(Be sure to also visit Page 2, Page 3, and Page 4 of the 3D Medical Animation Library)

What is the difference between a blackhead and a whitehead? Do you know what casues acne? Watch this video to find out.	Actinic keratosis (AK), or solar keratosis, or senile keratosis is a precancerous skin condition that develops in the skin when exposed to sun, hydrocarbons, and arsenicals and is more common in light-skinned people	Attention deficit hyperactivity disorder (ADHD) is a common childhood behavioral disorder. ADHD is characterized by inattention, hyperactivity and impulsive behavior. This informative video animation shows possible causes and treatments.
An allergy is an over-reaction of the immune system to a normally harmless substance called an allergen. This detailed video animation shows the causes of allergic reactions and how anti-histamine's can stop the reaction.	The most common cause of dementia occurring in patients over 45 yrs of age is Alzheimer's disease. This video animation shows how an abnormal tau protein in Alzheimer's patients can cause the microtubule structures to collapse.	Percutaneous Transluminal Coronary Angioplasty (PTCA) ? often abbreviated to angioplasty ? is a procedure to re-open a narrowed coronary artery. Watch how this procedure opens arteries.
Asthma is a disorder of obstruction to breathing due to inflammation and narrowing of the bronchial tubes. Pollen, pet dander, weather changes, tobacco smoke, etc. can trigger and worsen asthma symptoms in susceptible patients.	See how muscle spasms and Disc Prolapse can cause back pain. Disc Prolapse happens when the soft inner material of the vertebral disc bulges or bursts through the outer lining of cartilage and puts pressure on the spinal nerve	Bipolar disorder is a psychiatric disease characterized by episodes of extreme mood swings, depression and mania.

............................................................................................ ... ........... Next >>

Coughing--Coughing is a sudden expulsion of air from the lungs through the epiglottis at an amazingly fast speed (estimated at 100 miles per hour). With such a strong force of air, coughing is the body's mechanism for clearing the breathing passageways of unwanted irritants.
Allergy--Allergens like pollen are nothing more than foreign plant antigens. The stimulus for sneezing gets triggered when allergens first enter the nasal tissue. Pollen allergens encounter the plasma cells in the nose, which respond by producing antibodies. These antibodies attach to mast cells, which are white blood cells containing the chemical histamine. As more antibodies are produced, they cause the mast cells to release histamine. Histamine then produces allergy symptoms. A stuffy and runny nose, sneezing and watery eyes help to remove the invading pollen.
Breathing--The two lungs are the primary organs of the respiratory system. Other components of the respiratory system conduct air to the lungs, such as the trachea (windpipe) which branches into smaller structures called bronchi.
The process of breathing (respiration) is divided into two distinct phases, inspiration (inhalation) and expiration (exhalation). During inspiration, the diaphragm contracts and pulls downward while the muscles between the ribs contract and pull upward. This increases the size of the thoracic cavity and decreases the pressure inside. As a result, air rushes in and fills the lungs.
During expiration, the diaphragm relaxes, and the volume of the thoracic cavity decreases, while the pressure within it increases. As a result, the lungs contract and air is forced out.
Immune Response--The immune system is comprised of specialized white blood cells, called lymphocytes that adapt themselves to fight specific foreign invaders. These cells develop into two groups in the bone marrow. From the bone marrow, one group of lymphocytes migrates to a gland called the thymus and become T lymphocytes or T cells. Within the thymus, the T cells mature under the influence of several hormones. The T cells mature into several different types, including helper, killer and suppressor cells.
When matured, the T cell types are ready to work together to directly attack foreign invaders, providing what physicians call cell-mediated immunity. This type of immunity can become deficient in persons with HIV, the virus that causes AIDS, because HIV attacks and destroys helper T cells. The other group of lymphocytes, B lymphocytes or B cells, mature and develop within the bone marrow itself. In that process, they achieve the ability to recognize specific foreign invaders.
From the bone marrow, B cells migrate through the body fluids to the lymph nodes, spleen and blood. B lymphocytes provide the body with humoral immunity as they circulate in the fluids in search of specific foreign invaders to destroy.
Lungs-Interactive Tool--After the animation loads, click and drag the model to rotate it in any direction. Select a term from the structure list to travel to its location.
Click the "pin" button to hide or show the identification pin.
Click the "light bulb" button to view in highlight or full color mode.
Click the "double box" button to see and rotate the model in transparent mode.
Lymph Nodes--The lymphatic system is a complex network of thin vessels, valves, ducts, nodes, and organs. It helps to protect and maintain the fluid environment of the body by producing, filtering, and conveying lymph and by producing various blood cells. Lymph nodes play an important part in the body's defense against infection.
The most common cause of swollen lymph nodes is infection, which might occur even if the infection is trivial or not. Afferent lymph vessels bring unfiltered fluids into the lymph node to be filtered while efferent vessels carry clean fluids away from the lymph node and to the cardiovascular system where it helps form the plasma in the blood.
Overall, lymph nodes work like a biological filtering system. When the body is invaded by foreign organisms, the painful swelling sometimes felt in the neck, armpits, groin, or tonsils comes from the microorganisms being trapped inside collections of lymph cells or nodes. Eventually, these organisms are destroyed and eliminated by cells that line the walls of the lymph nodes and the swelling and pain subside.
Lymphatics and Breast--The lymphatic system is often referred to as the body's "secondary circulatory system". The lymphatic system collects excess fluid in the body's tissues and returns it to the bloodstream. Lymph formation occurs at the microscopic level.
During the exchange of fluid and molecules between the blood circulation and body tissues, blood capillaries may not reabsorb all of the fluid. Surrounding lymphatic capillaries absorb the excess fluid. The fluid is then filtered and transported back by the lymphatic system into large veins near the heart. The lymphatic system can play a very worrisome role in the spread of breast cancer. Components of the lymphatic system called lymph nodes are distributed at specific locations throughout the body.
There is also an extensive network of lymphatic vessels in every woman's breast tissue, which is important in regulating the local fluid balance as well as in filtering out harmful substances. The lymph vessels in the breast may inadvertently supply cancerous cells with access to a highway along which the cancerous cells can move to other parts of the body.
This process is called metastasis and may result in the formation of a secondary cancer mass in a different location of the body. Regular breast self examinations can help to detect tumors earlier in their growth, hopefully before they spread quickly or metastasize.
Phagocytosis--Macrophages are scavenger cells that can ingest dead tissue and foreign cells. Macrophages form tentacles called pseudopods to surround an invader. Once inside the macrophage, the invader is walled off and then digested and destroyed by a bag of digestive chemicals, or enzymes.
Vaccines--Vaccinations are injections of antigens into the body. Once the antigens enter the blood, they circulate along with other cells, such B and T cells. B and T cells are white blood cells that help the body defend itself against foreign invaders. As the antigens invade the body's tissues, they attract the attention of macrophages. Macrophages are non-specific scavengers, which in this case, engulf the antigens.
The macrophages then signal the T cells that antigens are invading. The killer-type of T cells respond by attacking the invading antigen. Finally, the suppressor T cells stop the attack. After a vaccination, the body will have a memory of an encounter with a potentially dangerous invader for a period of time, and hopefully have a better ability to fight it off if ever exposed to it again in greater numbers.