Download - BRAIN STEM EXTERNAL FEATURES
![Page 1: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/1.jpg)
Dr. Ahmed Fathalla Ibrahim
![Page 2: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/2.jpg)
BRAINPROSENCEPHALON (FOREBRAIN):1. TELENCEPHALON: Cerebral hemispheres (cavities:
2 lateral ventricles)2. DIENCEPHALON: thalamus, hypothalamus,
epithalamus & subthalamus (cavity: 3rd ventricle)MESENCEPHALON (MIDBRAIN)• Cavity: cerebral aqueductRHOMBENCEPHALON (HINDBRAIN)1. METENCEPHALON: Pons & cerebellum2. MYELENCEPHALON: Medulla• Cavity: 4th ventricle
![Page 3: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/3.jpg)
BRAIN STEMCOMPONENTS: 1. Midbrain: most rostal part2. Pons3. Medulla oblongata: most caudal partEMBRYOLOGICAL ORIGIN:• Midbrain: arises from mesencephalon• Pons & medulla: arise from
rhombencephalon or hindbrain (together with cerebellum)
![Page 4: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/4.jpg)
BRAIN STEMSITE: • It lies on the basilar part of occipital bone
(clivus)• The midbrain is continuous rostrally with
diencephalon of forebrain• The pons is continous rostrally with
midbrain & caudally with medulla• The medulla is continuous caudally with
spinal cord at the margin of foramen magnum
![Page 5: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/5.jpg)
BRAIN STEM
CONNECTION TO CEREBELLUM:1. Midbrain: by superior cerebellar
peduncle2. Pons: by middle cerebellar peduncle3. Medulla oblongata: by inferior
cerebellar peduncle
![Page 6: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/6.jpg)
BRAIN STEMIMPORTANCE:1. Pathway of tracts between cerebral cortex &
spinal cord2. Site of origin of nuclei of cranial nerves
(from 3rd to 12th)3. Site of emergence of cranial nerves (from 3rd
to 12th)4. Contains groups of nuclei & related fibers
known as reticular formation responsible for: control of level of consciousness, perception of pain, regulation of cardiovascular & respiratory systems
![Page 7: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/7.jpg)
BRAIN STEMVENTRAL SURFACE
![Page 8: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/8.jpg)
BRAIN STEMVENTRAL SURFACE
![Page 9: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/9.jpg)
BRAIN STEMVENTRAL SURFACE
MEDULLA:• Ventral median fissure: 1. It divides the medulla into 2 halves 2. Its lower part is masked by decussation of
pyramidal (corticospinal) fibers• Pyramid: 1. It lies on either side of ventral median
fissure 2. It is an elevation produced by corticospinal
tract
![Page 10: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/10.jpg)
BRAIN STEMVENTRAL SURFACE
MEDULLA:• Olive: 1. It lies lateral to the pyramid & separated from it
by the ventrolateral sulcus2. It is an elevation produced by inferior olivary
nucleusNerves emerging from Medulla (4 nerves):1. Hypoglossal (12th): between pyramid & olive2. Glossopharyngeal (9th), vagus (10th) & cranial
part of accessory (11th): dorsolateral to olive (from above downwards)
![Page 11: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/11.jpg)
BRAIN STEMVENTRAL SURFACE
![Page 12: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/12.jpg)
BRAIN STEMVENTRAL SURFACE
PONS:• Basilar sulcus:1. It divides the pons into 2 halves2. It is occupied by basilar artery• Transverse pontine (pontocerebellar)
fibers:1. Originate from pontine nuclei2. Cross midline & pass through contralateral
middle cerebellar peduncle to enter the opposite cerebellar hemisphere
![Page 13: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/13.jpg)
BRAIN STEMVENTRAL SURFACE
PONS:Nerves emerging from Pons (4 nerves):1. Trigeminal (5th): from the middle of ventrolateral
aspect of pons, as 2 roots: a small medial motor root & a large lateral sensory root
2. Abducent (6th): at junction between pons & pyramid
3. Facial (7th) & vestibulocochlear (8th): at cerebellopontine angle (junction between medulla, pons & cerebellum). Both nerves emerge as 2 roots: from medial to lateral: motor root of 7th , sensory root of 7th , vestibular part of 8th & cochlear part of 8th
![Page 14: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/14.jpg)
BRAIN STEMVENTRAL SURFACE
![Page 15: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/15.jpg)
BRAIN STEMVENTRAL SURFACE
MIDBRAIN:• It is formed of a large column of
descending fibers (crus cerebri or basis pedunculi), on either side
• The 2 crura cerebri are separated by a depression (interpeduncular fossa)
Nerve emerging from Midbrain (one):• Occulomotor (3rd): from medial aspect
of crus cerebri
![Page 16: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/16.jpg)
BRAIN STEMDORSAL SURFACE
![Page 17: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/17.jpg)
BRAIN STEMDORSAL SURFACE
MEDULLA• Divided into 2 portions:1. Caudal 2/3: Closed Medulla:2. Rostral 1/3: Open Medulla
![Page 18: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/18.jpg)
BRAIN STEMDORSAL SURFACE
CLOSED MEDULLA• Contains the rostral continuation of central canal• Composed of:1. Dorsal median sulcus: divdes the closed medulla into 2
halves2. Fasciculus gracilis: on either side of dorsal median
sulcus3. Gracile tubercle: an elevation produced at the upper part
of fasciculus gracilis, marks the site of gracile nucleus4. Fasciculus cuneatus: on either side of fasciculus
gracilis5. Cuneate tubercle: an elevation produced at the upper
part of fasciculus cuneatus, marks the site of cuneate nucleus
![Page 19: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/19.jpg)
BRAIN STEMDORSAL SURFACE
OPEN MEDULLA• Forms the lower part of floor of 4th ventricle• On either side, an inverted V-shaped sulcus
divides the area into 3 parts (from medial to lateral):
1. Hypoglossal triangle: overlies hypoglossal nucleus
2. Vagal triangle: overlies dorsal vagal nucleus
3. Vestibular area: overlies vestibular nuclei
![Page 20: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/20.jpg)
BRAIN STEMDORSAL SURFACE
![Page 21: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/21.jpg)
BRAIN STEMDORSAL SURFACE
PONS• Forms the upper part of floor of 4th ventricle• Separated from the medulla by an imaginary
line passing between the caudal margins of middle cerebellar peduncle
• On either side, a sulcus divides the area into 2 parts (from medial to lateral):
1. Medial eminence: overlies abducent nucleus
2. Vestibular area: overlies vestibular nuclei
![Page 22: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/22.jpg)
BRAIN STEMDORSAL SURFACE
![Page 23: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/23.jpg)
BRAIN STEMDORSAL SURFACE
MIDBRAIN:• Marked by 4 elevations:1. Two superior colliculi: concerned with
visual reflexes2. Two inferior colliculi: forms part of
auditory pathwayNerve emerging from Midbrain (one):• Trochlear (4th): just caudal to inferior
colliculus (The only cranial nerve emerging from dorsal surface of brain stem)
![Page 24: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/24.jpg)
FOURTH VENTRICLE
![Page 25: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/25.jpg)
FOURTH VENTRICLE
![Page 26: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/26.jpg)
FOURTH VENTRICLE
![Page 27: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/27.jpg)
FOURTH VENTRICLE
![Page 28: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/28.jpg)
FOURTH VENTRICLE• Cavity of hindbrain• Diamond (rhomboid) in shape• Triangular in cross section• Communications:1. Rostrally: with cerebral acqueduct
(cavity of midbrain)2. Caudally with central canal (cavity of
spinal cord)• Lateral walls (boundaries): superior &
inferior cerebellar peduncles
![Page 29: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/29.jpg)
FOURTH VENTRICLE• Roof:1. Upper part: superior cerebellar peduncle
& superior medullary velum (a layer of pia & ependyma bridging the space between the 2 peduncles)
2. Middle part: cerebellum3. Lower part: inferior medullary velum (a
layer of pia & ependyma), has a central defect that forms the median aperture of 4th ventricle
![Page 30: BRAIN STEM EXTERNAL FEATURES](https://reader033.vdocuments.site/reader033/viewer/2022061610/56815d12550346895dcb15fb/html5/thumbnails/30.jpg)
FOURTH VENTRICLE• Floor (rhomboid fossa): formed of:1. Whole dorsal surface of pons2. Open medulla (dorsal surface of rostral 1/3
medulla)• Apertures: provide communication
between 4th ventricle & subarachnoid space for circulation of CSF
1. One median aperture (Foramen of Magendi): in the roof of 4th ventricle
2. Two lateral apertures (Foramena of Luschka): at cerebellopontine angle