Physiology of Special Senses By Dr Abdel Aziz

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

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

Special Senses 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

Physiology of Vision Physiology of Special senses, Abdelaziz Hussein 5

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 6

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

The Eye (Organ of Vision) Physiology of Special senses, Abdelaziz Hussein 8

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

The eyeball Physiology of Special senses, Abdelaziz Hussein 10

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

Accessory Structures Physiology of Special senses, Abdelaziz Hussein 12

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

The Eyelids Physiology of Special senses, Abdelaziz Hussein 14

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

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

Muscles of the Eyelids 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

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

Functions of Lid Movements 1. Protect them from excessive illumination 2. Protect the eyes from the foreign bodies 3. Renewal of the tear fluid from the lacrimal glands Physiology of Special senses, Abdelaziz Hussein 19

The Conjunctiva Physiology of Special senses, Abdelaziz Hussein 20

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

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

Lacrimal Apparatus Physiology of Special senses, Abdelaziz Hussein 23

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

Control of lacrimal secretion Unconditi oned reflex • Irritation of the conjunctiva or the nasal mucosa Conditioned reflexes • psychic acts & emotions Physiology of Special senses, Abdelaziz Hussein 25

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

Functions of lacrimal secretion keeps the cornea & conjunctiva moist antibacterial action forms the precorneal tear film Physiology of Special senses, Abdelaziz Hussein 27

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

Extraocular Muscles Physiology of Special senses, Abdelaziz Hussein 29

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

Extraocular Muscles Action Physiology of Special senses, Abdelaziz Hussein 31

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Self Test • 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 1. 33. 4. Tear has antibacterial action due to the presence of lysosomal enzymes. Physiology of Special senses, Abdelaziz Hussein 34

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