Done by: Arwa AlNaseeb Revised by: Anjod AlMuhareb تنويه: هذا العمل ﻻ يعتبر مصدر رئيسي للمذاكرة وإنما للمرجعة فقط [email protected] OBJECTIVES .List the components of brain stem. .Describe the site of brain stem. .Describe the relations between components of brain stem & their relations to cerebellum. .Describe the external features of both ventral & dorsal surfaces of brain stem. .List cranial nerves emerging from brain stem. .Describe the site of emergence of each cranial nerve. • Development of the brain The brain develops from cranial part of Brainstem neural tube and then the cranial part divides into 3 parts: • The site - Forebrain : Brainstem is located in basilar part of Subdivided into :- occipital bone (clivus). It connects the 1) Two cerebral hemispheres. 2 lateral ventricles cerebrum to the spinal cord. 2) Diencephalon. 3rd ventricle • Parts of brainstem - Midbrain. cerebral aqueduct It composed from above downward: - Hindbrain: 4th ventricle - Midbrain. Subdivided into :- - Pons. 1) Pons. - Medulla oblongata. 2) Cerebellum. Each part is connected to the cerebellum 3) Medulla oblongata by three cerebellar peduncles 1- Superior peduncle to midbrain. 2- Middle to pons. 3- inferior to medulla. VENTRAL SURFACE OF BRAINSTEM midbrain pons Medulla abolongata - Crus cerebri (basis - Basilar sulcus: - Ventral median fissure: pedunculi): -Lodge the basilar artery. -Its lower part is marked by decussation of most of pyramidal fibers (75%-90%). -A large column of descendig - It is continuation of ventral median fibers. fissure of the spinal cord. -Seperated by interpeduncular fossa. - Transvers pontine - Pyramids: (pontocerebellar) fibers: -lateral to ventral fissure. -Originate from pontine nuclei, -Elevation overlies the cross the midline & pass through corticospinal (pyramidal) tract. the contralateral middle cerebellar peduncle to enter the - Olives: opposite cerebellar hemisphere. -Lateral to pyramids. -Elevation overlies the inferior olivary nuclei. control of movement - Anteriolateral sulcus: -Between the pyramids and olives. DORSAL SURFACE OF BRAINSTEM MIDBRAIN MEDULLA ABOLONGATA Has four elevations: Closed medulla: - Open medulla: - Two superior colliculi: -The caudal part. Opens to - the cranial (rostal) part. Concered with the visual reflexes. central canal. opens to 4th ventricle. - Two inferior colliculi: - Dorsal median sulcus. Related to auditory pathway. Fasciculus gracilis: - Inverted V-shaped sulcus: -Lateral to dorsal median sulcus. divides it to three parts -In its upper part, Gracile (medial to lateral): PONS tubercle which produced by 1) Hypoglossal triangle gracile nucleus. Overlies hypoglossal nucleus. 2) Vagal triangle. -Separated from medulla by imaginary Fasciculus cuneatus: Overlies dorsal vagal nucleus. line along inferior border of middle -Lateral to Fasciculus gracilis. 3) Vestibular area. cerebellar peduncles. -In its upper part, Cuneate Overlies vestibular nuclei. tubercle which produced by -Separated into two parts by median cuneate nucleus. sulcus (medial to lateral): -Medial eminence & facial colliculus: overlies abducent nucleus. -Vestibular area: overlies vestibular nuclei. ANTERIOR AND POSTERIOR VIEWS OF BRAINSTEM Cranial nerves and their emergences Midbrain Pons Medulla abolongata 3rd oculomotor nerve: 5th trigeminal nerve: 9th glossopharyngal nerve: -from medial aspect of crus - From the anteriolateral 10th vagus: cerebri. aspect of the pons. -At the level o superior 6th abducent nerve: cranial part of 11th accessory coolliculi. nerve: - From sulcus between pons and pyramids. th 4th trochlear nerve: 7 facial nerve: - All emerge from a sulci dorsolateral to olives. - caudal to inferior colliculus. -From cerebellopontine - The only cranial nerve angle. emerging from dorsal surface - as 2 roots, medial motor of brain stem. and lateral sensory roots. 12th hypoglossal nerve: 8th vestibuloccochlear nerve: - From sulcus between pyramids and olives. - From cerebellopontine angle. - As 2 roots, vestibular and cochlear roots. CRANIAL NERVES Questions for review Q1-The 3rd and 4th cranial nerves from: Q5- 5th trigemenal nerve emerge from: A- medulla. a- cerebellopontine angle. B- pons. B-middle of anteriolateral of pons. C- midbrain. C- at junction of pons and medulla. Q2- Abducent 6th cranial nerve emerge Q6- lateral to ventral median fissure: from: A- olives. A- sulcus between pyramids and olives. B- pyramids. B- sulcus between pons and pyramids. C- fasiculus gracilis. C- at cerebellopontine angle. Q7- facial colliculus overlies: Q3- all cranial nerves emerge from the A- facial nucleus. brainstem except : B- vestibular nuclei. A- 9th and 10th CN. C- abducent nucleus. B- 3rd and 4th CN. Q8- in the cranial part of medulla (open C- 1st and 2nd CN. medulla), it opens into: Q4- all cranial nerves emerge from ventral A- 4th ventricle. surface of brainstem except : B- 3rd ventricle. A- 4th trochlear nerve. C- central canal. B- 5th trigemenal nerve. C- 6th abducent nerve. Q9- from medial to lateral of dorsal surface of medulla: A- fissure, pyramids, olives. B- fasiculus gracilis, fasiculus cuneatus. C- hypoglossal triangle, vagal triangle, vestibular area. Q10- pons develops from: A- forebrain. B- hindbrain. C- midbrain. Answers Q1- c Q6- b Q2- b Q7- c Q3- c Q8- a Q4- a Q9- b Q5- b Q10- b .