THE 5 SENSE ORGANS AND THEIR MAIN FUNCTIONS - ANATOMY AND PHYSIOLOGY - 2025

The 5 sense organs are the eyes, skin, nose, ears, and tongue. Its main functions have to do with the interaction between the human body and the stimuli in its environment.

The information provided by the senses in the form of nerve impulses allows the human being to move safely and independently. With the sense organs, people can perceive light, sound, temperature, tastes and smells.

These stimuli are converted into nerve impulses that are interpreted by the brain to generate a response. This process is possible thanks to the sensory receptors.

What are sensory receptors?

The sense organs have sensory receptors. These are structures with cells specialized in detecting specific types of variations in environmental conditions.

If such variations exceed a certain value (threshold), the nerve impulse is generated that will travel through the neurons.

According to the type of stimulus they perceive, sensory receptors are classified into chemoreceptors, mechanoreceptors, thermoreceptors, and photoreceptors.

Chemoreceptors

They allow to perceive chemical elements related to flavors and odors.

Mechanoreceptors

They are the receptors that allow us to perceive textures, pressure, vibrations (such as sound waves), the sensation of balance and the contact or not of objects or other people.

Thermoreceptors

This type of receptor intervenes in the perception of temperatures.

Photoreceptors

With this type of receiver, electromagnetic energy can be perceived.

The 5 sense organs and their main functions

1- The skin: the sense of touch

The skin is the largest organ in the human body since it covers it completely. The sense of touch works in the skin. This sense allows to perceive qualities of external objects such as texture, temperature, pain, pressure, among others.

In this way, the human being can calculate whether or not to touch certain objects, according to his ability to resist the sensations that such objects produce. Internal nerve endings can also function as touch sensors.

The sexual organs and the fingertips are the parts of the body with the highest number of nerve endings.

The skin has mechano and thermoreceptors in all its layers, which are the dermis, epidermis and hypodermis.

These receptors come in the form of Meissner corpuscles (they allow us to perceive shapes, sizes and textures), Pacini (they help the organism to perceive the pressure and weight of objects), Ruffini (they intervene in the perception of heat) and of Krause (they allow to perceive the cold).

In addition, the hairiness of the skin magnifies sensitivity to stimuli.

2- The eyes: the sense of sight

The eye is an organ that allows us to capture the image of the external world. It is related to the sense of sight. This is the sense that allows people to see and recognize the shapes, colors and dimensions of objects in the outside world.

It also allows the human to calculate distances between himself and the objects around him.

To determine the main functions of the eye it is important to know its parts. Its characteristics are detailed below:

Cornea

It is the transparent surface on which light rays are refracted.

Iris

It is the part that controls the amount of light that passes through the eye pupil thanks to the ciliary muscles. The iris is where the color of the eye is distinguished.

Pupil

It is the opening that is located in the center of the iris through which light passes.

Crystalline

It serves as a regulator of the direction of light so that it reaches the retina correctly.

Retina

It is located at the back of the eye and converts light rays into electrical energy, so that they reach the optic nerve.

Optic nerve

Connects the eye to the brain stem so that electrical energy reaches the occipital lobe, the place in the brain where electrical energy is transformed into an image

The operation of the eye is similar to that of a camera: the light passes through the lens and goes to the retina, where the optic nerve leads it to the brain and there the image is reproduced.

When there is a lot of light, the iris contracts, decreasing the amount of light that can pass through it. The eye perceives a light spectrum that ranges from red to violet.

3- The nose: the sense of smell

Olfactory bulb

The nose is an organ located in the center of the face that is related to the sense of smell. Its internal part is in the roof of the mouth.

It has two pits that serve for the exit and entry of the air for breathing. These fossae are separated by the septum, a structure made up of cartilage and bone that is lined with mucous membranes.

Inside the nose are the yellow pituitary, which has olfactory receptors, and the red one, which contributes to the regulation of the temperature of the air that enters and leaves the lungs.

Also inside the nose there are villi called cilia, which help filter the air of impurities.

Also, in this organ are the paranasal sinuses, which are four pairs of air-filled cavities that are located near the nostrils. The paranasal sinuses are classified as edmoidal, maxillary, ephenoidal frontal.

With the human nose, up to 10,000 smells can be detected. Odors are vapors that emanate from different substances.

It is also believed that in the nose there is a specialized structure to perceive pheromones related to the reproductive cycle of the human being.

Smell stimulates the appetite and digestive secretions, thanks to the chemoreceptors in the nasal passages.

4- The tongue: the sense of taste

It is an organ located inside the mouth that has the function of hydrating both the mouth and food, and making language possible. It is related to the sense of taste, which allows to identify soluble substances in saliva, to complement the function of smell.

The parts of the tongue are: upper and lower face, lingual borders, base and tip. It also has an osteofibrous skeleton and several muscles that enable its movement.

On the upper side are the taste buds with the chemoreceptors that will allow us to perceive the substances dissolved in the saliva.

This sense fulfills the function of allowing people to distinguish different flavors, being able to detect those that indicate that a food is in bad condition.

How does it work?

If a papilla receives a stimulus through one of the dissolved substances, it sends nerve impulses to the brain that are interpreted as flavors. The main flavors that this sense recognizes are: sweet, bitter, sour and salty.

Each part of the tongue is specialized in capturing a flavor: sweet is captured at the tip, bitter near the base, acid at the lingual edges, and salty at the tip or at the edges.

Women tend to have this sense better developed than men.

5- The ear: sense of hearing

The ear is an organ that allows us to perceive sounds and their different qualities (volume, tone, timbre and origin). Its structure can be divided into internal, external and medium.

Sound waves enter the outer ear and travel through the ear canal to the eardrum, where they cause a vibration. This vibration moves three small bones of the middle ear (hammer, anvil and stapes).

The waves of the movement of the ossicles reach the fluid of the inner ear where there are thousands of hair cells that transform the waves into electrical signals, which go to the brain thanks to the superior auditory nerves.

There, the brain combines the signals received from both ears to determine the distance and direction of the sound.

In the middle ear, the semicircular canals of the vestibular system are those that intervene in the balance of the human body and its sense of spatial orientation.

The ear can perceive frequencies between 16 (lowest) and 28 thousand (highest) cycles per second.

The type of receptor that the ears have are called phonoreceptors, although they also have mechanoreceptors that help to perceive balance.

In fact, balance is a complex sensation in which the brain uses stimuli from the middle ear, the eyes, proprioceptive sensors (located in the skin and muscles) and the central nervous system.

Some authors include kinesthesia and synesthesia between the human senses.

References

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