Anatomy of the Eye Flashcards
Where are the eyeballs located and what is their position within the orbit?
The eyeballs are located in orbits on either side of the nasal cavity. Each eyeball occupies the anterior one-third of the orbit.
What is the function of the adipose tissue in the orbit?
The adipose tissue provides protective cushioning and keeps the eyeball in the proper position. It occupies the posterior two-thirds of the orbit.
What are the eyelids and what is their function?
The eyelids, or palpebrae, are two thin folds that cover the anterior region of the orbit. They prevent access by foreign objects and distribute tears during blinking.
What are the anatomical features of the eyelids?
The eyelids have several anatomical features. The tarsal plates are thin pieces of dense regular collagenous connective tissue that reinforce each eyelid. The tarsal glands are modified sebaceous glands located within the tarsal plates that secrete oil to prevent the eyelids from sticking together.
What are the eyebrows and eyelashes and what are their functions?
The hairs on the ridge of the brow form the eyebrows, which prevent perspiration from running into the eyes, reduce glare from bright light, and are important for facial expression. The eyelashes are stiff hairs on the edges of the eyelids that are associated with sensitive nerve endings. They cause blinking when objects touch them, reducing the risk of eye injury.
What is the conjunctiva and where is it located?
The conjunctiva is a thin continuous epithelial membrane that lines both the posterior surfaces of the eyelids and the anterior surface of the eyeball. It is a translucent membrane in which tiny blood vessels can be seen.
What is the lacrimal apparatus and what is its function?
The lacrimal apparatus produces and drains tears from the eye.
What are the components of the lacrimal apparatus and how do they function?
The lacrimal apparatus consists of the lacrimal gland, which is located in the superolateral region of the orbit posterior to the conjunctiva. It releases tears and mucus into tiny ducts that enter the conjunctival sac when stimulated by autonomic neurons. Blinking sweeps the tears medially and inferiorly across the eye surface, and they drain into passages that lead to the nasal cavity.
What are the extrinsic eye muscles and what are their functions?
The extrinsic eye muscles are six muscles that originate from the orbit wall and insert into the outer layer of the eyeball. They allow for precision movements.
What are the different types of rectus muscles and how do they move the eyeball?
The superior, inferior, lateral, and medial rectus muscles extend from a common tendinous ring on the posterior wall to their respective insertion sites on the eyeball. Each rectus muscle moves the eyeball primarily in the direction for which the muscle is named. The superior and inferior rectus muscles move the eyeball medially in addition to superiorly and inferiorly, respectively.
What is the superior oblique muscle and what is its function?
The superior oblique muscle travels from the posterior orbit along the medial wall and through a fibrous loop (trochlea) before inserting into the superior part of the eyeball. It helps to rotate the eye downward and laterally.
What is the function of the inferior oblique muscle in the eye?
The inferior oblique muscle originates from the medial floor of the orbit to insert on the inferolateral aspect of the eyeball. Its contraction elevates and moves the eye laterally.
How many cranial nerves provide innervation to the six muscles of the eye and which muscles do they innervate?
Three cranial nerves provide innervation to the six muscles of the eye. CN IV innervates the superior oblique, CN VI innervates the lateral rectus, and CN III innervates the remaining four muscles.
What is strabismus and what are its effects?
Strabismus, also known as lazy eye, is a disorder present at birth where the eyeballs are not properly aligned with one another. This leads to diplopia, or double vision.
What is the structure of the eyeball and what are its main components?
The eyeball is a hollow sphere that consists of an outer wall that surrounds several chambers and supports the lens, which focuses light as it enters the eye.
What are the three distinct tissue layers that maintain the shape of the eyeball and transduce light into electrical signals?
The three distinct tissue layers that maintain the shape of the eyeball and transduce light into electrical signals are the fibrous layer, the vascular layer, and the neural layer.
