eassy on process of digestion
Answers
Digestive Processes. The processes of digestion include six activities: ingestion, propulsion, mechanical or physical digestion, chemical digestion, absorption, and defecation. The first of these processes, ingestion, refers to the entry of food into the alimentary canal through the mouth.
Answer:
The digestive system is uniquely constructed to perform its specialized function of turning food into the energy and extracting nutrients necessary to sustain life. It does this by breaking down food into its basic nutrients, which include vitamins and minerals, fats, carbohydrates, proteins, and water, before transporting them to the small intestine, where most of the nutrients are absorbed into the body. The digestive system takes place in the alimentary canal, a tube that runs from the mouth to the anus and includes the esophagus, stomach, small intestine, and large intestine, colon, and rectum. The liver and pancreas also contribute to digestion but are not part of the alimentary canal.
Digestion begins in the mouth, where chemical and mechanical digestion occurs. Food enters the mouth and is chewed by the teeth, turned over, and mixed with saliva by the tongue. The sensations of smell and taste from the food set up reflexes which stimulate the salivary glands, saliva is produced by the salivary glands and is released into the mouth. Saliva begins to break down the food, moistening it and making it easier to swallow and contains a digestive enzyme called amylase which breaks down the carbohydrates (starches and sugars). One of the most important functions of the mouth is chewing. Chewing breaks the food into pieces and allows food to be mashed into a soft mass that is easier to swallow and digest later. Movements by the tongue and the mouth push the food to the back of the throat for it to be swallowed. A flexible flap called the epiglottis closes over the trachea to ensure that food enters the esophagus and not the windpipe to prevent choking.
Once the food is swallowed, it enters the esophagus, a muscular tube that is located between the throat and the stomach. Food is moved by peristalsis which pushes the food down through the esophagus to the stomach. The stomach is the widest part of the alimentary canal and acts as a reservoir for the food where it may remain for between 2 and 6 hours. The stomach has 3 main functions: to store the swallowed food and liquid; to mix up the food with various hormones, enzymes, including pepsinogen which begins the digestion of protein, hydrochloric acid, and other chemicals; and to slowly empty its contents into the small intestine. The wall of the stomach is impermeable to most substances, although it does absorb some water, electrolytes, certain drugs, and alcohol. At regular intervals a circular muscle at the lower end of the stomach, the pylorus opens allowing small amounts of food, now known as chyme to enter the small intestine.
Most digestion and absorption of food occurs in the small intestine. The small intestine consists of 3 parts: the duodenum, the jejunum, and the ileum. The small intestine has 2 important functions. First, the digestive process is completed here by enzymes and other substances made by intestinal cells, the pancreas, and the liver. Second, the small intestine absorbs the nutrients from the digestive process. The inner wall of the small intestine is covered by millions of tiny finger-like projections called villi. They increase the surface area for absorption and are richly supplied with blood vessels. After this, the waste products from the body are excreted out with the help of anal sphincter.