EAR:

The ear is the organ of hearing and balance. It converts sound waves into electrochemical signals that are interpreted by the brain and helps you maintain your sense of balance. The parts of the ear include:

 

Outer ear: The outer ear consists of the auricle or pinna - the visible portion of the ear that projects from the side of the head - and a short external auditory canal., consisting of:

Pinna or auricle: This is the outside part of the ear.

External auditory canal or tube: This is the tube that connects the outer ear to the inside or middle ear.

Tympanic membrane (eardrum): The tympanic membrane divides the external ear from the middle ear.

 

Middle ear (tympanic cavity), consisting of:

Ossicles: Three small bones that are connected and transmit the sound waves to the inner ear. The bones are called: Malleus; Incus; Stapes

Eustachian tube: A canal that links the middle ear with the back of the nose. The eustachian tube helps to equalize the pressure in the middle ear. Equalized pressure is needed for the proper transfer of sound waves. The eustachian tube is lined with mucous, just like the inside of the nose and throat.

 

The inner ear consists of:

Cochlea: This contains the nerves for hearing.

Vestibule: This contains receptors for balance.

Semicircular canals: These contain receptors for balance.

 

How do you hear?

The hearing starts with the outer ear. When a sound is made outside the outer ear, the sound waves, or vibrations, travel down the external auditory canal and strike the eardrum (tympanic membrane). The eardrum vibrates. The vibrations are then passed to 3 tiny bones in the middle ear called the ossicles. The ossicles amplify the sound. They send sound waves to the inner ear and into the fluid-filled hearing organ (cochlea).

Once the sound waves reach the inner ear, they are converted into electrical impulses. The auditory nerve sends these impulses to the brain. The brain then translates these electrical impulses to sound.

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NOSE:

 

Your nose helps you to breathe and to smell. The inner part of the nose is above the roof of the mouth. The nose is made up of:

• External meatus. Triangular-shaped projection in the center of the face.

• External nostrils. Two chambers are divided by the septum.

• Septum. Made up mainly of cartilage and bone and covered by mucous membranes. The cartilage also gives shape and support to the outer part of the nose.

• Nasal passages. Passages are lined with mucous membranes and tiny hairs (cilia) that help to filter the air.

• Sinuses. Four pairs of air-filled cavities, also lined with mucous membranes.

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THROAT:

The throat is a ring-like muscular tube. It is the passageway for air, food, and liquid. It also helps in forming speech. The throat is made up of:

• Voice box (larynx). The larynx is a cylindrical grouping of cartilage, muscles, and soft tissue that contains the vocal cords. The vocal cords are the upper opening into the windpipe (trachea), the passageway to the lungs.

• Epiglottis. A flap of soft tissue located just above the vocal cords. The epiglottis folds down over the vocal cords to prevent food and irritants from entering the lungs.

• Tonsils and adenoids. They are made up of lymph tissue and are located at the back and the sides of the mouth. They protect against infection. But they don't really have a function after childhood.

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CANCER:

Cancer is a disease in which some of the body’s cells grow uncontrollably and spread to other parts of the body. Cancer can start almost anywhere in the human body, which is made up of trillions of cells.  Cancerous tumors spread into, or invade nearby tissues and can travel to distant places in the body to form new tumors.

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Differences between Cancer Cells and Normal Cells

Cancer cells differ from normal cells in many ways. For instance, cancer cells:

• Grow in the absence of signals telling them to grow. Normal cells only grow when they receive such signals. 

• Ignore signals that normally tell cells to stop dividing or to die (a process known as programmed cell death, or apoptosis).

• Invade into nearby areas and spread to other areas of the body. Normal cells stop growing when they encounter other cells, and most normal cells do not move around the body. 

• Tell blood vessels to grow toward tumors.  These blood vessels supply tumors with oxygen and nutrients and remove waste products from tumors.

• Hide from the immune system. The immune system normally eliminates damaged or abnormal cells. 

• Trick the immune system into helping cancer cells stay alive and grow. For instance, some cancer cells convince immune cells to protect the tumor instead of attacking it.

• Accumulate multiple changes in their chromosomes, such as duplications and deletions of chromosome parts. Some cancer cells have double the normal number of chromosomes.

• Rely on different kinds of nutrients than normal cells. In addition, some cancer cells make energy from nutrients in a different way than most normal cells. This lets cancer cells grow more quickly. 

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