Learn about The Cell in this educational video from dizzo95.
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Female Speaker: Cells are the microscopic building blocks of the body, among the smallest human cells are some nerve cells while the largest cell the ovum has a diameter of 5 1000th of an inch, the size of a pin point. Each cell is a self-contained living unit which become modified and specialized as it develops and is integrated into the body's systems. When actual functioning cells in tissues and organs are packed together in close proximity they take on a variety of shapes. Muscle cells for example are elongated into fibers. Liver cells are hexagonal and the cells which lie in the intestine are column shaped. The cutaway view of a generalized cell as presented here and magnified to 6000 times the average size reveals the working parts concerned with systems of cell support, maintenance, repair and multiplication. The cell nucleus, a spherical structure contains the basic genetic material, deoxyribonucleic acid or DNA in the form of chromosomes. The nucleus controls the overall activity of the cell. The nuclear envelope is a two-layered membrane surrounding the nucleus. The envelope acts as a sieve controlling the continuos flow of chemicals to and from the nucleus. The nucleolus house within the nucleus has under a microscopic a granular appearance. This is due to its concentration of ribonucleic acid or RNA. Cytoplasm is the watery medium of the cell in which all the structures are suspended. Most of the work of the cell is carried on in the cytoplasm. The cell membrane is a soft pliable skin which acts as a controlled gate for the entry and exit of substances involved in cell function. The endoplasmic reticulum is a network of flatten sacks and tubes which provides a communication channel for materials passing between the nucleus and the cells environment. The lysosomes are simple sacks which store enzymes, the powerful chemicals involved in digestion. The mitochondria are the main sites of energy production within the cell. Pits on the surface of the cell capture fluid which contains large molecules such as proteins and carry it toward the interior. The ribosomes are the sites where proteins are made. They contain RNA similar to that in the nucleus. The centrioles are involved in cell division during which they move apart to opposite poles of the cell beating a delicate trace array within the cytoplasm and Golgi's complex acts as a -- for the storage and secretion of cell products. Working around the clock, the human cell is comparable is to a small factory. Like a factory, the cell takes in a continuos flow of raw materials for processing and packaging of its own chemical waste ready for disposal.