Cardiac cycle

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The Cardiac Cycle

The cardiac cycle refers to the complete sequence of mechanical and electrical events that repeats with every heartbeat. At a heart rate of 72 beats/min, one cycle lasts approximately 0.833 seconds (duration = 60 / heart rate). - Guyton and Hall Textbook of Medical Physiology

Initiation

Each cycle is triggered by a spontaneous action potential in the sinoatrial (SA) node, located in the superior lateral wall of the right atrium near the opening of the superior vena cava. The impulse travels rapidly through both atria, then passes through the AV node into the ventricles. A delay of >0.1 second at the AV node allows the atria to contract first, acting as "primer pumps" that top up the ventricles before powerful ventricular contraction begins. - Guyton & Hall

Overview Diagram (Costanzo Physiology)

Cardiac cycle diagram showing the 7 phases with pressure, volume, venous pulse, and ECG

Fig. 4.25 - The cardiac cycle with all 7 phases (A-G), left ventricular/atrial/aortic pressures, ventricular volume, venous pulse, and ECG. - Costanzo Physiology 7th Edition

The Seven Phases (Costanzo Classification)

The cycle is most conveniently divided into 7 phases. Here is a complete summary:

Phase	Name	ECG Event	Valves	Heart Sound	Key Events
A	Atrial Systole	P wave / PR interval	Mitral open	S4 (if present)	Atria contract; final ~20% of ventricular filling
B	Isovolumetric Ventricular Contraction	QRS complex	Mitral closes	S1	Ventricular pressure rises sharply; all valves closed; volume constant
C	Rapid Ventricular Ejection	ST segment	Aortic valve opens	-	Most of stroke volume ejected; ventricular volume drops rapidly
D	Reduced Ventricular Ejection	T wave	-	-	Ejection slows; ventricular volume reaches minimum (ESV)
E	Isovolumetric Ventricular Relaxation	After T wave	Aortic valve closes	S2	Ventricular pressure falls; all valves closed; volume constant
F	Rapid Ventricular Filling	-	Mitral valve opens	S3 (if present)	Ventricles fill passively; volume rises rapidly
G	Reduced Ventricular Filling (Diastasis)	-	-	-	Slow filling; pressure equalizes between atrium and ventricle

Table adapted from Costanzo Physiology 7th Edition, Table 4.5

Detailed Phase-by-Phase Description

Phase A - Atrial Systole

Atrial contraction is triggered by the P wave on the ECG. The mitral valve is already open (from the previous cycle), so atrial contraction forces an additional bolus of blood into the relaxed left ventricle. This produces a small "blip" in left ventricular pressure and appears as the a wave on the jugular venous pulse (JVP). At rest, atrial contraction contributes <20% of stroke volume; during heavy exercise, this can rise to 40%. The fourth heart sound (S4), if audible, coincides with atrial contraction and reflects a stiff, non-compliant ventricle (e.g., in ventricular hypertrophy). - Costanzo; Medical Physiology (Boron & Boulpaep)

Phase B - Isovolumetric Ventricular Contraction

The QRS complex marks ventricular depolarization and the start of ventricular contraction. As left ventricular pressure rises and exceeds left atrial pressure, the mitral valve closes - generating the first heart sound (S1). S1 may be split because the mitral valve closes slightly before the tricuspid valve. All valves are now closed, so ventricular volume is constant (isovolumetric) while pressure rises steeply. - Costanzo

Phase C - Rapid Ventricular Ejection

When left ventricular pressure exceeds aortic pressure (~80 mmHg diastolic), the aortic valve opens. Blood is rapidly ejected into the aorta along the pressure gradient. Ventricular pressure rises to its maximum (~120 mmHg systolic) and aortic pressure rises in parallel. Most of the stroke volume is ejected during this brief phase. Ventricular volume falls dramatically. Simultaneously, the left atrium begins refilling from the pulmonary veins. - Costanzo

Phase D - Reduced Ventricular Ejection

The T wave on the ECG marks ventricular repolarization. Ventricular contractile force wanes, so ejection slows. Although the aortic valve is still open and blood continues to enter the aorta, blood "runs off" into the arterial tree faster than it is being added, so aortic pressure begins to fall. Ventricular volume reaches its minimum, known as end-systolic volume (ESV), which is approximately 50 mL at rest. - Costanzo; Medical Physiology

Phase E - Isovolumetric Ventricular Relaxation

When ventricular pressure falls below aortic pressure, the aortic valve closes, generating the second heart sound (S2). The aortic valve closes slightly before the pulmonic valve; during inspiration, the pulmonic valve closure is delayed (increased right ventricular filling via Frank-Starling) producing physiological splitting of S2. All valves are again closed. Ventricular pressure falls rapidly while volume remains constant. - Costanzo

Phase F - Rapid Ventricular Filling

When ventricular pressure falls below left atrial pressure, the mitral valve opens. Blood flows rapidly and passively from atrium to ventricle down the pressure gradient, increasing ventricular volume quickly. The third heart sound (S3) may be heard at the start of this phase, caused by sudden deceleration of blood filling the ventricle. S3 is normal in children and young adults; in older adults it suggests ventricular dysfunction (e.g., dilated cardiomyopathy). - Costanzo

Phase G - Reduced Ventricular Filling (Diastasis)

Filling slows as ventricular and atrial pressures equalize. Both chambers are at relatively low pressure with the mitral valve wide open, and only minimal flow occurs between them - driven by the slightly higher pressure in the pulmonary veins. This "quiet" period ends when the P wave fires and the next atrial systole begins the cycle anew. - Medical Physiology (Boron & Boulpaep)

Pressure and Volume Key Values (Left Heart at Rest)

Parameter	Approximate Value
End-diastolic volume (EDV)	~120-130 mL
End-systolic volume (ESV)	~50 mL
Stroke volume (EDV - ESV)	~70-80 mL
Ejection fraction (SV/EDV)	~55-65%
Peak LV systolic pressure	~120 mmHg
LV diastolic pressure	~5-12 mmHg
Aortic diastolic pressure	~80 mmHg
Duration at HR 72 bpm	~0.83 s

ECG-to-Mechanical Event Correlations

ECG Event	Mechanical Correlate
P wave	Atrial depolarization → atrial contraction begins
PR interval	AV nodal delay (allows atrial emptying before ventricular contraction)
QRS complex	Ventricular depolarization → isovolumetric contraction begins
ST segment	Ventricular plateau (depolarized); rapid ejection occurring
T wave	Ventricular repolarization → ejection slowing, then aortic valve closes

Heart Sounds Summary

Sound	Timing	Cause	Clinical Note
S1 ("lub")	Start of ventricular systole	Closure of mitral + tricuspid valves	Heard best at apex (mitral) or lower left sternal border (tricuspid)
S2 ("dub")	End of ventricular systole	Closure of aortic + pulmonic valves	A2 before P2; splits with inspiration
S3	Early diastole (rapid filling)	Sudden deceleration of filling blood	Normal in youth; pathological in adults (ventricular failure)
S4	Late diastole (atrial kick)	Atrial contraction against stiff ventricle	Always pathological in adults; heard in LVH, hypertension

Effect of Heart Rate on Cycle Duration

When heart rate increases, diastole is disproportionately shortened compared to systole. At 72 bpm, systole comprises ~40% of the cycle. At three times the normal rate, systole occupies ~65% of the cycle. This is why very high heart rates can impair ventricular filling and reduce cardiac output - the heart does not have enough time to fill completely. - Guyton & Hall

Jugular Venous Pulse Waves

The JVP reflects atrial pressure changes and has three upward deflections:

a wave: atrial contraction (end of diastole)
c wave: tricuspid valve closure / bulging into atrium at start of systole
v wave: atrial filling against a closed tricuspid valve during ventricular systole

Sources:

Guyton and Hall Textbook of Medical Physiology
Costanzo Physiology, 7th Edition
Medical Physiology (Boron & Boulpaep)
Morgan & Mikhail's Clinical Anesthesiology, 7e

Create a visual study guide or poster diagram of the 7 cardiac cycle phases

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Medical study poster: "The 7 Phases of the Cardiac Cycle" - a clean, professional physiology diagram with a dark navy blue background and bright colors. At the top, a bold white title "THE CARDIAC CYCLE - 7 Phases". Below the title, a horizontal timeline bar divided into two main sections: "SYSTOLE" (highlighted in warm red/orange) covering phases B, C, D and "DIASTOLE" (highlighted in cool blue) covering phases E, F, G, A. The main body contains 7 color-coded phase cards arranged in a circular/sequential flow (like a clock going A→B→C→D→E→F→G→A), each card with: Phase A - ATRIAL SYSTOLE - purple card: "P wave on ECG | Mitral valve OPEN | Atria contract | Final ventricular filling | S4 heart sound" Phase B - ISOVOLUMETRIC VENTRICULAR CONTRACTION - red card: "QRS complex | Mitral valve CLOSES → S1 | All valves CLOSED | Volume constant | Pressure rises sharply" Phase C - RAPID VENTRICULAR EJECTION - orange card: "ST segment | Aortic valve OPENS | Most stroke volume ejected | LV pressure peaks ~120 mmHg | Volume drops fast" Phase D - REDUCED VENTRICULAR EJECTION - yellow card: "T wave | Aortic valve still open | Ejection slows | ESV reached (~50mL) | Aortic pressure starts falling" Phase E - ISOVOLUMETRIC VENTRICULAR RELAXATION - green card: "After T wave | Aortic valve CLOSES → S2 | All valves CLOSED | Volume constant | Pressure falls rapidly" Phase F - RAPID VENTRICULAR FILLING - teal card: "Mitral valve OPENS | Passive ventricular filling | Volume rises fast | S3 heart sound | Low pressure" Phase G - REDUCED VENTRICULAR FILLING (DIASTASIS) - blue card: "Mitral still open | Minimal flow | Pressure equalizes | Quiet period | Ends with next P wave" Below the circular flow, a simplified Wiggers diagram strip showing: aortic pressure curve, left ventricular pressure curve, and ECG trace (P-QRS-T) aligned with the phases A through G marked with vertical dashed lines. Bottom row: a quick reference table showing Heart Sounds: S1=Mitral closes (B), S2=Aortic closes (E), S3=Rapid filling (F), S4=Atrial kick (A). Key volumes: EDV=130mL, ESV=50mL, SV=80mL, EF=60%. Clean medical education style, white text on colored cards, clear arrows showing cycle direction, bold phase letters.

The 7 Phases of the Cardiac Cycle - Visual Study Poster

Here is your cardiac cycle study poster. It covers:

7 color-coded phase cards (A through G) arranged in sequential flow with phase names, ECG correlates, valve events, and key pressures/volumes
Systole vs. Diastole division clearly marked
Wiggers-style diagram strip at the bottom aligning aortic pressure, LV pressure, and ECG with the phases
Heart sounds quick reference (S1-S4) and key volume values (EDV, ESV, SV, EF)

A quick recap of the flow:

A (Atrial systole) → B (Isovolumetric contraction, S1) → C (Rapid ejection) → D (Reduced ejection) → E (Isovolumetric relaxation, S2) → F (Rapid filling, S3) → G (Diastasis) → back to A

prepare me the course of glossopharyngeal nerve using flowchart

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Professional medical anatomy flowchart poster on a deep navy blue background titled "GLOSSOPHARYNGEAL NERVE (CN IX) - Course & Distribution" in large bold white text at the top. The flowchart flows TOP to BOTTOM with color-coded boxes connected by thick arrows. Layout is a central vertical spine with branches going left and right. --- TOP SECTION: NUCLEI (dark purple boxes) --- Three purple boxes side by side labeled: 1. "NUCLEUS AMBIGUUS (Rostral Medulla)" - Motor nucleus - Branchial Efferent (BE) 2. "INFERIOR SALIVATORY NUCLEUS (Medulla)" - Parasympathetic - General Visceral Efferent (GVE) 3. "NUCLEUS TRACTUS SOLITARIUS" - Taste (SA) + Visceral Afferent (GVA) | "SPINAL NUCLEUS of CN V" - Somatic Afferent (GSA) Arrow DOWN labeled "Nerve fibers exit brainstem DORSOLATERAL to inferior olive" --- GANGLIA BOX (orange) --- "SUPERIOR GANGLION + INFERIOR (PETROSAL) GANGLION" - Located at Jugular Foramen - Cell bodies of afferent neurons Arrow DOWN labeled "Exits skull via JUGULAR FORAMEN" --- JUGULAR FORAMEN (bright yellow box) --- "JUGULAR FORAMEN - Exits skull with CN X (Vagus) and CN XI (Accessory)" Arrow DOWN --- DESCENT IN NECK (teal box) --- "Descends between INTERNAL JUGULAR VEIN and INTERNAL CAROTID ARTERY - Deep to styloid process and styloid muscles - Passes between internal and external carotid arteries - Curves around lateral border of STYLOPHARYNGEUS muscle" From this box, THREE branches diverge LEFT and RIGHT with arrows: BRANCH LEFT 1 (red box): "TYMPANIC BRANCH (Jacobson's Nerve) - Enters middle ear via tympanic canaliculus - Forms TYMPANIC PLEXUS on promontory of middle ear - Sensory: middle ear, mastoid air cells, pharyngotympanic tube mucosa - Continues as LESSER PETROSAL NERVE → OTIC GANGLION (below foramen ovale) - Postganglionic via AURICULOTEMPORAL NERVE (V3) → PAROTID GLAND (secretomotor)" BRANCH RIGHT 1 (green box): "CAROTID SINUS BRANCH (Nerve of Hering) - To carotid bifurcation - CAROTID SINUS: baroreceptor (blood pressure) - CAROTID BODY: chemoreceptor (O2/CO2) - Reflexes: respiratory + cardiovascular via vagal nucleus connection" BRANCH LEFT 2 (blue box): "MUSCULAR BRANCH - STYLOPHARYNGEUS muscle (only muscle supplied by CN IX) - Only branchial efferent branch - Derived from 3rd pharyngeal arch" BRANCH RIGHT 2 (purple box): "PHARYNGEAL BRANCHES - Joins vagus + sympathetic to form PHARYNGEAL PLEXUS - Sensory: mucosa of oropharynx, palatine tonsils - Afferent limb of GAG REFLEX" Arrow DOWN from teal box: --- TERMINAL DISTRIBUTION (gold box) --- "Passes DEEP TO HYOGLOSSUS MUSCLE - Reaches posterior tongue and palatine tonsil region" Two final branches: LEFT (pink box): "TONSILLAR BRANCHES - Sensory: palatine tonsils, soft palate, fauces" RIGHT (orange box): "LINGUAL BRANCHES - TASTE: posterior 1/3 of tongue (Special Afferent - SA) - GENERAL SENSATION: posterior 1/3 of tongue, vallate papillae (GSA)" --- BOTTOM SUMMARY TABLE --- A clean white table with 4 columns: "Fiber Type | Component | Distribution | Function" Row 1: BE | Branchial Efferent | Stylopharyngeus | Elevates pharynx/larynx during swallowing Row 2: GVE (para) | Preganglionic → Otic ganglion | Parotid gland via auriculotemporal | Salivary secretion Row 3: GVA | Visceral Afferent | Carotid body & sinus | Chemo/baroreception reflexes Row 4: GSA | General Somatic | Post. tongue, tonsil, pharynx, middle ear | Touch, pain, temperature Row 5: SA | Special Afferent (Taste) | Posterior 1/3 tongue | Taste sensation All boxes have white text, clean sans-serif font. Arrows are bright white with arrowheads. Color coding legend at bottom right corner. Clean medical education style, no clutter.

Glossopharyngeal Nerve CN IX - Course and Distribution Flowchart

Here is your CN IX flowchart poster. Below is a full written companion to go with it:

Course of the Glossopharyngeal Nerve (CN IX)

Fiber Types (5 components)

Fiber	Type	Function
BE	Branchial Efferent	Motor to stylopharyngeus
GVE	General Visceral Efferent (parasympathetic)	Secretomotor to parotid gland
GVA	General Visceral Afferent	Carotid body & sinus reflexes
GSA	General Somatic Afferent	Sensation - posterior tongue, tonsil, pharynx, middle ear
SA	Special Afferent (taste)	Taste from posterior 1/3 of tongue

Step-by-Step Course

1. Nuclei (Medulla)

Nucleus ambiguus (rostral) - motor origin
Inferior salivatory nucleus - parasympathetic preganglionic origin
Nucleus tractus solitarius - receives taste and visceral afferents
Spinal trigeminal nucleus - receives somatic pain/temperature

2. Brainstem Exit Fibers emerge dorsolateral to the inferior olive on the lateral medulla.

3. Ganglia Superior ganglion and inferior (petrosal) ganglion sit at the jugular foramen - contain cell bodies of afferent neurons.

4. Jugular Foramen Exits the skull alongside CN X (vagus) and CN XI (accessory).

5. Descent in the Neck Passes between the internal jugular vein and internal carotid artery, deep to the styloid process. It then curves around the lateral border of the stylopharyngeus muscle, passing between the internal and external carotid arteries, before travelling deep to hyoglossus towards the tongue base.

Branches & Their Distribution

Branch	Where Given Off	Distribution
Tympanic nerve (Jacobson's nerve)	At jugular foramen	Middle ear mucosa, mastoid air cells, pharyngotympanic tube; continues as lesser petrosal nerve → otic ganglion → parotid gland via auriculotemporal nerve (V3)
Carotid sinus branch (Nerve of Hering)	In neck	Carotid sinus (baroreceptor) and carotid body (chemoreceptor); mediates cardiorespiratory reflexes
Muscular branch	In neck	Stylopharyngeus - the ONLY muscle supplied by CN IX (3rd pharyngeal arch derivative)
Pharyngeal branches	In neck	Joins vagus + sympathetics to form pharyngeal plexus; sensory to oropharynx; afferent limb of gag reflex
Tonsillar branches	Terminal	Sensory to palatine tonsils, soft palate, fauces
Lingual branches	Terminal	Taste (SA) + general sensation (GSA) from posterior 1/3 of tongue and vallate papillae

Key Anatomical Relationships

Deep to styloid process and styloid muscles in the upper neck
Between internal and external carotid arteries as it descends
Curves around lateral border of stylopharyngeus
Deep to hyoglossus to reach tongue base

Clinical Correlate

Glossopharyngeal neuralgia - paroxysmal stabbing pain in the posterior tongue, tonsillar fossa, pharynx, or ear, triggered by swallowing/yawning. In severe cases, simultaneous vagal compression can trigger bradycardia or asystole.

Sources: Gray's Anatomy for Students; Bradley and Daroff's Neurology in Clinical Practice; Scott-Brown's Otorhinolaryngology

preprepare the same for spinal accessory nerve and hypoglossal nerve

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Professional medical anatomy flowchart poster, dark navy blue background. Title at top in large bold white text: "SPINAL ACCESSORY NERVE (CN XI) - Course & Distribution" Subtitle below: "Fiber Type: Branchial Efferent (BE) only - Pure MOTOR nerve" The flowchart flows TOP to BOTTOM with color-coded boxes and thick white arrows. --- BOX 1 (dark purple, top center) --- "NUCLEUS - SPINAL ACCESSORY NUCLEUS Upper 5 segments of Cervical Spinal Cord (C1-C5) Motor neurons in anterior horn (lateral group) NOT in the brainstem" White arrow DOWN labeled "Rootlets exit LATERAL surface of spinal cord" --- BOX 2 (indigo) --- "ASCENDING THROUGH SPINAL CANAL Rootlets join and ascend within the spinal canal Pass posterior to the dentate ligament Enter cranial cavity through FORAMEN MAGNUM" White arrow DOWN labeled "Enters posterior cranial fossa" Note box to the right (small, gray): "CRANIAL ROOT: A few rootlets from caudal medulla oblongata join briefly but immediately re-join CN X (vagus) → supplies pharyngeal muscles via vagus. NOT considered true CN XI." --- BOX 3 (teal) --- "POSTERIOR CRANIAL FOSSA Crosses posterior cranial fossa Joins with cranial rootlets briefly" White arrow DOWN labeled "Exits skull" --- BOX 4 (bright orange, wide) --- "JUGULAR FORAMEN Exits skull with CN IX (glossopharyngeal) and CN X (vagus) [Note: most posterior of the three]" White arrow DOWN --- BOX 5 (green) --- "DESCENT IN NECK - PHASE 1 Descends medial to internal jugular vein (IJV) Emerges between IJV and internal carotid artery Passes ANTERIOR BORDER of STERNOCLEIDOMASTOID (SCM) Relation to IJV: passes anterior to it in 70%, posterior in 27%, through it in 3% of cases" BRANCH LEFT (red box): "BRANCH TO SCM Motor branches to undersurface of SCM Arise ~4 cm below mastoid tip insertion Nerve pierces SCM (82%) or passes posterior to it (18%) ↓ INNERVATES: Sternocleidomastoid muscle" --- BOX 6 (blue) --- "POSTERIOR TRIANGLE OF NECK After SCM, nerve continues OBLIQUELY downward Crosses posterior triangle within investing layer of cervical fascia Lies between fascia crossing SCM and trapezius SUPERFICIAL location → vulnerable to injury Receives proprioceptive contributions from C2, C3 (cervical plexus)" White arrow DOWN --- BOX 7 (gold) --- "TRAPEZIUS MUSCLE Reaches anterior border of trapezius ~2-4 cm above clavicle, passes under/pierces trapezius Continues on DEEP SURFACE of trapezius ↓ INNERVATES: Trapezius muscle (upper, middle, lower fibres)" --- BOTTOM SECTION: Two side-by-side summary boxes --- LEFT (red): "MUSCLES INNERVATED 1. STERNOCLEIDOMASTOID (SCM) - Ipsilateral head rotation - Contralateral head tilt - Neck flexion 2. TRAPEZIUS - Shoulder elevation - Scapular retraction/rotation - Arm abduction above 90°" RIGHT (orange): "CLINICAL: CN XI INJURY 'Eleventh Nerve Syndrome': • Shoulder drooping • Inability to fully abduct shoulder (>90°) • Aberrant scapular rotation (winging) • Dull aching shoulder pain • Atrophy of trapezius Cause: neck dissection, posterior triangle surgery Test: shrug shoulder + abduct arm against resistance" At very bottom, a small note box: "Sources: Gray's Anatomy for Students | Cummings Otolaryngology | Bradley & Daroff's Neurology" All boxes white text, clean sans-serif font, clear labeled arrows, professional medical education style.

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Professional medical anatomy flowchart poster, dark navy blue background. Title at top in large bold white text: "HYPOGLOSSAL NERVE (CN XII) - Course & Distribution" Subtitle: "Fiber Type: General Somatic Efferent (GSE) only - Pure MOTOR nerve" The flowchart flows TOP to BOTTOM with color-coded boxes and thick white arrows. --- BOX 1 (dark purple, top center) --- "NUCLEUS - HYPOGLOSSAL NUCLEUS Location: Ventrolateral floor of 4th ventricle (medulla oblongata) Landmark: Forms HYPOGLOSSAL TRIGONE on floor of 4th ventricle Near the central canal, ventrolateral region Receives bilateral corticobulbar (upper motor neuron) input" White arrow DOWN labeled "Rootlets exit from anterior surface of medulla" --- BOX 2 (indigo) --- "BRAINSTEM EXIT Multiple rootlets exit from PREOLIVARY SULCUS (Anterolateral surface of medulla, between pyramid and inferior olive) Rootlets cross posterior cranial fossa laterally" White arrow DOWN labeled "Exits skull" --- BOX 3 (bright orange) --- "HYPOGLOSSAL CANAL Exits skull through HYPOGLOSSAL CANAL (Occipital bone, above foramen magnum) [NOT through jugular foramen - unlike CN IX, X, XI]" White arrow DOWN labeled "Enters neck - runs with C1 nerve fibres" --- BOX 4 (teal) --- "UPPER NECK - INITIAL COURSE Emerges deep to internal jugular vein (IJV) Courses around vagal ganglion Picks up C1 nerve root fibres (hitchhike on CN XII)" BRANCH RIGHT (yellow box): "C1 FIBRES (hitchhiking) Not true CN XII fibres - C1 spinal nerve fibres Leave CN XII at carotid bifurcation level as: SUPERIOR ROOT OF ANSA CERVICALIS (Descendens Hypoglossi) → Joins cervical plexus branches (C2, C3) → Forms ANSA CERVICALIS (loop) → Innervates: Strap muscles (infrahyoid) • Sternohyoid • Sternothyroid • Omohyoid" White arrow DOWN --- BOX 5 (green) --- "MID NECK - DESCENT Passes LATERAL to internal and external carotid arteries Curves around carotid bifurcation heading anteriorly Passes INFERIOR to greater horn of HYOID BONE Deep to posterior belly of digastric and stylohyoid muscles" White arrow DOWN --- BOX 6 (blue) --- "ANTERIOR NECK - FORWARD COURSE Courses SUPERIORLY after hyoid Runs SUPERFICIAL to hyoglossus muscle (Compare: CN IX ran DEEP to hyoglossus) Under the sublingual gland Passes medial to mylohyoid" White arrow DOWN --- BOX 7 (gold, terminal) --- "TONGUE - TERMINAL DISTRIBUTION Branches to innervate IPSILATERAL tongue muscles: INTRINSIC MUSCLES (all 4): • Superior longitudinal • Inferior longitudinal • Transverse • Vertical EXTRINSIC MUSCLES (3 of 4): • Hyoglossus (depresses, retracts) • Styloglossus (retracts, elevates) • Genioglossus (protrudes tongue - MOST IMPORTANT) [NOT palatoglossus - supplied by CN X via pharyngeal plexus]" --- BOTTOM SECTION: Two side-by-side summary boxes --- LEFT (red): "CLINICAL: CN XII INJURY / PALSY UMN lesion: Tongue deviates AWAY from lesion side LMN lesion: Tongue deviates TOWARD lesion side (+ wasting/fasciculations) Key test: Ask patient to protrude tongue - observe deviation Effects: • Dysarthria (slurred speech) • Dysphagia (difficulty swallowing) • Ipsilateral tongue atrophy + fasciculations (LMN) • Bilateral: anarthria, severe dysphagia" RIGHT (orange): "SURGICAL VULNERABILITY • Most vulnerable at: near greater horn of hyoid • During: Level I & II neck dissection • Near: ranine veins (rich venous plexus) • Risk: 0.42% in neck dissection series Management of transection: primary neurorrhaphy or cable grafting Remember: CN XII runs SUPERFICIAL to hyoglossus (CN IX runs DEEP)" Small note at very bottom: "Sources: Gray's Anatomy for Students | Cummings Otolaryngology | Scott-Brown's ORL | Bradley & Daroff's Neurology" All boxes white text, clean sans-serif font, clear labeled arrows, professional medical education style.

prepare it a little faster

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Medical anatomy flowchart poster, dark navy background. Title: "SPINAL ACCESSORY NERVE (CN XI) - Course & Distribution". Pure motor nerve - Branchial Efferent only. Vertical flowchart top to bottom with color boxes and arrows: BOX 1 purple: "SPINAL ACCESSORY NUCLEUS | Anterior horn C1-C5 spinal cord | NOT in brainstem" Arrow: "Rootlets exit lateral surface of spinal cord → ascend in spinal canal" BOX 2 indigo: "ASCENDS IN SPINAL CANAL | Posterior to dentate ligament | Enters skull via FORAMEN MAGNUM" Small side note gray: "Cranial root (caudal medulla) joins briefly then merges with CN X → not true CN XI" BOX 3 orange: "JUGULAR FORAMEN | Exits skull with CN IX and CN X | Most posterior of the three" BOX 4 green: "DESCENT IN NECK | Between IJV and internal carotid artery | Reaches anterior border of SCM | Relation to IJV: anterior 70%, posterior 27%, through 3%" Branch LEFT red: "BRANCH TO SCM | Motor to sternocleidomastoid | ~4 cm below mastoid tip | Pierces SCM in 82%" BOX 5 blue: "POSTERIOR TRIANGLE | Oblique downward course | Within investing cervical fascia | Superficial → vulnerable to injury | C2/C3 proprioceptive contributions" BOX 6 gold: "TRAPEZIUS MUSCLE | Enters 2-4 cm above clavicle | Runs on deep surface | Innervates all 3 parts of trapezius" Bottom two boxes side by side: LEFT red: "MUSCLES: SCM (head rotation/tilt) + TRAPEZIUS (shoulder elevation, scapular rotation, arm abduction >90°)" RIGHT orange: "CN XI PALSY - Eleventh Nerve Syndrome: shoulder drop, inability to abduct arm, scapular winging, trapezius atrophy. Test: shrug against resistance" Clean white text, bold labels, professional style.

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Medical anatomy flowchart poster, dark navy background. Title: "HYPOGLOSSAL NERVE (CN XII) - Course & Distribution". Pure motor nerve - General Somatic Efferent only. Vertical flowchart top to bottom with color boxes and arrows: BOX 1 purple: "HYPOGLOSSAL NUCLEUS | Floor of 4th ventricle, medulla | Forms hypoglossal trigone | Bilateral corticobulbar input" Arrow: "Rootlets exit preolivary sulcus (between pyramid and olive)" BOX 2 indigo: "HYPOGLOSSAL CANAL | Exits occipital bone via hypoglossal canal | NOT jugular foramen | Picks up C1 nerve fibres" Branch RIGHT yellow: "C1 FIBRES (hitchhiking) | Leave at carotid bifurcation | = Superior root of ANSA CERVICALIS | → Strap muscles: sternohyoid, sternothyroid, omohyoid" BOX 3 teal: "UPPER NECK | Deep to IJV | Curves around vagal ganglion | Lateral to carotid arteries" BOX 4 green: "MID NECK | Curves around carotid bifurcation anteriorly | Passes inferior to greater horn of HYOID | Deep to posterior belly of digastric + stylohyoid" BOX 5 blue: "FORWARD & UPWARD COURSE | SUPERFICIAL to hyoglossus muscle (key landmark) | Under sublingual gland | Medial to mylohyoid" BOX 6 gold: "TONGUE - TERMINAL BRANCHES | INTRINSIC (all 4): superior/inferior longitudinal, transverse, vertical | EXTRINSIC (3 of 4): genioglossus, hyoglossus, styloglossus | NOT palatoglossus (= CN X)" Bottom two boxes side by side: LEFT red: "CN XII LMN PALSY: tongue deviates TOWARD lesion side + wasting + fasciculations. Dysarthria + dysphagia. UMN: deviates AWAY." RIGHT orange: "SURGICAL RISK: vulnerable near greater horn of hyoid (Level I/II neck dissection). Superficial to hyoglossus. Ranine veins nearby." Clean white text, bold labels, professional style.

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