Let's get to know the digestive system... Its importance is hidden in this article
The mechanical breakdown of ingested food begins with chewing in the mouth and continues with the contraction of the smooth muscles of the stomach and intestines. Digestion in the mouth occurs through chewing and the saliva secreted by the salivary glands located within the mouth.
Chemical breakdown, on the other hand, is carried out through certain enzymes secreted by the stomach, small intestine, and pancreas. These substances, called digestive enzymes, break down carbohydrates, proteins, and fats into molecules small enough to be easily absorbed.
The end products resulting from mechanical and enzymatic breakdown are delivered into the bloodstream from the small intestine, along with water, minerals, and vitamins. The digestive system is composed mainly of the following structures: the mouth (teeth and tongue), salivary glands, pharynx, esophagus, stomach, intestines, rectum, and anus.
The digestive system is, in fact, a long tube-like structure that begins at the mouth, ends at the anus, and connects to the outside world through these two openings. Some parts of this structure are responsible for transporting food (the mouth and esophagus), some for storing it (the stomach and large intestine), and another part is mainly responsible for digestion and absorption (the small intestine).
These functions of the digestive system are controlled by numerous hormones, enzymes, and the autonomic nervous system.
In addition to the autonomic nervous system, the intestines also have their own enteric nervous system. In short, the digestive system has an extremely extensive nerve network.
The autonomic nervous system is a visceral, largely involuntary, sensory and motor system. The autonomic nervous system controls the secretory glands, the heart muscle, and the smooth muscles of the internal organs. The autonomic nervous system is divided into two: the sympathetic nervous system and the parasympathetic nervous system.
• The sympathetic nervous system: This is the branch of the nervous system that acts in parallel with the emotions. In situations such as fear, joy, and excitement, the sympathetic nervous system is activated, blood pressure rises, the heart rate increases, and digestion slows down. The SNS continuously exerts a constrictive effect on the blood vessels in the extremities (arms and legs). In response to stimuli such as fear and anger, it prepares the body for a “fight or flight” response. The heart rate increases, the pupils dilate, and the skin sweats. Blood is redirected from the skin and digestive system to the skeletal muscles, and the sphincters in the digestive and urinary tracts close.
• The parasympathetic nervous system: The parasympathetic nervous system generally functions to balance the sympathetic nervous system. It carries stimuli to the central nervous system via sensory neurons and delivers responses to effector organs via motor neurons. The parasympathetic system slows the heart and increases salivary and intestinal secretions and intestinal movements.
The mechanical breakdown and dilution of ingested macromolecular food substances significantly helps to increase the rate of enzymatic breakdown of the food. Enzymatic breakdown reduces molecules to a size that can be easily absorbed. In this way, four fundamental events emerge in digestion.
These events are, in order, mechanical breakdown, dilution, enzymatic breakdown, and absorption.
Nearly every structure in the digestive system participates in the mechanical breakdown, dilution, enzymatic breakdown (hydrolysis), and absorption of food substances.
Mechanical breakdown is carried out through chewing and the contraction of the smooth muscles of the stomach and intestines; dilution and enzymatic breakdown are carried out by the secretions produced by the structures of the digestive system.
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