The sense organs – eyes, ears, tongue, skin, and nose help to protect the body. The human sense organs contain receptors that send data via sensory neurons towards the suitable locations within the nervous system.
Each sense organ contains different receptors.
- General receptors are found throughout the body because they exist in skin, visceral organs (visceral meaning in the abdominal cavity), muscles, and joints.
- Special receptors include chemoreceptors (chemical receptors) found in the mouth and nose, photoreceptors (light receptors) found in the eyes, and mechanoreceptors found in the ears.
Eyes are organs of the visual system. They provide organism’s vision, the capability to process visual information, as well as allowing several photo feedback functions that are separate of vision. Eyes detect light and convert it into electro-chemical stimulus in neurons. In greater organisms, the eye is a complicated optical system which gathers light from the surrounding environment, controls its strength through a diaphragm, focuses it through a versatile assembly of lenses to create an image, converts this image within a set of electrical signals, and transmits these signals towards the brain via complicated neural pathways that connect the eye through the optic nerve towards the visual cortex along with other areas of the brain.
The simplest “eyes”, such as those in microbes, do nothing however detect whether the surroundings are light or dark, which is sufficient for the entrainment of circadian rhythms. From more complex eyes, retinal photosensitive ganglion cells send out signals along the retinohypothalamic tract to the suprachiasmatic nuclei in order to influence circadian adjustment and to the pretectal area in order to control the pupillary light reflex.
The ears are organs that provide two main functions – hearing as well as balance– that depend on specialized receptors called hair cells.
- Hearing: The eardrum oscillates when sound waves enter the ear canal. Ossicles, three tiny bones (including the stapes, the tiniest bone in the body), pass vibrations to the oval window, which is a membrane at the entrance to the inner ear.
- Balance: Balance is accomplished through a combination of the sensory organ in the inner ear, visual input, and info received from receptors in the body, especially around joints. The details processed in the cerebellum and cerebral cortex of the brain allows the body to cope with modifications in speed and the direction of the head.
The ear is divided into three parts:
- Outer ear: The outer ear consists of an ear canal that is lined with hairs and glands that produce wax. This part of the ear gives protection and channels sound. The auricle or pinna is the most noticeable part of the outer ear and what many people are describing when they utilize the word “ear”.
- Middle ear: Three small bones – the malleus, incus, and stapes – within the middle ear transfer sound vibrations from the eardrum to the inner ear. The middle ear is important because it is filled with many air spaces, which provide routes for infections to travel. It is also the location of the Eustachian tube, which equalizes the air pressure in between the inner and outer surfaces of the tympanic membrane (eardrum).
- Inner ear: The inner ear, also called the labyrinth, runs the body’s sense of balance and includes the hearing organ. A bony covering houses a complicated system of membranous cells. The inner ear is referred to as the labyrinth because of its intricate shape. There are two main sections within the inner ear: the bony labyrinth and the membranous labyrinth. The cochlea, the hearing organ, is located inside the inner ear. The snail-like cochlea is comprised of three fluid-filled chambers that coil around a bony core, which contains a central channel referred to as the cochlear duct. Inside the cochlear duct is the main hearing organ, the spiral shaped organ of Corti. Hair cells inside the organ of Corti identify sound and send out the information through the cochlear nerve.
- The nose is the body’s primary organ of smell as well as operates as part of the body’s respiratory system.
- The nose has an area of specialised cells which are accountable for smelling (part of the olfactory system). Another function of the nose is the conditioning of inhaled air, warming it and making it more humid. Hairs inside the nose prevent large particles from getting in the lungs.
- Sneezing is usually triggered by foreign particles irritating the nasal mucosa, however can more rarely be caused by unexpected direct exposure to bright light (called the photic sneeze reflex) or touching the external auditory canal. Sneezing can transfer infections, due to the fact that it creates aerosols in which the droplets can harbour microorganisms.
- Air enters the body through the nose. As it passes over the specialized cells of the olfactory system, the brain recognizes and identifies smells. Hairs in the nose tidy the air of foreign particles. As air moves through the nasal passages, it is warmed and humidified before it enters into the lungs.
- The most common medical condition related to the nose is nasal congestion. This can be brought on by colds or influenza, allergic reactions, or ecological aspects, leading to inflammation of the nasal passages. The body’s response to blockage is to convulsively eliminate air via the nose by a sneeze.
- Rhinoplasty is a cosmetic surgery treatment for problems, both medical and aesthetic, with the nose.
- The tongue is a muscular organ in the mouth. The tongue is enveloped with moist, pink tissue known as mucosa. Tiny bumps called papillae give the tongue its rough texture. Countless taste buds cover the surfaces of the papillae.
- Taste buds are collections of nerve-like cells that link to nerves running into the brain. The tongue is attached to the mouth by webs of tough tissue and mucosa. The tether constraining the front of the tongue is called the frenum. In the back of the mouth, the tongue is anchored into the hyoid bone. The tongue is crucial for chewing and swallowing food, along with for speech.
- The four common tastes are sweet, sour, bitter, and salty. A fifth taste, called umami, results from tasting glutamate. The tongue has many nerves that assist identify and transfer taste signals to the brain. Because of this, all parts of the tongue can identify these four common tastes; the commonly described “taste map” of the tongue does not really exist.
- Chemicals that promote taste receptor cells are known as tastants. As soon as a tastant is liquified in saliva, it can reach the plasma membrane of the gustatory hairs, which are the websites of taste transduction.
- The tongue is equipped with lots of taste buds on its dorsal surface, and each taste bud is covered with taste receptor cells that can notice particular classes of tastes. Distinct kinds of taste receptor cells respectively identify compounds that are sweet, bitter, salted, sour, spicy, or taste of umami. Umami receptor cells are the least understood and accordingly are the type most intensively under research study.
The skin safeguards us from microorganisms and the components, helps manage body temperature level, and permits the feelings of touch, heat, and cold.
Skin has three layers:
- The epidermis, the outermost layer of skin, provides a waterproof barrier and produces our skin tone.
- The dermis, underneath the epidermis, contains tough connective tissue, hair follicles, and gland.
- The much deeper subcutaneous tissue (hypodermis) is made from fat and connective tissue.
Skin has mesodermal cells, coloring, such as melanin given by melanocytes, which absorb a few of the possibly harmful ultraviolet radiation (UV) in sunlight. It also contains DNA repair work enzymes that help reverse UV damage, such as individuals not having the genes for these enzymes suffer high rates of skin cancer. One form primarily produced by UV light, malignant melanoma, is particularly intrusive, causing it to spread quickly, and can often be deadly. Human skin coloring varies among populations in a striking manner. This has actually caused the classification of individuals on the basis of skin color.
The skin is the biggest organ in the human body. For the normal adult human, the skin has a surface area of between 1.5-2.0 square meters (16.1-21.5 sq ft.). The thickness of the skin varies considerably over all parts of the body, and in between men and women and the young and the old. An example is the skin on the forearm which is on average 1.3 mm in the male and 1.26 mm in the woman. The typical square inch (6.5 cm ²) of skin holds:
- 650 sweat glands
- 20 blood vessels
- 60,000 melanocytes
- More than 1,000 nerve endings
The typical human skin cell has to do with 30 micrometers in diameter, but there are variations. A skin cell generally varies from 25-40 micrometers (squared), depending upon a range of factors.