Gross anatomy of human brain

DEPT OF NEUROSURGERY, CMCH, LUDHIANA

The Human Brain Master Watermark Image: http://williamcalvin.com/BrainForAllSeasons/img/bonoboLH-humanLH-viaTWD.gif

http://williamcalvin.com/BrainForAllSeasons/img/bonoboLH-humanLH-viaTWD.gif

Students will be able to describe the general structure of the Cerebrum and Cerebral Cortex.

• Students will be able to identify the Cerebrum, the Lobes of the Brain, the Cerebral Cortex, and its major regions/divisions.

• Students will be able to describe the primary functions of the Lobes and the Cortical Regions of the Brain.

Cerebrum -The largest division of the brain. It is divided into two hemispheres, each of which is divided into four lobes.

Cerebrum Cerebrum

Cerebellum



Cerebral Cortex

Cerebral Cortex

Cerebral Cortex - The outermost layer of gray matter making up the superficial aspect of the cerebrum.

http://www.bioon.com/book/biology/whole/image/1/1-6.tif.jpg


Cerebral Features:

• Sulci – Small grooves dividing the gyri

– Central Sulcus – Divides the Frontal Lobe from the Parietal Lobe

• Fissures – Deep grooves, generally dividing large regions/lobes of the brain

– Longitudinal Fissure – Divides the two Cerebral Hemispheres

– Transverse Fissure – Separates the Cerebrum from the Cerebellum

– Sylvian/Lateral Fissure – Divides the Temporal Lobe from the Frontal and Parietal Lobes

• Gyri – Elevated ridges “winding” around the brain.

Gyri (ridge)

Fissure

(deep groove)

Sulci (groove)



Longitudinal Fissure

Transverse Fissure

Sylvian/Lateral Fissure

Central Sulcus

http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg http://www.dalbsoutss.eq.edu.au/Sheepbrains_Me/human_brain.gif

Specific Sulci/Fissures:


http://www.dalbsoutss.eq.edu.au/Sheepbrains_Me/human_brain.gif

Frontal Parietal Occipital Temporal

* Note: Occasionally, the Insula is considered the fifth lobe. It is located deep to the Temporal Lobe.



The Frontal Lobe of the brain is located deep to the Frontal Bone of the skull.

(Investigation: Phineas Gage)

• It plays an integral role in the following functions/actions:

- Memory Formation

- Emotions

- Decision Making/Reasoning

- Personality

Investigation (Phineas Gage)

Modified from: http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg


Orbitofrontal Cortex – Site of Frontal Lobotomies

• Primary Motor Cortex (Precentral Gyrus) – Cortical site involved with controlling movements of the body.

• Broca’s Area – Controls facial neurons, speech, and language comprehension. Located on Left Frontal Lobe.

– Broca’s Aphasia – Results in the ability to comprehend speech, but the decreased motor ability (or inability) to speak and form words.

• Olfactory Bulb - Cranial Nerve I, Responsible for sensation of Smell

* Desired Effects:- Diminished Rage- Decreased Aggression- Poor Emotional Responses

* Possible Side Effects:- Epilepsy- Poor Emotional Responses- Perseveration (Uncontrolled, repetitive actions, gestures, or words)

Primary Motor Cortex/ Precentral Gyrus

Broca’s Area

Orbitofrontal Cortex

Olfactory Bulb


Regions

Investigation (Phineas Gage)


The Parietal Lobe of the brain is located deep to the Parietal Bone of the skull.

• It plays a major role in the following functions/actions:

- Senses and integrates sensation(s)

- Spatial awareness and perception(Proprioception - Awareness of body/ body parts in space and in relation to each other)



Primary Somatosensory Cortex (Postcentral Gyrus) – Site involved with processing of tactile and proprioceptive information.

• Somatosensory Association Cortex - Assists with the integration and interpretation of sensations relative to body position and orientation in space. May assist with visuo-motor coordination.

• Primary Gustatory Cortex – Primary site involved with the interpretation of the sensation of Taste.

Primary Somatosensory Cortex/ Postcentral Gyrus

Primary Gustatory Cortex

Somatosensory Association Cortex

Regions



The Occipital Lobe of theBrain is located deep to theOccipital Bone of the Skull.

• Its primary function is the processing, integration, interpretation, etc. of VISION and visual stimuli.



Primary Visual Cortex – This is the primary area of the brain responsible for sight -recognition of size, color, light, motion, dimensions, etc.

• Visual Association Area – Interprets information acquired through the primary visual cortex.

Primary Visual Cortex

Visual Association Area

RegionsModified from: http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg


The Temporal Lobes are located on the sides of the brain, deep to the Temporal Bones of the skull.

• They play an integral role in the following functions:

- Hearing- Organization/Comprehension of language

- Information Retrieval (Memory and Memory Formation)



Primary Auditory Cortex – Responsible for hearing

• Primary Olfactory Cortex – Interprets the sense of smell once it reaches the cortex via the olfactory bulbs. (Not visible on the superficial cortex)

• Wernicke’s Area – Language comprehension. Located on the Left Temporal Lobe.

- Wernicke’s Aphasia – Language comprehension is inhibited. Words and sentences are not clearly understood, and sentence formation may be inhibited or non-sensical.

Primary Auditory Cortex

Wernike’s Area

Primary Olfactory Cortex (Deep)Conducted from Olfactory Bulb

RegionsModified from: http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg

• Arcuate Fasciculus - A white matter tract that connects Broca’s Area and Wernicke’s Area through the Temporal, Parietal and Frontal Lobes. Allows for coordinated, comprehensible speech. Damage may result in:

- Conduction Aphasia - Where auditory comprehension and speech articulation are preserved, but people find it difficult to repeat heard speech.


Click the Region to see its Name

Korbinian Broadmann - Learn about the man who divided the Cerebral Cortex into 52 distinct regions: http://en.wikipedia.org/wiki/Korbinian_Brodmann


Lobes and Structures of the Brain

B. A.

C.

D. E.

F.

G.


Lobes and Structures of the Brain

B.

A. (groove)

C. (groove)

D. E.

F.

G.

B. Frontal Lobe

G. Parietal Lobe

F. Occipital Lobe

D. Temporal Lobe

A. Central Sulcus

(groove)

E. Transverse Fissure

C. Sylvian/Lateral Fissure


Cortical Regions

A.

B.

C.

D.

E. F.

G.

H.

I.

J.K.


Cortical Regions

A.

B.

C.

D.E. F.

G.

H.

I.

J.K.

A. Primary Motor Cortex/ Precentral Gyrus

B. Broca’s Area

C. Orbitofrontal Cortex

K. Primary Somatosensory Cortex/ Postcentral Gyrus

I. Primary Gustatory Cortex

J. Somatosensory Association Cortex

G. Primary Visual Cortex

H. Visual Association Area

E. Primary Auditory Cortex

F. Wernike’s Area

D. Primary Olfactory Cortex (Deep)


A: Primary Motor Cortex

* This graphic representation of the regions of the Primary Motor Cortex and Primary Sensory Cortex is one example of a HOMUNCULUS:

Homunculus

Q: Assuming this comical situation was factually accurate, what Cortical Region of the brain would these doctors be stimulating?

Copyright: Gary Larson

Ⅰ Olfactory nerve Ⅱ Optic nerve Ⅲ Oculomotor nerve Ⅳ Trochlear nerve Ⅴ Trigeminal nerve Ⅵ Abducent nerve Ⅶ Facial nerve Ⅷ Vestibulocochlear

nerve Ⅸ Glossopharyngeal

nerve Ⅹ Vagus nerve Ⅺ Accessory nerve Ⅻ Hypoglossal nerve

Sensory cranial nerves: contain only afferent (sensory) fibers ⅠOlfactory nerve ⅡOptic nerve Ⅷ Vestibulocochlear nerve

Motor cranial nerves: contain only efferent (motor) fibers Ⅲ Oculomotor nerve Ⅳ Trochlear nerve ⅥAbducent nerve Ⅺ Accessory nerv Ⅻ Hypoglossal nerve

Mixed nerves: contain both sensory and motor fibers--- ⅤTrigeminal nerve, Ⅶ Facial nerve, ⅨGlossopharyngeal nerve ⅩVagus nerve

N. Location of cell body and axon categories

Cranial exit

Terminal nuclei

Main action

Ⅰ Olfactory cells (SVA)

Cribrifomforamina

Olfactory bulb

Smell

Ⅱ Ganglion cells (SSA)

Optic canal

Lateral geniculate body

Vision

Ⅷ Vestibular ganglion(SSA)

Internal acoustic meatus

Vestibular nuclei

Equilibrium

Cochlear ganglion (SSA)

Cochlear nuclei

Hearing

Olfactory mucosa (SVA)→ Cribriform foramina → Olfactory bulb

Ganglion cell (SSA) → Optic canal → Lateral geniculate body

Vestibular ganglion(SSA) ↘ ↗ Vestibular nuclei Internal acoustic meatus Cochlear ganglion (SSA) ↗ ↘ Cochlear nuclei

N. Nucleus of origin and axon categories

Cranial exit Main action

Ⅲ Nucleus of oculomotor (GSE)

Superior orbital fissure

Motot to superior, inferior and medial recti; inferior obliquus; levator palpebrae superioris

Accessory nucleus of oculomotor (GVE)

Parasympathetic to sphincter pupillea and ciliary muscl

Ⅳ Nucleus of trochlear nerve (GSE)


Motor to superior obliquus

Ⅵ Nucleus of abducent nerve (GSE)


Motor to lateral rectus

Ⅺ Nucleus of accessory nerve (SVE)

Jugular foramen Motor to sternocleidomastoid and trapezius

Ⅻ Nucleus of hypoglossal nerve( GSE)

Hypoglossal canal Motot to muscles of tongue

Components General somatic efferent fibers (GSE) General visceral efferent fibers (GVE)

Main action － supplies Superior, inferior and medial recti; inferior obliquus; levator

palpebrae superioris Sphincter pupillea and ciliary muscle

Ciliary ganglion: lies between optic nerve and lateral rectus

Oculomotor nerve

Abducent nerve

Accessory nerve

Hypoglossal nerve

Oculamotor paralysis

Abducent nerve injury

Components of fibers SVE fibers: originate from motor nucleus

of trigeminal nerve, and supply masticatory muscles

GSA fibers: transmit facial sensation to sensory nuclei of trigeminal nerve, the GSA fibers have their cell bodies in trigeminal ganglion, which lies on the apex of petrous part of temporal bone

Branches Ophthalmic

nerve (Ⅴ1, sensory) leave the skull through the superior orbital fissure, to enter orbital cavity

Branches Frontal nerve:

Supratrochlear nerve Supraorbital nerve

Lacrimal nerve

Nasociliary nerve

Distribution: Sensation from

cerebral dura mater

Visual organ Mucosa of nose Skin above the eye

and back of nose

Maxillary nerve (Ⅴ2, sensory)

Leave skull through foramen rotundum

Branches Infraorbital nerve Zygomatic nerve

颧 Superior alveolar

nerve Pterygopalatine

nerve


cerebral dura mater Maxillary teeth Mucosa of nose and

mouth Skin between eye

and mouth

Mandibular nerve (Ⅴ3, mixed)

Leave the skull through the foramen ovale to enter the infratemporal fossa

Branches Auriculotemporal nerve

耳颞 Buccal nerve Lingual nerve Inferior alveolar nerve

Nerve of masticatory

muscles


cerebral dura mater Teeth and gum of lower

jaw Mucosa of floor of

mouth Anterior 2/3 of tongue Skin of auricular and

temporal regions and below the mouth

Motor to masticatory muscles, mylohyoid, and anterior belly of digastric

Components of fibers SVE fibers originate from nucleus of facial nerve, and

supply facial muscles GVE fibers derived from superior salivatory nucleus

and relayed in pterygopalatine ganglion and submandibular ganglion. The postganglionic fibers supply lacrimal, submandibular and sublingual glands

SVA fiber from taste buds of anterior two-thirds of tongue which cell bodies are in the geniculate ganglion of the facial nerve and end by synapsing with cells of nucleus of solitary tract

GSA fibers from skin of external ear

Course: leaves skull through internal acoustic meatus, facial canal and stylomastoid foramen, it then enters parotid gland where it divides into five branches which supply facial muscles

Branches within the facial canal Chorda tympani : joins lingual branch of mandibular nerve

To taste buds on anterior two-thirds of tongue

Relayed in submandibular ganglion, the postganglionic fibers supply submandibular and sublingual glands

Greater petrosal nerve: GVE fibers pass to pterygopalatine ganglion 翼腭神经节 and there relayed through the zygomatic and lacrimal nerves to lacrimal gland

Stapedial nerve : to stapedius

Branches outside of facial canal

Temporal Zygomatic Buccal Marginal mandibular Cervical

Pterygopalatine ganglion : lies in pterygopalatine fossa under maxillary nerve

Submandibular ganglion : lies between lingual nerve and submandibular gland

Injury to the facial nerve

Components of fibers SVE fibers: originate from nucleus ambiguus, and

supply stylopharygeus GVE fibers: arise from inferior salivatory nucleus

and ralyed in otic ganglion, the postganglionic fibers supply parotid gland

SVA fibers: arise from the cells of inferior ganglion, the central processes of these cells terminate in nucleus of solitary tract, the peripheral processes supply the taste buds on posterior third of tongue

GVA fibers: visceral sensation from mucosa of posterior third of tongue, pharynx, auditory tube and tympanic cavity, carotid sinus and glomus, and end by synapsing with cells of nucleus of solitary tract

GSA fibers: sensation from skin of posterior surface of auricle and

Course: leaves the skull via jugular foramen

Branches Lingual branches : to taste buds and mucosa of

posterior third of tongue Pharyngeal branches : take part in forming the pharyngeal

plexus Tympanic nerve : GVE fibers via tympanic and lesser

petrosal nerves to otic ganglion, with postganglionic fibers via auriculotemporal (Ⅴ3) to parotid gland

Carotid sinus branch : innervations to both carotid sinus and glomus

Others: tonsillar and stylophayngeal branches

Otic ganglion : situated just below foramen ovale

components of fibers GVE fibers: originate from dorsal nucleus

of vagus nerve, synapse in parasympathetic ganglion, short postganglionic fibers innervate cardiac muscles, smooth muscles and glands of viscera

SVE fibers: originate from ambiguus, to muscles of pharynx and larynx

GVA fibers: carry impulse from viscera in neck, thoracic and abdominal cavity to nucleus of solitary tract

GSA fiber: sensation from auricle, external acoustic meatus and cerebral dura mater

Course Exits the skull from jugular foramen Descends in the neck in carotid sheath

between internal (or common) carotid artery and internal jugular vein

Right vagus nerve Enter thoracic inlet on right side of

trachea Travels downward posterior to right

brachiocephalic vein and superior vena cava

Passes posterior to right lung root Forms posterior esophageal plexus Forms posterior vagal trunk at

esophageal hiatus where it leaves thorax and passes into abdominal cavity, then divides into posterior gastric and celiac branches

Left vagus nerve Enter thoracic inlet between left

common carotid and left subclavian arteries, posterior to left brachiocephalic vein

Crosses aortic arch where left recurrent laryngeal nerve branches off

Passes posterior to left lung root Forms anterior esophageal plexus Forms anterior vagal trunk at

esophageal hiatus where it leaves thorax and passes into abdominal cavity , then divides into anterior gastric and hepatic branches

Branches in neck Superior laryngeal nerve: passes

down side of pharynx and given rise to Internal branch, which pierces thyrohyoid

membrane to innervates mucous membrane of larynx above fissure of glottis

External branch, which innervates cricothyroid

Cervical cardiac branches : descending to terminate in cardiac plexus

Others: auricular, pharyngeal and meningeal branches

Superior laryngeal nerve

External branch

Internal branch

Branches in thorax Recurrent laryngeal nerves

Right one hooks around right subclavian artery, left one hooks aortic arch

Both ascend in tracheo-esophageal groove

Nerves enter larynx posterior to cricothyroid joint, the nerve is now called inferior laryngeal nerve

Innervations: laryngeal mucosa below fissure of glottis , all laryngeal laryngeal muscles except cricothyroid

Bronchial and esophageal branches

Branches in abdomen Anterior and posterior

gastric branches Run close to lesser

curvature and innervate anterior and posterior surfaces of stomach

As far as pyloric antrum to fan out into branches in a way like the digits of a crow’s foot to supply pyloric part

Hepatic branches: join hepatic plexus and then supply liver and gallbladder

Celiac branches: send branches to celiac plexus to be distributed with sympathetic fibers to liver, pancreas, spleen, kidneys, intestine as far as left colic flexure

"Men ought to know that from nothing else but the brain come joys, delights, laughter and sports, and sorrows, griefs, despondency, and lamentations.

Hippocrates (460 BC – ca. 370 BC)

Health & Medicine

Gross anatomy of human brain