[Music] in animal cells microfilaments made up of actin and myosin proteins that are involved in muscle contraction and other forms of cell movement form rings around the equator of the cell these rings are attached to the cellular membrane during cyto canis the Rings contract and pull in the equator of the cell much like the pulling of drawrings creating what is called a cleavage Furrow as the contracto Rings become smaller and smaller the cleavage Furrow becomes deeper and deeper until the parent cell is pinched in two producing two completely independent cells plants have stiff cell walls that can't easily be pinched apart thus the process of cyto canis in plant cells is quite different from that in animal cells rather than microfilaments pinching off the cellular membrane at the Equator the GGI bodies of both daughter cells Bud off carbohydrate filled vesicles that line up along the Equator of the parent cell these vesic fused together to form a structure called the cell plate that divides the parent cell into new daughter cells the membrane material that formed the vesicles fuses with the existing cell membrane on either side of the cell plate to form a new continuous cell membrane in each daughter cell the carbohydrates contained in the vessels form the middle Lamela of the new cell wall between the two plasma membranes each of the two daughter cells then secret cellulose between their new cell membrane and the middle Lela to form the primary cell wall many plants later secrete additional cellulose molecules and other polysaccharides beneath the primary wall forming a thick secondary wall the events of interphase and mitosis like so many other processes in our bodies and cells are orchestrated by regulatory proteins biologists are just now beginning to understand how these proteins interact to synchronize the events of the cell cycle but they've known for quite a while that different types of cells often proceed through the cell cycle at very different rates in our own bodies the cells that form our skin and line our intestines are continually dividing in order to replace worn out cells on the other hand the nerve and muscle cells of adult humans whose functioning depends critically on established connections and interactions with other cells usually exit the cell cycle entirely by by entering the goo phase for cells that remain in the cell cycle the decision to divide or not divide is controlled by both internal and external factors [Music] [Music]