--HUMAN EAR:

The ear consists of three basic parts - the outer ear, the middle ear, and the inner ear. Each part of the ear serves a specific purpose in the task of detecting and interpreting sound. The outer ear serves to collect and channel sound to the middle ear. The middle ear serves to transform the energy of a sound wave into the internal vibrations of the bone structure of the middle ear and ultimately transform these vibrations into a compressional wave in the inner ear. The inner ear serves to transform the energy of a compressional wave within the inner ear fluid into nerve impulses which can be transmitted to the brain.

THE OUTER EAR:

The outer ear consists of an ear flap and an approximately 2-cm long ear canal. The ear flap provides protection for the middle ear in order to prevent damage to the eardrum. The outer ear also channels sound waves which reach the ear through the ear canal to the eardrum of the middle ear. Because of the length of the ear canal, it is capable of amplifying sounds with frequencies of approximately 3000 Hz. As sound travels through the outer ear, the sound is still in the form of a pressure wave, with an alternating pattern of high and low pressure regions. It is not until the sound reaches the eardrum at the interface of the outer and the middle ear that the energy of the mechanical wave becomes converted into vibrations of the inner bone structure of the ear.

THE MIDDLE EAR:

The middle ear is an air-filled cavity which consists of an eardrum and three tiny, interconnected bones - the hammer, anvil, and stirrup. The eardrum is a very durable and tightly stretched membrane which vibrates as the incoming pressure waves reach it. As shown at the right, a compression forces the eardrum inward and a rarefaction forces the eardrum outward, thus vibrating the eardrum at the same frequency of the sound wave. Being connected to the hammer, the movements of the eardrum will set the hammer, anvil, and stirrup into motion at the same frequency of the sound wave. The stirrup is connected to the inner ear; and thus the vibrations of the stirrup are transmitted to the fluid of the middle ear and create a compression wave within the fluid. The three tiny bones of the middle ear act as levers to amplify the vibrations of the sound wave. Due to a mechanical advantage, the displacements of the stirrup are greater than that of the hammer. Furthermore, since the pressure wave striking the large area of the eardrum is concentrated into the smaller area of the stirrup, the force of the vibrating stirrup is nearly 15 times larger than that of the eardrum. This feature enhances our ability of hear the faintest of sounds. The middle ear is an air-filled cavity which is connected by the Eustachian tube to the mouth. This connection allows for the equalization of pressure within the air-filled cavities of the ear. When this tube becomes clogged during a cold, the ear cavity is unable to equalize its pressure; this will often lead to earaches and other pains.

THE INNER EAR:

The inner ear consists of a cochlea, the semicircular canals, and the auditory nerve. The cochlea and the semicircular canals are filled with a water-like fluid. The fluid and nerve cells of the semicircular canals provide no roll in the task of hearing; they merely serve as accelerometers for detecting accelerated movements and assisting in the task of maintaining balance. The cochlea is a snail-shaped organ which would stretch to approximately 3 cm. In addition to being filled with fluid, the inner surface of the cochlea is lined with over 20 000 hair-like nerve cells which perform one of the most critical roles in our ability to hear. These nerve cells have a differ in length by minuscule amounts; they also have different degrees of resiliency to the fluid which passes over them. As a compressional wave moves from the interface between the hammer of the middle ear and the oval window of the inner ear through the cochlea, the small hair-like nerve cells will be set in motion. Each hair cell has a natural sensitivity to a particular frequency of vibration. When the frequency of the compressional wave matches the natural frequency of the nerve cell, that nerve cell will resonate with a larger amplitude of vibration. This increased vibrational amplitude induces the cell to release an electrical impulse which passes along the auditory nerve towards the brain. In a process which is not clearly understood, the brain is capable of interpreting the qualities of the sound upon reception of these electric nerve impulses.


-- LIVER:

The liver is the largest glandular organ of the body. It weighs about 3 lb (1.36 kg). It is reddish brown in color and is divided into four lobes of unequal size and shape. The liver lies on the right side of the abdominal cavity beneath the diaphragm. Blood is carried to the liver via two large vessels called the hepatic artery and the portal vein. The heptic artery carries oxygen-rich blood from the aorta (a major vessel in the heart). The portal vein carries blood containing digested food from the small intestine. These blood vessels subdivide in the liver repeatedly, terminating in very small capillaries. Each capillary leads to a lobule. Liver tissue is composed of thousands of lobules, and each lobule is made up of hepatic cells, the basic metabolic cells of the liver.


MAJOR FUNCTION:

The liver has many functions. Some of the functions are: to produce substances that break down fats, convert glucose to glycogen, produce urea (the main substance of urine), make certain amino acids (the building blocks of proteins), filter harmful substances from the blood (such as alcohol), storage of vitamins and minerals (vitamins A, D, K and B12) and maintain a proper level or glucose in the blood. The liver is also responsible for producing cholesterol. It produces about 80% of the cholesterol in our body.

--PANCREAS:

The pancreas is a glandular organ that secretes digestive enzymes (internal secretions) and hormones (external secretions). In humans, the pancreas is a yellowish organ about 7 inches (17.8 cm) long and 1.5 inches. (3.8 cm) wide.
The pancreas lies beneath the stomach and is connected to the small intestine at the duodenum .

The pancreas contains enzyme producing cells that secrete two hormones. The two hormones are insulin and glucagon. Insulin and glucagon are secreted directly into the bloodstream, and together, they regulate the level of glucose in the blood. Insulin lowers the blood sugar level and increases the amount of glycogen (stored carbohydrate) in the liver. Glucagon slowly increases the blood sugar level if it falls too low. If the insulin secreting cells do not work properly, diabetes occurs.

The pancreas produces the body's most important enzymes. The enzymes are designed to digest foods and break down starches.

The pancreas also helps neutralize chyme and helps break down proteins, fats and starch. Chyme is a thick semifluid mass of partly digested food that is passed from the stomach to the duodenum. If the pancreas is not working properly to neutralize chyme and break down proteins, fats and starch, starvation may occur.