Sheep Eye Dissection

Here's a picture of the eye before we dissected it! The oval shaped structure in the center is the cornea, which helps focus the light entering the eye. Surrounding the cornea is the sclera, also known as the white of the eye. The sclera is a tough outer coat that protects the eye. It was very hard to cut into it. On top of the sclera is fatty tissue and external eye muscle remnants that we cut off later.

Cornea and sclera seen from the outside of the eye.

Cornea and sclera seen from the inside of the eye.

The small bump on the top of the eye is the optic nerve which sends the visual information from the retina to the brain. 

Here is the eye cut into two hemispheres. On the left, there is the retina and tapetum lucidum. The retina, bunched up at the top on the left, contains the photoreceptors for vision. The blue part under the retina is the tapetum lucidum. It's part of the choroid layer and reflects light onto the retina. The choroid is the black layer that  nourishes the back of the eye. The tapetum lucidum isn't found in humans, but it is in the eyes of many nocturnal animals to help them see at night. The ciliary body is in the right side of the eye. It is made up of muscles and controls and shapes the lens.

The round structure at the bottom of the picture is the lens. The lens changes shape to focus light on the retina. I thought that it would be squishy because it changes shape; however, the lens was hard like a marble. The liquid, which had the consistency of a gel, around the lens is the vitreous humor. It fills the central cavity of the eye. The suspensory ligament can be seen around the lens and connects the lens to the ciliary body.

This is the iris, or the colored portion of the eye. The hole in the center is the pupil. This is where light passes through into the eye.

The Clay Brain

     Our new unit is about the brain, so we made one out of clay in class! After looking through the textbook we started to outline the shape of the brain. We used different colored clay for each part of the brain and then labelled the parts. We shaped the bigger parts of the brain first, like the frontal lobe and temporal lobe. Then we added the smaller parts of the brain like the transverse fissure and central sulcus in between the lobes. This activity helped me learn the names of parts of the brain and how they all are connected.

Missing Parts of the Brain?

     This article is about a woman was able to survive for 24 years without a cerebellum. The cerebellum is essential for motor control, muscle memory, and speech. It modifies the motor commands before sending them to the muscles to make sure the command is accurate. The cerebellum also has about half of the total neurons in the brain. This would explain why the woman had problems keeping balance while walking and felt dizzy. Missing part of the brain is a rare case; cases like these reveal how the brain is able adapt and continue to function even without a large part of it.
     The lateral cerebral sulcus separates the frontal and parietal lobes from the temporal lobe. The sulci are the grooves in the brain. These folds help the brain take in more glucose and oxygen and help the brain fit into our skull. The more grooves an organism's brain has, the more complex functions the organism can perform. An absence of these grooves is known as lissencephaly, which causes developmental delays and brain malformation. Polymicrogyria is a condition where there are too many folds in the brain which can cause neurological problems like seizures, delayed development, and muscle weakness.