صدق الله العظيم الاسراء اية 58 Physiology of Special senses, Abdelaziz Hussein 1

By Dr. Abdel Aziz M. Hussein Lecturer of Medical Physiology Physiology of Special senses, Abdelaziz Hussein 2

The special senses are the senses that have specialized organs devoted to them; Taste (Tongue) Hearing (Ear) Smell (Nose) Vision (Eye) Equilibrium (Inner Ear) Physiology of Special senses, Abdelaziz Hussein 3

sensory receptors Special sensory receptors 1.Localized – confined to the head region 2.Receptors are not free endings of sensory neurons 3.Special receptor cells Physiology of Special senses, Abdelaziz Hussein 4

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6 Vision is a complex process through which an image of the external environment is formed on the retina of the eye, and then conducted as a nerve impulse to the brain where it is interpreted and recognized Physiology of Special senses, Abdelaziz Hussein

1. Informing the nervous system about the external environment 3. Postural reflexes and equilibrium 2. Learning and education 7

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The eye is the organ of vision which consists of 2 parts; 1.Eyeball 2.Extraocular accessory structure Eyeball Lacrimal Gland Eyelid Lacrimal drainage system Physiology of Special senses, Abdelaziz Hussein 9

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Physiology of Special senses, Abdelaziz Hussein 11 Conjunctiva Cornea Sclera Iris Ciliary Body Choroid Pupil Retina

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1.Eyelids. 2.Conjunctiva. 3.Lacrimal apparatus. 4.Extraocular muscles. Physiology of Special senses, Abdelaziz Hussein 13

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Lower Eyelid Upper Eyelid Medial Canthus Lateral Canthus Eyelashes Palpebral Fissure Physiology of Special senses, Abdelaziz Hussein 15

Lower eyelid Skin Conjunctiva Eyelashes Meibomain gland Orbicularis Oculi ms Physiology of Special senses, Abdelaziz Hussein 16

Orbicularis oculi muscle supplied by the facial nerve helps closure of the eyelids Levator palpebrae superioris supplied by oculomotor nerve helps in elevation of the upper eyelid Muller's muscle supplied by sympathetic fibres widens the palpebral fissure Levator Palpebrae superioris Orbicularis Oculi Physiology of Special senses, Abdelaziz Hussein 17

3. Reflex blinking 1.Voluntary blinking 2.Spontaneous blinking: (Rhythmic blinking) Physiology of Special senses, Abdelaziz Hussein 18

1. Protect them from excessive illumination2. Protect the eyes from the foreign bodies 3. Renewal of the tear fluid from the lacrimal glands Physiology of Special senses, Abdelaziz Hussein 19

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Palpebral conjunctiva Bulbar conjunctiva Fornix Physiology of Special senses, Abdelaziz Hussein 21

help free movement of the eyeball Physiology of Special senses, Abdelaziz Hussein 22

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Lacrimal Gland Lacrimal Puncti Lacrimal Canaliculus Nasolacrimal sac Nasolacrimal duct Inferior nasal meatus Physiology of Special senses, Abdelaziz Hussein 24

Unconditioned reflex Irritation of the conjunctiva or the nasal mucosa Conditioned reflexes psychic acts & emotions Physiology of Special senses, Abdelaziz Hussein 25

Irritation of Conjunctiva Trigeminal Nerve Facial Nerve Lacrimal Center Physiology of Special senses, Abdelaziz Hussein 26

keeps the cornea & conjunctiva moistantibacterial actionforms the precorneal tear film Physiology of Special senses, Abdelaziz Hussein 27

Precorneal tear film Deep mucous layer Superficial oily layer Middle tear layer Physiology of Special senses, Abdelaziz Hussein 28

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Medial long. bundle Physiology of Special senses, Abdelaziz Hussein 30

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About the lacrimal apparatus, all the followings are true except; 1.The lacrimal punctum, lacrimal canaliculi, lacrimal sac and nasolacrimal duct constitute the excretory lacrimal system. 2.Lacrimal fluid is an alkaline hypertonic solution of sodium chloride. 3.The refractive index of tears and aqueous humour is Tear has antibacterial action due to the presence of lysosomal enzymes. Physiology of Special senses, Abdelaziz Hussein 34

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