Anatomy 1 - Orbit and the Eye Flashcards
What is an orbital blow out fracture?
A fracture of one or more of the bones of the floor of the orbit (usually caused by indirect trauma i.e. hit another part of the face causing the thinner part of the floor to fracture)
What 3 bones form the orbital margin?
Frontal
Zygomatic
Maxillary
What is an orbital plate?
Part of the bone that forms part of the orbit
What 7 bones make up the orbit?
Frontal Zygomatic Maxillary ethmoid Lacrimal Sphenoid Palatine
What bone does the optic canal pass through?
Sphenoid bone
Name the 2 holes located on the floor of the orbit?
Superior and inferior orbital fissure
What is the purpose of the eyelid?
To protect the eye
What 4 structures of the eyelid help it protect the eye?
outer skin
inner conjuntiva
tarsal plate
Tarsal glands
What do tarsal glands secrete?
Oily substance (special type of sebaceous gland)
What is the purpose of the tarsal plate?
Helps maintain the shape of the eyelids
What is the name of the membranous sheet that acts as the anterior boundary of the orbit?
Orbital septum
Where does the orbital septum extend from?
The orbital rims to the eyelids
What 2 muscles does the eyelids contain?
Obicularis oculi
Levator palpebrae superioris
What muscle closes the eyelids?
Obicularis Oculi
Innervation of obicularis oculi?
CN VII
Which muscle raises the eyelids?
Levator palpebrae superioris
What nerve innervates levator palpebrae superioris?
CN VIII
What is the function of tears?
To keep the eyes moist
Flush out foreign bodies
Contains sugar and oxygen to supply the cornea
What produces tears?
The lacrimal gland
What is the nerve supply to the lacrimal gland?
CN VII
Where do tears pass from the cornea?
The puncta lacrimalia (minute circular opening of the lacrimal canaliculus)
Where do tears pass from the puncta lacrimalia?
Canuliculi
Where do tears pass from the canuliculi?
Lacrimal sac
Where does tears pass from the lacrimal sac?
To the nasolacrimal duct
Where does the nasolacrimal duct drain?
Into the inferior meatus on the lateral wall of the nasal cavity
What is the name of the act of the altering the shape and curvature of the lens to adjust the degree of refraction?
Accommodation
Describe the process of accommodation when focussing on a near object?
the ciliary muscle contract causing the suspensory ligaments to slacken = muscle tension on the lens is low and the lens shape is fat and more curved
Describe the process of accommodation when focussing on a distant object?
the ciliary muscles relax causing the suspensory ligaments to be stretched = muscle tension on the lens is high = thin, less curved lens
What type of muscle is the ciliary muscle?
Smooth muscle
Nerve supply to the sphincter pupillae?
CN III
What are the 2 smooth muscles located within the iris?
Sphincter pupillae
Dilator pupillae
What type of autonomic control is sphincter pupillae under?
Parasympathetic (CN III)
What type of autonomic control is dilator pupillae under?
Sympathetic
When does sphincter pupillae contract?
In bright light, accommodation
When does dilator papillae contract?
Dim light, fright
Name of part of the eye in front of the lens?
What does this contain
Anterior segment
Aqueous humour
Name of the part of the eye behind the lens?
What does this contain
Posterior segment
Vitreous humour
What 2 parts can the anterior segment be broken down to?
Anterior chamber (between cornea and iris) Posterior chamber (between iris and suspensory ligaments)
Name of the 6 extrinsic muscles of the eye?
Superior oblique Inferior oblique Superior rectus Inferior rectus Lateral Rectus Medial rectus
Where do all the rectus muscles originate from?
Common tendinous ring
Where do all the extra ocular muscles insert onto?
Sclera
Action of superior rectus?
Elevates the eye
Action of inferior rectus?
Depresses the eye
Action of lateral rectus?
Abducts the eye
Action of medial rectus?
Adducts the eye
Action of superior oblique muscle?
Down and out (tramp muscle)
Action of inferior oblique muscle?
Up and out
What is the general principle of testing the eye muscles?
Want to test the movement of individual muscles = have to line up gaze to plane of muscles being tested = isolates muscle movement
How to test that action of lateral rectus muscle?
Get the abduct their eye
How to test the action of the medial rectus?
Get the patient to adduct their eye
How to test the action of superior rectus?
Get the patient to look out and up
How to test the action of the inferior rectus?
Get the patient to look out and down
How to test the action of the inferior oblique?
Get the patient to look in and up
How to test the action of the superior oblique?
Get the patient to look in and down
Name of the depression in the frontal bone on the medial part of the optic ridge?
Supraorbital notch/ foramen
Name of the foraminae in the maxillary bone just below the orbital margin?
Infraorbital foramen
What is another name for the base of the orbit?
Orbital rim
What is the orbital rim made from?
The superior, inferior, medial and lateral orbital margins
What 2 parts of the orbit are especially thin?
The medial wall and orbital floor
What is the name of the 2 parts of obicularis oculi?
Orbital and palpebral parts
Name of the ligaments at either corners of the eyes?
Lateral and medial palpebral ligaments
Name of the tendons that immediately surround the eyes?
Superior tarus
Inferior tarus
Name of the tendon extending superiorly from the superior tarus?
Tendon of levator palpebrae superiorus
What is another name for the corneoscleral junction?
the limbus
What happens to aqueous secreted by the ciliary processes?
It circulates within ht posterior chamber nourishing the lens before passing through the pupil into the anterior chamber where it nourishes the cornea
Aqueous is then reabsorbed
Where is aqueous reabsorbed?
Into scleral venous sinus at the iridocorneal angle
What is the fundus?
The posterior area of the eye where light is focused
