206 NERVOUS SYSTEM - under construction

General Introduction

From actual bodies almost all the ideas of anatomical theory developed, but to understand this theory it is easier to use lists and labelled diagrammatic PowerPoint images (in 206), which present a simplified view, and one that ignores anatomical variation from one person to another. The purpose of the anatomy lab is for you to find out what bodies are really like to the extent that we can do this once they are dead.

For using this material at the computer, some may work from the screen just clicking the links, but most find it easier to print a version to read along with the images.

Central Nervous System: Brain & Spinal Cord

NBAN 206 Module V . NERVOUS SYSTEM & SPECIAL SENSES . Lab structures assigned

BRAIN (Lesson 25)
- - frontal lobe - - occipital lobe - - central sulcus postcentral gyrus - - parietal lobe - - parieto-occipital sulcus - - calcarine fissure - - parietal lobe
pons - - medulla oblongata - - cerebellum - - cerebral aqueduct cerebral aqueduct spinal cord - -
corpus callosum - - interventricular foramen - - thalamus - - hypothalamus - - optic chiasma - - attachment of hypophysis or pituitary gland

olfactory bulb - - olfactory tract - - CN II (optic n.) - - mammillary bodies - - CN V (Trigeminal n.) - - Cn VIII (vestibulocochlear n) - - CN VII (facial n.) - - CN X (vagus n.) - - CN XII (hypoglossal n.) - - CN III (oculomotor n.) - - CN IV (trochlear n.) - - CN VI (abducens n.) - - pyramid of medulla - - CN IX (glossopharyngeal n.) - - olive CN XI (accessory spinal n.) - - longitudinal fissure - - occipital lobe - - cerebral cortex
interventricular foramen - - lateral ventricle - - third ventricle - - cerebral aqueduct - - fourth ventricle - -

pia mater - - subarachnoid space - - meningeal dura mater - - periosteal dura mater (not for spinal cord) - - falx cerebri - - tentorium cerebelli
superior sagittal sinus
- - internal jugular v. (in cervical region) - - common carotid a. - - internal carotid a. - - vertebral a. (in cervical region)
(internal carotid aa.)

Circle of Willis:-

  • anterior cerebral aa.
  • middle cerebral aa.
  • anterior communicating a.
  • posterior communicating aa.
  • basilar a.
  • (posterior cerebral aa)
    SPINAL CORD (Lesson 28)
    cervical enlargement - - lumbar enlargement - - dura mater - - filum terminale - - cauda equina

    ORGANS OF SPECIAL SENSE (Lesson 30) Use Guy Lesson 30 & Marieb (text, Ch. 8) for information.

    EYE Eye PowerPoint
    pupil - - iris - - lens - - sclera - - retina - - optic nerve - - cornea - - vitreous (use cow eye for this)

    external auditory canal - - tympanic membrane - - middle ear - - inner ear - - auditory tube - - ossicles:-
    malleus - - incus - - stapes
    semicircular canals - - cochlea (use model for this)

    Now for the actual images . Here, first we'll look at the wrappings and bony protection that allow the brain to be a very soft squishy structure.

    Brain & Cord relations with meninges and skeleton
    Note, from the small white circle with a 'nose', that the head is facing the frame's top. The skull cap has been carefully dissected away from the thick dura mater which is left intact enclosing the brain. The dura is attached to the inside of the skull, but has pulled away (artifact) at the yellow arrows. The broken turquoise line marks the midline where the dura protrudes down the Falx cerebri separating the hemispheres. . Skull open, brain in situ, Dura intact

    Here the head points right, and the Dura has been cut and peeled back, except along the midline. Now exposed are the convoluted gyri/ridges of the cerebral cortex. However, you are looking at the tight shiny Pia mater - a thin membrane tightly attched to the surface of the gyri. The space between the Dura and Pia is the Subarachnoid space where CSF accumulated. . Brain in situ, Dura peeled back

    This U Iowa picture from Drs Williams, Gluhbegovic, and Jew shows how the Meninges are arranged for the spinal cord. A Thin Pia covers the cord, and is enclosed in the thick Dura, with a Subarachnoid space in between. However, the Dura is mostly separated from the vertebral bone by epidural fat (#8 in the key) . U Iowa Meninges of cord, posterior

    This page depicts a sketch of the Falx and Tentorium cerebelli in position within the skull. Also shown are the sagittal and transverse sinuses, running within the dura. CAUTION - the page is on a commercial site from Bartelby's Books, which carries advertizements on the page, which may pop up after exiting. The figures that Bartelby appropriated are from an edition of Henry Gray's Anatomy of the Human Body no longer protected by copyright. . Bartelby-Gray Sketch shows Falx, Tentorium, & Dural Sinuses

    Another Henry Gray view of the Superior sagittal sinus . Bartelby-Gray Sketch shows Superior sagittal sinus

    This Henry Gray sketch of the sagittal skull shows how the several sinuses converge to inside the back of the skull. From here sinuses curve down to create and feed the jugular veins leaving the jugular foramina. Bartelby-Gray Sketch shows Sagittal Skull with sinuses

    Bartelby-Gray sketch showing how the transverse sinuses extend from the midline, aiming for the sigmoid sinuses leading down into the jugular veins. . Bartelby-Gray Sketch shows Transverse sinuses headed for jugular veins

    This dissection has removed the brain by cutting back the white dural Tentorium cerebelli to allow the cerebellum with the brainstem to be pulled up out of the skull's inferior fossa. In the tentorium, blood is visible and marked in the cut-open transverse and superior sagittal sinuses. . Skull with sinuses

    Note the change of orientation. Another interior-skull dissection. The tentorium is mostly present nwo, but has cuts on either side of the opening for the brainstem. The superior/anterior and middle cranial fossas are labelled. The small dark hole just caudal to the optic chiasm is where the pituitary gland/hypophysis lay. . Skull base, Tentorium, Basilar & Vertebral AAs

    On this view inside the base of the dry skull, the stepping of the three fossas can be seen, plus many small holes - foramina. The large one -Foramen magnum - is for the medulla and the vertbral AAs. The Carotid canal and Jugular foramen carry the corresponding artery and vein on each side. However, the jugular foramen also allows the exit of three cranial nerves. Feel into the Sella turcica where the pituitary gland was housed. What makes the Cribriform plate sieve-like are the many little holes for the separate bundles of the olfactory nerves, running from the olfactory mucosa up to the olfactory bulb above. . Skull base (bone alone)

    Dental hygienists make appreciate this Skull module from Calfornia State U at Chico. It illustrates the anatomical complexity of the skull. California State U, Chico, Schematic skull module

    Ventricular system
    This U Michigan view shows clearly the lateral ventricle (injected yellow) large, and curled down and back on itself as the inferior horn, but the 3rd and 4th ventricles are not easily to be made out . U Michigan Ventricles within hemisphere

    This U Michigan specimen has had the ventricular system injected with colored resin, and then the brain was dissolved away - the corrosion-cast technique. From the two views, the smaller 3rd and 4th ventricles and the connecting cerebral aqueduct can now be seen . U Michigan Ventricular system, cast, lateral & anterior

    This coronal/frontal cut in one of our brains shows the two lateral ventricles (one labelled) separated by the membranous septum pellucidum. The third ventricle is the midline slit (between right and left sides of the unmarked thalamus and hypothalamus) Brain, coronal, Temporal; lobe, Ventricles

    A less detailed version of the previous image Brain, coronal/frontal - ventricles

    This U Michigan view shows well the shape of the 4th ventricle situated between cerebellum and the pons & medulla below. The cerebral aqueduct extending up through the midbrain is clear, but unlabelled . U Michigan Fourth ventricle, medial

    Brain structures
    An orientation device is not given here, since the cerebellum with its many little folds (folia) indicates the posterior brain. The lateral fissure demarcates the frontal from the temporal lobe, but the parieto-occipital sulcus remains hidden on the brain's medial side. The lateral fissure goes almost all the way in toward the midline, so providing the route for the middle cerebral A to reach the lateral surface of the cortex . Lateral brain, cortical lobes

    This medial view is of the right half-brain with the cerebellum (& posterior) now on your right. Note the major divisions: cortex (cerebral); cerebellum; diencephalon; & brainstem. The parieto-occipital sulcus is well defined, and meeting it and subdividing the occipital lobe is the wavy calcarine sulcus, rather deep, and so sometimes called a 'fissure' . Brain, medial, major subdivisions

    The same mid-sagittal view as the last, but labelled for the two main parts of the diencephalon - thalamus and hypothalamus, and the three of the brainstem. In the lab, on an untagged half-brain, use your digits for measuring and defining. A thumb-tip covers the thalamus; a pinky tip, the hypothalamus. An index finger-tip defines the midbrain; a thumb tip, the pons; and two finger widths, the medulla . Brain - mid-sagittal

    U Michigan mid-sagittal brain is similarly labelled . U Michigan Brain, mid-sagittal

    U Iowa medial cortex. With the brainstem and cerebellum removed, the occipital and temporal lobes are visible. Without looking at the key, find the parieto-occipital and calcarine sulci. Note under the corpus callosum, the membranous septum pellucidum. This septum separates the right from left lateral ventricle. Just below the septum are two small interventricular foramina permitting CSF to pass from lateral ventricles into the 3rd ventricle . U Iowa Rt Cortex alone. medial

    U Michigan diencephalon and brainstem, enlarged, shows the two pairs of hillocks/bumps colliculi lying superiorly on the midbrain, which also encloses the cerebral aqueduct. # 1 - the pineal gland - is part of the diencephalon . U Michigan Diencephalon & Midbrain, sagittal

    U Iowa, Brain, coronal, through mammillary bodies. These bodies (3 28) are bumps on the ventral/inferior side of the hypothalmus. Above them extends the third ventricle. Find the Corpus callosum and under it the two large lateral ventricles with the choroid plexus. Note from the key that the thalamus can be subdivided into groups of nuclei. Find the white-matter internal capsule which separates the thalamus on each side from the more laterallly lying basal ganglia (also subdivided - #s 2, 11, 16, 22, & 23) U Iowa Brain, coronal section, hypothalamic level

    U Iowa Brain, coronal, through midbrain. Some thalamus is left under each lateral ventricle, but, below, the cut has gone through not the hypothalamus, but the midbrain, with the small hole of the cerebral aqueduct. Further ventrally, the cut extends down into the pons (# 19). Find the lateral fissure (unmarked) thatt separates the temporal and frontal lobes . U Iowa Brain, coronal section, midbrain level

    U Michigan Brainstem, inferior - Ignore # 1 . U Michigan Medulla, ventral, general

    U Michigan Medulla, inferior for cranial nerves- U Michigan Medulla, ventral, cranial nerves identified

    U Iowa ventral pons and medulla. Ignore items # 3, 6, 8, 10. Number 11 - the pyramidal decussation - is where motor fibers from each motor cortex cross the midline, interleaved, to reach the other side of the spinal cord (see next Fig). Result:- Right motor cortex controls movements on the body's left side, and vice versa ' U Iowa Pons & Medulla, ventral

    Bartelby-Gray schematic shows the long and crossed course of the motor pathway. For facial, eye and tongue movements, the motor pathways go down only as far as the opposite brainstem motor nuclei [not shown here] . Bartelby-Gray Schematic shows Motor Pathway

    U Iowa inferior brain. Find the olfactory bulb and olfactory tract. To the former structure come the bundles of cranial nerve I unseen here. Note the optic nerves connecting at the optic chiasm, from which the optic tracts run posteriorly/caudally. Close by, the oculomotor nerves (III) protrude from the hidden midbrain. Further from the midline, the large trigeminal nerves (V) derive from the pons. Further back, clusters of nerves extend from the ponto-medullary junction VI, VII, & VIII. and IX, X, and XII from the medulla . U Iowa Brain Inferior, with numbered sketch

    This interior view of the skull with the brain removed shows how removing it leaves behind torn cranial nerves and the pituitary stalk Skull fossas with attached dura, nerves, etc

    Spinal Cord
    U Iowa Thoracic cord in situ, posterior. Note how the roots extend down caudally in the spinal canal before leaving via the intervertebral formaina as spinal nerves. The small branch off the spinal nerve is the dorsal ramus. At the start of the spinal nerve, its slight bulge is the dorsal root ganglion . U Iowa Thoracic cord in situ, Posterior

    U Iowa Sacral cord. The two kidneys give an idea of how high up the cord ends as the tapering conus medullaris (#1). But extending on down the spinal canal are the sacral and lumbar dorsal and ventral roots, awaiting their turn to unite and exit via sacral or lumbar intervertebral foramina. Collectively these roots form the cauda equina . U Iowa Sacral cord & Cauda Equina

    U Iowa Meninges of cord, posterior

    U Michigan Cord in situ, posterior

    Arterial Vessels
    This Henry Gray Fig shows how the internal carotid A provides, as its internal branch, the major supply of blood to the brain; meanwhile, the vertebral A wiggles up through the transverse foramina of the cervical spine . Bartelby-Gray Sketch . Course of Rt vertebral & carotid arteries

    On this dried skull, the bony openings for the internal carotid AAs and jugular VVs are clear . Skull base: Carotid Canal & Jugular Foramen

    A U Michigan midsagittal head, with the major brain arteries highlighted. Note how the internal carotid A twists as it enters the skull, and that the anterior cerebral AAs run over the corpus callosum and quite far posteriorly despite their 'anterior' name . U Michigan MRI Head, sagittal, arteries marked

    On this dried skull, the bony openings for the internal carotid AAs and jugular VVs are clear . Skull base, Tentorium, Basilar & Vertebral AAs

    Brain, ventral. Arterial supply. Points to note are:
    (i) the left vertebral A is abnormally, and is the main feed to the basilar A
    (ii) the right vertebral A has been cut off at the start of the basilar A
    (iii) the rostral end of the basilar A has been cut, but its continuity with the two recurving posterior cerebral AAs can still be worked out
    (iv) here, the anterior communicating A has no length, but is only a kissing connection between the right and left anterior cerebral AAs
    (v) the major artery fed by the internal carotid A is the middle cerebral A, here hidden by the temporal lobe
    (vi) neither posterior communicating A is to be seen, so only some of the many elements of the Circle of Willis can be seen . Brain, ventral, Some Circle-of-Willis vessels

    Images for self-testing
    Temple U Brain, lateral,: Test yourself on gyri, sulci, & arterial supply

    US Military Radiology case Sagittal CT of brain: Test yourself

    U Iowa Brain mid-sagittal: test yourself

    Guide to Guy's Anatomy Lab on SBLC Computers

    1 If the computer asks for a User ID, type in the computer's own number, e.g., SBCL09. Leave 'Password' blank and hit enter.

    2 Choose (double-click) the icon 'Shortcut to HSC SBLC SOFTWARE'

    3 From the many icons, choose 'Anatomy Lab'

    4 Choose 'The Upper Limb'

    5 Choose 'Axial Skeleton and Muscle'

    6 Wait until the program starts, then, in the query box, type a single letter, number, or punctuation mark, and hit ENTER to proceed

    7 From now on, whenever a question is posed (quite often), anything typed in the box, followed by ENTER lets you progress

    8 To get out, use 'Back to Menu, 'Yes', followed by as many 'Quits' and 'Close' as it takes.

    9 When you return just to Guy's main menu, you can find the Appendicular Skeleton in the Upper and Lower Limb boxes.

    Once into Guy's Program, here below are the topics under the four principal icons, with the specific topics for this module numbered. The listed topics also show how anatomists approach a region: what skeletal elements are present? what nerves? what blood vessels? what muscles? what major organs/systems? etc

    Bones (3)				Axial Skeleton & Muscles (1)
    Muscles of the Hip			Bones of the Upper Limb (2)
    Muscles of the Thigh			Muscles of the Shoulder & Arm
    Muscles of the Leg & Foot		Muscles of the Forearm & Hand
    Nerves					Nerves
    Vessels					Vessels
    Activities & Review			Actions & Review
    The Skull				Muscles of the Abdomen & Digestive System
    The Brain				Peritoneum
    Ventricles & Circulation		Vessels & Nerves
    The Spinal Cord				Urinary & Male Reproductive System
    Cranial Nerves				Female Reproductive System
    Muscles & Actions			The Endocrine System
    Autonomic Nervous System		The Thorax
    Review					The Heart