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Transcript
Cell Cycle and Cancer Investigation 3 Focus Questions How do different tissues perform different functions? How does the cell cycle control cell division? How does the loss of regulation of the cell cycle lead to cancer? How can cancer lead to loss of tissue function? Multi-cellular Organisms Multi-cellular organisms are made up of millions of tiny cells. In any one organism, there are many different types of cells. Cells that share a common structure and function can be found grouped and organized into tissues. There are four types of animal tissue: epithelial, muscle, nerve, and connective tissue. Multi-cellular Organisms cont. Two or more tissues work together to form organs. An organ is a group of tissues that work together to perform a specific set of functions for the organism. There are many different organs throughout the human body. The lung, heart, liver, breast, and skin are just a few of the organs throughout the human body. The Skin The skin is an organ that contains several types of tissues including connective, epithelial, nerve and muscle tissue. It is the largest organ in the human body! The function of this organ is to protect the body from external harm like the sun, heat, cold, and germs. The skin is composed of the epidermis, dermis, and subcutaneous layers. The Lung The lung mostly contains epithelial and connective tissues. The function of the lung is to allow exchange of oxygen from the air we breathe to blood so that it can be delivered to other tissues in the body where it is needed for normal cell function. It also allows carbon dioxide waste in the blood that came from tissues throughout the body to leave the body through exhalation. The Lung continued Air enters the body when we breathe through the nose and mouth. The air travels down the trachea (wind pipe) and into the bronchioles. There are bronchioles for the left and right lung lobe. The bronchioles lead to the terminal bronchioles and then the respiratory bronchioles that terminate in the alveolar ducts. The alveolar ducts are passageways that lead directly to the pulmonary alveoli which are small air sacs where the oxygen in the air is absorbed. The Breast The breast is made of a combination of fatty, glandular, and connective tissue. These tissues function to supply milk for growing infants. Glandular tissue produces and releases substances for use in the body. During the majority of a woman’s life, the breast is inactive and does not produce milk. Milk production only occurs when the tissues become active 3-5 days after a woman gives birth to a child. Tissues continued All of these tissues require increases in cell number through out the life of the human body. The skin has constant cell loss due to exposure to UV light from the sun and various other external insults. The lung alveoli cells are repeatedly exposed to damaging chemicals inhaled with the air in our environment including pollution and cigarette smoke. The breast must transform from inactive tissue to the active tissue within days after a woman gives birth. Cell Division The increased number of cells are supplied though increased cell replication (or cell division). Cell division must be closely regulated so that cells only divide when needed or the organization of these of these tissues would be destroyed making it impossible for them to function properly. Cell Division continued Cell division is also important in early childhood. During this time of growth the human body grows at a very fast rate. This is due to a constant increase in the total number of cells making up the body. Cell Division is the process by which two identical cells are produced from a single parent cell. This process requires that the original (parent) cell copies all of its contents, including DNA and organelles, and splits these materials evenly into two new daughter cells. Cell Division continued Once an adult human is fully grown, most cells either stop or slow down this process of dividing. However, in certain tissues, like the skin, lung, or active breast tissue, cell division is still needed. Whether cell division is occurring rapidly as in a growing child, or at a slower rate as in certain adult tissues, this process must be carefully controlled. Too much or too little cell division interferes with normal tissue function. The process that controls cell division is called the cell cycle. The Cell Cycle 1. 2. 3. 4. The cell cycle is an ordered set of events that results in cell division—the production of two identical cells from a single parent cell. The cell cycle can be broken into 4 distinct phases: G1 or GAP phase S or DNA synthesis phase G2 or GAP2 phase M or Mitosis Phase G1 Phase During the G1 phase, the cell produces proteins and grows in size. During this phase, the cell is functioning normally, constantly making proteins. This constant increase in proteins is what causes the cell to get larger. The G1 phase ends when the cell has reached a certain size. Then the S phase, or DNA synthesis begins. S Phase During S phase, the cell will make an exact copy of the DNA contained in the cell nucleus through DNA replication. At the end of the S phase, each chromosome inside the nucleus of the cell consists of two identical sister chromatids. Each chromatid is made up of a double stranded DNA molecule. G2 or GAP 2 Phase During this phase, the cell has very little activity. The cell is no longer changing in size and is doing minimal metabolic activity. M Phase or Mitosis phase 1. 2. 3. 4. During this phase, the sister chromatids produced in the S phase are separated and cell division (cytokinesis) occurs. The M phase or Mitosis Phase of the cell cycle is made up of four distinct stages: Prophase Metaphase Anaphase Telophase When a cell is not going through one of these stages, it is said to be in interphase. Cancer If a gene that codes for the controlling protein is damaged or mutated, then a properly functioning protein cannot be produced. If there is no production of the controlling proteins, the cells will go through the cell cycle and divide unregulated. Each new (daughter) cell will inherit the mutated gene for this controlling protein because the cell receives an exact copy of the DNA in the original (parent) cell. This means that every daughter cell produced from the originally damaged cell will also divide continuously. Cancer continued Cancer is defined as a group of diseases that involve the uncontrolled cell division of body cells. Cancer begins when one normal body cell breaks free from the normal controls of the cell cycle and begins to follow its own rate of cell division. This happens after damage to the cell’s DNA has occurred, which affects the production of a cell cycle controlling protein. All cells produced by this cell, and all cells from those daughter cells, will also follow a uncontrolled rate of cell division. Cancer continued If this process continues, a tumor, or a mass of cells will develop. A tumor can invade normal tissue and therefore alter its overall organization and structure. This disorganization leads to an inability of the tissue to function, which in turn means that the organ cannot function properly. How Cancer Spreads If a single cancer cell breaks away from the tumor it can travel in the blood to other places throughout the body. At a new site, this single cancer cell will proliferate and form another tumor. This is called metastases and is how cancer spreads. Adenocarcinoma Lung cancer, called adenocarcinoma, is one of the leading causes of death in adults. One of the primary causes of lung cancer is cigarette smoke. The chemicals in cigarette smoke are inhaled and absorbed by cells in the lung. Often when looking under a microscope at a lung tissue section from a smoker, deposits of tar (toxins) can be seen in the cells as small black specks. These toxins damage DNA. If the damage occurs on a gene that normally codes for a cell cycle controlling protein, cancer can develop. Adenocarcinoma continued However, since the damage to DNA is random, some people can smoke for many years and not develop cancer, while others may only smoke a few times and even quit and still get cancer. Even second-hand cigarette smoke (smoke inhaled from other people smoking) can cause damage to cells’ DNA. Lung cancer is not only caused by smoking, but this is thought tom be one of the leading preventable causes of lung cancer.