Eyes, Ears and Nose

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Last Updated: Saturday, 24 June 2023 22:23
Published: Saturday, 24 June 2023 13:34
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Eyes, Ears and Nose:

These are one of the vital parts of body, especially the eyes. Eyes re also the most fascinating organ.

Eyes:

Nice introductory video: https://www.youtube.com/watch?v=eySkNWTI03Q

Here's multiple diagrams showing internal parts of eye: https://kunnediagram.blogspot.com/2021/06/11-anatomy-of-human-eye-png.html

Main parts of Eyes:

  • Front: The front of the eye is cornea, the bulging part that you can see and feel. The black/brown circle that you see is called the Iris and is actually muscles that relax or contract. The color of the eye that we talk about is the color of the irs, as the color of these muscles depends on a color pigment. The Iris has a hole in the center which is called the pupil. If you look at someone's eye,you will see the big black/brown circle (Iris) and within it the smaller black circle (pupil). This hole is always black in color, as there's no light inside the hole. Just behind this hole is the lens of the eye. This lens is connected to ciliary muscles which change the shape of the lens to focus light rays on the back of our eyes, which is called the retina. The Sclera is the visible white part of the eye. The bulge in front of the iris is the cornea: sclera doesn't have this bulge, bulge is only for the part of the eye that is involved in vision.
  • Back: All of the back surface of the eyeball is retina where there are special light cells called rods and cones which get excited on receiving light rays. These rods/cones are connected to optic nerves, which take the signal from here to the brain for processing. The place where all the optic nerves from the eyes leaves the eyeball is called optic disc.There's no retina here, as that space is needed to bundle all the optic nerves and sendit out of the eyeball. As no picture is formed here, it's the blind spot of the eye. The brain finally makes an image, that remains well in our brain and in our thoughts. If the rays enetring the eyes don't converge exactly onto the retina, then the image will be blurred. It's the job of ciliary muscles to contract/expand to make sure light rays focus on the retina.
  • Liquid: The white thing that we seen in the front is small part of our eyeball. The space between the cornea and the lens is filled with a watery liquid called Aqueous humour. The space between the lens and the back of the eye is filled with a glassy kind of liquid called "Vitreous humour", which helps to maintain the shape of the eyeball.

 

Ears:

Nice introductory video (from Khan Academy, India): https://www.youtube.com/watch?v=98-6WfdumZY

Another video with 3D model of Middle Ear: https://www.youtube.com/watch?v=9fdO9x_Ej2M

Here's multiple diagrams showing internal parts of ear: https://www.researchgate.net/figure/shows-the-basic-anatomy-of-the-human-ear-It-consists-of-three-main-sections-the-outer_fig1_281726806

Main parts of Ears:

  • Outer Ear: The outside of the ear is called the outer ear. The opening in the ear leads to the eardrum.
  • Middle Ear: The eardrum is a very thin layer of skin, mostly translucent, and is called the tympanic membrane. Tympanic membrane needs to carry sound waves from the membrane to the internal ear, which is done via a connection of bones. There are 3 bones that connect this membrane to the inner ear. These are the 3 smallest bones in the human body, and are collectively called ossicles. The 3 bones are named Malleus, Incus and Stapes. Stapes amplify the sound vibrations from eardrum to inner ear by 20X. This is needed as there's liquid inside the inner ear to which it needs to transmit the vibrations. Liquids are denser and so it needs more forceful vibrations to get transmitted.
  • Inner Ear: The inner ear consists of 3 semicircular rings, which helps us with maintaining balance. It has nothing to do with hearing. Cochlea is another structure in inner ear, which is the main part associated with hearing. It has liquid inside it which receives the vibrations from the Stapes and transfers those as electrical signals via the auditory nerves which carry these sound signals to the brain.

There's a Eustachean tube in middle ear, which goes all the way to Pharynx, and has a opeing inside the nose. This means that any bacteria/mucus due to infection in upper nose, will get carried to the eardrum and can be seen from the outer ear when seen via enough light (as the ear drum is translucent). This is the ear infection that little kids generally have. It's frequent in kids but never happens in adults because this tube is small in kids, so it's easy for these bacteria to get carried all the way to the ears, but the long length of tube in adults prevents that from happening.

 

Nose:

Nice video: https://www.youtube.com/watch?v=e3gsndH9q1s

Dr John Campbell's video showing all parts from nose to throat: https://www.youtube.com/watch?v=IrZ3LZqrV7w