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How does the body obtain and utilise energy? Essay

The cardiovascular system

The myocardium, commonly referred to as the heart, acts as a pump for transporting blood around the body via a collective system, known as the cardiovascular system. This system has various components; blood vessels; mainly arteries, veins and capillaries. The cardiovascular system has four main functions within the body. Firstly to transport dissolved oxygen, hormones, nutrients, salts, enzymes and urea to cells located around various places within the body, whilst at the same time eliminating any waste products such as carbon dioxide and water. Secondly, to protect the body from infection and blood loss.

Thirdly, to distribute heat around the body to enable a healthy temperature of 37oc and finally to aid the body to maintain fluid balance. This ‘human pump’ can be regarded as two pumps. The fist sized organ contains two muscular chambers; the upper chamber; the atrium and the lower; the ventricle. The right side of the heart pumps deoxygenated blood from the veins to the lungs for oxygenation, whilst the left side pumps oxygenated blood from the lungs to the body. It is important to note that the two sides are separated by a septum. The blood flows through the heart twice within one cycle, this is known as ‘double circulation’.

The cardiovascular system carries oxygen and glucose to the cells and transports waste products such as co2 and urea away from the cells and to other parts of the body, such as the lungs and kidneys. Adenosine triphosphate, also known as ATP, is a chemical energy that is produced when nutrient molecules are burnt. ATP is constantly being produced on a daily basis due to the breakdown of glucose. Glucose is a sugar which is the main source of energy for the body. Glucose is broken down and the energy from the glucose molecule chemical bonds are released and utilized by the cell to produce ATP molecules. Catabolism is a metabolic action that breaks down more complex molecules, such as lipids and proteins and transforms them into simpler molecules, such as fatty acids and amino acids in order to release energy. The breakdown of food allows energy to be released as the foods

molecules’ bonds are breaking. This energy is then utilized to refine the bonds that have been broken to enable an increase of ATP to be created. More energy can be produce when oxygen is present. An aerobic production of ATP takes place within the mitochondria. The broken down food molecules enter the blood stream. The blood is a liquid which is made up of red and white cells.

The red blood cells are attached to a protein called hemoglobin, (which is responsible for giving blood its red appearance) oxygen is present within these red blood cells. Glucose is dissolved in the plasma. Plasma consist of water, fats, proteins and salts. Plasma is responsible for transporting blood cells throughout the body and nutrients i.e. glucose, It also transports waste products, antibodies, clotting proteins and hormones. Iron is also present within red blood cells and iron attracts oxygen. The cells require oxygen to produce energy.

The body would not receive the nutrients it needs if the cardiovascular system was not in place, therefore it is essential. The cardiovascular system is dependent on metabolic reactions. The heart itself needs ATP to function therefore the CV system would not work without the products of metabolism.

The digestive system

The digestive system consist of various organs such as, the pancreas, stomach and gall bladder, which all work together to convert food into energy and to extract the vital nutrients that the body requires to function efficiently. The digestive system has several components which all have their own duties to carry out in order to break down the food step by step. Although digestion has several steps there are two main forms of digestion that these steps fall into. The first form being; mechanical digestion. Mechanical digestion involves physically breaking the food into smaller pieces by chewing. The second form being; chemical digestion. This involves breaking down the food into simpler nutrients with the assistance of digestive enzymes such as, proteins, carbohydrates and lipids. Digestive enzymes are proteins that break up large molecules of food into smaller molecules to enable them to be absorbed and used by the cells in the form of nutrition.

The digestive tract plays a vital role within the digestive system, it is a tube that is responsible for passing the food to be further broken down. It consist of; the mouth, pharynx, esophagus, the small and large intestines and the anus. The other organs that work within the digestive system include; teeth, tongue, three pairs of salivary glands, the liver, the pancreas and the gall bladder. The teeth cut and grind the food in order for it to be swallowed, the salivary glands also produce and secrete salvia to aid the swallowing. As stated before there are three salivary glands which all carry out a different function; the parotid, which produces amylase in order to digest the carbohydrates. The submandibular provides mucin as a form of lubrication for the food bolus to travel down the esophagus to the stomach. Finally, the submandibular which secretes mucus. The tongues job is to roll and mix the food into a formulae known as bolus, which consists of small pieces of mashed up food.

Once the bolus is made, the tongue pushes it towards the pharynx and into the esophagus during the process of swallowing. The esophagus takes the food down to the stomach. The stomach is where the food is churned and mixed together with gastric fluids, such as enzymes and hydrochloric acid secreted by the stomach walls to make a paste like substance known as chyme. The alimentary canal is the small intestine. The alimentary canal is a tube that flows from the mouth to the anus. It consist of three parts; the duodenum, the jejunum and the ileum. The duodenum is attached to the stomach and is majorly involved in the breaking down process. Digestive enzymes are secreted by the pancreas to the duodenum. These enzymes are responsible for breaking down proteins, fats and carbohydrates.

The pancreas also performs the role of producing insulin, which is the main hormone responsible for metabolizing sugar, secreting it directly into the bloodstream. The jejunum and the ileum absorb the nutrients into the bloodstream. Contents of the small intestine initially begin semi-solid and transform into complete liquid form after passing through the organ. Water, bile enzymes and mucus are responsible for the change in consistency. The villi are vital for the absorption of digestive nutrients. The cells of the villi transport the food from the digestive tract into the bloodstream where the body can utilize them efficiently. The villi increase the surface area of the small intestine, they also contain specialized cells which transfer various types of nutrients into the blood. The liver then takes over and processes the absorbed nutrients from the small intestine.

Liver also secrets bile into the small intestine which aids in the digestion of fats. There is a muscular tube known as the colon, which provides a pathway from the small intestine to the rectum. The large intestine plays a crucial role within the digestive system, it is responsible for processing waste which allows the emptying of the bowels to be easy and efficient. Undigested food is transferred from the small intestine to the large intestine. Once in the large intestine water is reabsorbed and undigested food and fibre are eliminated.

After this process the food waste products harden and turn into faeces. Which are finally excreted via the anus. Once food has completed the process of digestion and has completely broken down, energy is provided to enable physical activity from walking to talking, from sports to working. Food provides the energy that is essential for everyday tasks. It also provides energy for involuntary activities such as, thinking, breathing, nerves, organs (especially the heart) to carry out their functions and the ability to build and repair tissues.

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