EYES and their functions

 

The eye is a complicated machine in itself with many parts. The eye works by refracting light rays to the retina. The light rays are adjusted through muscles and certain parts to create the right amount of light refracted to the retina. When light arrives at the retina it is converted to both chemical and electrical energy before being sent through optic nerves to the brain. In the retina, millions of rods containing rhodopsin that are responsible for night vision and convert the light into electrical impulses sent to the brain. The retina also contains millions of cones that contain iodopsin that are used for bright light vision, visual perception, and color perception. Light is transformed here also and sent to the brain through optic nerves. The brain translates what it receives through optic nerves so that we understand what we see.

Cornea

The cornea is the dome shape outer covering of the eye. It is like the windows of the car. It allows you to see but around you but protects you as well. The cornea is where most of the focusing of light occurs. It consists of many layers including the epithelium which is the tough outer layer that regenerates fairly quickly. The epithelium is usually removed or cut during many refractive procedures where the cornea is reshaped to focus light better.

Sclera

The Sclera is the outer white part of the eye that you can see. It provides protection and structure for the inner parts of the eye.

Conjunctiva and Lacrimal Glands

The conjunctiva is a mucus layer that keeps the eye moist. Infections to this area are known as the popular “pink eye.” Lacrimal glands are found on the outer part of each eye and are producers of tears.

Vitreous Humor and Aqueous Humor

The Vitreous Humor is gel like substance in the back part of the eyeball which provides the shape of the eyeball. The Aqueous Humor is the watery region in the form of the eye ball. It is separated into two regions, the anterior chamber in front of the iris and the posterior chamber behind it. The canal of Schlemm drains water in this region and is sometimes blocked off leading to the disease known as glaucoma or other complications.

Sclera

The Sclera is the outer white part of the eye that you can see. It provides protection and structure for the inner parts of the eye.

Iris and Pupil

The Pupil is the dark, black circle of the eye. It contracts with brightness and expands during darkness allowing light to better transmit. The iris is the colored part of the eye. This coloring is due to pigment cells in tissue in the iris. The iris contains the sphincter pupillae, a muscle used to narrow the pupil, and the dilator pupillae, a muscle used to widen the pupil.

Lens

The lens is a clear layer behind the pupil that does just what a regular lens does. The lens main purpose is to focus light by changing its shape. The ciliary body are muscles attached to the lens that help the lens change it shape to better focus light to the retina.

Retina

The retina is the inner most layer of sensitive tissue. When light is transmitted here images can clearly be transmitted to the brain. The retina consists of many layers including layers of rods and cones. Many cells in the retina transform light into chemical and electrical energy that is transferred to optic nerves. The back center of the retina contains themacula. The Macula is a highly sensitive part of the retina. It is responsible for our detailed vision. The center of the macula is called thefovea which has a major role in detailed perception. When there is damage to the macula, we are unable to see finer details.

FUN FACTS

• The human eye blinks an average of 4,200,000 times a year.
• It's impossible to sneeze with your eyes open.
• Our eyes are always the same size from birth, but our nose and ears never stop growing.
• Our body has some natural protection for our eyes. Our eyelashes help to keep dirt out of our eyes. Our eyebrows are made to keep sweat from running into our eyes.
• The shark cornea has been used in eye surgery, since its cornea is similar to a human cornea.
• The number one cause of blindness in adults is diabetes.
• The eyeball of a human weighs approximately 28 grams.
• The eye of a human can distinguish 500 shades of the gray.
• The cornea is the only living tissue in the human body that does not contain any blood vessels
• People generally read 25% slower from a computer screen compared to paper.
• Men are able to read fine print better than women can.
• All babies are colour blind when they are born.
• Babies' eyes do not produce tears until the baby is approximately six to eight weeks old.

Muscles

Muscles are one of those things that most of us take completely for granted, but they are incredibly important for two key reasons: Muscles are the “engine” that your body uses to propel itself.  Muscles turn energy into motion just like a car engine or an electric motor would do. It would be impossible for you to do anything without your muscles. Absolutely everything that you conceive with your brain is expressed as muscular motion. The only ways for you to express an idea are with the muscles of your larynx, mouth and tongue to speck words and the muscles of your fingers when taking with your hands or even dancing, or running.

When most people think of “muscle,” they think about the muscles that we can see. For example, most of us know about the biceps muscles, abs muscles. But there are three unique kinds of muscles in the human body, which are skeletal muscles, smooth muscle, and cardiac muscle. Skeletal muscle is the type of muscle that we can see and feel. When a body builder works out to increase muscle mass, skeletal muscle is what is being exercised. They attach to the skeleton and come in pairs, one muscle to move the bone in one direction and another to move it back the other way. These muscles usually contact voluntarily.  Smooth muscle is found in your digestive system, blood vessels, bladder, airways, and in a female, the uterus. Smooth muscle has the ability to stretch and maintain tension for long period of time. Smooth muscles also contracts involuntarily, meaning that you do not have to think about contracting it because your nervous system controls it automatically. Lastly, the cardiac muscle is found only in your heart, and its big features areenduracne and consistency. It can stretch a limited way, like smooth muscle, and contract with the force of a skeletal muscle. It is a twitch muscle and only contracts involuntarily.

Smooth                                                   skeletal                                                  cardiac 

             

The Skeletal System

The skeletal system is made up of bones and teeth. The normal human body has 206 bones which are needed for variety of functions within the body. The role of bones extends beyond the function of giving your body its shape. There are many reasons why bones are important to the body.  One of the most important functions that bones have in our body is providing support and structure. Bones are the hardest and most rigid structures in our body. The skeletal system also plays an important role in the protection of the vital organs throughout the body. The skull and the backbone protect the central nervous system. This protective role is especially important because the central nervous system controls the rest of your body and is very fragile. The ribs also protect the vital organs in the chest, such as the lungs and heart.  The skeletal system is also closely interacts with the muscles system. Bones are necessary because the muscles need something to attach to in order to contract and cause motion. Bones are also important as a center for the production of blood cells.  Lastly, the bones are responsible for the regulation of calcium levels. Calcium levels in the blood have to be kept in a narrow range to make sure the nerves and muscles are about to properly work. Much of the calcium is stored in the bones. When the body needs more calcium, bone tissue can be broken down to increase the blood’s supply and excess calcium can be stored in bone tissue for later.

Some interesting facts about the skeletal systems are:

1. Babies are born with 300 bones.

2. We are about 1 cm taller in the morning than in the evening.

3.The tooth is the only part of the human body that can't repair itself.

4.The feel account for one quarter of all the human body's bones.

5. Some bones are stronger than steel.