Hi everyone!
In science this term, we have been focusing into MRS C GREN–specifically the acronym we use to remember the “S” (sensitivity). This refers to how organisms detect and respond to changes in their environment.
To understand how sensitivity works, we first explored the physics of the world around us, learning about how sound waves and light wave stravel. Then, we shifted to biology to see how our bodies actually capture those waves. We studied the complex internal parts of both the ear and eye.
As a way of further extending our knowledge, we got our hands dirty and took a deep dive into an actual organ. We dissected an eye of a cow.
1. What part of the body did we dissect?
The part of the body that we dissected was the eye. Fun fact: cow eyes are actually incredibly similar to the structure of a human. A difference is that they are larger, but that’s actually a good thing because it makes it easier for us to inspect all the individual parts and understand how vision works.
2. The tools we utilised for this experiment are:
- Dissection scissors
- Tweezers
- Scalpel
- Dissecting tray
- Newspaper
3. Steps we took during the dissection:
Here is how we carefully explored the anatomy of the eye, along with the fascinating things we noticed along the way:
Step 1: Karakia
Prior to actually beginning the dissection, we performed a karakia. This shows respect to the animal we sacrificed for this experiment.
Step 2: External Identification
What we did: Before cutting, we looked at the outside of the eyeball to identify the optic nerve at the back and the cornea at the front.
What I saw: The optic nerve looked like a tough, stubby cord extending out of the back, and the cornea was a cloudy, prominent dome on the front.
Step 3: Cutting the Eye Open
What we did: We carefully cut around the middle of the eye to open it up into two halves. We had to be really careful not to accidentally cut into the cornea.
What I saw: As we cut through the tough outer layer, clear fluid began to seep out, and the eye split into a front and back half.
Step 4: Removing the Humorous Jelly
What we did: We identified the retina (which is attached to the optic nerve) and the humorous (vitreous humor). We then pulled the humorous (the clear, jelly-like substance) out of the eye.
What I saw: The humorous was a big lump of clear, thick gelatin. Once it was removed, it revealed a shiny, beautiful metallic blue-green layer at the back of the eye.
Step 5: Extracting the Lens
What we did: We located the lens in the front section of the eye and carefully pulled it out.
What I saw: The lens was solid and shaped like a small marble. When we held it up, we could see how it acts like a natural magnifying glass.
Step 6: Isolating the Iris and Pupil
What we did: We looked closely at the front half to identify the pupil (the empty space in the middle) and the iris (the circular tissue surrounding the pupil). Finally, we removed the iris and the ciliary body (the other black stuff attached to the iris) from the cornea.
What I saw: The iris looked like a dark, circular ring of muscle, and removing it left behind the completely clear, empty window of the cornea.
4. Eye Anatomy Diagram
Optic nerve:
Cornea:
Retina:
Humorous:
Lens:
Iris and pupil:
5. How 3 Key Parts of the Eye Work
To wrap up our lab, here is how three of the coolest parts we found actually function to help us see:
1. The Lens: Located right behind the pupil, this clear, marble-like structure focuses incoming light waves directly onto the back of the eye so we can see crisp images.
2. The Retina: This is the thin, sensitive tissue layer attached to the optic nerve. It acts like a projector screen, capturing light images and converting them into signals for the brain.
3. The Tapetum Lucidum: This is the shiny, colourful metallic layer behind the retina that we saw in Step 3. While humans don’t have it, it reflects light inside the cow’s eye to help them see in the dark!
My final Thoughts:
This dissection was definitely a bit gross at first, but it was an amazing way to see sensitivity in action. Seeing how light waves pass through the cornea, lens, and humour to reach the retina helped me obtain a clearer understanding of how incredible our senses really are. I would have to say my favourite part is definitely taking out the vitreous humorous and lens. Though it had an awfully weird smell and texture, it seemed really interesting, especially the fact that the lens literally works as a magnifying glass. The part in which I didn’t enjoy it as much is when we slowly cut the eyeball in half. As we did this, a bunch of black liquid came oozing out and it was quite vile.