Medulla oblongata

medulla oblongata

lower part of brainstem

location: in skull on clivus

length: 2.5 cm

2 surfaces: ventral + dorsal

upwards:

- bound by pons

downwards:

- at level of foramen magnum

- continues into spinal cord

ventral surface

5 grooves:

- fissura mediana anterior

- sulcus anterolateralis dexter et sinister

- sulcus posterolateralis dexter et sinister

structures:

- pyramis medullae oblongatae

- decussatio pyramidum

- oliva

- n. hypoglossus (XII)

- n. accessorius (XI)

- n. vagus (X)

- n. glossopharyngeus (IX)

pyramis medullae oblongatae

location: on both sides of fissura mediana anterior

contains: tractus corticospinalis

decussatio pyramidum

loaction: at lower end of pyramid

contains: crossed fibres of tractus corticospinalis

oliva

elevation

location: sulcus anterolateralis <--> sulcus posterolateralis

contains: nucleus olivaris

n. hypoglossus

XIIth cranial nerve

emerges: sulcus anterolateralis

cranial nerves (vagus group)

emerge: in sulcus posterolateralis (next to oliva)

nervus glossopharyngeus (IX)

nervus vagus (X)

nervus accessorius (XI)

posterior surface

upper part:

- larger

- takes part in formation of fossa rhomboidea

laterally from upper part:

- pedunculus cerebellaris inferior

- to cerebellum

midline of lower part:

- sulcus medianus posterior

next to it:

- fasciuculus gracilis with tuberculum gracile

- where gray matter = nucleus gracilis

next to it:

- fasciculus cuneatus

- terminates with tuberculum cuneatum

- where gray matter = nucleus cuneatus

internal features of medulla oblongata

- substantia grisea

- substantia alba

medulla oblongata - substantia grisea

1. nuclei craniales
2. nucleus gracilis
3. nucleus cuneatus
4. nuclei olivares
5. formatio reticularis

medulla oblongata - substantia grisea - nuclei craniales

nuclei of cranial nerves VIII-XII

--> in fossa rhomboidea

medulla oblongata - substantia grisea - nucleus gracilis

2nd neuron of epicritic sensibility pathway

--> in tuberculum gracile

medulla oblongata - substantia grisea - nucleus cuneatus

2nd neuron of epicritic senibility pathway

--> in tuberculum cuneatum

medulla oblongata - substantia grisea - nuclei olivares

--> in oliva

start of:

- tractus olivospinalis

- tractus olivocerebellaris

medulla oblongata - substantia grisea - formatio reticularis

diffuse network of cells + fibres

location:

- spinal cord + brainstem

- between pedunculi cerebellares inferiores

medial part: contains raphe nuclei

--> vast impact on CNS

connects to: cerebellum, thalamus, hypothalamus, cortex

function: influence on level of consciousness + other vital functions of body

(e.g. sleeping, walking, eating, urination, defecation, sexual activity)

medulla oblongata - substantia alba

- tractus ascendentes
- tractus descendentes

medulla oblongata - substantia alba - tractus ascendentes

conscious (--> impulses to cortex)

- fasciculus gracilis

(fibrae arcuatae externae + internae)

- fasciculus cuneatus

(fibrae arcuatae externae + internae)

- tractus spinothalamicus lateralis

- tractus spinothalamicus anterior

unconscious (--> impluses to cerebellum)

- tractus spinocerebellaris posterior

- tractus spinocerebellaris anterior

fasciculus gracilis and fasciculus cuneatus

substantia alba, tractus ascendentes

formed by: axons of pseudounipolar neurons of spinal ganglion

synapse with: 2nd neurons at nucleus gracilis or nucleus cuneatus

takes part in formation of: epicritic sensibility pathway

- info about position of body parts + their movements

axons form two groups of fibres:

a) fibrae arcuatae externae

- through pedunculi cerebellares inferiores --> cerebellum

b) fibrae arcuatae internae

- cross (decussatio lemnisci medialis --> ascends as lemniscus medialis)

fibrae arcuatae - picture

decussatio lemnisci medialis - picture

lemniscus medialis

ascends to: thalamus (diencephalon)

- to synapse with 3rd neurons

function: epicritic sensibility pathway

tractus spinothalamicus lateralis

substantia alba, tractus ascendentes

ascends to: thalamus (diencephalon)

- for synapsing

- as lemniscus spinalis

function: pain + temperature pathway

tractus spinothalamicus anterior

substantia alba, tractus ascendentes

ascends to: thalamus (diencephalon)

- for synapsing

- as lemniscus spinalis

function: touch pathway

lemniscus spinalis - picture

tractus spinocerebellaris posterior

substantia alba, tractus ascendentes

ascends to: cerebellum

- via pendunculus cerebellaris inferior

function: unconscious proprioreceptive / deep sensation pathway

tractus spinocerebellaris anterior

substantia alba, tractus ascendentes

ascends to: cerebellum

- passes through pons and mesencephalon

- via pendunculus cerebellaris superior

function: unconscious proprioreception / deep sensation pathway

tractus spinothalamicus, tractus spinocerebellaris - picture

medulla oblongata - tractus descendentes

pyramidal system (for voluntary movements)

- tractus corticospinalis

- tractus corticonuclearis

extrapyramidal system (for unvoluntary movements)

- tractus vestibulospinalis

- tractus vestibulocerebellaris

- tractus olivospinalis

- tractus olivocerebellaris

- tractus rubrospinalis

- tractus tectospinalis

- fasciculus longitudinalis medialis

- tractus reticulospinalis

tractus corticospinalis

substantia alba, tractus descendentes

formed by: axons of pyramidal cells of cortex

- belongs to pyramidal system

descend to: motor nuclei (spinal cord)

- passes through pyramis

function: for voluntary control of skeletal muscles for the trunk + limbs

majority of fibres 80%:

crossed (decussatio pyramidum)

20% of fibres:

uncrossed

--> continue in anterior funiculus (spinal cord)

--> as tractus corticospinalis anterior

tractus corticonuclearis

substantia alba, tractus descendentes

formed by: axons of pyramidal cells of cortex

- belongs to pyramidal system

synapses with: motor nuclei of cranial nerves (IX, X, XI, XII)

function: for voluntary control of skeletal muscles of head + neck

tractus corticospinalis, tractus corticonuclearis - picture

tractus vestibulospinalis

substantia alba, tractus descendentes

formed by: axons of nuclei vestibulares (fossa rhomboidea)

descends to: motor nuclei cornu anterioris (spinal cord)

function: balance pathway

- coordination of unvoluntary movements concerned with balance + posture

tractus vestibulocerebellaris

substantia alba, tractus descendentes

formed by: axons of nuclei vestibulares (fossa rhomboidea)

descends to: gray matter of cerebellum

function: takes part in balance pathway

- coordination of unvoluntary movements concerned with balance + posture

tractus olivospinalis

substantia alba, tractus descendentes

formed by: axons of nuclei olivares

descends to: motor nuclei cornu anterioris (spinal cord)

function: balance pathway

- coordination of movements concerning balance + posture

tractus olivocerebellaris

substantia alba, tractus descendentes

formed by: axon of nuclei olivares

descends to: cortex cerebelli

- via pedunculus cerebellaris inferior

function: takes part in balance regulation

tractus vestibulospinalis, tractus reticulospinalis - picture

fasciculus longitudinalis medialis, tractus tectospinalis, tractus rubrospinalis - pictures