Sense organs : Eyes, ears, tongue, nose and skin are the sense organs of the human body. Their description is given below.
Eyes : Eyes are the organs of sight. All animals use eyes for seeing the objects. In man these are spherical in shape and situated in the orbits. Each eye ball is made up of three concentric layers. The outer layer is called scleroid. Middle layer is called choroid and the inner layer is called retina. Retina is light sensitive layer. Retina contains rods and cones. Rods are sensitive to dim light while cones differentiate colours. These are made of photosensitive cells. A double convex lens is suspended with the cillary body. This lens divides the eye in two parts. The part between lens and cornea contains aqueous humour and the part between lens and retina contains vitreous humour.
Human eye is sensitive to the wave lengths form 380-760 nano meters. Retina is of complex structure. Outer layer is pigmanted layer, inner layer is sensory layer containing rods and cones. Cones are found at yellow spot. Bipolar layer and ganglionic layer is made up of bipolar neurons.
Eye can suffer with strabismus, cataract, glaucoma etc.
Eye can have four defects namely : myopia, hypermetropia, astigmatism and pressbyopia. All these defects can be corrected by suitable lenses.
Ears : Ear is an organ of hearing. It also maintains equillibrium and balance of the body. Ear has pinna (external ear) and middle ear containting tympanic cavity. There are three bones-melleus, incus and stapes. Hearing is concerned with the sacculus and cochlea. These are four parts of membranous labyrinth. These are semicircular canal, utriculus, sacculess and cochlea. Cochlea is the main centre of hearing. Canals mainly are meant for balancing.
Tongue : This is the organ for taste. It contains chemo-receptors. Taste buds are granular in structures on the tongue. There are four kind of taste buds for sweet, saltish, chilly and sour tastes. These are taste receptors.
Nose : This is the organ of smell. In the nasal cavity ethmoturbinals, maxilo turbinals and nasa turbinals bones are present. These bones are covered by the olfactory or schneidarian epithellium. Olfactory cell is a modified neuron that is a receptor for sense of smell.
Skin : Free nerve endings in the dermis are sensory to touch. Tactile organs are also present. These are corpuscles for cold and heat.
The sense organs are grouped into three types :
External receptors : These are situated on the outer surface of the body.
Internal receptors : These are situated with in the digestive system.
Proprio-receptors : These are situated internally but other than digestive system. These are mainly present in joints, muscles and tendons.
Other receptors : (i) Pain sensory receptors present in deep position are called noiceptors. (ii) Presso receptors or baro-receptors All the sense organs are very important for the body. Every animal has the sense organs.
Shopping Cart
