The Sensory System
In this lab you will learn about some of the eye and ear structures.
Begin by clicking on the following:
Here you will see the eyes and ears. Let's start with the eye.
Locate the following:
Superior rectus right
Lateral rectus right
Inferior oblique right
Rotate the image to 0 degrees. Locate the medial rectus and superior oblique muscles. These complete the 6 eye muscles. There are 4 rectus and 2 oblique muscles. These are innervated by cranial nerves 3, 4, and 6. Cranial nerve 4 (trochlear) innervates the superior oblique muscle. Cranial nerve 6 (abducens) innervates the lateral rectus muscle. Cranial nerve 3 (occulomotor) innervates all the remaining eye muscles.
The eye consists of 3 layers or tunics. The outer tunic (tunica externa) consists of the cornea and sclera. In this dissection both cornea and sclera are called the eyeball. Go ahead and dissect away the right eyeball.
You can now locate the anterior chamber. The anterior chamber contains a watery fluid called aqueous humor. This fluid is secreted by the ciliary body and circulates around the iris. It drains at the scleral venous sinus otherwise called the canal of Schlemm.
Locate the vitreous humor right. This is located in the posterior chamber and is a jelly-like fluid.
Dissect away the anterior chamber of the eyeball. You should now be able to locate the lens.
The lens is surrounded by suspensory ligaments that hold it in place. The lens is flexible which allows for it to change shape and focus on objects. This is called accomodation. As people age they lose this flexibility and may have to use corrective lenses.
The middle layer or tunic consists of the ciliary body and choroid coat. The choroid coat is a dark layer that provides contrast which helps with vision.
The inner tunic consists of the retina. The retinal contains the visual receptors that convert light into nerve impulses. These are called rods and cones. The rods produce black and white vision and are more sensitive in the dark while the cones produce color vision and are more sensitive in the daylight. On the back of the retina is where the optic nerve enters the eye. This is called the blind spot or optic disc as there are no photoreceptors there. Just lateral to the optic nerve is the fovea centralis which is in direct line with the pupil. This is the area of highest concentration of photoreceptors. This is also the area of sharpest vision.
If the eyeball is too short the image tends to focus behind the retina. This is called farsightendness or hyperopia. Hyperopia is corrected with a convex lens that pulls the image forward.
If the eyeball is too long the image focuses in front of the retina. This is called nearsightedness or myopia. Myopia is corrected with a concave lens that pushes the image backward.
The Ear
Locate the auricular cartilage right. This is also known as the pinna or auricle.
Locate the cavity of the acoustic auditory meatus right. This is also called
the external auditory canal or meatus.
Locate the cartilagenous part of the Pharyngotympanic tube aka Eustachian tube aka auditory tube. This provides a passageway between the middle ear and upper sinuses. It helps to equalize pressure between the middle ear and the atmosphere.
Since the remaining structures on your list are too small to see here you will need to locate these in your textbook.
This concludes the lab.