SPHU 1020: Cell, Individual, and Community. What is Cancer? Week of April 11
SPHU 1020: Cell, Individual, and Community. What is Cancer? Week of April 11 SPHU 1020
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This 3 page Class Notes was uploaded by Claire Jacob on Monday April 18, 2016. The Class Notes belongs to SPHU 1020 at Tulane University taught by Dickey-Cropley, Lorelei in Summer 2015. Since its upload, it has received 19 views. For similar materials see Cell, Individual & The Community in Public Health at Tulane University.
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Date Created: 04/18/16
What is Cancer? ● Cancer: a group of diseases characterized by uncontrolled growth and spread of abnormal cells ○ Untreated can lead to death ○ Affects almost every part of the human body ○ Every case of cancer begins as a change in a cell that allows cell to grow and divide when it should not ● Abnormal masses of tissue are called tumors ○ Can be benign (noncancerous) or malignant (cancerous) ● Cancerous cells can damage nearby tissue, and invade other areas of the body (metastasize) ● Classified according to types of cells that give rise to them ○ Carcinomas ○ Sarcomas ○ Lymphomas ○ Leukemias Looking back ● Tumors described as early as 1600 BC in ancient Egyptian writings such as Smith papyrus ● Hippocrates introduced term “carcinoma” derived from karkinos (crab) ○ Saw disease as clawing its way, crablike, through the body ● In 1800, Marie Francois Xavier Bichat proposed that cancer was an overgrowth of cellular tissue ● Cells identified as fundamental unit in tumor tissue in 1830, after invention of the microscope ● Rudolph Virchow’s 1858 theory that every cell originates from another cell became the foundation for present understanding of cancer The stages of tumor development A. Tumor begins to develop when a single cell’s DNA becomes altered, or mutated. We do not know exact number of mutations required for a normal cell to become a fully malignant cell, but it is probably fewer than 10. Accumulation of mutations can transform a normal cell into a cancerous one B. Altered cell and its descendents grow and divide rapidly, resulting in a condition called hyperplasia. At some point, one of these cells experiences another mutation that further increases its tendency to divide C. This cell’s descendants divide exessively and look abnormal, a condition called dysplasia. As time passes, one of the cells experiences yet another mutation D. This cell and its descendants are very abnormal in both growth and appearance. If tumor that has formed from these cells is still contained within its tissue of origin, called in situ, or stage 0, cancer. In situ cancer may remain contained indefinitely E. If some cells experience additional mutations that allow tumor to invade neighboring tissues and to shed cells into the blood or lymph. Tumor is said to be malignant. Metastasis ● Primary tumor original location of cancer ● New tumors called secondary tumors or metastases ● Can invade nearby tissues What causes cancer? ● Cancer is caused by both external factors and internal factors that occur from metabolism (chemical processes occurring within a living cell or organism that are necessary for the maintenance of life) ○ External factors include: tobacco, chemicals, radiation, and infectious organisms ■ Lymphomas can be triggered by the EpsteinBarr virus, which also causes mononucleosis ■ Damaging env agents (mutagens) include radiation, viruses, chemicals in air ○ Internal factors include: genetic, inherited mutations, hormones, immune conditions, and other mutations Infections and Cancer ● Infections can raise a person’s risk of cancer in 3 different ways ○ Some viruses directly affect the genes inside cells that control their growth. These viruses can insert their own genes into the cells causing the cell to grow out of control ○ Some infections can cause longterm inflammation in a part of the body. This can lead to changes in the affected cells and in nearby immune cells, which can eventually lead to cancer Some cancer are caused by viruses or bacteria ● `2 million new cancer cases attributable to infections ○ Higher in less developed countries ● Helicobacter pylori, hep B and C, and HPV responsible for 1.9 million cases, mainly gastric, liver, and cervix uteri cancers ● In women, cervix uteri cancer accounted for about ½ of infectionrelated burden of cancer ● In men, liver and gastric cancers accounted for more than 80% ● Around 30% of infectionattributable cases occur in people younger than 50 Genes and cancer ● There are genetic components Breast Cancer ● Most common cancer in women (after lung cancer) ● 1 in 8 women will develop it during her lifetime; i in 30 women will die from the disease ○ About 200,000 american women dx each year and 41,000 women die from it each year ● Risk factors ○ Rises quickly with age, about 50% occurring in women ages 4565 ○ Genetic predisposition/family history ■ BRCA genes ○ Estrogen connection ■ Early onset of menstruation ■ Late onset of menopause ■ Having first child after 30 ■ Having no children ■ Hormone replacement therapy ○ Obesity, diet, and alcohol use
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