BMS301 Anatomy Lecture 11 - Anatomy of Medulla Oblongata PDF

BMS301 Anatomy lecture 11 – Anatomy of medulla oblongata MEDULLA OBLONGATA EXTERNAL FEATURES It is the lowermost part of the brainstem. It continues downwards as the spinal cord. ❖ The Ventral Surface: Three elevations: On each side of the...

BMS301 Anatomy lecture 11 – Anatomy of medulla oblongata MEDULLA OBLONGATA EXTERNAL FEATURES It is the lowermost part of the brainstem. It continues downwards as the spinal cord. ❖ The Ventral Surface: Three elevations: On each side of the midline. From the medial to the lateral: 1) Pyramid: contains the corticospinal tract. 2) Olive: formed by the underlying inferior olivary nucleus. 3) Inferior cerebellar peduncle: it connects the medulla with the cerebellum. Three Fissures: 1) Anterior median sulcus: in the midline. 2) Preolivary fissure: between the pyramid and olive. 3) Postolivary fissure: between the olive and inferior cerebellar peduncle. Exit of the last 4 cranial nerves: Glossopharyngeal, vagus and cranial accessory nerves: in the postolivary fissure. Hypoglossal nerve: exits in the preolivary fissure. ❖ The Dorsal Surface: Lower Part of the Medulla: 3 elevations on each side of the midline: 1. Gracile tubercle (clava): medial and formed by the gracile nucleus. 2. Cuneate tubercle: middle and formed by the cuneate nucleus. 3. Tuberculum cinereum: lateral and formed by the spinal trigeminal nucleus. Upper Part of the Medulla (lower part of the floor of the 4th ventricle) ❖ It is divided into 3 trigones by sulcus limitans (inferior fovea): 1. Hypoglossal trigone: medial, formed by the hypoglossal nucleus. 2. Vagal trigone: middle, formed by the dorsal motor nucleus of the vagus. 3. Vestibular trigone: lateral, formed by the medial & inferior vestibular nuclei. ❖ Area postrema (vomiting center): at the lower angle of the 4th ventricle (obex). ❖ Stria medullaris of the 4th ventricle; band of fibers at the upper end of the medulla. PROF.HAGAR HASHISH-DR A NABAWY 1 BMS301 Anatomy lecture 11 – Anatomy of medulla oblongata PROF.HAGAR HASHISH-DR A NABAWY 2  BMS301 Anatomy lecture 11 – Anatomy of medulla oblongata INTERNAL FEATURES:  NUCLEAR GROUPS IN THE MEDULLA 1. Gracile and cuneate nuclei. 2. Cerebellar relay nuclei. 3. Cranial nerves nuclei. 1. Gracile and Cuneate Nuclei ❖ Receive gracile and cuneate tracts. ❖ second-order neuron for kinesthesia, discriminative touch and sense of vibration from the same side of the body. ❖ Their axons cross to the opposite side in sensory decussation and form medial lemniscus. 2. Cerebellar Relay Nuclei 1) Accessory (lateral) 2) Arcuate nucleus 3) Inferior olivary cuneate nucleus nuclear complex input  Proprioception from  Motor data from the  Motor data from the the upper limb via the cerebral cortex. cerebral cortex. cuneate tract.  Sensory data from the spinal cord via the spinoolivary tract. output  Their axons form  Their axons form  Their axons form cuneocerebellar arcuatocerebellar olivocerebellar tract which reaches fibers which reach the tract which reach cerebellum via ICP. cerebellum via ICP. the cerebellum via ICP. 4) Reticular formation 5) Vestibular nuclei: Input  Motor data from the cerebral  They project vestibulocerebellar cortex. fibers to reach the cerebellum via  Sensory data from the spinal cord. ICP. Output  Their axons form reticulocerebellar tract which reach the cerebellum via ICP. PROF.HAGAR HASHISH-DR A NABAWY 3  BMS301 Anatomy lecture 11 – Anatomy of medulla oblongata 3. CRANIAL NERVE NUCLEI 1) Spinal trigeminal nucleus: sensory ❖ It ascends in the pons and descends in the spinal cord to the level of C3 to become continuous with substantia gelatinosa of Rolandi. ❖ It mediates pain and temperature sensations from the same side of the face. ❖ The axons cross to the opposite side, form the trigeminal lemniscus, which terminates in the VPM nucleus of the thalamus (VPMNT). 2) Nucleus solitarius: sensory a. Upper one-third: receives taste fibers via the: i. Facial nerve (chorda tympani): anterior 2/3 ii. Glossopharyngeal nerve: posterior 1/3 iii. Vagus nerve: epiglottis and the most posterior part of tongue. b. Lower two thirds: receive general visceral sensation. 3) Hypoglossal nucleus: motor nucleus ❖ In the floor of fourth ventricle (hypoglossal trigone). ❖ Supplies all muscles of the tongue except the palatoglossus muscle. 4) Nucleus ambiguus: motor nucleus ❖ Supplies all muscles of the pharynx, all muscles of the larynx and all muscles of the palate except tensor palati muscle. It is divided into three parts: ✓ Upper part: Gives fibers to the glossopharyngeal nerve. ✓ Middle part: Gives fibers to the vagus nerve. ✓ Lower part: Gives fibers to the cranial accessory nerve, which join the vagus nerve. 5.Inferior salivatory nucleus: parasympathetic ❖ Supplies the parotid gland via the glossopharyngeal nerve. 6.Dorsal motor nucleus of the vagus: parasympathetic ❖ In the floor of the fourth ventricle (vagal trigone). ❖ Supplies thoracic and abdominal viscera till the left colic flexure through the vagus nerve. 7.Medial and inferior vestibular nuclei: ❖ In the floor of the fourth ventricle (vestibular trigone). PROF.HAGAR HASHISH-DR A NABAWY 4  BMS301 Anatomy lecture 11 – Anatomy of medulla oblongata ❖ Arterial supply :ASA: Medial zone, Medullary branch of vertebral artery ( intermediate zone), PICA lateral+ICP PROF.HAGAR HASHISH-DR A NABAWY 5  BMS301 Anatomy lecture 11 – Anatomy of medulla oblongata VASCULAR LESIONS OF THE MEDULLA Medial Medullary Syndrome  Cause: Occlusion of the anterior Spinal artery.  Clinical signs: 1. Hypoglossal nerve & nucleus lesion: ❖ LMN paralysis of the same side of the tongue (hemiparalysis). ❖ Deviation of the protruded tongue toward the affected side. 2. affection of the medial lemniscus: ❖ Contralateral loss of kinesthesia, discriminative touch and sense of vibration. 3. affection of the corticospinal tract: ❖ Contralateral hemiplegia. PROF.HAGAR HASHISH-DR A NABAWY 6  BMS301 Anatomy lecture 11 – Anatomy of medulla oblongata Lateral Medullary Syndrome (PICA Syndrome) ❖ Cause: Occlusion of the PICA. ❖ Clinical signs: 1. affection the Spinal trigeminal nucleus: ❖ Loss of pain and temperature from the same side of the face. 2. affection of lateral spinothalamic tract: ❖ Loss of pain and temperature sensation from the opposite side of the body. 3. affection of the nucleus ambiguous: ❖ Ipsilateral paralysis of the muscles of: a) Larynx: hoarseness of voice. b) Pharynx: dysphagia & loss of the pharyngeal gag reflex. c) Palate: nasal regurgitation of food & deviation of the uvula to the normal side. 4. affection of the inferior cerebellar peduncle: ❖ Ipsilateral ataxia. 5. affection of the vestibular nuclei: ❖ Vertigo, nausea, vomiting and nystagmus. 6. affection of the descending sympathetic fibers: ❖ Ipsilateral Horner’s syndrome. PROF.HAGAR HASHISH-DR A NABAWY 7  BMS301 Anatomy lecture 12 – Anatomy of pons 12.Anatomy of pons Prof.Hagar Hashish Professor of Human Anatomy & Embryology Faculty of Medicine Mansoura University Prof.Hagar Hashish  BMS301 Anatomy lecture 11 – Anatomy of medulla oblongata External features A. Ventral surface Basilar groove: contains basilar artery. Transverse pontine fibers. Middle cerebellar peduncle: connect pons with cerebellum. Exit of Trigeminal, abducent, facial and vestibulocochlear nerves. Cerbellopontine angle: lies between cerebellum & pons,medulla. Contains: B. Dorsal surface: Divided by suclus limitans into: 1. Medial eminence: Contain facial colliculus (abducent nucleus and facial fibers) 2. Vestibular area: superior and lateral nuclei. 3. Locus ceruleus: noradrenalin secreting center. 1 Prof.Hagar Hashish  BMS301 Anatomy lecture 11 – Anatomy of medulla oblongata A. Basilar groove B. MCP C. Trigeminal N A C D. Abducent N E.7,8 CN B D E Internal structures of the pons It is formed of anterior part (Basis pontis )and posterior part (tegmentum). 2 Prof.Hagar Hashish  BMS301 Anatomy lecture 11 – Anatomy of medulla oblongata A.Basis pontis: 1. Pyramidal tract fibers 2. Pontine nuclei :part of the cortico-ponto- cerebellar pathway. 3. Transverse pontine fibers pontocerebellar fibers. 4. Fibers of the middle 4 cranial nerves B.Tegmentum of pons: Tracts: 1. Four lemnisci: medial, trigeminal, spinal and lateral lemniscus. 2. Medial longitudinal fasciculus or bundle(MLF): it connects the vestibular nuclei with the motor nuclei that move the eyes. 3. Other tracts: tectospinal, rubrospinal, central tegmental tract and other tracts. Nuclei: 1. Of the middle 4 cranial nerves: V, VI, VII and VIII (vestibular & cochlear nerves). 2. Pontine reticular formation 3 Prof.Hagar Hashish  BMS301 Anatomy lecture 11 – Anatomy of medulla oblongata Lemnisci: Medial lemniscus: for deep sensation and fine touch from the opposite side of the body below the head. Spinal lemniscus: carrying pain, temperature and crude touch from the opposite side of the body below the head Trigeminal lemniscus: carrying pain, temperature and touch and proprioception from the opposite side of the face and scalp. Lateral lemniscus: for auditory sensation Cranial nerve nuclei 1. Nuclei of the trigeminal nerve includes the Trigeminal Motor nucleus and three Sensory nuclei: Spinal trigeminal nucleus, Main sensory nucleus and Mesencephalic nucleus. 2. Nuclei of the facial nerve includes the Facial Motor nucleus. , Superior salivary nucleus: parasympathetic function. Spinal trigeminal nucleus and Solitary tract and nucleus 4 Prof.Hagar Hashish  BMS301 Anatomy lecture 11 – Anatomy of medulla oblongata 3. Abducent nucleus 4. Nuclei of vestibulocochlear nerve includes 4 vestibular nuclei in pons and medulla and 2 cochlear nuclei in pons Arterial supply of pons The Basilar artery gives the following branches which supply the pons: A. pontine branches includes Paramedian, Short circumferential and Long circumferential arteries. B. AICA supplies the lateral part and middle cerebellar peduncle. Medial Pontine syndrome Causes: closure of paramedian branches of basilar artery Affected structures: 1. Corticospinal tract 2. Medial lemniscus 3. Medial longitudinal bundle 4. Abducent nerve and nucleus 5 Prof.Hagar Hashish  BMS301 Anatomy lecture 11 – Anatomy of medulla oblongata Manifestation of medial pontine syndrome: 1. Contralateral hemiplegia 2. Loss of proprioceptive sensation on the opposite side 3. Nystagmus 4. Ipsilateral paralysis of the lateral rectus 6 Prof.Hagar Hashish  BMS301 Anatomy lecture 11 – Anatomy of medulla oblongata Lateral pontine syndrome ▪ Causes: Occlusion of long circumferential branch of pontine artery ▪ Affected structures: 1. Facial nuclei 2. Trigeminal nuclei 3. Vestibulocochlear 4. Spinal lemniscus Clinical manifestation of lateral pontine syndrome Ipsilateral facial palsy Ipsilateral loss of pain and temperature of the face Paralysis of muscle of mastication 7 Prof.Hagar Hashish  BMS301 Anatomy lecture 11 – Anatomy of medulla oblongata Ipsilateral Ataxia Vertigo and nystagmus Contralateral loss of pain and temperature Horner syndrome`s 8 Prof.Hagar Hashish