Anatomy of the Eye, Eye muscles and associated structures

Summary

In this detailed anatomy video, Dr. Aan takes us through the complex structures of the eye. He covers its layers, including the fibrous, vascular, and retinal layers, and demonstrates the dissection of various eye muscles responsible for movement. Key points include the anatomy of the eyelids, the iris, pupil, and optic nerve, as well as the importance of the third eyelid in certain animals. The video also explains how to identify the right or left eye and discusses the internal structures such as the retina, lens, and the ciliary body, providing a comprehensive understanding of the eye's anatomy.

Takeaways

• 😀 The eye is located in the orbital cavity, with three eyelids: the upper lid, the lower lid, and the third eyelid, which can be an issue in some animals when foreign bodies get stuck beneath it.
• 😀 The eye has a medial and lateral angle, with the medial angle being more rounded compared to the sharper lateral angle, which helps in identifying the orientation of the eye.
• 😀 The eye is surrounded by a fat pad for protection, and the lacrimal gland is located dorsally-laterally on the eyeball.
• 😀 The fibrous layer of the eye consists of two parts: the sclera (white part) and the transparent cornea, providing structure, protection, and maintaining intraocular pressure.
• 😀 The middle layer of the eye is the vascular layer, while the innermost layer is the retina, which contains nerve cells and sends signals to the optic nerve.
• 😀 The eye has seven muscles that control its movement, including four straight muscles (lateral, medial, dorsal, and ventral straight muscles) and two oblique muscles (ventral and dorsal oblique muscles).
• 😀 The straight muscles are responsible for moving the eye laterally and medially (left and right) and up and down, while the oblique muscles help with rotation and overall movement.
• 😀 The retractor muscle of the eye surrounds the optic nerve and is crucial for controlling the position of the eyeball.
• 😀 The optic nerve is located ventrally on the eye, leaving the eye through the optic canal to reach the brain, which helps in identifying the dorsal and ventral sides of the eye.
• 😀 The eye can be identified as right or left based on the direction of the optic nerve and the rounded medial angle of the eye facing the midline of the head.
• 😀 The lens, located at the center of the eye, is supported by the ciliary body and suspensory ligaments, and it focuses light onto the retina for vision.

Q & A

What are the three layers of the eye?

The three layers of the eye are the fibrous layer (including the sclera and cornea), the vascular layer, and the retina.

What is the function of the third eyelid?

The third eyelid, which is located at the medial angle of the eye, helps protect the eye from foreign bodies like dust or sand and can cause problems if debris gets trapped under it.

How can we distinguish the medial and lateral angles of the eye?

The medial angle of the eye is more rounded compared to the lateral angle, which is sharper.

What is the role of the lacrimal gland in the eye's anatomy?

The lacrimal gland, located dorsal laterally to the eyeball, produces tears that help moisten and protect the eye.

How many muscles are responsible for moving the eye, and what are their names?

There are seven muscles responsible for moving the eye: four straight muscles (lateral, medial, dorsal, and ventral), two oblique muscles (ventral and dorsal oblique), and the retractor muscle.

What is the difference between the function of the straight muscles and the oblique muscles of the eye?

The straight muscles (lateral, medial, dorsal, and ventral) move the eye laterally, medially, up, and down, while the oblique muscles (dorsal and ventral) help in rotating the eye slightly and assisting in lateral and medial movements.

What is the function of the retractor muscle in the eye?

The retractor muscle surrounds the optic nerve and helps in retracting the eyeball into the orbit.

How can one identify the right or left eye even when removed from the orbit?

To identify the right or left eye, check the dorsal and ventral surfaces using the optic nerve as a guide. The medial surface faces the midline (toward the nose) and is more rounded, while the lateral surface is sharper.

What is the role of the iris and pupil in the eye?

The iris is a pigmented structure that forms the pupil, controlling the amount of light entering the eye. The pupil appears black and allows light to pass through to the retina.

What are the components of the vascular layer of the eye?

The vascular layer of the eye includes the ciliary body, which produces aqueous humor and controls the lens, and the iris, which controls the size of the pupil.