The Brain Flashcards
What are the primary brain vesicles?
Prosencephalon (forebrain)
Mesencephalon
Rhombencephalon (hindbrain)
What germinal later does the CNS derive from?
Ectoderm
What does the prosencephalon develop into?
Telencephalon
Diencephalon
What does the mesencephalon (1°) develop into?
Mesencephalon (psych!)
What does the rhombencephalon develop into?
Metencephalon
Myelencephalon
What does the telecephalon develop into?
Cerebrum and lateral vesicles
What does the diencephalon develop into?
Thalamus, hypothalamus, Epithalamus and third ventricle
What does the mesencephalon (2°) develop into?
Midbrain
Aqueduct of midbrain (cerebral aqueduct)
What does the metencephalon develop into?
Pons
Cerebellum
Upper 4th ventricle
What does the Myelencephalon develop into?
Medulla oblongata
Lower 4th ventricle
What does the brain stem contain?
Continuous with spinal cord
Contains medulla oblongata, pins and midbrain
Largest part of brain
Cerebrum
Three layers of cranial meninges
Dura mater
Arachnoid mater
Pia mater
Two layers of dura mater
Periosteal (external)
Meningeal (internal)
The two layers of dura mater are fused except for where
Dural venous sinus
Dural venous sinus
Endothelial lined venous channel
Drain blood from brain and deliver to internal jugular veins
What are the three extensions of dura mater?
Falx cerebri
Falx cerebelli
Tentorium cerebelli
Falx cerebri
Extension of dura mater
Separates two hemispheres of the cerebrum
Falx cerebelli
Extension of dura mater
Separates two hemisphere if cerebellum
Tentorium cerebelli
Extension of dura mater
Separates cerebrum from cerebellum
Blood enters the brain via
Internal carotid and vertebral arteries
Blood exits brain via:
Dural venous sinuses which drain into internal jugular veins.
Brain makes up what percent of total body weight but uses what percent of O2 and glucose?
2 and 20
What cells make up the blood brain barrier?
Astrocytes + endothelial cells connected by tight junctions.
What is the blood brain barrier
Semi-permeable covering encasing capillaries of the brain.
Doesn’t cover the roof of third and fourth ventricle, posterior pituitary gland, pineal gland, the median eminence of the hypothalamus and the area postrema.
What is the blood brain barrier permeable to?
H2O-soluble substances (ie glucose) by active transport
Creatine, urea, ions cross slowly.
Fat soluble substances :
O2, CO2, alcohol, anesthetic agents cross passively
Not proteins, bacteria
Cerebral spinal fluid
Protect CNS from chemical and physical injury
Mainly water, plus O2, glucose and other stuff (glucose, proteins, lactic acid, cations, anions, WBC)
Where does CSF circulate?
Subarachnoid space
Average total volume of CSF?
80-150 ml
What cavities are filled with CSF?
2 lateral ventricles (on each side of cerebrum) Third ventricles (midline) Fourth ventricles (between brain stem and cerebellum)
Septum pellucidum
Thin triangular membrane separating anterior horns of left and right ventricles.
The CSF from 4th ventricle flows into
Subarachnoid space and central canal
Functions of CSF
- Mechanical protection
- Homeostatic function (pH affects pulmonary ventilation and cerebral blood flow)
- Circulation
Where is most of the CSF made?
Chroroid plexuses
Ependymal cells
Special glial cells in choroid plexuses that filter substances from blood and secrete them into CSF
Choroid plexuses
Networks of blood capillaries in walls of ventricles. Location of CSF production.
Blood-CSF barrier
More tight junctions between ependymal cells.
Protect CNS from harmful blood borne substances.
Interventricular foramina
Opening between lateral and 3rd ventricles
Cerebral aqueduct
Connect 3rd and 4th ventricle
CSF Circulation
Lateral ventricle –[interventricular foramina]–> Third ventricle –[cerebral aquaduct]–> Fourth ventricle –[lateral and median apertures] –> subarachnoid space & central canal –> (absorbed into) Arachnoid Villi of dural venous sinuses –> venous blood –> heart and lungs –> arterial blood –> Choroid plexuses of the lateral, third and fourth ventricles
Arachnoid granulation
Cluster of arachnoid villi
Arachnoid villi
Fingerlike extensions of the arachnoid mater that projects into the dural venous sinuses (esp. the superiors sagittal sinus)
Where reabsorption of CSF into blood stream occurs.
