FETAL PIG DISSECTION - LAB # 5BRAIN AND SPINAL CORD

MATERIALS:scalpelsafety goggles / glasses

forceps (tweezers)Fetal Pig Reference Diagram Booklet

scissorslead & colored pencils

probe bone cutters (needed to remove skull)

pig

dissection pan lined with paper toweling

1 rough draft diagram entitled:

BRAIN AND SPINAL CORD – DORSAL / VENTRAL / LATERAL VIEWS

GENERAL INFORMATION:

This lab is divided into two parts:

PART I = You are going to remove the skull and extract the brain and spinal cord

PART II = you are going to locate, draw, dissect and label parts of the brain.

The labeled, colored diagrams completed in PART IImake up the lab report for this portion of the fetal pig dissection.

PART I

Removing the Brain and Spinal Cord from the Skull and Vertebral Column

You should have already removed the skin and muscle from the head of your pig. If you did not, please do so at this time.

1.Hold the pig’s head so that the snout faces the front of the room. Locate the vertebral column and look into the severed end. You should be able to see the spinal cord surrounded by the vertebral column. The cord is a light colored tube of nerve tissue. Open the scissors and carefully insert one blade point inside the vertebral column so that it is between the spinal cord and the bone on the right side. Cut through this side of the vertebral column. Do not cut or damage the spinal cord!! Repeat the procedure on the left side.

2.The next step is to peel off the dorsal side (top) of the vertebral column. However, the spinal cord is surrounded by a thick, opaque membrane. This membrane also covers the brain. It forms a protective layer called the meninges that is usually stuck to the underside of the vertebrae and skull. There are also nerves that extend through the vertebrae. Carefully loosen the membrane and nerves with the scalpel first and then remove the top of the vertebral column. This should expose the spinal cord and any nerves that branch off it. Try not to remove the meninges as you proceed because it helps hold the brain and spinal cord together.You will have to remove it after the brain is extracted in order to identify the parts.

3.You are now going to cut a "lid" out of the pig’s skull (like cutting a lid out of a Halloween pumpkin). Hold the pig’s head so that you are looking at the snout and eyes. Using the bone cutters, start at the inner corner of one eye socket and work toward the inner cornerof the opposite eye socket. Carefully scrape and snip the bone so that it is cut part of the way through. Be careful not to cut too deep because it is very easy to damage the brain which is like pudding in consistency. After you have reached the inner edge of the opposite eye socket, continue scraping and snipping the top of the eye socket, all the way around the back of the head, and over the top edge of the opposite eye socket. When you are done you should have “carved” a lid on the top of the skull, but not snipped deep enough to damage the brain. Once you have made this initial carving, use the scissors to carefully finish cutting through the bone. Try not to cut through the meninges that covers the brain.

4.Use scissors to cut the suture lines in the top of the skull. This will divide it into four quarters. Starting in the center of the top of the skull, peel the quarters of skull off the top of the head (like peeling the skin off an orange). The meninges will stick to the underside of the skull. You may have to use a scalpel to separate it from the inside of the skull. From this point on, you have to cut and peel off portions of the skull until the brain and spinal cord are exposed. There is no set way to complete this task. You may find it easier to hold the pig’s head in the palm of your hand, or to hold the snout as if it is a handle. Do not remove the eyes at this time. You have successfully completed this step when only the bottom third of the skull remains.

5.If the pig’s head is small, continue to use the snout as a handle. If the pig’s head is larger, cut off the snout in the following way. Use the bone cutters to break the bone, and then use the scissors to complete the job. Carefully cut away any remaining muscle, bone and cartilage from the front of the skull.

6.Turn the brain upside-down. Gravity should help pull the brain away from the remaining skull. Loosen the brain from the bottom of the skull by severing the large nerves that anchor it to the skull. This includes the optic nerves that extend from each eye into the brain. Remove the brain / spinal cord from what remains of your pigs head. You can also remove any meninges that are still present. Refer to diagram # 21 in the Reference Diagram Booklet.

PART II

Brain and Spinal Cord

REFER TO DIAGRAM # 20and # 21 in the Reference Diagram Booklet.

Use the rough draft diagram entitled: BRAIN AND SPINAL CORD - DORSAL / VENTRAL / LONGITUDINAL VIEWS to complete the next section.

1.Place the brain in the pan so that you are looking at the top of the head (dorsal side). The surface of the brain is convoluted. It has many ridges called gyri (singular = gyrus) and many grooves (indentations) called sulci (singular = sulcus). The largest portion of the brain is the cerebrum. It is divided into two halves called cerebral hemispheres. It is divided by a deep indentation called the longitudinal fissure which runs down the center of the cerebrum from anterior to posterior. The cerebral hemispheres are held together by a bridge of connective tissue called the corpus callosum. You will be cutting the corpus callosum later in the dissection. The gyri and sulci are part of the cerebrum. The surface of the brain is called the cerebral cortex.

2.Posterior to the cerebrum is the cerebellum. It is much smaller than the cerebrum. It is separated from the cerebrum by a deep indentationcalled the transverse fissurethat runs from the left side to the right side. The first part of the spinal cord is slightly wider than the rest of the cord. This wide area is the medulla oblongata. A lot more of the medulla oblongata will be seen when you turn the brain over to do the ventral view diagram.

3.Draw a dorsal view of the brain and spinal cord in the designated area.

Label the following:

cerebrumgyrus

longitudinal fissuresulcus

transverse fissuremedulla oblongata

cerebellumspinal cord

4.Turn the brain over so that you are looking at the ventral side. Most of what you see is cerebrum. Use the ventral view picture on diagram page # 21 to help you locate the optic tract and medulla oblongata. The medulla oblongata extends from the spinal cord and covers the middle of the cerebellum on this side of the brain. Only a small portion of the cerebellum on the left and right side of the medulla oblongata is visible from this view. Between the medulla oblongata and the optic tract there are two different areas of tissue. The pons is a small region of tissue that connects to the medulla oblongata. Between the pons and the optic tract is an area of brain tissue that is considered part of the cerebrum for this dissection.

Draw a ventral view of the brain and spinal cord in the designated area.

Label the following:

cerebrumpons

cerebellummedulla oblongata

optic tractspinal cord

5.You are now going to cut the brain in half longitudinally. Turn the brain so that the dorsal side faces the ceiling. Cut down through the longitudinal fissure (front to back). You will sever the corpus callosum that holds the cerebral hemispheres together. The remains of this structure are visible on the inside of the brain. Continue to cut through the cerebellum and spinal cord. Use diagram # 22 in the Reference Diagram Booklet to help you drawand label the inside of one half of the brain and spinal cord.

Label the following:

cerebrumgyrusspinal cord

cerebellumcorpus callosum

sulcustransverse fissure

6.Remove an eyeball and pop out the lens. It looks like a cherry pit. You can now get rid of anything that remains of your pig.

NOW YOU ARE DONE……………AMEN !!!

OVER 

FETAL PIG DISSECTION LAB REPORT # 5 (40 points):

This lab report consists of one final draft diagram page. Each person in the group must have one diagrampage to turn in. Photocopies receive zero credit. The diagrams are graded according to the following criteria:

accuracy of the drawings

neatness and correct spelling of labels

accuracy and legibility of labels

following the directions

1).Once you complete the rough draft page, get a clean copy to make your final draft.

Directions for thediagram page follows. Remember that the gyrus and sulcus are parts of the cerebrum. The fissures are indentations (spaces) between structures and should not be colored.

PAGE 1 – BRAIN AND SPINAL CORD – DORSAL / VENTRAL / LATERAL VIEWS

DORSAL VIEW=Use either a black colored pencil or black pen to outline and label

the structures.Use either a black colored pencil or black pen and a ruler to draw lines

from the labels to the structures. The lines should not cross over each other. Color the

cerebrum red, cerebellum blue, medulla oblongata orange and spinal cord green.

VENTRAL VIEW=Use either a black colored pencil or black pen to outline and label

the structures.Use either a black colored pencil or black pen and a ruler to draw lines

from the labels to the structures. The lines should not cross over each other.

Use the same colors that you used for the dorsal view but color the optic tract

yellowand the pons purple. Remember that the area between the optic tact and

pons is considered part of the cerebrum.

LATERAL VIEW =Use either a black colored pencil or black pen to outline and label

the structures.Use either a black colored pencil or black pen and a ruler to draw lines

from the labels to the structures. The lines should not cross over each other.

Color the cerebellum blue. Color the spinal cord plus the areas labeled medulla

oblongata and pons on diagram #22 in the Reference Diagram Booklet green.

Color the rest of the diagram red.

BRAIN AND SPINAL CORD - DORSAL / VENTRAL / LATERAL VIEWS

BRAIN / SPINAL CORD - DORSAL VIEW

BRAIN / SPINAL CORD - VENTRAL VIEW

BRAIN / SPINAL CORD - LONGITUDINAL SECTION