Anatomy Lab: The Brain

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three
We can conceptually divide the brain into HOW MANY portions- the cerebrum, cerebellum, and brainstem.
cerebrum
The WHAT is about 83% of its volume and consists of a pair of half globes called the cerebral hemispheres.
gyri
Each cerebral hemisphere is marked by thick folds called the WHAT?
sulci
The gyri is separated by shallow grooves called the WHAT?
longitudinal fissure
A very deep groove, the WHAT, separates the right and left hemispheres from each other. At the bottom of this fissure, the hemispheres are connected by a thick bundle of nerve fibers called the corps callosum- a prominent landmark for anatomical description.
corpus callosum
At the bottom of the longitudinal fissure, the hemispheres are connected by a thick bundle of nerve fibers called the WHAT?
cerebellum
The WHAT occupies the posterior cranial fossa inferior to the cerebrum. It is also marked by gyri, sulci, and fissures. The cerebellum is the second-largest region of the brain; it constitutes about 10% of its volume but contains over 50% of its neurons.
brainstem
WHAT is defined differently by various authorities. It is what remains of the brain if the cerebrum and cerebellum are removed. Its 4 major components are diencephalon (thalamus, the hypothalamus, and the pineal gland), midbrain, pons, and medulla oblongata
diencephalon, midbrain, pons, medulla oblongata
4 major components of the brain stem are?
white matter
bright, pearly white color stemming from the myelin around its nerve fibers. It is composed of tracts, or bundles of axons, which here connect one part of the brain to another and to the spinal cord. Deep to cortex.
gray matter
very little myelin. Site of the neuron cell bodies, dendrites, and synapses. It forms a surface layer called the cortex over the cerebrum and cerebellum, and deeper masses called nuclei surrounded by white matter.
cortex
Gray matter forms a surface layer called WHAT over the cerebrum and cerebellum.
nuclei
Gray matter forms deeper masses called WHAT surrounded by white matter?
deep
White matter lies WHAT to the cortical gray matter in most of the brain.
meninges
The brain is enveloped in three connective tissue membranes, the meninges, which lie between the nervous fissure and bone. These three are the dura mater, arachnoid mater, and pia mater.
dura mater, arachnoid mater, and pia mater
The three connective tissue membranes, the meninges are?
meninges
WHAT protect the brain and provide a structural framework for its arteries and veins.
periosteal layer and meningeal layer
The two layers in the cranial cavity of the dura mater are?
periosteal layer
In the cranial cavity, the dura mater consists of two layers- this is the outer layer equivalent to the periosteum of the cranial bones.
meningeal layer
In the cranial cavity, the dura mater consists of two layers- this is the inner layer. Only this layer continues into the vertebral canal, where it forms the dural sac around the spinal chord.
dural sinuses
In some places, the two layers of the dura mater are separated by WHAT spaces that collect blood that has circulated through the brain. The two major sinuses are superior sagittal sinus and transverse sinus. These sinuses meet like an inverted T at the back of the brain and empty into the internal jugular veins of the neck
superior sagittal sinus
This sinus is found just under the cranium along the median line
transverse sinus
This sinus runs horizontally from the rear of the head toward each ear.
arachnoid mater
WHAT is a transparent membrane over the brain surface.
subarachnoid space
WHAT separates the arachnoid from the pia below.
pia mater
WHAT is a very thin, delicate membrane that closely follows all the contours of the brain, even dipping into the sulci. It is not usually visible without a microscope. (Closely follows contour into sulci and fissures)
ventricles
The brain has four internal chambers called WHAT? Lateral (2), 3rd, and 4th
lateral ventricle
The largest and most rostral ones are the WHAT which form an arc in each cerebral hemisphere.
interventricular foramen
Through a tiny pore called the WHAT each lateral ventricle is connected to the third ventricle.
third ventricle
Through a tiny pore called the interventricular foramen, each lateral ventricle is connected to the WHAT? A narrow median space inferior to the corpus callosum.
cerebral aqueduct
From the third ventricle, a canal called the WHAT passes down the core of the midbrain and leads to the fourth ventricle.
fourth ventricle
WHAT is formed from the cerebral aqueduct and is a small triangular chamber between the pons and cerebellum.
central canal
Caudally, the fourth ventricle narrows and forms a WHAT that extends through the medulla oblongata into the spinal cord.
choroid plexus
On the floor or wall of each ventricle is a spongy mass of blood capillaries called WHAT? Ependyma lines the ventricles and canals and covers this. It produces cerebrospinal fluid.
cerebrospinal fluid
WHAT is a clear, colorless liquid that fills the ventricles and canals of the CNS and bathes its external surface. The brain produces about 500 mL of CSF per day, but the fluid is constantly reabsorbed at the same rate and only 100 to 160 mL is normally present at one time. About 40% of it is formed in the subarachnoid space, 30% by the general ependymal lining of the brain ventricles, and 30% by the choroid plexuses. Most is absorbed in subarachnoid space.
cerebrospinal fluid production
WHAT begins with the filtration of blood plasma through the capillaries of the brain. Ependymal cells modify the the filtrate as it passes through them, so the CSF has more sodium and chloride than blood plasma, but less potassium, calcium, and glucose and very little protein.
cerebrospinal fluid
WHAT is not a stationary fluid but continually flows through and around the CNS, driven partly by its own pressure, partly by the beating of ependymal cilia, and partly by the rhythmic pulsations of the brain produced by each heartbeat.
arachnoid villi
A small amount of CSF fills the central canal of the spinal chord, but ultimately all of it escapes through three pores in the walls of the fourth ventricle- a median aperture and two lateral apertures. These lead into the subarachnoid space on the brain and spinal chord surface. From this space, CSF is reabsorbed by WHAT, extensions of the arachnoid meninx that protrude through the dura mater into the superior sagittal sinus. (CSF is absorbed by WHAT that protrude into superior sagittal sinus)
buoyancy
(purpose of cerebrospinal fluid) Because the brain and CSF are similar in density, the brain neither sinks nor floats in the CSF. It hangs from delicate specialized fibroblasts of the arachnoid meninx. A human brain removed from the body weighs about 1,500 g, but when suspended in CSF its effective weight is only about 50 g. This allows the brain to attain considerable size without being impaired by its own weight. If the brain rested heavily on the floor of the cranium, the pressure would kill the nervous tissue
protection
(purpose of cerebrospinal fluid) CSF also protects the brain from striking the cranium when the head is jolted.
chemical stability
(purpose of cerebrospinal fluid) The flow of CSF rinses metabolic wastes from the nervous tissue and homeostatically regulates its chemical environment. (CSF is ultimately absorbed into the bloodstream. Removes metabolic wastes from brain).
brain barrier system
Although the brain is only 2% of the adult body weight, it receives 15% of the blood and consumes 20% of the oxygen and glucose. Despite its importance tot he brain, the blood is also a source of harmful agents. WHAT strictly regulates what substances can get from the bloodstream into the tissue fluid of the brain.
blood-brain barrier
(BBB) Tight junctions between endothelial cells of blood capillaries
brain barrier system
The WHAT (BBS) is highly permeable (allows liquid to pass through) to water, glucose, and lipid-soluble substances such as oxygen, carbon dioxide, alcohol, caffeine, nicotine, and anesthetics.
hydrocephalus
WHAT is the abnormal accumulation of CSF in the brain, usually resulting from a blockage in its route of flow and reabsorption. It occurs most commonly in the interventricular foramen, cerebral aqueduct, and apertures of the fourth ventricle. The accumulated CSF expands the ventricles and compresses the nervous tissues. In a fetus or infant, it can cause the entire head to enlarge because the cranial bones are not yet fused.
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