Lab One :

Meninges
Three layers of outer coverings of neural tissue. The dura mater, arachnoid layer, or pia mater.

Dura mater
Dark, fibrous covering of the CNS (varies from dark grey to grayish white in appearance). The dura’s thickness varies from several to a considerable number of cells. It forms a “bag or sac” around neural structures. Its toughness derives from its fibrous make up. It is seperated from covering bone by an area containing fat and blood vessels. Being tough and somewhat resilient, the dura protects the CNS against penetration.

Along the dorsal midline surface of the brain, the dura is two layers thick. The two layers contain
A) Cerebrospinal fluid (CSF) in “cisterns”
B) A large venous drainage system called the sagittal sinus

The Falx Cerebri is a structure in the brain made of tough connective tissue. It sits on top of the brain and goes down into the Longitudinal Fissure, which is the deep groove that separates the brain's two halves (the left and right cerebral hemispheres).

At the back of the brain, where the Occipital Lobes spread out, there’s another structure called the Tentorium Cerebelli. It acts like a roof over the space between the Cerebrum (the larger, upper part of the brain) and the Cerebellum (the smaller, lower part). This "roof" also dips into the area between the back part of the cerebral hemispheres and the front part of the cerebellum. Parts of it wrap around the midbrain and connect to bones on the underside of the brain.

If you're examining a brain with its protective covering (the dura mater) still intact, you'll notice the Tentorium Cerebelli feels especially tough. If you cut through the Falx Cerebri, you can see its internal spaces, which hold cerebrospinal fluid (CSF). Inside the Falx Cerebri, you'll also find dark areas that are remnants of blood and blood vessels. These vessels form the Sagittal Sinus, a large vein that drains blood from the top part of the brain.

Arachnoid
The arachnoid is a thin, delicate layer of connective tissue that surrounds the brain. It sits beneath the dura mater (the tough outer covering) and is separated from it by a small space called the subdural space. Unlike the dura, the arachnoid is not as thick and has a glossy, smooth appearance, often visible on the surface of the brain. It's crisscrossed by blood vessels, making it easy to spot.

The name "arachnoid" comes from its spider-like appearance under magnification. This is due to tiny, web-like fibers called trabeculae that extend into the space below it, called the subarachnoid space. This space is important because it allows cerebrospinal fluid (CSF) to flow, which helps remove waste from the brain and cushion it from injury. The trabeculae provide additional support, like cross-beams in a structure, helping to absorb shocks and protect small blood vessels from tearing or rupturing.

Pia Mater:
A thin membrane composed of a single layer of primarily epithelial cells which cover the neural tissue like a tight fitting rubber gloved. Unlike other meninges, the pia covers the CNS extremities into every nook and cranny of the CNS

CSF 
A clear fluid found in specific spaces within the brain and spinal cord. It’s made from blood through a filtering process that hapens in a special structuee caledd the choroid plexus, a network of tiny blood vessels. The choroid plexus is mainly located in the brain’s ventricles, and you can often see it in the lateral ventricles during dissections, where it looks like a bluish-black tangled material.

What does it do: 
1. Protects the Brain: CSF acts like a cushion to help absorb shocks and protect the brain from injuries.
2. Supports the Brain: It makes the brain "float," reducing its weight so the neck and skull can handle it more easily.
3. Provides Nutrients: It delivers important nutrients and electrolytes that brain cells need to work properly.
4. Regulates Pressure: CSF helps maintain stable pressure inside and around the brain and spinal cord.
Brain Surface Features:

The lateral (side) and dorsal (top) surfaces of the brain have fewer structures, mainly landmarks of the Neocortex. This is the newer part of the brain in terms of evolution. It has six layers, each with different types of cells and fibers.
The arachnoid membrane (if still present) is noticeable because it contains many blood vessels that follow the fissures (valleys or grooves) in the brain. The ridges between the fissures are called gyri (singular: gyrus), and the grooves are called sulci (singular: sulcus).
Key Structures:

Ansate (Central) Sulcus:
A short groove on the dorsal surface, extending from the longitudinal fissure (which divides the brain into left and right hemispheres).
In front of this sulcus is the Primary Motor Cortex, which controls movement and contains many large pyramidal cells. Their axons form major motor tracts.
Behind this sulcus is the Primary Somatosensory Cortex, which processes touch and tactile information.
Medial Longitudinal Fissure:
A deep groove on the dorsal surface that separates the brain's two hemispheres.
Marginal (Lateral) Sulcus:
Roughly marks the boundary between the Occipital Lobe (involved in vision) and the Parietal Lobe (processes sensory information like touch).
This sulcus is one of three grooves on the back part of the brain:
Endomarginal Sulcus: Closest to the middle.
Marginal Sulcus: Lies farther out.
Ectomarginal Sulcus: Marks the boundary between the Parietal and Temporal Lobes (important for hearing and language in humans).
Other Notable Fissures:

Pseudosylvian Fissure:
A T-shaped groove near the front of the brain, marking the division between the Frontal Lobe, Parietal Lobe, and Temporal Lobe.
In humans, the equivalent is the Sylvian Fissure, which is larger and slanted. This fissure also separates the frontal and parietal lobes from the temporal lobe.
Temporal Lobe:

In humans, the Temporal Lobes are responsible for hearing and speech perception, particularly on the left side.
In sheep, the temporal lobes are less developed since they don’t need to process speech. They lie along the Rhinal Fissure and are less prominent compared to humans.
Comparison with Humans:

Sheep brains and human brains have similar structures but differ in shape and complexity. For example:
Humans have bulging temporal lobes, while sheep have flatter ones.
Humans have more grooves (sulci) in the Temporal Lobe, dividing it into finer regions for specific functions.
It’s helpful to compare models of human and sheep brains to see these differences more clearly.