FOM2 Master Doc PDF - Nervous System Review

Week 1 10/28 Nervous System Review Nervous System Overview Somatic General Sensory (Afferent) First-order Neuron → Second-order Neuron → Third-order Neuron → Nervous spinal cord or brainste...

Week 1 10/28 Nervous System Review Nervous System Overview Somatic General Sensory (Afferent) First-order Neuron → Second-order Neuron → Third-order Neuron → Nervous spinal cord or brainstem thalamus Cerebral cortex System General Motor (Efferent) UMN: Cerebrum, midbrain, or brainstem → LMN → Target muscle Interneuron/LMN Autonomic Visceral Sensory (Afferent) Nervous System Visceral Sympathetic Preganglionic Neuron: Postganglionic Neuron: Motor Cell body in lateral horns of spinal cord (T1-L2) → Sympathetic ganglion → (Efferent) sympathetic ganglion Target muscle (for head, the axons travel from T1-T4 levels to cervical sympathetic ganglia) Parasympathetic Preganglionic Neuron: Postganglionic Neuron: From brainstem (cranial nerves) or sacral spinal Parasympathetic cord) → Parasympathetic ganglia ganglia → target organ/muscle 10/28 Intro to Brain, Spinal Cord, and Meninges Describe the spatial relationships of major regions and structures of the brain. Three Major Regions of the Brain: 1. Forebrain a. Cerebrum b. Diencephalon i. Thalamus ii. Hypothalamus iii. Epithalamus 2. Midbrain a. Mesencephalon 3. Hindbrain a. Pons b. Medulla Oblongata c. Cerebellum Review general structures of the spinal cord (spinal nerve roots, conus medullaris). At the conus medullaris (L1-L2), the pia mater continues as the filum terminale, which functions to anchor the spinal cord. 1. Filum terminale interim: moves freely in subarachnoid space down to S2 level 2. Filum terminale externum: anchors dural sac to coccyx, exists where there is no more CSF or subarachnoid space Description of the 3 meningeal layers and dural partitions. Three layers: 1. Dura mater: outermost layer, tough, projects into the falx cerebri and tentorium cerebelli partitions 2. Arachnoid mater: middle layer, web-like, contains CSF within the subarachnoid space 3. Pia mater: innermost layer, adheres to the brain and spinal cord surfaces a. Denticulate ligaments: extensions of pia mater that anchor the spinal cord laterally, helping to stabilize it within the dural sac Dural partitions of the meninges: 1. Falx cerebri: runs between the two hemispheres from the frontal crest/crista galli to the internal occipital protuberance 2. Tentorium cerebelli: separates the cerebrum and cerebellum; forms platform for occipital lobes; runs from sphenoid clinoid processes to petrous portion of temporal bone 3. Falx cerebelli: runs between cerebellar hemispheres inferior to tentorium 4. Diaphragma selli: runs between cerebrum and pituitary gland, holds passage for the infundibulum 10/28 Embryology of the CNS Describe the process of neurulation with accurate timing, inluding the development and anatomical significance of the following: 1. Ectoderm: Neurulation begins with the ectoderm, which differentiates into the neural plate around day 18-20 of development. The ectoderm is the outermost germ layer and gives rise to the neural tube, which eventually forms the central nervous system (brain and spinal cord).  2. Neural plate: The neural plate is a thickened region of the ectoderm that forms as a response to signals from the underlying notochord. It appears around day 18 and gives rise to the neural tube. 3. Neural groove: By day 20-21, the neural plate invaginates along the midline to form the neural groove, flanked by neural folds. 4. Neural folds: These are elevations on either side of the neural groove that move towards each other and eventually fuse, forming the neural tube. 5. Neural tube: The neural tube forms around day 22-26 when the neural folds fuse. It closes first at the middle of the embryo and then "zips" shut both cranially and caudally, with the anterior and posterior neuropores closing last. 6. Neuropores: The anterior (rostral) and posterior (caudal) neuropores are openings at the ends of the neural tube that close by days 25-27. Their closure is essential for proper neural tube formation, with failure leading to defects like anencephaly or spina bifida. 7. Neural crest: Cells that break away from the tips of the neural folds form the neural crest. These cells migrate and differentiate into various structures like sensory neurons, autonomic ganglia, and components of the peripheral nervous system. 8. Mantle layer: The mantle layer arises from the intermediate zone of the neural tube, containing proliferating cells that become neuronal cell bodies, forming gray matter. 9. Marginal layer: his is the outermost layer of the neural tube, where axons extend from the mantle layer, forming white matter. 10. Sulcus limitans: A groove in the neural tube that appears around week 4, dividing the dorsal (alar plate) and ventral (basal plate) regions of the developing spinal cord. 11. Basilar plate: The ventral part of the neural tube that gives rise to motor neurons, including those in the ventral horn of the spinal cord. 12. Alar plate: The dorsal part of the neural tube that forms sensory neurons, including those in the dorsal horn of the spinal cord. 13. Ventral horn: Arises from the basal plate and contains motor neurons that innervate skeletal muscles. 14. Dorsal horn: Arises from the alar plate and contains sensory neurons that receive input from peripheral sensory receptors. Describe the origin of sensory and motor spinal nerves and how they connect developmentally from the periphery to the spinal cord. Sensory nerves develop from the neural crest cells, which give rise to the dorsal root ganglia. Axons from these ganglia grow into the dorsal horn of the spinal cord, forming sensory pathways. Motor nerves originate from neurons in the ventral horn (derived from the basal plate) of the spinal cord. Axons from these neurons exit the spinal cord through the ventral roots and connect to skeletal muscles. Together, the sensory (dorsal) and motor (ventral) roots merge to form a spinal nerve, which connects the peripheral structures to the central nervous system. Describe the composition and development of gray and white matter in the spinal cord. Gray Matter: Composed mainly of neuronal cell bodies, which originate from the mantle layer of the neural tube. It forms the dorsal (sensory) and ventral (motor) horns of the spinal cord. White Matter: Consists of myelinated axons, originating from the marginal layer of the neural tube. It surrounds the gray matter and allows for communication between different levels of the spinal cord and the brain. Explain why the adult spinal cord ends around L1-2 based on embryology. During development, the spinal cord and vertebral column grow at different rates. Initially, the spinal cord extends the entire length of the vertebral column. However, as the vertebral column grows faster than the spinal cord, the cord ends higher relative to the vertebral levels. By birth, the spinal cord terminates around L3, and in adults, it typically ends at L1-2. This differential growth leads to the formation of the cauda equina, where lumbar and sacral nerve roots extend beyond the spinal cord. Describe the following structures’ development and final anatomical state: 1. Rhombencephalon: Develops into the metencephalon and myelencephalon, giving rise to structures like the pons, cerebellum, and medulla. 2. Myelencephalon: Differentiates into the medulla oblongata, which controls autonomic functions like heart rate and breathing. 3. Metencephalon: Develops into the pons and cerebellum, involved in motor control and coordination. 4. Mesencephalon: Forms the midbrain, containing structures like the tectum and tegmentum, involved in visual and auditory processing. 5. Prosencephalon: Splits into the telencephalon and diencephalon. The telencephalon forms the cerebral hemispheres, while the diencephalon forms structures like the thalamus and hypothalamus. 6. Diencephalon: Forms the thalamus, hypothalamus, and related structures, crucial for sensory relay and autonomic control. 7. Telencephalon: Develops into the cerebral cortex, basal ganglia, and limbic system, involved in higher cognitive functions. 8. Cephalic Flexure: A ventral bend in the developing neural tube at the midbrain level, helping to shape the forebrain. 9. Pontine Flexure: A dorsal bend between the metencephalon and myelencephalon, contributing to the development of the fourth ventricle. 10. Cervical Flexure: A ventral bend between the myelencephalon and spinal cord. 11. Rhombic Lip: Contributes to the formation of the cerebellum during development. Describe the developmental etiology and manifestation of the following:  Arnold-Chiari Deformity: A hindbrain malformation where the cerebellum and medulla elongate and protrude through the foramen magnum into the spinal canal. This can block cerebrospinal fluid (CSF) flow, leading to hydrocephalus and cranial nerve malformations. Neural Tube Disorders: These result from incomplete closure of the neural tube. Examples include: Spina Bifida: Failure of the posterior neuropore to close properly, leading to defects in the spinal column and potential exposure of the spinal cord. Anencephaly: Failure of the anterior neuropore to close, resulting in a lack of development of major parts of the brain, typically fatal. 10/28 + 10/29 Cranial Nerves I&II Periphery to CNS CNS to Periphery (Sensory) (Motor) Touch, pain, temperature & proprioception Somatic Afferent Somatic Efferent Vision, hearing/balance, smell, taste Special Afferent Involuntary (autonomic) Visceral Afferent Visceral Efferent CN Nerve Type Function Pathway Oh Once One Takes The Anatomy Final, Very Great Vacations Are Had I Olfactory Special Afferent Senses Olfactory receptors → olfactory fila → through cribriform smell plate → olfactory bulb → olfactory tract → frontal & temporal lobe II Optic Special Afferent Senses Optic canal → Optic chiasm → optic tract → lateral vision geniculate nucleus (thalamus) → visual cortex (for processing) III Oculomotor Somatic Efferent Moves Midbrain → Enters orbit through superior orbital fissure → eyes innervates superior/medial/inferior rectus, inferior oblique, levator palpebrae mm. Visceral Efferent Constricts Sphincter pupillae m pupils Lens Ciliary m accommod ation IV Trochlear Somatic Efferent Moves Midbrain → Enters orbit through superior orbital fissure → eyes innervates superior oblique m. V1 Trigeminal Somatic Afferent “SOFT GANG → PONS” (Ophthalmic Superior Orbital Fissure → Trigeminal Ganglion → Pons division) V2 Trigeminal Somatic Afferent “FOT GANG → PONS” (Maxillary division) Foramen Ovale → Trigeminal Ganglion → Pons V3 Trigeminal Somatic Afferent “FRT GANG → PONS” (Mandibular / Somatic Foramen Rotundum → Trigeminal Ganglion → Pons division) Efferent VI Abducens Somatic Efferent Moves Abducens nuclei (in pons-medulla junction) → Enters orbit eyes through superior orbital fissure → innervates lateral rectus m. VII Facial Visceral efferent Salivation Superior salivatory nucleus (pons) → IAM → geniculate (lower) ganglion → main trunk of facial n. → chorda tympani → through petrotympanic fissure → lingual n. (hitchhiking) → submandibular ganglion → postganglionic fibers → submandibular & sublingual glands Visceral efferent Tears Superior salivatory nucleus (pons) → IAM → geniculate (upper) (lacrimal) ganglion → greater petrosal n. → nerve of pterygoid canal Mucus → pterygopalatine ganglion → (nasal) - postganglionic neurons → branches of maxillary n. Mucus in (CNVII) → nasal & palate glands mouth & - Maxillary n. (CNVII) → Zygomatic n. (CNV2) → throat Lacrimal n. (CNVI) → lacrimal gland (palate) Special afferent Taste Anterior ⅔ of tongue: Taste receptors → lingual n. (CNV3) (from anterior ⅔ of → chorda tympani → through petrotympanic fissure → tongue) tympanic cavity → main trunk → geniculate ganglion Special afferent Taste Palate: Maxillary n. Branches (CNV2)→ nerve of pterygoid (from palate) canal → greater petrosal n. → geniculate ganglion → through IAM → solitary nucleus (medulla oblongata) Somatic afferent Minor Facial n. (external ear) → Vagus n. (ear canal) → tympanic  membrane VIII Vestibulocochlear Special Afferent Senses Vestibular & cochlear ganglion (inside cochlea) → balance, vestibular & cochlear nerves → internal acoustic meatus → equilibrium, vestibular & cochlear nuclei (in pons/medulla junction) hearing IX Glossopharyngeal Somatic Efferent Nucleus ambiguus (medulla) → emerges from medulla (inferior to CNVII & CNVIII) → exits cranium via jugular foramen → stylopharyngeus m. Visceral Efferent Inferior salivatory nucleus (pons/medulla) → emerges from medulla → exits via jugular foramen → branches off into tympanic n. → re-enters cranium (via inferior tympanic canaliculus) → expands into tympanic plexus → lesser petrosal n. emerges into middle cranial fossa → exits skull via foramen ovale → synapses at otic ganglion →postganglionic fibers hitchhike on auriculotemporal n (CNV3) → innervate parotid gland Somatic Afferent Oropharynx, palatine tonsils, posterior ⅓ of tongue → lingual, tonsillar, & pharyngeal branches merge to main  trunk of CNIX → superior & inferior ganglion of CNIX → medulla → spinal nucleus of trigeminal n. (CNV) Special Afferent Taste Oropharynx, palatine tonsils, posterior ⅓ of tongue → (posterior lingual, tonsillar, & pharyngeal branches merge to main ⅓ of trunk of CNIX → inferior ganglion of CNIX → medulla → tongue) solitary nucleus Visceral Afferent Barorecepti on/Chemor eception X Vagus Mixed XI Accessory Somatic Efferent Accessory nucleus (in spinal cord) → roots emerge from C1-C5/6 → enters cranium via foramen magnum → exits  cranium via jugular foramen XII Hypoglossal Somatic Efferent Tongue Hypoglossal nucleus (in medulla) → emerges from ventral muscles medulla → exits cranium via hypoglossal canal → enters floor of mouth Pupillary light reflex Bright light hits eyes → Optic n. (CNII) sends signal to midbrain & occipital lobe → Oculomotor n. (CNIII) preganglionic PS fibers send signal to ciliary ganglion → Oculomotor n. (CNIII) postganglionic PS fibers travel in short ciliary nn. to sphincter pupillae mm. → pupils constrict Skull: Craniometric Corresponding Fontanelle Corresponding sutures Point (6 total, 2 lateral each side) Bregma Anterior fontanelle Coronal and sagittal Lambda Posterior fontanelle Sagittal and Lambdoid Pterion Sphenoidal (anterolateral) fontanelle Coronal and sphenoparietal *Middle meningeal a Asterion Mastoid (posterolateral) fontanelle Lambdoid and occipitomastoid Condition Definition Causes Features Management  Plagiocephaly Asymmetrical Positional (e.g., Open sutures; Repositioning, head shape due lying on one correctable with helmet therapy. to external side). helmets. pressure (deformational). Craniosynosto Premature Genetic or Closed Surgical sis fusion of one or sporadic (e.g., suture(s); correction. more cranial FGFR compensatory sutures mutations). growth (structural elsewhere. issue). Key Suture Associations: Sagittal Synostosis: Long, narrow head (scaphocephaly). Coronal Synostosis: Flattened forehead (anterior plagiocephaly). Metopic Synostosis: Triangular forehead (trigonocephaly). (looking from top) Lambdoid Synostosis: Posterior asymmetry (rare). Sagittal Coronal 10/28 CMR HEENT I 1. HEENT History and Subjective Information Common Symptoms: Includes fever, chills, weight changes, headaches, dizziness, vision changes, ear pain, hearing loss, nasal congestion, sore throat, swollen glands, and cough. Medical and Family History: Should consider allergies, asthma, autoimmune conditions, malignancies, childhood infections, and vaccinations. Social History: Relevant factors include tobacco use, substance abuse, and recent travel or sick contacts. 2. Vital Signs and Their Significance in HEENT Exam  Temperature: Fever may indicate infection or inflammation. Pulse and Blood Pressure: Thyroid conditions can influence both; high blood pressure can lead to ocular symptoms. Respiratory Rate and Oxygen Saturation: May indicate upper or lower airway involvement. 3. Examination Components Head: Inspect the general size, hair, and scalp. Look for asymmetry, hair loss, or skin lesions. Palpate the skull for tenderness or abnormalities. Eyes: ○ Visual Acuity: Typically measured with a Snellen chart. ○ Extraocular Movements (EOM): Assesses the six eye muscles controlled by CN III, IV, and VI. ○ Visual Fields: Evaluates the peripheral vision in all directions. ○ Pupils: Inspect size, shape, symmetry, and light reaction. The "swinging light test" checks for consensual response. ○ Fundoscopic Exam: Uses an ophthalmoscope to inspect the retina, optic disc, macula, and blood vessels. Ears: ○ Inspection: Check for symmetry, shape, and any lesions. ○ Hearing Tests: Finger rub or whisper tests; Rinne and Weber tests differentiate conductive and sensorineural hearing loss. ○ Otoscopic Exam: Examine the ear canal and tympanic membrane for abnormalities like infection or fluid buildup. Nose and Sinuses: ○ Inspection: External nose inspection and internal examination with an otoscope. ○ Palpation and Percussion: Assesses tenderness in the maxillary and frontal sinuses, which may indicate sinusitis. Mouth and Throat: ○ Inspection: Observe lips, teeth, gums, mucosa, tonsils, and pharynx for lesions, swelling, or signs of infection. ○ Gums and Teeth: Check for dental health, gingival inflammation, or hypertrophy. Neck: ○ Inspection: Look for asymmetry, masses, or visible venous distention. ○ Palpation: Lymph Nodes: Palpate lymph nodes (e.g., preauricular, submandibular, cervical) for size, tenderness, and mobility. Thyroid: Palpate the thyroid gland from behind the patient, noting its size and any asymmetry or nodules. 4. Documentation and Common Abnormal Findings  Documentation: Details findings like visual acuity, eyelid condition, conjunctiva and sclera appearance, ear canal and tympanic membrane condition, nasal mucosa, sinus tenderness, and lymph node or thyroid abnormalities. Typical Abnormalities: ○ Eye Findings: Entropion, ectropion, conjunctivitis, ptosis, or pupil asymmetry. ○ Ear Issues: Tympanic membrane perforation, otitis media. ○ Nasal and Sinus Findings: Nasal polyps, discharge, sinus tenderness. ○ Oral and Throat Abnormalities: Tonsillar enlargement, dental decay, mucosal lesions. ○ Neck Findings: Enlarged lymph nodes, thyroid enlargement, or tracheal deviation. 5. Key Techniques and Tools Tools: Use of the ophthalmoscope, Snellen chart, otoscope, tuning fork, and stethoscope for a thorough exam. Communication Skill 10/28 OPP Cervical Screening/Regional/Segmental 10/29 Skull List the names of the bones and identify what other cranial bones they articulate with. Identify the major openings and fossae of the skull, the cranial bones that comprise them, and the major structures they contain. Identify major features and foramina of each bone and describe the structures that are transmitted through each foramen. List and identify the cranial sutures and craniometric points. List and identify the fetal fontanelles and explain their function. Define premature craniosyntosis and describe its consequences. Contrast these consequences with deformational plagiocephaly. Bones and Articulations: Paired Bones: Parietal, Temporal, Lacrimal, Nasal, Inferior Nasal Conchae, Maxillae, Palatines, Zygomatics, Auditory Ossicles. Unpaired Bones: Occipital, Sphenoid, Frontal, Ethmoid, Vomer, Mandible. Major Openings, Fossae, and Structures: Foramen Magnum: In the occipital bone, transmits the spinal cord.  Optic Canal: In the sphenoid, transmits CN II and ophthalmic artery. Superior Orbital Fissure: Between the sphenoid wings, transmits CN III, IV, VI, V1, and veins. Cranial Fossae: ○ Anterior (frontal and ethmoid), ○ Middle (sphenoid and temporal), ○ Posterior (occipital and parts of temporal). Features and Foramina: View Seen Foramina/Fissure From → To Structure(s) Diagram Anterior Supraorbital Orbit → Supraorbital a., v., n. (orbital) notch/foramen Forehead Optic canal ACF → Orbit CNII, ophthalmic a. Superior orbital MCF → Orbit CNIII, CNIV, CNV1, CNVI fissure Superior & inferior opthalmic vv. Inferior orbital Pterygopalatine Infraorbital a., v., n. fissure fossa → orbit Zygomatic n. Inferior ophthalmic v. Anterior Nasolacrimal canal Orbit → Nasal Nasolacrimal duct (facial) Cavity Zygomaticofacial Orbit → Face Zygomaticofacial a., v., n. foramen Infraorbital foramen Orbit → Cheek Infraorbital a., v., n. Mental foramen Mandibular Mental a., v., n. Canal → Chin Inferior Incisive foramina Nasal Cavity → Nasopalatine n., (MCF) Oral Cavity sphenopalatine a. & v. Greater & lesser Palatine Canal Greater & lesser palatine palatine foramina → Oral Cavity a., v., n. Foramen ovale MCF → Base of CNV3, lesser petrosal n. skull Foramen spinosum Base of skull → Meningeal branch of MCF CNV3, middle meningeal a. Carotid canal Base of skull → Internal carotid a., MCF sympathetic plexus Petrotympanic MCF → CNVII (chorda tympani) fissure Infratemporal (see diagram below) fossa Inferior Stylomastoid Facial canal → CNVII (PCF) foramen Base of skull Jugular foramen PCF → Base of CNIX, CNX, CNXI skull Internal jugular v., inferior petrosal v. Hypoglossal canal PCF → Base of CNXII skull Condylar canal Base of skull → Emissary vv. PCF Mastoid foramen Base of skull → Emissary vv. PCF Cranial Sutures and Craniometric Points: Sutures: Coronal (frontal-parietal), Sagittal (between parietal bones), Lambdoid (parietal-occipital), Squamosal (parietal-temporal). Craniometric Points: Bregma, Lambda, Nasion, Glabella, Pterion, Asterion, Inion, and Opisthion. Fetal Fontanelles and Function: Fontanelles: Anterior, Posterior, Sphenoidal, and Mastoid.  Function: Allow for flexibility during childbirth and provide space for brain growth. Premature Craniosynostosis and Consequences: Premature Craniosynostosis: Early closure of cranial sutures, potentially causing restricted skull and brain growth, leading to intracranial pressure and potential neurological issues. Deformational Plagiocephaly: Occurs when the sutures are open; non-surgical correction is possible with a helmet to reshape the skull. This is typically less severe than craniosynostosis. 10/29 Superficial Neck 1. Neck Triangles Anterior Triangle: Bordered by the midline, sternocleidomastoid (SCM) muscle, and mandible. It includes smaller triangles: ○ Submandibular Triangle: Contains the submandibular gland and facial artery/vein. ○ Submental Triangle: Contains submental lymph nodes. ○ Carotid Triangle: Contains the carotid artery, internal jugular vein, hypoglossal nerve (CN XII), and ansa cervicalis. ○ Muscular Triangle: Contains infrahyoid muscles, thyroid and parathyroid glands, larynx, and trachea. Posterior Triangle: Bordered by the SCM, trapezius, and clavicle. It includes: ○ Occipital Triangle: Contains the accessory nerve (CN XI), brachial and cervical plexuses, and scalene muscles. ○ Subclavian (Omoclavicular) Triangle: Contains the subclavian artery/vein and brachial plexus. 2. Muscles of the Neck Superficial Muscles: ○ Sternocleidomastoid (SCM): Flexes and rotates the neck; innervated by the accessory nerve (CN XI). ○ Platysma: Tenses skin of the neck; innervated by the facial nerve (CN VII). Infrahyoid Muscles: Depress the hyoid and larynx, primarily innervated by the ansa cervicalis. ○ Includes sternohyoid, omohyoid, sternothyroid, and thyrohyoid. Suprahyoid Muscles: Elevate the hyoid bone; innervated by the facial nerve (CN VII) and trigeminal nerve (CN V3). ○ Includes digastric, mylohyoid, and stylohyoid.  Scalene Muscles: Elevate ribs and assist in lateral neck flexion; important for relations with subclavian artery/vein and brachial plexus. 3. Thyroid and Parathyroid Glands Thyroid Gland: Located at the C5-T1 vertebral level, regulates metabolism and cardiovascular function. ○ Blood Supply: Superior and inferior thyroid arteries. ○ Innervation: Vasomotor innervation from sympathetic fibers. Parathyroid Glands: Four small glands on the posterior thyroid surface, involved in calcium and phosphate regulation. 4. Major Vessels of the Neck Arteries: ○ Common Carotid Artery: Bifurcates at the level of the thyroid cartilage into the external and internal carotid arteries. ○ External Carotid Artery (ECA): Supplies the face and scalp, with branches including superior thyroid, lingual, and facial arteries. ○ Subclavian Artery: Passes between anterior and middle scalene muscles; supplies the upper thorax and neck. Veins: ○ Internal Jugular Vein: Drains the brain, face, and neck. ○ External and Anterior Jugular Veins: Drain superficial regions of the head and neck. ○ Subclavian Vein: Joins with the internal jugular vein to form the brachiocephalic vein. 5. Nerves of the Neck Cervical Plexus: Includes cutaneous nerves, ansa cervicalis, and the phrenic nerve (innervates the diaphragm). Cranial Nerves: ○ Accessory Nerve (CN XI): Innervates SCM and trapezius muscles. ○ Hypoglossal Nerve (CN XII): Motor control of tongue muscles. ○ Vagus Nerve (CN X): Gives rise to recurrent laryngeal nerve and superior laryngeal nerve, which innervate laryngeal structures. Sympathetic Trunk: Runs along the cervical spine, providing sympathetic innervation to neck structures. 6. Lymphatics Superficial and Deep Cervical Nodes: These nodes drain the head, face, and neck, eventually converging into the thoracic duct or right lymphatic duct. 10/29 CMR HEENT II 10/29 OPP Cervical Soft Tissue/Articulatory 10/29 OPP Principles of Muscle Energy Treatment 10/30 Fascial Planes/Neck Describe the craniovertebral joints that allow for flexion/extension of the head & neck and those that allow for rotation of the head. Describe the ligaments that stabilize the craniovertebral joints List the fascial planes of the neck and describe the spatial relationships of the deep spaces between these planes. List the major structures found in these fascial planes and spaces. Describe the spatial relationships of major structures as they pass through the deep neck. Be able to describe pathways for infection through the deep spaces. Atlanto-occipital (AO) joint: - Between C1 and occipital bone Atlanto-axial (AA) joint: - Between C1 and C2 Craniovertebral Ligaments (anterior → posterior) 1. Anterior longitudinal membrane: continuous, becomes– a. Anterior AA membrane b. Anterior AO membrane 2. Apical ligament: connects dens to clivus, limits movement superiorly and inferiorly 3. Cruciate ligament: reinforces dens 4. Posterior longitudinal ligament: becomes– a. Tectorial membrane (superior continuation, connects to occipital bone) 5. Ligamentum flavum: not continuous (staggered/segmented), becomes–  a. Posterior AA membrane b. Posterior AO membrane Fascial Planes Cross Section: 10/31 Embryology of the Head and Neck Describe the structure of the pharyngeal arches, their tissues of origin, and their derivatives Identify the arterial and nervous supply of each pharyngeal arch Identify structures formed by neural crest cells and describe their importance Associate the pharyngeal pouches and clefts with their derivatives Describe the development of the tongue and thyroid gland Explain the roles of the frontonasal prominence, maxillary prominences, and lateral and medial nasal prominences in development of superficial facial structures Pharyngeal Arches * Mesenchyme = Mesoderm + Neural Crest Derivation Arch Aortic Arch Nerve Somitomere & Gives rise to Muscle Arch Maxillary Maxillary a. Trigeminal n. (V2) Somitomere 4; Facial skeleton, mandibular I mastication cartilage, malleus and incus Mandibular Trigeminal n. (V3) (ossicles) Neural Arch II Stapedial aa. Facial n. Somitomere 6; Stapes (ossicle), styloid crest cells (degenerates) facial expression process, stylohyoid ligament, lesser horn and body of hyoid Arch III Carotid aa. Glossopharyngeal n. Somitomere 7; Greater horn and body of stylopharyngeus hyoid Arch IV Left arch of Vagus n. Somitomeres 1/2; Thyroid cartilage aorta intrinsic laryngeals Mesoderm Right subclavian  Arch VI Pulmonary aa. Cricoid cartilage Pharyngeal clefts & pouches Number Pouch (internal) becomes Cleft (external) becomes I Middle ear External ear II Palatine tonsil Cervical sinus (incomplete closure = Branchial cyst) III Inferior parathyroid and thymus IV Superior parathyroid and thymus Cleft lip/palate disorders Disorder Improper closing of Picture Median Cleft Lip Medial nasal prominences Bilateral Cleft Lip and Medial nasal prominence and maxillary prominence Palate Oblique Facial Cleft Lateral nasal prominence and maxillary prominence & Medial nasal prominence and maxillary prominence Cleft Palate Lateral palatal shelves are not long enough 10/31 Cranial Circulation Veins - Dural Venous Sinuses - Space between dural layers where venous blood from brain & dipole (bone) collects before draining to internal jugular vein (IJV) - Superior sagittal sinus → confluence of sinuses → transverse sinus → sigmoid sinus → IJV - Inferior sagittal sinus → straight sinus → confluence of sinuses → transverse sinus → sigmoid sinus → IJV - Cavernous sinus - Drains anterior & lateral skull - Risk of infections passing through sinus from face into cranial cavity - Inflammation → damage to structures within (ICA, CN VI, CNs III-V) - Flows to: - → superior petrosal sinus → transverse sinus → sigmoid sinus → IJV - → inferior petrosal sinus → IJV - Bridging veins - Drain cerebral vv (in subarachnoid space) → dural venous sinuses - Lateral Venous lacunae - Collect & store CSF until it is drained into superior sagittal sinus - Filled w/ arachnoid granulations protruding through dura mater - Emissary veins - Drain extracranial veins → dural venous sinuses - Risk of infection from extracranial environment → intracranial spaces  - Spinal cord vasculature - Network of anterior & posterior spinal veins that run on anterior & posterior surfaces of spinal cord. Drain segmentally Arterial Supply - Brain - Internal Carotid Arteries → 85% - Supplies cerebrum, diencephalon, & orbits (via ophthalmic aa) - ICA Sections: Cervical → Petrous → Cavernous → Cerebral (opthalmic a branches off here) - Cerebral turns 180 degrees to join circle of willis - Vertebral Arteries → 15% - Supplies back part of brain (cerebellum) - Vertebral AA → Basilar a - Basilar branches: - PICA, AICA, Labyrinthine a, pontine aa, superior cerebellar a - Circle of WIllis - NEED TO FILL OUT - Spinal Cord - Vertebral arteries enter foramen magnum - Anterior spinal arteries (from vertebral artery) supply medulla oblongata & anterior spinal cord - Runs down spinal cord as single artery - Posterior spinal arteries (from PICA or vertebral artery) supply posterior spinal cord - Runs down spinal cord as two arteries 10/31 Blood Brain Barrier 1. Describe the Anatomy and Role of the Blood-Brain Barrier (BBB) Anatomy: The BBB is formed by endothelial cells with tight junctions, astrocyte end-feet, and pericytes that collectively create a selective barrier. This structure limits the movement of molecules between the bloodstream and the brain. Role: The BBB regulates the entry of substances into the brain and CSF, allowing essential small, lipid-soluble molecules (e.g., oxygen) to cross passively, while restricting larger, hydrophilic substances unless they are actively transported. This selective permeability protects the brain from toxins, pathogens, and fluctuations in blood composition, maintaining a stable environment for neural function. 2. Describe the Production, Composition, and Flow of Cerebrospinal Fluid (CSF) Production: CSF is primarily produced by the choroid plexus in the lateral, third, and fourth ventricles of the brain through a combination of filtration and active transport. The  production rate is around 20 mL per hour, maintaining a total volume of approximately 150 mL. Composition: Normal CSF is clear, with a low concentration of cells and proteins. It contains 0-5 white blood cells per high-power field, no red blood cells, proteins within normal limits, and glucose at about two-thirds of serum glucose levels. Flow Pathway: CSF flows from the choroid plexus → lateral ventricles → interventricular foramen (Foramen of Monro) → third ventricle → cerebral aqueduct → fourth ventricle. It exits through the medial aperture (Foramen of Magendie) and lateral apertures (Foramina of Luschka) into the subarachnoid space, where it circulates around the brain and spinal cord. CSF is eventually reabsorbed into the bloodstream via arachnoid villi. 3. Describe Normal Values of Cerebrospinal Fluid (CSF) White Blood Cells (WBCs): 0-5 cells per high-power field. Red Blood Cells (RBCs): None in normal CSF. Protein: Levels are low, within the typical physiological range. Glucose: Around two-thirds of the serum glucose concentration. Appearance: Clear and colorless. Any deviation, such as turbidity or discoloration, may indicate an underlying pathology. 4. Describe Basic Pathologies of the CSF System and Intracranial Pressure Subarachnoid Hemorrhage: CSF appears bloody with xanthochromia (yellow tint due to RBC breakdown), indicating the presence of older blood in the CSF. Meningitis: Increased WBC count and protein in CSF, with variations depending on the type of infection (bacterial, viral, fungal). Herpes Encephalitis: Elevated WBCs and protein levels, with positive HSV PCR testing confirming the diagnosis. Idiopathic Intracranial Hypertension: Characterized by elevated CSF opening pressure but normal CSF composition and brain imaging, often leading to symptoms like headache. Hydrocephalus: Increased intracranial pressure due to CSF buildup, with imaging showing enlarged ventricles. Can be obstructive (due to blockage) or communicating (due to impaired reabsorption). Cerebral Venous Thrombosis: Venous outflow obstruction causes elevated CSF pressure, often presenting with headache, venous infarcts, and papilledema. 11/1 Superficial Head 1. Describe the Structure of the Face and Scalp, Including Associated Bones, Cartilages, and Layers  Bones: The facial structure includes the parietal, frontal, temporal, sphenoid, nasal, zygomatic, maxilla, and mandible. Key foramina such as the supraorbital, infraorbital, and mental foramina allow nerves and vessels to pass through. Cartilages: The external nose includes nasal cartilages that help maintain the shape and flexibility of the nasal aperture. Scalp Layers: The scalp has five layers, remembered as "SCALP": ○ Skin ○ Connective tissue (dense) ○ Aponeurosis layer (galea aponeurotica) ○ Loose areolar tissue (provides mobility for the upper layers and is the “danger area” for infection spread) ○ Pericranium (periosteum on the skull). 2. Describe the Muscles of Facial Expression: Actions, Innervation, and General Attachments Muscles: The muscles of facial expression are responsible for moving the skin and creating expressions. Major muscle groups include: ○ Orbital Group: Surrounds the eyes; includes orbicularis oculi, which closes the eyelids. ○ Nasal Group: Moves the nose and includes muscles such as nasalis. ○ Oral Group: Moves the mouth and includes muscles like orbicularis oris (closes the lips) and zygomaticus major (elevates the mouth corner). ○ Occipitofrontalis: Raises the eyebrows and wrinkles the forehead. ○ Platysma: Tenses the skin of the neck. Innervation: These muscles are innervated by the Facial Nerve (CN VII), which branches within the parotid gland into temporal, zygomatic, buccal, marginal mandibular, and cervical branches. 3. Describe the Flow of Blood Through This Region: External and Internal Carotid Arteries and Their Branches, Major Veins Feeding into the Jugular Veins Arterial Supply: ○ External Carotid Artery (ECA): Supplies most superficial structures of the face and scalp through branches like: Facial Artery: Supplies the face, including the upper and lower lips. Maxillary Artery: Supplies deep facial structures. Superficial Temporal Artery: Supplies the scalp. Occipital Artery: Supplies posterior scalp. Posterior Auricular Artery: Supplies the auricle and scalp behind the ear. ○ Internal Carotid Artery (ICA): Supplies the brain and orbit, with the Ophthalmic Artery branching off to supply the eyes and nearby structures. Venous Drainage: ○ Superficial veins like the Facial Vein drain into the Internal Jugular Vein (IJV).  ○ The Superficial Temporal Vein and Maxillary Vein join to form the Retromandibular Vein, which drains into the IJV. ○ Danger Triangle of the Face: Blood from this region (nose and upper lip) can drain into both superficial and deep veins, providing a route for infections to spread to intracranial structures. 4. List the Cranial Nerves Relevant to This Region, Their Structure, and Their Functional Roles: CN V, VII, IX Trigeminal Nerve (CN V): Provides sensory innervation to the face and motor innervation to muscles of mastication. ○ Divides into three branches: Ophthalmic (V1): Sensory to forehead, scalp, and upper eyelid. Maxillary (V2): Sensory to the cheek, upper lip, and nasal cavity. Mandibular (V3): Sensory to lower face and motor to muscles of mastication. Facial Nerve (CN VII): Motor innervation to the muscles of facial expression and part of the platysma. It also provides taste sensation to the anterior two-thirds of the tongue. ○ The facial nerve branches within the parotid gland into temporal, zygomatic, buccal, marginal mandibular, and cervical branches. Glossopharyngeal Nerve (CN IX): Provides sensory innervation to the posterior third of the tongue and oropharynx, and parasympathetic innervation to the parotid gland through the auriculotemporal nerve. 5. Describe the Anatomy of the Parotid Gland: Its Structural Relations, Connection with the Oral Cavity, and Parasympathetic Innervation Structure and Location: The parotid gland is the largest salivary gland, located in front of the ear and extending to the angle of the mandible. It is superficial and partly wraps around the masseter muscle. Connection with the Oral Cavity: The parotid duct (Stensen’s duct) exits the gland, pierces the buccinator muscle, and opens into the oral cavity near the upper second molar. Parasympathetic Innervation: ○ Glossopharyngeal Nerve (CN IX) provides parasympathetic fibers to the parotid gland. ○ The fibers travel to the otic ganglion, where they synapse, and then reach the gland via the auriculotemporal nerve. 11/1 Histology of the Nerve Cells 1. Identify Gray and White Matter Based on Constituent Elements  Gray Matter: Contains neuron cell bodies (somata), dendrites, and unmyelinated axons, forming the cerebral and cerebellar cortex and certain deep brain structures like the basal ganglia. Gray matter has a fine texture due to the dense network of dendrites and unmyelinated fibers (neuropil). White Matter: Composed mainly of myelinated axons, which connect different CNS regions. It appears coarse in texture due to the myelin surrounding axons. White matter in the brain is located beneath the gray matter and includes tracts that link the cortex to other CNS regions. 2. Describe a Nerve Cell and Its Parts: Cell Body, Dendrites, Axons, Nissl Substance Cell Body (Soma or Perikaryon): The central part of a neuron containing the nucleus, Nissl bodies (rough endoplasmic reticulum involved in protein synthesis), and other organelles necessary for cellular function. Dendrites: Branch-like structures extending from the cell body, serving as the receptive field for signals from other neurons. They can contain Nissl substance. Axon: A single, elongated projection from the neuron that transmits electrical impulses to other neurons or effector cells. It is the principal output pathway of the neuron. Nissl Substance: Composed of rough endoplasmic reticulum and ribosomes, it is present in the soma and dendrites and is essential for protein synthesis in the neuron. 3. Identify Golgi Type I Cells (Large Projection Nerve Cells), Their Functions, and Locations Golgi Type I Cells: These are large projection neurons that send signals over long distances. Examples include: ○ Alpha Motor Neurons: Located in the brainstem and spinal cord (ventral horn), these neurons send axons to the peripheral nervous system to stimulate muscle fibers. ○ Pyramidal Cells: Found in the cerebral cortex, particularly in motor areas, and are involved in motor control and cognitive processing. They integrate synaptic inputs and send axons to subcortical structures, including the spinal cord. ○ Purkinje Cells: Located in the cerebellum, these cells are the only output neurons of the cerebellar cortex. They play a crucial role in motor coordination by modulating the activity of deep cerebellar nuclei. 4. Know the Function of Golgi Type II Cells (Small Interneurons) and Their Locations Golgi Type II Cells: These are small interneurons found only in the CNS and are responsible for integrating signals locally. They connect sensory neurons and motor neurons or other interneurons. ○ Function: They help maintain stability in neural circuits by inhibiting excessive excitation and organizing brain activity, contributing to cognitive functions.  ○ Locations: Found in various brain regions, including the cerebral cortex (where they exist in multiple forms, like basket cells, stellate cells, and others) and in the cerebellum, where they assist in fine-tuning neuronal signals. 5. Name Types of CNS Support Cells and Their Functions Astrocytes: Provide structural support, regulate the neural environment, and contribute to the blood-brain barrier by surrounding blood vessels and neurons. Oligodendrocytes: Predominantly in white matter, they produce the myelin sheath around CNS axons, supporting multiple neurons and improving signal transmission. Microglia: Act as the brain’s immune cells, becoming phagocytic to remove cellular debris and respond to infection or injury. Ependymal Cells: Line the ventricles of the brain and the central canal of the spinal cord. They are involved in the production and circulation of cerebrospinal fluid (CSF) and help maintain its flow. 11/1 Synaptic Transmission and Neural Reflexes 1) Identify the characteristic cellular features of neurons Neurons have distinct cellular features: Dendrites: Serve as receptive fields, receiving incoming signals. Axons: Fiber projections that conduct electrical signals from the cell body. Myelin: Insulating sheath around axons produced by glial cells, which speeds up electrical transmission and is stabilized by protein interactions. 2) Describe the ionic basis of each of the following local graded potentials Excitatory Post-Synaptic Potential (EPSP): Caused by the opening of ligand-gated cation channels, allowing Na+ or Ca2+ influx, leading to a small depolarization. Inhibitory Post-Synaptic Potential (IPSP): Typically arises from the opening of Cl- channels (e.g., GABA or glycine receptors), causing hyperpolarization. End Plate Potential (EPP): Occurs at neuromuscular junctions when acetylcholine (ACh) binds to nicotinic receptors, leading to Na+ influx and local depolarization. Receptor (Generator) Potential: Arises in sensory neurons when receptors detect stimuli, leading to local depolarization due to Na+ influx. 3) Contrast the generation and conduction of graded potentials (EPSP and IPSP) with those of action potentials  Graded Potentials (EPSP and IPSP): Generated by ligand-gated ion channels, are small, local changes in membrane potential, and decrease with distance. They are variable in size and duration and do not follow an all-or-none law. Action Potentials: Generated by voltage-gated channels, involve a large, rapid change in membrane potential, propagate without decrement along the axon, and are all-or-none. 4) Describe the ionic basis of an action potential Phase 1 (Depolarization): Voltage-gated Na+ channels open, leading to a rapid influx of Na+ and depolarization. Phase 2 (Plateau in some cells, like cardiac muscle): Voltage-gated Ca2+ channels open, maintaining depolarization. Phase 3 (Repolarization): K+ efflux through voltage-gated K+ channels returns the membrane potential to its resting state. Afterhyperpolarization: Caused by prolonged K+ efflux, often mediated by Ca2+-activated K+ channels. 5) Define and identify the following regions on a neuron diagram Dendrites: Branched projections that receive signals. Axon: Long projection that carries signals away from the soma. Axon Hillock: The initial segment of the axon, where action potentials are generated. Soma: The cell body containing the nucleus and metabolic machinery. Axodendritic Synapse: A synapse between the axon of one neuron and the dendrite of another. 6) Describe the functional role of myelin in promoting saltatory conduction Myelin increases conduction velocity by insulating the axon, reducing membrane capacitance, and increasing membrane resistance. This forces action potentials to “jump” between the Nodes of Ranvier, where Na+ channels are concentrated, enabling saltatory conduction. 7) Define membrane capacitance and how it affects current spread in myelinated and unmyelinated neurons Membrane Capacitance (Cm): The ability of the membrane to store charge. ○ In myelinated neurons: Lower Cm allows faster signal propagation because less charge is stored on the membrane. ○ In unmyelinated neurons: Higher Cm slows conduction due to increased charge storage. 8) Compare conduction velocities in a compound nerve based on diameter and myelination  Increased Axon Diameter: Reduces axial resistance, increasing conduction velocity. Myelination: Decreases membrane capacitance and increases membrane resistance, both of which enhance conduction velocity by promoting saltatory conduction. 9) Describe how axon diameter influences axial and membrane resistances, membrane capacitance, and conduction velocity Larger Axon Diameter: Decreases axial resistance (Ra) and slightly decreases membrane resistance (Rm) due to increased surface area, which allows faster longitudinal current flow and higher conduction velocity. Membrane Capacitance: Proportionally increases with diameter but is reduced by myelination, enhancing conduction further. 10) Describe chemical neurotransmission in the correct sequence 1. Action Potential Arrival: Depolarization reaches the presynaptic terminal. 2. Ca2+ Influx: Voltage-gated Ca2+ channels open, allowing Ca2+ into the cell. 3. Vesicle Fusion: Ca2+ triggers SNARE-mediated vesicle fusion with the membrane. 4. Neurotransmitter Release: Neurotransmitters are released into the synaptic cleft via exocytosis. 5. Binding to Postsynaptic Receptors: Neurotransmitters bind to receptors on the postsynaptic membrane, generating a graded potential. 11) Define the characteristics of a classical neurotransmitter A classical neurotransmitter must: Be synthesized in neurons. Be released in response to physiological stimuli. Mimic endogenous effects if applied externally. Have its action terminated by reuptake or enzymatic degradation. 12) Describe synthetic pathways, inactivation, and receptor mechanisms for key neurotransmitters Catecholamines (dopamine, norepinephrine, epinephrine): Synthesized from tyrosine, inactivated by reuptake and enzymes (COMT and MAO). Act on G-protein-coupled receptors. ○ Dopaminergic: D1 & D5: interact w/Gs; stimulates adenylyl cyclase, cAMP formation, and PKA D2, D3, D4: interact w/Gi/o; inhibit adenylyl cyclase, cAMP formation, and PKA ○ Adrenergic & Noradrenergic:  Acetylcholine: Synthesized from choline and acetyl-CoA; broken down by acetylcholinesterase. Acts on muscarinic and nicotinic receptors. Serotonin: Synthesized from tryptophan, inactivated by reuptake and MAO. Acts on various receptors (e.g., 5-HT receptors). GABA and Glycine: GABA synthesized from glutamate; both act on inhibitory receptors (GABA on GABAA_AA​, GABAB_BB​, GABAC_CC​, and glycine on glycine receptors). Glutamate: Synthesized from glutamine, reuptaken by transporters. Acts on NMDA, AMPA, and kainate receptors. Neuropeptides: Synthesized from precursor proteins; inactivated by proteolysis. 13) Diagram steps for channel protein phosphorylation upon Gs protein activation 1. Gs Protein Activation: Neurotransmitter binds to receptor. 2. Adenylyl Cyclase Activation: Gs activates adenylyl cyclase. 3. cAMP Formation: Increased cAMP production. 4. PKA Activation: cAMP activates Protein Kinase A (PKA). 5. Channel Phosphorylation: PKA phosphorylates channel protein, modulating its function. 14) Diagram steps for Ca2+ increase and Protein Kinase C activation via Gq protein 1. Gq Activation: Ligand binding activates Gq protein. 2. Phospholipase C (PLC) Activation: Gq activates PLC. 3. DAG and IP3 Formation: PLC converts PIP2 to DAG and IP3. 4. Ca2+ Release: IP3 causes Ca2+ release from intracellular stores. 5. PKC Activation: Ca2+ and DAG activate Protein Kinase C (PKC). 15) Diagram steps for enhanced K+ influx, decreased Ca2+ influx, and neurotransmitter release reduction via Gi/o protein 1. Gi/o Activation: Receptor-ligand binding activates Gi/o protein. 2. Inhibition of Adenylyl Cyclase: Reduces cAMP production. 3. K+ Channel Modulation: βγ subunits activate K+ channels, increasing K+ efflux. 4. Ca2+ Channel Inhibition: Reduced Ca2+ influx. 5. Reduced Neurotransmitter Release: Lower Ca2+ decreases vesicle fusion probability. 16) Describe the physiological mechanism underlying the patellar tendon reflex 1. Sensory Detection: Muscle spindle detects tendon stretch. 2. Afferent Impulse: Signal transmitted to spinal cord via afferent neurons. 3. Synapse with Motor Neuron: Afferent neuron excites motor neuron for the quadriceps. 4. Quadriceps Contraction: Motor neuron releases acetylcholine, contracting the muscle. 5. Reciprocal Inhibition: Renshaw cells release glycine onto the motor neuron controlling antagonistic hamstring muscle, inhibiting it and preventing flexion. 11/1 Emergency Med Case Workshop E-FAST (Extended Focused Assessment with Sonography in Trauma): is a rapid ultrasound exam used in trauma settings to identify life-threatening injuries. It evaluates: 1. Pericardial Space for cardiac tamponade. 2. Pleural Cavities for pneumothorax and hemothorax. 3. Peritoneal Cavities for free fluid (suggestive of bleeding). 4. Lung Bases for pneumothorax. The "Extended" part includes lung views to detect pneumothorax, broadening the original FAST exam, which focused only on the abdomen and pericardium. Spinal cord injuries: 1º spinal cord injury: injury occurs at the time of impact 2º spinal cord injury: occurs later from swelling, ischemia, or movement of sharp or unstable boney fragments from the initial injury Spinal shock: temporary loss of all types of spinal cord function distal to the site of the injury 1. Resolves spontaneously over hours-weeks (usually 24 hrs) 2. Complete flaccid paralysis does not always involve permanent injury 3. Manage cervical spine carefully to avoid permanent secondary injury 4. accompanied by: a. Flaccid paralysis distal to site of injury b. Loss of autonomic function i. Hypotension ii. Vasodilation iii. Loss of bowel and bladder function iv. Priapism (erection) v. Loss of thermal control Quadriplegia: complete cervical cord injury resulting in loss of function in all four extremities Paraplegia: complete thoracic or lumbar cord injury with loss of function to the lower extremities Why are secondary spinal injuries unlikely? → takes a large amount of force to break an intact spine (2,000-6,000 N) Cervical whiplash: flexion/extension injury Compression injuries: caused by things like diving into the shallow end of a pool - Axial loading: a force is applied along the vertical axis of the spine, compressing the cervical vertebrae. This can lead to fractures, dislocations,  or spinal cord injury, especially in high-impact scenarios like diving accidents or falls. NEXUS Study: - Established clinical criteria to safely rule out cervical spine injuries without imaging in trauma patients. Patients who meet all five criteria—no midline cervical tenderness, no focal neurologic deficit, normal alertness, no intoxication, and no painful distracting injuries—are at low risk for cervical injury, reducing unnecessary imaging. - Study was highly sensitive and specific Week 2 11/4 Infratemporal Fossa 1. Boundaries of the Infratemporal Fossa Lateral: Formed by the ramus of the mandible. Medial: Defined by the lateral pterygoid plate. Anterior: Bounded by the posterior part of the maxilla. Posterior: Composed of the temporal bone and the styloid process. Superior: The greater wing of the sphenoid bone. These boundaries create a space containing essential nerves, arteries, veins, and muscles involved in mastication and sensory-motor functions of the face. 2. Contents: Muscles of Mastication Temporalis Muscle: ○ Attachments: Temporal lines of the temporal bone to the coronoid process of the mandible. ○ Actions: Elevates the mandible; posterior and horizontal fibers retract the mandible. Masseter Muscle: ○ Attachments: Zygomatic arch to the angle of the mandible. ○ Actions: Elevates the mandible; superficial fibers assist in protrusion.  Medial Pterygoid Muscle: ○ Attachments: Originates from the medial surface of the lateral pterygoid plate and maxillary tuberosity, attaching to the medial ramus. ○ Actions: Elevates and protrudes the mandible; unilateral action enables grinding and lateral movements. Lateral Pterygoid Muscle: ○ Attachments: From the greater wing of the sphenoid and lateral pterygoid plate to the mandibular condyle and joint capsule. ○ Actions: Protracts the mandible and depresses the chin (bilateral); swings jaw toward the opposite side (unilateral), aiding in lateral chewing movements. 3. Maxillary Artery and Branches (Only listing the branches we need to know) The Maxillary Artery has three main sections: ○ Enters the skull: Middle meningeal a.: dura mater and calvaria Inferior alveolar a.: lower teeth and mandibular regions ○ Feeds muscles: Supplies the muscles of mastication ○ Follows nerves: Exits the infratemporal fossa to supply nasal and palatal regions Sphenopalatine a. Descending palatine a. Infraorbital a. INA’s MoM DESPises SPeaking IN_FRAnce 4. Venous Drainage: Pterygoid Venous Plexus The Pterygoid Venous Plexus drains blood from the infratemporal region, channeling it into the maxillary vein and eventually forming the retromandibular vein, which divides into anterior and posterior branches draining into the internal and external jugular veins (IJV and EJV). 5. Nerve Supply: Mandibular Division (V3) and Branches  The Mandibular Division (V3) of the Trigeminal Nerve (CN V) provides sensory and motor functions: ○ Sensory Branches: Include the auriculotemporal, buccal, and lingual nerves, supplying sensation to lower face regions. ○ Motor Branches: Innervate muscles of mastication and other muscles like the tensor tympani, tensor veli palatini, mylohyoid, and anterior digastric. Otic Ganglion: ○ Receives parasympathetic input from the glossopharyngeal nerve (CN IX) and transmits it to the parotid gland via the auriculotemporal nerve. Lingual Nerve and Chorda Tympani: ○ The lingual nerve (V3) carries sensory information and parasympathetic fibers from the chorda tympani (CN VII) to the submandibular ganglion. It also transmits taste sensations from the anterior two-thirds of the tongue. 6. Temporomandibular Joint (TMJ) Structure: The TMJ is a synovial joint between the mandibular condyle and the mandibular fossa of the temporal bone. It contains fibrocartilage-covered articular surfaces and a joint capsule. Ligaments: ○ Temporomandibular (Lateral) Ligament: Prevents posterior dislocation. ○ Stylomandibular Ligament: Provides minimal support. ○ Sphenomandibular Ligament: Offers passive support for the mandible’s weight. Movements: ○ Hinge Movements: Elevation and depression for opening and closing the mouth, facilitated by the temporalis, masseter, and medial pterygoid muscles. ○ Translation Movements: Protrusion and retraction of the jaw occur in the superior TMJ. ○ Lateral Excursion Movements: Side-to-side grinding and chewing, involving temporalis and pterygoid muscles. 11/4 Eye and Orbit 1. Orbit and Eye Structures Bones of the Orbit: The walls of the orbit serve as boundaries, with thin medial and inferior walls that are prone to fractures and infections. These walls also connect to nearby sinuses. Eyelids (Palpebrae): Layers include skin, subcutaneous tissue, orbicularis oculi muscle, tarsus, tarsal glands, and conjunctiva. Bulbar Fascia (Tenon’s Capsule): A sheath surrounding the eye that provides support and allows movement. Suspensory Ligament of Lockwood: A dense connective tissue structure supporting the eye, preventing downward displacement.  Lacrimal Apparatus: Produces and drains tears; includes the lacrimal gland, lacrimal sac, and nasolacrimal duct. 2. Eye Layers and Intrinsic Structures Fibrous Layer: Sclera (providing eye structure) and cornea (primary refractive component, highly sensitive). Vascular Layer (Uvea): Includes the choroid, ciliary body, and iris. Sensory Layer (Retina): Contains photoreceptors, with specialized areas such as the optic disc and fovea. Inner Structures: The lens (for focusing light), aqueous and vitreous chambers (filled with humors), and the ciliary body, which controls lens shape for accommodation. 3. Intrinsic Eye Muscles Iris Muscles: Sphincter pupillae (parasympathetic control) and dilator pupillae (sympathetic control) regulate pupil size. Ciliary Muscle: Controls lens shape for focusing; relaxation flattens the lens (sympathetic response), while contraction rounds it (parasympathetic response). 4. Extraocular Muscles and Eye Movements Seven Extraocular Muscles: Six move the eyeball, and one (levator palpebrae superioris) raises the eyelid. H-Test: Clinical test used to isolate and assess the primary function of each extraocular muscle by moving the eye in an “H” pattern. 5. Neurovasculature Nerves: ○ Oculomotor (CN III), Trochlear (CN IV), and Abducent (CN VI) control extraocular muscles. ○ Ophthalmic Branch of Trigeminal (V1) provides sensory innervation. ○ Ciliary Ganglion: Parasympathetic relay for pupil constriction and lens accommodation. Blood Supply: Primarily from the ophthalmic artery, with branches like the central retinal artery, ciliary arteries, and muscular branches supplying the eye and orbit. Venous Drainage: Blood from the eye and orbit drains through the superior and inferior ophthalmic veins to the cavernous sinus, an area vulnerable to infection due to venous connections with facial regions. 6. Clinical Notes  Common Pathologies: Increased intraocular pressure (glaucoma), oculomotor palsies, and the “triangle of danger” region, which relates to cavernous sinus thrombosis due to infections spreading from the face to the sinus. 11/4 Anatomy/Histology of the Ear 1. External Ear Structure and Functions: The external ear, which includes the auricle and external auditory canal, collects sound waves, aids in sound localization, and transmits sound to the middle ear. Innervation: Sensory innervation is provided by branches of the facial nerve (CN VII) and other nerves, such as the auriculotemporal nerve. Muscles: Small muscles like auricularis muscles play a minimal role in ear movement. 2. Middle Ear Functions: Converts airborne sound waves into mechanical vibrations suitable for the fluid-filled inner ear (impedance matching) and protects the inner ear from loud sounds. Key Features: ○ Auditory Ossicles: Malleus, incus, and stapes transmit vibrations from the tympanic membrane to the oval window. ○ Walls and Openings: The tympanic membrane forms the lateral boundary, while the medial wall features the oval and round windows. The roof is the tegmen tympani, and the anterior wall contains the pharyngotympanic (Eustachian) tube. ○ Eustachian Tube: Equalizes middle ear pressure with external air pressure, with opening facilitated by muscles like the tensor veli palatini. Dysfunction can lead to ear infections. Innervation: ○ Chorda Tympani: A branch of CN VII that passes through the middle ear, contributing to taste and salivary functions. ○ Glossopharyngeal Nerve (CN IX): Supplies sensory innervation to the middle ear mucosa and transmits parasympathetic fibers to the parotid gland. Middle Ear Muscles: ○ Tensor Tympani: Dampens sound by pulling on the malleus; innervated by a branch of the mandibular nerve (V3). ○ Stapedius: Limits stapes movement to dampen sound, innervated by CN VII. 3. Inner Ear Functions: Processes sound (hearing) and maintains balance. Anatomical Structure:  ○ The bony labyrinth is a structure filled with perilymph, containing the cochlea (for hearing), vestibule, and semicircular canals (for balance). ○ The membranous labyrinth within it contains endolymph, organized into regions such as the cochlear duct, semicircular ducts, saccule, and utricle. Cochlea: ○ Contains three chambers (scala vestibuli, scala media, and scala tympani) and the Organ of Corti, where hair cells convert mechanical vibrations into neural signals sent to the brain by the cochlear nerve (part of CN VIII). ○ Frequency Coding: High-frequency sounds are processed near the base (oval window) of the cochlea, while low frequencies are detected near the apex (helicotrema). Vestibular System: ○ Semicircular Canals: Detect rotational movements (pitch, roll, yaw) with specialized hair cells in the crista ampullaris. ○ Otolith Organs (Utricle and Saccule): Detect linear acceleration and head position relative to gravity using hair cells embedded in an otolithic membrane with small crystals (otoconia). 4. Sound Transmission Pathway 1. Sound Waves enter the ear canal. 2. Tympanic Membrane vibrates in response. 3. Ossicles (malleus, incus, stapes) transmit and amplify vibrations to the oval window. 4. Oval Window: Vibration creates pressure waves in perilymph within the scala vestibuli. 5. Cochlear Duct: Pressure displaces the vestibular membrane, moving endolymph and activating the basilar membrane. 6. Basilar and Tectorial Membranes: Movement stimulates hair cells, generating neural signals sent to the cochlear nerve. 7. Round Window: Dissipates remaining pressure waves from the scala tympani, completing the cycle. 5. Vestibular System and Balance Semicircular Canals detect angular acceleration (head rotations). Utricle and Saccule detect linear acceleration; movement of otoconia influences hair cells in these structures, signaling changes in head position. Clinical Correlation: Damage to the vestibular system can lead to dizziness, vertigo, and balance issues. 6. Vascular Supply The inner ear is primarily supplied by the labyrinthine artery, a branch of the anterior inferior cerebellar artery (AICA), which divides into vestibular and cochlear branches. 11/5 Auditory and Vestibular Systems 1. Learning Objectives Understanding the auditory pathway from the inner ear to the auditory cortex. Examining the vestibular pathways from the inner ear and its CNS connections. Describing auditory and vestibulo-ocular reflexes. Recognizing clinical correlations for each pathway. 2. Auditory Pathway Overview The auditory system relies on cranial nerve VIII (vestibulocochlear nerve) and includes structures like the outer ear, middle ear, and cochlea. Hair Cells: Specialized mechanoreceptors with stereocilia and kinocilia respond to mechanical stimuli, releasing neurotransmitters to excite CN VIII neurons. Cochlear Pathway: ○ Sound processing begins with hair cells in the cochlea’s spiral organ of Corti. ○ First-order neurons synapse in the spiral ganglion and cochlear nuclei before processing at higher levels like the superior olivary nucleus, which contributes to sound localization. Auditory Reflexes: ○ Reflexive muscle responses, such as the tensor tympani and stapedius reflexes, protect the cochlea from loud sounds. 3. Higher-Level Processing The auditory pathway includes several relay points: ○ From the superior olivary nucleus, neurons continue through structures like the lateral lemniscus, inferior colliculus, and medial geniculate nucleus in the thalamus, eventually reaching the primary auditory cortex in the superior temporal gyrus. Auditory Reflexes and Sound Localization: ○ Reflexive responses aid in protecting hearing. ○ The superior olivary nucleus facilitates binaural hearing for sound directionality. Lesions and Disorders: ○ Damage to the auditory pathway can cause partial hearing loss, tinnitus, and issues with pitch processing. 4. Vestibular Pathway Overview Vestibular System: ○ Comprises semicircular canals (anterior, posterior, lateral) and otolith organs (saccule and utricle), essential for balance and spatial orientation. ○ Vestibular hair cells detect movement, influencing balance and posture through the vestibulospinal tract.  Pathways: ○ First-order neurons in the vestibular ganglia connect to four nuclei (superior, inferior, lateral, and medial). ○ Descending pathways (lateral and medial vestibulospinal tracts) help regulate posture by controlling muscle tone in response to head movements. ○ Ascending pathways project to eye movement control centers (CN III, IV, and VI), aiding in head-eye coordination (vestibulo-ocular reflex). 5. Vestibulo-Ocular Reflex (VOR) This reflex stabilizes gaze by compensating for head movements. Nystagmus, an involuntary eye movement, can occur with vestibular dysfunction, showing slow movement followed by rapid corrective motion. 6. Clinical Relevance Benign Paroxysmal Positional Vertigo (BPPV): ○ Caused by otoliths dislodged into the semicircular canals, BPPV leads to vertigo and unintended vestibular activation. 11/6 Physiology–Audition Highlighted = Dr. Bi emphasizes it is most likely to be tested on Overview of Hearing Hearing involves the conversion (transduction) of sound waves into electrical energy, which is then processed by the nervous system. The document outlines the structures responsible for this process, from the external ear to the auditory cortex. Structures and Functions 1. External Ear: ○ Acts as a sound collector. ○ The pinna and concha play roles in localizing sound sources based on amplitude and frequency variations. 2. Middle Ear: ○ Contains the tympanic membrane (eardrum) and auditory ossicles (malleus, incus, stapes) that transmit sound from air to the fluid-filled cochlea. ○ Facilitates energy conduction and sound pressure amplification. ○ Has protective mechanisms like the tympanic reflex to dampen loud sounds. 3. Inner Ear: ○ Comprises structures like the cochlea, which contains fluid-filled ducts: scala vestibuli, scala media, and scala tympani.  ○ The basilar membrane acts as a frequency analyzer i. Closer to round window: narrow/stiffer → high frequency sensitivity ii. Apex/end: wider/flexible → low frequency sensitivity ○ Hair cells in the organ of Corti convert mechanical vibrations into neural signals. Conversion of Mechanical to Electrical Signals Hair cells bend against the tectorial membrane, opening K+ channels and causing depolarization. ○ Influx of K+ depolarizes the hair cells → opening of Ca2+ channels → glutamate release → action potential occurs in afferent cochlear nerves → message goes to brain This process leads to the release of neurotransmitters and the initiation of action potentials in cochlear nerve fibers, transmitting sound information to the brain. Hair Cell Degeneration Hair cell degeneration and severe hearing loss can be induced by medications like kanamycin (antibiotic) and furosemide (loop diuretic) Auditory Processing in the Brain The superior olivary complex (SOC) is key for sound localization, using interaural time differences (ITD) and interaural loudness differences (ILD) for spatial orientation. ○ Medial superior olive (MSO) → interaural time difference (ITDs); low frequency sounds ○ Lateral superior olive (LSO) → interaural level difference (ILDs); high frequency sounds Hearing Loss Types and Causes 1. Conductive Hearing Loss: ○ Occurs due to issues in the external or middle ear, such as otitis media or ossification, or lesions in the auricle, EAC, or middle ear ○ Rinne and Weber tests help differentiate between conductive and sensorineural losses. 2. Sensorineural Hearing Loss (SNHL): ○ Results from damage to cochlear hair cells or neural pathways. ○ Can be caused by exposure to loud noise, aging (presbycusis), genetic factors, or ototoxic drugs. 3. Mixed Hearing Loss: ○ Involves both conductive and sensorineural elements.  4. Cholesteatoma: benign middle ear tumor that causes conductive hearing loss & is repaired through surgery ○ Usually accompanied by a perforated TM Key Concepts and Tests Tonotopic organization starts at the basilar membrane and continues throughout the auditory pathway. Tests such as the Rinne and Weber tuning fork tests assess hearing capabilities and differentiate between loss types. 11/6 Oral Cavity Overview and Learning Objectives The material outlines the structural framework, muscle functions, blood flow, and innervation of the oral cavity and oropharynx. Key learning objectives include understanding: The skeletal framework and boundaries of the oral cavity. Muscles involved in tongue and soft palate movements and their innervation. The flow of blood through the region and the role of major veins and arteries. The cranial nerves relevant to the oral cavity and oropharynx. Key Anatomical Structures 1. Skeletal Framework: ○ Includes the palatine process of the maxilla, horizontal plate of the palatine, mandibular foramen, and various foramina (e.g., greater and lesser palatine). ○ The mandible’s structure features parts such as the mylohyoid groove, genial tubercles, and sublingual/submandibular fossae. 2. Teeth and Gingiva: ○ Teeth are arranged in the maxillary and mandibular arches, with periodontal ligaments securing them. ○ The document discusses the universal numbering system and gingival structures. 3. Oral Cavity and Vestibule: ○ Structures include the vermilion border, labial frenulum, oral vestibule, buccal mucosa, and parotid papilla. Muscles and Functions Tongue Muscles: ○ Includes both intrinsic and extrinsic muscles (e.g., genioglossus, hyoglossus, and styloglossus).  ○ The hypoglossal nerve (CN XII) innervates most tongue muscles, except the palatoglossus (innervated by the vagus nerve, CN X). Soft Palate Muscles: ○ Comprises muscles like the tensor and levator veli palatini, musculus uvulae, and palatoglossus. ○ Innervated mainly by the vagus nerve, except the tensor veli palatini (innervated by the mandibular branch of the trigeminal nerve, CN V3). Blood Flow and Innervation Arteries and Veins: ○ Key vessels include branches of the external carotid artery, such as the greater and lesser palatine arteries, which also have corresponding veins. Nerve Supply: ○ The oral cavity is served by multiple cranial nerves: Trigeminal nerve (CN V): Sensory innervation through its maxillary (V2) and mandibular (V3) branches. Facial nerve (CN VII): Provides parasympathetic innervation via the chorda tympani. Glossopharyngeal (CN IX) and vagus nerve (CN X): Involved in taste and motor functions. Clinical Correlations Nerve Damage: ○ Lesions of the hypoglossal nerve result in tongue deviation towards the injured side during protrusion. ○ Vagus nerve damage causes the uvula to deviate away from the affected side. Inferior Alveolar Nerve Block: ○ Commonly used for dental procedures involving the mandible. 11/6 Histology of Tongue and Salivary Gland Overview and Learning Objectives The content focuses on: The epithelial structures of the oral cavity and lips. The types and roles of lingual papillae on the tongue. The anatomy of salivary glands, including their secretory units and duct systems. The characteristics of saliva and its role in oral health. Oral Mucosa Types of Mucosa:  ○ Lining Mucosa: Found on mobile surfaces such as the inner lips and cheeks; consists of non-keratinized stratified squamous epithelium. ○ Masticatory Mucosa: Covers areas like the hard palate and gingiva; variably keratinized and firmly attached to underlying bone. ○ Specialized Mucosa: Covers the dorsum of the tongue and includes taste-related structures; also variably keratinized. Structural Features of the Lips The lips have a dual structure: ○ Outer Surface: Keratinized stratified squamous epithelium (similar to skin). ○ Inner Surface: Non-keratinized stratified squamous epithelium, with minor salivary glands embedded within the submucosa. The transition zone between the inner and outer lip, known as the vermillion zone, is highly vascularized, contributing to the reddish lip color. Tongue and Lingual Papillae Types of Papillae: ○ Filiform Papillae: Most abundant; thread-like, providing surface friction but lacking taste buds. ○ Fungiform Papillae: Mushroom-shaped, second most common, with taste buds primarily innervated by the facial nerve (CN VII). ○ Circumvallate Papillae: Large, located at the back of the tongue, surrounded by a trough with taste buds innervated by the glossopharyngeal nerve (CN IX); contain von Ebner’s glands that secrete serous fluid to cleanse the area.  ○ Foliate Papillae: Leaf-like structures on the lateral tongue edges, containing taste buds innervated by both CN VII and IX. Taste Buds: Found in all papilla types except filiform, involved in taste sensation. Salivary Glands Types: ○ Parotid Gland: Composed solely of serous acini, responsible for 25% of resting saliva production, producing a watery, enzyme-rich secretion. ○ Submandibular Gland: Contains mixed acini with a predominance of serous units, contributing approximately 70% of resting saliva. ○ Sublingual Gland: Primarily mucous acini with minor serous components, producing about 5% of resting saliva. Secretory Units and Histological Features Serous Acini: Produce watery secretions containing digestive enzymes and antimicrobial agents. Mucous Acini: Produce viscous secretions for lubrication and binding. Serous Demilunes: Crescent-shaped formations on mucous acini, appearing as artifacts of histological preparation. Myoepithelial Cells: Contractile cells that aid in the expulsion of secretions from acini. Duct System 1. Intercalated Ducts: Collect initial secretions; lined with low cuboidal cells. 2. Intralobular (Striated) Ducts: Receive fluid from intercalated ducts; lined with columnar cells. 3. Interlobular (Excretory) Ducts: Transport saliva to the main duct; lined with stratified columnar or cuboidal cells. 4. Main Excretory Duct: The final pathway for secretions before they enter the oral cavity. Functional Role of Saliva Saliva Composition and Functions: ○ Lubricates and binds food. ○ Initiates starch digestion via amylase.  ○ Provides antimicrobial properties. ○ Buffers the oral environment to maintain pH balance. 11/7 Nasal Cavity Key Points: Functions of the Nasal Cavity: ○ Olfaction: Enables the sense of smell. ○ Respiration: Facilitates breathing. ○ Filtration and Humidification: Filters dust and humidifies inspired air. ○ Secretion Management: Receives and eliminates secretions from nasal mucosa, sinuses, and nasolacrimal ducts. Anatomical Structure: ○ External Nose: Includes nasal bones, lateral cartilages, alar cartilages, and septal cartilage. ○ Nasal Septum: Composed of septal cartilage, the perpendicular plate of the ethmoid bone, and the vomer, with contributions from the maxilla and palatine bones. ○ Lateral Wall: Features structures such as the ethmoid's superior and middle conchae, inferior nasal concha, and related bones like the palatine and maxilla. Nasal Cavities and Paranasal Sinuses: ○ Paranasal Sinuses: Four sinuses (frontal, ethmoidal, sphenoidal, and maxillary) that develop from nasal cavity outgrowths and are lined with mucosa. ○ Drainage: Sinuses open into the nasal cavities through various meatuses and ducts, with the maxillary sinus being the largest. ○ Key Openings Sphenoethmoidal Recess: Contains the sphenoid sinus opening. Sphenoidal sinus → Sphenoethmoidal recess Superior Meatus: Drains posterior ethmoidal cells. Posterior ethmoid air cells → Superior meatus  Middle Meatus: Drains the frontal, anterior ethmoid, and maxillary sinuses. Features the ethmoidal bulla and semilunar hiatus for sinus openings. Middle ethmoid air cells → Ethmoid bulla Anterior ethmoid air cells → Semilunar hiatus Inferior Meatus: Contains the nasolacrimal duct. Lacrimal gland → Opening for nasolacrimal duct Innervation: ○ Cranial Nerves: Involves CN I (olfactory), CN V (trigeminal branches), and CN VII, with contributions from the deep petrosal nerve. ○ Pterygopalatine Ganglion: Provides parasympathetic innervation. ○ Sensory and Special Sensory Functions: Include olfaction and general sensory pathways. Vascular Supply: ○ Arterial Supply: Derived from branches like the sphenopalatine artery (maxillary), ophthalmic artery (internal carotid), and external carotid contributions. The greater palatine a. and sphenopalatine a. anastamose in the incisive canal ○ Venous Drainage: Nasal vein → cranial venous channels Passes through the foramen cecum Pterygoid plexus → cavernous sinus 11/7 Pharynx Pharynx Structure: Divisions: ○ Nasopharynx: Connects to the nasal cavity via the choanae and contains the pharyngeal tonsil (adenoid) and the opening of the auditory tube (pharyngotympanic or Eustachian tube). ○ Oropharynx: Bordered by the soft palate and epiglottis, featuring the palatine and lingual tonsils and the oropharyngeal isthmus.  ○ Laryngopharynx (Hypopharynx): Extends from the epiglottis to the esophagus, continuous with the larynx and containing structures like the piriform recess. Associated Structures: ○ The skeletal framework includes the temporal and occipital bones. ○ Key features include the torus tubarius, pharyngeal recess, and salpingopharyngeal fold. Musculature: Pharyngeal Constrictors: Superior, middle, and inferior constrictors insert at the pharyngeal raphe and tubercle, assisting in swallowing. Innervated primarily by the vagus nerve (CN X). Pharyngeal Elevators: Include muscles like the stylopharyngeus (innervated by the glossopharyngeal nerve, CN IX), contributing to elevating the pharynx during swallowing. Innervation: Nerves and Function: ○ Pharyngeal Plexus (CN IX and CN X) provides motor and sensory innervation to the pharynx. ○ Glossopharyngeal nerve (CN IX): Provides sensory input and innervates the stylopharyngeus muscle. ○ Vagus nerve (CN X): Supplies motor innervation to most pharyngeal muscles. Gag Reflex: Involves afferent input via CN IX and efferent response through CN X, stimulating contraction of pharyngeal and soft palate muscles. Blood Supply: Arterial Supply: Primarily from branches of the external carotid artery, including the ascending pharyngeal, superior thyroid, and facial arteries (with specific contributions like the tonsillar and ascending palatine branches). Veins: Drain into the internal jugular vein through the pharyngeal venous plexus and connections with the pterygoid plexus and facial vein. Tonsils: Waldeyer’s Tonsillar Ring: Comprises the pharyngeal (adenoid), tubal, palatine, and lingual tonsils, forming a ring around the pharynx that plays a role in immune defense. Clinical Note: Innervation Exceptions: The stylop