CNS Part 2 M.o , pons , cerebullm Flashcards
explain the Brain ( the part we are interested about its M.O pons cerebellum
-The brain or Encephalon is the part of CNS thats incloud all the higher centres
—Embryogenesis:
1- at the 3 vesicle stage : Rhomboncepholn
2- at the 5- stage vesicle : it will be maylencpholon and metencepholn
- external structure:
1-from sup the cerebral hemisphere and its belong to the Forebrain
2-from inf surface there is Rhemoboncephlon is divided into
2-1 maylencepholn : keeps origin to M.o
2-2 metencephlon : consist of Pons and cerebellum
— Cavities :
the human CNS is tubular so each part has its own cavity which consist of the cerebral-fluid , the cavity of the Rhomboncepholn its the 4th ventrecal
Explain the Medulla oblongata general feature
-Medulla oblongata or bulbuls cerebri its prolongation of spinal cord
—Embroyginisis:
1- at the 3 vesicle stage : Rhomboncepholn
2- at the 5 vesicle stage :
maylencephlon
— topography: its located in Claivus ,
inf. continue to spinal cord , sup continue to Pons , and between Pons and M.o we can see ( Ponta medullary junction )
explain the external structure of M.o
— its kinda similar to spinal cord
——Ventral surface
1- midline : ant fissure
2-sidelines : Antr.latral sulcus which is root of hypoglossal nerve pass through
3- elevations :
3-1 pyramid : which formed by cortico spinal tract
3-2 olives : more laterally which is separated from pyramids by ant, lateral sulcus
4- Pyramidal dicossation : some fibres from pyramid pass to opposite side in mid line to form dicossaion
——Dorsal surface :
1- Post Lateral sulcus : Root of
1-1 accessory n 1-2 vagus n
1-3 glossopharyngeal n pass through
NB! post latral sulcus dont correspond to the post latral sulcus in spinal cord here is more anteriorly
explain the Rhomboid fossa
— Dorsal surface of the M.o : at the same time its the floor of the 4th ventrecal and the floor of the 4th ventrecal is the floor of the rhomboid fossa
— structure of the Rhomboid fossa
1- mid line : post median sulcus
2- laterally from the Post median sulcus there is ( sulucs lemitens ) and between them there is median Emenins
3- medullary striae : its boundary between M.o and Pons
—— Triangles :
1- upper triangle : open part
2- lower triangle : close part , which there is - cuneate tubercle and - gracile tubercle thats why this part is enlarged because the nucleus of cuneate and gracile is projected inside , then these tubercles forming :
( inf, cerebra peduncles )
explain the internal structure of Medulla oblongata ( gray matter )
- its loses its butterfly shape , and its form 4 nuclear groups
—-1st group : paired gracile and cuneate - axons of proper receptors , neurones coms from ganglion ( 1st ordary N ) which located in the spinal cord these axons synapses with neurons of this nuclei ( 2nd ordary N) the axons of these neurons goes to ventral median and dicossate and from medial lemicecus goes upward to the thalamus ( 3rd ordray N ) and form Bulbothalmus tract
- small protion of these fibers goes to cerebral via inf cerebral peduncles and form bulbocerebral tract
—-2nd group : olivary nuclei
- axons of :
1- mid brain ( red nucleus) downward
2- cerebral cortex ( dontate nucleus) : goes medially
to the medulla oblongata and synapses with olivary nuclei and form
1- olivary cerebral tract via inf.ce.ped.
2- olivary spinal tract
- function: regulate the movement
—3rd group :reticular formation nuclei
-they are scatters among reticular formation nerve fibres
1- a small nuclei : works as intermediate neurones
2- large nuclei : works as centers of such a complex reflex for vital functions like :
- coughing , sneezing , heart beat , respiration
—4th group : nuclei of 9-12 cranial nerves
- they are mainly situated in dorsal medullary surface facing the forth ventricle
12- hyboglossal nuclei
- nuclei : post.median sulcus
-root : Ant.lateral sulcus
-hyboglossal trigon : under medullary striae
11-accessory nuclei
- nuclei : post. latral sulcus
-root : lateral feniculus , its prolongation passes to spinal cord till reach c5-c6 segment
10- vagus 9-glosspharngyeal nucleus :
-common motor nuclei : Ambiguous near to median sulcus
-common sensory nucleus: nuclei of solivatorytract near to rostal vegetative nuclei
-vagal trigon : medially from hypoglossla trigon
explain the internal structure of medulla oblongata ( white matter )
1— its very similar to that in spinal cord : , because all the tract which comes to spinal cord and leave the spinal cord they pass through medulla oblongata
2– in the medulla oblongata during the embryogenesis: the post part is separated from each other and movies laterally , and the both sensory tract and sensory nuclei they will be laterally and the motor will be medially
-Ascending tract ( sensory )
1-bulbothalmic tract
2-bulbocerebal tract
3-Ant.spinocerbrall tract
4-post.spinocerebrall tract
5-spinothlamic tract
—Descending ( efferent motor )
1-corticospinal tract : forming pyramids
2-lateral.cortcospinal tract
3-ant.corticospinal tract
—
4-tectospinal tract
5-conduction tract
—
6-reticular spinal tract
7-vestibular spinal tract
8-rubrospinal tract
—Nuclio thalamic tract: transmit general impulses from head and nick rigion and conducting information from inter receptor
—Nuclei cerebrall tract : transmit unconsion prop receptor impulses from head
Explain the External structure of Pons
—Embryogenesis:
1- at the 3stage vesicle : Rhomboncepholn
2- at the 5stage vesicle :
Metencephlon together with cerebellum
— The pons looks like a bridge between 2 ( middle cerebral peduncles ) they are formed by white matter and they connect Pons with cerebellum
— External structure of Pons
—-ventral—
1- Pontine ventral surface : directed to Clavius ,
2- Dorsal surface: directed to cerbellum
3- in the meddle there is a Basilar sulcus which contain the basilar artery
4- in ventral surface : there is fibres which move transversally they called ( pontine cerebral fibres ) which start from pontine nuclei in the gray matter
these fibres goes along meddle cerebral peduncles : pontocerebral fibres enter cerebellum and form ponto cerebral tract which regulate our movements
5- at the boundary between Pons and meddle cerebral peduncle there is a place of the ( trigmenal nerve 5th pair )
—-dorsal—-
1- at the dorsal surface of pons : forms the upper triangle of the rhomboid fossa and it has medial sulcus and ( limitan sulcus laterally ) and between then there is medial eminince and inferiorly to the eminence there is fascial colliculus which is formed by the fascial nerve
2- superiorly to the suluca limitans there is creinal fovea and inferiorly there is coudal fovea
3-the inferior margin of medial Eminince : there is the hypoglossla trigon
and inferiorly from it there is vagal trigon where is the dorsal vagal nuclei is located
4- in the inf,latral part : there is a vestibular cochlear and facial nerves where nucleus of vestibular and facial are projected ( they are both situated at the level of pontain angle )
explain the internal structure of Pons ?
— internal structure of Pons
- we can divide the Pons into 3 parts :
1- basilar part , ventral ( inf in pic )
2- tegmental part , superior or dorsal part
3- Trapezoid body between them
1– Basilar Part :
-gray matter :forms numerous of pontien nuclei
-neuron fibrous from the brain form ( Corticopontien tract ) and axon form this tract synapses with pontien nuclei and goes to cerebellum via meddle cerebral peduncles
-white matter : found by fibres running longuatidanlly and transversally , the axon of Corticopontien tract pass transversally and form pontocerebral tract
2-Tagmental part : is represented as the floor of the 3rd ventrecal
- and its consist of 5-8 cranial nuclei:
-5th (trigmenal nerve ): represented by -spinal nuclei: near to trigemnal trigon in post. horn of first 4 cervical segments
-sensory pontien nuclei
-mescenphlic nuclei : work as intermediate neurons
-6th ( abducens nuclei): located near to post median sulcus
-7th (facial nuclei) : located ventrolateral to abducens and goes around it and form elevation called facial colliculs and then pass ant. to leave the pons as facial nerve
-8th (Vestebualrcochlear )lies laterally from the elevation , and its axons run to decussate and form Trapezoid body
3- Trapezoid body : its the structure that is responsible of hearing , it is connected with fibers of vestibular cochlear nerve the 8th pair , these fibres comes to trapezoid body from sinuses , then they decussate and form ( medial meniscus )
- medial menisucs : is formed by blubothlamic tract
-lateral meniscus : formed by audtry fibres
—— tracts in the pons white matter
- Sensory :
1- spinocerebral tract
2- spinothalmic tract
3- thalamic nuclei
4- bulbothalmic tract
-motor :
1-rebrospinal tract
2- vestibularspinal tract
3- reticularspinal tract
4-Tecto-spinal tract
explain the external structure of the cerebellum
- it develops from metencephlon
-located in post cranial fossa and has rhomboid shape
— external structure
1- it consist of hemispheres : are distinguished right and left , the pons and medulla oblongata is located inferiorly to the cerebellum
2— surface: it has 2 surfaces , superior is concave and inferior surface which consist of Vermis which located in depression , and also there is a horizontal fissure between the superior and inferior surfaces , (the surfaces is not smooth there is numerous small sulcus) they are separating the whole cerebellum into 4 leafs
and the largest sluci seprate the cerebellum and vermis into lobules
3- lobuls of hemispheres corrspond to lobules of vermis bcs the cerebellum its like integration center so many tract and fibers come and analysed that why it should be connected to the other part of brain stem by peduncles which formed by white matter only so they are conducting tracts :
-sup ped : connect with midbrain
-meddle ped: coneect with pons
-inf ped : connect with M.o
4-the most ancient parts of the cerebellum: its flocculus
what is the vermis of cerebellum?
1-Lingula
2-central lobule
3-culmen
4-follum
—-
5-tuber
6-pyramid
7-uvula
8-Nodule
what is the lobules of cerebellum?
-Sup:
1-quadrangular plate
2-sup semilunar lobul
-inf:
1-inf semilunar lobul
2-garcile lobule
3-Biventral lobule
4-cerebral tonsil
explain the internal structure of cerebellum
- its consist of gray matter and white matter
- gray matter : lying superficially and forming cerebral cortex and they are 3 layers :
1-molecular layer
2-Purkinji layer
3- the granular layer
-white matter : lying under gray matter and form medullary body - in median section : it has a leaf shape called ( tree of life , Arbor veta )
—- nucleus in cerebellum:
1- cerebral nuclei: its located in the white matter
2-Fistigial nucleus : in each side of midline of vermis
3- globose nuclei: latrally to fastigial
4-Emboliform nuclei: more latrally to fastigial
5- dontate nuclei : inferiorly the most
what is the tracts passing through inferior peduncles?
—Inferior cerebral peduncles:all of them sensory except
1-post.spinecerebral tract
7-nuclocerebral tract
2-bulbocerebral tract
3-olivocerebral tract
4-vestibularcererbal tract
5-cerebrovestebular tract
6-cerebeloolvary tract ( association)
8-cereberalretcular tract
what is the tracts passing through meddle peduncles?
-only : Pontocerebral tract ( association )
what is the tracts passing through superior peduncles?
1-Ant.spine cerebral tract (afferent )
2-Dentatorubral tract ( association)
3-Dentatothamalic ( association )
