Senses: Head and Neck Flashcards
Describe the Anatomical and Functional organisation of the TMJ joint
-Connects the mandible to the temporal bone
-Attachments at the mandibular fossa of the temporal bone and the condylar process of the mandible
-Modified hinge synovial joint containing fibrocartilage rather than hyaline
-2 cavities separated by an articular disc filled with synovial fluid
-The joint is articulated primarily by the muscles of mastication which are innervated by CN 5
-The joint allows for protrusion, depression, retraction, elevation and lateral movement of the mandible.
-Stabilised by 2 extrinsic and 1 intrinsic ligament
oLateral ligament (intrinsic)- the zygomatic process of the temporal bone to the neck of the mandible
oSphenomandibular ligament- spine of the sphenoid bone to the lingula on the ramus of the mandible
oStylomandibular ligament- styloid process of the temporal bone to the angle of the mandible
oThese ligaments protect against posterior dislocation but not anterior (at risk during depression movement
Discribe muscles of Mastication
Masseter: Powerful elevator
superficial heads: inferior surface of the zygomatic bone + deep heads: maxillary process of the zygomatic bones> angle and ramus of mandible.
anterior trunk of the mandibular branch of the trigeminal nerve (CN 5)
Temporalis: Retraction and elevation
Temporal fossa> coronoid process of the mandible
anterior trunk of the mandibular branch of the trigeminal nerve (CN 5)
Lateral Pterygoid: protrusion of the jaw as well as assisting with lateral movement
upper heads: roof of the infratemporal fosses + greater wings of the sphenoid bone + lower heads: lateral surfaces of the lateral plates of the sphenoid bone> pterygoid fovia of the condylar processes of the mandible
anterior trunk of the mandibular branch of the trigeminal nerve (CN 5)
Medial Pterygoid: production of lateral (side to side movements) as well as weak elevation of the mandible
superficial heads: medial surface of the lateral plates of the pterygoid + pyramidal processes at either side of the sphenoid bone + superficial head: tuberosity of the pyramidal processes of the maxillae> angle of the mandible
Main trunk of the mandibular branch of the trigeminal nerve (CN 5)
Describe the anatomy and function of the pharynx
-Pharynx can be split into 3 separate sections
oNasopharynx which is connected anatomically to the nasal cavities.
oOropharynx which is connected anatomically to the oral cavity.
oLaryngopharynx (larynx) which connected to the oesophagus and trachea
-Posteriorly it can be observed that there is a stiff pharyngobasilar fascia which holds the nasopharynx open.
-There are 3 constrictor muscles within the pharynx which move food bolus through the pharynx towards the oesophagus. These are superior, middle and inferior. These are innervated by the Vagus nerve (CNX)
-The inferior pharyngeal constrictor has a lower circular band known as the cricopharyngeus that forms a sphincter around the upper oesophagus which prevents air being drawn into the stomach.
-The pharynx also contains elevator muscles which descend from the base of the skull and fan out to the inner surface of the pharynx. Some also send fibres to the thyroid cartilage ensuring simultaneous elevation of the pharynx and the larynx during swallow
oPalatopharyngeus: Elevates the pharynx and larynx and draws soft palate downwards (CNX Vagus)
oStylopharyngeus: Originates form the styloid process and elevates the pharynx and larynx. Supplied by (CN IX Glossopharyngeal nerve)
oSalpingopharyngeus: Originates from auditory tube, elevates the pharynx and larynx. Helps open the auditory tube for equalisation of the inner ear during swallow
Describe the phases of swallowing
- Oral Phase: food bolus formed in the oral cavity by the action of chewing and concurrent tongue movements. Bolus pushed into oropharynx by tongue. The soft palate closes the nasopharynx.
- Pharyngeal phase: Contraction of constrictors and elevation of soft palate to receive food. Pushed towards oesophagus. Epiglottis closes the laryngeal inlet to protect the airway. Elevation of the hyoid muscles and then depression of hyoid and larynx following elevation.
- Oesophageal phases: Inferior constrictor contracts the upper oesophageal sphincter allowing the food bolus into the oesophagus. Peristalsis occurs.
Describe the Suprahyoid muscles
- Mylohyoid: mylohyoid line of mandible>hyoid ad fibres opposite mylohyoid. Elevatd the hyoid and floor of mouth CN 5 (3)- inferior alveolar branch
- Digastric: Anterior and posterior bellies. Anterior: medial aspect of mandible, Posterior: medial aspect of mastoid process> hyoid. Anterior= raises hyoid and opens mouth, posterior belly elevates and retracts the hyoid. Anterior same as mylo and posterior digastric branch of CN VII
- Stylohyoid: styloid process>hyoid. Pulls hyoid upwards and supplied by CNII Facial
- Geniohyoid: located superior to mylo.
Describe the Infrahyoid muscles
Infrahyoid
- Sternohyoid: posterior aspect of sternoclavicular joint and manubrium> hyoid. Depresses hyoid after elevation during swallow
- Omohyoid: Superior belly: intermediate tendon and inserts into hyoid attaches with fascial sling. Depresses and flexes hyoid.
- Thyrohyoid: Thyroid cartilage> hyoid. Depression and can raise larynx when hyoid is fixed
- Sternothyroid: Posterior aspect of manubrium and inserts into thyroid cartilage. Draws larynx down.
Sternohyoid, omo and sternothy are innervated by C1-3. Thyro= C1 via CN XII
Describe the anatomical structure, irrigation and innervation of the nasal cavity
- There are two nasal cavities separated by a septum.
- Nasal cavity contains nasal concha which help spin and moisten air. There are three concha- superior, middle and inferior. The spaces between these choncha are known as the superior, middle and inferior meatus.
- Innervation is supplied by olfactory nerves which leave the brain through the cribriform plate. These nerves arrive from the olfactory bulb (Olfactory nerve CN1)
- These nerves are associated with sensory receptors in the olfactory mucosa
Describe the paranasal sinuses and their drainage
-Hollow pockets filled with air which aid ‘air conditioning’ and lighten the skull oFrontal sinus (frontal bone): drains via the frontonasal duct into the lateral wall of the nasal cavity (hiatus semilunaris) oEthmoid sinus (ethmoid bone): 3: anterior (drains into hiatus semilunaris, middle (ethmoid bulla) and posterior (superior meatus). oMaxillary sinus (maxillary bone): hiatus semilunaris inferior to opening of frontal sinus. Drainage of frontal can enter maxillary causing spread of infection. oSphenoidal sinus (Sphenoid bone): drain onto the roof of the nasal cavity and have associations with the pituitary gland (it can be accessed through the sinuses in surgery
What is the anatomical and functional organisation of smell
- Olfactory cranial nerve branches into cranial nerves which pass through the cribriform plate and associate with smell receptors in the nasal cavity
- There are medial and lateral olfactory pathways in the olfactory bulb. The Lateral Olfactory tract utilises mitral cells which send signals to the piriform cortex, amygdala and entorhinal cortex in the brain which lead to the prefrontal cortex and hippocampus (olfactory corticles). The medial olfactory pathway involves tufted cells which provide information to the basal forebrain and limbic structures which provides emotional association with smells
What is the anatomy of the oral cavity
-Expands from the oral fissure anteriorly to the oropharyngeal isthmus posteriorly
-Split to upper and lower dental arches
-Oral vestibule is the area between the teeth and the lips
-The roof of the mouth is separated into the hard and the soft palates. The hard palate is located in the anterior portion and separates the oral and nasal cavities. It is a bony palate which is covered superiorly with respiratory mucosa and inferiorly with oral mucosa. The soft palate is a posterior continuation of the hard palate. It is a muscular structure and acts as a valve that can lower to close the oropharyngeal isthmus and elevate to separate the nasopharynx from the oropharynx.
o Muscular diaphragm – comprised of the bilateral mylohyoid muscles. It provides structural support to the floor of the mouth, and pulls the larynx forward during swallowing.
oGeniohyoid muscles – pull the larynx forward during swallowing.
oTongue – connected to the floor by the frenulum of the tongue, a fold of oral mucosa.
oSalivary glands and ducts.
-The oral cavity contains 2 arches posteriorly.
oThe palatoglossal which is the most anterior and is the site of attachment of the uvula
oThe palatopharyngeal arch which sit posteriorly
-The palatine tonsils sit between each side of these arches
Describe the surface area of the tongue
-The tongues surface contains different types of papillae that increase surface area for taste receptors.
oFungiform (most anterior)- rounded appearance
oFiliform (middle)- spiky appearance
oVallate (Most posterior)- inwards appearance.
-The terminal sulcus divides the tongue into an anterior 2/3 and posterior 1/3
oAnterior 2/3 taste is provided by CNVIII and sensory by CNV (3)
oPosterior 1/3 taste and sensory by CNIX
Describe the extrinsic muscles of the tongue
Syloglossus: Retracts and elevates tongue Genioglossus Protrudes, depresses and pulls tip of tongue back and down Hyoglossus Depresses and Retracts Palatoglossus Elevates posterior aspect of tongue - All are innervated via the hypoglossal nerve CN XII but the palatoglossus which is innervated by the vagus nerve CNX
Which pathway handles taste information?
- Ventroposteromedial pathway deals with taste
- Nucleus of thalamus relays information to the gustatory cortex which encompasses the anterior insula and frontal operculum of the frontal and insular lobes.
What are the neural pathways serving pain and nociception
-The main pathway involved in pain reception is the spinothalamic tract. It incorporates 2 different types of neurons AB and C fibres. These produce primary and secondary types of pain. Primary pain is fast acting and occurs in the myelinated AB fibres. The secondary pain response is by the C fibres which take longer to react (unmyelinated)- 2nd wave of pain. See more in neuro block.
What are some factors which influence pain experience?
-Hyperalgesia is the term used to describe increased pain
oResult of damage to tissue which causes nociceptors to be hypersensitised
oIt may involve changes to the CNS- ‘central sensitisation’ where activity is exaggerated. Inputs from low-threshold mechanoreceptors are perceived as a painful stimulus.
oDecreased threshold for sensitisation due to increase in chemicals such as bradykinins (released from damaged tissues- activates nociceptors), Substance P (released from peripheral terminals of nociceptors. Dilates blood vessels, may activate mast cells), postaglandins (synthesised from cyclo-oxygenises from damaged lipid membranes. This sensitises nociceptors, rather than activating directly).
-Conversely there are conditions which decrease sensitivity to pain. A study carried out on a young boy with a condition caused by dysfunction in an SCN9A channel. This meant he could not experience pain and had very little understanding of it. This resulted in his death at the age of only 10.
-Some analgesics work by inhibiting postglandin synthesis which in turn decreases sensitivity
Discribe the basic sensory endings in muscles
-Muscle Spindles
o Involved in fine control
o They are large, complex mechanoreceptors
o Located in muscle (dense population of muscle spindles within skeletal muscle)
o Have 2 sensory endings: primary is very fast and responds to movement and stretch. Secondary is slower and comments on length of muscle.
-Golgi Tendon Apparatus
o Located in tendons
o Also large mechanoreceptors
o Large density sensory fibres encased in connective tissue
o Respond to active force within tendons
-Fine Afferents
o Group 3 and 4 fibres which are highly myelinated as well as unmyelinated
o They are difficult to identify with a light microscope and it is difficult to make electrical recordings.
o They are believed to be polymodal (several functions such as mechanoreceptors, nociceptors etc…)
Describe Joint Receptors
- Located in the connective tissue of joint capsules, ligaments and fat pads
- They have a similar composition to golgi tendons, Ruffini endings and Pacinian corpuscles). They contain free nerve endings which respond to changes in force within the connective tissue. They can be both rapid and slow adapting.
- Utilise mechanotransduction- convert movement into electrical signal. Triggers AP in response to stretch, deformation, change in sarcomere length, stretch sensitive channels.
What are the definitions of Proprioception, position sense and kinaesthesis
- Proprioception: Signals contributing to conscious and subconscious motor control.
- Position sense: (Stataesthesis) Conscious awareness of relative positions of our body
- Kinaesthesis (movement sense): awareness of joint movement, sense of movement, position and direction.
What evidence is there that proprioception is important to movement?
-Ian Waterman: patient with a selective large fibre sensory neuronopathy. No sensory feed-back from muscle, skin or joint from below the neck. Has relatively uncoordinated movements
Describe how discharge frequency of receptors may be related to proprioception
-Slowly and rapidly adapting receptors exist in joint capsule and ligaments
- 4 types:
o 1- Ruffini (SA)
o 2- Paciniform (RA)
o 3- Golgi (SA)
o 4- Free nerve (SA)
- RA joint receptors can signal occurrence and speed of movement: discharge rate of single Ruffini join afferent in response to movement in different directions. Can also signal contact
-SA joint receptors produce a discharge related to joint position (different discharge for different position. Signal maintained contact.
-These look to be providing sensory information on position and velocity of movement which is of importance in proprioception
How does information from spindles, joints etc… work with proprioception?
-Can only really be observed in human studies.
-Joint receptors
o Joint replacement operations or blockage of articular afferents with local anaesthetics- moderate loss of position sense
o Electrical stimulation of some single joint afferents evokes sensations of pressure, stress or joint movement
-Cutaneous Receptors
o Electrical stimulation of a small proportion of SAII afferents during microneurography, evokes a sensation of joint movement: others only tactile sensation.
-Muscle Spindle receptors
o Tendon pulling experiments: pulling of tendons exposed conscious humans to stretch muscle without producing movement- evokes some sense of movement
o Effects of muscle vibration (proximal joints)
Think their arms are at the same position (moved)
Describe the Anatomy of the larynx including cartilages, membranes and ligaments.
- Organ located in the anterior of the neck
- Structure is primarily cartiligenous and is held together by a series of membranes and ligaments. Its structure is mainly that of a cartilage skeleton.
- The larynx is suspended in the anterior portion of the neck by the hyoid bone (a small floating bone consisting of a body and 2 lesser and greater horns). It is suspended by the thyrohyoid membrane
- It opens superiorly to the lower segment of the pharynx and inferiorly to the trachea
- It is covered anteriorly by the infrahyoid muscles and laterally by the lobes of the thyroid gland.
- It consists of the supraglottis in which the the epiglottis is located (a leaf shaped covering which acts like a valve preventing food enetering the airways). It ends at the vestibular folds (false vocal folds)
- The glottis which houses the vocal cords. The openeing between the vocal folds is known as the rema glottis
- ## The subglottis is from the inferior border of the glottis to the inferior border of the cricoid cartilage.
Describe the musculature of the larynx in terms of innervation and movement: Extrinsic muscles
Suprahyoid and Infrahyoid
- suprahyoid and stylopharyngeus lift larynx while infrahyoid depresses
Summarise the main cartilages of the larynx
Unpaired Thyroid cartilage - form laryngeal prominance Cricoid cartilage Epiglottis Paired Arytenoid - attachment of vocal ligament Corniculate - articulate with arytenoid Cuniform - strengthens ary-epiglottic folds
