Question

292 Review Sheet 17 Dissection of the Sheep Brain 13. In your own words, describe the firmness and texture of the sheep brain tissue as observed when you cut into it. Given that formalin hardens all tissue, what conclusions might you draw about the firmness and texture of living brain tissue? 14. When comparing human and sheep brai ns, you observed some profound differences between them. Record your observations in the chart below Sheep Ofactory bub Ponvmedula relationship Location of cranial nerve Mammilary body Corpus callosum Relative size of superior and inferior collicul Pineal gland 15. A brain hemorrhage within the region of the right internal capsule results in paralysis of the left side of the body. Explain why the left side (rather than the right side) is affected 16.+Explain why trauma to the brain stem is often much more dangerous than trauma to the frontal lobes. 17. Patients with unresponsive wakefulness syndrome (UWS) have lost awareness of self and their environment. In many cases. there is no damage to the cerebral cortex or the brain stem,. If signal transmission to the cerebral cortex is affected, what part of the brain is most likely to have been damaged? 18. +Patients with unresponsive wakefulness syndrome (UwS) often reflexively respond to visual and auditory stimuli. Explain how this phenomenon relates to the unaffected parts of their brain involved in sensory input

Answer 1

13. ANS: Firmness and texture of the sheep brain: Very soft; much like thickened oatmeal in consistency.

To preserve the dead tissues (anatomically), the tissue are soaked in the solution of formalin. Formalin hardens the tissue very much and prevents the decomposition of the tissue for years together. So, a brain tissue which is preserved in formalin solution definitely gets harden, and the normal tissue must be soft and smooth than the tissue stored in formalin. Particularly a live brain tissue is very soft and needs a very gentle handling because it can be easily torn.

14. ANS:

	Human	Sheep
Olfactory Bulb	Smaller	Bigger
Pons/Medulla Relationship	More inferior straight up and down	More longitudinal to the back
Location of cranial nerve III.	Same area; thinner and lower	Same area; thicker and higher
Mammillary Body	Larger	smaller
Corpus Callosum	Thicker; Straighter direction	Thinner; More slanted direction
Interthalamic Adhesion	Pressed up against the corpus callosum	Smaller; small space between thalamus and corpus callosum
Relative size of the superior and inferior colliculi	Larger	smaller
Pineal Gland	Smaller	Larger

15. ANS: At the decussation of pyramids in the medulla oblongata, the major motor tracts cross over. This means that the right side of the brain controls the motor movements of the left side of the body, so when the right internal capsule is damaged, the left side of the body is affected.

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