Eyeball
The eyeball is a spherical structure located in the orbit of the skull. It is the organ of sight, responsible for detecting light and transmitting visual information to the brain.
Structure:
- Sclera: outermost layer, provides protection
- Choroid: middle layer, contains blood vessels
- Retina: innermost layer, contains light-sensitive cells
Location:
- Orbit of the skull
- Positioned in the bony socket
Characteristics:
- Spherical shape
- Outer transparent layer (cornea)
- Pupil regulates light entry
- Iris controls amount of light
- Lens focuses light
Function:
- Detects light
- Transmits visual information to the brain
- Regulates light entry (pupil)
- Focuses light (lens)
Tissue Components:
- Epithelial tissue (corneal epithelium, retinal pigment epithelium)
- Connective tissue (sclera, choroid)
- Muscle tissue (extraocular muscles)
- Nervous tissue (retina, optic nerve)
Functions of Each Tissue:
- Epithelial tissue: protects, provides barrier function
- Connective tissue: provides support, structure
- Muscle tissue: moves the eyeball
- Nervous tissue: transmits visual information
Epithelial Tissue
- Eyeball has a double layer of epithelium, the inner neuroepithelium and the outer pigmented epithelium.
- Neuroepithelium is a single layer of neurosensory cells.
- Pigmented epithelium is a single layer of cells that nourish the retina.
Connective Tissue
- Sclera is a dense connective tissue that provides support and protection to the eyeball.
- Choroid is a vascular connective tissue that nourishes the retina.
- The uvea, which includes the sclera, choroid, and iris, is a pigmented connective tissue.
Muscle Tissue
- Eyeball has six extraocular muscles that control its movements: levator palpebrae superioris, rectus, oblique, and superior and inferior obliques.
- These muscles are attached to the eyeball by tendons and control its movements through a system of pulleys and levers.
Nervous Tissue
- Eyeball has a complex system of nerves that transmit signals to the brain.
- The optic nerve is a bundle of nerve fibers that carries electrical signals from the eyeball to the brain.
- The retina has a complex system of neurons that process visual information.