The only blood supply to an area of tissue, if occlusion was to occur the tissue wouldn’t survive
What is an example of an end artery (and corresponding vein) in the eye?
Central artery and vein of the retina
What do the central artery/vein of the retina run within?
The optic nerve
The inferior ophthalmic vein drains mainly into where?
Superior ophthalmic vein
The superior ophthalmic vein drains into where?
Cavernous sinus
What is the posterior area of the retina where light is focused known as?
The fundus
What are the 3 parts of the fundus?
Optic disc, macula and fovea
The optic disc is the site of formation of what nerve?
Optic nerve (CNII)
What is the only point of entry/exit for blood vessels and CNII nerve axons?
Optic disc
The optic disc has no photoreceptors. What is the clinical relevance of this?
It is a blind spot
Which part of the retina has the greatest density of cones?
Macula
Which part of the retina is the centre of the macula and is the area of most acute vision?
Fovea
What is the most posterior layer of the retina?
The photoreceptors
What layer of the retina lies anterior to the photoreceptor cells?
Ganglion cells
What is the most anterior layer of the retina?
Axons of ganglion cells
Where do the retinal vein and arteries lie in relation to the retina?
Anterior
Complete interruption of flow in a retinal artery/vein branch will cause what?
Visual loss in the specific area of the visual field which corresponds to that area of ischaemia
Complete interruption of flow to the central artery or vein will cause what?
Monocular blindness
Light from objects in the right visual field will be processed where?
Left visual cortex
Light from objects in the lower visual field is processed by what?
The upper part of the primary visual cortex
Light from the temporal retina passes the optic chiasm at what side?
The same side it originated from
Light from the nasal retina passes the optic chaise at what side?
The opposite side it originated form (it crosses over)
How many extra-ocular skeletal muscles are there?
7
Where do all the extra-ocular skeletal muscles originate from?
Where do they insert?
What is the exception to this?
Originate from a common tendinous ring.
Insert onto sclera (except LPS)
How many rectus intra-ocular muscles are there? What are they known as?
4 (superior, inferior, medial and lateral)
How many oblique intra-ocular muscles are there? What are they known as?
2 (superior and inferior)
Where does the superior oblique muscle come from?
Sphenoid bone
Where does the superior oblique muscle pass through, to allow it to pass through the eye at an acute angle?
Trochlea
What is the best way to remember the innervation of the intra-ocular muscles?
LR6 SO4 AO3
What intra-ocular muscle does CNVI supply?
Lateral rectus
What intra-ocular muscle does CNIV supply?
Superior oblique
What nerve supplies all the intra-ocular muscles except the lateral rectus and superior oblique?
CNIII
The vertical axis of the eye allows what movements?
Abduction and adduction
The transverse axis of the eye allows what movements?
Elevation and depression
The anteroposterior axis of the eye allows what movements?
Intorsion/extorsion
What two intra-ocular muscles only have 1 movement?
Medial and lateral rectus
What is the only movement of the lateral rectus?
This brings the eye into the same plane as what muscles?
Abduction.
Brings into the plane of superior and inferior rectus
Once the eye is in abduction, what are the only movements of the superior and inferior rectus?
Superior- elevates eye
Inferior- depresses eye
What is the only movement of the medial rectus?
This brings the eye into the same plane as what muscles?
Adduction.
Brings into the plane of the superior and inferior obliques.
Once the eye is in adduction, what are the only movements of the superior and inferior obliques?
Superior- depresses eye
Inferior- elevates eye
The superior rectus and inferior oblique act synergistically to produce what movement?
They act as antagonists to what movement?
Synergists- elevation of the eyes
Antagonists- rotation of the eyes
The superior oblique and inferior rectus act synergistically to produce what movement?
They act as antagonists to what movement?
Synergists- depress the eyes
Antagonists- adduction/abduction
