Tuesday, June 1, 2010

Degenerative Diseases

1. What are degenerative diseases?
Degenerative diseases are non infectious prevalent diseases whose incidences increase with aging.

2. What are risk factors for diseases?
Risk factors for a disease are everything that contributes to increase the risk of the disease to appear. For example, for most cardiovascular diseases, tobacco smoking and diabetes mellitus are both important risk factors; for some cancers having a genetic component a positive family history is a risk factor, etc.

3. What are the main human degenerative diseases?
The main human degenerative diseases are divided into three groups: cardiovascular diseases, neoplastic diseases and degenerative diseases of the nervous system. The main cardiovascular diseases are hypertension, the cardiopathies, including coronary disease and myocardial infarction, and the cerebrovascular accidents (CVAs, or strokes). Neoplasias are benign tumors and cancers. The main degenerative diseases of the nervous system are Alzheimer's disease and Parkinson's disease.

4. What is hypertension?
Hypertension is a disease in which the arterial blood pressure, during systole or during diastole, is abnormally high.
Hypertension, or high blood pressure, is a condition that must be diagnosed and treated since it produces irreversible injuries in arteries and, later, it causes other severe diseases in organs like the heart, brain, kidneys, retina, etc.

5. What are the main risk factors for hypertension?
The main risks factors for hypertension are tobacco smoking, stress, obesity, sedentary lifestyle and alcoholism.

6. What is the relation between the maximum and the minimum blood pressure with the phenomena of systole and diastole?
The maximum blood pressure is the pressure on the wall of the systemic arteries during systole, i.e., when the heart is pumping blood to arterial vessels. The minimum blood pressure is the pressure on the wall of the systemic arteries during diastole, i.e., when the heart ventricles are relaxing and getting blood.

7. What are the main degenerative diseases of the heart?
The main degenerative diseases of the heart are heart failure, arrhythmias, valvular heart diseases, coronary insufficiency and myocardial infarction. 

8. What is coronary disease?
Coronary disease, or coronary insufficiency, is a disease in which there is total or partial obstruction of one or more of the arteries that irrigate the heart musculature, i.e., obstruction of the coronary arteries. The disease is formed by slow and gradual formation of atheroma plaques inside the coronaries. The fatty plaques grow and block the flow of blood, a process known as atherosclerosis (do not confuse with arteriosclerosis which is the hardening of the arteries generally cause by chronic high blood pressure).
The main risk factors for coronary disease are tobacco smoking, diabetes mellitus, hypertension, hypercholesterolemia (high level of bad cholesterol and low level of good cholesterol), stress, alcoholism and sedentary lifestyle.
Coronary disease may present in two manners, as angina pectoris or as myocardial infarction. If the arterial obstruction is not complete and extensive the patient often feels chest pain (angina pectoris), mainly when performing physical exercise or in any situation when the heart needs more oxygen. If the obstruction of one or more coronaries is complete or blood cannot irrigate some regions of the heart muscle (myocardium) the infarction occurs and the muscle cells of the affected area die.

9. What is myocardial infarction?
Myocardial infarction is the condition in which an area of this tissue or the entire heart muscle dies by hypoxia due to lack of blood irrigation. Myocardial infarction is a severe disease since on the dependence of its extension the heart can fail, i.e., it can no longer pump blood to the lungs or to the body or it can even stop beating (causing death).
The main cause of myocardial infarction is coronary obstruction, blocking of the arteries that carry arterial blood to the heart muscle. Other events like hemodynamic shock (circulation stoppage due to large hemorrhages, for example) can also cause myocardial infarction.

10. What is coronary bypass graft?
Coronary artery bypass graft is a kind of surgical myocardial revascularization, i.e., a way to provide blood to a myocardium whose blood supply is impaired or blocked due to coronary disease. In this surgical treatment of coronary disease one or more blood vessel grafts taken from other parts of the body are used to join the obstructed artery (in a region after the obstruction) with the aorta or other healthy coronary artery thus reestablishing the blood flow to the myocardium. Often the blood vessel grafts are part of the saphenous vein from the leg or of the mammary artery from the chest or even of the radial artery from the forearm.

11. What are cerebrovascular accidents?
Cerebrovascular accident (CVA), also known as stroke, is the generic name given to infarction (tissue and cellular death by hypoxia) of areas of the brain due to vascular obstruction or hemorrhages. CVAs are divided into ischemic and hemorrhagic. In the ischemic CVA blocking of arteries that carry blood to the brain occurs; its cause is generally atherosclerosis (atheroma formation) of these vessels. In the hemorrhagic CVA there is rupture of one or more blood vessels of the brain with blood leakage, increasing intracranial pressure and thus interruption of blood flow in some areas of the brain. The severity of the stroke depends on the function performed by the affected area of the brain, for example, motor function, visual function, vegetative function, etc., and on the size of the involved area.
The main risk factors for cerebrovascular accidents are hypertension, hypercholesterolemia, tobacco smoking and old age.

12. What are neoplasias?
Neoplasia is any abnormal and uncontrolled proliferation of cells of an organism. Neoplasias can be benign or malign. Benign neoplasias are those in which the cell proliferation is limited to a given site of the body and so neoplastic cells do not spread to other close regions or at distance through the circulation. Malign neoplasias are those in which the neoplastic cells disseminate at distance to other sites and organs of the body, a process called metastasis, where they continue to proliferate. Malign neoplasias injure tissues and if not eradicated they are fatal. Benign neoplasia can also be deadly when it forms a tumor that grows and compresses vital organs.

13. How different are the concepts of neoplasia, tumor and cancer?
Not every tumor is neoplastic and not every neoplasia creates tumor. Tumor is the generic name given to the abnormal increase in mass or volume of any area of the body (for example, the enlarged tonsils during throat infection are a kind of tumor, any inflammation creating a swelled area characterize a tumor, etc.). Neoplasias can form tumors, some of them very large, by aggregation of neoplastic cells in the region where the neoplasia began or in distant implantations. Cancer is a synonym for malign neoplasia.

14. What is cancer?
Cancers are malign neoplasias, i.e., abnormal and uncontrolled proliferation of cells that can disseminate to other sites of the body. Cancer dissemination at distance usually occurs through blood or lymphatic vessels.

15. How do malign neoplasias appear?
Neoplasias appear due to DNA mutations in genes that regulate the cellular proliferation thus making the cell lose its capacity to control and limit its division by mitosis. The cell then divides continuously and uncontrollably and this defect is transmitted to its daughter cells.

16. What are carcinogens?
Carcinogens are factors capable of producing neoplasias. Any mutagen, a substance that can induce DNA mutation, is a potential carcinogen. Examples of carcinogens are radiation, nitrous acid, many substances inhaled through tobacco smoking and the human papilloma virus (HPV).

17. How do cells of neoplastic tumors obtain oxygen and nutrients and release wastes?
In neoplastic tumors a phenomenon called angiogenesis occurs. Angiogenesis is the formation of new blood vessels. Neoplastic cells induce the formation of new blood vessels to irrigate and drain the neoplastic tissue.
Angiogenesis is important because the tumor growth depends on it. A lot of research on cancer has tried to discover natural and synthetic substances to inhibit angiogenesis.

18. What are the main types of cancer that affect humans?
Excluding skin cancer, that are the more easily detected and so cases are registered in larger number, the main types of cancer in men are prostate cancer, lung cancer, stomach cancer; in women, breast cancer, colon and rectal cancer and lung cancer are of great incidence. Other common cancers are ovarian cancer, pancreatic cancer, liver cancer, esophageal cancer, brain cancer and the leukemias and lymphomas (blood cancers).
Epithelial cancers, of the skin as well as of the internal organs, are more common because epithelial tissues are more exposed to carcinogens.
The proportional incidence of the many types of cancers varies according to the considered population.

19. What is the main risk factor for lung cancer?
The main risk factor for lung cancer is tobacco smoking. The large number of cases of this type of cancer is due to the increased number of smokers worldwide.

20. What is the main risk factor for skin cancer?
The main risk factor for skin cancer is solar exposition of the skin without protection against ultraviolet radiation (a potential carcinogen).
The most lethal skin cancer is melanoma.

21. How is cancer usually treated?
If the cancer is in its initial stage treatment is often done by surgical removal of the neoplastic tissue. Cancers already disseminated are often treated with radiation (radiotherapy) and anti-mitotic drugs (chemotherapy).

22. What are the main degenerative diseases of the nervous system?
The main degenerative diseases of the nervous system are Alzheimer’s disease and Parkinson’s disease.
Degenerative diseases of the nervous system are caused by progressive tissue degradation or loss of neurons in some regions of the nervous system.

23. What is Alzheimer’s disease?
Alzheimer’s disease is a degenerative disease of the central nervous system in which the patient has progressive dementia and alteration of mental functions.
The disease generally appears after 40 years of age and it is more frequent in the elderly. Image studies of the brain show broad loss of brain tissue. (The Alzheimer’s disease should not be confused with other mental deteriorations common in the elderly.)

24. What is Parkinson’s disease?
Parkinson’s disease is a degenerative disease of the nervous system in which the main manifestations are progressive motor disturbances, like tremors of feet, hands and mandibles (jaws) and walking and balance impairments. Parkinson’s disease is due to the degeneration of dopaminergic motor neurons, i.e., motor neurons that use dopamine as a neurotransmitter, located in a specific region of the brain, the mesencephalon. Such degeneration creates deficiency of dopamine in the nervous system. (Parkinson’s disease should not be confused with other causes of tremors, like the use of some medicines.)

No comments:

Post a Comment