Sense Organs – Human Anatomy and Physiology B. Pharma 1st Semester

Sense Organs

Sense Organs


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


• 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

Sense Organs







• 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

• 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

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