Cells

How do cells grow and divide?

A cell divides into two new cells (mitosis process). A checking process monitors the mitosis process for incorrect operations. Faulty cells are thought to go through the mitosis process without proper checking.
Cells are grouped together to form tissues and organs.
Different types of tissues are made up of different types of cells.
 Cells divide and grow very quickly between conception (young) and adulthood (old).
Cells divide and grow for about 50 to 60 times/cycles before they die.
The cell cycle is a division process with 4 main stages: stage 1 – cells grow in size and check for errors, stage 2 – cells copy DNA, stage 3 – check for correct DNA, stage 4 – cells divide into two.
When cells are damaged, they will self destruct (apoptosis process). This process prevents cells from growing without control.
Cancer starts with changes in one cell or small group of cells.
The primary tumor is the location of where the cancer starts.
There have to be half a dozen different mutation before a normal cell turns into a cancer cell.
Benign tumors grow slowly, don’t spread to other cells.
Malignant tumors grow quickly in size, spread to other cells, and release hormones to affect the surrounding.
Normal (cancer) cells grow and divide and eventually form tissues (tumors).
A tissue (tumor) may contain millions of cells.
The basement membrane is a layer to keep cells inside tissues.
Invasive cells can break through the basement membrane.
Normal (cancer) cells cannot live without oxygen and nutrients.
To encourage the formation of new blood vessels, angiogenic factors are produced (angiogenesis process).
Without a blood supply, a tissue (tumor) can’t grow much bigger than a pin head.
One approach to suppress cells growing is to control the blood supply to the cells via the angiogenesis process (cutting the formation of blood vessels via angiogenic factors).
3 different ways that tissues (tumors) may grow into surrounding tissues (tumors): pressure from the growing tumor, enzymes, crosstalk with surrounding cells (mobility).
The location where cancer cells start growing is the primary site. The secondary site (metastasis) is where cancer cells grow to new areas.
To spread to new areas, cancer cells break away from the basement membrane from the primary site and via the bloodstream or lymphatic system to grow in new areas.
Case 1: Cancer cells go into small blood vessels in order to go to the bloodstream (circulating tumor cells).
The circulating blood carries the cancer cells throughout the body. If cancer cells get stuck in a very small blood vessel (capillary), cancer cells must move through the cell wall and into the tissues to form new cells (tumors).
Upper bound (0.1%): 1 in 1000 circulating tumor cells can survive this circulating pathway to form the secondary site.
Lower bound (0.0001%): 1 in 900,000 circulating tumor cells can survive this circulating pathway to form the secondary site.
Beside getting stuck in a very small blood vessel, cancer cells could stick to blood cells (platelets) to enhance chances to stick to larger blood vessels and to form new cells in new areas.
The lymphatic system circulates body fluid via a network of tubes and glands.
Case 2: Cancer cells may get stuck in small tubes and glands and to form new tumors (lymph node spread).
Chemotherapy drugs are used to attack cells that are in the process of doubling to form new cells.
Cells (as well as cancer cells) go into a long rest period between divisions. Thus chemotherapy drugs will not be effective to these cells.
Cells may die off naturally or through other complex cell defense mechanisms.
Radiotherapy uses radiation to break DNA during the cell growth and division. Both normal cells and cancer cells are affected by this process.
Biological therapies control the cell growth and division to minimize the tissues (tumors).
p-glycoprotein helps cells to remove toxins via pumping mechanism.
Cells with high p-glycoprotein levels tend to be less effective by chemical invasion.
To identify the stage of cells, TNM is employed:
  • T (tumor) – check the size of the cells (1 – 4)
  • N (node) – check if cells spread to lymph nodes (0 – 3)
  • M (metastasis) – check if cells spread to other areas (0 – 1)
  • cT2 N1 M0 – clinical tumor size 2, spread to lymph node level 1, no metastasized.
  • pT4 N3 M1b – pathological tumor size 4, spread to lymph node level 3, and metastasized to lung.
What are stem cells and how do they relate to cancer stem cells?
Stem cells have potential to develop into different cell types.
There are two possible outcomes from dividing and growing stem cells: stem cells divide and grow into stem cells; stem cells divide and grow into specialized cells such as muscle cell or red blood cell.
Some tumor cells are thought to develop from faulty stem cells. If so, what other internal or external factors trigger the faulty development?
How do some cells around mature age that do not reproduce so often?
 
How do cells know when to stop growing?
How do cell know when to recycle cell materials?

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