Brain stem It is stalk like in shape
Brain stem
It is stalk like in shape and connects the narrow spinal cord with the expanded forebrain Brainstem 4 th ventricle cerebellum Brainstem spinal cord 2
Thalamus occupies the posterior cranial fossa of the skull Cerebral aqueduct 4 th ventricle midbrain cerebellum Pons medulla oblongata Central canal 3
Anterior surface of the brainstem Midbrain Pons Pontomedullary junction Medulla oblongata 4
Optic chiasma Optic tract Interpeduncular fossa Cerebral peduncle Transverse pontine fibres Basis pontine Midbrain Pons Basilar sulcus Posterolateral slcus Olive Anterolateral sulcus Pyramid anterior median fissure decussation of the pyramids Medulla oblongata Anterior surface 5
Exit of the Cranial nerves from the anterior surface 4 3 5 87 6 9 12 10 11 6
External features of the anterior surface of Medulla oblongata - It present the following features from the median plane to the lateral: 1 - Anterior median fissure; Its lower part is interrupted by pyramidal (motor) decussation. 2 - Pyramid; an elevation on each side of the anterior median fissure. - The pyramid is formed by the pyramidal tract (corticospinal tract). 3 - Anterolateral sulcus; It is the groove on the lateral side of the pyramid. 4 - Olive; it is the oval elevation lateral to the pyramid. - It is formed by the bulging of the olivary complex nuclei. 5 - Posterolateral sulcus; lateral to the olive. Cranial nerves related to the anterior surface: 1 - Anterolateral sulcus; gives exit for the rootless of hypoglossal nerve (12 th). 2 - Posterolateral sulcus; gives exist to the glossopharyngeal (9 th), vagus (10 th) and cranial part of accessory (11 th) nerves arranged from above downwards. 7
External features of the anterior surface of Pons 1 - Basilar sulcus; a longitudinal groove in the middle line for the basilar artery. 2 - Basis pontine: raised ridge on each side of the basilar sulcus. - It is formed by fibers of the pyramidal tract. 3 - Transverse pontine fibres; on each side. - It is produced by the corticopontocerebellar fibers that collect to form the middle cerebellar peduncle. Cranial nerves related to the anterior surface: 1 - Trigeminal nerve: arise by a large sensory root and small motor root from the lateral part of the anterior surface at its junction with the middle cerebellar peduncle. 2 - Pontomedullary groove; gives exist to the abducent (6 th), facial (7 th) and vestibulocochlear (8 th) nerves arranged from medial to lateral. External features of the anterior surface of Midbrain (Mesencephalon) 1 - Cerebral Peduncles: descend from the cerebral hemispheres. - Occulomotor nerve (3 rd) exits from the medial aspect of each cerebral peduncle. 8
Interpeduncular fossa A 2 1 B - The trochlear nerve (IV) is the only cranial nerve which emerges from the back of the brain stem. C (Cerebral peduncle) D 4 3 9
Tuber cinerium infundibulum 2 Mammillary bodies pons posterior perforated substance Trochlear nerve structures inside oculomotor nerve Interpeduncular fossa 10
Interpeduncular Fossa * Shape and site; this is a diamond shaped depression at the base of the brain between the two cerebral peduncles. * Boundaries: 1 - Anteriorly, Optic chiasma. 2 - Posteriorly, Upper border of the pons. 3 - Anterolaterally, Optic tracts. 4 - Posterolaterally, Cerebral peduncles. * Contents: 1 - Tuber cinereum and Infundibulum. 2 - 2 Mammillary bodies. 3 - Posterior perforated substances (perforated by the central branches of the posterior cerebral artery). 4 - The oculomotor (3 rd) nerve exits through the medial sides of the cerebral peduncles. 11
Posterior surface of brainstem Medial eminence Superior colliculus Facial colliculus Superior fovea Inferior colliculus S Cerebellar peduncles M Stria medullaris Vestibular area I Inferior fovea Vagal area Spinal tract of trigeminal N Cuneate tract & nucleus Gracile tract & nucleus Posterior median fissure Hypoglossal area 12
External features of posterior surface of Medulla oblongata A- The posterior surface of the closed lower half medulla; - It presents the following features from medial to lateral 1 - Posterior median fissure (sulcus). 2 - Gracile tract and nucleus; lateral to posterior median sulcus. 3 - Cuneate tract and nucleus; lateral to the gracile tract. The cuneate tubercle is a higher level than the gracile. 4 - Spinal tract (nucleus) of trigeminal nerve; lateral to the 13 cuneate tract.
External features of posterior surface of Medulla oblongata B- Posterior surface of the opened upper half medulla; - It forms the lower part of the floor of the 4 th ventricle, and it is separated from the pons by a stria medullaries. - It presents the following features: 1 - A median longitudinal fissure. 2 - An inverted V shaped depression called the inferior fovea. 3 - Hypoglossal area (trigone); between the median sulcus and the inferior fovea. It overlies the hypoglossal nucleus. 4 - Vagal area (trigone); between the two limbs of inferior fovea overlies the dorsal nucleus of the vagus. 5 - Vestibular area (trigone); lies lateral to the inferior fovea. - It overlies inferior vestibular nucleus. 14
External features of posterior surface of Pons (tegmentum) - It forms the upper part of the floor of the fourth ventricle; 1 - Median longitudinal sulcus; in the middle line. 2 - Medial eminence: a longitudinal elevation on each side of the median sulcus, produced by the abducent nucleus. 3 - Facial colliculus; a round swelling on the lower part of the medial eminence. - It is produced by the facial nerve which encircles the abducent nucleus. 4 - Superior fovea, a groove lateral to the facial colliculus. 5 - Vestibular area, lateral to the superior fovea. It overlies the vestibular nuclei. 15
External features of posterior surface of Midbrain (Tectum) - Four Knob-like elevations called colliculi - The 4 colliculi are separated by a cruciform (cruciate) sulcus. a- 2 superior colliculi; which are the centers of visual reflex. - Each of them is connected to the lateral geniculate body (L. G. B) by superior brachium. b- 2 inferior colliculi; which are the centers of auditory reflex. - Each of them is connected to the medial geniculate body (M. G. B) by inferior brachium. - The trochlear nerve (IV), the only cranial nerve which emerges from the back of the brain stem. 16
Blood supply of the brainstem Circle of Wills Midbrain Basilar artery Pons Posterior inferior cerebellar artery Medulla oblongata Vertebral artery 17
th 4 ventricle
19
The fourth ventricle Definition Is the cavity of hind brain It is situated between pons and superior half of medulla oblongata (anterior) and cerebellum (posterior) 4 th ventricle cerebellum Pons Medulla Position of The fourth ventricle 20
Shape of The fourth ventricle Posteriorly, it is rhomboidal (diamond) in shape Laterally, the fourth ventricle is a tentshaped cavity 21
3 rd ventricle cerebral aqueduct 4 th ventricle Central canal of the medulla oblongata The fourth ventricle communication 22
Median sulcus Upper Pontine part Floor The diamond -shaped floor Transverse stria medullaries Lower Medullary part 23
The posterior surface of the superior half of the medulla oblongata Transverse medullary stria Hypoglossal trigone Vagal trigone Lower Medullary part Floor Pons Inferior fovea Inverted Vshaped Vestibular trigone 24
Floor Upper Pontine part Superior cerebellar peduncle Vestibular area Superior fovea Medial eminence cerebellum Facial colliculus 25
Floor (Rhomboidal fossa) - Median sulcus divides floor into right and left halves, extends from superior to inferior angle. - Stria medullaris divides the floor into upper part (pontine) and lower part (medullary). A- The medullary (lower) part presents on each side of the median sulcus, - An inverted V shaped groove called inferior fovea. 1 - Hypoglossal area (trigone) medial to inferior fovea. 2 - Vagal area (trigone) between 2 limbs of inferior fovea. 3 - Vestibular area (trigone) lateral to inferior fovea. B- The pontine (Upper) part presents on each side of the median sulcus, 1 - Medial eminence: a longitudinal elevation on each side of the median sulcus, 2 - Facial colliculus; a round swelling on the lower part of the medial eminence. 3 - Superior fovea, a groove lateral to the facial colliculus. 4 - Vestibular area, lateral to superior fovea. It overlies superior, medial and lateral vestibular nuclei. 26
Borders & angles & openings Superior cerebellar peduncles Inf cerebellar peduncle Spinal tract of trigeminal N Cuneate nucleus Gracile nucleus Connection (Openings) of the fourth ventricle, 1 - Superior angle is continuous with 3 rd ventricle through cerebral aqueduct of Sylvius. 2 - Inferior angle is continuous with the central canal of the closed medulla. 3 - 3 openings in lower part of roof which transmit cerebrospinal fluid to the subarachnoid space. a- One Median opening (foramen of Magendie) in lower part of roof. b- Two Lateral openings (foramina of Luschka) one in each lateral recess. 8
• ** Boundaries of the 4 th ventricle • - It has 4 angles, 4 borders, floor, and roof. Angles, • 1 - Superior angle is continuous with the 3 rd ventricle through cerebral aqueduct of Sylvius. • 2 - Inferior angle is continuous with the central canal of the closed medulla. • 3 - 2 lateral angles extend laterally to form the lateral recess on each side. Borders, it has 4 borders: • 1 - Upper lateral border: is formed by superior cerebellar peduncle on each side. • 2 - Lower lateral border: is formed by gracile and cuneate tubercles, spinal tract of trigeminal nerve and inferior cerebellar peduncle on each side. 28
Boundaries of 4 th ventricle Spinal tract of trigeminal 29
Roof Tent-shaped roof projects into the White core of cerebellum Cerebellum Superior medullary velum Lingula of cerebellum Choroid plexus Inferior vermis Inferior medullary velum 30
LS choroid plexuses Tela choroidea 31
Roof: 1 - The upper part is formed by the superior medullary velum: thin sheet of white matter between the 2 superior cerebellar peduncles. - It is pierced by the trochlear nerve. 2 - The lower part is formed by the inferior medullary velum: thin sheet of white matter between the two inferior cerebellar peduncles. - It is invaginated by the tela choroida. 3 - Middle part by lingula and inferior vermes of the cerebellum Tela choroidea and Choroid plexus of the fourth ventricle; - Tela choroidea is a double layer of pia matter that invaginated by the choroid plexus into the cavity of the ventricle. - Choroid plexuses- They are branches from the posterior inferior cerebellar arteries. - They secret C. S. F. into the cavity of the 4 th ventricle. 32
Medulla Oblongata Cranial Nerve Nuclei 9, 10, 11, 12 The most important part of the brain, It regulates the breathing, heart and blood vessels, digestion and swallowing
Motor nuclei 1 - Nucleus Ambiguus (S. V. E = pharyngeal arch) - Upper part → g. Iossopharyngeal nerve → to stylopharyngeus muscle. - Middle part → vagus nerve. - Lower part → cranial part of accessory nerve. N. B; The vagus and accessory form pharyngeal plexus supply all muscles of pharynx except stylopharyngeus muscle, all muscles of larynx and palate except tensor palati. 2 - Hypoglossal Nucleus (G. S. E) → to the hypoglossal nerve → all muscles of the tongue except palatoglossus (supplied by the pharyngeal plexus). 34
Parasympathetic nuclei (G. V. E) 1 - Inferior salivary nucleus - It gives parasympathetic → glossopharyngeal nerve → relay in the otic ganglia → to the parotid gland. 2 - Dorsal Nucleus of Vagus a- It is a parasympathetic fibers to the smooth muscles and glands of the digestive, respiratory tracts and cardiac muscle. b- It receives general sensation from the mucous membrane of the digestive, respiratory tract and heart. 35
Sensory nuclei 1 - Solitary Nucleus (S. V. A): It receives taste sensation from: a- Anterior 2/3 of the tongue through facial nerve (chorda tympani) and oral surface of the soft palate (greater petrosal nerve). b- Posterior 1/3 of the tongue through glossopharyngeal nerve (lingual nerve). c- Root of the tongue through vagus nerve (internal laryngeal nerve). 2 - Spinal nucleus of trigeminal nerve (general sensation) (G. S. A): It receives pain, temperature and general sensations from the head and face (5 th, 9 th & 10 th). 3 - Inferior Vestibular Nuclei (S. S. A): It receives fibres of the vestibular organs of the inner ear. 36
Conclusion of Cranial nerves nuclei in medulla 1 -Motor nuclei inferior vestibular nucleus 2 -parasympathetic nuclei 3 -Sensory nuclei 37
NON CRANIAL NERVE NUCLEI
internal arcuate fibers sensory decussation 39
Non-cranial nuclei • Gracile and CUneate Nuclei: 2 nd order neuron for the conscious proprioceptive sensation and fine touch. - Gracile nucleus receives from the lower limb and lower 1/2 of the trunk while cuneate receives from the Upper limb and upper 1/2 of the trunk. • Axons of the gracile and cuneate nuclei ( internal arcuate fibers) → Sensory decussation → medial lemniscus → end into the posterolateral ventral nucleus (PLVN) of the thalamus. • Accessory Cuneate Nucleus (proprioceptive sensation) sensation of position and movement going to cerebellum • Arcuate nucleus is the expansion of the pontine nuclei 40
Connection of inferior olivary complex Afferent fibers the inferior olivary nuclei The cells ofreach the inferior olivary nucleus sendfrom the spinal cordfibers (the spino-olivary tracts)toand from olivocerebellar across the midline enter the higher centers through central tegmental tract cerebellum through the inferior cerebellar peduncle. 41
4 Its efferents fibers form (venteral external arcuate Arcuate nucleus is a small nucleus situated in fibers) which enter the cerebellum through the front of corticospinal fibers in pyramid. inferior cerebellar peduncle. 42
• Olivary complex Nuclei (large corrugated sac with its opening directed medially): - It forms an elevation on the front of the medulla called the olive. - Its function is associated with voluntary muscle movements. ** Afferent from 1 - Spinal cord (Spino-olivary tract). 2 - Red nucleus 3 - Globus pallidus 4 - Reticular formation ** Efferent; Olivo-cerebellar the fibers cross to the opposite side to the cerebellar cortex through the inferior cerebellar peduncle. 43
The pyramidal decussation pyramid of Medulla oblongata Motor decussation Uncrossed fibers Lateral corticospinal tract Anterior corticospinal tract (80 -85%) cross the midline (15 -20%) don't cross the midline 44
• Motor (pyramidal) decussation - In the lower part of medulla, most of the fibers of corticospinal tract (80 -85%) decussate the midline forming Lateral cortico-spinal tract descends in the lateral column of the white matter to relay in the anterior horn cells (AHC) of the spinal cord • Uncrossed pyramidal tract • 15 -20% does not cross midline forming Ventral (Anterior) corticospinal tract, descends in anterior white column of white matter. Its fibers cross midline to relay in anterior horn cells of the opposite side. N. B; Some of fibers (1%) remain in the same side without crossing to end around the medial motor nuclei (nuclei that supply the muscles of the trunk and respiration). So, these muscles receive fibers from both sides. This explains absence of respiratory and trunk paralysis in cases of hemiplegia.
** Lesions of Medulla Oblongata (Wallenberg's syndrome) 1 - Medial Medullary syndrome a- Pyramidal tract → contralateral hemiplegia U. M. N. L (paralysis of the muscles on the opposite 1/2 of the body). b- Medial lemniscus → loss of proprioceptive sensation and fine touch on the opposite side of the body. c- Hypoglossal nerve → paralysis of the muscles of tongue on the same side (The tongue deviated to the side of paralysis). 2 - Lateral Medullary syndrom a- Lateral spinothalamic tract → loss of pain and temperature sensations on the opposite side of the body. b- Spinal tract of trigeminal nerve→ loss of pain and temperature sensations on the same side of the face. c- Nucleus ambigus → paralysis of muscles of the pharynx, larynx and palate on the same side. d- Inferior cerebellar peduncle → cerebellar manifestations on the same side. 46
** Lesions of Medulla Oblongata (Wallenberg's syndrome) 1 - Medial Medullary syndrome a- Pyramidal tract → contralateral hemiplegia U. M. N. L (paralysis of the muscles on the opposite 1/2 of the body). b- Medial lemniscus → loss of proprioceptive sensation and fine touch on the opposite side of the body. c- Hypoglossal nerve → paralysis of the muscles of tongue on the same side (The tongue deviated to the side of paralysis). 2 - Lateral Medullary syndrom a- Lateral spinothalamic tract → loss of pain and temperature sensations on the opposite side of the body. b- Spinal tract of trigeminal nerve→ loss of pain and temperature sensations on the same side of the face. c- Nucleus ambigus → paralysis of muscles of the pharynx, larynx and palate on the same side. d- Inferior cerebellar peduncle → cerebellar manifestations on the same side. 47
Pons Cranial Nerve Nuclei 5 th, 6 th, 7 th, 8 th 5
§ Nuclei of the trigeminal nerve 1 - Motor nucleus (S. V. E); for the muscles developed from the 1 st pharyngeal arch. 2 - Main sensory nucleus (G. S. A); - It receives sensory fibers of crude touch from the face and scalp. 3 - Spinal tract (nucleus) of trigeminal (G. S. A); - It lies in the lower part of the pons and descends along the whole length of the medulla oblongata to be continuous with SGR in the spinal cord. - It receives pain and temperature sensations from the scalp and face. N. B: Sensation from lower part of face to the upper part of the nucleus and vice versa. - Sensation from medial part of face to lateral part of the nucleus and vice versa. 4 - Mesencephalic nucleus (G. S. A): extends up to the midbrain -It receives proprioceptive sensations from the scalp, face and muscles of mastication. N. B; the only first order neuron that present inside the central nervous system. 49
• Abducent Nucleus (G. S. E) - It is encircled by the facial nerve (looping around it) forming facial colliculus. - It is the motor nerve for the lateral rectus muscle. LR 6 (SO 4)3 50
• Facial Nuclei 1 - Motor nucleus (S. V. E); muscles developed from the 2 nd pharyngeal arch. • Upper part of motor nucleus receives fibres from both sides of corticobulbar tracts Lower part receives fibers from opposite side of corticobulbar tract. 2 - Parasympathetic nuclei (G. V. E) a- Superior Salivary Nucleus; (SSS) → facial nerve → chorda tympani → lingual nerve → submandibular ganglion → submandibular & sublingual glands b- Special lacrimatory nucleus (SSL) → facial nerve → greater petrosal nerve → sphenopalatine ganglion → lacrimal, nasal, palatine and pharyngeal glands. 3 - Solitary nucleus (SVA), receives taste sensation. 51
Upper part Like Orbicularis oculi Lower part Motor nucleus of facial nerve Like Buccinator 52
• Vestibulo-cochlear nerve a- Vestibular Nuclei (S. S. A) superior, medial and lateral - They receive equilibrium from inner ear along vestibular nerve - They connected to cerebellum by efferent and afferent fibers. b- Cochlear Nuclei (S. S. A) dorsal and ventral - They receive hearing impulses from the cochlea of the inner ear through the cochlear nerve. - The fibres cross to the opposite side as auditory decussation (trapezoid body) and ascend as lateral leminscus to the medial geniculate body of the thalamus. 53
• Non-cranial nerve nuclei 1 - Pontine nuclei: Cortico-ponto-cerebellar tract • Cerebral cortex (same side) ----- Pontine nuclei ----cross to the opposite side ----- middle cerebellar peduncle ------ to the cerebellum 2 - Reticular formation nuclei. 54
Midbrain Cranial Nerve Nuclei 5 th, 6 th, 7 th, 8 th 5
• Nuclei of occulomotor nerve: a- Motor nucleus (G. S. E) for all the extra ocular muscles except lateral rectus and superior oblique. b- Parasympathetic (Edinger-westphal nucleus) (G. V. E) → inferior division of oculomotor nerve → nerve to inferior oblique → ciliary ganglia → to ciliary muscle and constrictor pupillae muscle. § Motor nucleus of the trochlear nerve (G. S. E): - It supplies the superior oblique muscle of the eyeball. • Mesencephalic nucleus of trigeminal nerve. - It receives the proprioceptive sensation from the muscle of mastication. 56
NON CRANIAL NERVE NUCLEI
Tegmentum Red nucleus The tegmentum is continuous across the median plane substantia nigra crus cerebri basis pedunculi 58
• Non-cranial nerve nuclei - Substantia Nigra (extrapyramidal center) - It contains melanin pigment, hence its name nigra (black). - is concerned with muscle tone - It is connected to the corpus striatum (basal nuclei) cerebral cortex, and hypothalamus, - Degeneration of the substantia nigra leading to absence of dopamine secretion causing Parkinson's disease 59
Connection of red nucleus 3 Afferent fibers 60
Connection of red nucleus 3 Efferent fibers 61
Red nucleus: - It is so called because it has a pink color in fresh sections due to the presence of iron pigment. - It is an important station of extrapyramidal system through it the cerebellum controls activity of spinal cord and medulla oblongata. • Afferent I- From the cerebral cortex (same side). 2 - From the cerebellum (dentate nucleus) (opposite side). 3 - Superior colliculus (same side). * Efferent SIR 1 - to the spinal cord (opposite side). 2 - to the inferior olivary nucleus (same side). 3 - to the reticular formation (opposite side). . 62
3 - Tectal nuclei that lie in the tectum (posterior surface). a- Superior Colliculus (Visual) * Afferent : 1 - From the optic tract. 2 - From visual area of the cerebral cortex. b- Inferior Colliculus (Auditory) * Afferent: 1 - From the cochlear nerve. 2 - From auditory area of the cerebral cortex. * Efferent of superior and inferior colliculus to: - Tecto-bulbar: Ocular motor nuclei (3 rd, 4 th, 6 th) responsible for movement of the eyes in relation to the visual and auditory stimuli. - Tecto-spinal: upper segments of the spinal cord responsible for the movement of the head in relation to the visual and auditory stimuli (Spinal part of accessory nerve). 4 - Pretectal Nucleus for light reflex. * Afferent from the optic tract. * Efferent to the Edinger Westphal nucleus of oculomotor of both sides. 63
Th ank Qu you est ion s I/Azzam - 2004
- Slides: 65