Aclands Videos - Supplementary material notes from the online Acland video modules PDF

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Supplementary material notes from the online Acland video modules ...

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Acland Videos 4.7.1 Brain: Initial overview   

Largest part of the brain = cerebrum o Cerebrum divided at the midline into 2 cerebral hemispheres Below but separate from the cerebrum = cerebellum Both cerebrum and cerebellum grow out of the brainstem o Brainstem continues to the spinal cord

4.7.2 Lining of the cranial cavity, falx ad tentorium 

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Brain inside the cranial cavity o Made of skull bone o Divide into the floor of the cavity into 3 parts  The sphenoid ridges separate the  Anterior cranial fossa from the middle cranial fossa  The petrous temporal ones separate the  Middle cranial fossa from the posterior cranial fossa Frontal lobe occupies the anterior cranial fossa Temporal lobe occupies the middle cranial fossa Brainstem and cerebellum occupy the posterior cranial fossa Foramen magnum (giant hole at the base of skull): brain stem exits through it and continues onto spinal cord Cranial cavity is lined with tough, shiny fibrous tissue = the dura o The dura lining passes through the foramen magnum and is continuous in lining the spinal canal The falx and the tentorium are extensions of the dura Tentorium cerebelli o Separates the posterior cranial fossa from the rest of the cranial cavity o Separates the cerebrum, and the cerebellum o The opening in the tentorium is the tentorium incisure  Which allows brain stem to past through it o Attached along the occipital bone and the edge of the petrous temporal bone  Attachment ends at the posterior clinoid process o The upper surface of the tentorium is continuous with the dura of the middle cranial fossa  Blends into the dura o Add the midline, the tentorium is attached to the falx Falx cerebri o Forms a midline partition between the two cerebral hemispheres o Attached to the occipital, parietal and frontal bones o At the front of the skull it is attached to the crista galli o When split in two it has a small triangular space for the superior sagittal sinus  Sagittal sinus is an important part of the brain drainage system

4.7.3 The meningeal layers: dura, arachnoid, pia  

Dura, arachnoid, pia = the meninges Inward fold = sulcus, outward fold = gyrus

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Pia layer: very thin, looks like the glossy layer o Extends down into the sulcus and back up to the gyrus o Each sulcus contains blood vessels that lie just outside the pia  Each vessel is surrounded by a sleeve of pia Arachnoid: delicate transparent membrane o Doesn’t extend into the sulci, bridges across the gyrus o Contains the subarachnoid space  Cisterns = large spaces of subarachnoid space  Infront and behind the cerebellum  Infront of the brain stem Dura: tough layer of tissue o Closely attached to the bone o Branches of the meningeal artery runs in the thickness of the dura  The nerves and vessels that exit the brain cavity, exit via openings in the dura  Dura forms a tunnel around the vessel or nerve  There are differences in the openings of the dura and openings of the bones o As the dura wraps around the vessel of nerve leading it to the bony opening

4.7.4 Lining of middle cranial fossa   

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Middle cranial fossa houses the pituitary fossa Pituitary fossa is closed in by the clinoid processes The dura covers the fossa and creates an opening in the middle o This contains the pituitary gland o The cavity is lined with dura Lateral to the pituitary fossa is the cavernous sinus Trigeminal nerve enters through an opening in the dura to a side cavity under called the trigeminal cave o Trigeminal cave houses the trigeminal ganglion

4.7.9 Cerebrum 

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Functions of entire cerebrum o Vision o Hearing o Smell o Touch o spatial perception o speech and language o memory o thought o voluntary actions Made from 2 cerebral hemispheres o Separated by the midline  Falx cerebri  Occupies the longitudinal cerebral fissure o Hemispheres are connected by the corpus callosumat the midline

Below this they are connected by the cerebral peduncles converging on the brain stem  And the floor of the 3rd ventricle Frontal lobe = occupies anterior cranial fossa Temporal lobe = occupies the medial cranial fossa Occipital lobe = lies above the tentorium. Its upwards slope conforms to the shape of the tentorium Each fold of gyrus and sulcus has a name. only need to identify 2 o Central sulcus  Runs all the way from the lateral sulcus to the midline o Lateral sulcus  Very deep, extends to the underside of the brain  Separates the frontal lobe and the temporal lobe  These sulci form boundaries between the front lobe and the parietal and temporal lobe Lobes: o Frontal o Temporal o Parietal o Occipital The uncus o Tip of the temporal lobe o Lies just above thee tentorial incisure Olfactory tract o Underside of the frontal lobe ends in the olfactory bulb  Olfactory nerve emerges from here o

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4.7.7 midbrain, cerebral peduncles  

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Midbrain = lies above the pons On its dorsal surface o Roof of the fourth ventricle o Superior cerebellar peduncles o Bulges = inferior and superior colliculi o Pineal body in the midline Trochlear nerve emerges form the dorsum of the midbrain Midbrain spreads out into 2 columns = cerebral peduncles o Connect the brainstem to the cerebrum Above the peduncles is the medial geniculate body and the lateral geniculate body which give rise to the optic tract o Between the peduncles the oculomotor nerve emerges Optic nerve and optic tract meet at the optic chiasm where the nerves emerge

4.7.6 Medulla, fourth ventricle 

ventricular system o filled with CSF  2 lateral ventricles connect to the 3rd ventricle which descends to the 4th ventricle

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Brainstem o Medulla: cone shaped and tapers down to be continuous with the spinal cord at the foramen magnum o Pons o Midbrain  Contains tracts the connects the cerebrum, cerebellum, and the spinal cord  Contains nuclei that control basic autonomic functions  Origin of nearly all cranial nerves Medulla, bons and midbrain o Located behind the basilar part of the occipital bone and the dorsum sellae Dorsal aspect of the medulla faces backwards Back of the upper part of the medulla forms the floor of the fourth ventricle The superior medullary velum forms the top of roof of the fourth ventricle The inferior medullary velum forms the bottom of the roof of the fourth ventricle Ventral aspect of the medulla o Has the bulges  The pyramid  The olive o Emerging from this is the filament of the 4 last cranial nerves  Hypoglossal  Accessory  Vagus  Glossopharyngeal Pons o Becomes continuous with the middle cerebellar peduncle o Arising from the groove between the pons and medulla are 3 cranal nerves  Vestibulocochlear nerve  Facial nerve  Abducent nerve o Trigeminal nerve arises from the upper part of the pons

4.8.1 Olfactory and optic nerves 

1st olfactory: o Extremely short o Made of fine filaments o Arise from the olfactory bulb on the underside of the frontal lobe o Lies just above the cribriform plate  Forms a narrow rough of the nasal cavity  Filaments of olfactory nerve, run through plate and mucous membranes to meeting nerve endings in the nose to get the smells

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2nd optic o Optic nerve ends emerge from optic chiasm  Optic chiasm is where they cross over  Into the opposite optic tract  Fibres that connect to the lateral halves of the retinae stay on the same side of the optic tract

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 Passes through the dura to enter optic canal  Underneath chiasma in the carotid arteries and the pituitary fossa o Nerve attaches to the eye between the rectus muscles origin o Which is where the retina is o It is covered throughout the whole canal by the meningeal layers  Dura is continuous with the sclera rd 3 oculomotor o Eye Motor nerve o Arises from the cerebral peduncles o Bony: Passes through the superior orbital fissure o Dura: alongside the posterior clinoid process o Pass through the lateral wall of the cavernous sinus  Cavernous sinus leads to the superior orbital fissure o Nerve divides into an upper and lower branch  Upper branch supplies the  Superioris and superior rectus muscles  lower branch supplies  medial rectus, inferior rectus and inferior oblique muscles o also assists with the autonomic control of the intraocular muscles and shape of the lens 4th trochlear o Eye Motor nerve o Arises form the back of the midbrain o Bony: Passes through the superior orbital fissure o Pass through the lateral wall of the cavernous sinus o Supplies the superior oblique muscle 5th Trigeminal (massive nerve) o V1 ophthalmic  Exits via the superior orbital fissure  As it passes through it divides  The frontal nerve which runs beneath the roof of the orbit o Divides in cutaneous branches which go to the orbit  Into the lacrimal nerve which supple the lacrimal gland  The nasociliary nerve: gives sensation to the eyeball o Gives off one or more ethmoidal nerves and a cutaneous branch the infratrochelear nerve o They exit out of the supra orbital, supratrochlear or infratrochelear nerve  Supply the forehead, upper eyelid, and upper part of the nose  Ethmoid branches supply the lining of the nasal cavity o V2 maxillary  Exits via the foramen rotundum  Pterygo-maxillary fissure continuous with the inferior orbital fissure  Maxillary nerve emerges deep in Pterygo-maxillary fissure  Divides into branches as it approaches the maxilla

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Continuing trunk of the nerve = infraorbital nerve o Runs forward into a bony tunnel in the floor of the orbit, emerges via the infra-orbital foramen o Branches supply the upper teeth, nasal cavity and palate and the upper part of the cheek. o They run through tunnels in the bone o Divides into  Palpebral:  Labial:  Nasal branches:  Supple the lower eyelid, part of the nose and cheek and apart of the lip Posterior superior alveolar nerves o Run down to enter tunnels in the maxilla Anterior superior alveolar o Runs downwards  These form a loop where dental and gingival branches arise  Which supply the teeth and upper gums Palatine and nasopalatine branches o Supply palate and parts of the nasal cavity o Goes through the sphenopalatine foramen o Separate into the greater and lesser palatine enrves  Emerge through the palatine foramen and provide sensation to the palate o Nasal branches supply back part of the nasal cavity Zygomatic branch o Pass through the zygomatic bone to supply cheek

V3 mandibular  Exits via the foramen ovale  Emerges behind the lateral pterygoid plate  Has motor and sensory branches  Motor: controls muscles of mastication  Sensory: o Buccal nerve: sensation to the cheek inside and out o Auriculotemporal nerve: sensations to the temples o Inferior alveolar nerve: enters mandible through mandibular foramen. Supplies the lower teeth and gums, chin and lower lip o Lingual nerve: common and taste sensations to the front 2/3rd of the tongue Main functions: provide sensation to the face, nasal cavity, and oral cavity. AND supply motor information to the muscles of mastication Emerges from the pons and passes forwards  To the tunnel in the dura and leads to the trigeminal cave  Where the branches branch off

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The sensory fibres synapse in the ganglion located here = the trigeminal ganglion

6th abducens o Eye Motor nerve o Arises below the pons o Bony: Passes through the superior orbital fissure o Pass through the lateral wall of the cavernous sinus o Supplies the lateral rectus muscle  Abducts the eye 7th facial nerve o Leave the brainstem just below the pons o Pass through the internal auditory meatus then into the facial canal bony tunnel, comes out around the styloid process o Passes through the parotid gland o Gives off 3 branches  Greater petrosal nerve: autonomic branch  Nerve to the stapedius muscle  Chorda tympani: tramsits taste sensation o Supplies all the branches of facial expression 8th vestibulocochlear nerve o Leave the brainstem just below the pons o Pass through the internal auditory meatus o Divides into  Vestibular nerve: transmits balance  Cochlear nerve: transmits hearing th 9 glossopharyngeal o Arise from a line of filaments that arise form the lateral aspect of the medulla o Out of jugular foramen o Runs lateral to the stylopharyngeus muscle  Supplies this muscle o Enters the wall of the pharynx o Supplies sensation to the back of the tongue, back of the oral cavity and the oropharynx th 10 vagus o Arise from a line of filaments that arise from the lateral aspect of the medulla o Out of jugular foramen o Goes all the way to the abdomen o Role: to provide parasympathetic supply to the organs throughout the thorax and upper abdomen  Sensory and motor supply to larynx and pharynx o Trunk is thickened by ganglion o Goes all the way down the neck and to the abdomen o Branches  Pharyngeal branch  Enter wall of pharynx  Supply the superior and middle constrictor muscles, muscles of the palate except the tensor palati

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Superior laryngeal nerve  Goes down to the hypopharynx  Has an external and internal branch o Internal: Provides sensation to the hypopharynx, epiglottis, part that is above the vocal cords o External: supplies the cricothyroid muscle and the inferior constrictor muscle Recurrent laryngeal nerve  Goes motor supply to all the muscle of the larynx and provides sensation to the larynx below the vocal folds

11th accessory o Arise from the filaments of the spinal cord. Comes up through the foramen magnum and joins the 9th and 10th nerve o Out of jugular foramen o Motor nerve o Supplies the muscles  Sternocleidomastoid muscle  Trapezius muscle th 12 hypoglossal o Leaves via the hypoglossal canal o Motor nerve o Supplies all the muscles of the tongue and infrahyoid muscles

3.1.8 Spinal cord (cross section), spinal meninges, Dural sac 

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The main spinal cord only partly fills the spinal canal o 2 nerve filaments protrude form the main cord  Ventral aspect  Dorsal aspect  These form the spinal nerves Cord lies within the dura o Lined loosely by the arachnoid o Cord is covered by a firmly attached pia membrane Space between the cord and the arachnoid/dura o Is the subarachnoid space o Filled with CSF Space between the dura and the canal o Is the epidural space o Filled with fat, loose connective tissue and blood vessels Sleeve of dura = dural sack o Sack passes through the foramen magnum  Becomes continuous with the dura of the brain o Dural sack tapers to a point at the 2nd sacral segment Cord only fills up the first 2/3rd of the spine o The rest is the lumbar spine

3.1.9 spinal cord (from behind), nerve roots 

Cord is attached to the dura by

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o Denticulate ligaments o Triangle ligaments Spinal nerves arising o Rises from a small bundle of dorsal filaments  Unite to form the dorsal (sensory) root of a nerve o Rises from a small bundle of the ventral filaments o Unite to form the ventral (motor) root Lumbar spine has a large bundle of nerve roots filling up the dorsal sac o The corda equina  The nerves leave the canal 2 at a time all the way to the lower end of the sacrum Roots leave the dural sack and emerges from the intervertebral foramen o Has the dorasal and ventral roots o Thickening at the root of the nerve = dorsal root ganglion o As it emerges, it divides into  Posterior primary ramus  Pass backward to supply muscles and skin on the back  Anterior primary ramus  Emerge laterally and power everything else Brachial plexus o C5-T1 o Major nerves of upper extremities Lumbar and sacral plexus o L1-S3 o Nerves of lower extremities C8 has no corresponding vertebra

1.1.14 Nerves of the shoulder region: the brachial plexus 

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5 roots of the brachial plexus (these are the ventral rami of their subsequent vertebrae) o Top 2 roots join (C5/6) o Bottom 2 roots join (C8/T1) o Middle one (C7) stays alone) These create the 3 trunks o Upper o Middle o Lower  Trunks divide into anterior and posterior divisions Of the divisions o The upper two anterior divisions unite, lower stays alone o All posterior divisions unit They are now cords o Lateral o Medial o Posterior  Surround axillary artery Lateral cord divides into o Musculocutaneous nerve: supplies upper arm muscles

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o ½ of the median nerve Medial cord divides into o Ulnar nerve o ½ of the median nerve Posterior cord divides into o Axillary nerve: supply deltoid muscle and teres minor o Radial nerve o Subscapular nerves: subscapularis and teres major Muscles of the shoulder regions o Medial cord gives rise two the medial pectoral nerve o Lateral cord gives rise to the lateral pectoral nerve

Lumbar plexus     

Anterior primary rami of the T12 – L5 Femoral nerve Obturator nerve Gluteal Sciatic...