Anatomy & physiology Flashcards
Iris
The colored tissue at the front of the eye that contains the pupil in the center.
Theirishelps control the size of the pupil to let more or less light into the eye.
Limbus
Corneoscleral junction
Lacrimal gland
It continually releases fluid which cleanses and protects the eye’s surface as it lubricates and moistens it.
Sclera
The white layer of theeyethat covers most of the outside of theeyeball.
Conjunctival fornix
Is loose soft tissue lying at the junction between the palpebralconjunctiva(covering the inner surface of the eyelid) and the bulbarconjunctiva
Thelacrimal lake
Is the pool of tears in the lower conjunctival, which drains into the opening of the tear drainage system (the lacrimal punctum).
Inferior lacrimal papilla & punctum
Drainage system for lacrimal fluid
Cornea
Acts as the eye’s outermost lens. It functions like a window that controls and focuses the entry of light into the eye. Thecorneacontributes between 65- 75 percent of the eye’s total focusing power.
Conjunctiva
A loose connective tissue that covers the surface of the eyeball (bulbar conjunctiva) and reflects back upon itself to form the inner layer of the eyelid (palpebral conjunctiva)
What are the 3 layers of the eyes?
Fibrous - outer layer
Uvea (vascular layer) - middle layer
Retina (photosensitive) -inner layer
What are the 2 parts of the outer fibrous layer of the eyes?
- Sclera
2. Cornea
Cilliary body
Controls iris, shape of lens and secretion of aqueous humour.
Contains smooth muscle and blood vessels
Choroid
Nutrition and gas exchange
What are the 3 parts of the Uvea (vascular, middle) layer of the eyes?
- iris
- ciliary body
- choroid
What are the 2 eye segments?
Anterior and posterior
Anterior segment of the eyes
In front of lens (lens behind cornea) - Divided into:
- anterior chamber
- posterior chamber
Posterior segment of the eyes
Behind lens - makes up 2/3rds of eye
Contains vitreous body/humor
Vitreous body/humour
The clear gel that fills the space between the lens and the retina of the eyeball of humans
Anterior chamber of the eyes
Between cornea and iris
Posterior chamber of the eyes
Between iris and suspensory ligaments
Circulation of Aqueous
- Ciliary body produces Aqueous
- First goes to posterior chambers - nourishes lens
- Aqueous then passes through pupil
- Then into anterior chamber - nourishes cornea
- Aqueous reabsorbed into Canal of Schlemn
Canal of Schelmn
Aqueous reabsorbed into scleral venous sinus (Canal of Schlemm) at iridocorneal angle
Where is the Canal of Schelmn?
Iridocorneal angle
The arterial supply of the eyes
Provided by several branches from the ophthalmic artery, which is derived from the internal carotid artery in most mammals.
These branches include the central retinal artery, the short and long posterior ciliary arteries, and the anterior ciliary arteries.
The central vein of the retina
The only vein draining the retina
An end artery
An artery with insufficient anastomoses to maintain viability of the tissue supplied if arterial occlusion occurs
DANGER TRIANGLE of the face
Upper lip/external nose
Venous drainage of the eyes
Carried out by the superior and inferior ophthalmic veins. These drain into the cavernous sinus, a dural venous sinus in close proximity to the eye.
Theretina
Contains millions of light-sensitive cells (rods and cones) and other nerve cells that receive and organize visual information. Yourretinasends this information to your brain through your optic nerve, enabling you to see.
Fundoscopy
A procedure in which the back portion of the eye called the fundus is examined. Fundus includes the blood vessels that feed the eye, the retina, the optic disk, and the choroid.
Optic disc
- The circular area in the back of the inside of theeyewhere theopticnerve connects to the retina.
- Point of CN II formation
Blind spot
There are no photoreceptors in the optic disc - (hence the optic disc is the “blind spot”)
Macula
Part of the retina - greatest density of cones
Fovea
Centre of the macula - Depression of 1.5mm diameter
Area of most acute vision
Complete interruption retinal artery branch/retinal vein
Loss of an area of visual field corresponding to the area of ischaemia
Complete interruption of flow of the central artery (end artery) or vein
Monocular blindness
Lateral rectus
Can only abduct eyeball CN VI (Abducent)
Superior Rectus
When in abduction, SR can only elevate CN III (Oculomotor)
Inferior rectus
When in abduction, IR can only depress CN III (Oculomotor)
Medial rectus
Can only adduct eyeball CN III (Oculomotor)
Inferior oblique
When in adduction, IO can only elevate CN III (Oculomotor)
Superior oblique
When in adduction, SO can only depress CN IV (Trochlear)
How many extraocular muscles are there?
6
Levator palpebrae superioris
Small muscle of the superior orbit that elevates and retracts the upper eyelid.
A blowout fracture
A break in the floor or inner wall of the orbit or eye socket. A crack in the very thin bone that makes up these walls can pinch muscles and other structures around the eye, keeping the eyeball from moving properly.
The orbicularis oculi muscle
Is a muscle located in the eyelids. It is a sphincter muscle arranged in concentric bands around the upper and lower eyelids. The main function is to close the eyelids.
What cranial nerve innervates the orbicularis oculi muscle?
Temporal branch of the seventh cranial nerve (facial nerve)
Superior tarsus muscle
Known as Muller’s muscle, is a structural muscle which functions to maintain the elevation of the upper eyelid.
Superior tarsus muscle innervation
It receives innervation from the sympathetic nervous system and is unique in that it consists of thin fibers of the smooth muscle.
Location of lacrimal gland
Under eyebrows (lateral end of face)
Lacrimal gland innervation
The sensory innervation to the lacrimal gland is via the lacrimal nerve. This is a branch of the ophthalmic nerve (in turn derived from the trigeminal nerve).
What are the 3 branches of the trigeminal nerve?
CN V1 (ophthalmic nerve) CN V2 (maxillary nerve) CN V3 (mandibular nerve)
What does the CN V1 (ophthalmic nerve) innervate?
Sensory innervation to the upper eyelid, cornea, lacrimal gland and conjunctiva
What does the CN V2 (maxillary nerve) innervate?
Sensory innervation to skin of the lower eyelid
and skin over the maxilla
What does the CN V3 (mandibular nerve) innervate?
Sensory innervation to skin over mandible and TMJ
except angle of mandible
Vestibulo-ocular reflex
Turns the eyes in the opposite direction to a head movement
Stabilises gaze on an object during head movement
Oculocardiac reflex
Reflex bradycardia in response to tension on extraocular muscles or pressure on eye
Sympathetic autonomic supply to the eyes
open eyes wider
get more light into eyes
emotional lacrimation
Parasympathetic autonomic supply to the eyes
- Get less light into eyes (to protect the retina from bright light or when asleep)
- focus on near objects
- Reflex lacrimation (to wash away the stimulant foreign body & clean the cornea)
Autonomic reflexes of eye
parasympathetics constrict the pupil - in bright light and “rest & digest”
sympathetic innervation dilates the pupil
- the sick patient
Suspensory ligament of lens
Suspensory ligament of lens connects the circumferences of the lens & the ciliary body
Basal tears
For corneal health
clean/nourish & hydrate the avascular cornea
contain lysozyme - hydrolyses bacterial cell walls