ELAINE N. MARIEB EIGHTH EDITION 8 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings PowerPoint ® Lecture Slide Presentation by Jerry L. Cook, Sam Houston University ESSENTIALS OF HUMAN ANATOMY & PHYSIOLOGY PART A Special Senses

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Senses  General senses of touch (temp, pressure, pain)  Special senses  Smell  Taste  Hearing  Equilibrium  Sight: 70% of all sensory receptors are in the eyes  Each eye has over a million nerve fibers  Well protected: bony orbit, fat cushion

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye  Eyelids  Eyelashes  Meibomian glands: – modified sebacious oily lubricates eye  Ciliary glands: sweat between eyelashes Figure 8.1b

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye  Conjunctiva  Membrane that lines the eyelids  Connects to the surface of the eye  Secretes mucus to lubricate the eye Pink Eye = Conjunctivitis - Infection of the conjunctiva

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Lacrimal Apparatus  Lacrimal gland – produces lacrimal fluid (TEARS)  Lacrimal canals – drains tears from eyes  Lacrimal sac – collects tears toward nasal cavity  Nasolacrimal duct – empties lacrimal fluid into the nasal cavity Figure 8.1a

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Function of the Lacrimal Apparatus  Properties of lacrimal fluid  Dilute salt solution (tears)  Contains antibodies and lysozyme  Protects, moistens, and lubricates the eye  Empties into the nasal cavity

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Extrinsic Eye Muscles  Muscles attach to the outer surface of the eye  Produce eye movements Figure 8.2

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye  The wall is composed of 3 tunics (layers)  Fibrous tunic: outside layer - Sclera (white part of eye) - Cornea (transparent)  Choroid: middle - Iris (colored) - Pupil (hole)  Sensory tunic: inside layer - Retina Figure 8.3a

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Sensory Tunic (Retina) Retina  Contains receptor cells (photoreceptors)  Rods : allow you to see black & white  Cones: allow you to see color  Signals pass from photoreceptors in retina to the brain for processing through the optic nerve

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Neurons of the Retina Figure 8.4 -Fovea Centralis: area of the retina with only cones (color) - Optic Disk = blind spot, no photoreceptors - Color blindness: results from a lack of one cone type. More common in Males.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Internal Eye  Lens: Biconvex crystal-like structure. Held by a ligament attached to ciliary body  Aqueous Humor: fluid infront of lens  Vitreous Humor: fluid in back of lense Figure 8.3a

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Images Formed on the Retina Figure 8.10

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of the Ear  Houses two senses  Hearing  Equilibrium (balance)  Ear is divided into 3 areas:  Outer (external) ear  Middle ear  Inner ear Figure 8.12

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Ear External ear: -Pinna (auricle) -Auditory canal (cerumen = wax) Middle ear: Tympanic Cavity -Malleus (hammer) -Incus (anvil) - Stapes (stirrip) Figure 8.12

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Middle Ear or Tympanic Cavity  Tympanic membrane – Ear Drum covers the auditory canal  Pharyngeotympanic auditory tube connects middle ear &throat (yawn to equalize pressure)

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Inner Ear or Bony Labrynth Inner Ear or Bony Labrynth:  A maze of bony chambers within the temporal bone  Cochlea  Vestibule  Semicircular canals  Balance & hearinga Static & Dynamic Equilibrium Figure 8.12

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Mechanisms of Hearing Figure 8.16a–b

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Senses – Taste and Smell  Taste & smell senses complement each other and respond to many of the same stimuli  Olfaction – the sense of smell  The tongue is covered with projections called papillae – that have taste buds  Taste buds: tongue & cheeks  Sweet receptors  Sour receptors  Bitter receptors  Salty receptors

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Tongue and Taste  The tongue is covered with projections called papillae – that have taste buds  Sweet receptors  Sugars  Saccharine  Some amino acids  Sour receptors  Acids  Bitter receptors  Alkaloids  Salty receptors  Metal ions