CH 1 Anatomy of the Head and Spine Flashcards
What are the 8 bones of the cranial vault?
- Frontal
- Temporal
- Ethmoid
- Parietal
- Occipital
- Sphenoid
Frontal bone
forms part of the cranial cavity as well as the forehead, the brow ridges and the nasal cavity
Left and Right parietal bones
form much of the superior and lateral portions of the cranium
Occipital bone
forms the posterior and inferior portions of the cranium. many neck muscles attach here, as this is the point of articulation with the neck and cranium.
Sphenoid bone
forms part of the eye orbit and helps to form the floor of the cranium. It is batwing shaped
Ethmoid bone
forms the medial ortions of the orbits and the roof of the nasal cavity.
The cranial bones have a _________ appearance sonographically
highly echogenic appearance
5 major sutures of the skull (image pg 3)
- Coronal
- Frontal (metopic)
- Lambdoidal
- Squamosal
- Sagittal
Coronal Suture
Frontal bone and the Parietal bones form
Frontal Suture (Metopic)
between the 2 Frontal bones
Lambdoidal Suture
formed by Occipital bones and the Parietal bones
Sagittal Suture
along the midline and separates the 2 Parietal bones
Squamosal Suture
runs between the Temporal bone and Parietal
Two abnormalities can occur involving the sutures of the cranial bones
Craniosynostosis and Cloverleaf skull (Kleeblattschadel)
Craniosynostosis
- premature fusion of the cranial sutures
- fusion may be complete or partial
Premature fusion (*Craniosynostosis) of the lambdoidal, coronal and sagittal sutures may lead to
Microcephaly (small head) and secondary Microenchaphy (small brain)
Cloverleaf skull (Kleeblattschadel)
-the premature fusion of the coronal and lambdoidal sutures
- the sagittal suture remains open and allows growth in only 1 direction
- a “trilobed” skull appearance occurs
Children having this type of abnormalilty generally die in infancy and have profound mental retardation
Fontanelles
- the spaces between the bones of an infants skull where the sutures intersect
- generally remain open for 3-18 months
2 fontanelles that are covered by tough membranes
- anterior fontanel, which is the largest and most important
- posterior fontanel
Anterior fontanel (soft spot)
- the junction where the 2 frontal and 2 parietal bones meet at the intersection of the sagittal and coronal sutures
- remains soft until about 18 months and then forms the bregma
Posterior fontanel
- junction of the 2 parietal bones and the occipital bone where the sagittal and lambdoidal sutures meet.
- usually closes first, before the anterior fontanel
- -closes to form the lambda at 2-3 months of age
Mastoid fontanel
- located at the junction of the temporal, parietal and occipital bones
- closes at 1 year
Sphenoid fontanels (anterior lateral)
- located behind and slightly above (~3cm) the zygomatic process
- formed by the frontal bone, the anterior tips of the parietal bone and the temporal bones and the greater wing of the sphenoid bone.
Telencephalon (cerebrum)
Diencephalon (thalamus, hypothalamus, epithalamus)
becomes forebrain
Mesencephalon (colloculi and peduncles)
becomes the midbrain (remains tubular)
Myelencephalon (medulla oblongata)
becomes the hindbrain and spinal cord
4 divisions of the brain
1-Prosencephalon (forebrain) which has 2 additional divisions (telencephalon and diencephalon)
2-Mesencephalon or midbrain
3-Rhombencephalon (hindbrain) contains the metencephalon and myelencephalon
4- spinal cord
4 major regions of the brain
1- Cerebrum
2- Diencephalon
3- Cerebellum
4- Brain stem
Prosencephalon
the most anterior portion of the brain (forebrain). Consists of telenchephalon, striatum, dienchephalon, lateral ventricle and third ventricle.
Diencephalon
enclosed by the cerebral hemispheres and superior to the brain stem.
- includes thalamus, hypothalamus, the optic tracts, optic chiasma, infundibulum, 3rd ventricle, mammillary bodies, posterior pituitary gland and pineal gland.
- part of the prosencephalon (forebrain)
Telencephalon
anterior portion of the brain, rostral (to the front of) to the midbrain.
- consists of cerebral cortex, basal ganglia, corpus striatum and olfactory bulb.
- part of the prosencephalon (forebrain)
Mesencephalon
most rostral portion of the brainstem.
- consists of tectum and tegmentum
- located between forebrain and brainstem.
Rhombencephalon
inferior portion of the brainstem
-comprised of metencephalon, myelencephalon, and reticular formation
Metencephalon
located below the posterior portion of the cerebrum and above the medulla oblongata.
- division of the hindbrain and consists of the pons and cerebellum
- part of rhombencephalon
Pons connected to cerebellum by:
connected by the middle cerebral peduncles
-part of rhombencephalon
Myelencephalon
posterior portion of the brain stem
-composed of the medulla oblongata and contains a portion of the fourth ventricle
Sonographic appearance of parenchyma of the brain
homogenous and of low echogenicity
Gray matter of the brain
- outer portion
- composed of large groups of neurons
White matter of the brain
- deep inside the brain
- composed of the bundles of axons and dendrites covered with fat
Outer gray matter, 1.5 to 5 mm portion of the cerebrum
-is called the cerebral cortex and contains 6 layers
cerebral cortex
a layer of cells covering the surface of the brain
Gyri
Many folds of the cortex
- allows more surface area
- large sulci subdivide each hemisphere
Folds or convolutions on the cerebrum
Gyri
grooves that separate the gyri
Sulci
Cingulate Gyrus
major gyrus of brain
- hypoechoic structure in the medial part of the brain
- partially wraps around the corpus callosum
- superior to hypoechoic corpus callosum
- posterior to echogenic cigulate sulcus
- with callosal marginal artery within it
Precentral gyrus
- primary motor cortex
- located in frontal lobe
Postcentral gyrus
- posterior to the fissure of Rolando, or central sulcus
- main sensory area for the sense of touch
Hippocampal gyri (parahippocampal gyri)
- gray matter region surrounding the hippocampus
- lies in temporal lobe of the brain
- important in memory, especially facial recognition
Sulci
echogenic spider-like fissures separating the hypoechoic gyri
Normal sulcal development occurs
between 32-40 seeks gestation
** NO sulci or gyri are apparent up to 22 weeks of gestation**
Premature infants have more/less sulci than term infants?
Less
-both sulci and gyri are more prominent in full term infants
Absence of sulci in term infant
suggests the presence of cerebral edema or infection
- TORCH infections
Central Sulcus
- main sulcus
- known as sulcus of Rolando
- separates frontal and parietal lobes
- only visible when very deep
- separates primary motor cortex and primary somatosensory cortex
Parieto-Occipital Sulcus
- the first one formed and carries the PCA(posterior cerebral artery)
- may be seen in lateral view running horizontally from the occipital horn of the later vent to back of skull
PCA
Posterior Cerebral artery
Cingulate sulcus
- carries the callosal marginal artery
- superior to the corpus callosum
- coronally cingulate sulci and gyrus seen on either side of falx cerebri
Sulci and fissures both have the appearance
of echogenic lines sonographically
Gyri, or folds have have the appearance
similar to the parenchyma, homogenous and of low echogenicity
Calcarine sulcus
anatomical landmark
- caudal end of the medial brain surface
- primary visual cortex of the brain is concentrated in this area
Fissures
deep grooves in the brain
Interhemispheric fissure
- main fissure
- longitudinal fissure
- appears echogenic midline structure
- separates right and left cerebral lobes
Sylvian fissure
- Lateral fissure or lateral sulcus
- one of the most prominent structures of human brain
- divides frontal and parietal lobe above from the temporal lobe below
- in both hemispheres, but longer in the left
Pulsations from Middle Cerebral Artery (MCA) can be seen pulsating
within the Sylvian fissure
Falx Cerebri
- lies within interhemishperic fissure.
- infold of dura which contains the superior sagittal sinus
- known to calcify with age
- highly echogenic within the interhemispheric fissure
Meninges
- covering of the brain
- 3 coverings, dura mater, arachnoid layer, and pia mater
- encase brain and spinal cord
Epidural space
between the Dura Mater and skull
Subdural space
between the Dura Mater and the Arachnoid mater
Subarachnoid space
between the arachnoid and Pia Mater
Dura Mater
-Latin = “hard mother”
-outer most covering on the CNS (central nervous system)
-toughest and most inflexible
-has 2 layers:
superficial - acutally the skulls inner periosteum
deep- inner layer, the dura mater proper
There are 5 dural reflections, sonographically we image 2 of the dural reflections
- tentorium cerebelli
- falx cerebri
Tentorium cerebelli
- between and separates the cerebellum and brainstem from the occiptal lobes of the cerebrum
- most important dural reflection
- highly echogenic between cerebellum and occitital and posterior portions of the temporal lobes of cerebrum
- divides cranial cavity into supratentorial and subtentorial sections
Falx cerebri
- separates the two hemispheres of the brain
- located in Interhemispheric fissure
- midline, crescent-shaped structure
- divides the suprtentorial compartment into a left and right side
Falx cerebelli
- separates the lobes of the cerebellum and is a very small dural reflection
- generally not imaged on ultrasound
Falx cerebri and Tentorium are the principle dural infoldings where there are a number of venous sinuses draining the brain to the:
Internal jugular veins
Superior sagittal sinus
- largest venous sinus
- runs across the top of the brain and within the falx cerebri
Sinuses of the brain (5)
- superior sagittal sinus
- straight sinus
- inferior sinus
- transverse sinus
arachnoid granulations (or villi) drain into
- the superior sagittal sinus.
The arachnoid granulations are:
small finger-like projections of arachnoid which extend into the dura.
they extend into the venous sinuses of the brain and drain CSF into the blood stream
Thrombosis of the superior sagittal sinus can occur in infants due to:
*severe dehydration
Transverse sinuses include:
left and right
- right transverse sinus is a continuation of the superior sagittal sinus
- left transverse sinus is the continuation of the straight sinus
Thrombosis of any of the dural venous sinuses in the brain may lead to:
white matter ischemia and infarction
Arachnoid Mater
is a “spider web-like” membrane between the Dura Mater and Pia Mater
Arachnoid Mater provides
a secure medium and space through which the CSF can circulate and provides specialized tissue necessary for absorption of the CSF back into the bloodstream.
Mesh-like structure of the arachnoid helps
to anchor the surrounding membranes and keep the subarachnoid space at a constant depth.
Arachnoid granulations or villi:
project into the sinuses of the Dura Mater. These granulations or villi transfer CSF from the ventricles into the bloodstream.
Subarachnoid cisterns
areas within the subarachnoid space where the pia mater and arachnoid membrane are not in close proximity.
-subarachnoid space is between the arachnoid and pia mater
4 Major subarachnoid cisterns:
- cisterna magna
- pontine cistern
- interpeduncular cistern
- quadrigeminal cisterns (superior cistern, cistern of the great cerebral vein, ambient)
- ambient cistern is thin sheet like extension of the quadrigenmal
Quadrigeminal cistern
- below the quadregeminal plate, or tectum of the midbrain.
- junction of the gray and white matter in the embryo
- called- ambient, superior, cistern of great vein (contains vein of Galen)
Dilation of the subarachnoid space between the splenium of the corpus callosum and superior surface of the cerebellum
Quadrigeminal cistern
Quadrigeminal cistern extends bewteen layers of:
tela choroidea of the 3rd ventricle
Quadregeminal cistern can be a frequent site of bleeding
major arteries supplying brain course through these areas.
-subarachnoid or subdural hemorrhages and hematomas
Interpeduncular cistern
- or basal cistern
- wide cavity where the arachnoid extends across the 2 temporal lobes
- encloses the cerebral peduncles and the structures contained in the interpeduncular fossa
The circle of Willis is located in which cistern?
Interpeduncular cistern
biology.org
Pontine cistern is located
between the pons and medulla oblongata
Cistern Magna is located
between the cerebellum and the dorsal surface of the medulla oblongata.
CSF from the 4th ventricle drains into
Cistern Magna (largest)
Pia Mater latin for
“tender mother”
Pia mater
- delicate innermost layer of the meninges
- thin, mesh-like pia mater closely envelopes the entire surface of the brain
- joins with ependyma to form choroid plexus, which helps produce cerebrospinal fluid.
In the spinal cord, Pia Mater attaches
to the Dura Mater by the denticular ligaments through the arachnoid membrane
Tele choroidea
-double fold of pia mater and ependyma which forms the roof of the 3rd ventricle and lower part of the roof of the 4th ventricle.
Cerebrum (cerebral cortex)
-forebrain and is the largest part of the human brain.
Functions of Cerebrum
- motor function
- planning and organization
- touch sensation
- personality development
- interpretation of sensory impulses
- intelligence determination
4 lobes of Cerebrum
- frontal
- parietal
- temporal
- occipital
Frontal lobe
- anterior portion of the cerebral cortex.
- separated from the parietal lobe by the fissure of Rolando posteriorly and from the temporal lobe inferiorly by the Slyvian fissure.
Frontal lobe involved with
decision-making, problem solving and planning
Parietal lobe
- superior to occitpital lobe and posterior to the central sulcus and frontal lobes.
- posterior portion of the Sylvian fissure separates it from the temporal lobe.
Parietal lobe involved with
receives and processes sensory information
Temporal lobes
are anterior to the occipital lobes and lateral to the Sylvian fissure.
Temporal lobes involved with
responsible for emotions, memory and speech
Occipital lobe
- most caudal region of the cerebral cortex
- no natural boundaries on its lateral aspect.
Occipital lobe involved with
Vision and color recognition
Insula
area within the cerebral cortex, deep within the lateral sulcus.
- where the frontal, parietal an dtemporal opercula (lateral portions of the gyri) meet.
- 5th lobe of brain
vascular supply to insula
M3 branch of the Middle Cerebral Artery
Broca’s area
contained within the insula
- controls speech, writing, and reading
Cerebrum is divided into
2 halves
-the right and left hemispheres
The two hemispheres of the cerebrum are connected by the
corpus callosum
-latin for “large body”
Corpus Callosum
- latin for “large body”
bundle of commissural, or interconnecting, fibers that allows the hemispheres to communicate with each other.
*larges white matter structure and connective pathway in the human brain.
Corpus Callosum is divided into 4 parts
- rostrum
- genu
- body
- splenium
Corpus Callosum sonographically
imaged as a midline, hypoechoic structure that forms the superior margin of the ventricles.
Germinal Matrix
- is actually a “fetal” area
- it cannot be visualized as a distinct structure
- contains highly “friable” collection of blood vessels that is most active between 8-28 weeks gestation.
- can damage easily resulting in hemorrhage.
- highly vulnerable to birth injury and blood pressure fluctuations.
Germinal Matrix lies
- anterior/inferior to the caudate nucleus (near the head) and the floor of the lateral ventricle in the sub-ependymal layer of the later ventricle.
- along inferior aspect of lateral ventricles, immediately beneath the ependymal lining of the ventricles and extends from frontal horns backwards into occipital horns.
- *lies in caudothalamic groove/notch at 24 weeks gestation
Germinal Matrix area matures:
- area “matures” and “disappears after 32 weeks gestation.
- reason infants greater than 32 weeks gestation rarely develop sub-ependymal germinal matrix hemorrhages
Caudothalamic Groove
landmark on the floor of the lateral ventricle formed by the white matter of the internal capsule that forms a groove between the head of the caudate nucleus and the thalamus.
Caudothalamic groove in babies less than 32 weeks
the germinal matrix may persist in the area causing the infant to be at risk for sub-ependymal hemorrhage (SEH)
- landmark used to assist in detection of SEH
- best seen in parasagittal plane
Caudothalamic groove sonographically
seen as a notch where the choroid plexus “tucks” in near the area between the caudate nucleus and the thalamus.
Thalamus
- sub-cortical, gray matter, oval or egg-shaped structure on either side of the third ventricle.
- consists of two bodies and tissue that connect the bodies, the “Massa Intermedia” aslo know as the interthalamic adhesion.
Thalamus located
- top of the brainstem and superior to the hypothalamus
- frontal horns of the lateral ventricles are anterior to thalami
- sylvian fissue, with pulsations from the MCA, runs along the lateral margin of the Thalami
Thalamus responsible for
consciousness, sleep, wakefulness, motor control and all senses except olfactory.
Thalami sonographically
hypoechoic, large rounded structures posterior to the lateral ventricles.
Massa Intermedia
lies within the third ventricle and is seen as a highly echogenic dot within the ventricle when the 3rd ventricle is dilated.
- it is absent in 20% of humans
- connects the bodies of the Thalami
Hypothalamus
- located below the thalamus and above the brain stem
- 3rd ventricle is closely related to thalamus and hypothalamus
- size of an almond
Hypothalamus controls
- body temp
- hunger
- thirst
- fatigue
- anger
- circadian cycles (daily 24 hr rhythms)
Optic chiasma
- located at bottom of the brain immediately below the hypothalamus
- near the thalamus and hypothalamus at which portions of each optic nerve cross over.
Amygdala
- almond shaped group of neurons
- located deep within the temporal lobe, medial to hypothalamus
- associated with arousal, emotions, and *hormone secretion
Basal Ganglia
- collection of nuclei
- located deep within the cerebral hemispheres in the telencephalon region of the brain closely related to the lateral ventricles.
- consists of: *caudate nucleus, lenticular nucleus, putamen, globus pallidus, subthalamic nucleus and the substantia nigra
Caudate nucleus
concavity of the lateral angles of each lateral ventricle
-lies below the floor of the frotal horns of the lateral ventricles and superior and anterior to the Thalamus.
Caudate nucleus involved with
learning and memory
Caudate nucleus is composed of
-head, body, tail
Caudate nucleus sonographically
-medium-level echoes below the frontal horns of the lateral ventricles
Cerebellum
“Little brain” in latin, located just above the brainstem, beneath the occipital lobe’s in the posterior fossa of the skull.
It has two hemispheres and it’s covered by cortex.
They are connected by the cerebellar vermis.
Composed of gray matter and a band of white matter that has a “tree – like“ appearance.
Cerebellum controls:
Fine movement coordination, balance, equilibrium and muscle tone.
Cerebellar peduncles:
List the three peduncles and what they connect.
Connect the cerebellum to the Brainstem (midbrain, pons and medulla, spinal cord)
Act as a connection between the midbrain, the thalamic nuclei and the cerebrum. They also contain the ascending and descending nerve tracts which run between the pons and the cerebrum.
Superior cerebellar peduncles =cerebellum to midbrain
Middle cerebellar peduncles = cerebellum to the pons.
Inferior cerebellar peduncles =cerebellum to the spinal cord
Sonographically the cerebellum:
Is seen as a rounded hyperechoic structure in the posterior fossa.
In the sagittal midline view, we are really Imaging the cerebellar vermis.
Cerebellar nerve tracks:
Dorso– spino-cerebellar tract: upper body in impulses
Ventro– spino-cerebellar tract: lower body impulses
Vestibulo– cerebellar tract: inner ear impulses
Reticulo– cerebellar tract: spinal impulses to the brain stem and cortex
Brain stem:
The lower part of the brain, adjoining and structurally continuous with the spinal cord.
It is located at the junction of the cerebrum and spinal column.
Consists of the midbrain, medulla oblongata, and the pons.
The neurological functions that occur in the brainstem are necessary for survival and arousal. The majority of the cranial nerves come from the brain stem.
Pons:
Is a bridge – like structure that connects the cerebrum to the cerebellum and links different parts of the brain.
Serves as a relay station from the medulla to the higher cortical structures of the brain and contains the respiratory center.
Associated with arousal and autonomic functions such as the function of the heart and digestion.
Medulla oblongata:
The most inferior portion of the brain stem and functions primarily as a relay station for the crossing of motor tracts between spinal cord and brain stem.
Also contains the respiratory, vasomotor and cardiac centers as well as many mechanisms for controlling reflex activities such as coughing, gagging, swallowing and vomiting.
Cerebral peduncle’s sonographic appearance:
Hypoechoic, heart-shaped paired structure seen beneath the thalami that fuse with the pons.
Coronally, the pons, peduncles and medulla are hypoechoic structures seen in the midline plane below the thalami, extending into the posterior fossa.
Ventricular system : list the four ventricles in the brain
What are the series of openings that connect the ventricles with each other.
2 lateral ventricles, the third ventricle, and the fourth ventricle.
Foramen of Monroe - Connect the lateral ventricle with the third ventricle
Aqueduct of Sylvius - connect the third and fourth ventricles.
Lateral ventricles:
What are the four segments of the lateral ventricles:
The lateral ventricles are situated in the lower medial portion of each cerebral hemisphere and are separated by thin layer called the septum pellucidum.
The lateral ventricles are the largest CSF filled structures in the brain.
They are use as landmarks to identify other structures in the brain. Most lateral ventricles are asymmetrical normally, especially the occipital horns. The left ventricle is usually larger than the right ventricle.
The entire ventricle system appears larger in preterm neonate. And very immature neonates, the anterior horns are larger than in term infants.
Four segments to the lateral ventricles:
1)The body
And three horns or cornu:
2) the frontal horn
3) occipital horn
4) temporal horn.
Frontal horns of the lateral ventricles
The frontal horns of the lateral ventricles are anterior in the cerebrum.
They are triangular in shape with concave lateral walls.
Coronally, the frontal horns are seen anteriorly as a common shape fluid filled structures.
The foramen of Monro divides the frontal horns anteriorly from the body of the ventricles posteriorly
Temporal and occipital horns of the lateral ventricles :
Lateral ventricle is formed by:
The temporal horns of the lateral ventricles are inferior and occipital horns are in the posterior portion of the cerebrum.
The roof of each lateral ventricle is formed by the corpus callosum and the medial walls are formed by the septum pellucidum.
The lateral walls of the ventricles are formed by the head at the caudate nucleus.
The body of the lateral ventricle:
Extends from the foramen of Monro to the trigone.
They are seen slightly posterior to the frontal horns as rounded anechoic structures anterior to the thalami.
Trigone of the lateral ventricles:
The trigone is a triangle shaped area where the temporal and occipital horns meet the body of the lateral ventricle.
The trigone of the lateral ventricles is seen filled with the echogenic glomus portion of the Choroid plexus.
In the trigon region of the lateral ventricles and anterior to the frontal horn‘s, periventricular area white matter can be seen as a normal periventricular “blush“ or “halo“
This area should be less than or equal to the echogenicity of the normal Choroid plexus but never more echogenic.
Septum pellucidum:
Septum Vergae:
The septum Pellucidum is a thin, triangular, vertical membrane which separates the anterior horns of the lateral ventricles. It extends from the corpus callosum down to the fornix of the cerebrum (fornix -bundles of nerve fibers above the thalamus of the brain)
The cavum septum pellucidum and cavum septum Vergae are a continuous cystic midline structure in the septum pellucidum.
The cavum septum pellucidum is anterior to the foreman of monro and the cavum septum vergae is posterior.
The structures begin to close at six months to station and are usually close at charm.
Third ventricle of the brain
Is a narrow midline space between the right and left thalamus, which communicates with the lateral ventricles through a small opening at the anterior end of the third ventricle called the interventricular foramen or the foramen of Monro.
The third ventricle continues caudally into the cerebral aqueduct or aqueduct of sylvius. This aqueduct opens into the fourth ventricle connecting it to the third ventricle.
The third ventricle has three sac – like recesses:
Pineal recess - is a small recess of the third ventricle which projects into the stalk of the pineal body. The pineal gland is attached to the posterior wall of the third ventricle.
Supraoptic recess - or optic recess, is a small angular recess or diverticulum at the junction of the floor and anterior wall of the third ventricle. It is immediately above the optic chiasm.
Infundibular recess –is a funnel-shaped recess on the floor of the third ventricle. It is below the supra-optic recess.
Fourth ventricle:
Lies within the pons and narrows caudally in the upper part of the medulla, to form the central canal of the spinal cord.
Sonographically the fourth ventricle is too thin to be seen unless it is dilated with CSF.
It lies between the thalami in the coronal plane.
In the sagittal plane, the third and fourth ventricles normally are not seen unless they are dilated.
CSF flows from the fourth ventricle through the:
From the fourth ventricle through the foramen of Magendie (median aperture) into the quadrigeminal cistern and foramen of luschka (lateral aperture) into the Pontine cistern.
Together they drain the fourth ventricle into the subarachnoid space.
CSF:
A clear, colorless fluid that is contained within the system of fluid-filled cavities called ventricles.
CSF flow through the ventricles, exits into the cisterns at the base of the brain, baths the surface of the brain and spinal cord and then is absorbed into the bloodstream.
40% of CSF comes from the choroid plexus, the other 60% is produced by extracellular fluid movement from blood through the brain and into the ventricles ( Rumack)
Choroid plexus:
The choroid is formed by the fusion of the pia mater and the ependyma (lining of the ventricles). The structure is a tuft of small capillary vessels that are fringe – shaped and covered by a very fine layer of ependymal cells.
The choroid plexus is located on the roof of the temporal horn of the lateral ventricle, and the roof of the third and fourth ventricles and the floor of the body of the lateral ventricle.
The bulk of the choroid is contained in atrium of the ventricle and his termed the glomus.
** there is no choroid plexus in the frontal or occipital horn.
** it is normal to see “lumpy“ or “bulky“ choroid in the premature infants.
The current Texas nearly fills the entire lateral ventricle in the first trimester of pregnancy.
Cerebral spinal fluid flows through:
CSF flows from the lateral ventricle to the third ventricle through the intraventricular foramen (Foramen of Munro)
The cerebral aqueduct (aqueduct of sylvius) connects the third ventricle and the fourth ventricle to each other.
CSF them flows into the subarachnoid space through the foramina of Luschka (there are two of these) and the of foramen of Magendie (only one)
Absorption of the CSF into the bloodstream takes place in the superior sagittal sinus through the structures called arachnoid villi.
Arachnoid villi
Absorption of the CSF into the bloodstream takes place in the superior sagittal sinus through the structures called arachnoid villi.
When CSF pressure is greater than the venous pressure, CSF will flow into the bloodstream.
The arachnoid villi act as “one way valves” if the CSF pressure is less than a venous pressure, the arachnoid villi will not let blood pass into the ventricular system.
CSF functions:
- Protection: the CSF protects the brain from damaged by “buffering“ the brain. The CSF acts to cushion the blow to the head and lessen the impact.
- Buoyancy: because the brain is immersed in fluid, the net weight of the brain is reduced from about 1400 g to about 50 g. Pressure at the base of the brain is reduced.
- Excretion of waste products: the one-way flow from the CSF to the blood takes potentially harmful metabolites, drugs and other substances away from the brain.
CSF is also an endocrine medium for the brain. The CSF serves to transport for hormones to other areas of the brain. Hormones released into the CSF can be carried to remote sites of the brain where they may act.
CSF should almost all be absorbed into the bloodstream as it circulates. When the production or absorption of CSF is disturbed, hydrocephalus is the result.
Spinal cord:
A tubular bundle of nerves that begins at the foramen magnum and passes through the vertebral column down to the level of the fourth lumbar vertebrae.
It extends from the medulla oblongata and continues through the conus medullaris near the first or second lumbar vertebrae, terminating in a fibrous extension known as a film terminale. Is it over ovoid-shaped, hypoechoic and is in large in the cervical and lumbar regions.
The spinal cord ends:
Conus medullaris bear the first or second lumbar vertebrae.
The spinal cord does not run through the lumbar vertebrae
Below the level of L1, the vertebral canal is occupied by spinal nerve roots and meninges.
The spinal cord is hypoechoic and the interface created by the nerves are echogenic.
Three meninges that cover the spinal cord:
(Along with a brain) the outer dura mater, the arachnoid mater, and the inner most pia mater.
Cerebrospinal fluid is found in the sub arachnoid space between the pia and the arachnoid.
The cord is stabilized within the dura mater by the connecting denticulate ligaments which extends from the enveloping pia mater laterally between the dorsal and ventral roots.
Dural sac/thecal sac:
Is a membranous sac that encases the spinal cord within the bony structure of the vertebral column. If fuses with the film terminale and contains the CSF the spinal cord floats in. The dural sac ends at the vertebral level of the second sacral vertebrae.
Conus medullaris
The terminal end of the spinal cord. It extends from the medulla oblongata to the level between the first and second lumbar vertebrae.
Film terminalis
Is a strand of connective tissue, pia mater, extending from the conus medullaris to the spinal dural ( thecal) sac that secures the lower end of the spinal cord. It separates from the nerve roots (Cauda Equina) as it extends posteriorly in the canal.
cauda equina
The nerve roots below L1. This is the structure of the terminal end of the spinal cord that contains lumbar and sacral nerves. It has an appearance of a horses tail, thus the term Cauda Equina. The nerve roots pass through the intravertebral foramen of each vertebrae.
Lumbar cistern
An enlargement of the subarachnoid space. It extends from the level of the intravertebral disc between L1 – L2 to S2. This is at the level of termination of the spinal cord with its pia mater covering and the spinal dura mater with its arachnoid lining. The contents of the lumbar cistern include the film terminale, cauda Equina cerebrospinal fluid. It is a site for lumbar punctures.
Descending tracts of the spinal cord:
Corticospinal tract = lower extremities
Spinocerebellar tract = muscle coordination
Spinothalamic tract =Touch, pressure, pain, temperature
There are 31 pairs of spinal nerves:
8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccyx
Anterior median fissure
Long furrow along the midline of the anterior aspect of the spinal cord and the medulla oblongata. it is seen as a central echogenic line which delineates the central end of the anterior median fissure.
Posterior median sulcus
A shallow vertical groove dividing the spinal cord throughout its whole length in the midline posteriorly
