Blood And Special Senses PDF

10 Blood PowerPoint® Lecture Slide Presentation by Jerry L. Cook, Sam Houston University ESSENTIALS...

10 Blood PowerPoint® Lecture Slide Presentation by Jerry L. Cook, Sam Houston University ESSENTIALS OF HUMAN ANATOMY & PHYSIOLOGY EIGHTH EDITION ELAINE N. MARIEB Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Blood  The only fluid tissue in the human body  Classified as a connective tissue  Living cells = formed elements  Non-living matrix = plasma Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Blood Figure 10.1 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Physical Characteristics of Blood  Color range  Oxygen-rich blood is scarlet red  Oxygen-poor blood is dull red  pH must remain between 7.35–7.45  Blood temperature is slightly higher than body temperature Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Blood Plasma  Composed of approximately 90 percent water  Includes many dissolved substances  Nutrients  Salts (metal ions)  Respiratory gases  Hormones  Proteins  Waste products Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Plasma Proteins  Albumin – regulates osmotic pressure  Clotting proteins – help to stem blood loss when a blood vessel is injured  Antibodies – help protect the body from antigens Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Formed Elements  Erythrocytes = red blood cells  Leukocytes = white blood cells  Platelets = cell fragments Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Photomicrograph of a Blood Smear Figure 10.2 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Characteristics of Formed Elements of the Blood Table 10.2 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Characteristics of Formed Elements of the Blood Table 10.2 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Erythrocytes (Red Blood Cells)  The main function is to carry oxygen  Anatomy of circulating erythrocytes  Biconcave disks  Essentially bags of hemoglobin  Anucleate (no nucleus)  Contain very few organelles  Outnumber white blood cells 1000:1 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hemoglobin  Iron-containing protein  Binds strongly, but reversibly, to oxygen  Each hemoglobin molecule has four oxygen binding sites  Each erythrocyte has 250 million hemoglobin molecules Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Leukocytes (White Blood Cells)  Crucial in the body’s defense against disease  These are complete cells, with a nucleus and organelles  Able to move into and out of blood vessels (diapedesis)  Can move by ameboid motion  Can respond to chemicals released by damaged tissues Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Leukocyte Levels in the Blood  Normal levels are between 4,000 and 11,000 cells per millimeter  Abnormal leukocyte levels  Leukocytosis  Above 11,000 leukocytes/ml  Generally indicates an infection  Leukopenia  Abnormally low leukocyte level  Commonly caused by certain drugs Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Types of Leukocytes  Granulocytes  Granules in their cytoplasm can be stained  Include neutrophils, eosinophils, and basophils Figure 10.4 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Types of Leukocytes  Agranulocytes  Lack visible cytoplasmic granules  Include lymphocytes and monocytes Figure 10.4 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Granulocytes  Neutrophils  Multilobed nucleus with fine granules  Act as phagocytes at active sites of infection  Eosinophils  Large brick-red cytoplasmic granules  Found in repsonse to allergies and parasitic worms Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Granulocytes  Basophils  Have histamine-containing granules  Initiate inflammation Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Agranulocytes  Lymphocytes  Nucleus fills most of the cell  Play an important role in the immune response  Monocytes  Largest of the white blood cells  Function as macrophages  Important in fighting chronic infection Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Platelets  Derived from ruptured multinucleate cells (megakaryocytes)  Needed for the clotting process  Normal platelet count = 300,000/mm3 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hematopoiesis  Blood cell formation  Occurs in red bone marrow  All blood cells are derived from a common stem cell (hemocytoblast)  Hemocytoblast differentiation  Lymphoid stem cell produces lymphocytes  Myeloid stem cell produces other formed elements Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Fate of Erythrocytes  Unable to divide, grow, or synthesize proteins  Wear out in 100 to 120 days  When worn out, are eliminated by phagocytes in the spleen or liver  Lost cells are replaced by division of hemocytoblasts Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Control of Erythrocyte Production  Rate is controlled by a hormone (erythropoietin)  Kidneys produce most erythropoietin as a response to reduced oxygen levels in the blood  Homeostasis is maintained by negative feedback from blood oxygen levels Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Control of Erythrocyte Production Figure 10.5 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hemostasis  Stoppage of blood flow  Result of a break in a blood vessel  Hemostasis involves three phases  Platelet plug formation  Vascular spasms  Coagulation Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Platelet Plug Formation  Collagen fibers are exposed by a break in a blood vessel  Platelets become “sticky” and cling to fibers  Anchored platelets release chemicals to attract more platelets  Platelets pile up to form a platelet plug Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Vascular Spasms  Anchored platelets release serotonin  Serotonin causes blood vessel muscles to spasm  Spasms narrow the blood vessel, decreasing blood loss Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Coagulation  Injured tissues release thromboplastin  PF3 (a phospholipid) interacts with thromboplastin, blood protein clotting factors, and calcium ions to trigger a clotting cascade  Prothrombin activator converts prothrombin to thrombin (an enzyme) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Coagulation  Thrombin joins fibrinogen proteins into hair- like fibrin  Fibrin forms a meshwork (the basis for a clot) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Blood Clotting  Blood usually clots within 3 to 6 minutes  The clot remains as endothelium regenerates  The clot is broken down after tissue repair Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Fibrin Clot Figure 10.7 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Undesirable Clotting  Thrombus  A clot in an unbroken blood vessel  Can be deadly in areas like the heart  Embolus  A thrombus that breaks away and floats freely in the bloodstream  Can later clog vessels in critical areas such as the brain Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Bleeding Disorders  Thrombocytopenia  Platelet deficiency  Even normal movements can cause bleeding from small blood vessels that require platelets for clotting  Hemophilia  Hereditary bleeding disorder  Normal clotting factors are missing Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Blood Groups and Transfusions  Large losses of blood have serious consequences  Loss of 15 to 30 percent causes weakness  Loss of over 30 percent causes shock, which can be fatal  Transfusions are the only way to replace blood quickly  Transfused blood must be of the same blood group Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Human Blood Groups  Blood contains genetically determined proteins  A foreign protein (antigen) may be attacked by the immune system  Blood is “typed” by using antibodies that will cause blood with certain proteins to clump (agglutination) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Human Blood Groups  There are over 30 common red blood cell antigens  The most vigorous transfusion reactions are caused by ABO and Rh blood group antigens Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings ABO Blood Groups  Based on the presence or absence of two antigens  Type A  Type B  The lack of these antigens is called type O Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings ABO Blood Groups  The presence of both A and B is called type AB  The presence of either A or B is called types A and B, respectively Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Rh Blood Groups  Named because of the presence or absence of one of eight Rh antigens (agglutinogen D)  Most Americans are Rh+  Problems can occur in mixing Rh+ blood into a body with Rh– blood Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Rh Dangers During Pregnancy  Danger is only when the mother is Rh– and the father is Rh+, and the child inherits the Rh+ factor Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Rh Dangers During Pregnancy  The mismatch of an Rh– mother carrying an Rh+ baby can cause problems for the unborn child  The first pregnancy usually proceeds without problems  The immune system is sensitized after the first pregnancy  In a second pregnancy, the mother’s immune system produces antibodies to attack the Rh+ blood (hemolytic disease of the newborn) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Blood Typing  Blood samples are mixed with anti-A and anti-B serum  Coagulation or no coagulation leads to determining blood type  Typing for ABO and Rh factors is done in the same manner  Cross matching – testing for agglutination of donor RBCs by the recipient’s serum, and vice versa Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Blood Typing Figure 10.8 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Developmental Aspects of Blood  Sites of blood cell formation  The fetal liver and spleen are early sites of blood cell formation  Bone marrow takes over hematopoiesis by the seventh month  Fetal hemoglobin differs from hemoglobin produced after birth Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings  Essentials of Human Anatomy & Physiology Seventh Edition Elaine N. Marieb Chapter 8 Special Senses Slides 8.1 – 8.19 Lecture Slides in PowerPoint by Jerry L. Cook and Melissa Scott This presentation contains Copyright © 2003 copyright Pearson Education, protected Inc. publishing as Benjamin Cummings materials The Senses  General senses of touch (tactile)  Temperature- thermoreceptors (heat)  Pressure- mechanoreceptors (movement)  Pain- mechanoreceptors  Special senses  Smell- chemoreceptors (chemicals)  Taste- chemoreceptors  Sight- photoreceptors (light)  Hearing- mechanoreceptors  Equilibrium- (balance) mechanoreceptors The Eye and Vision  70 percent of all sensory receptors are in the eyes  Each eye has over a million nerve fibers  Protection for the eye  Most of the eye is enclosed in a bony orbit made up of the lacrimal (medial), ethmoid (posterior), sphenoid (lateral), frontal (superior), and zygomatic and maxilla (inferior)  A cushion of fat surrounds most of the eye  Accessory Structures of the Eye  Eyelids- brush particles out of eye or cover eye  Eyelashes- trap particles and keep them out of the eye  Accessory Structures of the Eye  Ciliary glands – modified sweat glands between the eyelashes- secrete acidic sweat to kill bacteria, lubricate eyelashes  Accessory Structures of the Eye  Conjunctiva  Membrane that lines the eyelids  Connects to the surface of the eye- forms a seal  Secretes mucus to lubricate the eye http://neuromedia.neurobio.ucla.edu/campbell/eyeandear/wp_images/175_conjunctiva.gif  CONJUNCTIVITIS - Inflammation of the conjunctiva - Caused by bacterial or viral infection - Highly contagious http://www.healthseva.com/images/eye/conjunctivitis.jpg  Accessory Structures of the Eye  Lacrimal apparatus  Lacrimal gland – produces lacrimal fluid  Lacrimal canals – drains lacrimal fluid from eyes Accessory Structures of the Eye  Lacrimal sac – provides passage of lacrimal fluid towards nasal cavity Accessory Structures of the Eye  Nasolacrimal duct – empties lacrimal fluid into the nasal cavity Function of the Lacrimal Apparatus  Properties of lacrimal fluid  Dilute salt solution (tears)  Contains antibodies (fight antigens- foreign substance) and lysozyme (enzyme that destroys bacteria)  Protects, moistens, and lubricates the eye  Empties into the nasal cavity Extrinsic Eye Muscles  Muscles attach to the outer surface of the eye  Produce eye movements When Extrinsic Eye Muscles Contract  Superior oblique- eyes look out and down  Superior rectus- eyes looks up  Lateral rectus- eyes look outward  Medial rectus- eyes look inward  Inferior rectus- eyes looks down  Inferior oblique- eyes look in and up http://www.esg.montana.edu/esg/kla/ta/eyemusc.jpg Structure of the Eye  The wall is composed of three tunics  Fibrous tunic – outside layer  Choroid – middle layer  Sensory tunic – inside layer The Fibrous Tunic  Sclera  White connective tissue layer  Seen anteriorly as the “white of the eye”  Semi-transparent The Fibrous Tunic  Cornea  Transparent, central anterior portion  Allows for light to pass through (refracts, or bends, light slightly)  Repairs itself easily  The only human tissue that can be transplanted without fear of rejection http://www.phys.ufl.edu/~avery/course/3400/vision/eye_photo.jpg Choroid Layer  Blood-rich nutritive tunic  Pigment prevents light from scattering (opaque- blocks light from getting in, has melanin) Choroid Layer  Modified interiorly into two structures  Cilliary body – smooth muscle (contracts to adjust the shape of the lens)  Iris- pigmented layer that gives eye color (contracts to adjust the size of the pupil- regulates entry of light into the eye)  Pupil – rounded opening in the iris Sensory Tunic (Retina)  Contains receptor cells (photoreceptors)  Rods  Cones  Signals leave the retina toward the brain through the optic nerve Sensory Tunic (Retina)  Signals pass from photoreceptors via a two-neuron chain  Bipolar neurons and Ganglion cells http://www.uams.edu/jei/patients/retina_services/images/retina.jpg  VISUAL PIGMENTS Rhodopsin- visual purple, in high concentration in RODS -Composed of opsin and retinal (a derivative of vitamin A) proteins -When light hits the protein it “bleaches”- turns yellow and then colorless. It straightens out and breaks down into opsin and retinal. There are three different other opsins beside rhodopsin, with absorption for yellowish-green (photopsin I), green (photopsin II), and bluish-violet (photopsin III) light. Neurons of the Retina and Vision  Rods  Most are found towards the edges of the retina  Allow dim light vision and peripheral vision (more sensitive to light, do not respond in bright light)  Perception is all in gray tones  ROD CELLS http://webvision.med.utah.edu/imageswv/rod-GC.jpeg http://www.webvision.med.utah.edu/imageswv/PKCrodb.jpeg Neurons of the Retina and Vision  Cones  Allow for detailed color vision  Densest in the center of the retina  Fovea centralis – area of the retina with only cones  Respond best in bright light  No photoreceptor cells are at the optic disk, or blind spot http://blc1.kilgore.cc.tx.us/kcap2/images/retina%20100x%20b%20fireworks.jpg http://www.yorku.ca/eye/rod-cone.gif http://www.secretbeyondmatter.com/ourbrains/theworldinourbrains_files/11-1.jpg  Cone Sensitivity  There are three types of cones  Different cones are sensitive to different wavelengths - red- long - green- medium - blue- short  Color blindness is the result of lack of one or more cone type  How do we see colors? To see any color, the brain must compare the input from different kinds of cone cells—and then make many other comparisons as well. The lightning-fast work of judging a color begins in the retina, which has three layers of cells. Signals from the red and green cones in the first layer are compared by specialized red- green "opponent" cells in the second layer. These opponent cells compute the balance between red and green light coming from a particular part of the visual field. Other opponent cells then compare signals from blue cones with the combined signals from red and green cones.  COLORBLINDNESS - An inherited trait that Comes from a lack of one is transferred on the or more types of color sex chromosomes (23rd receptors. pair)- sex-linked trait Most are green or red or - Occurs more often in both and that is due to a males lack of red receptors. - Can not be cured or Another possibility is to corrected have the color receptors missing entirely, which would result in black and white vision.  COLORBLINDNESS TEST PLATES http://www.geocities.com/Heartland/8833/coloreye.html Lens  Biconvex crystal-like structure  Held in place by a suspensory ligament attached to the ciliary body  Refracts light greatly Internal Eye Chamber Fluids  Aqueous humor Refracts light  Watery fluid found in slightly chamber between the lens and cornea  Similar to blood plasma  Helps maintain intraocular pressure  Provides nutrients for the lens and cornea  Reabsorbed into venous blood through the canal of Schlemm  Internal Eye Chamber Fluids  Vitreous humor Refracts light slightly  Gel-like substance behind the lens Holds lens and  Keeps the eye from collapsing retina in place  Lasts a lifetime and is not replaced http://faculty.washington.edu/kepeter/119/images/eye3.jpg  Lens Accommodation  Light must be focused to a point on the retina for optimal vision  The eye is set for distance vision (over 20 ft away)  20/20 vision- at 20 feet, you see what a normal eye would see at 20 feet (20/100- at 20, normal person would see at 100)  The lens must change shape to focus for closer objects  MYOPIA Nearsightedness, or myopia is the difficulty of seeing objects at a distance. Myopia occurs when the eyeball is slightly longer than usual from front to back. This causes light rays to focus at a point in front of the retina, rather than directly on its surface. Concave lenses are used to correct the problem.  HYPEROPIA Hyperopia, or farsightedness, is when light entering the eye focuses behind the retina. Hyperoptic eyes are shorter than normal. Hyperopia is treated using a convex lens. http://web.mountain.net/~topeye/images/hyperopia.jpg Images Formed on the Retina If the image is focused at the spot where the optic disk is located, nothing will be seen. This is known as the blind spot. There are no photoreceptors there, as nerves and blood vessels pass through this point. Visual Pathway  Photoreceptors of the retina  Optic nerve  Optic nerve crosses at the optic chiasma Visual Pathway  Optic tracts  Thalamus (axons form optic radiation)  Visual cortex of the occipital lobe Eye Reflexes  Internal muscles are controlled by the autonomic nervous system  Bright light causes pupils to constrict through action of radial (iris) and ciliary muscles  Viewing close objects causes accommodation  External muscles control eye movement to follow objects- voluntary, controlled at the frontal eye field  Viewing close objects causes The Ear  Houses two senses  Hearing (interpreted in the auditory cortex of the temporal lobe)  Equilibrium (balance) (interpreted in the cerebellum)  Receptors are mechanoreceptors  Different organs house receptors for each sense  Anatomy of the Ear  The ear is divided into three areas  Outer (external) ear  Middle ear  Inner ear  (Add C. “INNER EAR” to notes)  The External Ear  Involved in hearing only  Structures of the external ear  Pinna (auricle)- collects sound  External auditory canal- channels sound inward The External Auditory Canal  Narrow chamber in the temporal bone- through the external auditory meatus  Lined with skin  Ceruminous (wax) glands are present  Ends at the tympanic membrane (eardrum) The Middle Ear or Tympanic Cavity  Air-filled cavity within the temporal bone  Only involved in the sense of hearing The Middle Ear or Tympanic Cavity  Two tubes are associated with the inner ear  The opening from the auditory canal is covered by the tympanic membrane (eardrum)  The auditory tube connecting the middle ear with the throat (also know as the eustacian tube)  Allows for equalizing pressure during yawning or swallowing  This tube is otherwise collapsed Bones of the Tympanic Cavity  Three bones span the cavity  Malleus (hammer)  Incus (anvil)  Stapes (stirrip) http://medicine.wustl.edu/~oto/bbears/images/ossic.jpg http://www.ghorayeb.com/files/STAPES_on_a_Penny_375_SQ.jpg Bones of the Tympanic Cavity  Vibrations from eardrum move the malleus  These bones transfer sound to the inner ear  Inner Ear or Bony Labyrinth  Also known as osseous labyrinth- twisted bony tubes  Includes sense organs for hearing and balance  Filled with perilymph  Inner Ear or Bony Labyrinth http://www.neurophys.wisc.edu/h&b/auditory/animation/animationmain.html Vibrations of the stapes push and pull on the membranous oval window, moving the perilymph through the cochlea. The round window is a membrane at the opposite end to relieve pressure.  Inner Ear or Bony Labryinth  A maze of bony chambers within the temporal bone  Cochlea  Upper chamber is the scala vestibuli  Lower chamber is the scala tympani  Vestibule  Semicircular canals Organ of Corti  Located within the cochlea  Receptors = hair cells on the basilar membrane Scala vestibuli Scala tympani Organ of Corti  Gel-like tectorial membrane is capable of bending hair cells (endolymph in the membranous labyrinth of the cochlear duct flows over it and pushes on the membrane) Scala vestibuli Scala tympani  Organs of Hearing  Organ of Corti  Cochlear nerve attached to hair cells transmits nerve impulses to auditory cortex on temporal lobe Scala vestibuli Scala tympani  Mechanisms of Hearing  Vibrations from sound waves move tectorial membrane (pass through the endolymph fluid filling the membranous labyrinth in the cochlear duct)  Hair cells are bent by the membrane  Mechanisms of Hearing  An action potential starts in the cochlear nerve  The signal is transmitted to the midbrain (for auditory reflexes and then directed to the auditory cortex of the temporal lobe) Mechanisms of Hearing Continued stimulation can lead to adaptation (over stimulation to the brain makes it stop interpreting the sounds) Organs of Equilibrium  Receptor cells are in two structures  Vestibule  Semicircular canals Organs of Equilibrium  Equilibrium has two functional parts  Static equilibrium- in the vestibule  Dynamic equilibrium- in the semicircular canals Static Equilibrium  Maculae – receptors in the vestibule  Report on the position of the head  Send information via the vestibular nerve Static Equilibrium  Anatomy of the maculae  Hair cells are embedded in the otolithic membrane  Otoliths (tiny stones) float in a gel around the hair cells Function of Maculae Movements cause otoliths to bend the hair cells (gravity moves the “rocks” over and pulls the hairs) http://neuromedia.neurobio.ucla.edu/campbell/eyeandear/wp_images/177_macula_HP.gif  Dynamic Equilibrium  Whole structure is the ampulla  Crista ampullaris – receptors in the semicircular canals  Tuft of hair cells  Cupula (gelatinous cap) covers the hair cells  Dynamic Equilibrium  Action of angular head movements  The cupula stimulates the hair cells  Movement of endolymph pushes the cupula over and pulls the hairs  An impulse is sent via the vestibular nerve to the cerebellum DYNAMIC EQUILIBRIUM STRUCTURES http://www.faculty.une.edu/com/abell/histo/CristaAmp.jpg http://neuromedia.neurobio.ucla.edu/campbell/eyeandear/wp_images/177_macula_crista.gif Chemical Senses – Taste and Smell  Both senses use chemoreceptors  Stimulated by chemicals in solution  Taste has four types of receptors  Smell can differentiate a large range of chemicals  Both senses complement each other and respond to many of the same stimuli  Olfaction – The Sense of Smell  Olfactory receptors are in the roof of the nasal cavity  Neurons with long cilia  Chemicals must be dissolved in mucus for detection Olfaction – The Sense of Smell  Impulses are transmitted via the olfactory nerve  Interpretation of smells is made in the cortex (olfactory area of temporal lobe) http://asb.aecom.yu.edu/histology/labs/images/slides/A74_OlfactoryEpith_40X.jpg The Sense of Taste  Taste buds house the receptor organs  Location of taste buds  Most are on the tongue  Soft palate  Cheeks  The Tongue and Taste  The tongue is covered with projections called papillae  Filiform papillae – sharp with no taste buds  Fungifiorm papillae – rounded with taste buds  Circumvallate papillae – large papillae with taste buds  Taste buds are found on the sides of papillae http://neuromedia.neurobio.ucla.edu/campbell/oral_cavity/wp_images/96_fungiform.gif http://www.esg.montana.edu/esg/kla/ta/vallate.jpg  Structure of Taste Buds  Gustatory cells are the receptors  Have gustatory hairs (long microvilli)  Hairs are stimulated by chemicals dissolved in saliva  Structure of Taste Buds  Impulses are carried to the gustatory complex (pareital lobe) by several cranial nerves because taste buds are found in different areas  Facial nerve  Glossopharyngeal nerve  Vagus nerve http://www.biosci.ohiou.edu/introbioslab/Bios171/images/lab6/Tastebuds.JPG Taste Sensations  Sweet receptors  Sugars  Saccharine  Some amino acids  Sour receptors  Acids  Bitter receptors  Alkaloids  Salty receptors  Metal ions  Umami  Glutamate, aspartate (MSG, meats) http://instruct1.cit.cornell.edu/courses/psych431/student2000/mle6/tonguebig.gif Developmental Aspects of the Special Senses  Formed early in embryonic development  Eyes are outgrowths of the brain  All special senses are functional at birth