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Organ system histology
Special senses, such as vision, smell, hearing, and balance are senses that use specialized organs and sensory receptors in order to convey information about a person’s surroundings to the central nervous system.
This video will focus on the eyes, which are the sensory organs responsible for vision; and the inner ears, which are the sensory organs responsible for both hearing and balance.
The eyes are complex and highly developed photosensitive organs.
Each eye has three concentric layers or tunics that make up the outer portion of the eye.
And the innermost sensory layer is formed by the retina.
Let’s first take a closer look at the outer fibrous layer or tunic.
The cornea covers the anterior 1/6th of the eye and can be further divided into five sub-layers.
Starting from the surface of the cornea is the corneal epithelium, then the bowman membrane, stroma, descemet’s membrane, and corneal endothelium along the inner surface.
The corneal epithelium is made of non-keratinized stratified squamous epithelium that stains darker than the remaining layers.
Bowman membrane is composed of collagen fibers and has a thickness between 7-12 µm.
When stained with hematoxylin and eosin it can be difficult to identify, but it has a more solid pink appearance when compared to the underlying stroma.
The stroma is the thickest layer of the cornea and is made of collagen fibers and fibroblasts that form a clear and avascular layer of connective tissue that bends or refracts incoming light to help the lens more easily focus light onto the retina.
The eye and ear are both organs of the body that are responsible for receiving sensory information. The eye is responsible for receiving visual information, while the ear is responsible for receiving auditory information.
The eye structures include the eyelashes, lids, muscles, accessory glands, and conjunctiva, and internal structures which include sclera and cornea, the uvea which is the vascular layer in the middle, subdivided into the iris, ciliary body, and choroid; and finally, the retina that consists of nervous tissue.
The ear has three main parts, which are the outer ear, middle ear, and inner ear. The outer ear consists of the auricle, and the external auditory canal and are both lined by keratinized stratified squamous epithelium. The middle ear extends from the tympanic membrane to the oval window of the inner ear, and it is lined with non-keratinized stratified squamous epithelium. Finally, the inner ear consists of the cochlea, semicircular canals and the vestibule.
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