A&P 1 Final PDF
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Summary
These notes cover the human anatomy and physiology of the skull, cranial sinuses, meninges, brain, brain ventricles, cerebrospinal fluid (CSF), and the blood-brain barrier.
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Block 4 26Skull-Meninges 26. Describe the general structure of the skull bones, sutures, and internal fossae 26.1. General structures of skull bones 26.1.1. Orbit (eyes) 26.1.2. Piriform aperture (smell through) 26.1.3. External acoustic meatus (...
Block 4 26Skull-Meninges 26. Describe the general structure of the skull bones, sutures, and internal fossae 26.1. General structures of skull bones 26.1.1. Orbit (eyes) 26.1.2. Piriform aperture (smell through) 26.1.3. External acoustic meatus (ear canal) 26.1.4. Foramen magnum (brain stem enters the base of the skull) 26.2. Sutures of skull bones 26.2.1. Coronal suture 26.2.2. Sagittal suture 26.2.3. Lambdoidal suture 26.2.4. Squamous suture 26.2.5. Pterion (soft spot where all of the sutures come together) 26.3. Internal fossae of skull bones 26.3.1. Anterior cranial fossa 26.3.2. Middle cranial fossa 26.3.3. Posterior cranial fossa 26.4. Locate the major cranial sinuses and understand their function 26.4.1. Ethmoid sinus - Lubricate, Clean, Reduce skull weight, Resonate voice 26.4.2. Maxillary sinus - Weight reduction, Voice resonance, Air humidification, Nasal pressure regulation, Shock absorption, Facial growth, Protection, Craniocerebral trauma 26.4.3. Frontal sinus - Mucus production, Mechanical barrier, Energy absorption, Lightens the skull, Cushions the brain 26.4.4. Sphenoid sinus - Mucus production, Air circulation. Fluid drainage, Lightening the skull, Resonating chamber, Separating structures Surgical access 26.4.5. 26.5. Describe the way different parts of the skull develop and understand the location and function of fontanelles 26.5.1. Intramembranous Ossification - forms directly from tissue 26.5.1.1. The flat bones of the skull, clavicle, and most of the cranial bones 26.5.2. Endochondral Ossification - cartilage first then bone 26.5.2.1. Ethmoid and sphenoid bones as well as the petrous and mastoid portion of the temporal bone and the occipital bone 26.5.3. Anterior Fontanelle - allow for growth of the brain and skull during an infant's first year 26.5.3.1. Palpable during 1st year (closed by 2nd year) 26.5.3.2. If depressed - dehydrated 26.5.3.3. If bulged - increased intracranial pressure 26.5.3.4. 26.6. List the cranial meninges, spaces, and potential hemorrhages 26.6.1. Cranial Meninges and spaces in order from superficial to deep 26.6.1.1. Skin 26.6.1.2. Periosteum 26.6.1.3. Skull 26.6.1.4. Periosteum (Endocranium) 26.6.1.5. Arachnoid mater 26.6.1.6. Dura mater (Pia mater) 26.6.2. Hemorrhages 26.6.2.1. Epidural - trauma causes LOC - half moon 26.6.2.2. Subarachnoid - thunderclap headache - bright middle 26.6.2.3. Subdural - shaken baby syndrome, surprise LOC - Outer edge, not limited by sutures 26.7. Locate the major meningeal folds 26.7.1. Falx cerebri: Separates the left and right cerebral hemispheres 26.7.2. Tentorium cerebelli: Separates the cerebellum and brainstem from the occipital lobes 26.7.3. Falx cerebelli: Separates the left and right cerebellar hemispheres 26.7.4. Diaphragma sellae: Covers the hypophysial fossa of the sphenoid bone 26.7.5. 26.8. Describe the arrangement of brain ventricles, how CSF is made, and the path of CSF circulation 26.8.1. Brain ventricles - a system of four interconnected fluid-filled cavities 26.8.1.1. Two lateral ventricles located deep within each cerebral hemisphere 26.8.1.2. Third ventricle in the diencephalon 26.8.1.3. Fourth ventricle situated in the hindbrain 26.8.1.4. 26.8.2. CSF is primarily produced by the choroid plexus but ependymal cells lining the ventricles also contribute a smaller amount 26.8.3. CSF path of circulation 26.8.3.1. Lateral ventricle 26.8.3.2. Interventricular foramen into third ventricle 26.8.3.3. Cerebral Aqueduct into Fourth Ventricle 26.8.3.4. Median aperture into Cisterna Magna 26.8.3.5. Out to spinal cord 26.8.4. Understand the formation of the blood-brain barrier 26.8.4.1. Formed by a tight network of specialized endothelial cells lining brain capillaries, which are tightly connected by tight junctions, and are further supported by a basement membrane, pericytes embedded within the membrane, and astrocyte "perivascular feet" that closely envelop the capillaries, collectively creating a barrier that selectively controls what substances can pass from the bloodstream into the brain tissue 27BrainI 27. Describe the major regions of the brain 27.1. Regions 27.1.1. Cerebrum: The largest part of the brain, divided into two hemispheres (left and right), responsible for complex functions like thinking, learning, memory, language, and emotion. 27.1.2. Cerebellum: Located at the back of the brain, primarily responsible for coordinating muscle movements, maintaining balance, and fine motor skills. 27.1.3. Brainstem: Connects the brain to the spinal cord, controlling vital functions like breathing, heart rate, digestion, and consciousness. 27.2. Define gyri, sulci, gray & white matter 27.2.1. Gyri - Hills 27.2.2. Sulci - Valleys 27.2.3. Gray matter - Unmyelinated axons, cell bodies, dendrites 27.2.4. White matter - Myelinated axons 27.3. List the lobes of the cerebrum and their functions 27.3.1. Frontal lobe: Located at the front of the brain, involved in decision-making, planning, personality, and motor function. 27.3.2. Parietal lobe: Situated behind the frontal lobe, responsible for processing sensory information like touch, pain, and body awareness. 27.3.3. Temporal lobe: Located on the sides of the brain, primarily involved in auditory processing, memory, and facial recognition. 27.3.4. Occipital lobe: Found at the back of the brain, dedicated to visual processing. 27.3.5. Central sulcus: A deep groove running vertically on the lateral surface of the brain, marks the boundary between the primary motor cortex (in the frontal lobe) and the primary somatosensory cortex (in the parietal lobe). 27.3.6. Lateral Sulcus (Sylvian Fissure): A prominent sulcus that separates the temporal lobe from the frontal and parietal lobes. 27.4. Describe the functional areas of the motor cortex 27.4.1. Precentral Gyrus (Primary Motor Cortex): This is the main area responsible for initiating voluntary movements by sending signals directly to the spinal cord to control muscle contractions; it is considered the "primary" motor cortex and is located within the precentral gyrus. 27.4.2. Somatic Motor Association Area (Premotor Cortex): Situated in front of the primary motor cortex, this region is involved in planning complex movements, coordinating muscle groups, and preparing the body for action based on sensory information. 27.4.3. Frontal Eye Field: This specific area within the frontal lobe controls voluntary eye movements, directing gaze to specific targets based on visual input. 27.4.4. Broca's Area: Located in the inferior frontal gyrus, primarily involved in producing speech by controlling the muscles involved in articulation. 27.5. Describe the functional areas of the sensory cortex 27.5.1. Postcentral Gyrus (Primary Somatosensory Cortex): Situated on the postcentral gyrus of the parietal lobe, this area receives and processes information related to touch, pressure, pain, temperature, and proprioception from the body surface, creating a "sensory homunculus" representation of the body based on the density of sensory receptors;. 27.5.2. Somatosensory Association Area: Located near the primary somatosensory cortex, this area integrates and interprets sensory information from the body, allowing for complex perception of touch and spatial awareness. 27.5.3. Primary Visual Cortex (Area 17): Found in the occipital lobe, this area is the primary processing center for visual information received from the retina, responsible for basic visual perception like shape and color. 27.5.4. Visual Association Area: Surrounding the primary visual cortex, this region further analyzes and interprets visual information, enabling recognition of objects and scenes. 27.5.5. Primary Gustatory Cortex: Primarily located in the anterior insula and frontal operculum, this area processes taste information from the tongue and mouth. 27.5.6. Primary Auditory Cortex (Heschl's Gyrus): Situated within the temporal lobe, specifically in the transverse temporal gyri (Heschl's gyrus), this area is responsible for initial processing of sound frequencies and basic auditory perception. 27.5.7. Auditory Association Area: Adjacent to the primary auditory cortex, this area integrates and interprets complex auditory information, allowing for sound recognition and language comprehension. 27.5.8. Primary Olfactory Cortex: Found in the inferior frontal lobe and piriform cortex, this region receives and processes olfactory information from the nose. 27.6. Understand the special language areas of the brain and how they work together 27.6.1. Broca's area (left frontal lobe): Primarily responsible for speech production, including forming words and grammar structures. 27.6.2. Wernicke's area (left temporal lobe): Primarily responsible for language comprehension, processing the meaning of spoken and written words. 27.6.3. Angular gyrus (parietal lobe): Connects different sensory modalities, allowing for integration of visual, auditory, and tactile information related to language. 27.6.4. Speaking a Heard Word 27.6.4.1. Primary auditory cortex 27.6.4.2. Wernicke's Area 27.6.4.3. Broca’s area 27.6.4.4. Primary motor cortex 27.6.5. Speaking a Written Word 27.6.5.1. Primary visual cortex 27.6.5.2. Wernicke's Area 27.6.5.3. Angular Gyrus 27.6.5.4. Broca’s area 27.6.5.5. Primary motor cortex 27.6.6. Left side of brain is literal interpretation of speech 27.6.7. Right side of brain is emotional context of speech 27.7. Describe the way different areas of the brain communicate - communicate through white matter tracts 27.7.1. Association fibers: 27.7.1.1. Connect different areas of the cerebral cortex within the same hemisphere. 27.7.1.2. Can be short (U-fibers) connecting adjacent gyri or long connecting distant brain regions. 27.7.1.3. Important for complex cognitive functions like language processing and spatial awareness. 27.7.1.4. Examples include: 27.7.1.4.1. Superior Longitudinal Fasciculus (connecting frontal, parietal, temporal, and occipital lobes) 27.7.1.4.2. Inferior Longitudinal Fasciculus (connecting temporal and occipital lobes) 27.7.1.4.3. Uncinate Fasciculus (connecting frontal and temporal lobes) 27.7.2. Commissural fibers: 27.7.2.1. Connect corresponding areas between the left and right hemispheres of the brain. 27.7.2.2. The largest commissural tract is the corpus callosum, crucial for interhemispheric communication. 27.7.2.3. Smaller commissural tracts include the anterior commissure and posterior commissure. 27.7.3. Projection fibers: 27.7.3.1. Connect the cerebral cortex to other parts of the central nervous system like the brainstem and spinal cord. 27.7.3.2. Can be either sensory (ascending) or motor (descending) depending on the direction of information flow. 27.8. Understand the concept of cerebral lateralization 27.8.1. The specialization of functions between the left and right hemispheres of the brain, where each side takes on distinct cognitive roles, allowing for more efficient processing of information 27.8.2. Left hemisphere: 27.8.2.1. Language comprehension and production 27.8.2.2. Logical reasoning 27.8.2.3. Mathematical calculations 27.8.2.4. Fine motor control of the right side of the body 27.8.3. Right hemisphere: 27.8.3.1. Facial recognition 27.8.3.2. Spatial awareness 27.8.3.3. Artistic and creative thinking 27.8.3.4. Emotional processing 28BrainII 28. Name the parts of the diencephalon and give their functions 28.1. Understand the role of the thalamus as a relay 28.1.1. Thalamus: Acts as a relay center, receiving sensory information from various parts of the body and sending it to the cerebral cortex for processing, also involved in regulating consciousness and sleep. All sensory pathways except olfactory. Made up of various nuclei that have different functions. 28.1.2. Hypothalamus: Manages vital bodily functions like body temperature, hunger, thirst, sleep-wake cycles, and hormone regulation by controlling the pituitary gland, essentially maintaining homeostasis. 28.1.3. Epithalamus: Includes the habenular nuclei and pineal body, primarily involved in circadian rhythm regulation through melatonin production by the pineal gland: 28.1.3.1. Habenular nuclei: Associated with the limbic system, potentially involved in emotional responses to smells 28.1.3.2. Pineal body: Secretes melatonin, a hormone crucial for regulating sleep-wake cycles 28.2. Describe the functions of the hypothalamus - regulates homeostasis 28.2.1. Control of autonomic nervous system - sympathetic & parasympathetic 28.2.2. Control of endocrine system 28.2.3. Regulation of body temperature 28.2.4. Emotional behavior 28.2.5. Water intake 28.2.6. Sleep-wake rhythms 28.3. Identify the basal ganglia and describe their functions - a group of deep brain structures primarily responsible for controlling voluntary movement by filtering unnecessary motor signals, essentially acting as a "gatekeeper" for movement initiation, and also play a role in cognitive functions like decision-making and reward processing 28.3.1. Lentiform nucleus: 28.3.1.1. Putamen: Primarily involved in motor control, learning, and reward processing, receiving inputs from the motor cortex and sending signals to the globus pallidus. 28.3.1.2. Globus pallidus: Further refines motor signals, with the internal globus pallidus (GPi) sending inhibitory projections to the thalamus to influence movement. 28.3.2. Caudate nucleus: A C-shaped structure involved in planning and initiation of movement, as well as cognitive functions like working memory and decision-making. 28.3.3. Internal capsule: A white matter tract that carries fibers connecting the cerebral cortex to other brain regions, including the basal ganglia, essentially serving as a communication pathway. 28.3.4. Claustrum: A thin layer of grey matter with complex connections to various cortical areas, potentially involved in integrating sensory information and contributing to consciousness. 28.3.5. 28.4. Understand the role of the limbic system and its individual parts - The limbic system is a network of brain structures primarily responsible for regulating emotions, behavior, motivation, and memory 28.4.1. Cingulate gyrus: Plays a central role in regulating emotions, pain perception, and decision-making, with its anterior portion particularly involved in processing positive emotions and the posterior in negative emotions. 28.4.2. Fornix: A white matter tract that acts as a crucial communication pathway connecting the hippocampus to other limbic structures, particularly important for memory consolidation. 28.4.3. Limbic cortex: The outermost layer of the limbic system, integrating sensory information with emotional responses and contributing to complex behaviors. 28.4.4. Mammillary body: Located in the hypothalamus, involved in memory retrieval, especially related to spatial navigation and recognition. 28.4.5. Hippocampus: Critical for forming new long-term memories, spatial navigation, and recalling past experiences. 28.4.6. Olfactory bulbs: Process olfactory information, which is tightly integrated with emotional memories due to the close connection with the limbic system. 28.4.7. Amygdala: Plays a key role in processing emotions, particularly fear and aggression, and associating emotional significance with memories. 28.4.8. Parahippocampal gyrus: Involved in spatial navigation and memory, closely connected to the hippocampus. 28.5. Describe the parts of the midbrain and their functions 28.5.1. Cerebral Peduncles: These large bundles of nerve fibers are the main pathway for motor signals descending from the cerebral cortex to the spinal cord, facilitating voluntary movement control. 28.5.2. Superior Colliculus: Located on the dorsal surface of the midbrain, this structure plays a crucial role in visual orientation reflexes, allowing rapid eye movements to focus on visual stimuli. 28.5.3. Inferior Colliculus: Primarily involved in auditory processing, receiving and integrating sound information before relaying it to the thalamus. 28.5.4. Superior Cerebellar Peduncle: A bundle of nerve fibers connecting the midbrain to the cerebellum, facilitating communication between the two structures and contributing to coordinated movement. 28.6. Describe the parts of the pons and medulla and their functions - contain various nuclei and tracts responsible for vital functions like breathing, heart rate, and sensory relay 28.6.1. Pons: 28.6.1.1. Middle cerebellar peduncle: A large bundle of fibers connecting the pons to the cerebellum, primarily responsible for transmitting motor signals from the cerebral cortex to the cerebellum. 28.6.1.2. Superior olivary nucleus: Located in the pons, involved in sound localization by processing auditory information from the ears. 28.6.1.3. Reticular formation: A diffuse network of neurons within the pons involved in arousal, consciousness, sleep-wake cycles, and various autonomic functions. 28.6.1.4. Facial nucleus: Controls muscles of facial expression. 28.6.1.5. Trigeminal nerve nuclei: Relay sensory information from the face, including pain and temperature. 28.6.2. Medulla Oblongata: 28.6.2.1. Pyramids: Bulging structures on the ventral surface of the medulla where the corticospinal tract (motor fibers) descend from the brain. 28.6.2.2. Pyramidal decussation: The point where a majority of the corticospinal tract fibers cross over to the contralateral side of the spinal cord. 28.6.2.3. Olive: A prominent bulge on the lateral surface of the medulla containing the inferior olivary nucleus. 28.6.2.4. Inferior olivary nucleus: Part of the olivo-cerebellar system, involved in motor coordination and learning. 28.6.2.5. Nucleus gracilis and nucleus cuneatus: Sensory nuclei that receive information from the dorsal column-medial lemniscus pathway, responsible for fine touch, proprioception, and vibration sense. 28.6.2.6. Cardiac center: Regulates heart rate. 28.6.2.7. Respiratory center: Controls breathing rhythm. 28.6.2.8. Medial lemniscus: A sensory pathway carrying information about fine touch, pressure, and proprioception from the body to the thalamus. 28.6.3. Fourth Ventricle: 28.6.3.1. Location: Situated between the pons and medulla, filled with cerebrospinal fluid. 28.6.3.2. Function: Acts as a fluid-filled chamber that cushions the brain and helps maintain intracranial pressure. 29BrainIII 29. Describe the general anatomy of the cerebellum, it’s component parts, and their functions 29.1. External Anatomy: 29.1.1. Anterior Lobe: The front part of the cerebellum, involved in regulating muscle tone and coordinating postural activities like gait. 29.1.2. Vermis: A narrow midline ridge connecting the cerebellar hemispheres, primarily responsible for axial muscle control and balance. 29.1.3. Posterior Lobe: The larger posterior section of the cerebellum, crucial for planning and coordinating fine, distal movements like hand movements. 29.1.4. Primary Fissure: A prominent groove separating the anterior and posterior lobes. 29.1.5. Folia: The numerous parallel folds on the surface of the cerebellar cortex, increasing the surface area for neural connections. 29.1.6. Middle Cerebellar Peduncle: A bundle of nerve fibers connecting the cerebellum to the pons, carrying information from the cerebral cortex to the cerebellum. 29.2. Sectional Anatomy: 29.2.1. Cerebellar Cortex: The outer layer of the cerebellum, composed of a tightly packed layer of gray matter with three distinct layers (molecular, Purkinje cell, and granular) responsible for processing sensory information and sending inhibitory signals to the deep cerebellar nuclei. 29.2.2. Arbor Vitae: The branching pattern of white matter within the cerebellum, providing pathways for information to reach the cerebellar cortex and deep nuclei. 29.2.3. Dentate Nucleus: The largest deep cerebellar nucleus, located within the white matter, which receives input from the Purkinje cells and sends output signals to the brainstem to modulate movement. 29.3. Understand how information travels to and from the cerebellum 29.3.1. Information travels to the cerebellum primarily through the corticopontocerebellar pathway, carrying motor commands from the cerebral cortex, and sensory information from the spinal cord via the spinocerebellar tracts, allowing the cerebellum to compare intended movements with actual movement and send corrective feedback via the dentato-rubro-thalamo-cortical pathway 29.3.2. 29.4. Describe the function of the reticular formation - processes sensory information, sends signals to cortex to bring about alertness 29.5. Understand the fundamental setup of ascending and descending pathways in the spinal cord 29.5.1. Sensory pathways ascend toward brain 29.5.2. Motor pathways descend from brain 29.5.3. 29.6. List the major sensory pathways and their functions 29.6.1. Dorsal Column-Medial Lemniscus Pathway: Carries information about fine touch, vibration, and proprioception; 29.6.1.1. Primary Neuron: Located in the dorsal root ganglion (DRG), with peripheral endings in the skin and proprioceptors; 29.6.1.2. Secondary Neuron: Cell body in the medulla oblongata (gracile and cuneate nuclei), axons cross the midline to form the medial lemniscus; 29.6.1.3. Tertiary Neuron: Cell body in the ventral posterolateral nucleus of the thalamus, axons project to the primary sensory cortex. 29.6.2. Spinothalamic Pathway (Anterolateral Pathway): Carries information about pain and temperature; 29.6.3. Spinocerebellar Pathway: Carries proprioceptive information from muscles and joints to the cerebellum for coordination; 29.6.4. Key Points: 29.6.4.1. Primary Sensory Cortex: Located in the postcentral gyrus of the parietal lobe, receives sensory information from the thalamus. 29.6.4.2. Cell Body in DRG: The cell body of the primary sensory neuron in most sensory pathways is located in the dorsal root ganglion. 29.6.4.3. Peripheral Ending: The sensory receptor located in the periphery that detects stimuli (e.g., touch, pain, temperature). 29.7. List the major motor pathways and their functions 29.7.1. Primary Motor Cortex: The origin of voluntary movement signals, sending information down through the corticospinal tract to control muscle movement throughout the body. 29.7.2. Upper Motor Neuron (UMN): A neuron with its cell body in the cerebral cortex that carries motor commands down the spinal cord to activate lower motor neurons, responsible for initiating voluntary movement. 29.7.3. Lower Motor Neuron (LMN): A neuron located in the ventral horn of the spinal cord that directly innervates muscle fibers, responsible for muscle contraction. 29.7.4. Cell Body in Ventral Horn: The location within the spinal cord where the cell bodies of lower motor neurons reside. 29.7.5. Peripheral Ending: The axon terminal of a lower motor neuron that connects to a muscle fiber, triggering muscle contraction. 29.7.6. Major Motor Pathways: 29.7.6.1. Lateral Corticospinal Tract: The primary pathway for voluntary movement of the limbs, particularly fine motor control of the hands and feet; originates in the primary motor cortex and crosses over in the medulla oblongata. 29.7.6.2. Rubrospinal Tract: Primarily involved in flexor muscle control, particularly in the upper limbs, originating from the red nucleus in the brainstem. 29.7.6.3. Ventromedial System (including Anterior Corticospinal Tract): Controls axial muscles and posture, maintaining balance and stability of the trunk. 29.7.6.4.Anterior Corticospinal Tract: A part of the ventromedial system, responsible for voluntary control of axial muscles. 29.7.6.5. Reticulospinal Tract: Contributes to muscle tone and posture regulation, originating from the reticular formation in the brainstem. 29.7.6.6. Vestibulospinal Tract: Primarily responsible for maintaining balance and posture, originating from the vestibular nuclei in the brainstem. 29.7.6.7. Tectospinal Tract: Involved in eye movement coordination and head turning, originating from the superior colliculus. 29.7.7. Key points to remember: 29.7.7.1. The corticospinal tract is considered the primary pathway for voluntary movement. 29.7.7.2. Damage to upper motor neurons typically results in spasticity and hyperreflexia, while lower motor neuron damage leads to muscle weakness and atrophy. 29.7.7.3. The different motor pathways work together to coordinate complex movements. 30CNI-II 30. Olfaction (CN1: Olfactory Nerve) 30.1. Describe the gross anatomy of the olfactory nerve 30.1.1. Olfactory epithelium: The lining of the nasal cavity where olfactory receptor cells are located, detecting odor molecules. 30.1.2. Olfactory nerve fibers: The axons of the olfactory receptor cells that extend from the olfactory epithelium, forming bundles that pass through the cribriform plate. 30.1.3. Cribriform plate: A part of the ethmoid bone with numerous small holes through which the olfactory nerve fibers pass to reach the cranial cavity. 30.1.4. Olfactory bulb: A bulb-shaped structure located just above the cribriform plate where the olfactory nerve fibers terminate and synapse with mitral cells (second-order neurons) within glomeruli. 30.1.5. Olfactory tract: A bundle of axons from the mitral cells in the olfactory bulb that carries olfactory information to the brain. 30.1.6. Important points to remember: 30.1.6.1. The olfactory nerve is considered a special sensory nerve, meaning it carries sensory information related to a specific sense (smell). 30.1.6.2. The olfactory bulb is a crucial processing center for olfactory information before it is transmitted to the brain. 30.1.6.3. Damage to the cribriform plate or olfactory bulb can lead to impaired sense of smell (anosmia). 30.2. Describe the components of the olfactory epithelium 30.2.1. Olfactory receptor cells: The primary sensory neurons of the olfactory epithelium, with hair-like projections called olfactory hairs (cilia) that extend into the mucous layer to detect odor molecules. 30.2.2. Supporting cells: Cells surrounding the olfactory receptor cells, providing structural support and secreting mucus. 30.2.3. Basal cells: Stem cells located in the basal layer of the epithelium that continuously regenerate new olfactory receptor cells. 30.2.4. Olfactory glands (Bowman's glands): Exocrine glands within the lamina propria that secrete mucus to trap odor molecules. 30.2.5. Cribriform plate: A perforated bone structure in the roof of the nasal cavity through which the olfactory nerve fibers pass to reach the olfactory bulb. 30.2.6. Lamina propria: The connective tissue layer underlying the olfactory epithelium, containing blood vessels and olfactory glands. 30.2.7. Mucous layer: A layer of mucus covering the olfactory epithelium, where odor molecules dissolve before interacting with olfactory receptors. 30.2.8. Olfactory bulb: A bulge in the brain where the olfactory nerves synapse with mitral cells and other neurons. 30.2.9. Olfactory glomerulus: A spherical structure within the olfactory bulb where the axons of olfactory receptor cells make synaptic connections with the dendrites of mitral cells. 30.2.10. Mitral cells: Principal neurons within the olfactory bulb that receive signals from olfactory receptor cells via the glomeruli. 30.3. Understand the olfactory pathways through the brain 30.3.1. Olfactory receptors in the nose: Odor molecules bind to specialized receptor cells in the olfactory epithelium. 30.3.2. Olfactory nerve (cranial nerve I): Signals are transmitted via the olfactory nerve fibers through the cribriform plate to the olfactory bulb. 30.3.3. Olfactory bulb: Within the olfactory bulb, the information is processed and relayed by mitral cells. 30.3.4. Olfactory tract: Axons from mitral cells form the olfactory tract, projecting to the primary olfactory cortex. 30.3.5. Piriform cortex: The primary olfactory cortex (mainly the piriform cortex) receives the olfactory information and performs initial odor processing. 30.3.6. Amygdala projection: Neurons from the piriform cortex send projections to the amygdala, enabling emotional associations with smells. 30.3.7. Hypothalamic projection: Further projections from the piriform cortex reach the hypothalamus, influencing behaviors like feeding and drinking based on smell. 30.3.8. Important considerations: 30.3.8.1. Unique pathway: Unlike most other sensory systems, the olfactory pathway bypasses the thalamus before reaching the cortex. 30.3.8.2. Emotional processing: The direct connection to the amygdala explains why smells can trigger strong emotional responses and memories. 30.3.8.3. Integration with other senses: Olfactory information can be integrated with other sensory modalities, like taste, in higher cortical areas. 30.4. Vision (CN II: Optic Nerve) 30.5. Describe the anatomy of the structures associated with the eye 30.5.1. External Eye Anatomy: 30.5.1.1. Eyelid (Palpebra): A movable fold of skin that protects the eye, with the upper and lower eyelids meeting at the medial and lateral palpebral commissures (inner and outer corners). 30.5.1.2. Tarsal Plate: A dense fibrous tissue within each eyelid that provides structural support. 30.5.1.3. Conjunctiva: A thin mucous membrane lining the inside of the eyelids and covering the visible part of the sclera, providing lubrication. 30.5.1.4. Lacrimal Gland: Located in the superior lateral aspect of the orbit, responsible for producing tears. 30.5.1.5. Lacrimal Caruncle: A small fleshy bump located at the medial canthus (inner corner) of the eye, containing modified sweat glands. 30.5.1.6. Lacrimal Puncta: Tiny openings on the medial aspect of each eyelid margin where tears enter the lacrimal drainage system. 30.5.1.7. Lacrimal Canaliculi: Small ducts connecting the lacrimal puncta to the lacrimal sac. 30.5.1.8. Lacrimal Sac: A small pouch located in the bony lacrimal fossa, collecting tears from the canaliculi. 30.5.1.9. Nasolacrimal Duct: A tube that carries tears from the lacrimal sac into the nasal cavity. 30.6. Describe the internal structure of the eye and the retina 30.6.1. Fibrous Layer: The outermost layer of the eye, composed of the transparent cornea (anterior) and the white sclera (posterior). 30.6.2. Cornea: The clear, dome-shaped front part of the eye that allows light to enter. 30.6.3. Sclera: The tough, protective white outer layer of the eyeball. 30.6.4. Vascular Layer (Uvea): The middle layer of the eye, consisting of the choroid, ciliary body, and iris. 30.6.5. Choroid: A pigmented layer behind the retina, providing blood supply and absorbing excess light. 30.6.6. Ciliary Body: A muscular structure attached to the lens, responsible for accommodation (focusing). 30.6.7. Iris: The colored part of the eye, containing muscles that control the size of the pupil. 30.6.8. Pupil: The opening in the center of the iris, allowing light to enter the eye. 30.6.9. Inner Layer (Retina): The light-sensitive inner layer of the eye, containing photoreceptor cells (rods and cones) that convert light into electrical signals. 30.6.10. Lens: A transparent, biconvex structure behind the pupil, focusing light onto the retina. 30.6.11. Aqueous Humor: A clear fluid filling the anterior chamber of the eye, between the cornea and the iris. 30.6.12. Vitreous Humor: A gel-like substance that fills the posterior chamber of the eye, supporting the retina. 30.7. List the types of photoreceptors and their arrangement 30.7.1. Function: Rods are highly sensitive to light, allowing for vision in dim conditions, while cones are less sensitive but provide detailed color information. 30.7.2. Distribution on the retina: Rods are mainly located in the peripheral retina, while cones are densely packed in the central fovea. 30.8. Understand visual fields and the pathway of visual information 30.8.1. Retina: Light enters the eye and is focused onto the retina, where photoreceptor cells (rods and cones) convert light into electrical signals. 30.8.2. Optic Nerve: The electrical signals from the retina are transmitted through the optic nerve, which leaves the eye at the optic disc. 30.8.3. Optic Chiasm: At the optic chiasm, a partial crossover occurs where fibers carrying information from the nasal (inner) half of each retina cross over to the opposite side of the brain, while fibers from the temporal (outer) half remain ipsilateral. 30.8.4. Lateral Geniculate Nucleus (LGN): After the optic chiasm, the optic tracts carry visual information to the LGN in the thalamus, where further processing takes place. 30.8.5. Optic Radiations: From the LGN, visual information travels through the optic radiations to reach the primary visual cortex (V1) located in the occipital lobe. 30.8.6. Important aspects of visual fields: 30.8.6.1. Binocular vision: Both eyes contribute to the overall visual field, with overlapping areas creating depth perception. 30.8.6.2. Visual field quadrants: The visual field is divided into four quadrants (superior right, superior left, inferior right, inferior left). 30.8.6.3. Blind spot: The area where the optic nerve leaves the retina lacks photoreceptors, creating a small blind spot in the visual field. 30.8.7. How visual information is processed in the brain: 30.8.7.1. Primary Visual Cortex (V1): This area performs basic visual processing, including detecting edges, orientation, and color. 30.8.7.2. Visual association areas: After V1, visual information is further processed in specialized areas of the brain depending on the type of information (e.g., motion detection, object recognition, facial recognition). 30.8.8. Potential impacts on visual fields and pathways: 30.8.8.1. Brain lesions: Damage to specific parts of the visual pathway can result in visual field defects, such as hemianopsia (loss of vision in one half of the visual field). 30.8.8.2. Eye diseases: Retinal diseases or optic nerve damage can also lead to visual field impairments. 30.9. 30.10. 31CNIII-IV-VI 31. Describe the gross anatomy of the nerves serving the extraocular muscles 31.1. Oculomotor nerve (CN III): This nerve innervates four of the six extraocular muscles: the superior rectus, inferior rectus, medial rectus, and inferior oblique. It also controls the levator palpebrae superioris muscle, which raises the upper eyelid.2 The oculomotor nerve exits the brainstem at the level of the midbrain and travels through the cavernous sinus before entering the orbit through the superior orbital fissure. 31.1.1. 31.2. Trochlear nerve (CN IV): This nerve innervates the superior oblique muscle, which is responsible for downward and outward eye movement. It is the only cranial nerve that exits the brainstem dorsally. The trochlear nerve also travels through the cavernous sinus and enters the orbit through the superior orbital fissure. 31.3. Abducens nerve (CN VI): This nerve innervates the lateral rectus muscle, which is responsible for outward eye movement. The abducens nerve exits the brainstem at the level of the pons and travels through the cavernous sinus before entering the orbit through the superior orbital fissure. 31.3.1. 31.4. Identify the location and arrangement of the extraocular muscles 31.4.1. Superior Rectus: Located at the top of the eye, responsible for upward eye movement. 31.4.2. Medial Rectus: Situated on the medial side of the eye, moving the eye inwards towards the nose. 31.4.3. Lateral Rectus: Found on the lateral side of the eye, responsible for outward eye movement. 31.4.4. Inferior Rectus: Positioned at the bottom of the eye, controlling downward eye movement. 31.4.5. Superior Oblique: Originates in the upper medial part of the orbit, with a unique tendon that runs through a pulley before attaching to the eye, allowing for downward and outward eye movement. 31.4.6. Inferior Oblique: Located on the floor of the orbit near the nose, primarily responsible for upward and outward eye movement. 31.4.7. Levator Palpebrae Superioris: Not directly involved in eye movement, but situated above the superior rectus muscle and is dedicated to raising the upper eyelid. 31.5. Understand how the extraocular muscles work together to move the pupil 31.5.1. Muscles area “yolked” or coupled” 31.5.2. 31.5.3. 31.5.4. 31.5.5. 31.6. Understand intorsion and extorsion and why they are necessary 31.6.1. 31.6.2. Why are they necessary? 31.6.2.1. Maintaining Focus: As the eye moves, especially during oblique gaze (looking up and inward or down and outward), intorsion and extorsion help keep the visual axis aligned with the target. This ensures that the image falls directly onto the fovea, the part of the retina responsible for sharp, detailed vision. 31.6.2.2. Binocular Vision: These rotational movements are essential for maintaining binocular vision, where both eyes work together to produce a single, unified image. By coordinating these movements, the brain ensures that both eyes are focused on the same point in space. 31.6.2.3. Compensating for Head Tilt: When we tilt our head, our eyes need to adjust to compensate. Intorsion and extorsion help maintain visual stability by counteracting the effects of head tilt. 31.7. Describe the parasympathetic innervation of the eye 31.7.1. Parasympathetic innervation of the eye primarily controls the ciliary muscle and the iris sphincter muscle, leading to lens accommodation (by contracting the ciliary muscle) and pupil constriction (by contracting the iris sphincter), allowing the eye to focus on near objects by changing the shape of the lens and regulating the amount of light entering the eye; this pathway is carried by the oculomotor nerve (cranial nerve III) via the ciliary ganglion to reach the eye muscles involved. 31.7.2. 31.8. Understand the consequences of lesions to CN III, IV, & VI - remember to give side too! 31.8.1. CN III (Oculomotor nerve) 31.8.1.1. Upper lip ptosis 31.8.1.2. Extroic globe (“down and ou”) 31.8.1.3. Diplopia & strabismus (horizontal & vertical double vision) 31.8.1.4. Mydriasis (dilated pupil) 31.8.1.5. Lack of accommodation 31.8.1.6. 31.8.2. CN IV (Trochlear nerve) 31.8.2.1. Extorted eye made worse when head position requires intorsion for level vision 31.8.2.2. Head tilt to unaffected side (point chin to lesion) 31.8.2.3. 31.8.3. CN VI (Abducens nerve) 31.8.3.1. Diplopia 31.8.3.2. Face turns to side of lesion to restore binocular vision 31.8.3.3. 32CNV 32. Describe the overall gross anatomy of the trigeminal nerve 32.1. Describe the anatomy and functions of the ophthalmic, maxillary, and mandibular divisions 32.1.1. V1: Ophthalmic Division 32.1.1.1. Branches: Frontal nerve, lacrimal nerve, nasociliary nerve (which further divides into the supraorbital nerve, infratrochlear nerve, and long ciliary nerves) 32.1.1.2. Sensory distribution: Skin of the forehead, scalp, upper eyelid, eyebrow, frontal sinus, cornea, conjunctiva, and dural sinuses of the anterior cranial fossa. 32.1.1.3. 32.1.2. V2: Maxillary Division 32.1.2.1. Branches: Zygomatic nerve, infraorbital nerve (which divides into the superior labial nerves), pterygopalatine ganglion (giving rise to the nasopalatine nerve, greater palatine nerves, and lesser palatine nerves), superior alveolar nerves 32.1.2.2. Sensory distribution: Skin of the cheeks, upper lip, maxillary sinus, lateral nose, upper teeth, palate, and nasal mucosa 32.1.2.3. 32.1.3. V3: Mandibular Division 32.1.3.1. Branches: Auriculotemporal nerve, lingual nerve, buccal nerve, inferior alveolar nerve (which terminates as the mental nerve) 32.1.3.2. Sensory distribution: Skin of the chin, lower lip, external ear, lower teeth, oral mucosa of the lower lip and floor of the mouth, temporomandibular joint 32.1.3.3. 32.2. Describe the structure of the temporomandibular joint 32.2.1. Mandibular Fossa: This is a depression on the temporal bone which forms the socket for the head of the mandible, including the articular eminence (a raised anterior border) that guides jaw movement. 32.2.2. Articular Disc: A biconcave, fibrous cartilage disc that acts as a shock absorber, separating the mandibular fossa from the mandibular condyle and dividing the joint space into two compartments. 32.2.3. Joint Capsule: A fibrous connective tissue sheath that surrounds the TMJ, attaching to the margins of the mandibular fossa, the articular eminence, and the neck of the mandibular condyle, providing stability to the joint. 32.2.4. Head of the Mandible (Condylar Process): The rounded, articulating surface on the mandible that fits into the mandibular fossa, allowing for sliding and rotational movements. 32.3. List the muscles of mastication and their actions 32.3.1. Jaw Closers: 32.3.1.1. Temporalis: Elevates and retracts the mandible (jaw closure), contributes to grinding movements by side-to-side action. 32.3.1.2. Masseter: Elevates the mandible (jaw closure), strong force for biting. 32.3.1.3. Medial Pterygoid: Elevates and protrude the mandible (jaw closure), assists in side-to-side movement. 32.3.2. Jaw Opener: 32.3.2.1. Digastric Muscle: Depresses the mandible (jaw opening). 32.3.3. Lateral Excursion (Side-to-Side Movement): 32.3.3.1. Lateral Pterygoid: When contracting unilaterally, causes lateral excursion of the mandible to the opposite side. 32.3.4. Key Points: 32.3.4.1. All muscles of mastication are innervated by the mandibular nerve (V3) of the trigeminal nerve. 32.3.4.2. The temporalis and masseter are considered the primary jaw closers, while the lateral pterygoid is the primary jaw opener 32.4. Understand the function of the auditory muscles and their relationship to mastication 32.4.1. Tensor tympani: When contracted, this muscle pulls on the malleus bone in the middle ear, tightening the tympanic membrane and reducing its vibration in response to loud sounds like chewing or sudden noises. 32.4.2. Tensor veli palatini: This muscle primarily functions to open the Eustachian tube, which equalizes air pressure in the middle ear, often triggered by swallowing or jaw movements that occur during chewing. 32.4.3. Key points about their relationship to mastication: 32.4.3.1. Reflexive action: Both muscles are part of the middle ear reflex, meaning they contract involuntarily in response to loud sounds, including those produced during chewing. 32.4.3.2. Neural connection: The shared innervation by the trigeminal nerve allows for coordinated activity between the muscles of mastication and the auditory muscles, ensuring proper sound dampening during chewing. 32.4.3.3. Protection from damage: By adjusting the tension of the tympanic membrane, these muscles help prevent damage to the delicate hair cells in the inner ear from excessive sound vibrations caused by chewing. 32.5. Understand the role of the trigeminal nerve in carrying axons for other nerves 32.5.1. Sensory function: Primarily, the trigeminal nerve is responsible for carrying sensory information from the face, including touch, pain, and temperature sensations. 32.5.2. Parasympathetic involvement: While not its primary function, the trigeminal nerve also carries parasympathetic fibers to certain glands in the head and neck region. 32.5.3. Lacrimal gland innervation: The ophthalmic division of the trigeminal nerve carries parasympathetic fibers to the lacrimal gland, stimulating tear production. 32.5.4. Salivary gland innervation: The mandibular division of the trigeminal nerve carries parasympathetic fibers to the submandibular and sublingual glands, contributing to saliva secretion. 32.5.5. Pathway: The parasympathetic fibers traveling with the trigeminal nerve typically originate from the pterygopalatine ganglion, then travel along the nerve branches to reach their target glands. 32.5.6. 33CNVII 33. Describe the gross anatomy and parts of the facial nerve 33.1.1. Geniculate ganglion: A sensory ganglion located within the facial canal, where the greater petrosal nerve originates. 33.1.2. Greater petrosal nerve: A branch of the facial nerve carrying parasympathetic fibers to the pterygopalatine ganglion, which then innervates the lacrimal gland and mucous glands of the nasal cavity and palate. 33.1.3. Chorda tympani: Another branch of the facial nerve that passes through the middle ear and joins the lingual nerve (a branch of the mandibular nerve) to convey taste sensation from the anterior two-thirds of the tongue; it also carries parasympathetic fibers to the submandibular and sublingual glands. 33.1.4. Pterygopalatine ganglion: A parasympathetic ganglion where the greater petrosal nerve synapses, providing postganglionic fibers to the lacrimal gland and mucous glands of the nasal cavity and palate. 33.1.5. Submandibular ganglion: A parasympathetic ganglion where the chorda tympani synapses, innervating the submandibular and sublingual salivary glands. 33.1.6. 33.2. Describe the actions of the different muscles of facial expression 33.2.1. Muscles of the Forehead and Eyebrow 33.2.2. Galea aponeurotica (Epicranial aponeurosis): A tough, tendinous sheet that connects the frontalis and occipitalis muscles. It allows for movement of the scalp. 33.2.3. Frontalis: Raises the eyebrows, creating a surprised or worried expression. 33.2.4. 33.2.5. Occipitalis: Pulls the scalp posteriorly. 33.2.6. Epicranius (Occipitofrontalis): Together, the frontalis and occipitalis form the epicranius. They work together to raise the eyebrows and wrinkle the forehead. 33.2.6.1. 33.2.7. Procerus: Lowers the medial aspect of the eyebrow, creating a frown. 33.2.8. Orbicularis oculi: 33.2.8.1. Orbital part: Closes the eyelids forcefully. 33.2.8.2. Palpebral part: Gently closes the eyelids. 33.2.8.2.1. 33.2.8.3. Medial palpebral ligament: Supports the eyelids and helps to maintain their shape 33.2.8.4. Muscles of the Nose 33.2.8.4.1. Nasalis: 33.2.8.4.1.1. Alar part: Flares the nostrils. 33.2.8.4.1.2. Transverse part: Compresses the bridge of the nose. 33.2.8.4.1.3. 33.2.9. Muscles of the Mouth 33.2.9.1. Orbicularis oris: Closes the lips. 33.2.9.1.1. 33.2.9.2. Zygomaticus major: Elevates the corner of the mouth, producing a smile. 33.2.9.2.1. 33.2.9.3. Zygomaticus minor: Elevates the upper lip. 33.2.9.3.1. 33.2.9.4. Levator anguli oris: Elevates the corner of the mouth. 33.2.9.4.1. 33.2.9.5. Levator labii superioris: Elevates the upper lip. 33.2.9.5.1. 33.2.9.6. Depressor anguli oris: Depresses the corner of the mouth, creating a frown. 33.2.9.6.1. 33.2.9.7. Depressor labii inferioris: Depresses the lower lip. 33.2.9.7.1. 33.2.9.8. Mentalis: Elevates and protrudes the lower lip. 33.2.9.8.1. 33.2.9.9. Pterygomandibular Raphe: A tendinous raphe that provides attachment for various muscles. 33.2.9.10. Buccinator: Compresses the cheeks and helps to keep food between the teeth during chewing. 33.2.9.10.1. 33.2.9.11. Platysma: Tenses the skin of the neck and depresses the angle of the mouth. 33.2.9.11.1. 33.2.10. 33.3. Understand the overall mechanism of gustation 33.3.1. Gustation, or the sense of taste, is a complex process that involves the interaction of chemical substances with specialized receptors on the tongue. 33.3.2. Chemoreception: This is the detection of chemical stimuli by sensory cells. In the case of taste, the chemical stimuli are called tastants. 33.3.3. Tastants: These are substances that dissolve in saliva and interact with taste receptors. They can be simple molecules like sodium chloride (salty) or complex compounds found in foods. 33.3.4. Taste Buds: These are sensory organs located primarily on the tongue's surface, within structures called papillae. They contain taste receptor cells, which are responsible for detecting taste. 33.3.5. Gustatory Cells: These specialized cells within taste buds have microvilli that extend into taste pores. When tastants dissolve in saliva and enter the taste pores, they bind to receptors on the microvilli. 33.3.6. Binding of Tastants: Different types of tastants bind to specific receptors on the gustatory cells. For example, sweet, bitter, and umami tastes are detected by G protein-coupled receptors, while salty and sour tastes are detected by ion channels. 33.3.7. Signal Generation: When a tastant binds to its receptor, it triggers a series of biochemical reactions within the gustatory cell. This leads to the generation of electrical signals, which are transmitted to the brain. 33.3.8. Neural Transmission: The electrical signals are carried by cranial nerves to the brain stem, where they are processed and interpreted. 33.3.9. Brain Processing: The signals from the taste buds are sent to the thalamus, a relay station in the brain, and then to the gustatory cortex, located in the temporal lobe. 33.3.10. Taste Perception: The gustatory cortex processes the information and generates the perception of taste. This perception is influenced by factors such as the concentration of the tastant, temperature, and the presence of other sensory stimuli, such as smell. 33.4. Describe the gross anatomy of the tongue 33.4.1. Body: The anterior two-thirds of the tongue, visible in the oral cavity. 33.4.2. Root: The posterior one-third, attached to the hyoid bone and pharyngeal wall. 33.4.3. A terminal sulcus separates the body and root. The dorsal surface of the tongue is covered with various types of papillae: 33.4.3.1. Filiform papillae: Small, thread-like structures covering most of the tongue's surface, responsible for texture sensation. 33.4.3.2. Fungiform papillae: Mushroom-shaped papillae scattered among the filiform papillae, containing taste buds. 33.4.3.3. Circumvallate papillae: Large, circular papillae arranged in a V-shape near the base of the tongue, also containing taste buds. 33.4.4. Facial Nerve (CN VII): 33.4.4.1. Chorda tympani branch: Innervates the anterior two-thirds of the tongue, providing taste sensation (sweet, salty, sour) and general sensation (touch, pressure, pain). 33.4.5. Glossopharyngeal Nerve (CN IX): 33.4.5.1.Innervates the posterior one-third of the tongue, providing taste sensation (bitter) and general sensation. 33.4.6. Vagus Nerve (CN X): 33.4.6.1. Provides general sensation to the root of the tongue and epiglottis. 33.5. List the types of papillae and their functions 33.5.1. Circumvallate papillae 33.5.1.1. 70% of taste buds 33.5.1.2. Anterior to terminal sulcus 33.5.2. Filiform papillae 33.5.2.1. Most numerous 33.5.2.2. Lacks taste buds 33.5.2.3. Mechanical role 33.5.3. Fungiform papillae 33.5.3.1. 30% of taste buds 33.5.3.2. Anterior ⅔ of tongue 33.5.4. Foliate papillae 33.5.4.1. Poorly developed 33.5.4.2. Few taste buds 33.5.5. 33.6. Understand the information taste conveys - Entire tongue is sensitive to all tastes 33.6.1. Sweet -> energy rich 33.6.2. Umami/Savory -> amino acids 33.6.3. Salty -> dietary electrolytes 33.6.4. Bitter -> Noxious/poisonous 33.6.5. Sour -> Noxious/poisonous 33.6.6. Fat -> ? 33.7. Understand gustatory pathways in the brain 33.7.1. Facial N./Glossopharyngeal N. → Medulla → Thalamus → Insula (primary gustatory cortex) 33.7.2. 33.8. Lesions 33.8.1. 34CNVIII 34. Describe the gross anatomy of the auditory system 34.1. Cochlea 34.1.1. Cochlea: A spiral-shaped bony structure in the inner ear responsible for hearing. 34.1.2. Cochlear Nerve: Part of CN VIII, it transmits auditory information from the cochlea to the brain. 34.1.3. Scala Vestibuli: Uppermost chamber of the cochlea filled with perilymph. 34.1.4. Scala Tympani: Lowermost chamber of the cochlea filled with perilymph. 34.1.5. Cochlear Duct (Scala Media): Middle chamber of the cochlea filled with endolymph, containing the Organ of Corti. 34.1.6. Tectorial Membrane: A gelatinous membrane in the cochlear duct that overlays hair cells. 34.1.7. Vestibular Membrane (Reissner's Membrane): Separates the scala vestibuli from the cochlear duct. 34.1.8. Basilar Membrane: A flexible membrane in the cochlear duct that supports the Organ of Corti and vibrates in response to sound waves. 34.1.9. Hair Cell: Sensory receptor cells in the Organ of Corti that convert sound vibrations into electrical signals. 34.2. Auditory Ossicles 34.2.1. Malleus (Hammer): The first and largest of the three ossicles, attached to the tympanic membrane. 34.2.2. Incus (Anvil): The middle ossicle, connecting the malleus to the stapes. 34.2.3. Stapes (Stirrup): The smallest ossicle, its footplate fits into the oval window. 34.2.4. Stapedal Footplate: The base of the stapes that transmits vibrations to the fluid in the cochlea. 34.2.5. Oval Window: An opening in the cochlea that receives vibrations from the stapes. 34.3. Auditory Anatomy 34.3.1. CN VIII (Vestibulocochlear Nerve): A cranial nerve responsible for hearing and balance. 34.3.2. Cochlear Branch: Part of CN VIII that transmits auditory information. 34.3.3. Vestibular Branch: Part of CN VIII that transmits information about balance and spatial orientation. 34.3.4. Auricle (Pinna): The visible part of the ear that collects sound waves. 34.3.5. External Acoustic Meatus (Ear Canal): A tube that conducts sound waves to the tympanic membrane. 34.3.6. Tympanum (Tympanic Membrane): The eardrum, a thin membrane that vibrates in response to sound waves. 34.3.7. Eustachian Tube: Connects the middle ear to the nasopharynx, equalizing pressure. 34.4. Understand how the ossicles and cochlea transmit sound 34.4.1. Sound waves vibrate tympanic membrane 34.4.2. Waves transmitted through auditory ossicles 34.4.3. Ossicles transmit vibrations to oval window 34.4.4. Vibrations cause pressure waves in perilymph 34.4.5. Pressure waves travel via scala vestibuli to apex of cochlea, “sensed” by cochlear nerve 34.4.6. Pressure waves in perilymph transferred to scala tympani 34.4.7. Pressure waves dissipated through round window into tympanic cavity 34.4.8. 34.5. Describe the mechanism of auditory hair cells 34.5.1. Basilar membrane pushes hair cells into tectorial membrane 34.5.2. Stereocilia tips are moved, tips links pull open ion channels 34.5.3. Hair cell releases NT from its base, exciting sensory neuron 34.5.4. 34.6. Understand auditory pathways in the brain 34.6.1. Cochlear N. → Cochlear nuclei → Superior olivary nucleus → Inferior colliculus → Thalamus → Primary auditory cortex (temporal lobe) 34.6.2. 34.7. Describe the basic anatomy and function of the vestibular system 34.7.1. The vestibular system is a critical component of the inner ear responsible for maintaining balance and spatial orientation. It consists of two primary components: 34.7.2. Semicircular Canals 34.7.2.1. Function: Detect rotational movements of the head. 34.7.2.2. Anatomy: There are three semicircular canals: 34.7.2.2.1. Superior: Detects head movements in the sagittal plane (nodding "yes"). 34.7.2.2.2. Posterior: Detects head movements in the coronal plane (tilting head side-to-side). 34.7.2.2.3. Horizontal: Detects head rotations in the transverse plane (shaking head "no"). 34.7.3. Ampullae: Enlarged chambers at the base of each semicircular canal. 34.7.4. Hair Cells: Sensory receptors within the ampullae that detect movement of fluid (endolymph) within the canals. 34.7.5. Kinocilium: A single, large hair-like projection. 34.7.6. Stereocilia: Multiple, smaller hair-like projections. 34.7.7. Otolith Organs 34.7.7.1. Function: Detect linear acceleration and gravity. 34.7.7.2. Anatomy: There are two otolith organs: 34.7.7.2.1. Utricle: Detects horizontal linear acceleration (forward/backward, side-to-side). 34.7.7.2.2. Saccule: Detects vertical linear acceleration (up/down). 34.7.7.3. Maculae: Sensory structures within the utricle and saccule. 34.7.7.4. Hair Cells: Sensory receptors within the maculae that detect movement of otoliths. 34.7.7.4.1. Kinocilium: A single, large hair-like projection. 34.7.7.4.2. Stereocilia: Multiple, smaller hair-like projections. 34.7.7.5. Otoliths: Tiny calcium carbonate crystals that move in response to gravity and linear acceleration, bending the hair cells. 34.7.8. When the head moves, fluid within the semicircular canals or otolith organs shifts, bending the hair cells. This bending triggers nerve impulses that are transmitted to the brain via the vestibular nerve (part of the vestibulocochlear nerve, CN VIII). The brain processes this information and coordinates responses to maintain balance, posture, and eye movements. 34.8. List the components of the vestibular system and describe how they detect head movements 34.8.1. The vestibular system, located in the inner ear, is responsible for detecting head movements and maintaining balance. It comprises two main components: 34.8.2. Semicircular Canals: 34.8.2.1. Function: Detect rotational head movements. 34.8.2.2. Anatomy: There are three semicircular canals oriented in different planes: 34.8.2.3. Superior canal: Detects head nodding (up and down). 34.8.2.4. Posterior canal: Detects head tilting (side to side). 34.8.2.5. Horizontal canal: Detects head shaking (left to right). 34.8.2.6. Detection Mechanism: Each canal contains a fluid called endolymph. When the head rotates, the endolymph fluid lags behind due to inertia, causing it to flow and deflect a structure called the cupula. The cupula houses hair cells, which are sensory receptors with tiny hair-like projections called stereocilia. The movement of the cupula bends the stereocilia, triggering nerve impulses that are sent to the brain. 34.8.3. Otolith Organs: 34.8.3.1. Function: Detect linear acceleration and gravity. 34.8.3.2. Anatomy: There are two otolith organs: 34.8.3.2.1. Utricle: Detects horizontal linear acceleration (forward/backward, side-to-side). 34.8.3.2.2. Saccule: Detects vertical linear acceleration (up/down). 34.8.3.3. Detection Mechanism: Each otolith organ contains a gelatinous structure called the otolithic membrane, which is embedded with tiny calcium carbonate crystals called otoconia. When the head accelerates linearly, the otoconia shift, pulling on the otolithic membrane and bending the hair cells within it. This bending triggers nerve impulses that are sent to the brain. 34.9. Understand vestibular pathways in the brain and how they interact with other systems (eyes, cerebellum) 34.9.1. Vestibular Nuclei 34.9.2. Projections include: 34.9.2.1. Cerebellum 34.9.2.2. Thalamus → Cerebral cortex 34.9.2.3. Oculomotor nuclei 34.9.2.4. Vestibulospinal Tracts 35CNIX-XII 35. Glossopharyngeal Nerve 35.1. Describe the gross anatomy and functions 35.1.1. The glossopharyngeal nerve (CN IX) is a mixed nerve that provides both motor and sensory innervation to the head and neck regions. It emerges from the medulla oblongata and exits the skull through the jugular foramen. 35.1.2. Stylopharyngeus Muscle: This muscle, innervated by CN IX, elevates the pharynx and larynx during swallowing and speech. 35.1.3. General Sensory: Provides sensation to the posterior one-third of the tongue, pharynx, tonsils, and middle ear. 35.1.4. Special Sensory (Taste): Transmits taste sensations from the posterior one-third of the tongue. 35.1.5. Baroreceptors and Chemoreceptors: Monitors blood pressure and blood gas levels in the carotid sinus and carotid body. 35.1.6. Parasympathetic Function: 35.1.6.1. Parotid Gland: Via the otic ganglion, CN IX stimulates the parotid gland to secrete saliva. 35.1.6.2. Otic Ganglion 35.1.6.2.1. The otic ganglion is a small parasympathetic ganglion located near the mandibular foramen. It receives preganglionic parasympathetic fibers from the glossopharyngeal nerve via the lesser petrosal nerve. Postganglionic fibers from the otic ganglion travel with the auriculotemporal nerve to innervate the parotid gland. 35.2. Vagus Nerve 35.2.1. Describe the gross anatomy and functions 35.2.1.1. The vagus nerve is the longest cranial nerve, extending from the brainstem to the abdomen. It's often referred to as the "wandering nerve" due to its extensive distribution. This nerve plays a crucial role in various bodily functions, making it a vital component of the parasympathetic nervous system. 35.2.1.2. Origin: The vagus nerve emerges from the medulla oblongata. 35.2.1.3. Course: It exits the skull through the jugular foramen, descends through the neck, thorax, and abdomen. 35.2.2. Branches: 35.2.2.1. Pharyngeal Branches: These innervate the pharyngeal muscles involved in swallowing. 35.2.2.2. Recurrent Laryngeal Nerve: This nerve loops under the aortic arch on the left side and the subclavian artery on the right side before ascending back to the larynx. It innervates most of the intrinsic muscles of the larynx, responsible for voice production. 35.2.2.3. Cardiac Branches: These branches innervate the heart, slowing heart rate and reducing contractility. 35.2.2.4. Pulmonary Branches: These branches innervate the lungs, bronchi, and pleura, regulating breathing and airway constriction. 35.2.2.5. Esophageal Branches: These branches innervate the esophagus, controlling peristalsis and relaxation of the lower esophageal sphincter. 35.2.2.6. Abdominal Branches: These branches innervate the stomach, small intestine, liver, pancreas, and other abdominal organs, regulating digestion, secretion, and motility. 35.2.3. Functions: 35.2.3.1. Parasympathetic Innervation: The vagus nerve is the primary parasympathetic nerve, promoting "rest and digest" functions. It slows heart rate, stimulates digestion, and increases intestinal motility. 35.2.3.2. Sensory Function: It transmits sensory information from the pharynx, larynx, and internal organs, including taste sensations from the epiglottis and the root of the tongue. 35.2.3.3. Motor Function: It innervates muscles of the pharynx, larynx, and soft palate, involved in swallowing, speech, and vocalization. 35.2.4. Describe the muscles of the pharynx & larynx 35.2.4.1. Muscles of the Pharynx 35.2.4.1.1. The pharynx is a muscular tube that connects the nasal and oral cavities to the larynx and esophagus. Its muscles are essential for swallowing and speech. 35.2.4.2. Constrictors of the Pharynx 35.2.4.2.1. Superior Pharyngeal Constrictor: 35.2.4.2.1.1. Originates from the pterygoid hamulus, pterygomandibular raphe, and the alveolar process of the mandible. 35.2.4.2.1.2. Inserts into the median pharyngeal raphe. 35.2.4.2.1.3. Function: Constricts the upper pharynx during swallowing. 35.2.4.2.2. Middle Pharyngeal Constrictor: 35.2.4.2.2.1. Originates from the stylohyoid ligament and the greater and lesser horns of the hyoid bone.1 35.2.4.2.2.2. Inserts into the median pharyngeal raphe. 35.2.4.2.2.3. Function: Constricts the middle pharynx during swallowing. 35.2.4.2.3. Inferior Pharyngeal Constrictor: 35.2.4.2.3.1. Originates from the thyroid and cricoid cartilages. 35.2.4.2.3.2. Inserts into the median pharyngeal raphe. 35.2.4.2.3.3. Function: Constricts the lower pharynx during swallowing. 35.2.4.3. Elevators and Dilators of the Pharynx 35.2.4.3.1. Levator Veli Palatini: 35.2.4.3.1.1. Originates from the petrous temporal bone. 35.2.4.3.1.2. Inserts into the soft palate. 35.2.4.3.1.3. Function: Elevates the soft palate during swallowing and speech. 35.2.4.3.2. Palatoglossus: 35.2.4.3.2.1. Originates from the soft palate. 35.2.4.3.2.2. Inserts into the side of the tongue. 35.2.4.3.2.3. Function: Elevates the posterior tongue and narrows the oropharyngeal isthmus. 35.2.4.3.3. Palatopharyngeus: 35.2.4.3.3.1. Originates from the soft palate. 35.2.4.3.3.2. Inserts into the thyroid cartilage and pharyngeal wall. 35.2.4.3.3.3. Function: Elevates the pharynx and larynx, narrows the oropharyngeal isthmus, and contributes to velopharyngeal closure. 35.2.4.3.4. Stylopharyngeus: Originates from the styloid process of the temporal bone. 35.2.4.3.4.1. Inserts into the thyroid cartilage and pharyngeal wall. 35.2.4.3.4.2. Function: Elevates the pharynx and larynx. 35.2.5. Muscles of the Larynx 35.2.5.1. The larynx is a complex structure involved in voice production, breathing, and swallowing. 35.2.5.2. Cricothyroid: 35.2.5.2.1. Originates from the anterior surface of the cricoid cartilage. 35.2.5.2.2. Inserts into the inferior cornu of the thyroid cartilage. 35.2.5.2.3. Function: Tenses the vocal folds, increasing pitch. 35.2.5.3. Oblique Arytenoid: 35.2.5.3.1. Originates from the posterior surface of the arytenoid cartilage. 35.2.5.3.2. Inserts into the apex of the opposite arytenoid cartilage. 35.2.5.3.3. Function: Adducts the vocal folds and rotates the arytenoid cartilages. 35.2.5.4. Posterior Cricoarytenoid: 35.2.5.4.1. Originates from the posterior surface of the cricoid lamina. 35.2.5.4.2. Inserts into the muscular process of the arytenoid cartilage. 35.2.5.4.3. Function: Abducts the vocal folds, opening the glottis for breathing. 35.2.6. Understand how the vocal cords produce sound 35.2.6.1. Vocal cord vibration is a complex physiological process that involves the coordinated action of multiple muscles and cartilages within the larynx. This intricate mechanism enables us to produce a vast range of sounds, from a soft whisper to a loud shout. 35.2.6.1.1. Inhalation: Air is drawn into the lungs, increasing lung pressure. 35.2.6.1.2. Vocal Fold Adduction: The vocal folds, composed of muscle tissue and mucous membrane, are brought together, partially occluding the glottis (the opening between the vocal folds). 35.2.6.1.3. Subglottal Air Pressure: As air is expelled from the lungs, it builds up subglottal pressure, forcing the vocal folds apart. 35.2.6.1.4. Vocal Fold Vibration: The sudden release of air causes the vocal folds to vibrate rapidly. This vibration generates sound waves. 35.2.6.1.5. Vocal Tract Resonance: The shape and configuration of the vocal tract (pharynx, oral cavity, and nasal cavity) modify the sound produced by the vocal folds, resulting in different speech sounds. 35.2.6.2. Factors Affecting Vocal Cord Vibration: 35.2.6.2.1. Muscle Tension: The tension in the vocal folds, controlled by intrinsic laryngeal muscles like the vocalis and cricothyroid, determines the fundamental frequency or pitch of the sound. Increased tension results in higher pitch, while decreased tension produces lower pitch. 35.2.6.2.2. Subglottal Air Pressure: The intensity or loudness of the sound is influenced by the subglottal air pressure. Higher air pressure leads to louder sounds. 35.2.6.2.3. Vocal Tract Configuration: The shape and position of the articulators (tongue, lips, and soft palate) modify the sound waves, resulting in different vowels and consonants. 35.3. Hypoglossal Nerve 35.4. Describe the gross anatomy and functions 35.4.1. Origin: The hypoglossal nerve originates from the hypoglossal nucleus located in the medulla oblongata. 35.4.2. Course: It exits the skull through the hypoglossal canal and descends into the neck. 35.4.3. Innervation: It primarily innervates the intrinsic and extrinsic muscles of the tongue 35.4.4. Functions: The hypoglossal nerve is a purely motor nerve, responsible for: 35.4.5. Tongue Movement: It innervates all the intrinsic and extrinsic muscles of the tongue, except for the palatoglossus muscle, which is innervated by the vagus nerve.1 35.4.6. Speech: The precise movements of the tongue are essential for articulation and clear speech. 35.4.7. Swallowing: The tongue plays a crucial role in propelling food bolus into the pharynx during the swallowing process. 35.5. Describe the muscles of the tongue 35.5.1. The tongue is a complex muscular organ that plays a crucial role in speech, mastication, and swallowing. It is composed of both intrinsic and extrinsic muscles. While the intrinsic muscles alter the shape of the tongue, the extrinsic muscles change its position. 35.5.2. Extrinsic Muscles 35.5.2.1. Genioglossus: 35.5.2.1.1. Origin: Inner surface of the mandible, near the symphysis. 35.5.2.1.2. Insertion: Entire length of the tongue and hyoid bone. 35.5.2.1.3. Function: Protracts the tongue, depresses the tip, and can retract the tongue. 35.5.2.2. Hyoglossus: 35.5.2.2.1. Origin: Greater and lesser horns of the hyoid bone. 35.5.2.2.2. Insertion: Lateral margin of the tongue. 35.5.2.2.3. Function: Retracts and depresses the sides of the tongue. 35.5.2.3. Styloglossus: 35.5.2.3.1. Origin: Styloid process of the temporal bone. 35.5.2.3.2. Insertion: Sides of the tongue. 35.5.2.3.3. Function: Retracts and elevates the sides of the tongue. 35.5.2.4. Intrinsic Muscles 35.5.2.4.1. Superior Longitudinal Muscle: Shortens the tongue and turns the tip upward. 35.5.2.4.2. Inferior Longitudinal Muscle: Shortens the tongue and turns the tip downward. 35.5.2.4.3. Transverse Muscle: Narrows and elongates the tongue. 35.5.2.4.4. Vertical Muscle: Flattens and widens the tongue. 35.5.3. All of these muscles are innervated by the hypoglossal nerve (CN XII), except for the palatoglossus muscle, which is innervated by the vagus nerve (CN X). 35.6. Accessory Nerve 35.6.1. Describe the gross anatomy and functions 35.6.1.1. The accessory nerve (CN XI) is primarily a motor nerve responsible for innervating specific muscles in the neck and shoulders. It has a unique dual origin, with both cranial and spinal components. 35.6.2. Cranial Root: 35.6.2.1. Originates from the medulla oblongata. 35.6.2.2. Joins the vagus nerve (CN X) and provides motor innervation to some pharyngeal muscles. 35.6.3. Spinal Root: 35.6.3.1. Originates from the spinal cord, specifically from the upper cervical segments (C1-C5). 35.6.3.2. Exits the skull through the jugular foramen. 35.6.4. Functions: The primary function of the accessory nerve is to innervate two major muscles: 35.6.5. Sternocleidomastoid Muscle: This muscle allows for head rotation, flexion, and lateral flexion. 35.6.6. Trapezius Muscle: This muscle is involved in shoulder elevation, retraction, and depression, as well as neck extension. 35.7. Identify lesions of CN IX–XII 35.7.1. Glossopharyngeal Nerve (CN IX) Lesions 35.7.1.1. Difficulty swallowing 35.7.1.2. Loss of taste sensation on the posterior one-third of the tongue 35.7.1.3. Impaired gag reflex 35.7.1.4. Dry mouth (due to impaired parotid gland function) 35.7.2. Vagus Nerve (CN X) Lesions 35.7.2.1. Difficulty swallowing (dysphagia) 35.7.2.2. Hoarseness or loss of voice (dysphonia) 35.7.2.3. Nasal regurgitation 35.7.2.4. Loss of gag reflex 35.7.2.5. Cardiac arrhythmias 35.7.2.6. Gastrointestinal disturbances 35.7.3. Accessory Nerve (CN XI) Lesions 35.7.3.1. Weakness or paralysis of the sternocleidomastoid and trapezius muscles 35.7.3.2. Difficulty turning the head 35.7.3.3. Shoulder drooping 35.7.3.4. Weakness in lifting the shoulders 35.7.4. Hypoglossal Nerve (CN XII) Lesions 35.7.4.1. Tongue deviation towards the side of the lesion 35.7.4.2. Difficulty with tongue movements 35.7.4.3. Impaired speech articulation 35.7.4.4. Difficulty swallowing 35.7.5. Clinical Syndromes Associated with CN IX-XII Lesions 35.7.5.1. Bulbar palsy: A lower motor neuron lesion affecting CN IX-XII, resulting in weakness, atrophy, and fasciculations of the tongue and bulbar muscles. 35.7.5.2. Pseudobulbar palsy: An upper motor neuron lesion affecting CN IX-XII, resulting in spastic dysarthria, dysphagia, and emotional lability.
