Mechanical Digestion vs Chemical Digestion
Food has to be ingested first followed by digestion, and finally absorption takes place before defecation. Ingestion is simply the eating process that gives animals the mental satisfaction with a taste, as they take their food through the mouth. Digestion is the breaking down process which takes place inside mouth, stomach and duodenum of the alimentary tract. First, the food has to be digested mechanically and then, chemically. As the food goes into the oral cavity, it is mechanically digested by the teeth and chemically digested by saliva. Through the pharynx and oesophagus, the major chemical digestion occurs with enzyme secretions from different glands associated with the digestive tract. However, in some animals viz. crocodiles, ratite birds, and seals the mechanical breakdown of food items takes place in the stomach. This article intends to discuss the similarities and differences between these two important aspects.
What is Mechanical Digestion?
Food particles are broken down into small pieces in the mechanical digestion. Generally, this starts as soon as the food is ingested into the mouth through the process called mastication. Mastication, in simple terms, is known as the chewing of food. Teeth are calcified structures inside the oral cavity designed especially for mastication of food. In crocodiles, ratite birds, and seals, the gastroliths perform the function of mechanical digestion of food. Those are the rock-hard structures inside a crocodile’s stomach. However, other than teeth and gastroliths, peristaltic movements are also helpful for mechanical digestion of food as it passes through oesophagus, stomach, and duodenum. In the other parts of the alimentary tract also the peristalsis occurs, but not the mechanical digestion. Mechanical digestion completes at the duodenum as one of the most important aspects of feeding.
What is Chemical Digestion?
Mechanically broken down food particles consist of finely ground organic materials, which are more often composed of long and complex molecules. These molecules have to be simplified by means of chemical digestion in order for them to be able to absorb into the body. Digestive enzymes are responsible for the chemical breakdown of food. Amylase, Trypsin, Nuclease, Protease, Lipase, and Collagenase are some of the major digestive enzymes. The concentrations and presence of enzymes determine the speed of chemical digestion. Different enzymes are responsible for digestion of their specific molecules (e.g. proteases for proteins; amylase for carbohydrates; lipase for lipids). Accessory organs of the alimentary tract are extremely important in producing digestive enzymes. Salivary glands, Gall bladder, Liver, and Pancreas are the major accessory glands that produce digestive enzymes other than the stomach. Additionally, the secretion of Hydrochloric acid inside the stomach creates a very low pH acidic environment, which helps immensely for the enzymatic digestion. Chemically digested food is then ready for the absorption at the small intestine.
What is the difference between Mechanical Digestion and Chemical Digestion?
Mechanical breakdown triggers the digestion process by differentiated teeth inside the oral cavity. After the mechanical digestion, the chemical formula is not changed, but the physical shape and size of the ingested food items are changed. In contrast to mechanical process, the enzymatic digestion changes the chemical formula and more often the complex chains of the molecules are simplified in such a way that they are ready to be absorbed. Additionally, enzymes are responsible for breaking down of specific food molecules. In different places of the alimentary tract, different enzymes are secreted for digesting food. Food is both mechanically and chemically digested at oral cavity, stomach and duodenum. However, more mechanical digestion takes place inside the mouth, whereas the duodenum and stomach perform mostly chemical digestion. The equilibrium of both these aspects of feeding is necessary for an efficient digestion, and hence for a healthy lifestyle.