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The Role of the Respiratory and Circulatory Systems in the Provision of Oxygen and the Removal of Carbon Dioxide from the Body

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The Role of the Respiratory and Circulatory Systems in the Provision of Oxygen and the Removal of Carbon Dioxide from the Body The purpose of breathing is to supply a continuous supply of fresh oxygen into the body and to remove carbon dioxide. Oxygen is essential for cells to function. Blood acts as the transport mechanism for gases to move between the lungs and tissues by passive diffusion. These gases will diffuse down their pressure gradient from areas of high pressure to areas of lower pressure. Atmospheric air contains approximately 79% nitrogen and 21% oxygen plus negligible amounts of water vapour, carbon dioxide and pollutants (Boyle & Senior, 2008). Air needs to enter and leave the body in a continuous, rhythmic pattern to sustain the body. Cardiac muscles rhythmically contract and relax to empty and refill the heart; respiratory muscles also act in a rhythmic pattern to fill and empty the lungs with air. These two actions are performed involuntary - the heart by means of a pacemaker and the respiratory muscles at a brainstem level. Specialised neurones called dorsal medullary respiratory neurones produce a cycle of activity that occurs every few seconds to establish the basic routine of respiration When air is breathed in, the external intercoastal muscles, of which there are eleven on each side of the body, contract and pull the ribcage upwards and outwards whilst the dome-shaped muscular diaphragm simultaneously contracts and flattens downwards by approximately 1cm in normal breathing thus pushing down the abdominal organs. This contraction is responsible for 75% of the air drawn into the lungs. As the diaphragm is attached to the lower ribs, its movement rotates the ribs into an increased horizontal position. A combination of these movements results in an increase in the volume of the chest which results in a decrease of pressure to a level below that of the atmosphere and thus air is forced into the body to equalise the pressure. ...read more.


The function of the left ventricle is to pump oxygenated blood around the whole of the body and for this purpose it requires a much thicker muscle structure than the right ventricle which only has to pump to the lungs. Separating the atria and the ventricles are atrioventricular valves which stop blood from flowing from the ventricles back up to the atria. The left valve has two flaps and is called the bicuspid (or mitral) valve, whereas the right valve has 3 flaps and is called the tricuspid valve. These valves are held in place by chordae tendineae attached to papillary muscles. These contract at the same time as the ventricles and thus hold the valves closed. The other vales within the heart are called semi lunar which guard the openings to the pulmonary artery and aorta and stop blood flowing back into the ventricles. These valves all ensure that blood only flows in one direction through the heart. The heart is composed of cardiac muscle with a thick wall of muscle separating the right and left cavities of the heart called an inter-ventricular septum. The cells that make up cardiac muscle are multinuclear and are called myocardiocyteal muscle cells. This type of cell is a capable of functioning without any conscious effort or additional stimuli; in other words it functions spontaneously. They are also specially adapted to resist symptoms of tiredness and for this purpose they have an unusually high number of mitochondria. Each chamber of the heart must be full of blood before a heartbeat can take place. This process occurs approximately 72 times per minute in the average person (buzzle.com). Initially, an electrical signal is received from the sino-atrial node (SA node or pacemaker) which is located in the wall of the right atrium. This signal causes the atria to contract simultaneously. Next, a second group of cells called the atrio-ventricular node (AV node) ...read more.


Environmental factors, such as air quality, can also contribute to the development of asthma. Symptoms occur due to the narrowing of the bronchi either by non-specific factors such as irritants within the atmosphere, e.g. smoke or pollution or from specific factors such as irritants from pet hair, pollen and certain medicines; e.g. aspirin. The membranes of the bronchi swell and produce an increased amount of mucus. Sufferers are generally born with a predisposition to asthma which is then triggered by one of the factors above. There is no cure, so any treatments taken are aimed at reversing the swelling of the bronchi and trying to prevent an attack. Bronchodilators relax the muscles within the airways and as their effects can be very quick acting, they give almost immediate relief from the symptoms. Anti-inflammatory medicine can be taken regularly to keep narrowing of the bronchi membranes to a minimum. Bronchitis is also a disease causing swelling of the lining of the bronchi. There are two different types, acute and chronic. In the case of acute bronchitis, viruses are to blame in 90% of cases, with bacteria accounting for the remaining 10%. Acute cases often accompany respiratory tract illnesses and are characterised by a severe cough plus one or more of the following: fever, nasal congestion or sore throat. Chronic bronchitis (or 'chronic obstructive pulmonary disease' as it is often called) is classified as a long-standing disease (symptoms have usually been present in excess of three months) and is mainly caused by smoking, although air pollution can be causative. The symptoms are very similar to those of acute bronchitis; however any mucus that is produced is often discoloured - having a yellow/green tinge to it. As viruses are to blame for the majority of acute bronchitis cases, antibiotics would be ineffective in trying to cure the disease. Instead, it can be alleviated by dealing symptomatically; in other words painkillers for any aches or sore throats and cough medicines to relive the cough. Patients with chronic bronchitis are advised to stop smoking immediately. ...read more.

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Some relevant information is included and the report addresses the role of the circulatory and respiratory systems in transport of oxygen and carbon dioxide, but far too much irrelevant information is included. There is a good use of references in the text, but a bibliography should be included at the end. The report ends abruptly without a summary To improve:
1)Exclude irrelevant details that do not contribute to answering the question
2)Make sure all key details are linked to the question the report addresses - how do all of the factors mention help maximise oxygen and carbon dioxide transport and exchange? Thisis often unclear.
3)Use key biological terminology throughout. The level is currently too basic for an A-level Biology report
4)Include a relevant summary paragraph at the end.

Marked by teacher Kerry jackson 07/02/2012

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