Obtain the frontal section of the human brain and identify the following structures:

LONGITUDINAL FISSURE

CORPUS CALLOSUM

LATERAL VENTRICLES

BASAL GANGLIA

DISSECTION OF THE SHEEP BRAIN

MATERIALS

1 DISSECTING TRAY

1 SCAPEL

1 PAIR OF DISSECTING SISSORS

1 DISSECTING PROBE

1 DISSECTING NEEDLE

1 SHEEP BRAIN

Two sheep brains with intact dura mater will be on display at the front of the room.  Examine the specimen and find the falx cerebri and tentorium cerebelli on the dorsal surface.  Compare the composition of the falx cerebri vs the tentorium cerebelli. 

Turn the brain over to examine the pituitary on the ventral surface.  The dense connective tissue covering is called the diaphragm sellae. 

Obtain a sheep brain (one per pair of students).

 Examine the cerebrum and identify the following lobes:  frontal, parietal, occipital and temporal lobes.  Find the longitudinal fissure that separates the right and left cerebral hemispheres. Locate the corpus collosum.  Examine the sulci and gyri on the surface of the cerebrum.

Find the structures in the hind brain: pons, medulla, spinal cord and cerebellum.

Examine the cerebellum.  Compare the structure and size of the folia with the structure and size of the gyri found in the cerebrum. 

Carefully bend the brain in half.   This will expose the midbrain, between the cerebrum and cerebellum. 

Turn the brain over to view the ventral surface.  Find the area where the medulla joins the spinal cord.    Identify the pons and cerebral peduncles in the midbrain.  Identify the mammilary body and find the infundibulum that attaches the pituitary to the brain.

Find the cranial nerves that arise from the surface of the brain.  You may have to observe several brains to see them all.

INTERNAL ANATOMY OF THE BRAIN

Carefully cut through the longitudinal fissure from the anterior portion to the posterior portion, creating a midsagital section. 

Locate the following structures in the cerebrum:  gray matter, white matter, corpus callosum, anterior commissure, fornix,  lateral ventricle, and septum pellucidum.

Locate the following structures in the diencephalons:  intermediate mass, third ventricle, thalamus, hypothalamus, infundibulum, mammillary body.

Locate the following structures in the midbrain:  cerebral aqueduct, cerebral peduncles, pineal gland, corpora quadrigemma, superior colliculi, and inferior colliculi.

Locate the following structures in the rhombencephalon:  pons, medulla, spinal cord.

Locate the following structures in the cerebellum:  arborvitae,  fourth ventricle, gray matter, and white matter.

EXAMINE A PREPARED SLIDE OF GIANT MULTIPOLAR NEURONS AND CEREBRUM.

            Under low power find several multipolar neurons.    Focus on one neuron and increase the magnification.  Find the cell body and nucleus.  Examine the axons and dendrites (it is impossible to tell them apart). 

EXAMINE A PREPARED SLIDE OF A NEUROMUSCULAR JUNCTION.

      Under low  power find several teleodendria and motor end plates.  Focus on one motor end plate and increase the magnification.

REVIEW THE ANATOMY OF THE SPINAL CORD AND LABEL THE DRAWING ABOVE.

Obtain a slide of the spinal cord and examine the microscopic structure of the spinal cord.  View it first at low magnification identifying the following structures:  posterior horn, anterior horn, ventral horn*, gray commissure and central canal.  Look for the meningeal coverings of the spinal cord*

* may or may not be present.

Examine the images of the spinal cord on page 467and 469  looking for the following structures:  white columns, dorsal root, ventral root, dorsal horn, ventral horn, ventral median fissure, dorsal median sulcus, central canal, pia mater, arachnoid mater, dura mater, dorsal rootlets, subdural space, epidural space, subarachnoid space, and dorsal root ganglion.

These may not be present in all views.

ANATOMY OF A SPINAL NERVE

Using the photo provided,  label the fascicles, endoneurium, perineurium and epineurium.

DISSECTION OF THE EYE

MATERIALS

1 DISSECTING TRAY

1 SCAPEL

1 PAIR OF DISSECTING SISSORS

1 DISSECTING PROBE

1 DISSECTING NEEDLE

1 COW OR SHEEP EYE

PROCEDURES

1.                  Place the preserved eye onto the dissecting tray.

2.                  Using the scalpel, dissecting probe and dissecting needle remove the adipose and extra connective tissue covering the eyeball.

3.                  Find the optic nerve, it will be a cylindrical stub on the posterior surface of the eye. 

4.                  Examine the sclera and the cornea.

5.                  Using the scalpel, carefully pierce through the eyeball at the junction of the sclera and cornea. 

6.                  Using the dissecting scissors, carefully cut around the periphery of the cornea.  Be sure not to cut too deeply

7.                  Notice the watery fluid that escapes as you cut open the eyeball.  This is the aqueous humor that fills the anterior chamber.

8.                  Completely remove the cornea and set it aside. 

9.                  Examine the anterior chamber.  Look for the iris, a ring shaped muscle surrounding the opening you created when removing the cornea.

10.              Look for the radial and circular muscle fibers that make up the iris.

11.              Carefully cut around the periphery of the iris and remove it.

12.              Find the amber colored lens, located just behind the iris.  It is hardened in the preserved specimen but would be flexible in a living sample.  Carefully remove it and examine its structure.  Cut it in half and notice the arrangement of the connective tissues that make it up.

13.              Gingerly remove the gelatinous vitreous humor from the posterior chamber.  This will expose a delicate membrane like layer called the retina.  The retina will vary in color from beige to transparent.

14.              After examining the retina, carefully pull it off of the underlying surface. This will expose the underlying choroid layer. It will be a bluish black layer in the sheep or cow eye.