Microscopic structure of the sense organs Aleš Hampl December 2019 Sense system It serves to convey stimuli that influence organism from inside and outside Sensitive nerve endings (with simple structure) • Simple sensory endings • Intraepithelial sensory endings • Sensory bodies Complex organs • Photosensitive organ - Eye • Organ of hearing and equilibrium - Ear Photoreceptor organ - Eye Analyzes the form, light intenzity and colour reflected from objects Eye ball (three-layered structure) • tunica externa = fibrosa • tunica media = vasculosa • tunica interna = nervosa Accessory structures • eye lids • conjunctiva • lacrimal apparatus • muscles What do we expect form the eye ? • Ability to sense signals and transfer them to CNS • Ability to focus on objects • Enough strength • Ability to regenerate • Ability to move with a minimal friction Enough strength Eyes sit in the protective environment of the skull, in orbits, surrounded by the fat cussions.. Cornea + Sclera = Tunica externa oculi 1/6 + 5/6 = 6/6 of the surface I I Sclera • average thickness 0.5 mm (thicker in posterior part) • bundles of flat collagen I fibers (intesrsecting in all directions) • few fibroblasts, minimum ground substance • relatively avascular • connected by loose system of collagen fibers with Tenon's capsule -Tenon's space - allows for free movement of the yee • lamina suprachoroidea - connection to choroid (loose connective tissue with melanocytes, fibroblasts and elastic fibers) Enough strength Eyes sit in the protective environment of the skull, in orbits, surrounded by the fat cussions.. Cornea + Sclera = Tunica externa oculi 1/6 + 5/6 = 6/6 of the surface I I Sclera • average thickness 0.5 mm (thicker in posterior part) • bundles of flat collagen I fibers (intesrsecting in all directions) • few fibroblasts, minimum ground substance • relatively avascular • connected by loose system of collagen fibers with Tenon's capsule -Tenon's space - allows for free movement of the yee • lamina suprachoroidea - connection to choroid (loose connective tissue with melanocytes, fibroblasts and elastic fibers) Cornea (transversal section) Corneal epithelium Bowman's membrane stratified + squamous (5-6 layers) nonkeratizing rich in nerve endings surface cells equipped with microvili (protrude into the space with the film of tears) : Lamina limitans anterior thickness about 7 - 12 ^m fine collagen fibers (intersecting in all directions) no cells provides strength Substancia propria corneae = STROMA idaj many layers of collagen fibers (in right angles) flat keratocytes in between the collagen lamellae(fibroblast-like cells) contains mucoid substance rich in chondroitinsulphate properly hydrated KEY to the TRANSPARENCY : Lamina limitans posterior fine collagen fibers fibers are organized to 3D network Descemet's membrane Corneal endothelium simple + squamous active in transport to maintain cornea in a proper state continues on the frontal part of iris (via spongium anguli iridocornealis) Ability to regenerate Limbus - corneoscleral junction The area of transition of the transparent collagen bundles of cornea into the opaque collagen bundles of sc\era. Highly vascularized - feeds ayascu\ar cornea Limbus Sclera Cornea Cornea Terminally \ differentiated cell Limbus Epithelium Stroma LIVBUS : . • • • r «- ->-.-! *'* • r • * • o • ■ * " •< ' _ xlOOO X200 Choroid Enough supply of resources Choroid + Ciliary body + Iris Choroidea Corpus ciliare Iris Tunica media T. vasculosa Ciliary body Choroid = 4-layered structure Lamina suprachoroidea ■ loose connective tissue • rich for pigment cells - melanocytes Lamina vasculosa ■ loose connective tissue • rich for pigment cells - melanocytes ■ contains larger vessels and nerves Choroid Lamina choriocapillaris ■ loose connective tissue * network of small vessels .amina vitrea = L. basal is = Bruch's membrane fibers of collagenu a elastin overall thickness about 3-4 \im links together basal lamina s of Lamina choriocapillaris of choroid and pigmented epithelium of retina •z o 77 Ability to focus on objects Ciliary body - anterior extension of the choroid Stroma of ciliary body • loose connective tissue • contains elastic fibers, vessels and melanocytes • rich for capillaries (chamber fluid) • bundles of smooth muscle fibers (anchored to sclera and protrude to the processes of ciliary body - m. ciliaris) Processes of CB (Processus ciliares) • protrude into posterir chamber • total number of about 70-80 • rich for capilaries (chamber fluid) • covered by two-layered epithelium (from the retina - pars ciliaris retinae) • linked to the lens Capsula fibrae suspensoriae lentis (zonulae) Triangular on crossection Connects to: • lens + posterior chamber (A) • sclera (B) • vitreous body (C) Choroid Pupil----1> Ciliary Ciliary body Iris - 1 Anterior continuation of the choroid. Partially covers the lens. Section through the anterior part of the eye Iris - 2 Epithelium + border layer Posterior chamber Pigmented epithelium Iris = 4-layered structure Layers from outside: Anterior epithelium • continuation of the posterior ep. of the cornea ■ discontinues layer of flat epithelial cells, fibroblasts a melanocytes Anterior border layer • thin layer of connective tissue • rich for pigmented cells - melanocytes ■ decides about eye colour Stroma ■ loose connective tissue ■ large number of radially running vessels • concentrically ordered smooth muscle fibers (=musculus sphincter pupillae) Pars iridica retinae • 2-layered • continues form ciliar body • layer facing the stroma contains smooth muscle fibers (=musculus dilatator pupillae) Lens Capsule + Epithelium + Fibers • 10-20 jim ■ Collagen IV Fibrae suspensorie lentis are anchored to the equator of the lens. Ability to sense signals and transfer them to CNS for processing Retina = Tunica aculi interna - Tunica nervosa Posterior part • photosensitive • multi layered Anterior part • non-photosensitive • two-layered • covers ciliary body and posterior part of the iris Invagination of prosencephalon creaies two-layered optic cup. Outer layer Stratum pigmenti retinae columnar cells basally located nucleus firm connection with lamina vitrea/basalis of choroid zonulae occludentes and adherentes rich for smooth ER (esterification of vit A) rich for melanin granula apical extensions (microvili and sheets) vesicles in apical parts Inner layer Neural retina Neural (optical) retina minimum 15 different types of neurons with tens of interactions (synapses) ( Internal limiting membrane Layer of nerve fibers Ganglion cell layer Internal plexiform layer Internal nuclear layer External plexiform layer layer ^^^DJA'^; V External nuclear External limiting membrane Layer of rods and cones Photoreceptors = Rod and cone cells 1 I. Neurones of the optical path Internal limiting membrane Layer of nerve fibers Ganglion cell layer Internal plexiform layer Internal nuclear layer External plexiform layer External nuclear layer External limiting membrane Layer of rods and cones Photoreceptors = Rod and cone cells 2 I. Neurones of the optical path Other neurons of the optical path 1 Internal limiting membrane Layer of nerve fibers Ganglion cell layer Internal plexiform layer Internal nuclear layer External plexiform layer External nuclear layer External limiting membrane Layer of rods and cones mmmm - -.11 "u v j) t Of

Human retire „Does the retina see the same in all its areas Central x Peripheral vision Macula lutea Retina Choroid Fovea centralis of the macula lutea = the sharpest vision lacula Fovea centralis Cones only Audioreceptor system Vestibulocochlear apparatus Sensing and transfer of sound Sensing static equilibrium Sensing dynamic equilibrium External ear Middle ear Internal ear Internal ear Internal ear External + Middle ear - Organ of hearing Middle ear - fitted in the cavities of temporal bone along with internal ear - osseous labyrinth. Synovial joints JL Elastic cartilage Tympanic membrane Pars ossea: 2-layered vilous cylindrical epithelium Pars cartilaginea: - multilayered -"- • Stratum mucosum • Stratum f ibrosum • Stratum cutaneum Extrenal ear - Auricle Extrenal ear - Auricle - Elastic cartilage Internal ear Bony labyrinth series of cavities petrous portion of temporal bone Vestibulum Cochlea | Semicircular canals Ö Membranous labyrinth series of interconnected tubes and vesicles lined by epithelium positioned in bony lybrinth Utricle Saccule Semicircular ducts Cochlear duct - Subdural space Subarachnoid space Semicircular ducts Internal ear - Organ of hearing £ £ i Ductus cochlearis (Sca\a media) Round window Cochlea • 2,5 turns around modiolus • total length about 35 mm Stapes at C oval window Basilar V Ganglion spirále ' Vestibular t membrane Semicircular ducts Tectorial membrane Modiolus (bony core) • central axis of cochlear duct • contains ganglion spirale cochleae, nervus cochlearis and vessels 7 - 9 mm \ tympani/ ~ _ ✓ Cochlear branch of n.v. Internal ear - Detail of cochlear duct Stria vascularis • vascularized epithelia • responsible for the composition of endolymph? Basilar membrane • between lig. spirále and bony lamina spiralis • supports the cells of organ of Corti • made of fibrils of keratin-like proteins Tectorial membrane • product of the cells of spiral limbus • rich for glycoproteins • přes vrcholky smyslových buněk organ of Corti Ligamentum Spirale > Spiral ganglion Bony lamina spiralis 20 |jm Internal ear - Organ of Corti - 1 Internal ear - Organ of Corti - 2 Secondary receptor cells • hearing hairs - stereocilia • in contact with tectorial membrane • bases wraped by dendrites of bipolar cells of ganglion spirale Outer hair cells • 3-5 rows, ~12 000, no axonema Inner hair cells • 1 row, ~3 500, no axon. Supporting cells Hensen's cells Outer phalangeal cells • support to hair cells, which run through the spaces between ph. Outer pillar of Corti Outer pillar of Corti Inner phalangeal cells • same as inner ph. cells Border cells Hensen's c. Outer tunnel Tectorial membrane Cells of Claudius Spiral ligament Internal spiral tunnel Cochlear Basilar / / I Outer membrane j I pillar Cells ol Boettcher Outer phalangeal c. Inner tunnel Inner pillar Inner phalangeal c. Hair and phalangeal cells Spiral ganglion f/> ,í"V-CO -v ii V ,bone * spiral ganglion (nerve cell bodies of cochlear nerve) Inner ear - Principle of hearing Inner ear - Statokinetic / Vestibular organ Uniform composition of the wall (vessicles and tubes) Thin layer of connective tissue + single-layer squamous/cuboidal epithelium. Unifying concept of the composition of sensing elements (vessicles - maculae; tubes - cristae ampullares) Thickening of the wall with neuroepithelial cells inervated by branches of n. vestibularis. Inner ear - Statokinetic / Vestibular organ - Sensing of static equilibrium (maculae = static spots) Deviation from the gravity force (gravity force of otoliths) max. pressure - max. pull Position of maculae Saccule bottom Utricle lateral wall Kinocilium (no axonema) Terminal plexus of tonof ibrils 25-100 y.m Supporting cells Afferent innervation Stereocilia (microvili) Dendrites of cells gangl. n. vestibuli Hair cells Supporting eel Efferent innervation AW Fibers of n. vestibularis in connective basis of macula Inner ear - Statokinetic / Vestibular organ Sensing of dynamic equilibrium (cristae ampulares) - 3 -Subdural space Subarachnoid space Tympanic membrarv Reaction on acceleration/deceleration (movement of endolymph) Position of cristae amplulares • in ampules of semicircular ducts ridges perpendicular to axis of SDs Hair cells Hair cells Supporting cells Dendrites of cells gangl. n. vestibuli j Cupula Ampula Hair cells Crista bone Membranous labyrinth Development of sense organs - Overall picture Mammary glands Sweat glands Sebaceous glands Embryonic endoderm canal Trachea Lungs Pancreas Wall of respiratory tract / Myocardium Endocardium Pharynx Outflow tract Walls of aortic arches Liver Digestive tract Wall of gut Thyroid Pharyngeal pouches I Middle ear Auditory tube II Tonsils III Thymus Inf. parathyroids IV Sup. parathyroids Post, branchial bodies Stroma of pharyngeal pouch derivatives Sense organs - Reminder - Neural tube Neural tube Intermediate mesoderm Paraxial mesoderm Lateral plate mesoderm Splanchnic Somatic Head Somite Kidney Gonads Sclerotome Myotome Dermatome - I Neural plate « **•.... rpdermal signals s**8'"* y............... : Neural folds • T Neural tube Dorsahľing signals Shh gradient Intermediate mesoderm A* Epidermal ** * ectoderm ^ ••«....•*** Paraxial mesoderm Chordamcsodcrm Somite Notoc horci Epidermis *• crest cells Roof plate Somite Floor plate Notochord Somite Sense organs - Reminder - Neural crest Arise from both dorsal epidermis and neural plate Sense organs - Cranial neural tube + Placodes Forebrain Mesencephalon Prosencephalon Hindbrain Rhombencephalon Central canal Brain after 4 weeks of development Placodespatches of dense culumnar epithelium in the epidermis covering the head - their formation is induced by underlying brain and mesenchymal tissue - develop in week 4 Placode (a) Epibranchial placodes Dorsolateral placodes Otic vesicle Nasal placode Dorsolateral placodes Contribute to: • eye - lens placode • ear - otic placode • nose - nasal placode • sensory ganglia Epibranchial placodes Develop into: • sensory ganglia of cranial nerves (V, VII, IX, X) Sense organs - Eye development 1 Telencephalon Lateral ventricles (first and second) Third ventricje.»»""«» ** Optic cup Mesencephalon Rhombencephalon (e) Central canal Fourth ventricle Future aqueduct of Sylvius Brain after 5 weeks of development Neural plate ectoderm -> prosencephalon (forebrain) eye fields -> -> neural plate growth carries eye field region forward -> -> eye field invaginates forming optic grooves (sulci) Sense organs - Eye development 2 Neuroectoderm Prosencephalon - transversal section - about 30 days Lens placode: the ectoderm invaginates in response to signals from the optic cup underneath. It then pinches off as a lens vesicle. Cells elongate to fill the vesicle and start to synthesize crystallins. Optic cup: forms from the neural tube by invagination. The opening (choroid fissure) closes forming a round optic cup, an extension of the brain. Optic stalk: connection to the brain that is filled with neurons to form the optic nerve. Reciprocal interaction: the lens induces the formation of the optic cup and the cup regulates formation of the lens. Sense organs - Eye development 3 Intraretinal space Neuroectoderm Diencephalon - transversal section - 6 weeks Sense organs - Eye development 4 Lens epithelium ektoderm- Eyelid About 7 weeks Pigmented and neural retina intraretinální prostor Hyaloid artery Optic nerve Undifferentiated mesenchyme Histogenesis of retina ends in 8 month. m. ciliaris proc. ciliares stroma iridis choroid sc\era vitreous Ear development - Inner ear 1 Otic placode Mesenchyme Epidermal ectoderm pharynx 22 days stěna rhombencefala 1. Pharyngeal groove D 30 days Ganglion vest i bulococh leare (contributed by neural crest) Otic vesicle • dorsal part • ventral part Rhombencephalon - transversal section Ear development - Inner ear 2 resoiptton Supeno* scmiorcuta/ duct Later* semicircular dud Elongation Poatcno» SArnofCula' dud ft Cochlear ganglion OečMM Apoptosis Superior ae*norcu1«f dud Ctttt0ň IM otic CApwe Bony f">omt)coc«prta*oo Ectoderm Crnyda- Paruul T*sor>rm nmodemi V ODCtHIkJ. ........... CoctW . * Otic placode-► OK — Oocyst \ mirt \ > \ \ ........../ \ VmtKOw;. Vestibulär r\ .••\".....fl*V»n »♦ »*1 Dorsal part Barchel vn*bbui*f VeslitKjiar ga.">gfcon Ventral part Ear development - Middle ear Pharyngeal arches 1 + 2 E"dt>c dud car«i EndotympMiic duct Pnrnoidiuro 0» »•* Pharyngeal groove \} par cavity Pharyngeal pouch 1 / B AixMory tuDe Ossicles Mesenchyme of neural crest origin (phar. arches 1+2) Embedded in mesenchyme Apoptosis late in pregnancy Tympanic membrane Endoderm Mesoderm Ectoderm Ear development - External ear External auditory meatus - ectoderm Thank you for your attention !