Sheep Brain Dissection Analysis

My rendition of the surface of the brain.

The sheep brain before any incisions.

In this lab, we dissected a sheep's brain to observe the different sections of the brain and how they work in relation to each other. As we learned before, the brain is divided into different sections. By simply observing the surface of the brain, we can distinguish a few structures, including the cerebrum, which is the front parts of the brain, the cerebellum or bell-shaped lump near the back of the brain, and the brainstem, which protrudes out of the back and bottom of the cerebellum. The cerebrum controls higher brain function, such as thought and action. The cerebellum receives sensory information and regulates voluntary movement, like posture for example. The brain stem controls the flow of messages between the brain and the rest of the body, while also controlling basic bodily functions like breathing.

After making a longitudinal incision to sever the brain into two halves, the right and left hemispheres, even more structures became apparent. What looked like a mere chicken cutlet at first glance now became a complex and organized network of thoughts, each specialized part of the brain controlling its own important part of the sheep's life. Now we could see myelin layers, which appeared as a paler color than the surrounding brain tissue. You can clearly see a
tree-shaped branching bunch of myelin fibers in the cerebellum. Myelin acts as an insulator on the neurons to speed up the process of interpretation, which is why it concentrates in areas of the brain that require ultra-fast processing, like the cerebellum, which I thought looked a lot like cauliflower. We observed the corpus callosum, which was the only thing connecting the two hemispheres, allowing for communication between the two. This is what was severed in split brain patients. We also saw the midbrain, the collective of multiple structures involved with the central nervous system, vision, hearing, etc. Towards the front of the brain was the optic nerve, which transfers visual information from the retina to the brain. The first lump, going from the posterior to the anterior of the brain, was the pons, which controls breathing, communication, taste, hearing, balance and more. The next bump was the medula oblongata, the regulator of breathing, heart and blood vessel function, digestion, sneezing, and swallowing. In front of that was the thalamus, which correlates consciousness, sleep, and sensory interpretation, and then the hypothalamus, which connects the nervous system to the endocrine system through the pituitary gland and the hormones released from it. After making a cross sectional cut, we could see even more clearly the aforementioned myelin, whose presence created white matter. The darker brain matter is called grey matter.