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The cardiovascular system Essay

The heart is a major organ in the body, this organ pumps blood around the body, through veins, capillaries and arteries. The blood carries oxygen to our cells and also carries waste products which include water and carbon dioxide, which are products of respiration. Blood also helps spread out salts, enzymes, urea, nutrients, hormones and heat across the body.

The structure of the heart

The heart is located between lungs and it is protected by the rib cage, it is thought to be the same size as a closed fist. The heart is protected a membrane called pericardium, this membrane contains a film of fluid which helps prevent fiction. Each side of the heart consist of an atrium and a ventricle. The right side of the heart carries deoxygenated blood through the veins to the lungs, and the left side of the heart pumps oxygenated blood through the arteries around the body. The heart is separated by a septum. “Each of the four heart chambers has a major blood vessels entering or leaving it. Veins enter the atria, and arteries leave the ventricles” (Strech, Beryl; Whitehouse, Mary;, 2010) The pulmonary circulation is the circulation to and from the lungs. The pulmonary artery carries deoxygenated blood this leaves the right ventricle to go to the lungs and the blood is separated between the two lungs and the pulmonary blood then carries oxygenated blood and then enters the left atrium.

The main artery which is located leaving the left ventricle is called the aorta. The main vein which is located entering the right atrium is called the vena cava. The vena cava has two part (branches), these two parts are called the superior vena cava and the inferior vena cava. The superior vena cava returns blood from the neck and brain. The inferior vena cava returns blood from the rest of the body. The blood can only flow one way so there are 2 sets of valves which are between th atrium and the ventricles. These valves are called the right and left atrio-ventricular valves, but they also have old names, the mitral (left side) and the tricuspids (right side).

These valves are made up of flaps called cusps, and each cusp is very thin and this helps prevent them turning inside out. “They have tendinous cords attached to their fee ends and these are tethered to the heart muscles of the ventricles by small papillary muscles.” (Strech, Beryl; Whitehouse, Mary;, 2010) The tendious cords hold the valves in place. The semi-lunar valve is a valve that guards the exit of the pulmonary, the arteries and the aorta; this valve is very important because the blood is being forced into the arteries, the valve then stops the blood falling back into the ventricles. The Cardiac Cycle

“The cardiac cycle comprises the events taking place in the heart during one heartbeat.” (Strech, Beryl; Whitehouse, Mary;, 2010) There are different events in the cardiac cycle these are: The atria contracts and then pushes blood into the ventricles The atrio-ventricular valve is forced shut, because the ventricles are full of blood The semi-lunar valve is then forced open which is located in the pulmonary vein and aorta The arteries being to expand because the blood has been forced into the aorta and pulmonary vein The blood then leaves the ventricles

The atrio-ventricular valves are forced open with blood that is filling the atria When the ventricles are nearly full the cycle begins again. The heart is never empty; it is always full of blood, as well as that the cycle never ends.

Heart rate and stroke volume

“The cardiac output is the quantity of blood expelled from the heart in one minute” (Strech, Beryl; Whitehouse, Mary;, 2010) Stroke volume is the amount of blood expelled from the left ventricle in the heart and the beats of the heart is known as heart rate. An average heathy person has a stroke volume of 70cm and a heart rate between 60 and 80 beats per minute.

Blood pressure

When are heart pumps it is pumping blood around the body, as the blood is moving around the body it is pushing against the sides of our blood vessels, our blood pressure is the strength of the pushing. People who have high blood pressure are putting more strain on the arteries, and this could be dangerous because it could lead to things such as heart attacks and strokes. Blood pressure can be measured by a sphygmomanometer.

Blood Vessels

Pulmonary circulation is the circulation of the deoxygenated blood through the pulmonary arteries and oxygenated blood through the pulmonary veins. Each organ gets a supply of blood and this is because each organ has an arterial and venous. “The systemic circulation comprises all the blood vessels not involved in the pulmonary circulation” (Strech, Beryl; Whitehouse, Mary;, 2010)

Structure and function of the blood

“Blood transports materials around the body and protects against disease. It consists of cells, solutes and liquid. Blood is pumped away from the heart at high pressure in arteries and returns to the heart at low pressure in veins.” (BBC Bitesize, 2015) Our blood contains plasma, plasma is a liquid that contains dissolved substances, cells and cell fragments. The plasma contains red blood cells, these are to transport oxygen around the body, white blood cells, which help protect our bodies against diseases and Platelets which help the blood to clot.

Red blood cells –

Are small in size which help pass through narrow capillaries Contains haemoglobin which helps transport oxygen around the body Its flattened disc shape which give it a large service area Red blood cells do not contain a nucleus

Plasma carries many things around the body, including: Hormones, antibodies, nutrients and water substances.

Effects of cardiovascular system on metabolism

The cardiovascular system provides our cells with oxygen and nutrients, this is so we can get energy. The relationship between the cardiovascular system and metabolism is “inextricable”, we wouldn’t be able to get nutrients form out food, or oxygen from the air we breathe. The cardiovascular system has to provide oxygenated blood to the rest of the body at a constant speed and in order for this speed to maintain we need enough energy which has to be produced by the oxygen that is taken in for it to run.

The digestive System
The alimentary canal

The alimentary tube is the tube that extends throughout the body; it starts in the mouth and ends at the anus. Different glands have different roles in the process of digestion. The process start in the mouth where the salvia is mixed with the food and is rolled into a ball and swallowed, this process is called mechanical digestion and this is important because it is breaking down food in the first stages.

The salivary glands

There are three pairs of salivary gland in the mouth which produces saliva. Salvia is a digestion juice that contains an enzyme called amylase, which starts breaking down carbohydrates from the mouth throughout the body.

The oesophagus

The oesophagus which is also known as the gullet transports food from the mouth to the stomach, the amylase that is found in the salivary gland also carries on for a short period of time and the food is passed down by muscular contractions.

The stomach

The stomach is behind the rib cage, food is thought to stay in the stomach for up to 3 hours depending on what type of food that is consumed, food that is high in protein takes longer than meals that do not contain that much protein. “The strong stomach wall roll and churn the food around and pour on secretion from gastric glands. The resulting paste-like material is called chime.” (Strech, Beryl; Whitehouse, Mary;, 2010) The gastric gland produces many things, these include gastric juices, hydrochloric acid and protease. The pH of the stomach is 1-2. The goblet cells which are located in the epithelial lining of the stomach, the goblet cells produce a mucus which helps protect the lining of the stomach from acid erosion. “The stomach empties the chime in spurts into the duodenum through the sphincter, a thick ring of muscle that alternately contracts and relaxes.” (Strech, Beryl; Whitehouse, Mary;, 2010)

The Duodenum

The next part of the alimentary canal is the small intestines, the small intestines are not actually small in length but because there small in diameter. The first C part of the small intestines is called the duodenum, it is important in digestion as well as the liver and the pancreas because they pour there secretion juices into the area. The duodenum secrets juices that are called succus entericus which helps continue the process of digestion in carbohydrates, lipids, fats and protein.

The ileum

The rest of the small intestine is called the ileum. It is adapted in several ways, for example its long length, it can fold, it is covered in villi and the villi are covered in microvilli, these are all very helpful because they increase the surface area so that more nutrients can be absorbed.

The colon

At the bottom of the small intestines and the start of the large intestines there are remnants called the caecum and the appendix, neither of these remnants has a purpose. The large intestines contains the colon and the rectum. “The colon removes water, salt, and some nutrients forming stool. Muscles line the colon’s walls, squeezing its contents along. Billions of bacteria coat the colon and its contents, living in a healthy balance with the body.” (WebMD, 2015) The colon travels up the right side of our abdomens. Faeces contains, cellulose, dead bacteria and scraped-off cells from the gut lining and the reason why our faeces is brown because is because of the bile pigments.

The liver

The liver is very important because it cleans our blood, it produces bile and it stores energy in the form of a sugar called glycogen. Bile travels down the bile duct into the duodenum, before that the bile was stored in the gall bladder, bile does not contain enzymes but it does produce bile salts which cause the emulsification of fats in the duodenum.

The pancreas

The pancreas is located between the intestines and the stomach, to neutralise the stomach acid, the pancreas secretes pancreatic juices and alkaline slats, these neutralise it. “Pancreatic enzymes go to work on all three macronutrients and are important agents for the complete breakdown of complex food molecules into amino acids, glucose and similar simple sugars, fatty acids and glycerol.” (Strech, Beryl; Whitehouse, Mary;, 2010)

Breakdown and absorption of food materials

Ingestion is taking food in through the mouth, “food is generally composed of large complex moleclues of protein, carbohydrates and fats that would be unable to pass through the lining of the alimentary canal.” (Strech, Beryl; Whitehouse, Mary;, 2010) The complex molecules are turned into soluble molecules which then allows them to be absorbed, in the process of absorption. Waste products that cannot be absorbed will be passed through the anus, this term is called egestion.


Food and chime move through the alimentary canal, this process is called peristalsis, this is the contractions of two sets of muscles in the gut. One set of muscles lines the gut while the other circles it, they then contract and squeeze the food down. How does the digestive system work in relation to energy metabolism? The digestive system is a group of organs that breaks down food, once the food is broken down it provides energy to the body, we need this energy for many things such as physical activity. Food also provides our bodies energy so it can keep our organs active, and helps our bodies repair and build body tissues.

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