Gross Anatomy of the Head and Neck

Overview of Brain and Blood Supply

  • Course Code: ANA 312/302

  • Subject: Gross Anatomy of the Head and Neck

  • Focus Areas: Brain, its blood supply, and cranial nerves.

Meninges of the Brain

  • Coverings: Skin, skull, dura mater, arachnoid layer, pia mater, and cerebral cortex.

  • Functions:   1. Covers and protects the CNS.   2. Protects blood vessels and encloses venus sinuses.   3. Contains Cerebrospinal Fluid (CSF).   4. Forms partitions within the skull.

Ventricular System and Cerebrospinal Fluid (CSF)

  • Ventricles: Right and Left lateral ventricles, third ventricle, and fourth ventricle.

  • Passages: interventricular foramen, cerebral aqueduct (aqueduct of Sylvius), and central canal of spinal cord.

  • CSF Characteristics:   - Adult volume: approximately 150 ml150\,ml.   - Components: anions, cations, glucose, lactic acid, proteins, urea, and WBC.

  • CSF Functions:   1. Reduces brain weight by approximately 97%97\%.   2. Prevents head injury.   3. Supplies nutrition.   4. Transports hormones.

The Cerebrum

  • Lobes: Frontal, Parietal, Temporal, and Occipital.

  • Functions: Higher brain functions, sensory processing, motor initiation, and information integration.

  • Cross-Sectional Features: White matter, basal ganglia, ventricles, cerebral cortex, and corpus callosum.

  • Hemispheric Specialization:   - Left Side: Language development, mathematical/learning capabilities, and sequential thought.   - Right Side: Visual-spatial skills, musical/artistic activities, and intuitive abilities.

Cortical Functional Areas

  • Motor and Sensory:   - Primary Somatosensory Cortex: Processes touch from areas like hands, lips, and genitals.   - Primary Motor Cortex: Controls movement for areas like face, tongue, and extremities.

  • Association Areas: Frontal association area, Somatosensory association area, Auditory association area, and Visual association area.

  • Specific Senses: Speech, Smell, Taste, Hearing, Reading, and Vision.

Diencephalon and Limbic System

  • Diencephalon: Includes the thalamus and hypothalamus.   - Thalamus: Relay center for sensory tracts; involves pain, temperature, touch, emotions, and arousal.   - Hypothalamus: Autonomic control (blood pressure, heart rate), body temperature, water balance, sleep/wake cycles, appetite, sexual arousal, and endocrine regulation via the pituitary gland.

  • Limbic System: Includes the Thalamus, Hypothalamus, Amygdala, and Hippocampus.

  • Reticular Formation: Processes inputs from eyes, ears, touch, pain, and temperature; directs motor output to the spinal cord.

Brainstem and Cerebellum

  • Midbrain: Contains ascending/descending tracts; reflex center for eye muscles; processes visual and auditory stimuli.

  • Pons: Regulates breathing and connects cerebellum halves.

  • Medulla Oblongata (or Medulla oblongatal): Extension of the spinal cord; site for nerve tract crossover; origin for most cranial nerves. Controls subconscious activities: respiratory and heart rates, swallowing, coughing, and sneezing.

  • Cerebellum: Coordinates muscular activity, equilibrium, posture, and movement.

Arterial Supply of the Brain

  • Source Arteries: Pairs of vertebral and internal carotid arteries.

  • Vertebral Artery Chain:   - Enters via foramen magnum; joins at the pontomedullary junction to form the basilar artery.   - Basilar artery bifurcates into 22 posterior cerebral arteries at the upper pons.

  • Internal Carotid Artery Parts:   1. cervical   2. petrous   3. cavernous   4. cerebral (terminates into anterior and middle cerebral arteries).

  • Cerebral Arterial Circle (of Willis):   - Vascular shunt via interconnections on the ventral brain surface.   - Components: anterior communicating a., anterior cerebral a., internal carotid a., posterior communicating a., and posterior cerebral a.

Cranial Nerves

  1. I Olfactory: Smell.

  2. II Optic: Vision.

  3. III Oculomotor: 44 of 66 extrinsic eye muscles.

  4. IV Trochlear: Extrinsic eye muscles (superior oblique).

  5. V Trigeminal: Facial sensation and chewing muscles.

  6. VI Abducens: Lateral eye movement.

  7. VII Facial: Facial expression.

  8. VIII Vestibulocochlear: Hearing and balance.

  9. IX Glosopharyngeal (or Glossopharygeal): Tongue and pharynx.

  10. X Vagus: Slows heart and breathing; visceral motor/sensory.

  11. XI Accessory: Sternocleidomastoid and trapezius muscles; accessory to vagus.

  12. XII Hypoglossal: Muscles under the tongue.

Applied Anatomy and Pathology

  • Traumatic Brain Injuries: Concussion, contusion, subdural/subarachnoid hemorrhage, and contrecoup injury.

  • Cerebrovascular Accidents (CVAs): Ischemia, thrombus, embolism, arteriosclerosis, and stroke.

  • Degenerative Diseases: Alzheimer’s, Down’s, Parkinson’s, Huntington’s Chorea, MS, Epilepsy, and Schizophrenia.