Anatomy Tables

neurulation process

1

Begins (3rd week)

What happens: Notochord signals induce Ectoderm

Results: CNS development starts

2

Neuroectoderm

What happens: Ectoderm differentiates

Results: Neural tissue forms

3

Neural plate

What happens: Thickening occurs

Results: Flat precursor

4

Folds fold

What happens: Edge elevates

Results: Neural folds

5

Neural grove

What happens: Midline depression

Results: Tube formation

6

Fusion

What happens: Folds fuse

Results: Neural tube forms

7

Week 4

What happens: Tube closed

Results: Brain + Spinal cord

Primary Vesicles - Week 4

Prosencephalon

Becomes: Forebrain

Function: Higher processing

Clinical Correlation: Holoprosencephaly - failure of forebrain to split

Mesencephalon

Becomes: Midbrain

Function: Reflexes

Clinical Correlation: Eye movement disorders

Rhombencephalon

Becomes: Hindbrain

Function: Vital functions (respiration, HR)

Clinical Correlation: Respiratory failure

Spinal cord

Becomes: Spinal cord

Function: Conduction

Clinical Correlation: Spina bifida

Secondary Vesicles - Week 5

Prosencephalon - Primary

Secondary - Telencephalon

Adult Structure - Cerebrum

Function - Cognition

Clinical - Lissencephaly - smooth brain, causes developmental delay, seizures

Prosencephalon - Primary

Secondary - Diencephalon

Adult Structure - Thalamus, Hypothalamus

Function - Relay

Clinical - Hormone imbalance

Mesencephalon - Primary

Secondary - Mesencephalon

Adult Structure - Midbrain

Function - Reflex

Clinical - Motor disorders

Rhombencephalon - Primary

Secondary - Metencephalon

Adult Structure - Pons , Cerebellum

Function - Coordination

Clinical - Ataxia

Rhombencephalon - Primary

Secondary - Myelencephalon

Adult Structure - Medulla

Function - Autonomic

Clinical - Resp failure

Spinal Cord

Stays spinal cord

Adult Structure - Spinal cord

Function - Reflex

Clinical - Paralysis

Cerebrum

Structures Comprising the Region :

Frontal , Parietal , Temporal , Occipital lobe , Basal nuclei , Cerebral cortex

Major Functions : Conscious thought, voluntary movement, sensation , language , memory

Major Features & Characteristics : Largest part of brain ; highly folded (gyri & sulci); divided into hemispheres; lateralization (left = language)

Diencephalon

Structures Comprising the Region:

Thalamus , Hypothalamus , Epithalamus (pineal gland)

Major Functions:

Sensory relay (thalamus); homeostasis & endocrine control (hypothalamus); circadian rhythm (pineal)

Major Features & Characteristics: Surrounds 3rd ventricle; connects nervous & endocrine systems; major autonomic control center

Brainstem

Structures Comprising the Region:

Midbrain , Pons , Medulla oblongata

Major Functions :

Vital functions (heart rate, breathing, BP); reflexes ; cranial nerve function

Major Features & Characteristics:

Connects brain to spinal cord; contains cranial nerve nuclei; essential for survival; damage often fatal

Cerebellum

Structures Comprising the Region:

Cerebellar , hemispheres , Vermis , Arbor vitae (tree like)

Major Functions:

Coordination of movement, balance, posture, motor learning

Major Features & Characteristics:

Does NOT initiate movement; smooths & fine-tunes motor activity

Highly folded; located posteriorly

Limbic System

Structures Comprising the Region:

Hippocampus , Amygdala , Cingulate gyrus

Major Functions:

Emotion, memory , formation , motivation , behavior

Major Features & Characteristics:

"Emotional brain"; links emotion with memory; involved in fear, reward, and learning

Cerebrum Key Notes

Thinking & voluntary control

Thalamus Key Notes

Sensory relay station (everything except smell)

Hypothalamus Key Notes

Homeostasis (temperature, hunger, hormones)

Brainstem Key Notes

Life support (breathing, heart rate)

Cerebellum Key Notes

Coordination (NOT strength or paralysis)

Limbic System Key Notes

Emotion + memory

Clinical Correlations

Cerebrum damage -> stroke (paralysis, aphasia)

Hypothalamus -> endocrine disorders, temp disregulation

Brainstem -> coma or death

Cerebellum -> ataxia, poor coordination

Hippocampus -> memory loss (Alzheimer's )

Amygdala -> altered fear / emotional response

Muscles of Facial Expression

ALL = CN VII (7) - facial nerve

Frontalis Muscle

Region:

Face

Action:

Raises eyebrows, wrinkles forehead

Innervation:

Facial nerve (CN VII)

Orbicularis Oculi

Region:

Face

Action:

Closes eyelids

Innervation:

CN VII

Orbicularis Oris

Region:

Face

Action:

Closes / protrudes lips

Innervation:

CN VII

Zygomaticus major

Region:

Face

Action:

Elevates mouth (smile)

Innervation:

CN VII

Buccinator

Region:

Face

Action:

Compresses cheek

Innervation:

CN VII

Risorius

Region:

Face

Action:

Draws mouth laterally (grimace)

Innervation:

CN VII

Levator labii superioris

Region:

Face

Action:

Elevates upper lip

Innervation:

CN VII

Depressor anguli oris

Region:

Face

Action:

Pulls mouth downward

Innervation:

CN VII

Mentalis

Region:

Face

Action:

Protrudes lower lip (pouting)

Innervation:

CN VII

Platysma

Region:

Neck

Action:

Tenses neck, depresses mandible

Innervation:

CN VII

Muscles of Mastication

ALL CN V3 - Trigeminal Nerve

Masseter

Region:

Head

Action:

Elevates mandible (closes jaw)

Innervation:

Trigeminal nerve (CN V3)

Temporalis

Region:

Head

Action:

Elevates & retracts mandible

Innervation:

CN V3

Medial pterygoid

Region:

Head

Action:

Elevates mandible

Innervation:

CN V3

Lateral pterygoid

Region:

Head

Action:

Protracts mandible, opens jaw

Innervation:

CN V3

Suprahyoid Muscles

Swallowing - mix - Trigeminal and Facial

Digastric (anterior belly)

Region:

Neck

Action:

Depresses mandible

Innervation:

CN V3 (Trigeminal)

Digastric (posterior belly)

Region:

Neck

Action:

Elevates hyoid

Innervation:

CN VII (Facial)

Mylohyoid

Region:

Neck

Action:

Elevates floor of mouth

Innervation:

CN V3 (Trigeminal)

Stylohyoid

Region:

Neck

Action:

Elevates hyoid

Innervation:

CN VII (Facial)

Geniohyoid

Region:

Neck

Action:

Moves hyoid anteriorly

Innervation:

C1 via CN XII

Infrahyoid Muscles

Stabilize Hyoid

Sternohyoid

Region:

Neck

Action:

Depresses hyoid

Innervation:

Cervical plexus (C1-C3)

Omohyoid

Region:

Neck

Action:

Depresses hyoid

Innervation:

Cervical plexus

Sternothyroid

Region:

Neck

Action:

Depresses larynx

Innervation:

Cervical plexus

Thyrohyoid

Region:

Neck

Action:

Elevates larynx

Innervation:

C1 via CN XII

Sternocleidomastoid (SCM)

Region:

Neck

Action:

Rotates head, flexes neck

Innervation:

Accessory Nerve (CN XI)

Trapezius

Region:

Neck/back

Action:

Elevates shoulders, extends neck

Innervation:

CN XI

Scalenes

Region:

Neck

Action:

Elevate ribs (breathing)

Innervation:

Cervical nerves (C3-C8)

Splenius capitis

Region:

Neck

Action:

Extends & rotates head

Innervation:

Cervical nerves

Semispinalis capitis

Region:

Neck

Action:

Extends head

Innervation:

Cervical nerves

Innervation Patterns

CN VII -> ALL facial expression muscles

CN V3 -> ALL mastication muscles

CN XI -> SCM + Trapezius

Cervical plexus -> most infrahyoid + deep neck muscles

Mixed Innervation -> digastric

CN I

Name:

Olfactory

Sensory or Motor:

Sensory

Key Functions:

Smell

Symptoms:

Anosmia

Clinical:

Loss early in Parkison's / Alzheimer's

CN II

Name:

Optic

Sensory or Motor:

Sensory

Key Functions:

Vision, visual fields

Symptoms:

Vision loss, APD

Clinical:

Bitempora; hemianopsia (pituitary tumor)

CN III

Name:

Oculomotor

Sensory or Motor:

M + PS

Key Functions:

Eye movement, pupil constriction, eyelid

Symptoms:

Down & out, ptosis, blown pupil

Clinical:

Aneurysm vs diabetic palsy

CN IV

Name:

Trochlear

Sensory or Motor:

Motor

Key Functions:

Down & in (superior oblique)

Symptoms:

Vertical diplopia

Clinical:

Head tilt away, stairs difficulty

CN V

Name:

Trigeminal

Sensory or Motor:

Both

Key Functions:

Face sensation, mastication

Symptoms:

Loss sensation, jaw deviates

Clinical:

Trigeminal neuralgia

CN VI

Name:

Abducens

Sensory or Motor:

Motor

Key Functions:

Abduct eye

Symptoms:

Eye medially deviated

Clinical:

Affected by increased ICP

CN VII

Name:

Facial

Sensory or Motor:

Both

Key Functions:

Facial expression, taste anterior 2/3

Symptoms:

Facial paralysis

Clinical:

UMN spares forehead

CN VIII

Name:

Vestibulocochlear

Sensory or Motor:

Sensory

Key Functions:

Hearing, balance

Symptoms:

Hearing loss, vertigo

Clinical:

Acoustic neuroma

CN IX

Name:

Glossopharyngeal

Sensory or Motor:

Both

Key Functions:

Taste posterior 1/3, gag afferent

Symptoms:

Loss gag, dysphagia

Clinical:

Rarely isolated

CN X

Name:

Vagus

Sensory or Motor:

Both

Key Functions:

Voice, swallowing, parasympathetic

Symptoms:

Hoarseness, uvula deviates away

Clinical:

Efferent gag reflex

CN XI

Name:

Accessory

Sensory or Motor:

Motor

Key Functions:

SCM, trapezius

Symptoms:

Shoulder droop

Clinical:

Atrophy, fasciculations

CN XII

Name:

Hypoglossal

Sensory or Motor:

Motor

Key Functions:

Tongue movement

Symptoms:

Tongue deviates toward lesion

Clinical:

Atrophy, fasciculations

Cranial Nerves - Skull openings - Muscle Groups

CN 1 (Olfactory)

Skull Opening:

Cribriform Plate

Main Function:

Smell

Clinical Correlation:

Ethmoid fracture

Classic Symptoms:

Anosmia, CSF leak

CN II (Optic)

Skull Opening:

Optic canal

Main Function:

Vision

Clinical Correlation:

Sphenoid tumor

Classic Symptoms:

Bitempora 1 hemianopsia

CN III (Oculomotor)

Skull Opening:

Superior orbital fissure

Muscle Group:

Extraocular muscles

Key Muscles:

Superior rectus

Inferior rectus

Medial rectus

Inferior oblique

Main Function:

Eye movement, pupil constriction

Clinical Correlation:

Aneurysm compression

Classic Symptoms:

"Down & out" eye, ptosis

CN IV (Trochlear)

Skull Opening:

Superior orbital fissure

Muscle Group:

Extraocular

Key Muscles:

Superior oblique

Main Function:

Eye looks down

Clinical Correlation:

Trauma

Classic Symptoms:

Vertical diplopia

CN V1 (Ophthalmic)

Skull Opening:

Superior orbital fissure

Muscle Group:

Sensory

Main Function:

Forehead sensation

Clinical Correlation:

Orbital injury

Classic Symptoms:

Loss of forehead sensation

CN V2 (Maxillary)

Skull Opening:

Foramen rotundum -> infraorbital foramen

Muscle Group:

Sensory

Main Function:

Midface sensation

Clinical Correlation:

Facial fracture

Classic Symptoms:

Numb cheek & upper lip

CN V3 (Mandibular)

Skull Opening:

Foramen ovale

Muscle Group:

Mastication muscles

Key Muscles:

Masseter

Temporalis

Pterygoids

Main Function:

Chewing

Clinical Correlation:

Mandible fracture

Classic Symptoms:

Jaw deviation

CN VI (Abducens)

Skull Opening:

Superior orbital fissure

Muscle Group:

Extraocular

Key Muscles:

Lateral rectus

Main Function:

Abducts eye

Clinical Correlation:

Increase ICP trauma

Classic Symptoms:

Medial deviation

CN VII (Facial)

Skull Opening:

Internal acoustic meatus -> stylomastoid foramen

Muscle Group:

Facial

Key Muscles:

Orbicularis oculi, oris

Zygomaticus

Buccinator

Main Function:

Facial expression, blinking

Clinical Correlation:

Bell palsy

Classic Symptoms:

Facial droop

CN VIII (Vestibulocohlear)

Skull Opening:

Internal acoustic meatus

Main Function:

Hearing, balance

Clinical Correlation:

Acoustic neuroma

Classic Symptoms:

Hearing Loss, vertigo

CN IX (Glossopharyngeal)

Skull Opening:

Jugular foramen

Muscle Group:

Pharyngeal

Key Muscles:

Stylopharyngeus

Main Function:

Swallowing, gag reflex

Clinical Correlation:

Brainstem lesion

Classic Symptoms:

Loss of gag reflex

CN X (Vagus)

Skull opening:

Jugular foramen

Muscle Group:

Pharynx / larynx

Key Muscles:

Pharyngeal constrictors

laryngeal muscles

Main Function:

Swallowing, voice

Clinical Correlation:

Tumor surgery

Classic Symptoms:

Hoarseness dysphagia

CN XI (Accessory)

Skull Opening:

Jugular foramen

Muscle Group:

Neck muscles

Key Muscles:

SCM, trapezius

Main Function:

Head rotation, shoulder elevation

Clinical Correlation:

Neck injury

Classic Symptoms:

Shoulder droop

CN XII (Hypoglossal)

Skull Opening:

Hypoglossal canal

Muscle Group:

Tongue Muscles

Key Muscles:

Intrinsic & extrinsic tongue

Main Function:

Tongue movement

Clinical Correlation:

Stroke, tumor

Classic Symptoms:

Tongue deviation