Discuss about the Digestive System of Humans for Protein Digestion of Human Body?
The food that we eat is acted upon by a group of organs together that helps in converting food into body energy and nutrients while feeds the entire body to grow and develop. This process is known as digestion and all the organs that help in digestion together constitute the digestive system of the body.
In the initial step, food from mouth enters a long tube called the alimentary canal or the gastrointestinal (GI) tract which is a combination of few parts like oral crater pharynx, throat, stomach, small intestine and large intestine. There are few accessory organs also that play an important role in digestion of food for e.g. teeths, tongue, saliva glands, liver, gallbladder and pancreas. (Taylor, 2015)
Mechanism
When we eat food items like meat, fried chips, junk food, vegetables etc. which are not in form that body can use for its nourishment, therefore these needs to be first broken down into smaller molecules before getting absorbed and entering the blood stream. The process of digestion work upon it to mix it well with fluid and juices, break it into smaller parts and move it along the gastrointestinal pathway. (Dummies, 2016)
Gastrointestinal tract
The gastrointestinal tract is a series of organs linked together after each other to perform a specific function in the process of digestion. These include- mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus. Apart from given names, few necessary organs that support the process in breaking it down into smaller portions are-teeth and tongue, salivary glands, gall bladder, liver, pancreas.
Gastrointestinal tract
Process of digestion
This complete process is carried out with the help of muscles that are present along the walls of organs to facilitate its movement in the downward direction. Complex movements of organs like esophagus, stomach and intestines is known as peristalsis. Peristalsis is a sequence of spontaneous reactions-like muscle contractions which move food along the digestive tract.
Peristaltic movement of walls of intestine
Peristaltic movement helps in pushing the food and liquid forward towards the hollow organs with the supporting action of muscle contraction and relaxation. (Dennett, 2015)
First, food from the mouth enters the esophagus or the food pipe and soon the working of muscles start which is involuntary in nature. Its acts as a passage and prevents back flow of food with the help of a valve at its both ends. Food then passes into the stomach and is received by soft smooth muscles in its upper part.
Secondly, the stomach first receives the complex food form like large pieces of chicken, chips etc, then breaks it and mixes it with liquid and juices secreted by the stomach itself and then finally propels it to the large intestine through a small curved pipe-like structure known as duodenum. In the stomach only partial digestion takes place which is further carried out in the intestines. Along with the peristalsis there are certain other kinds of movements seen in the walls of the intestine such as segmentation and pendular movements. These pendular movements are done by the longitudinal muscles of the intestinal wall which are responsible for contracting and relaxing the walls.
Pendular Movements of the Intestinal Wall.
It is because of such type of movements that the food, get mixed up thoroughly with the digestive juices and processes next into the intestines to complete the process of digestion. When the food gets churned up by the stomach walls and degraded by juices produced by the stomach that were initially eaten as meat, chips and other things is now turned into a thick soupy mass called, chyme. The useful nutrients that are absorbed by the specialized cells in the lining of intestines grab sugar, fatty acids, amino acids, vitamins and minerals back into the body for energy and growth. These extracted nutrients may also serve as building blocks for newer tissues to develop.
The complete and complex process of digestion is governed with a series of enzymes, juices, muscles, organs etc which all work together to get the complex food digested completely in a messy way and ends up with the discharge of waste and unwanted stuff from the body in the form of faeces.
News letter
hemical digestion is a progression by which the food taken by a human body is reduced to a minimal size where the nutrients from the food can be absorbed easily in the blood stream with the help of certain enzymes, saliva and digestive juices. When the food reaches the mouth, the hormone system gets triggered and starts releasing enzymes which help in digesting the food particles. There are proteins, carbohydrates, fats, lipids etc found in the food which gets digested separately, each in a different manner. Most of the protein is broken down by the enzyme called pepsin. An enzyme amylase helps in the digestion of carbohydrates, which begin in their mouth in the very early stage. These initial stages of digestion can last for several hours depending on different species but it generally lasts for one to two hours in humans. (Geek, 2016)
Digestion of proteins
The digestion of proteins begins in the stomach body parts and finishes in the small intestine with the help of enzyme pepsin (protease in gastric juice) and nerve signals. The breakdown of proteins occurs at different sites- stomach, duodenum and SI. Here proteins are first broken down into polypeptides, then to peptides and finally these peptides break into amino acids. (Annigan, 2016)
Chewing protein rich food, especially the tough ones like meat or whole grains allows the digestive process to occur at a more rapid speed. The food when enters the stomach gets exposed to a harsh acidic environment which denatures proteins so that enzymes can act on it, and also inactivates any harmful micro-organisms ingested along with the food.
The protein when broken into peptide in the stomach now moves to the small intestine where a neutral (Ph) environment encourages activity of protein-digesting enzymes. These help in further breakage of peptides into amino acids. The amino acids gets absorbed into the blood and passed to the liver from where they get distributed throughout the body. These usable amino acids act as nutrients available to cells and helps in muscle continuation, support immunity function, red blood cell formation, hormone synthesis and tissue repair.
Digestion of carbohydrates
The digestion of carbohydrates starts from the mouth. The consumed food is first moisturized with saliva secreted by the salivary glands, where an enzyme salivary amylase is released to split the polysaccharides present in the carbohydrate food.
After the food is chewed into smaller pieces, it will be swallowed and passed through the esophagus into the stomach. This paste of food is known as chyme. The acids produced in the stomach demolish the bacteria available in the food and also stops the action of salivary amylase .
Pancreatic amylase, an enzyme released from the pancreas breaks these polysaccharides into a disaccharide in which only two sugars are linked together. Further, the enzymes lactase, sucrose and maltase (enzyme secreted by small intestine) act together and result in the breakdown of disaccharide into monosaccharide. These are single sugar molecules which get easily absorbed into the blood stream. (Kaiser, 2016)
The leftover undigested carbohydrate reaches the colon (large intestine) and gets broken down by the bacteria present in the intestinal walls and turns it into fiber which is finally expelled out of the body in the form of faeces.
Digestion of lipids
Like carbohydrates and proteins, lipids also need to be broken down into smaller components for easy absorption. These are generally large and are not soluble in water. Their digestion starts in the mouth where they act with saliva and start the process of emulsification, facilitated by the action of enzyme lingual lipase. As a result of this the fat particles gets converted into tiny droplets and separates from water components present in the mixture.
After the passage of food from mouth into the stomach, through the esophagus, gastric lipase breaks down triglycerols into diglycerides and fatty acids. The fat molecules gets dispersed by the contraction and churning movements of the stomach and results in further emulsification of these diglycerides. A very small quantity of fat digestion occurs in the stomach during the process.
In the small intestine, the separated fat combines with the watery fluids of the intestine with the help of bile. Bile contains bile salts, cholesterol constituents and lecithin. Once pancreatic lipase enters the small intestine, it further breaks fats available into free fatty acids and monoglycerides. Here they are wrapped around with the bile salt to form micelles thus releasing fat compounds into the cells of digestive tract lining.
Essay on Metabolism of products of digestion
The nutrients when digested thoroughly in the gastrointestinal tract gets absorbed into the blood stream and reaches the hepatic portal system which helps in transporting it to the liver for the further process. This is a result of a diffusion process which allows the smaller particles to cross the membrane lining from a region of their higher concentration to the region of their lower concentration, and thus reach the capillary from where they enter the hepatic portal system easily.
From the liver, all the glucose gained travels to each and every cell of the body (which is basically the prime of energy to the body) and this function is carried out with the help of insulin which is highly responsible for the uptake of glucose into the cells. Further, the metabolic breakdown of glucose occurs which is known as glycolysis (glycol-glucose: lysis-breakdown) that takes place in nearly all the tissues. This helps in converting glucose into pyruvate which is acidic in nature. Similar to glycolysis a more complex process called fructolysis (fructo-fructose: lysis-breakdown) also occurs which is the metabolism of fructose which occurs only in the liver.
Both these processes of glycolysis and fructolysis result in aerobic or anaerobic respiration which produces high quantity of energy to meet the demands of body. Apart from providing energy to the body there is a storage system also available so that energy saved can be used at any point of time whenever required. In this, the glucose molecules gets linked together through strong chemical bonds and form long chains and gets stored in the liver and muscles fibers. These can be hydrolyzed back into glucose at the time of need especially between meals or when the sugar levels are low during long hours of sleep. This process is known as glycogenesis. (Wang, 2005)
The digestion of proteins, carbohydrates and lipids occurs at a result of metabolism which chiefly refers to those chemical reactions that occur while breaking complex molecules into simpler structures so that they can be digested easily. All metabolic reactions that take place can be categorized into two main types that are anabolic and catabolic reactions. When the bigger particles are broken down into smaller ones accompanied with the release of energy, such type of processes are said to come under catabolic reactions, whereas, when this released energy is used by the body for performing various tasks, for warming body and also for developing new molecules for growth and repair, such processes come under anabolic type of reactions. Reactions are necessary to occur as bigger molecules are unable to cross the membrane barrier of the cells therefore can result in decreased digestion and absorption. To utilize the released energy in a proper way by all the cells of the body for better functioning and development, anabolic reactions are very likely to occur. In other words we can say that a complete set of reactions that takes place to complete the various stages in the process of digestion is said to be as metabolism. (Wright, 2004)
Conclusion
In the above stated text, we have discussed about how complex food particles like chicken, chips fried in batter and coke gets digested in the human body and move along the gastrointestinal pathway. The process of digestion is distributed evenly to all the organs involved in the digestive process. The muscles and the juices secreted by these organs play a very important role in digestion and its metabolism. The digestion of carbohydrates, fats and lipids is a complex phenomenon which involves breakage of larger particles into the smaller ones with the help of enzymes, chemical reactions and juices. After the products gets completely digested their metabolism starts which results in the diffusion of gained products into the cells to release energy and provide it to the individual at the time of need. But the fat rich products provide less energy as they are high in cholesterol level and increase the deposit of fat in tissues.
References
Annigan J., (2016). https://healthyeating.sfgate.com/protein-digestion-inside-human-body-6044.html- Protein Digestion inside the Human Body by Jan Annigan,Dennett C., (2015).
How Does the Body Digest & Metabolize Fat? Last Updated: May 23, 2015 | By Carrie Dennett www.livestrong.comGeek W., (2016). What Is Chemical Digestion? https://www.wisegeekhealth.com/what-is-chemical-digestion.htmHandbook of Functional Lipids (Functional Foods and Nutraceuticals). (2006). Food Nutr Bull, 27(2), pp.188.1-188.
https://bk.psu.edu/clt/bisc4/ipweb/misc/…/digestive/Digestion_Absorption.pdf
https://ISSFAL (International Society for the Study of Fatty Acids and Lipids). 2004. Recommendations for intake of Polyunsaturated Fatty Acids in Healthy Adults. ISSFAL 2004, UK (www.issfal.org)
Jamerson A., (2016). The Digestion & Absorption of Sucrose by Ann Jamerson, Demand Media https://healthyeating.sfgate.com/protein-digestion-inside-human-body-6044.html
Kaiser S., (2016). What Are the Steps to Digestion for Carbohydrates? By Sara Kaiser https://healthyeating.sfgate.com/protein-digestion-inside-human-body-6044.html
Steyn, N.P., Maunder, E., MacIntyre, U., Gericke, G., Swart, R., Huskisson, J., Dannhauser, A., Vorster, H.H., Nesmvuni, A.E. & Nel, J.H. (2005). Public Health Nutr., 8(5): 533-543.
Taylor, t. (2016). Digestive System.InnerBody. IFFGD publication #190. From NIH Publication No. 04-2681, May 2004, (2016). https://www.innerbody.com/image/digeov.html
The Human Digestion Process (or, W. (2016). The Human Digestion Process (or, What Happens after You Eat Food). Dummies.com. Available https://www.dummies.com/how-to/content/the-human-digestion-process.html
Wang, H.J., Hu, Y.S. & Yang, X.G. 2005. The status and trend for dietary pattern of energy, protein and fat in Chinese residents. Acta Nutrimenta Sinica, 27(5): 358-365.
Wright, J.D., Kennedy-Stephenson, J., Wang, C.Y., McDowell, M.A. & Johnson, C.L., (2004). Trends in intake of energy and macronutrients – United States, 1971–2000. MMWR., 53(04): 80-82.
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