Cranium, Scalp, Meninges and Brain Flashcards
The brain is protected and isolated by multiple structures. Describe them
- Bony cranium - rigid support
- Connective tissue membranes - meninges - surround and partition portions of the brain
- Cerebrospinal fluid - cushioning fluid
- blood-brain barrier - prevent entry of pathogens
What are the layers of the Scalp?
Skin Connective tissue Aponeurosis Loose connective tissue Pericranium
Three dense regular connective tissue layers separate soft tissue of the brain from what?
the bones of the cranium
The cranial meninges enclose and protect what? What do they contain.
blood vessels that supply the brain
Contain and circulate cerebrospinal fluid
Parts of the cranial meninges form some of what?
veins that drain blood from the brain
From superficial to deep, what are the layers of the cranial meninges?
Dura mater
Arachnoid
and Pia mater
What layer is the tough membrane composed of two fibrous layers and is strongest of the meninges?
Dura Mater
What are the two layers of Dura mater?
Perisosteal layer - the more superficial layers and attaches to the periosteium of the cranial bones
Meningeal layer - lies deep to the periosteal layer
The meningeal layer is usually fused to the periosteal layer except when?
In specific areas where the two layers separate to form large, blood-filled spaces called dural venous sinuses
What meningeal layer lies immediately internal to the dura mater?
Arachnoid
What meningeal layer is partially composed of a delicate web of collagen and elastic fibers?
Arachnoid
Termed the arachnoid trabeculae
What is between the arachnoid and the overlying dura mater?
Subdural space
What is immediately deep to the arachnoid?
Subarachnoid space
What is immediately deep to the arachnoid ?
Subarachnoid space
What is the innermost of the cranial meninges?
Pia mater
What meningeal layer is a thin layer of delicate connective tissue that tightly adheres to the brain and follows every contour of the brain surface?
Pia mater
THe meningeal layers of the dura mater extends as flat partitions (septa) deep into the cranial cavity at four locations called what?
Cranial dural septa
The membranous partitions separate what specific parts of the brain and provide additional stabilization and support to the entire brain?
Falx cerebri
tentorium cerebelli
Falx cerebelli
Diaphragma sellae
In the septa what dural venous sinuses are present?
Superior and inferior sagittal sinuses
The straight sinus
sigmoid sinus
transverse sinus
What is cerebrospinal fluid?
Clear, colorless liquid that circulates in the ventricles and subarachnoid space
Bathes the exposed surfaces of the central nervous system and completely surrounds it
What important functions does the cerebospinal fluid perform?
Buoyancy
Protection
Environmental stability
What forms the cerebospinal fluid?
Choroid plexus in each ventricle
How is cerebospinal fluid produced?
By secretion of a fluid from the ependymal cells that originate from the blood plasma
What is the cerebospinal fluid similar to?
Blood plasma but has greater amounts of sodium, hydrogen, and calcium, but less potassium (and calcium??????)
What are brain ventricles?
Cavities or expansions within the brain that are derived from the lumen (opening) of the embryonic neural tube
The brain ventricles are continuous with what?
one another as well as with the central canal of the spinal cord
What are the four ventricles in the brain?
Two lateral ventricles: in the cerebrum, separated by a thin medial partition called the septum pellucidum
Third ventricle: within the diencephalon
Fourth: within the pons and cerebellum
How does each lateral ventricle communicate with the third ventricle?
Through an opening called the intraventricular foramen
CSF is produced by the chorid plexus in what?
the ventricles
CSF flows from the third ventricle through what to get to the fourth ventricle?
mesencephalic aguaduct
Where does excess CSF flow into?
The arachnoid villi, then drains into the dural venous sinuses
What does pressure allow the CSF to do?
Be released into the blood without permitting any venous blood to enter the subarachnoid space
The greater pressure on the CSF in the subarachnoid space assures what?
That CSF moves in the venous sinuses
What disease is called “water on the brain”?
Hydrocephalus
What causes hydrocephalus?
Obstruction in CSF flow that restricts its reabsorption in the venous bloodstream
How is hydrocephalus treated?
Inserting a ventriculoperitoneal shut that drains to the abdominal cavity
Or a ventriculostomy that creates a hole in the floor of the third ventricle that drains into the subarachnoid space
The brain is protected from the general circulation by what?
Blood-brain barrier
What does the blood-brain barrier strictly regulate?
What substances can enter the interstitial fluid of the brain
What does the blood-brain barrier prevent?
exposure of neurons in the brain to drugs, waste products in the blood, and variations in levels of normal substances (ions, hormones) that could adversely affect brain function
What prevents materials from diffusing across the capillary wall in the blood brain barrier?
Tight junctions
What acts as “gatekeepers” that permits materials to pass to the neurons after leaving the capillaries?
Astrocytes
Astrocytes are markedly reduced or missing in what three distinct locations in the CNS?
Choroid plexus, hypothalamus, and pineal gland
Which of the following cranial bones is not paired?
Sphenoid
Which cranial foramen permits passage of the mandibular nerve?
Foramen ovale
The horizontally oriented fold of dura mater that separates the occipital and temporal lobes of the cerebrum from the cerebellum is what?
Tentorium Cerebelli
Falx run vertically
What nerve is in the lateral wall of the cavernous sinus?
Trochlear (CN IV)
Excess CSF is removed fromt he subarachnoid space by what?
Arachnoid granulations
The brain ventricle located in the cerebrum is _____.
Lateral ventricle
