The Orbit and Eye - 1 Flashcards
Which 2 holes lie within the sphenoid bone?
The optic foramen and the superior orbital fissure.
What is the roof of the orbital cavity formed by?
It is formed by the orbital process of the frontal bone.
On the lateral side what is the wall of the orbital cavity formed by?
It is formed by the zygomatic bone.
In the floor of the orbit, what is the dominant bone?
The maxilla.
Which bones form the medial part of the orbital cavity?
The small lacrimal bone, part of the ethmoid bone and an insignificant contribution from the palatine bone to the posterior portion of the medial wall of the orbital cavity,
Describe the medial and lateral walls of the orbital cavity.
The medial wall lies in the sagittal plane. The lateral wall diverges outwards as it is traced forwards.
Taking a cross-section of the eyelids, what can we see going from the outside to the inside?
We can see:
- skin
- sphincter muscle called obscularis oculi
- fibrous tarsal plates
- conjunctiva
There is no subcutaneous fat beneath the skin of the eyelids.
Where are the eyelashes found?
They are found at the edge of the eyelids.
What are the tarsal plates for?
Tarsal plates are made of fibrous tissue and they function to stiffen the lids.
Describe the inferior and superior tarsus.
The inferior tarsus is attached to the lower orbital margin and the superior tarsus is larger.
What is adherent to the deep surface of the tarsal plates?
Conjunctiva.
How are the tarsal plates attached to the orbital margin?
Palpebral fascia form an orbital septum. This orbital septum attaches each of the tarsal plates to the orbital margin.
What is the path of the fibres of the levator palpebrae superioris muscle?
The fibres enter the upper eyelid and they attach to the upper part of the tarsal plate. They also extend beyong the tarsal plate and they can intermingle with the fibres of the orbicularis oculi muscle further anteriorly.
What 2 types of fibres are found in levator palpebrae superioris?
There are voluntary fibres and involuntary fibres.
The voluntary fibres are supplied by the 3rd cranial nerve.
The involuntary fibres are supplied by the sympathetic neurones.
What happens when the voluntary and involuntary fibres of the levator palpebrae superioris muscle act together?
They raise the upper eyelid.
What is the function of the medial and lateral palpebral ligaments?
They attach the tarsal plates to the sides of the orbit.
Describe the medial palpebral ligament.
This is strong and lies in front of the lacrimal sac.
What is the medial lacrimal sac?
This is the apparatus that collects tears.
What are the 2 types of glands that are found in the lids?
Ciliary glands and lacrimal glands.
Where are the ciliary glands?
They are placed immediately behind the roots of the eyelashes.
What happens when the ciliary glands become infected?
They form a red swelling on the lid margin called a stye.
Where are the tarsal glands found?
They are found on the deep surface of the tarsal plates.
Where do the ducts of the tarsal glands open onto?
They open onto the the lid margin.
Where do the sensory nerves to the upper lid come from?
They come from the ophthalmic division of the trigeminal nerve.