Anatomy Flashcards
Where does the eyeball sit?
In the orbit
What 6 bones make up the orbit?
Frontal Zygomatic Sphenoid Ethmoid Lacrimal Maxilla
What bone forms the roof of the orbit?
Frontal bone
What bone forms the floor of the orbit?
Maxilla
What bones form the lateral wall of the orbit?
Zygomatic and sphenoid
What bones form the medial wall of the orbit?
Ethmoid and lacrimal
What are orbital plates?
The part of bone the bones that lines the orbit.
What three features can be found on the sphenoid bone?
Optic canal
Superior Orbital Fissure
Inferior Orbital FIssure
What feature can be found on the frontal bone?
Supraorbital notch
What feature can be found in the maxilla?
Infraorbital foramen
What passes through the infraorbital foramen?
Sensory nerves to the nose and cheeks
What happens in an orbital blow out fracture?
Increased pressure forces the eyeball through the thin ethmoid bone.
What muscles are responsible for opening the eyes?
Levator palpebrae superioris
What do the levator palpebrae superioris muscles do?
Open the eyes
What nerve supplies the levator palpebrae superioris muscles?
CNIII
What does CNIII palsy lead to with the levator palpebrae superioris?
Ptosis- in ability to open eye
What muscle allows us to close our eyes?
Orbicularis Oculi (lets you get some shut eye)
What protective features does the eyelid poses?
Outer skin
Eyelashes
Inner conjunctiva
Describe the inner conjunctiva
Continuous layer from inner eyelid over eyeball for protection
What is the tarsal plate?
Stiff plate in eyelid to maintain shape and secrets lipids to protect eyes.
Where are lacrimal glands located?
On the underside of the bone in the superior lateral aspect of the orbit.
What do lacrimal glands do?
Secrete tears
Where do tears drain to?
Canaliculi in medial aspect of eye then on to nasal cavity.
What does canaliculi mean?
Little canal
What nerve innervates the lacrimal gland?
CNVII- Parasympathetic
What are the three layers of the eyeball?
Fibrous outer layer
Vascular Uvea
Photosensitive retina
What is the fibrous outer layer of the eye made up of ?
White sclera and clear cornea
What is the vascular uvea middle layer made up of?
Iris
Ciliary body
Choroid
What does the iris do?
Regulate amount of light entering the eye
What does the ciliary body do?
Controls iris and lens size/shape
Secretes aqueous humour
What occurs at the choroid?
Nutrient and gas exchange.
Appears black due to lots of melanin
What occurs at the photosensitive retina?
Detection of light
What two segments make up the eyeball?
Anterior segment
Posterior segment
What two chambers make up the anterior segment of the eyeball?
Anterior chamber
Posterior chamber
What are the boundaries of the anterior chamber?
Cornea and iris
What are the boundaries of the posterior chamber?
Iria and ligaments from ciliary body
What is contained in the anterior segment of the eyeball?
Aqueous humour
What constitutes the posterior segment of the eyeball?
Everything behind the lens
What is contained in the posterior segment of the eyeball?
Vitreous fluid which cannot be replaced.
Describe the role of aqueous humour?
Nurish cornea
Where is aqueous humour reabsorbed?
Scleral venous sinus at iridocorneal angle
What happens at the iridocorneal angle?
Aqueous humour is reabsorbed into the scleral venous sinus
Describe the blood supply to the orbit?
Common carotid -> Internal carotid -> Ophthalmic artery
Where does the ophthalmic artery enter the orbit?
Through the optic canal with the optic nerve
What subdivisions does the opthalmic artery give rise to?
Central artery of the retina
Ciliary arteries
Ophthalmic then supplies muscles of eye movement.
What does the central artery of the retina do?
Supplies the retinal layer
What runs with the central artery of the retina?
Central vein of the retina
What two veins does the orbit blood flow ultimately drain into?
Facial vein anteriorly
Cavernous sinus posteriorly
What feature of the sphenoid bone allows venous drainage into the cavernous sinus?
Superior orbital fissure
What is the fundus of the eye?
Posterior area where light is focused
What is the macula?
Area with greatest density of cones therefore best vision here
What is the optic disk?
Outflow from eyeball where the nerves run to form CNII.
Gives rise to the blind spot of the eye.
What is the fovea?
Centre of the macula where the macula lutea is found
What three features of the fundus are important to know?
Macula
Fovea
Optic disk
How many extrinsic muscles of the eye are there?
6
What two categories of extrinsic muscles of the eye are there?
Rectus
Oblique
How many rectus muscles are there and name them
Superior rectus
Inferior rectus
Lateral rectus
Medial rectus
How many oblique muscles are there and name them
Superior oblique
Inferior oblique
Where do all the extrinsic muscles of the eye insert?
Sclera
What do the rectus muscles do?
Move the eye in their direction
What movement does the superior oblique muscle do?
Intorsion- Rotate nasally
Down and out (think tramps)
What movement does the inferior oblique muscle do?
Up and out
What movement do both oblique muscles do?
Out (Oblique goes out)
What does the superior oblique muscle pass through?
Trochlea
What nerve supplies the superior oblique muscle?
Trochlear (CNIV)
What nerve supplies the lateral rectus muscle?
Abducens (CNVI)
What nerve supplies all extrinsic muscles of the eye bar superior oblique and lateral rectus?
Oculomotor (CNIII)
What passes through the superior orbital fissure?
CNIII, IV, V1 and VI
Ophthalmic vein
Where does the nasolacrimal duct drain?
Inferior meatus
