Why human cells stops growing after a certain time ?
413070
Alternatively, if you meant why do cells stop dividing after a certain time it is because their telomeres get too short. Telomeres are the parts of DNA at the end of chromosomes. DNA polymerase requires a primer (a piece of DNA to sit on). It starts making new DNA from this point, but doesn't copy the part it sits on at first, so the copy is a tiny bit shorter than the original. Each time cells divide and copy their DNA, their telomeres get a little bit shorter. When they are too short the cell recognizes this and stops dividing.
804801
Death begins when the heart stops beating. Deprived of oxygen, a cascade of cellular death commences. It begins with brain cells and finishes with the skin cells. Death is therefore a process, rather than an event.\n\n When the heart stops beating\n\n1. Heart stops beating and/or lungs stop breathing.\n\n2. Body cells no longer receive supplies of blood and oxygen.\n\n    * Blood drains from capillaries in the upper surfaces and collects in the blood vessels in the lower surfaces.\n    * Upper surfaces of the body become pale and the lower surfaces become dark.\n\n3. Cells cease aerobic respiration, and are unable to generate the energy molecules needed to maintain normal muscle biochemistry.\n\n    * Calcium ions leak into muscle cells preventing muscle relaxation.\n    * Muscles stiffen and remain stiff (rigor mortis) until they begin to decompose.\n\n4. Cells eventually die and the body loses its capacity to fight off bacteria.\n\n5. The cells' own enzymes and bacterial activity cause the body to decompose - muscles lose their stiffness.\n\nTiming?\n\n    * Brain cells can die if deprived of oxygen for more than three minutes. Muscle cells live on for several hours. Bone and skin cells can stay alive for several days.\n    * It takes around 12 hours for a human body to be cool to the touch and 24 hours to cool to the core.\n    * Rigor mortis commences after three hours and lasts until 36 hours after death.\n    * Forensic scientists use clues such as these for estimating the time of death.\n\n What is rigor mortis?\n\nRigor mortis refers to the state of a body after death, in which the muscles become stiff. It commences after around 3 hours, reaching maximum stiffness after 12 hours, and gradually dissipates until approximately 72 hours after death. Rigor mortis occurs due to changes in the physiology of muscles when aerobic respiration ceases.\n\nMuscles are made up of two types of fibre. These fibres have connections between them that lock and unlock during muscle contraction and relaxation. These connections are controlled by a biochemical pathway within the cell, which is partially driven by the presence of calcium ions. The concentration of calcium ions is higher in the fluid surrounding muscle cells than it is inside the cells, so calcium tends to diffuse into the cell. High calcium levels inside the cell drive the biochemical pathway in the direction that maintains muscle contraction. To relax, muscle cells must expel the calcium ions from the cell and this requires energy molecules to pump them across the cell membrane.\n\nAfter a body has died, the chemical reaction producing these energy molecules is unable to proceed because of a lack of oxygen. The cells no longer have the energy to pump calcium out of the cell and so the calcium concentration rises, forcing the muscles to remain in a contracted state. This state of muscle stiffening is known as rigor mortis and it remains until the muscle proteins start to decompose.
896374
Mainly because embryonic stem cells proliferate (multiply rapidly) for a year or more in the laboratory without differentiating, but most adult stem cells cannot.  Scientists cannot have not determined why this is so but it works to their advantage.
923360
The size of fat cells increases and decreases as we add / lose weight BUT unless we get to the stage when the cells are absolutely "full as an egg" then the body does not actually make MORE fat cells.\n\nSo...\n\nIncrease in number:  when first developing in the womb and when continually gaining weight without end.\n\nIncrease / decrease in size: all the time as we lose/gain weight.\n\n\nThis is why it helps to lose as much weight as possible before having liposuction, as the fat cells are moreved they are "gone for good" unless you eat to great excess - in which case the body will then make new fat cells to replace the ones you vaccumed out.
371024
The cells undergo a process known as mitosis. This is when the chromosomes will duplicate themselves and then split into two cells. Hormones often tell cells when to begin mitosis. Your skin grows in 3 layers. The cells towards the inside will multiply and push older skin cells towards the 2nd, and 3rd layer until they die and fall off. This means that your skin in constantly renewing itself.
235848
The time is different for different types of cells, but doubling time is the time taken for a cell to complete the cell cycle. It is the amount of time between successful cell divisions.
170528
No, but there is evidence that it was "designed" to wear out and get old.  A region of the chromosome called the telomere is reduced in size with each cell division, once the cell has replicated so much that the telomere is gone, replication comes to a halt and the person eventually dies
270174
stem cells can regenerate. There are certain places in our body that do not regenerate (re-grow) any cells that get damaged such as our brain and nervous system. If stem cells are planted in those areas, it can help re-grow cells in those areas by which people can recover from serious illnesses.
832920
First off, cancer is an otherwise perfectly healthy cell that starts reproducing but doesn't stop when it should. \n\nMost cells in adult multicellular organisms don't divide because more cells aren't needed. Take yourself as an example: Once you stop growing your heart has all it needs to function, your lungs are big enough, and you have plenty of skin. If your cells didn't stop dividing you would keep growing, such is the case in people suffering from Gigantism.\n\nWhen cell loss (through damage or 'old age') is detected a chemical switch is flipped and surrounding cells are stimulated to divide in order fill the gap. Once the gap has been filled cells are supposed to stop reproducing.\n\nIf that "switch" gets broken or stuck in the "on" position, the cells won't stop dividing, and their offspring don't stop dividing. The new cells pile up on each other, forming a lump, and they'll keep dividing, making more cells, and more, and more, and more. That is cancer.
584546
There are parts of your body that stop growing.  Your brain for example stops growing after about 10 to 12 years old.  Your eyes stop growing after about a month old.  Some other internal organs also stop growing.  \n\nBones (legs, arms, feet, etc) stop growing after about 18 to 20 years old for males, 16 for females.\n\nShort answer, if you have no serious diseases, your eyes cannot become smaller, but rather you are becoming larger.\n\nBTW interesting fact, your nose will never stop growing.  If it's big now, wait until you're 60.
310592
Many people believe that a person's hair, fingernails and toenails continue to grow after death. Despite what you may have read or seen in the movies, this is false. Once a person has died all growth of the hair and nails ceases. After death the body dehydrates and the skin around the hair and nails will recede a little making it appear as the deceased's nails and hair have grown. However, it is only an optical illusion. The nails and hair remains the same length as before but more of it is exposed due to tissue shrinkage.
924940
The dna and other components of the cell have started to break down.
202126
All living cells change every 7 to 10 years. Bones, muscles, fat, etc. Even the enamel on your teeth undergoes a slow change.\n\nBones have living cells that continually decompose the mineral matrix of ol bone an dutilize the calcium for your boy while other cells are laying down a new matrix at the same time.\n\nOur blood recycles every 30 days give or take. The cells in our muscles are repalced and added to or subtracted as needed. That is one of the reasons why you can get buff and cut and not work out for 10 months and not be as strong as before.\n\nThe part about the vitrious humour of the eye is also correct. Thsi is a liquid produced by cells lining this area. These cells are repalced, but the fluid remains MOSTLY unchanged. If you have a leak due to injury the body will replenish it slowly. It is often used to test for time of death, and for poisonings as it is not easily cycled from the body.
345920
It divides by mitosis then it begin to grow.According to which type of cell your referring to.That's what I think.
49056
from what I learned in my anatomy class, when you gain fat cells you never lose them. They shrink when you lose weight. Thats why overweight people have to stick with a healthy lifestyle after they lose a bunch of weight because its so easy to enlarge those fat cells again if they go back to bad eating habits.
355307
It isn't a very good control if your cells die before the experiment is complete.  More info is needed to get a more specific answer.
921540
It's different for each tissue in the body... some examples are: epithelial (skin) cells: 1 month, or neurons (brain cells) : 50 years.