This lecture talks about a wide number of anatomical things
Lecture objectives
- Identify the bony features of the cranium
- Describe the form and major divisions of the nervous system
- Describe the anatomy of the meninges
- Describe the blood supply and venous drainage of the brain and identify the circle of willis and venous sinuses
- Detail the ventricular system and circulation of CSF
1: The skull.
You have 8 bones that make up the cranium
- Frontal
- 2x Parietal
- 2x Temportal
- Occipital
- Ethmoid
- Sphenoid
These join at the top to form the coronal, sagittal and lambdoid sutures on the top as well as the squamous sutures.
There are 2 intersections of sutures called the bregma and lambdoid sutures.
You have 3 pairs of fossa in the cranium, anterior middle and posterior oriented like cascading pools.
The cranial floor has a number of internal features some of note being the cribriform plate of ethmoid bone, sella turcica of the sphenoid bone and petrous part of the temporal bone
2 The separation of cns and pns
The CNS is the brain and spinal cord. this is where processing is done.
PNS is the nerves incl. cranial. which bring information to and from the CNS
Divisions of the CNS
The brain has 3 main parts, the forebrain (cerebral hemispheres, Dienchaphalon/Interbrain) brainstem (midbrain, pons, medulla) and cerebellum.
Another classification is the forebrain midbrain and hindbrain with the hindbrain being the pons medulla and cerebellum
3: Structure of your brain
Cerebrum
The cerebrum is divided into 5 lobes
- frontal
- temporal
- parietal
- occipital
- Insular
they are all separated by a few anantomical features
- Transverse fissure
- Central sulcus
- Lateral sulcus
- parieto-occipital sulcus
Corpus callosum
This is a commissure which connects the 2 cerebral hemispheres.
it has 4 parts
- rostrum
- genu
- body
- splenium
Diencephalon (distinct form cerebrum)
this is called the interbrain and houses the pineal gland, thalamus, hypothalamus, and pituitary gland
Basal nuclei (part of the cerebrum)
these are subcortical nuclei (Collections of neuron bodies) which are located near the diencephalon.
they consist of the
- caudate nucleus
- globus pallidus
- Putamen
The lenticular nucleus is made of the putamen and the globus pallidus
Straitum
- Caudate nucleus & putamen.
all 3 are the corpus striatum
these are functionally associated with the subthalamic nuclei and substantia nigra
When one refers to the basal ganglia they refer to the corpus striatum, the subthalamic nuclei and the substantia nigra
Function
The function of the basal nuclei are to inhibit undesired movements
the caudate nucleus is the innermost followed by the thalamus and then the lentiform nucleus. There are fibres between the thalamus caudate nucleus and the lentiform nucleus. This is called the internal capsule. There is an external capsule which surrounds the lentiform and then a bit of grey matter called the claustrum. thern there is the extreme capsule.
The internal capsule has a shorter anterior limb, the bend called the genu and a longer posterior limb
4: spinal cord anatomy
This is covered before and it is a lot of the same
31 pairs of nerves
Enlargenings at the level of the arms and legs
2 way flow of info
no periosteal dural layer
meninges
filum terminale and cauda equina as well as the conus medullaris
5: Meninges and csf flow
The meninges are a membrane system which covers the CNS there are 3 layers
- The dura mater is tough and fibrously protects
- The arachnoid mater gives a layer inbetween which allows circulation of csf around the brain and blood vessels to flow.
- The pia mater anchors stuff to brain tissue and is distinct as it is the only one which follows follows sulci in
the dura mater and the arachnoid mater separate to form sinuses where csf flows out. these are found along the superior and inferior margins of the falx cerebri, the margins of the tentorium cerebelli as well as the incisions. there exist arachnoid granulations which serve to allow csf to flow into the sinuses
3 major infolds
- falx cerebri
- tentorium cerebelli
- falx cerebelli.
cisterns are largened subarachnoid spaces ( like ventricles but outside nervous system)
arachnoid villi drain csf into venous sinuses
cavernous sinuses
The middle meningeal arteries supply both the dura as well as the cranium.
6 blood flow in and out of the brain
Csf and blood flow out of the brain in the sinuses where most flows into the superior sagittal sinus or the straight sinus. it then goes to the confluence, transverse and sigmoid sinuses
inferior structures drain into the cavernous sinuses and will drain to the superior or inferior petrosal sinuses. the superior draiing into the transverse, sigmoid, and into the internal jugular and the inferior draiing straight to the IJV
The blood flows to the brain via the internal carotid arteries and the vertebral arteries. the ICAs split into the anterior cerebral arteries and the middle cerebral arteries. the vertebral arteries change into the posterior cerebral arteries.
The ACAs supply the medial front 2/3rds fo the cerebrum, the MCAs supply the lateral 5/6ths and the PCAs supply the median 1/3 and a bit of the lateral occipital lobes
7: Ventricular system
the ventricular system is a series of chambers and channels which allow csf to flow from the brain and through the tissues, and eventually into the subarachnoid layer and out of the brain.
It consists of the lateral ventricles, thirds ventricle and fourth ventricle as well as the cerebral aquaduct. the 4th has 3 openings, the median and 2 lateral openings.