Wednesday, May 25, 2011

Pig Dissection Day 3

Heart and Lungs Continued:
We used scissors to cut the blood vessels around the heart.  After examining the heart and the vessels, we examined the back, or dorsal, side of the heart.  Afterwards, the heart was cut lengthwise (the cut was parallel to the front and back of the heart).  Both ventricles and the left atrium were visible inside of the heart.  With the heart removed, we identified the trachea and esophagus.  The trachea is the windpipe that carries air.  The esophagus is the tube that carries food, liquids, and saliva from your mouth to stomach.  The carotid arteris and jugular veins, which carry blood to and from the head, were found on either side of the trachea.  Beneath them was the vagus nerve.  The thyroid gland was placed ventral to the trachea.  It was reddish-brown and had two lobes.  The larynx was located at the top of the trachea.

The Head:

We opened the mouth of the pig and examined the tongue, any teeth visible, and the back of the throat.  We had to use our scalpel to slit the corners of the mouth on both sides in order to view the epiglottis, glottis, and opening to the esophagus.  The pig has four pairs of salivary glands; the largest of these is the parotid gland, which extends from the base of the ear to the shoulder and the jaw.  Using our scalpel, we made an incision through the skin and facial muscles at the base of the ear.  The skin and muscle layer were removed, and we examined the parotid gland.  Beneath the parotid gland was the mandibular gland. 

The Nervous System:

The pig has a very similar nervous system to that of humans.  There is the central nervous system consisting of the brain and spinal cord, and the peripheral nervous system consisting of cranial and spinal nerves and their branches.  Using our scalpel, we made an incision through the skin of the head.  The skin was then peeled off.  Afterwards, we inserted the pointed end of our scissors between the area where the bones of the skull met.  Then we broke off pieces of the skull until most of the skinned area was open.  The outermost membrane of the pig is called the dura mater.  It is the thickest and toughest of the membranes.  The surface of the brain is covered by a thin membrane called the pia mater.  The third membrane is called the arachnoid membrane and is found between the dura mater and pia mater.  In living animals, cerebrospinal fluid fills the space between the two inner membranes.  Our group frist cut through the dura mater, exposing the brain.  We attempted to identify the right and left cerebral hemispheres, cerebellum, cerebrum, olfactory lobes, and the medulla.  We also identified cranial nerves.  The spinal cord was surrounded and protected by the vertebrae of the spinal column.  We removed the skin from an area of the back so around 8~9 cm of the spinal column were exposed.  The remaining tissues were removed so the spiny extensions of the vertebrae were not completly exposed.  We cut off the tops of the spiny extensions of the vertebrae with our scissors and saw the spinal cord and spinal nerves. 

HW: Lab with cover sheet due Friday! (Don't forget to color code diagrams in lab).

Next Scribe: YUNSU Y. (:

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