As one continues to understand the human body, one basic yet important question is always asked, what does the human body do? The human body is highly organized that it is able to perform different actions at the same time, without us even knowing that we are doing an action.
This encompasses the physical and chemical barriers that distinguish the internal environment of our body to that of the external environment which surrounds it. Examples of these barriers are membranes, the physical presence of our skin and protective coverings.
The purpose of these boundaries not only serves as a limiting membrane but it is also able to admit contents and other substances that are essential to the body and at the same time, it acts as a gatekeeper that restricts the entry of potentially harmful and damaging substances.
Upon closer inspection, one will notice that every cell in our body is protected by a membrane that is selectively permeable. The integumentary system protects the internal organs from bacteria, a fatal change due to the drying of our internal organs and the damage that is caused by sunlight.
It is said that the most difficult thing that a human person can do is to stay still. Movement of the body is influenced by stimulus and is enacted by the muscular system. Running, walking, swimming and even the subtle changes made by our fingers are all actions of movement. Movement also includes the flow of blood in our body, the propelling of urine and the shortening and lengthening of the cells.
The human body is very sensitive to changes or stimuli in the environment. To picture this ability, you may have experienced touching a hot surface and then all of a sudden you withdraw your hand away from the source of heat in just a split second! That is a classic example of our responsiveness or irritability. Another example is when the equilibrium inside the body is no longer attained, like an increase in carbon dioxide. When that happens, sensors will send signal to the brain and the brain will make adjustments that makes you breath faster.
Ingested food is broken down right from its entry and as it travels along the alimentary canal. As the food is digested or broken down, nutrients are collected and distributed throughout the body.
Metabolism is a broad term and includes all chemical reactions occurring in the body cells. Catabolism is the breaking down of substances into their simpler form; anabolism is the synthesizing of more complex cellular structures from simpler substances. ATP, which is what powers the activities of the cell, is made from oxygen and nutrients via cellular respiration.
Excreta is the term also used when referring to wastes. As the different parts of the body functions the way it is programmed to, by-products are produced and serve no purpose to the body. These needs to be removed from the body and several organ-system work in collaboration for this to happen. The digestive system is responsible for excreting unnecessary materials in the form of feces. The urinary system disposes unnecessary fluids and metabolic wastes that contains nitrogen in the form of urine. The respiratory system is the system that removes carbon dioxide, the metabolic waste of oxygen exchange.
Every day, reproduction occurs in the body. The cells divide, giving rise to new and fresh cells that replaces the worn-out and dying cells. The cells produced are identical to the parent cell and functions as a mirror image to that of the parent cell. The major task of the human body is the production of a new person.
As the number of cells increases, the body tries to adjust by expanding, thus the increase in size leading to growth. In order for true growth to happen, constructive activities must happen faster compared to the destructive process.