The Senses - Taste and Hearing - AG - Canvas-2

The SensesTaste and Hearing Dr Abhishek Gupta a.gupta@wlv.ac.uk Ext: 2673 Learning objectives • Understand how substances are tasted (the papillae and taste buds). • Name the structural compartments of the ear. • Describe the main components in different compartments of the ear. • Understand how a sound wave is converted into a perceived sound. Contents • Tongue • Taste (Gustation) • Structure of the Ear • Mechanism of Hearing Tongue • Formed of muscle • Attached by its base to hyoid bone • Part of its floor is attached with the throat through a fold, frenulum • Superiorly has papillae (projections) which contain taste receptors • Vallate • Fungiform • Filiform https://mobilephysiotherapyclinic.net/palatoglossus-muscle-2/ Functions: • Chewing (mastication) • Swallowing (deglutition) • Speech • Taste Taste Papillae • Circumvallate papillae • • • • The largest 8-12 Semicircular Near the base of the tongue • Fungiform papillae • Like the heads of mushrooms • Mainly lies at the tip and sides of the tongue • Foliate papillae Taste Buds • Filliform papillae do not bear taste buds • Buds for bitter taste: • Base of the tongue • Buds for sweet and salty taste • Tip of the tongue • Buds for sour taste • Sides of the tongue • Leaf like • 3-4 pairs • Lies on sides of the tongue • Filliform • Minute • Found all over the surface of the tongue https://www.histology.leeds.ac.uk/oral/tongue.php Function of the Ear • Collect sound waves, covert into other vibrations: • First by small bones (the middle ear) • Then by fluid (the inner ear) • Finally covert the fluid vibration into nerve impulses External Ear • The Auricle (Pinna) • Irregular shaped framework • Elastic cartilage covered with skin • Directs sound waves into the External Auditory Meatus • The Lobule • Extends from the lower margin of the auricle • Skin-covered connective tissue • The External Auditory Meatus (canal) • • • • • • • Curved (S-shaped) Approximately 2.5 cm long Figure: External Ear Extend from the Auricle to the Eardrum Lined with Skin, and near its entrance are fine hair and sebaceous glands Also has Ceruminous glands (modified sweat glands) Ceruminous glands secrete cerumen (ear wax) Traps insects and prevents small foreign particles from reaching the Eardrum (Modified from Spence and Mason, 1992) Middle Ear • Small air-filled chamber in the temporal bone • Separated from the External Auditory Meatus (External ear) by the Tympanic membrane • Separated from the Internal air by a bony wall with 2 openings: • Fenestra vestibuli (the oval window) • Fenestra cochleae (the round window) • Another opening connects the middle ear chamber with the Auditory tube, leading to the Nasopharynx • Helps equalise the air pressure in the middle ear with the atmospheric pressure https://www.aboutkidshealth.ca/Article?contentid=833&language=English Middle Ear • The Three Ear Ossicles (middle-ear bones) Malleus- Hammer shaped Incus – Anvil shaped Stapes- Stirrup shaped • Forms a bridge across the middle-ear chamber between the Tympanic membrane and the oval window. • The ossicles picks up vibrations of the tympanic membrane and transmits to the oval window. Internal Ear • Consists of: • Osseous labyrinth (Bony labyrinth)• Hollowed out of the bone; filled with perilymph • Vestibule • Semicircular Canals • Cochlea • Membranous labyrinth• located within the osseous labyrinth, • filled with endolymph Internal Ear • Osseous labyrinth • Filled with perilymph • Low concentration of potassium ions ang high sodium ions • Divided into 3 areas: • Vestibule • A Chamber- medial to the middle-ear chamber • Vibration of the oval window transmitted to the perilymph of the vestibule • Within the vestibule are the 2 enlargements of the membranous labyrinth: • Utricle (Membranous labyrinth) • Saccule (Membranous labyrinth) • Contains receptors that detect position and movements of head (sense of balance). Drawn by Dr Abhishek Gupta Internal Ear • Semicircular canals: • Three semicircular canals (Anterior, Posterior and Lateral) • Contains membranous semicircular ducts • Semicircular ducts contains enlarged Ampulla which contains receptors • Detects movements of the head (equilibrium) • Cochlea: • Associated with hearing ½ • Snail shell like shape spiralling 2 • Divided in three longitudinal tunnels • Scala vestibuli • Cochlear duct (Scala media): Membranous labyrinth of the cochlea, filled with endolymph • Scala tympani • Vestibular membrane • Basilar membrane: The organ of Corti containing the receptors of hearing Drawn by Dr Abhishek Gupta Drawn by Dr Abhishek Gupta Drawn by Dr Abhishek Gupta Structure of the Ear (Spence and Mason, 1992) Mechanism of Hearing Hearing is the process of perceiving sound Sound waves enters the external auditory canal Strike the tympanic membrane and gets converted to vibrations These vibratory movements of the tympanic membrane are transmitted across the middle ear cavity by the ossicles to the oval window of the inner ear. • This causes movements in the perilymph pushing the perilymph along the scale vestibuli, through helicotrema and into the scale tympani. • Sensory cells of the organs of Cort vibrate and when these touch the tectorial membrane, impulse is generated. • This impulse is carried to the brain and translated to hearing. • • • • (Spence and Mason, 1992) Bibliography • Spence, A.P and Mason, E. (1992) Human Anatomy and Physiology. 4th Edition. West Publishing Co. • Totorta, G. and Derrickson, B. (2011) Principles of Anatomy and Physiology. 13th Edition. Wiley & Sons. • Minett, P. and Ginesi, L. (2020) Anatomy and Physiology. 1st Edition. Lantern Publishing Ltd. UK. • Waugh, A. & Grant, A. (2014) Anatomy and Physiology in Health and Illness. 12th Edition. London: Elsevier.