Mid Term Revision

Neuroanatomy block-Anatomy

Editing file

This file was done by:

● Abdulrahman Shadid ● Ateen Almutairi

Boys team: Girls team :

● Abdullah Basamh All team members ● Alwaleed Alsaleh ● Salman Alagla Special thanks to May babaeer ● Abdulrahman Al-Bedaiwi Lecture 1: Organization of The Nervous System (1/1)

Organizations of the nervous system Structural organization Functional organization

(Central nervous system) (Peripheral nervous system) -brain & (Sensory-afferent) (Motor-efferent) -nerve, ganglion & receptors -occupies the dorsal cavity Consists of nerve fibers Consists of nerve fibers

-integrating/command center that convey impulses that convey impulses

from receptors located from the CNS to the 1)Ganglion: group of neurons 1)Nucleus: group of neurons in various parts of the effector muscles, organs outside CNS within CNS body to the CNS. and glands. 2)Nerve: group of nerve fibers 2)Tract: group of nerve fibers outside CNS within CNS

-Functions of the nervous system: 1) collection of sensory input 2) integration 3) motor output -Nervous tissue: 1) : cell bodies/processes of neuron/neuroglia/B.V 2) : same as grey matter BUT without cell bodies

Autonomic nervous system Neurons that detect changes and control the activity of the viscera. Its components are present in both the central and peripheral nervous systems.

Sympathetic Parasympathetic (Thoracolumbar outflow) (Craniosacral outflow)

Divisions are generally have antagonistic effects on the structures that they innervate E.g. Sympathetic increases the heart rate, while the parasympathetic decreases the heart rate. Parts of The Brain

Cerebral hemispheres Tissue of cerebral Cerebellum hemispheres

The largest part of the brain. The outer layer is the gray matter or cortex. Cerebellum has 2 cerebellar They have elevations, called gyri that Deeper is located the white matter or hemispheres with convoluted surface. are separated by depressions called medulla, composed of bundles of nerves and fibers carrying impulses to and from the It has an outer cortex of gray matter sulci. cortex. and an inner region of white matter. Each hemisphere is divided into 4 lobes Basal nuclei are gray matter that are It provides precise coordination for named according to the bone above. located deep within the white matter to help body movements and helps maintain Lobes are separated by deeper grooves the motor cortex in regulation of voluntary equilibrium. called fissures or sulci. motor activities.

Brainstem Diencephalon The diencephalon is located between It is connected to the cerebellum the 2 cerebral hemispheres and is with 3 paired peduncles superior, linked to them and to the brainstem. middle and inferior. The major structures of the The brainstem has three parts: diencephalon are: 1. Midbrain. 1. Thalamus 2. Pons. 2. Hypothalamus 3. Medulla oblongata. 3. Subthalamus 4. Epithalamus.

Brain ventricles

● ● Brain is bathed by the cerebrospinal fluid ● There are three connective tissue CSF is constantly produced by the choroid (CSF). membranes invest the brain and plexuses inside the ventricle. ● ● Inside the brain, there are 4 ventricles filled the spinal cord, from outward to Inside the brain, CSF flows from the lateral with CSF. inward: ventricles to the 3rd and 4th ventricles ● ● The 4 ventricles are: 1. Dura matter. From the 4th ventricle, part of the CSF flows - 2 lateral ventricles: One in each 2. Arachnoid matter. down in the of the spinal cord. ● hemispheres. 3. Pia matter. Most of the CSF drains from the 4th - 3rd ventricle: in the Diencephalon. ventricle to distribute in the subarachnoid - 4th ventricle: between Pons, Medulla space around the brain and returns to the oblongata & Cerebellum. dural venous sinuses through the Cerebral aqueduct: arachnoid villi. connects the 3rd to the 4th ventricle. 2 Lecture 2: Anatomy of the Spinal Cord (1/2)

Spinal Cord Shape & Pathway

● It is elongated, cylindrical, thickness of the little Function & Protection finger,suspended in the vertebral canal Features ● Continuous above with the medulla oblongata. extends ● The primary function of spinal ● Gives rise to 31 pairs of spinal from foramen magnum to 2nd lumbar (L1-L2) vertebra. cord is nerves: (In children it extends to L3). a transmission of neural signals between 8 Cervical, 12 Thoracic, In adults, its Length is approximately 45 cm the brain and the (PNS) then to the rest of 5 Lumbar, 5 Sacral, the body by: 1 Coccygeal. ● The tapered inferior end forms , which 1. Sensory. is connected to the coccyx by a non-neuronal cord called 2. Motor. ● Spinal cord has two . 3. Local reflexes. enlargements: 1. : supplies ● The bundle of spinal nerves extending inferiorly from ● Protected by vertebrae and upper limbs. lumbosacral enlargement and conus medullaris surrounded by the meninges and 2. Lumbosacral enlargement: surround the filum terminale and form cerebrospinal fluid (CSF) supplies lower limbs

Cross section of the Spinal cord Central canal

A cerebrospinal-filled space that runs longitudinally through the entire length of the spinal cord. The spinal cord is Commissure Lined by ependymal (ciliated columnar Incompletely divided epithelium) into two equal parts: Grey commissure: Continuous with the ventricular system of Anteriorly by a short, Composed of grey A Transverse bridge of grey matter connecting the anterior the brain shallow median fissure. matter in the and posterior gray horns on each side Superiorly opens into the 4th ventricle Posteriorly by a deep centre surrounded Is pierced by the central canal that divides it into anterior Inferiorly in the conus medullaris, it narrow septum, the by white matter and posterior part. expands into the fusiform terminal posterior median supported by White commissure: ventricle and terminates below at the root septum. neuroglia. Lies ventral to the gray commissure. of filum terminale. Mainly contains decussating nerve fibers.

Grey matter

● The arrangement of grey matter resembles the shape of the letter H, ● having two posterior, two anterior and two lateral horns/columns. ● Consists of nerve cell bodies and their processes, neuroglia, and blood vessels ● The nerve cells are multipolar and are of three main categories: 1. Sensory neurons (Tract cells): receive impulses from the periphery of the body and whose axons constitute the ascending fasciculi of the white matter, are located in the Dorsal horns. 2. Lower motor neurons: transmit impulses to the skeletal muscles, are located in the ventral horns (similar neurons in the lateral horn are the preganglionic neurons of the autonomic system). 3. (connector neurons): linking sensory and motor neurons, at the same or different levels, which form spinal reflex arcs.

❏ Arrangement of the nerve cells group: ❏ Dorsal horn ❏ ventral horn ❏ lateral horn : Small column composed of small neurons extend from: • T1 to L2-3 segments, give rise to preganglionic sympathetic fibers • S2-4 segments, give rise to preganglionic parasympathetic fibers Intermediolateral Nucleus (IMN): Located in the intermediate column and lateral horn. relays sensory information from visceral to the brain, and autonomic signals from the brain to the visceral organs. (Lamine VII). Groups of cells in the Dorsal Horn

Name Location Function and features

Marginal at the tip of the dorsal horn. Important for relaying pain and temperature sensation to the brain. zone (MZ) (Laminae I)

Substantia at the apex of the posterior Dorsal root fibers relaying pain, temperature, and light touch sensation to the Gelatinosa horn brain. (SG): (Laminae II). Composed of large neurons and Extends throughout the length of spinal cord

Nucleus In the neck of the dorsal horn Dorsal root fibers concerned with half of crude touch, concerned with senses of Proprius (anterior to substantia position & movement. gelatinosa) .(Laminae IV). Composed of large neurons and Extends throughout the length of spinal cord

Nucleus at the base of dorsal horn dorsal root fibers concerned with information from muscle spindles and Dorsalis (Laminae VII). tendon organs (relays unconscious proprioceptive information to the brain) Composed mostly of large neurons and Extends from C8 to L3-4 segments

Visceral lateral to nucleus dorsalis • Afferents: Visceral afferents Afferent Rexed • Composed mostly of medium size neurons • Extends from T1 to L3 segments Nucleus (Lamina VII)

3 Lecture 2: Anatomy of the Spinal Cord (2/2)

1. The comprise a system of ten layers of grey matter (I-X) 2. These layers are called the Laminae of Rexed, that are numbered consecutively by Roman numerals, starting from the tip of (Rexed Laminae) the dorsal horn and moving ventrally into the ventral horn. 3. Cells of the same type are clustered into groups, which occur in long columns. 4. In transverse section, these columns appear as layers, especially within the dorsal horn. Groups of cells in the Ventral Horn

The ventral horns contain: 1. Motor neurons, also called lower motor neurons. and has two type: ● Large multipolar cells ➢ Numerous ➢ Axons pass out in the ventral roots of spinal nerves as alpha efferents ➢ Innervate extrafusal muscle fibers ● Smaller multipolar cells ➢ Less numerous ➢ Axons pass out in the ventral roots of spinal nerves as gamma efferents ➢ Innervate intrafusal muscle fibers of neuromuscular spindles *Both alpha and gamma motor neurons are under the influence of descending pathways (upper motor neurons) from brain Motor neurons are organized in 3 groups: a. Medial: present in most segments and Innervate muscles of Neck and Trunk (including intercostal and abdominal muscles). b. Central: smallest, present in some segments: cervical (phrenic C3-5, spinal accessory C1-6 or C1-5 as on other lecture) and lumbosacral (L2-S1). c. Lateral: present in cervical and lumbosacral segments, innervates muscles of the Limbs *Lateral motor neurons and medial motor neurons: Composed of motor neurons that innervate visceral and skeletal muscles. (Laminae VIII & IX) 2. Interneurons, the (Renshaw cells), whose branched axons form inhibitory synaptic junctions on motor neurons

White matter Regional differences

The nerve fibers are Tracts are The amount of white matter increases Consists of mixture arranged as bundles, often named Depending on in a caudal-to-cranial direction of nerve fibers, Arranged in running vertically according to their functions, because fibers are added to ascending neuroglia and blood columns/funic through the cord. A their points of the spinal tracts tracts and fibers leave descending vessels. White color uli; anterior, group of axons that origin and are divided into tracts. The gray matter is in increased is due to high posterior and share a common destination, ascending tracts volume in cervical & lumbosacral proportion of lateral origin, termination e.g. and descending enlargements for innervation of upper myelinated nerve and function form a spinothalamic, tract. & lower limbs. The lateral horn is fibers tract or fasciculus corticospinal. characteristics of thoracic and upper lumbar segments. Spinal nerves

innervate Deep muscles of the trunk responsible for movements of the vertebral ● 31 pairs of spinal nerves. 8 pair cervical, 12 pair thoracic, 5 pair Dorsal Rami: lumbar, 5 pair sacral, 1 pair coccygeal column and Skin near the midline of the back. ● First pair exit vertebral column between skull and atlas, last four pair exit via the sacral foramina and others exit through In the thoracic region form Intercostal nerves that innervate the intercostal intervertebral foramina. muscles and the skin over the thorax ● Each spinal nerve arises as rootlets which then combine to form Ventral Rami: Remaining ventral rami form five plexuses: dorsal purely sensory & ventral purely motor Roots. ● C1 - C4 = Cervical plexus. ,C5 - T1 = Brachial plexus, L1 - L4 = Lumbar ● Two roots merge laterally and form the spinal nerve. plexus. , L4 - S4 = Sacral plexus., S5 & Co = Coccygeal plexus. ● Dorsal root has a ganglion (dorsal root/sensory ganglion) that contains the cell bodies of the sensory neurons. ● Each spinal nerve then divides into a MIXED smaller dorsal and Communicatin Is connection between spinal nerves and sympathetic chain of ganglia a larger ventral Ramus. g Rami

Dermatome

● Dermatome is a segment of skin supplied by one spinal nerve.(segmental spinal nerve) ● Each of these spinal nerves relay sensation from a particular region of skin to the brain. a. The nerves from the upper cervical spine supply the skin of the neck. b. C5 to T1 nerves supply the arms. c. T2 to L2 nerves supply the chest and abdomen. d. L3 to S1 nerves supply the skin of the legs. e. S1-Co nerves go to the groin. ● Cutaneous areas supplied by adjacent spinal nerves overlap. There is therefore little or no sensory loss after interruption of a single spinal nerve or dorsal root ● Testing of dermatomes is part of the neurological examination looking for sensation changes within a specific dermatome that may help in determining the pathological disc level.

Spinal Meninges ● From outward to inward: Arachnoid matter Subarachnoid Contains blood tough outer layer, a potential cavity thin and wispy contain CSF and delicate membrane bound tightly to vessels, connective continuous with between the dura and membrane deeper to blood vessels within surface of brain and spinal cord and (areolar) tissue and epineurium of the , dura mater web-like strands of carries blood vessels. fat spinal nerves Contains a small arachnoid tissu Forms the filum terminale, which volume serous fluid anchors spinal cord to coccyx and the that attach the spinal cord to the dura mater. 4 Lecture 3: Sensory Tracts (1\1)

Dorsal column Spinothalamic pathway Tracts Funiculus Cuneatus Funiculus Gracilis Lateral spinothalamic Anterior spinothalamic

● Discriminative Touch ● pain ● Non-Discriminative touch ● Two Point Discrimination Function ● Temperature ● pressure ● Proprioception

Neuron I cell body lies in the dorsal root ganglion small cells in the dorsal root ganglia. :medium cells in the dorsal root ganglia.

Substantia Gelatinosa of Rolandi in the Nucleus Cuneatus Nucleus Gracilis Nucleus Proprius (main sensory nucleus) Neuron II / synapse 1 posterior horn

decussate in the medulla as Internal Arcuate Fibers and ascend through the the cell bodies of which liein the contralateral dorsal horn, then decussate and ascend as Neuron II axons brainstem as Medial Lemniscus which terminates in the thalamus spinal lemniscus

Neuron III/synapse 2 Ventral Posterior Nucleus

Neuron III axons project to the somatosensory cortex (thalamocortical fibers)

Spinocerebellar pathways Tracts Posterior Spinocerebellar Anterior Spinocerebellar

Carry information derived from muscle spindles, Golgi tendon organs and tactile receptors, joints, skin, and subcutaneous tissue to the cerebellum for the control ofposture and Function coordination of movements.

Neuron I large cells of dorsal ganglia.

Neuron II / synapse 1 nucleus dorsalis; Clark's nucleus (column)

cross to opposite side, ascend as far as the midbrain, and then make a sharp turn caudally terminate ipsilaterally (uncrossed) in the cerebellar cortex by entering through (the fibers cross the midline for the second time) and enter the superior cerebellar peduncle Neuron II axons the inferior cerebellar peduncle to terminate in the cerebellar cortex

Spinoolivary Tracts Spinotectal Indirect spinocerebellar pathway Spinoreticular (spino-olivo-cerebellar)

● Involved in perception of dull aching (slow pain) reflexive turning of the head and eyes (spinovisual Contribute to movement coordination associated ● Forms part of the ascending reticular activating Function reflex) toward a point of cutaneous stimulation primarily with Balance (indirect pathway) system

Neuron I Dorsal Root Ganglion (receive axons through the dorsal)

Neuron II / synapse 1 lie in base of the dorsal horn Inferior Olivary Nucleus Lies in the dorsal horn

Contains uncrossed fibers that Cross to opposite side (anterolateral part), and end in medullary & both crossed & uncrossed project to the periaquiductal gray matter and Relayed to the cerebellum Neuron II axons fibers that terminate in pontine reticular formation, finally to the superior colliculus in the midbrain thalamus; to Activate the cerebral cortex

Lesions of the sensory tracts

Disease Cause Tracts affected Result

Dorsal column and lumbosacral dorsal spinal Loss of proprioception which is manifested by a high steppage and Tabes Dorsalis Syphilitic infection root (fasciculus gracilis) unsteady gait (sensory ataxia)

Subacute Combined Sensory ataxia Systemic disease result from B12 deficiency Dorsal column and lateral columns Degeneration of the spinal cord Weak and spastic limbs

Loss of proprioception in hands and fingers (astereogenosis) Dorsal column (fasciculus cuneatus) of the Signs: Multiple Sclerosis Immune disease cervical region Musculoskeletal: weakness, spasms, ataxia Sensation: pain, hyposthesia, paraesthesias

Spinothalamic tracts (lateral first then Loss of pain and temperature in the upper limbs Syringomyelia Damage in syringomyelia anterior) Charcot’s joint

Incoordination of arms, intense tremor, wide base reeling Friedrichs ataxia Inherited degeneration disease Spinocerebellar tracts gait ataxia

5 Lecture 4: Brachial and Lumbosacral Plexuses (1\1)

Brachial Plexus

⤞ forms in the posterior triangle of the necks by the union of the anterior rami ⤞ from C5~T1

Roots Trunks Divisions Cords (In the posterior ▲ of the neck) (In the posterior ▲ of the neck) (Behind the clavicle) (In the axilla)

⤞ C5~T1 ⤞ Upper ⤞ Anterior & Posterior ⤞ Lateral ⤞ Branches: ⤷ Nerve to subclavius divisions of each ⤞ Posterior ⤷ Dorsal Scapular n. ⤷ Suprascapular n. trunk ⤞ Medial ⤷ Supply to phrenic n. ⤞ Middle ⤷ Long Thoracic n. ⤞ Lower Important branches and their supply

Branches (In the axilla) Dorsal scapular nerve (C5) ➔ Rhomboideus, levator scapulae muscles Long thoracic nerve (C5, 6, 7) From medial cord {4MU}: From lateral cord {2LM}: From posterior cord {ULTRA}: ⤞ ⤞ ⤞ ➔ Serratus anterior Medial pectoral n. Lateral pectoral n. Upper subcapsular n. ⤷ ⤷ ⤷ Suprascapular nerve (C5, 6) Medial root to median n. Lateral root to median n. Lower subcapsular n. ⤷ ⤷ ⤷ ➔ Supraspinatus and infraspinatus muscles Medial cutaneous n. to arm Musculocutaneous n. Thoracodorsal n. ⤷ ⤷ ⤷ Lateral pectoral nerve (C5, 6, 7) Medial cutaneou n. to forearm Radial n. ⤷ ⤷ ➔ Pectoralis major muscle Axillary n. ⤷ Musculocutaneous nerve (C5, 6, 7) ➔ Anterior compartment of arm (Flexors of shoulder & elbow Injuries Upper subscapular nerve (C5, 6) ➔ Subscapularis muscle Thoracodorsal nerve (C6, 7, 8) Upper trunk (C5 & Lower trunk lesion (C8 Median nerve injury Radial nerve Related to humerus ➔ Latissimus dorsi muscle C6) &T1) fractures Lower subscapular nerve (C5, 6) ➔ Subscapularis and teres major muscles -Called -Called Klumpke’s Palsy -Called Ape’s hand or -Called -Axillary Nerve: Axillary nerve (C5, 6) Erb-Duchenne or Claw hand Pointing index finger saturday night surgical neck ➔ Deltoid and teres minor muscles; Palsy or Waiter’s -Complete claw hand. -Loss of flexion, palsy -Radial Nerve: radial Radial nerve (C5, 6, 7, 8; T1) tip position (median & ulnar ns. opposition & weak Wrist drop groove, ➔ Posterior compartment of arm & forearm & hand -Adducted arm, and affected) abduction of the -Paralysis of of -Ulnar nerve: medial (Extensors of elbow, wrist & fingers) extended & -Partial claw hand. thumb extensors of epicondyle Medial pectoral nerve (C8; T1) pronated forearm (Ulnar n. only affected) -Loss of flexion of the wrist & fingers ➔ Pectoralis major & minor (Can happen during -Paralysis of the muscles index Ulnar nerve (C8; T1) + Median nerve (C5, 6, 7, 8; T1) baby delivery) supplied by the damaged finger,paralysis of ➔ Anterior compartment of forearm & hand (Flexors of nerve both FDS & FDP wrist & fingers)

Lumbosacral Plexus

Lumbar part Sacral part

⤞ Formed by the union of the ventral rami of L1,L2,L3 & most of L4. ⤞ Formed by the union of the ventral rami of a part of L4 & whole of L5 (Lumbosacral trunk) ⤞ Located in the substance of psoas major muscles. and S1,S2,S3 & most of S4. ⤞ Main branches: ⤞ Located in front of piriformis muscle. ⤷ liohypogastric & Ilioinguinal nerves → Supplies the anterior abdominal wall ⤞ Main branches: ⤷ Obturator nerve → Supplies the medial compartment of the thigh ⤷ Pelvic splanchnic nerve (S2,3 & 4) :Preganglionic parasympathetic supply to: Pelvic ⤷ Femoral nerve → Supplies the anterior compartment of the thigh Viscera & Hindgut ⤷ Pudendal nerve (S2,3 & 4): Supplies the perineum ⤷ Sciatic nerve lumbosacral plexus (L4, L5, S1, S2 & S3): Supplies the lower limb

Femoral Nerve Sciatic Nerve

⤞ Originates from lumbar plexus ⤞ Originates from sacral part. It’s a terminal branch of the sacral plexus. ⤞ Course: ⤞ Course: ⤷ Descends lateral to psoas major & enters the thigh behind the inguinal ligament. ⤷ Leaves pelvis through greater sciatic foramen. ⤷ Then passes lateral to femoral artery, then divides into terminal branches. ⤷ passes gluteal region between ischial tuberosity & greater trochanter → then to ⤞ Muscular branches posterior compartment. ⤷ In abdomen: To iliacus (flexor of hip joint). ⤞ Branches into common peroneal (fibular) nerve & Tibial nerve. ⤷ In lower limb: To anterior compartment of thigh: ⤷ To flexors of hip joint: sartorius & pectineus. Motor Injuries: Sensory Injuries: ⤷ To extensors of knee joint: quadriceps femoris ⤞ Cutaneous branches ⤞ Wasting of muscles below knee. ⤞ Loss of sensation below the knee ⤷ To antero-medial aspects of the thigh. Foot assumes “foot drop” position EXCEPT the medial side of leg & ⤷ To medial side of knee, leg and foot (saphenous nerve) by its weight. foot (supplied by femoral n.)

Injuries Fibular Nerve Tibial Nerve

Motor Sensory ⤞ Course: ⤞ Course: ⤞ Wasting of quadratus femoris ⤞ Loss of sensation in the ⤷ Leaves the popliteal fossa ⤷ Descends through the popliteal fossa ⤞ Loss of knee extension anteromedial aspect of the thigh, ⤷ Turns around the lateral aspect of the to the posterior comp. of the leg. ⤞ Weak hip flexion and the medial side of the leg & fibula’s neck ⤷ Passes deep to flexor retinaculum to foot. (Areas supplied by the femoral ⤞ Divides into: the sole of the foot where it divides nerve) ⤷ Superficial peroneal → lateral comp. leg. into medial and lateral planter nerves. ⤷ Deep Peroneal → anterior comp. of leg Supplies: Muscles of posterior Supplies :Muscles of anterior & lateral compartment of leg & intrinsic muscles of compartments of leg (Dorsiflexors of ankle, sole Plantar Flexors of ankle, flexors of toes Extensors of toes & evertors of foot. & invertors of foot. 6 Lecture 5: External structures of brainstem

● Definition: is the region of the brain that connects the cerebrum with the spinal cord. ● Site: on the basilar part of occipital bone () Brainstem ● Parts: 1- Midbrain ,2- pons ,3- medulla oblongata and they are connected to Cerebellum by cerebellar peduncles (superior, middle & inferior). Functions of the brainstem: Contains the reticular formation which is responsible for: control of level of consciousness, perception of pain, and regulation of 1 cardiovascular & respiratory systems. 2 Pathway of tracts between cerebral cortex & spinal cord (ascending and descending tracts). 3 Site of origin of nuclei & emergence of (from 3rd to 12th). Medulla Oblongata

Ventral Surface Dorsal Surface

Ventral surface - Divides the medulla into 2 - Cavity: Central canal. ventral halves. - Composed of: median - Its lower part is marked Dorsal median sulcus: divides the closed medulla into 2 fissure by decussation of most of halves. pyramidal fibers Fasciculus gracilis: on either side of dorsal median sulcus. Closed Gracile tubercle: an elevation produced at the upper part Ventral median fissure Medulla of fasciculus gracilis, marks the site of gracile nucleus. - An elevation on either side Fasciculus cuneatus: on either side of fasciculus gracilis. Dorsal surface of ventral median fissure. Pyramid Cuneate tubercle: an elevation produced at the - Produced by corticospinal upper part of fasciculus cuneatus, marks the site of tract cuneate nucleus.

Fasciculus cuneatus - An elevation lateral to the - Cavity: 4th ventricle. pyramid. - On either side, an inverted V-shaped sulcus divides the Olive - Produced by inferior Open Medulla area into 3 parts (from medial to lateral): olivary nucleus Hypoglossal triangle, Vagal triangle, Vestibular area

Pons

Ventral Surface Dorsal Surface Ventral surface

Basilar Divides the pons into 2 halves,occupied Separated from open medulla by an imaginary line passing between sulcus by basilar artery. the margins of middle cerebellar peduncle. Dorsal surface - On either side of median sulcus, it divides into 2 parts (from medial Transverse Originate from pontine nuclei, cross the to lateral) : Medial eminence & facial colliculus: overlies abducens pontine midline & pass through the contralateral nucleus.Vestibular area: overlies vestibular nuclei. (ponto- middle cerebellar peduncle to enter the - The dorsal surfaces of open medulla and pons lie in the caudal 1/3rd cerebellar) opposite cerebellar hemisphere. and the rostral 2/3rd of the floor of the 4th ventricle respectively. fibers

Midbrain Ventral surface Crus cerebri Ventral Surface Dorsal Surface

- Large column of descending fibers (crus cerebri or basis - Marked by 4 elevations: pedunculi), on either side, separated by a depression called the Two superior colliculi: concerned with visual reflexes. Dorsal surface interpeduncular fossa. Two inferior colliculi: forms part of auditory pathway.

12th: From sulcus between pyramid & olive , 9th-10th-11th: From sulcus Ventral Surface of Medulla dorsolateral to olive

5th:the middle of ventrolateral aspect of pons ,6th:the junction between Ventral Surface of Pons the pons & pyramid 7th-8th: cerebellopontine angle from:

Ventral surface= 3rd: Medial aspect of crus cerebri. Dorsal surface=

Nerves Emerge Midbrain 4th: Cudal to inferior colliculus 7 Lecture 6: Internal structures of the Brainstem 1\2

Medulla oblongata

Caudal (Closed) Medulla MId Medulla

Traversed by the central canal Traversed by the central canal

Motor decussation (decussation of the pyramids) Formed by pyramidal fibers, (75-90%) cross to the Pyramids are prominent ventrally opposite side ● They descend in the lateral white column of the spinal cord as the lateral corticospinal tract. Larger size Gracile & Cuneate nuclei, concerned ● The uncrossed fibers form the ventral with proprioceptive deep sensations of the body. corticospinal tract

Axons of Gracile & Cuneate nuclei form the Trigeminal sensory nucleus. it is the larger sensory internal arcuate fibers; decussating forming nucleus. Sensory Decussation ● The Nucleus Extends Through the whole Sensory Decussation: length of the brainstem and its ● Formed by the crossed internal continuation of the substantia gelatinosa arcuate fibers which are called of the spinal cord. Medial Leminiscus after their ● It lies in all levels of M.O, medial to the crossing. spinal tract of the trigeminal. ● Lies adjacent to the middle line ● It receives pain and temperature from ventral to the central canal face, forehead. ● Terminates in thalamus. ● Its tract present in all levels of M.O. is ● Concerned with proprioceptive deep formed of descending (how its sensory and sensation. descend?see the note) fibers that terminate in the trigeminal nucleus.

Rostral (Open Medulla)

On the ventral aspect Nuclei (beneath the floor of the 4th Tract The pyramid is clear, with medial lemniscus on either sides of ventricle except 1,2) middle line dorsal to the pyramid Inferior Olivary Nucleus: (see next slide for more info) 1. Inferior Olivary Nucleus: A convoluted mass of gray A. Medial longitudinal fasciculus: it is matter., lies posterolateral to the pyramids & lateral to important association tract; On the dorsal aspect the medial lemniscus. It is concerned with the control of movement. Upwards : It links the vestibular nuclei with ● Lower part of the floor of the 4th ventricle. nuclei of extraocular muscles .(3,4&6) as ● The Inferior Cerebellar Peduncle is, connecting M.O. 2. Cochlear nuclei:. dorsal and ventral to the Inferior (vestibulo-ocular tract) to help coordination with cerebellum. cerebellar peduncle, concerning with hearing. of ● dorsal and ventral to the Inferior cerebellar peduncle eye movements with head movements. lie the Cochlear nuclei 3. Hypoglossal Nucleus Downwards : It links vestibular nuclei with anterior horn 4. Dorsal vagal nucleus contains preganglionic cells of spinal cord (cervical & upper thoracic 5 parasympathetic fibers. segments) as (vestibulo-spinal tract)- so, the 4 neck & trunk move with head movements, so 2 maintaining balance of the body trunk and 3 5. Vestibular nuclei complex : composed of medial, head. 7 lateral, inferior & superior nuclei ,concerned with A equilibrium

B 6 6. Nucleus Ambiguus: (motor nucleus)lies dorsal to 2 olivary nucleus and gives motor fibers along 9th & 10th CN to Muscles of the pharynx, larynx & palate.

1 7. Solitary nucleus (sensory nucleus ) receive taste B. : between tectum of sensation from the tongue along the 7th, 9th 10th CN midbrain and spinal cord involved in head movements during visual and auditory tracking

● It is a complex matrix of nerve fibers & groups of nerve cells that extends throughout the brain stem.(coordination between the structures of the brain stem) Reticular ● It has a number of important functions i.e. Respiratory and Cardiovascular centers. ● Reticular tract Formation ○ Reticulo spinal tracts: Descending fibres Influence a muscle tone & posture ○ Reticular Activating system: Ascending fibers activate the cerebral cortex through the thalamus

8 Lecture 6: Internal structures of the Brainstem 2\2

The Pons Divided into

by the Trapezoid Body (consists of acoustic fibres from cochlear nuclei to Anterior part (Basis Points) ascend into midbrain as lateral Posterior part (Tegmentum) lemniscus and terminate in inferior colliculus).

(At the level of the trigeminal Caudal part of the Pons nerve)

Pontine nuclei: Are small masses of nerve cells, Motor nucleus of the : Lies in the receive cortico pontine fibers. Their axons form the lateral part of the floor of the 4th ventricle. transverse pontocerebellar fibers which pass to the contralateral side of the cerebellum through Middle Cerebellar peduncles. Main sensory nucleus of the trigeminal nerve: it lies lateral to the motor nucleus. Bundles of corticospinal & corticonuclear fibres (Pyramidal fibres) Superior cerebellar peduncles form the lateral boundary of the 4th ventricle The ascending fibres of the Medial lemniscus:- become separated from the pyramid and displaced dorsally. rotates 90 degree and lies horizontally. Rostral Pons

Superior Medullary Velum: Passes between the two Spinal tract & nucleus of Trigeminal. peduncles & forms the roof of the 4th ventricle.

Deep origin of cranial nerve nuclei :- Medial longitudinal fasciculus: Lies close to the Abducent nucleus midline beneath the floor of the 4th ventricle Facial motor nucleus

Midbrain Divided into

Ventral part (Tegmentum) at the level of the cerebral aqueduct. by the The cerebral aqueduct which is Dorsal part (Tectum) The most ventral part of the surrounded by a pear shaped of 4 colliculi tegmentum is the massive fibrous periaqueductal (central) gray matter. mass (Crus Cerebri)

Inferior Colliculus Level Superior Colliculus Level

Inferior colleculus is a large nucleus of gray matter that lies beneath a corresponding surface elevation. It is part of the auditory pathway. It receives fibers from the lateral Superior colliculus is a A large nucleus of gray lemniscus. matter that lies beneath corresponding elevation. Its efferent fibers pass to the thalamus ● It forms part of the visual reflexes. ● Its efferent fibers go to the anterior horn Trochlear nucleus: lies in the central gray matter close to the median cells & to cranial nuclei 3, 4, 6, 7 & 11). plane. The fibers of the trochlear nerve decussate (the only CN that ● It is responsible for the reflex decussate completely) in the superior medullary velum and emerge movements of the eyes, head and neck in from posterior surface of midbrain. response to visual stimuli

Decussation of the superior cerebellar peduncles in the midline.

Oculomotor nucleus: Situated in the central gray Ascending LEMNISCI: Medial, Lateral, Spinal (Lateral & anterior matter. spinothalamic tracts), and Trigeminal (Lateral & medial). The fibers of the oculomotor nerve passes anteriorly through the red nucleus to emerge on the medial side of the crus cerebri (In Substantia nigra : Occupies the most ventral part of the tegmentum. It interpeduncular fossa) consists of a pigmented, melanin containing segment (Pars Compacta) and a non pigmented segment (Pars Reticulata) and projects to the basal ganglia. Its degeneration (Pars Compacta) is associated with Parkinson’s disease. Red nucleus :A rounded mass of gray matter that lies in the central portion of the tegmentum. Its red coloration is due to its vascularity and the Crus cerebri It is a massive mass ventral to the substantia nigra.It presence of an iron containing pigment in the consists entirely of descending cortical efferent fibers (Frontopontine, cytoplasm of its neurons. Corticospinal & corticobulbar and Temporopontine Fibres) to the It is involved in motor control motor cranial nerve nuclei and to anterior horn cells of spinal cord. Involved in the coordination of movement. Present in both levels of colliculi. 9 Lecture (7) Nerve Supply of the Face 5th & 7th 1\2 5th CN: Trigeminal Nerve

● Type: Mixed (Sensory & Motor). ● Receive: sensory supply from the face (with an exception of a small area over ramus of mandible by great auricular nerve C2,C3).

Fibers Nuclei

General somatic Afferent: General somatic (Mesencephalic nucleus): receives proprioceptive fibers from Afferent Carrying muscles of mastication. general sensations from face and anterior part of the General somatic Afferent: scalp. (Principal (Main) sensory nucleus) :receives touch fibers from face & scalp

Special Visceral General somatic Afferent: Efferent: Supplying (Spinal nucleus):receives pain & temperature sensations from muscles developed face & scalp. from the 1st pharyngeal arch, (8 muscles). Special Visceral Efferent (Motor nucleus) :supplies: 8 Muscles 1) Four Muscles of mastication (temporalis, masseter, medial & lateral pterygoid). 2) Other four muscles (Anterior belly of digastric, mylohyoid, tensor palati & tensor tympani).

Site: Occupies a depression in the middle cranial fossa (apex of petrous ). (trigeminal impression) -(trigeminal cave). Importance: Contains cell bodies : 1. Whose dendrites carry sensations from the face & scalp. Ganglion Trigeminal 2. Whose axons form the sensory root of trigeminal nerve.

Trigeminal Nerve

Emerging division

Ophthalmic (CV1) Maxillary (CV2) Mandibular (CV3) Emerges From the middle pure sensory pure sensory mixed of the ventral surface of the pons by 2 roots : -Large Lateral sensory root pass through superior -small medial motor root. pass through Foramen pass through Foramen orbital fissure rotundum ovale

Sensory branches: Frontal : supplies skin Upper teeth, gum & of face & scalp. maxillary air sinus: Lingual : receives general anterior, middle & sensations from anterior ⅔ Lacrimal: supplies skin posterior superior the of tongue of face & sensory for alveolar nerves. Inferior alveolar: supplies lacrimal gland. lower teeth, gums & face. Face: Buccal: supplies face (cheek Nasociliary: supplies Zygomaticofacial nerve. on upper jaw). skin of face, Zygomaticotemporal Auriculotemporal: Supplies nasal cavity & eyeball. nerve auricle, temple, parotid Infraorbital nerve. gland & TMJ.

Motor branches:

To 8 muscles Trigeminal Neuralgia (4 muscles of mastication & other 4 muscles).

❖ Compression, degeneration or inflammation of the 5th cranial nerve may result in a condition called trigeminal neuralgia or tic douloureux. ❖ Usually involves maxillary & mandibular branches, rarely in the ophthalmic division.

10 Lecture (7) Nerve Supply of the Face 5th & 7th 2\2 7th CN: Facial Nerve ● Type: Mixed (Special Sensory, motor, Parasympathetic).

Fibers

Special Visceral Afferent Special Visceral Efferent General Visceral Efferent

carrying taste sensation from supplying muscles Supplying parasympathetic secretory fibers to anterior ⅔ of the tongue. developed from the 2nd pharyngeal arch. submandibular, sublingual, lacrimal, nasal & palatine glands

Nuclei

Special Visceral Afferent Special Visceral Efferent (motor nucleus of General Visceral Efferent (nucleus solitarius) facial nerve) (Superior salivatory nucleus)

receives taste from the anterior supplies: sends preganglionic parasympathetic secretory fibers to: ⅔ of tongue. 1. Muscles of the face 1. Pterygopalatine ganglion 2. Muscles of scalp, (Occipitofrontalis). 2. Submandibular ganglion 3. Muscles of the auricle. Posterior belly of Then the Postganglionic fibers pass to Sublingual, digastric, Platysma, Stylohyoid, Stapedius. Submandibular, Lacrimal, Nasal & Palatine glands.

❶ Emerges from the cerebellopontine angle by 2 roots: ❷ It passes through internal ❸ Emerges from the ➔ Medial motor root: contains motor fibers auditory meatus to the inner ear stylomastoid ➔ Lateral root (nervous intermedius): contains where it runs in facial canal. foramen & enters the parasympathetic & taste fibers. parotid gland where it ends.

carries preganglionic parasympathetic fibers to Greater petrosal nerve pterygopalatine ganglion then postganglionic fibers to lacrimal, nasal & palatine glands.

carries: Preganglionic parasympathetic fibers to submandibular Chorda tympani ganglion then postganglionic fibers to submandibular & sublingual glands. Taste fibers from anterior ⅔ of tongue. In facial canal:

Nerve to stapedius Control the amplitude of sound waves from the external environment to the inner ear.

Posterior auricular To occipitofrontalis muscle

Muscular branches To posterior belly of digastric & stylohyoid stylomastoid foramen as it emerges from the

★ Temporal Branches Of Facial Nerve

★ Zygomatic gives 5 terminal motor branches to ★ Buccal the muscles of the face gland ★ Mandibular ★ Cervical Inside parotid

Bell’s Palsy ❏ Damage of the facial nerve results in paralysis of muscles of facial expressions: Facial (Bell’s) palsy; also called lower motor neuron lesion (whole face affected) NB. In upper motor neuron lesion (upper face is intact) ❏ Face is distorted:

Unable to show teeth or close the eye on that side Drooping of lower eyelid Loss of ➢ facial expressions Sagging of mouth angle Hyperacusis ➢ chewing ➢ blowing Dribbling of saliva ➢ sucking 11 Lectrue (8) Cranial Nerves 9th & 10th 1\1 Glossopharyngeal (IX) Vagus (X)

● It is a Mixed nerve. it is the longest and most widely distributed cranial nerve. ● it's mixed nerve, a Sensory nerve with preganglionic parasympathetic and few ● The principal role of the vagus is to provide para sym supply to organs motor fibers throughout the thorax and upper abdomen. ● It has no real nucleus to itself. Instead it shares nuclei with VII and X ● It also gives sensory and motor supply to the pharynx and larynx.

Superficial attachment Course Superficial attachment Course

It arises from the ventral 1. It Passes forwards between aspect of the medulla by a Internal jugular vein and External its rootlets exit from the 1. The vagus runs down the neck on the linear series of small rootlets, carotid artery. medulla between olive and prevertebral muscles and fascia. in groove between olive and inferior cerebellar peduncle. inferior cerebellar peduncle. 2. Lies Deep to Styloid process. 2. The internal jugular vein lies behind it, It leaves the cranial cavity by Leaves the skull through and the internal and common carotid passing through the jugular 3. Passes between external and jugular foramen. It occupies arteries are in front of it, all the way foramen in company with the internal carotid arteries at the the posterior aspect of the down to the superior thoracic aperture. Vagus , and the Accessory posterior border of carotid sheath between the 3. It lies on the prevertebral muscles and nerves and the Internal Stylopharyngeus then lateral to it. internal jugular vein fascia. jugular vein. laterally and the internal 4. It reaches the pharynx by passing and common carotid 4. Enters thorax through its inlet: between middle and inferior arteries medially. ● Right Vagus descends in front of the Right constrictors, deep to Hyoglossus, subclavian artery. where it breaks into terminal ● Left Vagus descends between the left branches. common carotid and Left subclavian arteries.

Ganglia & Communications Ganglia & Communications

Superior Ganglion Inferior ganglion Inferior ganglion Superior Ganglion in the jugular foramen Large and carries general sensations from just below the jugular foramen Small with no branches. with: Inferior ganglion of pharynx, soft palate and tonsil. with:Cranial part of accessory nerve. It is connected to the Superior glossopharyngeal nerve It is connected to Auricular Branch of Vagus. Hypoglossal nerve. Cervical sympathetic ganglion. Superior cervical sympathetic The Trunk of the nerve is connected to the Facial Superior cervical sympathetic ganglion. ganglion nerve at the stylomastoid foramen. 1st cervical nerve. Facial nerve.

Component of fibers & Deep origin Component of fibers & Deep origin

Type of fibers Nuclei Structure innervated Type of fibers Nuclei Structure innervated

GVE fibers: General synapses in parasympathetic ganglia, SVE fibers: Special Nucleus ambiguus Supply stylopharyngeus muscle. Dorsal Visceral Efferent short postganglionic fibers innervate Visceral Efferent (NA) Nucleus of Cardiac muscle, smooth muscles, respiratory, Vagus gastrointestinal systems. And glands of viscera. GVE fibers: General inferior salivatory Relay in otic ganglion. Visceral Efferent nucleus (ISN). the postganglionic fibers supply parotid gland. SVE fibers: Special Muscles of Pharynx (except stylopharyngeus) Nucleus Visceral Efferent Larynx,Palate (except the tensor palati) ,Upper part of Ambiguus esophagus SVA fibers: Special Nucleus of solitary Originate from the cells of inferior ganglion, Visceral Afferent tract (NST). their 1- Central processes terminate in (NST). GVA fibers: General carry impulse from viscera in neck, thoracic and 2-Peripheral processes carry sensation from Nucleus of Visceral Afferent abdominal cavities Chemoreceptors in aortic bodies and the taste buds on posterior third of tongue. solitary tract baroreceptors in aortic arch. (was written in the (NST). summary) GVA fibers: General Nucleus of solitary Carry visceral sensation from mucosa of Visceral Afferent tract (NST). posterior third of tongue, pharynx, auditory SVA fibers: Special Sensation from auricle, external acoustic meatus and tube ,tympanic cavity and carotid sinus. Spinal Tract Visceral Afferent cerebral dura mater,esophagus, tympanic membrane , & nucleus of external auditory meatus and part of chonca of the trigeminal middle ear (was written in the summary) Tympanic: (sensory + para sym) relays in the otic ganglion and gives Pharyngeal: to the mucosa of secretomotor to the parotid gland pharynx . Superior Laryngeal: It divides into: Meningeal : to the dura (1) Internal Laryngeal :(sensory) It provides sensation to the hypopharynx, the epiglottis, and the part of the larynx that lies above the Auricular nerve: to the Nerve to Stylopharyngeus vocal folds. (also carry general and special external acoustic meatus and Tonsillar (sensory) muscle. sensation from the root of the tongue) (2) tympanic membrane. The only motor branch Branches External Laryngeal :(motor)supplies the cricothyroid muscle. Branches To carotid body Sensory branches from the Lingual : carries sensory branches, Recurrent Laryngeal :(both) the recurrent carotid sinus and body general and special (taste) from laryngeal nerve goes round the subclavian the posterior third of the tongue. (pressoreceptors and artery on the right, and round the arch of Pharyngeal :it enters the wall chemoreceptors). the aorta on the left It runs upwards and of the pharynx. It supplies medially alongside the trachea, and passes the mucous membrane of the behind the lower pole of the thyroid gland. pharynx, superior and Manifestation: gives motor supply to all the muscles of the middle constrictor muscles, Difficulty Of Swallowing and Absent Gag Reflex. Dysfunction Of The Parotid larynx, except the cricothyroid. It also and all the muscles of the Gland (Dry Mouth). Impairment Of Taste And Sensation Over The Posterior provides sensation to the larynx below the palate except the tensor lesion Nerve One-third Of The Tongue ,Palate And Pharynx. vocal folds. palati.

1. Lateral medullary syndrome: A degenerative disorder seen over age

of 50 mostly due to Thrombosis of the Inferior Cerebellar Artery. Manifestation: 2. Tumors Produce palatal and pharyngeal and laryngeal paralysis Abnormalities

Lesions Manifested by: Ipsilateral paralysis of the muscles of the Palate, Pharynx of esophageal motility, gastric acid secretion, gallbladder emptying, and lesion Nerve & X Nerve

Causes Of IX and Larynx. Ipsilateral loss of Taste from the Posterior Third of tongue. heart rate; and other autonomic dysfunction. 12 Lecture (9) Cranial nerves 11th and 12th (1\1)

11th cranial nerve 12th cranial nerve

Type Motor Motor

Cranial part: carries fibres that originate in the caudal Origin : Hypoglossal nucleus of the part of nucleus ambiguus. medulla (in the floor of 4th ventricle). -Emerges from lateral aspect of the medulla as a linear course : series of rootlets caudal to rootlets of the vagus nerve. -The fibers emerge from the anterior - At the side of medulla it joins the spinal root briefly then It surface of the medulla oblongata separates again. through the sulcus between the pyramid - At the level of jugular foramen these fibres join the vagus & the olive. nerve and distribute with it to muscles of the: -The nerve courses downward with soft plate, esophagus, pharynx and larynx. cervical neurovascular bundle (internal carotid artery, internal Jugular vein, Spinal part: vagus nerve),. Then curves forward Origin and course arises from motor neurons in ventral horn of the spinal behind mandible to supply the tongue. : gray matter at levels C1-C5 (spinal nucleus). During its initial course, it carries C1 -The axons leave the cord via series of rootlets, emerge fibers which leave in a branch to take laterally midway between the dorsal & ventral roots of the part in the formation of ansa cervicalis spinal nerves. (a loop of nerves supplying neck -Courses rostrally and enter the cranial cavity through the muscles). foramen magnum, and joins the cranial root briefly. The hypoglossal nucleus receives: -Separates once again as the nerve leaves the cranial 1- corticonuclear fibers from both cavity through the Jugular foramen. cerebral hemispheres EXCEPT the region -Supplies the: sternomastoid and trapezius muscles. that supplies genioglossus muscle (receives contralateral supply only). *The nucleus ambiguus and the spinal nucleus receive bilateral corticonuclear fibers (from both cerebral 2- Afferent fibers from nucleus solitarius hemispheres). and trigeminal sensory nucleus.

Foramen of exit: Jugular foramen hypoglossal canal.

Innervates all of the muscles of the tongue Except the palatoglossus (which is -Movement of the soft palate, larynx & Pharynx. supplied by the vagus nerve). So, it

Function : Controls the movements and shape of the -Movement of the neck. tongue during speech & swallowing. 2-Carries proprioceptive afferents from the tongue muscles.

1-Trapezius atrophy & weakness. 1-Loss of tongue movements. 2- Difficulty in chewing & speech. 2-Unilateral Trapezius paralysis. 3-The tongue paralyses, atrophies, becomes shrunken and furrowed on 3-Shoulder dropping. the affected side (LMN paralysis).

4-Speech & swallowing difficulty. 4-On protrusion, tongue deviates to the affected side. Injury 5 -Inability to turn head. 5-If both nerves are damaged, person can’t protrude tongue.

13 Lecture (10) Anatomy of the Ear (1\1) The External Ear

The Auricle The External Auditory Cana ● It has a characteristic shape and it collects air vibrations ● is a curved S-shaped tube about 2.5 cm, that conducts & ● It consists of a thin plate of elastic cartilage covered by a collects sound waves from the auricle to the tympanic double layer of skin membrane. Its outer 1/3rd is elastic cartilage, while its inner ● It receives the insertion of extrinsic muscles which are 2/3rds are bony supplied by the facial nerve. Sensation is carried by greater ● Its lined by skin, and its outer 1/3rd is provided with hairs, auricular & auriculotemporal nerves sebaceous and ceruminous glands (modified sweat glands that secrete a yellowish brownish substance called ear wax) Middle Ear (Tympanic Cavity)

● The middle ear is a narrow, oblique slit-like cavity (air-filled) in the petrous temporal bone & lined with mucous membrane. ● It contains the auditory ossicles, which transmit vibrations of the tympanic membrane (eardrum) to the internal ear ● The middle ear communicates anteriorly with the nasopharynx through the auditory tube ● Contains Auditory Ossicles :Stapes, Incus), Malleus They are covered by mucous membrane & are articulated by synovial joints. ● which extends from the anterior wall downard, forward and medially to the nasopharynx. ● The posterior 1/3rd of the canal is bony and its anterior 2/3rds are cartilaginous ● its function is to equalize the pressure of both sides of the eardrum

Lateral Wall Posterior Wall Anterior Wall Medial Wall It is largely formed by the The posterior wall has in its upper The anterior wall is formed below by a The medial wall is formed by the tympanic membrane. part a large irregular thin plate of bone that separates the lateral wall of the inner ear. The membrane is opening,which is the aditus to tympanic cavity from the internal The greater part of the medial obliquely placed, facing mastoid antrum a cavity behind carotid artery wall shows a rounded projection, downward, forward, & the middle ear, within mastoid There are 2 canals at the upper part of called the promontory, that laterally. process, it contains air cells) the anterior wall: results from the underlying 1st It’s extremely sensitive to Below, a small, hollow, conical Upper smaller, which is the canal for turn of the cochlea. pain. projection, the pyramid, which the tensor tympani muscle Above & behind the promontory Nerve supply of the houses the stapedius muscle and Lower larger, which is for the lies the oval window (Fenestra eardrum: its tendon auditory tube Vestibuli), which is closed by the Outer surface: The tendon emerges from the apex base of the stapes. Auriculotemporal nerve of the pyramid Below & behind the promontory Auricular branch of vagus Roof lies the round window (Fenestra nerve Formed by a thin plate of bone called Cochleae), which is closed by the Inner surface: tegmen tympani which is part of the secondary tympanic membrane. Tympanic branch of the Floor petrous temporal bone It separates glossopharyngeal nerve Formed by a thin plate of bone which the tympanic cavity from the separates the middle ear from the temporal lobe of the brain bulb of the internal jugular vein

Muscles of the Ossicles Nerve of the middle ear

Tensor Tympani Stapedius (the smallest voluntary muscle) tympanic nerve Facial nerve

Cartilage of the auditory tube & The tympanic nerve is a The facial nerve enters through the internal Origin Internal walls of the hollow pyramid the bony walls of its own canal branch of the acoustic meatus with the 8th nerve. It expands glossopharyngeal nerve to form the geniculate ganglion It passes It gives the Tympanic vertically behind the pyramid & leaves the The tendon emerges from the apex of the plexus on the middle ear through the stylomastoid foramen Insertion Into the handle of the malleus pyramid and is inserted into the neck of the promontory.The Branches: stapes tympanic plexus gives - Greater petrosal nerve: arises from the the lesser petrosal nerve geniculate ganglion & carries preganglionic which relays in the otic parasympathetic to supply Lacrimal, nasal, & Nerve Mandibular Nerve Facial Nerve ganglion. The lesser palatine glands. petrosal nerve gives - Nerve to stapedius reflexly limit the excursion of the Reflexly damps downs the vibrations of the secretomotor supply to - Chorda tympani: arises just before the facial Action tympanic membrane stapes the parotid gland nerve exits

Internal Ear (Labyrinth)

Vestibule Semicircular Canals Cochlea

-The vestibule is the central part of the bony -The first turn of the -There are 3 semicircular canals: Superior (anterior) labyrinth cochlea produces the Bony Labyrinth canal Posterior canal Lateral canal -It contains the utricle & saccule (parts of the promontory on the medial A series of bony chambers lined by -Each canal has a swelling at one end called the membranous labyrinth) wall of the tympanic

endosteum. They contain a clear fluid, ampulla -In the lateral wall of the vestibule are the fenestra cavity the perilymph, in which is suspended -The canals open into the vestibule by five orifices, vestibuli, which is closed by the base of the stapes, -It contains the cochlear the membranous labyrinth one of which is common to two canals Consists of & the fenestra cochleae, which is closed by the duct (part of the -Lodged within the canals are the semicircular ducts secondary tympanic membrane. membranous labyrinth)

Membranous Labyrinth Sacs Ducts

Consists of Consists of a series of membranous sacs & ducts within the bony Three semicircular ducts (lie within the bony labyrinth, its filled with endolymph , semicircular canals) consists of four ducts & two sacs, Utricle & Saccule (lodged in the bony vestibule) Cochlear duct (lies within the bony cochlea). The which freely communicate with one cochlear duct divides the bony cavity into Scala another. Consists of Vestibuli & Scala Tympani 14 Lecture11 : Cranial Nerve VIII (1\1)

type Origin Course

special Sensory Afferent (SSA) conveys ventral surface of brainstem through run laterally in posterior cranial fossa impulses from inner ear to nervous the cerebellopontine angle. and enter the internal acoustic meatus system. along with 7th nerve

Vestibular Part conveys impulses associated with body posture, balance and coordination of head & eye movements

First & Second order neurons Axons of vestibular nuclei may go

-1st Order Neurons :are located in the vestibular ganglion within the internal from the vestibular nuclei auditory meatus. 1- To ipsilateral flocculonodular lobe of cerebellum (vestibulo-cerebellar -Peripheral Processes (vestibular nerve fibers) make dendritic contact with tract) (For Balance) through inferior cerebellar peduncle. hair cells of the membranous labyrinth (inner ear). 2- Bilaterally to ventral posterior nucleus of thalamus, which in turn project to the cerebral cortex ( For conscious awareness). - central processes ( from vestibular nerve ) -mostly end up in the lateral , 3- Bilaterally to motor nuclei of cranial nerves (vestibulo-ocular tract) medial , inferior and superior vestibular nuclei (2nd order neurons) of the through medial longitudinal fasciculus (For coordination of head and eye rostral medulla, located beneath the lateral part of the floor of 4th ventricle movements). 4- To Motor neurons of the spinal cord as lateral (ipsilateral) directly & - Some fibers go to the cerebellum through the inferior cerebellar peduncle medial vestibulospinal (bilateral) tracts through medial longitudinal fasciculus ((for control the posture ).

Medial Longitudinal Fasciculus Extends through out the brain stem and formed of both descending & ascending fibers

Ascending Vestibulo-Ocular establishes connections with the nuclei of the Descending Vestibulo-Spinal extends into the spinal cord as the medial Oculomotor, Trochlear & Abducent nerves (motor nuclei for extraocular , for control the body posture. muscles) for coordination of head & eye movements.

Vestibulo Spinal Tracts Vestibulospinal fibers influence the activity of spinal motor neurons concerned with the control of body posture and balance.

lateral medial arises from lateral vestibular ( deiters ) nucleus, descends ipsilaterally. is the descending part of the medial longitudinal fasciculus, projects bilateraly

Vestibular Cortex -Located in the lower part of postcentral gyrus (head area). -Responsible for conscious awareness of vestibular sensation.

Cochlear Part conveys impulses associated with hearing. The representation of cochlea is essentially bilateral at all levels.

First order neurons Second order neurons Third order neurons

● Cells of spiral ganglion in ● Cells of dorsal & ventral cochlear nuclei in pons . the cochlea.Axons form ● Cells of inferior colliculus (midbrain) cochlear nerve. ● ● Cochlear nuclei belong to special somatic afferent Both colliculi are interconnected by commissural fibers. ● Cochlear nerve makes column in brain stem. dendritic contact with hair cells of Organ of Corti(in ● On ascending, most of axons decussate in the Cochlear Duct). trapezoid body & form lateral leminiscus.

● Some fibers end in Superior Olivary Nucleus & Nucleus of Lateral Leminiscus. Fourth order neurons

● Superior Olivary Nucleus & Nucleus of Lateral ● Leminiscus: modulate transmission of auditory Cells of medial geniculate nucleus information to cochlear nerve by: (thalamus). Axons form auditory 1. Sending inhibitory fibers through radiation that pass through vestibulocochlear nerve ending in Organ of retrolenticular part of internal capsule. ● Corti. Ends in primary auditory cortex 2. Establishing connection with motor neurons (superior temporal gyrus) which is supplying tensor tympani & stapedius connected to auditory association cortex. muscles

N.B. : Representation of cochlea is bilateral at all levels above cochlear nuclei 15 Lecture (12) Anatomy of the Nose & Olfactory Nerve (1\2)

The Nose Only in boys slide Reception of secretions Olfaction: ● The external (anterior) nares or nostrils lead to to the nasal cavity. from the paranasal sinuses 6 1 Smell ● Formed above by bony skeleton. and nasolacrimal duct. ● Formed below by plates of hyaline cartilage

Humidification of Respiration: the inspired air: Functions 5 2 Breathing Nasal Cavity Mucous

● It is a large air filled space above and behind the nose in the middle of the face. Warming the ● Each cavity is the continuation of one of the two nostrils. Filtration of inspired air: ● It communicates with nasopharynx posteriorly. dust 4 3 submucous ● It consists of Vestibule, Respiratory, and Olfactory regions. venous plexus. ● It extends from nostrils anteriorly to turbinate (choanae) posteriorly Divisions of Nasal Cavity:

Vestibule region: Respiratory region: Olfactory Region - The area surrounding the external opening to the nasal cavity. - Lined by modified skin, provided with hairs and Sebaceous - The largest region. - Located at the apex of the nasal cavity. glands to filter the incoming air. Exocrine glands in the skin that - Lined with mucous that is continuous with that of - It is lined by olfactory cells with secrete an oily or waxy matter called sebum to lubricate and Nasal Sinuses, Lacrimal sac, Conjunctiva, and olfactory receptors. waterproof the skin and hairs. Nasopharynx.

Nasal Cavity mucosa Only in girls slide

Respiratory mucosa Nasal (Olfactory) mucosa

● It is thick, ciliated highly vascular and contains mucous glands goblet cells ● It is delicate and contains olfactory nerve cells. ● It lines the lower part of the nasal cavity. ● It is present in the upper part of nasal cavity: (From skin of vestibule to the superior concha). ○ Roof ● It functions to moisten, clean and warm the inspired air ○ On the lateral wall, it lines the upper surface of the superior ● The air is moistened by the secretion of numerous serous glands concha and the sphenoethmoidal recess. ● It is cleaned by the removal of the dust particles via ciliary action of the ○ On the medial wall, it lines the superior part of the nasal columnar ciliated epithelium that covers the mucosa. septum. ● The air is warmed by a submucous venous plexus.

It is divided into right and left parts by nasal septum Each part has

Lateral Wall Marked by three projections Roof Floor 1. Superior concha. 2. Middle concha. 3. Inferior concha. It is formed by: It is formed by: Medial Wall They project into the nasal cavity, creating four pathways for the air to -Body of sphenoid The nasal (upper) flow: (Posteriorly). surface of the hard The nasal septum: 1.Spheno-ethmoidal recess: opening of sphenoid air sinus -Cribriform plate of (bony) palate: Vertical plate of 2. Superior meatus: receives openings of posterior ethmoidal sinuses. ethmoid (Middle). -Palatine process of ethmoid. 3. Middle meatus. Contain: (bulla ethmoidalis) for opening of middle -Frontal bone maxilla (Anteriorly). Vomer. ethmoidal sinus (Anteriorly). -Horizontal plate of the Septal Cartilage. Hiatus semilunaris for openings of maxillary sinus, - Nasal bone palatine (Posteriorly). Infundibulum opening of Frontonasal duct that drains the frontal sinus (Anteriorly). and anterior ethmoidal sinus. 4. Inferior meatus: receives opening of nasolacrimal duct. Paranasal Sinuses

Definition Functions Clinical significance

● They are a group of four paired air-filled spaces that 1. Inflammation surround the nasal cavity. 1. (Lighten the skull weight). The paranasal sinuses are joined to the nasal cavity via small ● They are lined with respiratory epithelium 2. Increasing resonance of the voice orifices called ostia These become blocked easily by allergic mucoperiosteum (ciliated pseudostratified columnar (Amplify the sound as we speak). inflammation or by swelling in the nasal lining that occurs with a epithelium). 3. Providing a buffer against facial cold If this happens, normal drainage of mucus within the sinuses ● Open in the lateral wall of the nasal cavity trauma. is disrupted, and sinusitis may occur. ● Divided into subgroups that are named according to the 4. Insulating sensitive structures like Because the maxillary posterior teeth are close to the maxillary bones within which the sinuses located: dental roots and eyes from rapid sinus, this can also cause clinical problems if any disease processes temperature change in the nasal cavity. are present, such as an infection in any of these teeth 1. The Maxillary Sinuses: the largest of the paranasal 5. Humidifying and heating of inhaled air 2. Cancer sinuses, located under the eyes, in the maxillary bones. because of slow air turnover in this Malignancies of the paranasal sinuses comprise approximately 0 2 2. The Frontal Sinuses: superior to the eyes, in the frontal region. of all malignancies bone, which forms the hard part of the forehead. About 80 of these malignancies arise in the maxillary sinus, 3. The Ethmoidal Sinuses: formed from several discrete tumors of the sphenoid and frontal sinuses are extremely rare. air cells within the ethmoid bone between the nose and Carcinomas are more frequent than sarcomas. the eyes. 4. The Sphenoidal Sinuses: in the sphenoid bone. 16 Lecture (12) Anatomy of the Nose & Olfactory Nerve (2\2)

Nerve supply Arterial supply Venous drainage Lymph drainage

● Nerves of smell: Olfactory Nerves (Cr 1). The nasal cavity receives blood from: ● Venous plexus in ● Submandibular & ● Nerves of general sensation: Ophthalmic ● Internal carotid branches: Anterior and submucosa formed ● Upper deep cervical and Maxillary divisions of Trigeminal Posterior Ethmoidal (ophthalmic). by veins nodes. nerve (Cr 5). ● External carotid branches: accompanying the ● The anterior part is supplied by: 1. Sphenopalatine artery (Maxillary). arteries Anterior Ethmoidal nerve. 2. Superior labial (Facial). ● They drain into the ● The posterior part is supplied by 3. Greater palatine artery pterygoid venous branches of the pterygopalatine 4. Lateral nasal arteries plexus & facial vein ganglion: ● Applied anatomy :The most common site or . 1. Nasopalatine for epistaxis is at the anterior & inferior 2. Nasal. part of nasal septum (Little’s area) because 3. Palatine. of the rich arterial anastomosis.

Olfactory nerve ● The first and shortest cranial nerve, it is the nerve that transmits special sensory information to have a sense of smell. ● it is one of two cranial nerves that do not emerge from the brainstem. ● Elderly people usually have less sensation of smell probably because of progressive reduction in number of olfactory cells. Olfactory pathway: it is important to note that the olfactory nerve is made up of multiple nerve fibers/rootlets coming from the receptors cells. The pathway can be summarized as follows: olfactory receptor cells, olfactory nerves, olfactory bulb, olfactory tract, olfactory striae, olfactory cortex The only sensory pathway which reaches the cerebral cortex without passing through the Thalamus.

Olfactory receptors Mitral cells of olfactory bulb Olfactory tract

● 2nd neurone ● 1st order neuron ● The olfactory tract runs inferiorly ● In the cranial cavity, the fibres enter the olfactory bulb, ● they are specialized, ciliated nerve to the frontal lobe which lies in the olfactory groove, within the anterior cells that lie in the olfactory ● Each tract divides into 2 roots at the cranial fossa. epithelium. anterior perforated substance ● Preliminary processing of olfactory information is ● The axons of these bipolar cells ● Posterior and anterior to the optic within the olfactory bulb which contains interneurons 12-20 fibers from the ture olfactory chiasm, the olfactory tract on both and large Mitral cells. nerve fibers which pass through the sides into medial and lateral ● The olfactory nerve fibres synapse with the mitral cribriform plate of ethmoid (in the olfactory striae. cells, forming collections known as synaptic glomeruli. roof of the nasal cavity) and then ● From the glomeruli, second order nerves then pass join the olfactory bulb. posteriorly into the olfactory tract

Olfactory STRIAE The primary olfactory cortex

● Medial root (Medial stria): ❖ crosses midline through anterior commissure and joins the uncrossed olfactory bulb lateral root of the opposite side. ❖ The primary olfactory cortex sends nerve fibres to ❖ It connects olfactory centers of 2 cerebral hemispheres, so many other areas of the brain, like piriform each olfactory centre receives smell sensation from both halves of nasal cavity. cortex, amygdala, olfactory tubercle and the ❖ Lateral root (Lateral stria): secondary olfactory cortex. ❖ Carries olfactory fibers to end in cortex of the Uncus & ❖ adjacent Hippocampal gyrus (center of smell). olfactory area These areas are involved in the memory and of the cerebral cortex (also known as the primary olfactory appreciation of olfactory sensations. cortex)

17 Lecture 13: Cranial Nerves II, III, IV & VI (1\1)

Nerve OPTIC OCULOMOTOR TROCHLEAR ABDUCENT

Type sensory Motor Motor Motor

Three neurons Has 2 nuclei + para sym fiber Small motor nucleus: Only one motor nucleus - 1st order neurons: Bipolar cells -Oculomotor nucleus:Axons s curve Fibers curve backwards It emerges from the of retina ventrally through the tegmentum and decussate. ventral aspect of the brain 2nd order neurons: Ganglion cells and the red nucleus in the The nerve emerges stem at the junction of the of retina. midbrain.The nerve emerges on the immediately caudal to the pons and the pyramid of 3rd order neurons: Neurons in anterior surface of the midbrain in inferior colliculus, on the the medulla oblongata. It the lateral geniculate body.. interpeduncular fossa.Then it passes dorsal surface of brain has the longest course to forward between 2 arteries: stem. reach the orbit. It passes Axons of retinal ganglion cells Posterior cerebral artery, Superior through cavernous sinus, converge at the optic disc and cerebellar artery. In the middle It passes forward through lying below and lateral to pass as the optic nerve. cranial fossa it runs in the lateral middle cranial fossa in the the internal carotid -Then the nerve passes wall of the cavernous sinus, then it lateral wall of the artery,Then it enters the posteromedially in the orbit. Then divides into superior and inferior cavernous sinus below the orbit t Course exits through the optic canal divisions which pass through the oculomotor nerve. Fibers of facial nerve Then it enters the middle cranial superior orbital fissure to the orbit looping around the fossa to joins the. optic chiasma The nerve then enters the Abducent nucleus, forms Fibers of nasal (medial) half of -Edinger-Westphal nucleu :Axons orbit through the superior the facial colliculus. the retina decussate in the accompany the oculomotor nerve orbital fissure. chiasm and join uncrossed fibers fibers to the orbit, where they of the opposite side temporal terminate in the ciliary ganglion. (lateral) half of the retina to form the optic tract Mainly terminate -Postganglionic fibers pass through in the (LGB), lateral geniculate the short ciliary nerves to the body of the thalamus eyeball, where they supply: A few fibers terminate in pretectal area and superior colliculus.

• Elevation of upper eyelid. • Turning the eyeball upward, Vision downwards and medially, Rotates the eye ball Rotates the eye ball (transmits visual information Function •Constriction of the pupil (Pupillary downwards and laterally. laterally (abduction). from the retina to the brain) reflex). • Accommodating reflex of the eyes

Motor to: 1. Levator palpebrae superioris 2. Superior rectus muscle 3. Medial rectus muscle 4. Inferior rectus muscle ——- Superior oblique muscle Lateral rectus muscle Supplies 5. Inferior oblique muscle.

Parasympathetic fibers to: 1- Constrictor pupillae 2- Ciliary muscles.

Disease of the eyeball as: 1. Lateral squint. • diplopia (double vision) Inability to direct the Cataract, Intraocular 2. Ptosis. • Inability to rotate the affected eye laterally, so it haemorrhage, Retinal 3.Diplopia. eyeball inferolaterally. So, result in (medial squint). detachment, Disease of optic 4. Pupillary dilatation. the eye deviates; upward -A nuclear lesion may also nerve, MS, (multiple sclerosis), 5. Loss of accommodation. and slightly inward involve the nearby Optic nerve tumors lead to loss of 6. The eyeball is fully abducted and (medially). This person has nucleus or axons of the vision in the affected depressed. difficulty in walking facial nerve, causing eye, (monocular blindness). downstairs paralysis of all facial 2. Compression of the optic muscles in the ipsilateral chiasm by an adjacent pituitary side. tumour leads to Bitemporal hemianopia. Lesion 3. Vascular and neoplastic lesions of the optic tract, or optic radiation produce a Homonymous hemianopia, (Contralateral).

Ptosis

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