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