Sensory organs

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Information about Sensory organs
Health & Medicine

Published on April 18, 2013

Author: pamelafabie



By: Dr. Pamela Fabie

By: Dr. Pamela Josefina T. Fabie

• A. The Eye and its Appendages • B. Ear and Ear Ossicles

 Elevated by a muscle called Levator Superioris Muscle Nerve supply: facial n. – orbicularis muscle occulomotor n. – levator palpebrae muscle Blood Supply: • arterial supply – superior and inferior palpebral branches of ophthalmic artery • Venous drainage – ophthalmic vein

Superior Plica Conjunctiva semilunarisLateral canthus Lacrimal caruncle in lacrimal lake Inferior lacrimal papilla

1. Lacrimal Gland  located at the superolateral angle of the orbit  Oval in shape  Divided into 2 parts: Superior (orbital portion) and Inferior (Palpebral portion)  Pour tears by means of 8-12 tiny ducts Function of Tears: A. Wash away iritating materials, e.g. dust B. Lyzozyme prevents microbial infection C. Prevents drying of conjunctiva and cornea

2. Lacrimal Ducts  Situated one on each eyelid starting from lacrimal punctum to lacrimal sac 3. Lacrimal Sac  Situated in the lacrimal fossa4. Nasolacrimal Ducts  Downward continuation of the sac  About ¾ inch in length  Drains into the inferior nasal concha

 Likened to a quadrilateral pyramid Each orbit contains the globe of one eye and its appendages

 Approximately 1 inch in diameter  Situated in the anterior parts of the orbit nearer the roof than the floor 3 COATS OF THE EYEBALLFIRST COAT  Sclera – white of the eye; tough fibrous external capsule which encloses the posterior 5/6 of the eyeball  Cornea – anterior transparent and clear portion

SECOND COAT  Choroid – nourishing coat of the eyeball composed manily of blood vessel  Ciliary Body - dangerous area of the eye since the wound here can involve the iris, choroid, retina or the cornea o Ciliary muscle – bundles of smooth muscle; aka the “muscle of accomodation” o Ciliary Processes – about 70 in number; forms the Aqueous Humor.  Iris – aka Uveal Tract; corresponds to the diapragm of the camera and has a central opening called “pupil” which regulate the amount of light that reach the retina

THIRD COAT  Retina– expanded termination of the Optic nerve; considered part of the brain.  Optic Disk – considered as the physiologic blind spot  Macula Lute (yellow spot) – forms a yellowish, circular area that lacks blood vessels  Fovea Centralis – tiny depression at the center; the point of highest visual acuity  Refractive Media – are he Cornea, Aqueous Humor, the Lens and the Vitreous Humor (in order from outside to inside)  Aqueous Humor - clear fluid that occupies the space between the cornea in front and lens behind. It is the Lymph of the eye.  Lens- biconvex, transparent and colorless body found between aqueous humor in front and vitreous humor behind. It has the “Power of Accomodation” due to its elastic nature of change.  Vitreous Humor – soft, gelatinous substance that fills whole of the eyeball behind the lens; supports retina behind

1. Lateral rectus m. – pulls the eye laterally 2. Medial Rectus m. – pulls the eye medially RECTI 3. Superior Rectus m. – pulls the eye superiorly and medially 4. Inferior Rectus m. – pulls the eye inferiorly and laterally 5. Superior Oblique m. – pulls the eye inferiorly andOBLIQUE medially 6. Inferior Oblilque m. – pulls the eye superiorly and laterally 7. Levator Palpebrae superioris m. – raises the upper eyelid

- acute and painfulpyogenic infection ofthe sebacious orMeibomian glands ofthe eylid margin

- Inflammation of theconjunctiva may becaused by irritants suchas smoke, dust, windcold, dry air, micronialinfection or allergicreations

-increased intraocularpressure due todefective drainage ofaqueous fluid throughthe scleral venous sinus(canal of Schlemm)

Opacity of the lens whichmay be degenerative orcongenital, bilateral orunilateral. Opacityinterferes withtransmission of light raysso that vision is impaired.

Inability of eyes to moveso that the same imagefalls on the correspondingparts of the retina in botheyes cause by extraocularmuscle weakness ordefective nerve supply

a. AURICLE b. EXTERNAL (Pinna) AUDITORY MEATUS Its purpose is to collect and convey soundwaves to the tympanic membrane (ear drum).

- a cartilagenous framework covered by skin- Aka “Pinna”- Nerve Supply:• Greater auricular n., auriculo- temporal n., lesser occippital n.- Blood Supply:  Supplied by posterior auricular artery and superficial temporal artery  Venous drainage by superficial temporal vein and external jugular vein

- A canal that extends from concha to tympanic membrane- About 1 inch long- 1st part – cartilagenous; 2nd part - osseuosBlood supply:  Skin of cartilagenous part is by hair follicles, sebaceous and ceruminous glandsNerve Supply:  Auriculo-temporal nerve

o Separates the external and the middle earo It transmits the vibrations of sound waves along the auditory ossicles to the inner earo It bulges into the middle ear, making the outer wall concave

 It is the space in the petrous portion of the temporal, lined by mucuos membrane Contains the OSSICLES (Malleus, Incus, Stapes), which transmit sound vibrations from the eardrum to the internal ear

MIDDEL EAR Anterior wall – presents the Auditory(Eustachain) tube Medial wall – present 3 structures:  Foramen Ovale (fenestra vestibule)  Promontory  Foramen rotundum2 muscles:a. Tensor tympani muscleb. Stapedius muscle – draws stapes backward

 It is situated in the petrous portion of the temporal bone Concerned with sound perception, orientation and balancing Made up of TWO LABYRINTHS BONY LABYRINTH MEMBRANOUS LABYRINTH

- About 3mm thick, hard as ivory.- Consists of: o Cochlea – small shell that makes ½ turns around a central pillar called the “modiolus” o Vestibule – central part, attached to stapes o 3 Bony Semicircular Canals – horseshoe-shaped, contain the membranous semicircular ducts. They have no auditory functions but they provide information about the position of the head in space, contributing to the maintenance of equilibrium and balance

- This lies within the bony labyrinth consisting of sac that contains fluid known as “endolymph”- Separated between the bony walls by a fluid known as “perilymph”- It consists of:  Cochlear Duct – contains the spiral organ of Corti, essential part of the organ of hearing  Utricle and Saccule – situated inside bony vestibule  Semicircular Ducts – smaller in size but have the same shape as the bony canals

Infection bystaphylococcusaureus is the usualcause of thelocalizedinflammation (boils)in the external aud.canal

Inflammation of themiddle ear and may bedue to spread ofmicrobes from the upperrespiratory tract throughthe eustachain tube orfrom the outer earthrough the rupture oftympanic membrane.

There is excessiveendolymph causing Repetitive motion causegeneralized dilation and excessive stimulation of theincreased pressure within semicircular canals & vestibularthe membranous labyrinth. apparatus and result in nauseaWith episodes of vertigo, and vomiting in some peoplenausea, nausea, vomiting, tivertigo, vomiting, tinnitus.nnitus. The deafness of old age due to the degeneration of the sensory cells of the organ of Corti.

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