Phagocytosis Process

Phagocytosis is a process used by certain cells to engulf and ingest solid particles. The particles engulfed and ingested can be nutrient particles or bacteria. The cells capable of ingesting in such a manner, by the phagocytosis process, are known as phagocytes. The phagocytes can be free living unicellular organisms, such as amoeba, or they can be part of the body cells of a multicellular organism. Phagocytes belongs to the family of processes, that are collectively referred to as 'endocytosis', consisting of all the processes that involve ingestion of material by cell.

What is the Process of Phagocytosis

Phagocytosis process is a specific type of endocytosis, that involves vesicular internalization of solid particles, such as bacteria, unlike other endocytosis process that involve vesicular internalization of liquids. Certain unicellular organisms, such as the protists, use this particular process as means of feeding. It provides them part or all of their nourishment. This mode of nutrition is known as phagotrophic nutrition. In amoeba, phagocytosis takes place by engulfing the nutrient with the help of pseudopods, that are present all over the cell, whereas, in ciliates, a specialized groove or chamber, known as the cytostome, is present, where the process takes place.

Other examples of phagocytosis include some immune system cells, that engulf and kill certain harmful, infectious micro-organisms and other unwanted foreign materials. Mammalian immune system contains certain phagocytes that helps them to destroy and get rid of pathogenic bacteria and other infectious organisms. In these cells, the engulfment of foreign material is facilitated by actin-myosin contractile system. It allows the cell membrane to expand in order to engulf the particle and then contract immediately, ingesting it.

Phagocytosis Steps

It is quite fascinating to watch the process under a microscope. One can actually see the phagocyte engulfing the foreign particle. There are several distinct steps involved in the process of phagocytosis. Let us have a look at them.

In case of unicellular organisms, the process of phagocytosis takes place when the organism comes in contact with the nutrient particles. The phagocytes in the immune system are activated in the presence of certain bacterial cells, inflammatory cells or other foreign bodies. Let us talk about the general steps involved in the process.

Step 1: The phagocytes get activated by the presence of certain particles around them. As soon as they detect a foreign particle, the phagocytes produce surface glycoprotein receptors, that increase their ability to adhere to the surface of the particle.

Step 2: The phagocyte slowly attaches to the surface of the foreign particle. The cell membrane of the phagocyte begins to expand and forms a cone around the foreign particle.

Step 3: The cell membrane surrounds the foreign particle from all sides to create a vacuole, known as phagosome or food vacuole. The phagosome is then passed into the cell for absorption.

Step 4: Now comes the role of the lysosomes, which are cell structures, that are specialized in digesting the particles that enter the cell through the cell membrane. The lysosomes break the food vacuole or phagosome, into its component materials. The essential nutrients, if any, are absorbed in the cell, and the rest is expelled as waste matter. In case of the immune system, the cell creates a peroxisome, a special structure that helps the body to get rid of the toxins.

In unicellular organisms like amoeba, phagocytosis is necessary for survival, as they are totally dependent on it for nutrients. Some of these organisms have adapted special traits which enable them to locate and keep a track of the food particles.