Brain Stem PDF - Suez Canal University

Suez Canal University Faculty Of Medicine Presented By Dr. Bassma M. Dessouki Lecturer of Anatomy & Embryology Depart. 3 Elevations 1. Pyramid: It is a pyramidal elevation that is formed by the pyramidal tract. 2. Olive: It is an oval-like elevation which is...

Suez Canal University Faculty Of Medicine Presented By Dr. Bassma M. Dessouki Lecturer of Anatomy & Embryology Depart. 3 Elevations 1. Pyramid: It is a pyramidal elevation that is formed by the pyramidal tract. 2. Olive: It is an oval-like elevation which is formed by the inferior olivary nucleus. 3. Inferior Cerebellar Peduncle: It lies postero- lateral to the olive. 3 Sulci & Fissures 1. Anterior Median Fissure: It lies in the midline anterior. 2. Antero-Lateral Sulcus: It lies between pyramid & olive. It gives exit to the rootlets of the hypoglossal nerve (12th ). 3. Postero-lateral sulcus It lies between olive & inferior cerebellar peduncle. It gives exit to the rootlets of glosso- pharyngeal nerve (9th ), vagus nerve (10th ) & cranial accessory nerve (11th ). 1. Gracile tract: It lies adjacent to the posterior sulcus. It ends in gracile tubercle (produced by gracile nucleus). 2. Cuneate tract It lies adjacent to the gracile tract. It ends in cuneate tubercle (produced by cuneate nucleus). 3. Tuberculum cinereum : lies lateral & overlies spinal nucleus of trigeminal nerve. Inferior Fovea : is an inverted V-shaped depression which divides the upper1/2 into 3 areas: 1. Hypoglossal Triangle: lies medially & overlies the hypoglossal nucleus. 2. Vagal Triangle: lies between the 2 limbs & overlies the dorsal nucleus of vagus. 3. Vestibular Area: lies laterally & overlies the vestibular nuclei. 1) Closed Medulla: is the lower part & encloses the central canal. 2) Open Medulla: is the upper part & opens into the 4th ventricle. 1. Basilar Sulcus : it is a longitudinal median sulcus & lodges the basilar artery. 2. Transverse pontine ridges ❑ They lie on each side of the basilar sulcus. ❑ They form the middle cerebellar peduncle (MCP). 3. Trigeminal (5th) nerve: is attached at the junction between basilar part & MCP. 4. Abducent (6th) nerve: is attached to the junction between pyramid & pons. 5. Facial (7th) & vestibulo-cochlear (8th) nerves: are attached to the ponto-medullary junction. 1. Facial Colliculus is formed by abducent nucleus & facial nerve fibres around it. 2. Vestibular area. 3. Superior Fovea : is a depression between facial colliculus & vestibular area. The midbrain is traversed by a canal (cerebral aqueduct of Sylvius ) which divides it into: ❑ Tetcum------------------------posterior. ❑ 2 Cerebral peduncles ------anterior. 1. 4 Colliculli : ▪ 2 Superior colliculli ( reflex centers for vision). ▪ 2 Inferior colliculli ( reflex centers for hearing). 2. Superior Cerebelllar Peduncles 3. Trochlear (4th) nerve: Emerges just below the inferior collicullus. 4. Pretectal region: Lies just above the superior collicullus.  Each cerebral peduncle consists of 3 parts: 1. Crus cerebri 2. Substantia nigra. 3. Tegmentum  Olfactory nerve (1): is formed from 20 filaments that reach the olfactory bulb from below. Optic nerve (2): joins the anterolateral angle of the optic chiasma.  Oculomotor nerve (3): emerges on the medial aspect of the cerebral peduncle. Trochlear nerve (4): The only cranial nerve which is attached to the dorsal surface of the brainstem.  Trigeminal nerve (5): is attached at the base of the MCP. Abducent nerve (6): emerges between the lower border of pons & base the of pyramid. Facial (7) & vestibulocochlear (8) nerves: are attached laterally to the cerebello-pontine angle.  Glossopharyngeal (9), vagus (10) & cranial part of accessory (11) nerves: are attached to the postero-lateral sulcus of the medulla (between olive & inferior cerebellar peduncle). Hypoglossal nerve (12): Is attached to the anterolateral sulcus of the medulla.