language and speech anatomy

Importance of Reviewing Anatomy in Speech Pathology Training

Importance of Reviewing Anatomy in Speech Pathology Training

• Anatomical Areas of Focus:

  • Oral Cavity

  • Oropharynx

  • Hypopharynx

• Functional Significance:

  • These regions are common to both the respiratory and digestive systems.

  • They serve multiple functions:

    • Airway for breathing.

    • Speech production.

    • Swallowing.

• Impact of Head and Neck Cancer:

  • Cancer in these regions can significantly affect:

    • Swallowing functions.

    • Speech capabilities.

  • Treatment interventions (e.g., surgery, radiotherapy) may further impact these functions.

• Role of Speech Pathologists:

  • Integral part of a multidisciplinary team in the care of clients with head and neck cancer.

  • Responsibilities include:

    • Assessing clients prior to definitive treatment (surgery).

    • Conducting assessments post-surgery.

    • Providing long-term care support.

• Contribution to Recovery:

  • Speech pathologists serve as a valuable resource for clients in their recovery from diseases affecting the oral cavity and pharyngeal regions.

  • Emphasis on understanding anatomical contexts enhances the effectiveness of interventions and patient care.

• Conclusion:

  • The introduction to anatomy is essential for understanding the complexities of swallowing and speech in patients with head and neck cancer, guiding the interventions provided by speech pathologists.

 

Overview of the Ventricular System

Overview of the Ventricular System

• Central Part of the Brain:

  • The ventricular system is a critical component located centrally within the brain.

Key Components

• Lateral Ventricles:

  • These are the first structures to consider within the ventricular system.

  • Action Item: It’s helpful to mark these in blue on your anatomical images if you haven't done so already.

• Connection to the Third Ventricle:

  • The lateral ventricles connect to the third ventricle via a narrow passage known as the interventricular foramen.

• Posterior View:

  • The posterior part of the lateral ventricles can be visualised.

Clinical Implications

• Narrow Openings:

  • The interventricular foramen and cerebral aqueduct are both narrow openings between the ventricles.

• Potential Blockages:

  • If there is a blockage at these narrow points, the affected ventricle will continue to produce cerebrospinal fluid (CSF).

  • This leads to an increase in size of the ventricle, resulting in a mass effect or increased pressure on the brain due to the accumulation of fluid.

This understanding of the ventricular system is essential for grasping how conditions like hydrocephalus can arise when normal CSF flow is obstructed, leading to significant clinical consequences.

View of the Ventricular System with Surrounding Structures

Clinical Considerations

• Narrowing Points:

  • The ventricular system contains several narrowing points where blockages can occur:

    • Interventricular Foramen: Between the lateral ventricles and the third ventricle.

    • Cerebral Aqueduct: Between the third and fourth ventricles.

• Implications of Blockages:

  • Blockages at these sites can lead to conditions such as hydrocephalus, resulting from the accumulation of cerebrospinal fluid (CSF) and increased intracranial pressure.

Overview of the Thalamus

Functions of the Thalamus

• Relay Station:

  • The thalamus acts as a relay station for sensory information.

  • It houses the third-order neuron cell bodies in various sensory pathways, making it crucial for processing sensory input before it reaches the cortex.

• Motor Control:

  • In addition to sensory functions, the thalamus plays a role in motor control by relaying information between different motor pathways.

Clinical Considerations

• Impact of Stroke:

  • The thalamus can be affected by deep strokes known as lacunar infarcts.

  • These infarcts can lead to significant functional impairments, as the thalamus is integral to sensory and motor processing.

Overview of Basal Nuclei

Overview of Basal Nuclei

• Anatomical Features:

  • The basal nuclei are highlighted in pink on transverse sections.

  • They consist of:

    • Lentiform Nucleus:

      • Shape: Pea-shaped

      • Components:

        • Putamen: Outer portion, acts as the input nucleus.

        • Globus Pallidus: Inner portion, serves as the output nucleus.

    • Caudate Nucleus: Located adjacent to the lateral ventricle.

Functions of Basal Nuclei

• Motor Control:

  • The putamen and globus pallidus are primarily involved in motor control, facilitating the regulation of voluntary movements.

• Cognitive and Emotional Functions:

  • Combinations of the caudate nucleus and the putamen play roles in cognition and emotion control.

Clinical Considerations

• Neurological Damage:

  • The basal nuclei can be affected by focal neurological damage, leading to motor, cognitive, or emotional impairments. Understanding their role is crucial for diagnosing and managing conditions like Parkinson’s disease, Huntington’s disease, and other movement disorders.

Overview of White Matter in the Brain

Overview of White Matter in the Brain

• White Matter Composition:

  • Contains axons that traverse the cerebral hemispheres.

  • Facilitates communication between different brain regions.

Key Structures of White Matter

1. 6 Callosum:

   • Connects the two cerebral hemispheres.

   • Plays a crucial role in interhemispheric communication.

2. Corona Radiata:

   • Serves as a pathway for connections between the cortex and the internal capsule.

3. Internal Capsule:

   • Divided into three parts:

     • Anterior Limb: Involved in connections to the frontal lobe.

     • Genu: Concentrated fibers for connections to the head and neck areas.

     • Posterior Limb: Transmits fibers to and from the body.

Clinical Implications

• Damage Consequences:

  • Small areas of damage in the white matter can disrupt multiple pathways.

  • Example from Radiopedia:

    • MRI Scan: Shows enhancement or infarct in the posterior limb and genu of the internal capsule.

    • Clinical Outcome: Damage on the right side may result in hemiplegia affecting the left side of the body.

Overview of Coronal Sections of the Brain

Overview of Coronal Sections of the Brain

• Central Structures:

  • Ventricles:

    • Lateral Ventricles: Located laterally.

    • Third Ventricle: Centrally located and surrounded by the thalamus.

• Key Features:

  • Corpus Callosum:

    • Positioned on the superior surface of the lateral ventricles.

    • Contains commissural fibers that connect the two cerebral hemispheres.

Types of Fibers in the Brain

1. Commissural Fibers:

   • Connect the left and right hemispheres of the brain (e.g., corpus callosum).

2. Association Fibers:

   • Connect adjacent areas within a single lobe (e.g., primary sensory areas to secondary areas).

3. Projection Fibers:

   • Run in the corona radiata and internal capsule.

   • Ascend and descend, connecting the cortex to lower brain regions and the spinal cord.

Clinical Implications

• Impact of Damage:

  • Small areas of damage, such as a small infarct, can disrupt multiple pathways.

  • Potential consequences include impairments in both sensory and motor functions.

Area Supplied by Cerebral Arteries

1.  

   • Anterior Cerebral Artery (ACA): Supplies the medial parts of the frontal lobes and superior medial parietal lobes.

   • Middle Cerebral Artery (MCA): Supplies lateral aspects of the cerebral hemispheres, including critical areas for language and motor control.

   • Posterior Cerebral Artery (PCA): Supplies the occipital lobe and the inferior part of the temporal lobe.

Blood Supply of the Brain

• Two Sets of Paired Vessels:
  The brain receives its blood supply from two sets of paired vessels:

  • Anteriorly:

    • Internal Carotid Arteries:

      • Branches of the common carotid artery.

      • They originate at the level of the superior edge of the thyroid cartilage.

  • Posteriorly:

    • Vertebral Arteries:

      • Ascend through the cervical spine within the transverse foramina.

      • Join to form a single basilar artery, which runs in the basilar groove on the ventral surface of the pons.

Circle of Willis and Collateral Circulation

• Formation of the Circle of Willis:
  The Circle of Willis is an essential structure that provides collateral circulation in the brain, formed by the following components:

  • Two Internal Carotid Arteries:

    • Supply blood to the anterior part of the brain.

  • Two Anterior Cerebral Arteries:

    • Branches of each internal carotid artery.

  • Anterior Communicating Artery:

    • Intervenes between the two anterior cerebral arteries, allowing communication.

  • Two Posterior Communicating Arteries:

    • Branches of the internal carotid artery that connect to the posterior circulation.

  • Two Posterior Cerebral Arteries:

    • Bifurcations of the basilar artery that supply the posterior part of the brain.

• Importance of Collateral Circulation:

  • The Circle of Willis is crucial for bypassing blockages or gradual narrowing of blood supply in the arteries.

  • It ensures blood flow remains adequate, especially when issues arise in the internal carotid arteries.

  • Limitations:

    • If blockages occur beyond the Circle of Willis in the branches of the anterior, middle, or posterior cerebral arteries, the collateral circulation may not be effective.

• Variability in Circulation:

  • Not all patients have a completely patent Circle of Willis.

  • Some individuals may have hypoplastic (narrowed) communicating arteries, which compromises collateral circulation and can affect overall cerebral blood flow.

This information is critical for understanding how the brain compensates for vascular issues and how variations in anatomy can impact health outcomes.

Major Branches of the Cerebral Circulation

• Cerebral Arteries Overview:
  The cerebral circulation consists of major arteries that supply different areas of the brain, crucial for understanding the implications of strokes and other vascular issues.

• Key Arteries:

  • Anterior Cerebral Artery (ACA):

    • Supplies the medial surface of the frontal and parietal lobes.

    • Important for functions related to leg motor control and higher cognitive functions such as decision-making.

  • Middle Cerebral Artery (MCA):

    • Supplies the lateral surface of the cerebral hemispheres, including parts of the frontal, parietal, and temporal lobes.

    • Vital for arm and face motor control and language functions (in the left hemisphere).

  • Posterior Cerebral Artery (PCA):

    • Supplies the occipital lobe and the inferior part of the temporal lobe.

    • Essential for visual processing and memory.

• Visual Analogy:

  • The anatomy of the Circle of Willis and its branches can be likened to a Martian figure:

    • Legs: Formed by the vertebral arteries.

    • Body: Represented by the basilar artery.

    • Arms:

      • First set: Posterior cerebral arteries.

      • Second set: Middle cerebral arteries.

    • Eyes: Internal carotid arteries.

    • Antennae: Anterior cerebral arteries.

• Understanding Stroke Implications:

  • Recognising the territories supplied by these arteries is crucial for understanding the clinical manifestations of strokes.

  • Blockages or damage to specific arteries will lead to distinct deficits in motor, sensory, or cognitive functions depending on the regions affected.

Blood Supply of the Brain: Cerebral Arteries

• Anterior Cerebral Arteries (ACA):

  • Pathway: Runs over the corpus callosum in the longitudinal fissure.

  • Supplies:

    • Medial surface of the frontal and parietal lobes.

    • Lower limb portion of the primary motor cortex and primary somatosensory cortex.

• Middle Cerebral Arteries (MCA):

  • Pathway: Passes through the lateral sulcus.

  • Supplies:

    • Lateral surface of the frontal, parietal, and temporal lobes.

    • Primary motor cortex for the face and upper limb.

    • Primary somatosensory cortex for the face and upper limb.

    • In the dominant hemisphere (usually the left):

      • Includes Broca’s area (speech production).

      • Includes Wernicke’s area (language comprehension).

• Posterior Cerebral Arteries (PCA):

  • Pathway: Runs superior to the tentorium cerebelli.

  • Supplies:

    • Inferior surface of the temporal lobe.

    • Posterior part of the occipital lobe.

    • Primary visual cortex (responsible for vision).

    • Areas of the temporal cortex associated with memory.

Visualisation Techniques

• These cerebral arteries can be visualised using various radiographic techniques, such as:

  • MRI (Magnetic Resonance Imaging).

  • CT Scans (Computed Tomography).

  • Angiography (to specifically view blood vessels).

  • 

Angiography and Digital Subtraction Angiogram

• Angiography:

  • A procedure where a thin wire is passed through the blood vessels.

  • Dye is injected to outline the territories of the cerebral arteries.

  • Key Arteries Visualised:

    • Anterior Cerebral Artery (ACA): Located adjacent to the longitudinal fissure.

    • Middle Cerebral Artery (MCA): Located adjacent to the lateral sulcus.

    • Note: The Posterior Cerebral Artery (PCA) may not be visible in certain images.

• Digital Subtraction Angiogram (DSA):

  • A technique used to create clear images of blood vessels.

  • Involves imaging the area with a CT scan.

  • The skull and cerebral elements are subtracted from the image, allowing for a clearer view of the blood supply.

  • This method enhances the visualization of the vascular structures, facilitating diagnosis and treatment planning for conditions such as strokes or vascular malformations.

Importance of Angiography

• Provides detailed information about the blood supply to the brain.

• Helps in identifying blockages, aneurysms, or other vascular issues that may impact brain function.

• Assists healthcare professionals in planning surgical or non-surgical interventions effectively.

Blood Supply of Deep White and Grey Matter

• Penetrating Arteries:

  • The blood supply to the deep white and grey matter is primarily provided by penetrating arteries that branch off from the middle cerebral artery (MCA).

  • Lenticulostriate Arteries:

    • These arteries are specifically involved in supplying the lentiform nucleus (which includes the putamen and globus pallidus) and adjacent structures.

    • They have a straight appearance and are crucial for maintaining the vascular health of deep brain structures.

• Impact of Hypertension:

  • Hypertension (high blood pressure) can lead to the blockage of these lenticulostriate arteries.

  • When these arteries become obstructed, it can result in a specific type of stroke known as a lacunar infarct.

Lacunar Infarct

• Definition:

  • A small, deep brain infarct resulting from the occlusion of a penetrating artery supplying subcortical structures.

• Causes:

  • Primarily associated with chronic hypertension and conditions that affect small blood vessels.

• Effects:

  • Can lead to various neurological deficits depending on the specific area of the brain affected.

  • Commonly results in motor or sensory impairments, and can impact functions such as coordination, balance, and cognitive abilities.

Understanding the blood supply to the deep structures of the brain is crucial for diagnosing and managing conditions that can lead to lacunar strokes and their associated complications.

 

Venous Drainage of the Brain

• Dural Venous Sinuses:

  • The venous drainage of the brain occurs through the dural venous sinuses, which are formed between the folds of the dura mater—specifically, the endosteal fold and the meningeal fold.

• Key Components:

  • Superior Sagittal Sinus:

    • Located within the falx cerebri and runs along the top of the brain.

  • Inferior Sagittal Sinus:

    • Also located in the falx cerebri, draining into the straight sinus.

  • Straight Sinus:

    • Formed by the convergence of the inferior sagittal sinus and the great cerebral vein.

  • Confluence of Sinuses:

    • A junction where several sinuses meet, leading to the transverse sinus.

  • Transverse Sinus:

    • Continuation from the confluence, which drains into the sigmoid sinus.

  • Sigmoid Sinus:

    • Drains into the internal jugular vein, which then carries deoxygenated blood away from the brain.

• Function:

  • This system of venous drainage is crucial for removing deoxygenated blood and waste products from the cranial cavity, ensuring proper cerebral blood flow and maintaining intracranial pressure.

Understanding the venous drainage system is essential for assessing conditions such as venous sinus thrombosis and other cerebrovascular disorders that can impact brain health.

Ventricular System and Cerebrospinal Fluid (CSF) Circulation

• erebrospinal Fluid (CSF) Circulation:

  • Production:

    • CSF is primarily produced by the choroid plexus, which is located within the ventricles, particularly in the lateral and third ventricles.

  • Circulation Pathway:

    • Lateral Ventricles → Interventricular Foramen → Third Ventricle → Cerebral Aqueduct → Fourth Ventricle.

    • From the fourth ventricle, CSF can flow into the subarachnoid space surrounding the brain and spinal cord through openings called foramina (e.g., foramen of Magendie and foramina of Luschka).

  • Absorption:

    • CSF is reabsorbed into the bloodstream through arachnoid granulations that protrude into the dural venous sinuses.

• Function of CSF:

  • Protection: Acts as a cushion to protect the brain from trauma.

  • Buoyancy: Reduces the effective weight of the brain, preventing damage from pressure on the base of the skull.

  • Nutrient Delivery: Transports nutrients and removes waste products from the brain.

Understanding the ventricular system and CSF circulation is crucial for diagnosing and managing neurological conditions such as hydrocephalus, subarachnoid hemorrhage, and meningitis.

Circulation of Cerebrospinal Fluid (CSF)

• Production of CSF:

  • CSF is produced by the choroid plexus, which is located in:

    • Lateral Ventricles

    • Fourth Ventricle

• Circulation Pathway:

  • After production, CSF circulates through the ventricular system and then into the subarachnoid spacesurrounding the brain.

  • The pathway includes:

    • Lateral Ventricles →

    • Interventricular Foramen →

    • Third Ventricle →

    • Cerebral Aqueduct →

    • Fourth Ventricle →

    • Subarachnoid Space

• Reabsorption:

  • CSF is reabsorbed into the bloodstream through arachnoid granulations (also known as arachnoid villi).

  • These granulations protrude into the dural venous sinuses, specifically the superior sagittal sinus.

• Exit from the Cranial Cavity:

  • Once reabsorbed, CSF exits the cranial cavity along with dural venous blood into the venous system.

• Functions of CSF:

  • Provides cushioning for the brain.

  • Helps maintain homeostasis within the central nervous system.

  • Delivers nutrients and removes waste products.