Cervical Vertebrae Anatomy Quiz

Cervical Vertebrae

• Cervical vertebrae are small, oval, and curved with a large vertebral foramen.
• They have long, split spinous processes, pointing inferiorly.
• They have transverse foramina.
• The spinous process in the cervical region is typically bifid (except C1/C7) and impalpable.
• They support the skull, stabilize the brain and spinal cord, and allow controlled movement of the head.

Thoracic Vertebrae

• Thoracic vertebrae are medium in size, heart-shaped, and have flat faces with facets for rib articulations.
• They have a medium-sized vertebral foramen.
• They have long, slender, inferiorly-pointing spinous processes.
• All vertebrae except T11 and T12 have facets for rib joints.
• They support the weight of the head, neck, upper limbs, and chest.

Lumbar Vertebrae

• Lumbar vertebrae are massive, oval, and have flat faces.
• They have a small vertebral foramen, a blunt, broad, posteriorly-pointing spinous process, and short transverse processes.
• They do not have foramina or articular facets.
• They support the weight of the entire body.

Anatomy of the Neck

• The vertebral canal contains the spinal cord, meninges, CSF, vertebral venous plexus, spinal arteries, spinal veins, and epidural fat.
• The odontoid process (peg) is a protruberance of C2, developmentally arising from C1 and held in place by the cruciate ligament.
• The alar ligaments extend from the odontoid process to the foramen magnum.

Movements of the Neck

• Flexion and extension (nodding) occur between the atlas and occiput.
• Rotation occurs between C1 and C2.

Nuchal Ligament

• The nuchal ligament located behind the vertebral column brings the head to an upright position, functioning as an elastic structure.

Muscles of the Neck

• Trapezius elevates the scapula and can assist in angling the glenoid fossa superiorly.
• Levator Scapulae elevates the scapula and can assist in angling the glenoid fossa inferiorly.
• Deep Cervical Muscles extend and stabilize the cervical spine.
• Sternocleidomastoid (SCM) causes ipsilateral flexion of the cervical spine and contralateral rotation of the head.
• Infrahyoid Muscles (including omohyoid and sternothyroid) depress the hyoid.
• Scalene Muscles act as accessory muscles of respiration and contribute to flexion and lateral rotation of the neck.

Hyoid Bone

• The hyoid bone sits at C3 and is derived from pharyngeal arches 2 and 3.
• Suprahyoid muscles sit superior to the hyoid, while infrahyoid muscles sit inferior.
• These muscles play a role in swallowing, depressing the mandible, elevating the hyoid bone, and elevating the floor of the oral cavity.

Neck Vasculature

• The common carotid artery branches into the internal carotid artery and external carotid artery.
• The internal carotid artery runs with the internal jugular vein and does not give off branches in the neck.
• The external carotid artery gives off numerous branches.
  • Anterior branches: superior thyroid artery, lingual artery, facial artery, maxillary artery, superficial temporal artery.
  • Posterior branches: ascending pharyngeal artery, occipital artery, posterior auricular artery.
• The vertebral artery passes through the transverse foramina of cervical vertebrae (except C7).

Fascial Layers of the Neck

• Investing fascia encircles the neck immediately beneath the skin.
  • It splits to enclose the sternocleidomastoid and trapezius muscles.
• Prevertebral fascia encircles the cervical spine.
  • It contains the cervical vertebral column, vertebral muscles, spinal nerves, and phrenic nerve.
  • It forms part of the carotid sheath's posterior border.
• Pretracheal fascia extends from the hyoid bone to the pericardium.
  • It encloses the infrahyoid muscles and the thyroid gland, trachea, and esophagus.
• Carotid sheath is a tubular structure surrounding the common carotid artery, internal jugular vein, and vagus nerve.
• Buccopharyngeal fascia is a component of the pretracheal fascia that surrounds the pharynx.
  • It is continuous with the pretracheal fascia inferiorly.

Spaces of the Neck

• Parotid space surrounds the parotid gland – suprahyoid
• Masseter space is more medial to the parotid space – suprahyoid
• Submandibular space is located under the mandible – suprahyoid
• Thyroid space surrounds the thyroid – infrahyoid
• Danger space is located in front of the prevertebral fascia – both infra and suprahyoid
• Retropharyngeal space is located anterior to the danger space – both infra and suprahyoid
• Carotid space surrounds the carotid arteries, etc – both infra and suprahyoid

Compartments of the Neck

• Visceral (central) compartment:
  • Largest compartment
  • Contains vital structures like the larynx, trachea, esophagus, thyroid, and parathyroid glands.
  • Surrounded by pretracheal fascia.
• Vascular (lateral) compartment:
  • Contains the carotid sheath, common carotid artery, internal jugular vein, and vagus nerve.
• Muscular (posterior) compartment:
  • Contains the deep muscles of the neck (e.g., scalene and prevertebral muscles)
  • Houses the cervical vertebrae and cervical spinal cord.

Triangles of the Neck

• Anterior triangle:
  • Boundaries: middle of neck anteriorly, inferior border of the mandible superiorly, and anterior border of the SCM laterally.
  • Contains submental, submandibular, carotid, and muscular triangles.
  • Key structures: carotid arteries.
• Posterior triangle:
  • Boundaries: posterior border of the SCM anteriorly, anterior border of trapezius posteriorly, and the middle 1/3 of the clavicle inferiorly.
  • Contains occipital and supraclavicular triangles.
  • Key structures: brachial plexus.

Thoracic Outlet Syndrome

• Thoracic outlet syndrome occurs when structures such as the brachial plexus (nerves), subclavian artery, or subclavian vein are compressed in the space between the clavicle, first rib, and the muscles of the shoulder.
• The borders of the thoracic outlet include the pectoralis major and minor muscles anteriorly, the teres major and latissimus dorsi muscles posteriorly, the serratus anterior muscle and four ribs medially, the humerus and biceps brachii laterally, and the clavicle, scapula, and first rib superiorly.
• Structures within the thoracic outlet include the axillary artery, axillary vein, axillary lymphatics, the short head of the biceps brachii, coracobrachialis muscle, and the brachial plexus.
• Common causes include poor posture, trauma, and congenital conditions like an extra cervical rib.
• Symptoms include pain, numbness, tingling, weakness, and a pulsating lump.

Thyroid Anatomy

• The thyroid gland consists of two lobes connected by an isthmus.
• It lies across the second to third tracheal rings, posterior to the sternothyroid muscles.
• The cricoid cartilage and tracheal rings wrap around the thyroid gland.
• The laryngeal cartilage lies inferior to the thyroid gland.
• The thyroid gland occupies the pretracheal fascia, alongside the pharynx and esophagus.
• Berry's ligament connects the trachea to each lobe of the thyroid gland.

Thyroid Surgical Access

• Open thyroidectomy involves a traditional incision through the platysma and strap muscles, leading to a visible scar and potential complications.
• Minimally invasive thyroidectomy accesses the thyroid gland through a minimal incision, avoiding visible scars, and reducing the risk of complications.

Thyroid Complications

• Bleeding and hematomas can cause airway compromise.
• Recurrent laryngeal nerve injury can lead to true vocal fold paralysis.
• Hypoparathyroidism may occur due to direct trauma, devascularization, or removal of the parathyroid gland.
• Thyrotoxic storm occurs when the thyroid gland releases excessive hormones, potentially injuring the superior laryngeal nerve, causing hoarseness and difficulty producing high-pitched sounds.

Spaces of the Neck

• The masticator space houses the mandible body and mastication muscles.
• The danger space lies behind the retropharyngeal space, separated by the alar fascia.
• The carotid space encloses the carotid vessels.
• The parotoid space surrounds the parotid gland.
• The alar fascia constitutes the most important fascia in the neck.
• Other fascial layers include the buccopharyngeal, investing, pretracheal, and prevertebral fasciae.

Retropharyngeal Space

• Infections often originate in the lower molars or tonsils and may spread to the retropharyngeal space, extending from the mouth downwards to the T1-T2 vertebrae.
• The retropharyngeal space lies one fascia (alar fascia) away from the danger space.
• The danger space is considered dangerous due to its lack of fascial barriers, allowing infections to spread unchecked to the prevertebral space, potentially leading to meningitis and spinal cord infection.
• From anterior to posterior, the neck spaces extend: retropharyngeal, danger, and prevertebral space, reaching down to the L3 vertebrae.

Cranial Nerve Nuclei and Visual Pathway

Brainstem and Fourth Ventricle

• The brainstem comprises the medulla, pons, and midbrain.
• It contains tracts connecting the cerebrum, cerebellum, and spinal cord, nuclei for autonomic function, and cranial nerve nuclei.
• The third and fourth ventricles are located in the midline.
• The third ventricle lies superior to the fourth ventricle.
• The lateral ventricles, the largest of the ventricles, connect to the third ventricle via midline connections.
• All ventricles are filled with cerebrospinal fluid.

Brain Stem Surface Features

• The medulla oblongata forms the inferior part of the brainstem, continuous with the spinal cord at the foramen magnum.
• The pons is located superior to the medulla, connecting to the cerebellum via the middle cerebellar peduncle.
• The midbrain, a small but important region, connects the pons to the diencephalon.
• The fourth ventricle, shaped like a diamond, is bordered anteriorly by the pons and the medulla, posteriorly by the cerebellum, and inferiorly by the obex.
• The central canal of the spinal cord continues as the fourth ventricle.
• The cerebellum, a large structure located dorsal to the brainstem, connects to the brainstem via three peduncles:
  • Superior cerebellar peduncle: connects the cerebellum to the thalamus, relaying signals to the motor cortex.
  • Middle cerebellar peduncle: receives input from motor areas of the brainstem and cerebrum, and sends signals to the cerebellum.
  • Inferior cerebellar peduncle: connects the cerebellum to the spinal cord, relaying signals from the spinal cord to the cerebellum for coordination.

Cranial Nerve Nuclei

• Olfactory nerve (CN I): Arises from the olfactory bulb and passes through the cribriform plate of the ethmoid bone to reach the olfactory epithelium in the nasal cavity.
• Optic nerve (CN II): Begins at the retina and travels through the optic canal to the optic chiasm. It carries visual information from the eye to the brain.
• Oculomotor nerve (CN III): Emerges from the brainstem between the cerebral peduncles. It controls most extraocular muscles responsible for eye movement.
• Trochlear nerve (CN IV): This nerve emerges from the posterior aspect of the midbrain and controls the superior oblique muscle, involved in downward and inward eye movement.
• Trigeminal nerve (CN V): Located laterally on the brainstem, it has a motor component that controls mastication and a sensory component that conveys touch, pain, temperature, and proprioception from the face, head, and teeth.
• Abducens nerve (CN VI): It emerges from the brainstem on the medial side of the anterior surface and controls the lateral rectus muscle, responsible for outward eye movement.
• Facial nerve (CN VII): Composed of two parts: the facial nerve proper (controls facial expression) and the nervus intermedius (carries taste sensations from the anterior two-thirds of the tongue). It emerges from the brainstem near the pontomedullary junction, alongside the vestibulocochlear nerve.
• Vestibulocochlear nerve (CN VIII) : It emerges from the brainstem near the pontomedullary junction, and has two components: the vestibular nerve (controls balance and equilibrium) and the cochlear nerve (responsible for hearing).
• Glossopharyngeal nerve (CN IX) : It emerges from the brainstem laterally to the olive and carries taste sensation from the posterior third of the tongue and controls swallowing actions.
• Vagus nerve (CN X) : The vagus nerve is one of the longest cranial nerves, with a wide array of functions: regulating heart rate, digestion, and respiration. It emerges from the brainstem inferolaterally to the olive.
• Accessory nerve (CN XI): This nerve is unique because its nucleus is not located within the brainstem, but in the spinal cord. It controls the sternocleidomastoid and trapezius muscles.
• Hypoglossal nerve (CN XII): It emerges from the brainstem in the furrow between the pyramid and olive. It controls tongue movements related to swallowing and speech.

Visual Pathway

• The visual pathway begins at the eye and continues through the following structures:
  • Retina: The light-sensitive layer at the back of the eye, where photoreceptor cells convert light into electrical signals.
  • Optic nerve: Carries visual information from the retina to the optic chiasm.
  • Optic chiasm: Where the optic nerves from each eye cross over to form partial decussation, resulting in the right visual field being processed by the left hemisphere and vice versa.
  • Optic tract: Following the chiasm, the optic tracts continue carrying visual information to the thalamus.
  • Lateral geniculate nucleus (LGN): A relay nucleus within the thalamus that receives visual information and sends it to the visual cortex.
  • Visual cortex: Located in the occipital lobe of the brain, this region processes visual information to form our perception of the world.

Neural Development

• The entire nervous system develops from the neural tube during embryogenesis.
• The rostral (upper) end of the neural tube gives rise to the brain, cerebellum, and other structures.
• By the time a fetus is 3-4 weeks old, the neural tube has closed and the brain has begun to form.
• At birth, the brain is about 25% its adult size and continues to grow and develop throughout childhood and adolescence.

Key Landmarks

• Obex: The inferior tip of the fourth ventricle, marking the transition between the medulla and the spinal cord.
• Pyramids: Bulges on the anterior surface of the medulla, containing motor fibers that control voluntary movement.
• Olive: A prominent bulge on the lateral surface of the medulla, involved in cerebellar function.
• Superior and inferior colliculi: Bulging structures on the posterior surface of the midbrain involved in auditory and visual processing.
• Cerebral peduncles: Thick bundles of axons connecting the brainstem to the thalamus, important for relaying motor and sensory information.
• Internal capsule: A dense band of white matter located between the thalamus and basal ganglia.
• Corona radiata: A fan-shaped sheet of white matter fibers that extend from the internal capsule to the cerebral cortex.
• Corpus callosum: A thick band of white matter connecting the two cerebral hemispheres.

Important Points

• All cranial nerves except the trochlear nerve emerge from the ventral aspect of the brainstem.
• The dorsal columns of the spinal cord carry touch and proprioceptive information, which is relayed through the gracile and cuneate nuclei of the medulla to the thalamus.
• The pyramids of the medulla contain the corticospinal tract, which carries motor commands from the cerebrum to the spinal cord.
• The midbrain is responsible for eye movement, auditory processing, and visual reflexes.
• The visual pathway undergoes partial decussation at the optic chiasm, meaning each hemisphere receives information from both eyes.
• The brainstem is essential for relaying motor and sensory information between the cerebrum, cerebellum, and spinal cord, and plays a crucial role in regulating autonomic functions such as breathing, heart rate, and blood pressure.

Morphogens and Neural Tube Development

• Morphogens are signaling molecules that create gradients in the developing neural tube, influencing cell differentiation.
• These gradients specify the types of neurons produced by neural stem cells, leading to motor neurons ventrally and sensory neurons dorsally.
• Morphogenetic gradients also exist rostrocaudally, contributing to regional specialization along the length of the neural tube.

Brainstem and Spinal Cord Structures

• The spinal cord is innervated by structures derived from somites.
• The brainstem receives input from both somites and pharyngeal arches/pouches, contributing to a wider range of neuron types.
• The basal plate of the neural tube forms motor neurons, while the alar plate forms sensory projection relay neurons.
• Branchial (pharyngeal arch) motor neurons are a specialized type of motor neuron in the brainstem, responsible for innervating striated skeletal muscle associated with pharyngeal arches.

Sulcus Limitans

• The sulcus limitans is a key landmark in the brainstem that demarcates the boundary between the alar (sensory) and basal (motor) plates.
• This sulcus is not clearly visible in the mature spinal cord, but it is more prominent in the brainstem.

Brainstem Nuclei Organization

• Brainstem nuclei are organized in a consistent pattern, with motor nuclei generally located more medially and sensory nuclei situated laterally.
• The positions of these nuclei remain relatively constant throughout the brainstem, even in regions lacking specific nuclei types.

Cranial Nerves

• Cranial nerves are numbered from I to XII and can carry various sensory and motor modalities, including somatic motor, autonomic motor, visceral sensory, somatic sensory, and special sensory.

Oculomotor and Trochlear Nerves

• The oculomotor nerve innervates extraocular muscles and carries parasympathetic fibres to the ciliary ganglion. Its nucleus is located medially and represents a somatic motor nucleus.
• The Edinger-Westphal nucleus, located laterally, contains parasympathetic fibres.
• Both the oculomotor and trochlear nerves originate within the midbrain, and both primarily carry somatic motor fibres, though the oculomotor nerve also includes parasympathetic components.

Trigeminal Nerve

• The trigeminal nerve emerges laterally from the pons and carries both sensory and motor fibres.
• The trigeminal nerve is responsible for somatic sensation (light touch, proprioception, pain, and temperature) from the face and jaw.
• The main spinal trigeminal nucleus mediates pain and temperature sensation, while the principal sensory nucleus mediates proprioception.
• The trigeminal motor nucleus supplies muscles of mastication, which are considered branchial motor neurons.

Abducens, Facial, and Vestibulocochlear Nerves

• The abducens nerve innervates the lateral rectus muscle and carries only somatic motor fibres.
• The facial nerve carries branchial motor fibres for muscles of facial expression, autonomic motor fibres for the submandibular and sublingual glands, and visceral sensory fibres for taste from the tongue.
• The vestibulocochlear nerve has two components, the vestibular and cochlear nerves. The vestibular nerve carries sensory information for balance and head position, while the cochlear nerve carries sensory information for hearing.

Glossopharyngeal and Vagus Nerves

• The glossopharyngeal nerve innervates pharyngeal structures and carries branchial motor fibres, autonomic motor fibres, and visceral sensory fibres from the posterior 1/3 of the tongue.
• The vagus nerve innervates pharyngeal muscles and carries parasympathetic fibres to the heart and gut.
• Both nerves share the nucleus ambiguous for branchial motor fibres and the nucleus of the solitary tract for visceral sensory fibres.

Accessory Nerve

• The accessory nerve originates from the cervical spinal cord and innervates the sternocleidomastoid and trapezius muscles.
• Although it exits the skull with the glossopharyngeal and vagus nerves, it does not share nuclei with these nerves.

Hypoglossal Nerve

• The hypoglossal nerve innervates the muscles of the tongue and carries only somatic motor fibres.

Visual Pathway

• The visual pathway begins with the ganglion cells of the retina, which project their axons through the optic nerve to the optic chiasm.
• The optic chiasm allows fibres from the medial part of the retina to cross over and synapse in the contralateral lateral geniculate nucleus.
• Fibres from the lateral part of the retina remain ipsilateral and synapse in the same lateral geniculate nucleus.
• The lateral geniculate nucleus relays visual information to the primary visual cortex in the occipital lobe via the optic radiation.

Test your knowledge about the anatomy of cervical vertebrae, including their unique features, functions, and differences from other vertebrae like lumbar and thoracic. This quiz covers essential characteristics, such as pedicles, transverse foramina, and spinous processes.