Cell Cycle: Mitosis (Nursing)

00:01 So the next component of the cell that we're going to discuss is the nucleus.

00:05 And the nucleus is the most important of the organelles because it allows for us to actually function and so I refer to this as the "brain" of the cell.

00:16 Inside of the nucleus, we have our hereditary units of the cell, or our genes.

00:22 Our genes are located on a molecule called DNA and it is in these genes that encode everything that we need in order to perform all of life's functions.

00:34 The genes are arranged along chomosomes that are found inside of our cells and our DNA is so long that these chromosomes allow for all of these information to fit inside of the nucleus.

00:51 So in discussing the nucleus, it's important to discuss exactly how a cell cycles or the life of a cell.

01:00 So the cell, if you think about it like a clock, the cell spends most of its time in a part of the cell cycle known as interphase.

01:10 In interphase, there are certain processes that are going to occur at different steps in interphase.

01:17 Interphase is divided into three sub-phases.

01:21 G1 being the phase where normal cellular processes are occuring and as well where the cell begins to prepare to divide.

01:32 Why does the cell need to divide in th first place? Remember, in life's basic processes, growth is essential.

01:42 It is a requirement for all living things and so cell division allows for organisms such as humans to grow.

01:51 So in G1, we prepare to grow by doubling in size as well as doubling the number of organelles that are found inside of the cell.

02:00 From there, we go to S phase.

02:04 An S Phase is when we double the amount of DNA.

02:07 Why do I need to double the amount of DNA? Again, I'm going to create two cells from originally one cell so everything needs to be twice as big and I need to have twice as much of everything so that my new cell is exactly like the other cell.

02:25 So after we go to S phase, we then enter into G2 phase.

02:29 And G2 phase is what I like to refer to as kind of like the proofreading and prep phase.

02:36 So before I divide, I need to make sure that the new cell that I'm gonna make is exactly like the old cell.

02:43 I want to make sure that the DNA has been copied correctly or replicated correctly and I wanted to just make sure that the cell is ready.

02:52 Once I go through the proofreading process, I can then enter into the other part of the cell cycle which is M Phase or the mitotic phase of the cell cycle.

03:04 In mitosis, I'm going to start with one cell and end up with two cells.

03:10 So one cell that is doubled in size with double the number of organelles will now become two identical cells.

03:18 It's very important to remember in mitosis that the two cells are genetically identical.

03:25 That is the goal of mitosis and that will become important later when we talk about reproductive cell division.

03:35 In mitosis, there are basically four major steps.

03:39 We're gonna start with prophase where we're preparing the cell to divifde by creating these microtubule or mitotic spindle fibres that are going to eventually be used to pull the cell apart.

03:55 In metaphase, all of our chromosomes are gonna line-up single file across the cell to what's known as the mitotic plate.

04:04 and this is going to allow for the duplicated DNA because remember, we duplicated in S phase so everything is by two to be separated eventually.

04:17 In anaphase, those mitotic spindle fibers are now going to separate those two duplicated chromosomes away from each other and pull them towards opposite poles of the cell.

04:30 And then finally in telophase, we begin to start the formation of new cells as well as an entirely new nucleus.

04:42 After the mitotic phase, we go through cytokinesis.

04:47 Cytokinesis is actually separate from mitosis and involves the actual separating of the two nuclei that we just made during during mitosis.

04:58 Cytokinesis is usually gonna start during telophase and eventually you end up with two genetically identical cells.

05:08 So when it comes to cell division, remember I said it's important for our cells to be able to divide but what are the possible destinies of the cell division? Well first off, some of our cells actually are non-dividing cells.

05:25 Examples of non-dividing cells in your body include your muscle cells.

05:29 So believe it or not, all of the muscle cells in your body are the same muscle cells that you had when you were born.

05:35 And instead of getting new muscle cells, the muscle cells that you already have just get bigger and bigger and bigger as you grow.

05:44 Other types of cells that are non-dividing also includes certain types of nerve cells which is why when you destroy or sever a nerve, it can lead to paralysis because there's no process to replace those types of cells.

06:01 Another destiny of our cells is to grow and divide normally.

06:07 And then finally, a third destiny which is actually a very important destiny of your cells, is to die.

06:14 We actually need our cells to be able to die.

06:17 We need old cells to die when they are no longer useful or if they become defective and as well actually during the developmental process, when we are developing from an embryo and turning into a baby, there's going to be an interplay between cells growing and dividing and also between cells dying.

06:39 So for example in the womb, your fingers and toes are webbed and then as you begin to develop, the cells in between the digits began to die and we get individual fingers.