Sense Organs
Objectives
At the end of this lecture, student will be able to
• Describe the structural components of eye ball
• Explain the accessory structures of eye ball
• Distinguish between the structural components and the
accessory structures of eye ball
• Describe the interior of the eye ball
• Explain image formation
• Explain the physiology of vision
• Distinguish the changes occurring during light and dark
adaptation
• Explain the processing of visual signals in retina
• Describe the anatomy of ear
• Identify the receptor organs for equilibrium
• Describe the function of receptor organs for equilibrium
• Describe the auditory pathway
• Explain the major events in the physiology of hearing
• Describe the anatomy of olfactory receptor
• Explain the physiology of olfaction and olfactory
transduction
• Describe the anatomy of taste bud and papillae
• Explain the physiology of gustation and gustatory pathway
• Describe the layers of the epidermis and the cells that
compose them
• Describe various accessory structures of the skin
• Distinguish between the accessory structures and the main
components of skin
• Explain the functions of skin
Content
• Eye ball
– Structural Component
– Accessory Structures
• Interior of the eye ball
• Image formation
• Physiology of vision
• Light and dark adaptation
• Anatomy of Ear
• Auditory Pathway
• Physiology of hearing
• Anatomy of olfactory receptor
• Physiology of olfaction and olfactory receptor
• Anatomy of taste bud and papillae
• Physiology of gustation and gustatory pathway
• Skin
– Layers of epidermis
– Accessory structures
– Function
Summary
• Eye is the organ of the sense of sight
• Eye is situated in the orbital cavity supplied by optic
nerve
• Accessory structure of eye ball – eyelids, Eyelashes,
Eyebrows, Lacrimal apparatus, extrinsic eye muscles
• Eyelashes & eyebrows protects the eye ball
• Lacrimal apparatus produces and drains lacrimal fluid or
tears
• Extrinsic eye muscle moving the eye in almost any
direction
• Wall of the eyeball consists of – fibrous tunic (sclera
and cornea), vascular tunic (choroid, ciliary body, and iris), and retina
• Lens helps focus images on the retina to facilitate clear
vision
• Lens divides the interior of the eyeball into anterior
cavity and the vitreous chamber
• Anterior cavity consists of anterior and posterior chamber
• Image formation involves – refraction of light,
accommodation and convergence
• Cyclic bleaching and regeneration of photo pigments helps
in vision
• Light adaptation occur when emerging from a dark
surrounding to sunshine
• Dark adaptation occur when entering a dark surrounding
• Visual field of each eye consists of nasal region and
temporal region
• Ear is the organ for hearing
• External (outer) ear – auricle, external auditory canal,
and tympanic membrane (eardrum)
• Middle ear – auditory tube, ossicles, oval window, and
round window
• The internal (inner) ear consists of the bony labyrinth
and membranous labyrinth
• The internal ear contains the spiral organ (organ of
Corti), the organ of hearing
• Hair cells of the spiral organ convert a mechanical
vibration (stimulus) into an electrical signal (receptor potential)
• Static equilibrium is the orientation of the body relative
to the pull of gravity; utricle and saccule are the sense organs of static
equilibrium
• Dynamic equilibrium is the maintenance of body position in
response to rotational acceleration or deceleration; ristae in the semicircular
ducts are the main sense organs of dynamic equilibrium
• Olfactory receptors are responsible for the sense of smell
• Cilia responds to inhaled chemicals; generates potential;
initiates the olfactory response; activates the enzyme adenylate cyclase
• Gustation is a chemical sense
• Five primary tastes – Sour, sweet, bitter, salty, and
umami
• Receptors for sensations of taste are located in the taste
buds
• Tastants binds to receptors; generates potential; release
of neurotransmitter; initiates nerve impulse
• Taste signals pass to the medulla oblongata, thalamus, and
cerebral cortex (parietal lobe)
• Skin is the largest organ of the body in surface area and
weight
• Principal parts of the skin are the epidermis
(superficial) and dermis (deep)
• Types of cells in the epidermis are keratinocytes,
melanocytes, Langerhans cells, and Merkel cells
• Epidermal ridges provide the basis for fingerprints and
footprints
• The color of skin is due to melanin, carotene, and
hemoglobin
• Accessory structures of the skin—hair, skin glands, and
nails—develop from the embryonic epidermis
• Skin functions include body temperature regulation, blood
storage, protection, sensation, excretion and absorption, and synthesis of
vitamin D