Anatomy
MBBS Anatomy question bank: general anatomy and osteology, regional gross anatomy (upper limb, lower limb, thorax, abdomen, pelvis, head and neck), neuroanatomy, histology and embryology.
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Definition
The spinal cord is the part of the CNS within the vertebral canal, containing ascending (sensory) and descending (motor) tracts.
General Features
- Extends foramen magnum → L1–L2 (conus medullaris)
- 31 pairs of spinal nerves
- Grey matter (H-shaped) + surrounding white matter
- Cervical & lumbar enlargements
Ascending Tracts
- Dorsal column — fine touch, vibration, proprioception
- Spinothalamic — pain, temperature
Descending Tracts
- Corticospinal (pyramidal) — voluntary movement
- Extrapyramidal — tone, posture
The cord relays sensation up and motor commands down through named tracts. Tract Function Dorsal column Touch, vibration Spinothalamic Pain, temperature Corticospinal Voluntary movement Applied
- Hemisection (Brown-Séquard syndrome)
- Lumbar puncture below L2 (safe)
🔑KEY POINTS TO REMEMBER- Cord: foramen magnum → L1/L2; 31 spinal nerves.
- Ascending: dorsal column, spinothalamic; descending: corticospinal.
- LP done below L2.
📚SOURCES: BD Chaurasia’s Human Anatomy (Vol. 3); Gray’s Anatomy; Snell’s Clinical Neuroanatomy; Vishram Singh’s Neuroanatomy.Definition
The brainstem connects the brain to the spinal cord and consists of the midbrain, pons and medulla; it holds cranial nerve nuclei and vital centres.
Parts (top → bottom)
- Midbrain — CN III, IV; cerebral peduncles
- Pons — CN V, VI, VII, VIII
- Medulla — CN IX, X, XI, XII; vital centres
Functions
- Conduit for ascending/descending tracts
- Cranial nerve nuclei (III–XII)
- Vital centres — respiratory, cardiovascular (medulla)
- Reticular formation
Three parts stack up, each housing particular cranial nerve nuclei. Part Cranial nerves Midbrain III, IV Pons V, VI, VII, VIII Medulla IX, X, XI, XII Applied
- Brainstem stroke → crossed signs
- Coning (medullary compression)
🔑KEY POINTS TO REMEMBER- Brainstem: midbrain, pons, medulla.
- Cranial nerve nuclei III–XII; vital centres in medulla.
- Stroke → crossed signs.
📚SOURCES: BD Chaurasia’s Human Anatomy (Vol. 3); Gray’s Anatomy; Snell’s Clinical Neuroanatomy; Vishram Singh’s Neuroanatomy.Definition
The cerebrum is the largest part of the brain, comprising the cortical lobes, the internal capsule and the basal ganglia.
Lobes
- Frontal — motor, personality
- Parietal — sensory
- Temporal — hearing, memory
- Occipital — vision
Internal Capsule
- White matter between basal ganglia & thalamus
- Carries corticospinal fibres
- Common site of stroke
Basal Ganglia
- Caudate, putamen, globus pallidus
- Control of movement
The cortex sends motor fibres through the internal capsule past the basal ganglia. Structure Function Frontal lobe Motor, personality Internal capsule Motor fibres Basal ganglia Movement control Applied
- Internal capsule stroke → hemiplegia
- Basal ganglia → Parkinson’s disease
🔑KEY POINTS TO REMEMBER- Lobes: frontal (motor), parietal (sensory), temporal (hearing), occipital (vision).
- Internal capsule carries corticospinal fibres (stroke site).
- Basal ganglia control movement.
📚SOURCES: BD Chaurasia’s Human Anatomy (Vol. 3); Gray’s Anatomy; Snell’s Clinical Neuroanatomy; Vishram Singh’s Neuroanatomy.Definition
The ventricles are CSF-filled cavities in the brain; CSF circulates through them; the meninges cover the brain.
Ventricular System
- Two lateral ventricles
- Third ventricle
- Fourth ventricle
- Connected by foramina (Monro, cerebral aqueduct)
CSF
- Produced by the choroid plexus
- Circulates ventricles → subarachnoid space
- Absorbed by arachnoid villi
Meninges
- Dura, arachnoid, pia
- Subarachnoid space contains CSF
CSF flows through the ventricles into the subarachnoid space, then is absorbed. Ventricle Connection Lateral Foramen of Monro 3rd → 4th Cerebral aqueduct 4th Foramina to subarachnoid Applied
- Hydrocephalus (blocked flow)
- Meningitis (subarachnoid space)
🔑KEY POINTS TO REMEMBER- Ventricles: 2 lateral, 3rd, 4th; linked by Monro & aqueduct.
- CSF: choroid plexus → ventricles → subarachnoid → arachnoid villi.
- Blockage → hydrocephalus.
📚SOURCES: BD Chaurasia’s Human Anatomy (Vol. 3); Gray’s Anatomy; Snell’s Clinical Neuroanatomy; Vishram Singh’s Neuroanatomy.Definition
The brain is supplied by the internal carotid and vertebral arteries, connected at the base by the circle of Willis.
Arterial Supply
- Internal carotid → anterior circulation
- Vertebral → basilar → posterior circulation
Circle of Willis (components)
- Anterior cerebral + anterior communicating
- Internal carotid
- Posterior cerebral + posterior communicating
Cerebral Arteries
- Anterior cerebral — medial frontal/parietal
- Middle cerebral — lateral surface (commonest stroke)
- Posterior cerebral — occipital lobe
Two arterial systems meet in the circle of Willis and branch to the brain. Artery Supplies ACA Medial hemisphere MCA Lateral hemisphere PCA Occipital lobe Applied
- MCA stroke is commonest
- Berry aneurysm on the circle of Willis
🔑KEY POINTS TO REMEMBER- Anterior (internal carotid) + posterior (vertebrobasilar) circulation.
- Circle of Willis links them at the base.
- MCA = commonest stroke; berry aneurysm site.
📚SOURCES: BD Chaurasia’s Human Anatomy (Vol. 3); Gray’s Anatomy; Snell’s Clinical Neuroanatomy; Vishram Singh’s Neuroanatomy.Definition
The corticospinal (pyramidal) tract is the main descending motor pathway for voluntary movement.
Pathway
- Origin: motor cortex (precentral gyrus)
- Descends through internal capsule and brainstem
- Decussates in the medulla (pyramids)
- → anterior horn cell → muscle
Divisions
- Lateral corticospinal (crossed) — limbs
- Anterior corticospinal (uncrossed)
Voluntary commands descend and cross in the medulla before reaching muscle. Feature Detail Origin Motor cortex Crosses Medulla (pyramids) Function Voluntary movement Applied
- Lesion → UMN signs
- Stroke commonly damages this tract
🔑KEY POINTS TO REMEMBER- Corticospinal = voluntary movement; from motor cortex.
- Decussates in the medulla.
- Lesion → UMN signs.
📚SOURCES: BD Chaurasia’s Human Anatomy (Vol. 3); Gray’s Anatomy; Snell’s Clinical Neuroanatomy; Vishram Singh’s Neuroanatomy.Definition
The internal capsule is a compact band of white matter carrying fibres between the cortex and lower centres, lying between the basal ganglia and the thalamus.
Parts
- Anterior limb
- Genu
- Posterior limb (corticospinal fibres)
Significance
- Carries motor (corticospinal) & sensory fibres
- Small area packs many fibres
- Common stroke site (lenticulostriate arteries)
A small band carrying dense motor/sensory fibres — a critical stroke site. Part Carries Genu Corticobulbar fibres Posterior limb Corticospinal fibres Applied
- Stroke → contralateral hemiplegia
- Dense motor + sensory loss
🔑KEY POINTS TO REMEMBER- Internal capsule: anterior limb, genu, posterior limb.
- Posterior limb carries corticospinal fibres.
- Stroke → dense contralateral hemiplegia.
📚SOURCES: BD Chaurasia’s Human Anatomy (Vol. 3); Gray’s Anatomy; Snell’s Clinical Neuroanatomy; Vishram Singh’s Neuroanatomy.Definition
The circle of Willis is an anastomotic ring of arteries at the base of the brain, connecting the anterior and posterior circulations.
Components
- Two anterior cerebral arteries
- One anterior communicating artery
- Two internal carotid arteries
- Two posterior cerebral arteries
- Two posterior communicating arteries
Function
- Provides collateral blood flow
- Equalises pressure
- Backup if one vessel is blocked
A ring of arteries links both circulations for collateral supply. Connection Artery Anterior Anterior communicating Posterior Posterior communicating Applied
- Berry aneurysm (esp. anterior communicating)
- Collateral circulation in occlusion
🔑KEY POINTS TO REMEMBER- Ring at the base connecting anterior + posterior circulation.
- Communicating arteries complete it.
- Berry aneurysm site.
📚SOURCES: BD Chaurasia’s Human Anatomy (Vol. 3); Gray’s Anatomy; Snell’s Clinical Neuroanatomy; Vishram Singh’s Neuroanatomy.Definition
Cerebrospinal fluid (CSF) circulates through the ventricles and subarachnoid space, produced by the choroid plexus and absorbed by arachnoid villi.
Pathway
- Choroid plexus (lateral ventricles)
- → 3rd ventricle (foramen of Monro)
- → 4th ventricle (cerebral aqueduct)
- → subarachnoid space → arachnoid villi
CSF is made, flows through the ventricles, then is absorbed into venous blood. Step Route Production Choroid plexus Flow Ventricles → subarachnoid Absorption Arachnoid villi Applied
- Obstruction → hydrocephalus
- Communicating vs non-communicating
🔑KEY POINTS TO REMEMBER- CSF: choroid plexus → ventricles → subarachnoid → arachnoid villi.
- Via Monro & cerebral aqueduct.
- Obstruction → hydrocephalus.
📚SOURCES: BD Chaurasia’s Human Anatomy (Vol. 3); Gray’s Anatomy; Snell’s Clinical Neuroanatomy; Vishram Singh’s Neuroanatomy.Definition
The basal ganglia are subcortical grey-matter nuclei that regulate the initiation and control of movement.
Components
- Caudate nucleus
- Putamen
- Globus pallidus
- (+ substantia nigra, subthalamic nucleus)
Functions
- Initiation & regulation of movement
- Control of muscle tone
- Suppress unwanted movements
These nuclei fine-tune movement; damage produces movement disorders. Structure Grouping Caudate + putamen Striatum Globus pallidus Pallidum Applied
- Parkinson’s (substantia nigra)
- Huntington’s (caudate)
🔑KEY POINTS TO REMEMBER- Basal ganglia: caudate, putamen, globus pallidus.
- Regulate movement + tone.
- Parkinson’s & Huntington’s disorders.
📚SOURCES: BD Chaurasia’s Human Anatomy (Vol. 3); Gray’s Anatomy; Snell’s Clinical Neuroanatomy; Vishram Singh’s Neuroanatomy.Definition
The cerebellum lies in the posterior cranial fossa and coordinates movement, balance and muscle tone.
Structure
- Two hemispheres + vermis
- Three lobes; three peduncles (connect to brainstem)
- Grey cortex + white matter (arbor vitae)
Functions
- Coordination of movement
- Balance & posture
- Regulation of muscle tone
- Motor learning
The cerebellum links to the brainstem to smooth and coordinate movement. Part Function Vermis Trunk, balance Hemispheres Limb coordination Applied
- Ataxia, intention tremor, nystagmus
- Cerebellar signs are ipsilateral
🔑KEY POINTS TO REMEMBER- Cerebellum: hemispheres + vermis; 3 peduncles.
- Coordination, balance, tone.
- Lesion → ipsilateral ataxia/intention tremor.
📚SOURCES: BD Chaurasia’s Human Anatomy (Vol. 3); Gray’s Anatomy; Snell’s Clinical Neuroanatomy; Vishram Singh’s Neuroanatomy.Definition
The thalamus is a large mass of grey matter in the diencephalon that acts as the main sensory relay station to the cerebral cortex.
Functions
- Relays all sensory input (except smell) to the cortex
- Involved in motor control (relay)
- Role in consciousness and alertness
Position
- On either side of the 3rd ventricle
- Below the internal capsule
Nearly all sensation relays through the thalamus on its way to the cortex. Feature Detail Role Sensory relay Exception Smell (olfaction) Applied
- Thalamic stroke → sensory loss
- Thalamic pain syndrome
🔑KEY POINTS TO REMEMBER- Thalamus = main sensory relay (except smell).
- Beside the 3rd ventricle.
- Stroke → sensory loss / thalamic pain.
📚SOURCES: BD Chaurasia’s Human Anatomy (Vol. 3); Gray’s Anatomy; Snell’s Clinical Neuroanatomy; Vishram Singh’s Neuroanatomy.