This document provides an overview of the anatomy of the brain and findings from a necropsy (autopsy) of the brain. It describes the major structural divisions and lobes of the brain, as well as key structures like the cortex, limbic system, basal ganglia, thalamus, brainstem, and cranial nerves. The necropsy section outlines the procedure for removing the brain and describes common findings including pia-arachnoid fibrosis, meningeal congestion, and prolapsed cerebellum. It also discusses using Pandy's reagent to test for excess cerebrospinal fluid proteins which can indicate infections of the central nervous system.

1. Anatomy of Brain and
Necropsy findings:
Submitted to : Sir Imtiaz Ahmed
Submitted by : Abdul Wahab
15-arid-4445

2. Anatomy of brain:
• The central nervous system consists of the brain and the spinal cord. The
peripheral nervous system consists of the extensions of neural structures
beyond the central nervous system and includes somatic and autonomic
divisions.
• The brain is composed of 3 main structural divisions: the cerebrum, the
brainstem, and the cerebellum. At the base of the brain is the brainstem,
which extends from the upper cervical spinal cord to the diencephalon of
the cerebrum. The brainstem is divided into the medulla, pons, and midbrain.
Posterior to the brainstem lies the cerebellum.

4. Cont.…
• Gross Anatomy:
• Cerebrum:
• The cerebrum is the largest component of the brain. It is divided into right and left
hemispheres. The corpus callosum is the collection of white matter fibers that joins
these hemispheres.
• Each of the cerebral hemispheres is further divided into 4 lobes: the frontal lobe,
the parietal lobe, the temporal lobe, and the occipital lobe. The medial temporal
lobe structures are considered by some to be part of the so-called limbic lobe.

5. Cont.…
• Cortex and subcortical fibers:
• The outermost layer of the cerebrum is the cortex, which has a slightly gray
appearance--hence the term "gray matter." The cortex has a folded structure; each
fold is termed a gyrus, while each groove between the folds is termed a sulcus.
• Below the cortex are axons, which are long fibers that emanate from and connect
neurons. Axons are insulated by myelin, which increases the speed of conduction.
Myelin is what gives the white appearance to these fibers of the brain--hence the
term "white matter."

6. Cont.…
• Limbic system:
• The limbic system is a grouping of cortical and subcortical structures
involved in memory formation and emotional responses. The limbic system
allows for complex interactions between the cortex, the thalamus, the
hypothalamus, and the brainstem. The limbic system is not defined by strict
anatomic boundaries but incorporates several important structures. The
limbic structures conventionally include the amygdala, the hippocampus, the
fornix, the mammillary bodies, the cingulate gyrus, and the parahippocampal
gyrus.

7. Cont.…
• Basal nuclei (ganglia):
• The primary input to the basal nuclei is from the primary motor cortex and
premotor cortex (Brodmann areas 4 and 6) and consists primarily of the pyramidal
cells in cortical layer V. These excitatory projections lead primarily to the striatum.
The striatum also receives input from the dopaminergic cells of the substantia nigra.
In turn, the striatum sends inhibitory projections to the globus pallidus externa and
interna. The globus pallidus externa sends inhibitory projections to the subthalamic
nucleus, which sends excitatory projections to the globus pallidus interna. The
globus pallidus interna in turn projects to the ventral anterior and ventral lateral
nuclei of the thalamus.

8. Cont.…
• Thalamus:
• Positioned between the brainstem and the telencephalon, the diencephalon is
composed of the thalamus, the epithalamus, the subthalamus, and the
hypothalamus. The thalamus serves as a relay station for ascending input to the
cortex and receives information from each of the cardinal senses (except smell). It is
hypothesized that the thalamus serves a gating function in filtering information. The
anterior thalamic nuclei are functionally associated with the limbic system and share
reciprocal connections with the cingulate gyrus and the mammillary bodies. The
medial nuclei project to the frontal association cortex and premotor cortex, with
reciprocal connectivity.

9. Cont.…
• Epithalamus:
• The epithalamus is made up of the habenula, the habenular commissure, the posterior commissure,
and the pineal gland.
• Subthalamus:
• Located between the midbrain and the thalamus, the subthalamus contains the subthalamic nucleus, the red
nucleus, and the substantia nigra. Subthalamic structures are closely integrated with the basal nuclei and play
a role in modulation of movement.
• Hypothalamus:
• Thy hypothalamic nuclei lie in the walls of the third ventricle anteriorly. The hypothalamus is involved in
mediating endocrine, autonomic, visceral, and homeostatic functions. It can roughly be divided into anterior,
posterior, and middle groups of nuclei.

10. Cont.…
• Brainstem and Cranial Nerves:
• Evolutionarily, the brainstem is the most ancient part of the brain. Structurally, it
can be divided into the medulla oblongata, pons, and midbrain.
• Medulla oblongata:
• The medulla oblongata, or simply medulla, is continuous with and superior to the
cervical spinal cord. There are several external anatomic features of the medulla that
can be visible grossly. Ventrally, the pyramids and pyramidal decussation is visualized
just below the pons. These are the descending corticospinal tracts. Just lateral to the
pyramids, the rootlets of the hypoglossal nerve can be seen as they exit the
brainstem.

11. Cont.…
• Pons
• Superior to the medulla lies the pons, the ventral surface of which has a
characteristic band of horizontal fibers. These fibers are the pontocerebellar fibers
that are in turn projections from the corticopontine fibers. They cross to enter the
contralateral middle cerebellar peduncle and thus enter the cerebellum.
• Midbrain:
• The midbrain, also termed the mesencephalon, is the superior most aspect of the
brainstem. Ventrally, the midbrain appears as 2 bundles that diverge rostrally as the
cerebral peduncles. Between the cerebral peduncles, the third cranial nerve
(oculomotor) can be seen exiting.

12. Necropsy Findings:
• Removal of Brain:
• Remove the major muscle masses from inside the area of dorsal side of forehead.
• Hold the head with your thumb in the eye socket, and your index finger on top of the blade of
the saw.
• One cut is transverse through the frontal bone, caudal to the zygomatic process of frontal bone.
• Place the head on its right side. Another cut is sagittal, just medial to left occipital condyle.
• Place the head on its left side for one cut. The cranial part of the head is towards you, your
thumb in the eye socket, and your fingers around the mandible.
• Pry up the skull cap.

13. Cont.…
• Use a stronger prying instrument than a knife if the bone was not sawn free.
• Remove Sinuses, nasal cavities, and cranial vault should be examined now.
• Check to see that the tentorium cer- ebelli is removed as well as other limiting dura.
The arrow points to its location.
• With the head in upright position, tap it lightly on the table to loosen the brain.
• Cut the olfactory peduncles, internal carotid arteries, and cranial nerves as the brain
is removed. Tilt the head so that the brain will rest on the table.
• If the brain is not to be kept, cut 1 cm transverse sections for inspection

15. Cont.…
• Clinical Findings:
• Pia-arachnoid Fibrosis:
• This is the common opaque white deposit of soft fibrous connective tissue present in the
meninges of old animals, especially dogs. It is concentrated deep in the sulci, primarily over
the cerebral cortex and the ventral surface of the brain.
• Nodules of connective tissue may be found in the cerebellar meninges of horses. The cause
is considered to be the normal wear and tear of the CNS.
• Meningeal Congestion:
• It is common to see congested meninges due to body position and gravity after death. It is
rarely diagnostic, unless quite distinctly localized.

16. Cont.…
• Meningeal Congestion:
• It is common to see congested meninges due to body position and gravity
after death. It is rarely diagnostic, unless quite distinctly localized.
• Prolapsed Cerebellum:
• This is a common finding at the foramen magnum in many CNS disease
cases, even in chickens.

17. Cont.…
• Pandv’s Reagent and CNS Disease:
• The normal cerebrospinal fluid has only a small amount of protein present but with
most CNS infections and some brain destructive processes, as parasite migration or
trauma, the protein levels can increase significantly.
• In the postmortem room, it is often wanted to have a rapid answer to the question,
“Were the nervous signs seen in this animal the result of an infection, or possibly
due to the often common effect of a metabolic disease, as with fever or grass
tetany,” by which this simple test for excess protein would be helpful differentially.

18. Cont.…
• The Pandy’s reagent is made by boiling pure phenol crystals in sterile water.
The phenol crystals will dissolve and when allowed to cool, the upper layer
of clear fluid will be supersaturated phenol test solution, while the darker
fluid at the bottom is the liquefied phenol itself. The supersaturated phenol is
decanted off for use in the test.
• Rabies and listeria will always be positive and should be considered if it is
positive.
•