Tongue, Taste Buds and Taste PDF

Tongue, taste buds and taste [Oral & Dental Sciences] Miss H Rogers GDC ILOS 1.1.5 Describe relevant and appropriate dental, oral, craniofacial and general anatomy and explain their application to patient management 1.1.6 Describe relevant and appropriate physiology and explain its application...

Tongue, taste buds and taste [Oral & Dental Sciences] Miss H Rogers GDC ILOS 1.1.5 Describe relevant and appropriate dental, oral, craniofacial and general anatomy and explain their application to patient management 1.1.6 Describe relevant and appropriate physiology and explain its application to patient management Related topics:  Epithelium  Muscles  Floor of the mouth  Regional anatomy  Oral Mucosa Aim To gain an overview of the structure and functions of the tongue, and its variations in appearance Learning Outcomes By the end of this lecture you should be able to: 1. Describe the structures and functions of the tongue and taste buds 2. Describe the muscles of the tongue (intrinsic and extrinsic), including their nerve innovation and blood supply 3. Describe how the sensation of taste is created 4. Recognise the variations in the tongue’s appearance in both health and disease The Tongue: In health 4 Grab a mirror and take a look at your tongue! Look at all the surfaces, consider the shape, colour, texture- how would you describe it?  Tongue- Comes from the Greek Glossus It is a moveable muscular organ, comprising of a root, body and tip (apex). It has a curved dorsal surface and an inferior ventral surface. Functions Qu: What do we use our tongue for - how many uses can you list? Click on the image above to see a video on how our tongue moves Functions How many did you get…  Mastication  Kissing  Taste  Sensitivity  Swallowing  Suckling  Oral Hygiene  Defence  Speech Structures Qu: Which structures of the tongue are you able to label?  Epiglottis Palatine Tonsil Lingual Tonsil Root/Base Sulcus Terminalis (Posterior 1/3) Dorsum/Dorsal surface Lateral border Body Ventral surface (Anterior 2/3) (on underside) Median Lingual Sulcus Lingual Papillae Apex (tip)  Ventral surface Dorsum/Dorsal surface Lateral border Dorsum The dorsum of the tongue is divided into two sections: Anterior two thirds Root/Base (oral/body) Posterior one third (Posterior 1/3) (pharyngeal/base) Body The two parts are separated by: (Anterior 2/3) sulcus terminalis (a triangle-shaped landmark) foramen caecum Ventral Surface This surface is covered during your lecture ‘FOM and Palate’ Can you remember any of the structures? What type of mucosa covers the ventral Deep Lingual Veins Plicae Fimbriate surface? (fimbriated fold) Please refer to the FOM and Lingual Frenum 13 palate lecture for more information on these structures Lateral Border The main features are the ridges along the border made up of foliate papillae Have another look in the mirror Are you able to identify these features on your own tongue? Lingual Papillae 16 There are 4 types of lingual papillae located on the dorsum of the tongue: Filiform Fungiform Circumvallate Foliate Filiform Fungiform Circumvallate Sulcus Terminalis Circumvallate Papillae Foliate Taste Buds 23 Taste buds are barrel-shaped organs and are composed of 30-80 spindle-shaped cells that extend from the basement membrane to the epithelial surface of the lingual papillae. The lingual papillae associated with taste buds: Fungiform Foliate Circumvallate Turnover of taste bud cells is rapid, approximately 10 days.  Within each taste bud there are two types of cell:  Supporting cells  Taste cells Supporting Cells These support the taste bud and are usually located on the outer portion of the taste bud Taste Cells Usually located in the central portion of the taste bud The taste pore is an opening in the most superficial portion of the taste bud Superficial taste receptors make contact with dissolved molecules of food at the taste pore producing a taste sensation Taste cells are also associated with sensory neuron processes in the inferior portion of the taste bud among the cells which receive messages of taste sensation by way of the receptors. The messages are then sent by way of the nerve to the central nervous system where it is identified as a certain type of taste Taste (Gustation) 29 Why do we have taste? Safety Foods that are: Sweet, umami or low salt- indicate nutrient rich foods Bitter, sour or highly salty- indicate potentially toxic or spoiling foods Physiological Taste starts digestion and is closely linked to the other 4 senses… Sight, smell and the sounds of food prepare the body by increasing saliva flow and stimulating gastric juices. When food enters the mouth, touch allows the body to know what type of saliva is most appropriate. In order to be able to experience taste, saliva needs to be present as substances can only be tasted in solution. Remember, the taste receptors in the taste bud make contact with dissolved molecules of food. What does this mean for patients with xerostomia or reduced saliva production? How might people compensate for a lack of taste and how could this have an impact on their oral health? Taste Mapping Muscles of the tongue 33 Divided into 2 groups: Extrinsic muscles (originate outside the tongue and inserted into it) Intrinsic muscles (contained entirely within the tongue) Extrinsic These muscles alter the position of the tongue Genioglossus Hyoglossus Palatoglossus Styloglossus Genioglossus Origin The superior genial tubercle (on the inferior aspect of the mandible) Insertion Into the whole surface of the tongue Action Pulls tongue forward to protrude from the mouth. Whole muscle can depress and form a concavity on its dorsal surface Hyoglossus Origin The hyoid bone Insertion The ventral side of the tongue Action Depresses the tongue and assists in retraction Palatoglossus Lies within the palatoglossal arch (see palate lecture) Origin Small narrow muscle arising from the aponeurosis of the soft palate Insertion Side of the tongue, and blends with the intrinsic muscles Action Lifts up the tongue, closing off the mouth from the pharynx e.g. during swallowing Styloglossus Origin A short muscle originating at the styloid process Insertion Blends with the inferior longitudinal muscle, and the hyoglossus. Action Draws the tongue upwards and backwards  Intrinsic These muscles alter the shape of the tongue Superior Longitudinal Muscle Inferior Longitudinal Muscle Vertical Muscle Transverse Muscle Superior Longitudinal Muscle Origin The sub mucosa of the Superior Longitudinal Mu posterior portion of the tongue Insertion The apex and anterolateral margins of the tongue Action Shortens the tongue Turns the tip and the sides upwards Inferior Longitudinal Muscle Origin Root of the tongue and the hyoid bone Insertion Into the apex of the tongue Action Shortens the tongue Pulls the tip and sides Inferior Longitudinal Muscle downwards Vertical Muscle Origin Root of the tongue and genioglossus muscle Vertical (& Transverse) Muscle Insertion Lingual aponeurosis Action Flattens and broadens the tongue Transverse Muscle Origin Fibres which originate in the median lingual septum Transverse (& Vertical) Muscle Insertion Pass laterally to insert into the side of the tongue Action Narrows and lengthens the tongue This video is a good visual walk through to summarise the extrinsic and intrinsic muscles of the tongue: https://www.youtube.com/watch?v=umNW_PvKsPE Nerve Innervation & Blood Supply 46 Nerve Innervation The tongue has both a sensory nerve supply Posterior 1/3 and a motor nerve supply. Sensory and Taste: Glossopharyngeal Nerve (IX) Anterior 2/3 Motor supply: Sensory: Hypoglossal nerve (XII), except the Palatoglossus which is supplied by the Vagus nerve (X) Lingual nerve Taste: (Trigeminal Nerve V) Chorda Tympani (Facial nerve VII) & Lingual nerve Blood Supply Blood supply reaches the tongue via the Lingual artery (a branch of the external carotid artery) Deep lingual artery External carotid artery Lingual artery Blood Supply The tongue drains principally through the lingual vein Deep lingual veins Lingual vein The Tongue: ‘Abnormal’ appearance 50 Geographic Tongue Benign condition Caused by inflammation of the tongue Smooth irregular red patches and white wavy lines, which may change position Appearance likened to a Further information: map- hence the name Oral Health Foundation ‘geographic’ NORD No treatment, advise to avoid acidic and spicy foods to reduce soreness Glossitis Inflammation causing swelling , redness and Iron deficiency anaemia [full article] changes in the surface Left: before treatment, Right: after treatment texture Can be categorised into acute, chronic, atrophic and median rhomboid Several causes including, Median Rhomboid Glossitis but not limited to: Further information: Anaemia Sharabim, A.F. & Winters, R. Glossitis. [Updated Nov 30 2020]. In: StatPearls Celiac disease [Internet] Trauma Lu, S. (2016) Perception of iron deficiency from oral mucosa alterations that s how a high prevalence of Candida infection. Allergic reaction Piercings According to a poll undertaken by the Oral Health Foundation, tongue piercings are the most popular oral piercing.  How might they impact on oral hygiene?  How might they impact on the integrity of the teeth? Snake Eyes Need help? See a list by Colgate of the risks involved with oral piercings, or an article by dentalcare.com on the implications for dental professionals Venom Black Hairy Tongue Overgrowth of cells creating elongated papillae. Food, bacteria and yeast becomes trapped and causes discolouration. Smoking, antibiotics and radiotherapy can also contribute to the appearance. Treated by cleaning the surface of the tongue with a toothbrush or tongue scraper, and making lifestyle changes. Squamous Cell Carcinoma  Squamous cell carcinomas (SCC) make up 95% of oropharyngeal cancers. [Cancer Research UK]  Most common site (40%) is the tongue, on the posterior lateral border or ventral surface. SCC lesion This will be covered in more detail during your Dental Specialities module in Year 2 Reconstruction of the tongue following removal of SCC Summary- test yourself! 1. Try labelling this tongue diagram again. Compare it to the one you labelled at the start. How does it compare? 2. List the 4 different types of lingual papillae- highlight the ones that contain taste buds. Revision Prep! Use the table below, or create your own, to summarise the muscles of the tongue Muscle Origin Insertion Action Innervation Blood Supply  Additional Resources YouTube Development of the tongue (NB: try not to get overwhelmed by the detail- check out the animations) https://youtu.be/NzLySYOBjRY Sam Webster- Muscles of the tongue (anatomy) https://youtu.be/lATWhP0wJ5c Article InformedHealth.org [Internet]. Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG); 2006-. How does the tongue work? 2011 Dec 19 [Updated 2016 Aug 23]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK279407/  Website KenHub- Muscles and Taste Sensation of the Tongue https://www.kenhub.com/en/library/anatomy/muscles-and-t aste-sensation-of-the-tongue KenHub- Tongue https://www.kenhub.com/en/library/anatomy/tongue References Bath-Balogh, M. & Fehrenbach, M.J. Dental Embryology, Histology, and Anatomy. Elsevier. 2006. Gravina, S. A., Yep, G. L., & Khan, M. (2013). Human biology of taste. Annals of Saudi medicine, 33(3), 217–222. https://doi.org/10.5144/0256-4947.2013.217 KenHub https://www.kenhub.com/