The effects of smoking on bodily systems.

As described in earlier posts smoking has a significant effect on several body systems. The major systems that are affected by smoking are the respiratory systems and cardiovascular systems.
It affects the respiratory system by coating the lungs with tar causing cells to mutate into cancerous cells resulting in lung cancer.
It can make the respiratory tract (bronchi) prone to infection(bronchitis) and cause emphysema.
Smoking increases the risk of heart disease as smoking causes plaque to build up in the arteries leading to atherosclerosis or hardening of the arteries. This in turn raises blood pressure increasing the risk of heart attack and strokes. Also smokers suffer from poor circulation due to blocked arteries and in extreme circumstances can lead to amputation of limbs.
Smoking can reduce the efficiency of the immune system and make us more susceptible to other illnesses.

Smoking can be attributed to a whole number of problems with body systems and cause them to break down and not function properly. The campaign to get people to quit is well intentioned and could save the NHS millions in smoking related diseases, however smoking is a hard habit to break and it will be some time before smoking is eliminated entirely.

Smoking, coronary heart disease and lung cancer.

Smoking is directly related to coronary heart disease. The toxins in cigarette smoke cause plaques to form in the arteries which leads to atherosclerosis. Smoking also increases blood pressure, increasing the likelihood of stroke. Congestive heart failure is closely liked to atherosclerosis and smoking.

In America 61 million people suffer from a form of cardiovascular disease. 2600 die every day due to coronary heart diseases. Coronary heart disease caused by smoking is the leading cause of death in America and has been linked with sudden cardiac death in both men and women.
Smoking related coronary heart disease is thought to contribute to congestive heart failure. 4300 Americans die from this disease every year.

People who smoke are at a much higher risk than those who don't. Clearly smoking is a huge contributor, if not the main source, for coronary heart disease.

Smoking causes 9 out 0f 10 cases of lung cancer. There around 39,400 people diagnosed with lung cancer in the UK every year. It is the second most common cancer in men and third in women in the UK but is the most common type of cancer worldwide.
Smoking causes 90% of lung cancer deaths as smokers are 15 times more likely to die from lung cancer than non-smokers.
Quitting smoking has a postive reducing effect on the liklihood of developing lung cancer. This can be seen on the graph below.

The graph clearly shows then benefits of quitting smoking and the relation to lung cancer. It also highlights the connection between smoking and lung cancer.

Smoking is the primary cause of lung cancer and is responsible for the most deaths worldwide when looking at cancer. Smoking is the primary cause of lung cancer, and if it is the cause of 90% per cent of cases then by eliminating smoking you could reduce lung cancer occurance by 90%, which would almost eliminate it.

References:

www.cancerhelp.org.uk/type/lung-cancer/about/lung-cancer-risks-and-causes

http://quitsmoking.about.com/od/tabaccostatistics/a/heartdiseases.htm

http://info.cancerresearchuk.org/cancerstats/types/lung/riskfactors/index.htm

Diet, blood pressure, cholesterol and circulatory disease.

Diet, blood pressure, cholesterol and circulatory disease are all connected. A poor diet can lead to high cholesterol levels which increases the chance of circulatory disease, such as atherosclerosis.
There are two types of cholesterol: LDL which is the harmful one and HDL which is the protective one. A diet rich in saturated fat will increase the level of LDL cholesterol in the blood. This means that it is more likely that fatty deposits will develop within the arteries, leading to circulatory problems such as atherosclerosis.

Atherosclerosis results in the narrowing of the arteries, this then causes more resistance to blood flow which in turn raises blood pressure, making the individual more prone to heart attacks and strokes.

The main contributing factors to high blood pressure and high cholesterol, apart from diet, are:
Lack of exercise
Obesity
Excess alcohol
Diabetes
Gender
Age
Genes

A poor high fat diet will increase cholesterol which in turn raises blood pressure and as a result will put you at a much higher risk of suffering from circulatory disease. On the other hand a balanced low fat diet can reduce cholesterol levels and blood pressure thus, lowering the chances of suffering from circulatory disease.

References:
www.patient.co.uk/health/High-Blood-Pressure-(Hypertension).htm

www.bhf.org.uk/Keeping_your_heart_healthy/preventing_heart_disease/cholesterol.aspx

Changes in artery stucture associated with circulatory disease.

Peripheral artery disease affects the arteies that carry blood from the heart to the rest of the body. This condition causes the arteries to narrow which restricts blood flow to the limbs and muscles.

Peripheral artery disease usually affects the legs causing pain that can come on while walking.

Peripheral artery disease is caused by fatty deposits building up on the inside walls of the arteries. This is known as atherosclerosis. The fatty deposits cause arteries to narrow which restricts blood flow to tissues. This can cause pain in muscles, especially when exercising, as the muscles cant get enough blood and therefore not enough nutrients to function properly.

Atherosclerosis increases the risk of heart attack and stroke.

Other diseases that can cause change in arterial structure are called aneurysms. An aneurysm is an abnormal bulge in a blood vessel and occur most commonly in the aorta. Atherosclerosis can lead to an aneurysm and an aneurysm is more likely to be the site of fatty deposits. Most of the time aneurysms are small but sometimes, if they get big enough, they can burst which would requie immediate medical attention.

References:

http://hcd2.bupa.co.uk/fact_sheets/html/peripheral_arterial_disease.html

www.medicinenet.com/vascular_disease/article.htm

Mechanisms for regulating ventilation and pulse rates.

Ventilation rate is controlled by the medulla and the pons in the brain stem. The activity of this centre is stimulated by peripheral chemoreceptors, which are located in the aorta and carotid arteries.
Chemoreceptors are specialised nerve cells that monitor the pH of blood. They measure the pH of blood by detecting hydrogen ion concentration, the higher the concentration the more acidic the blood. Chemoreceptors also monitor carbon dioxide levels in the blood. It is carbon dioxide that influences the amount of hydrogen ions in the blood.
When levels of carbon dioxide and hydrogen ions become high the chemoreceptors stimulate the respiratory centres to speed up so that the excess carbon dioxide and hydrogen can be removed from the blood.

The pulse rate is regulated by by the sino-atrial node. This specialised group of cells are responsible for generating the electrical impulses that makes the heart contract.
Like ventilation rate pulse rate can be affected by chemoreceptors. An increased ventilation rate usually goes hand in hand with increased pulse rate. This is because the blood needs to travel faster in order to get to the lungs so that carbon dioxide can be exhaled. An increase in ventilation rate will stimulate the SA node to increase its rate of fire thus increasing the pulse rate.

References:
www.howstuffworks.com/lung3.htm

Cardiac Output

Cardiac output is the amount of blood pumped by the heart per minute and is measured in millilitres of blood per minute. In order to calculate cardiac output you have to times stroke volume (millilitres per beat) by heart rate (bpm).
The average person will have a stroke volume of about 70ml/min and a heart rate of 70bpm, cardiac output would be as follows:

70 x 70 =4,900ml of blood per minute.

This means that 4,900 ml of blood is being pushed out of the left ventricle per minute, which is equivalent to how much blood an average person has in their circulatory system. This measurement is a normal person at rest. During exercise cardiac output can increase up to 7 times.

Cardiac output is a measure of the amount of blood pumped around the body every minute. Blood carries all the essential nutrients that the body needs to function. If cardiac output is low then it could be a sign of cardiac disease, and as a result the body will not be getting the nutrients it need to function properly. This makes measuring cardiac output an important indicator of potential cardiac health problems.

References:
www.biosbcc.net/doohan/sample/htm/COandMAPhtm.htm

Electrical Activity of the heart.

The heart has a specialised natural pacemaker known as the sino-atrial (SA) node. The sino-atrial node is responsible for making the heart beat and regulating the cardiac cycle. The heart is the only organ that acts independently of the brain, the SA node generates its own nerve impulses.

The SA node is located in the upper portion of the right atrium and when it sends an impulse it sets off a chain of events.

When it first fires, the electrical impulse travels across both of the atria making them contract, this forces blood within the atria to be pushed into the ventricles.

The impulse then moves to to the atrio-ventricular (AV) node, this is located just above the ventricles. The impulse is delayed for a brief period at the AV node. This delay allows the atria to empty the blood into the ventricles.

After the delay the impulse then travels throughout he ventricles via special pathways called purkinje fibres. This then stimulates the ventricles to contract forcing the blood out and into the pulmonary artery and the aorta.

This cycle happens around 72 times per minute.

References:

www.heartsite.com/html/electrical_activity.html

http://heratdisease.about.com/od/palpitationsarrhythmias/ss/electricheart.htm

Structure of the heart and the cardiac cycle.

The heart is made up of cardiac muscle and this muscle is called the myocardium. The heart is a pump that continuously pumps blood throughout the body. The picture below shows that there are four chambers to the heart. These chambers are:

Right atrium:
This is where deoxygenated blood returns to after it has been round the body. The blood returns via the superior vena cava (blood from the upper body) and the inferior vena cava (blood from the lower body). When the blood has filled the atrium it gets pushed in to the right ventricle via the tricuspid valve. This valve prevents blood from flowing back up into the atrium.

Right Ventricle:
This receives blood from the right atrium. Once the ventricle is full the heart contracts and pushes the the blood through the pulmonary valve and into the pulmonary artery (the pulmonary artery is the only artery in the body that carries deoxygenated blood). The blood is then pumped to the lungs where it is oxygenated before returning to the left atrium via the pulmonary vein.

Left Atrium:

This receives blood from the pulmonary vein. Blood that enters here has been oxygenated in the lungs and is ready to be pumped around the body. Once the atrium is full the blood is pushed down into the left ventricle through the bicuspid valve.

Left Ventricle:

The walls of the left ventricle are three times thicker than the right ventricle. This is because blood has to be pushed around the body and so requires a more forceful contraction. Once the blood has entered from the left atrium the bicuspid valve closes to stop blood flowing backwards. The left ventricle then contracts pushing blood through the aortic valve and into the aorta, where it then travels around the body providing oxygen and nutrients throughout the body before returning to the right atrium via the superior and inferior vena cava and starting the cycle again.

During the cardiac cycle there are two distinct phases. The diastole phase is where the heart is relaxed and fills with blood. The systole phase is where the heart contracts and pushes blood into the arteries.

Diastole phase:

During this phase the heart muscle is relaxed and the atrioventricular valves are open. Deoxygenated blood from the vena cavae fills the right atrium and oxygenated blood from the pulmonary vein fills the left atrium. A nerve impulse from the sinoatrial node causes the atria to contract, pushing the contents into the respective ventricles.

Systole Phase:

During this phase the atrioventricular valves are closed and the semilunar valves open. Nerve impulses from the purkinje fibres cause the ventricles to contract pushing the blood from the ventricles into the pulmonary artery from the right ventricle and into the aorta from the left ventricle.














References:


http://web.buddyproject.org/web019/web019/heart.html



http://biology.about.com/od/anatomy/ss/cardiac_cycle.htm

The structure of arteries, veins and capillaries.

Arteries are the blood vessels that carry blood away from the heart, they repeatedly branch off getting smaller and smaller. The small arteries are known as arterioles.
Arteries are made up of three layers. The outside layer is made up of fibrous connective tissue which connects to surrounding tissues, this acts as an anchor to help keep the artery in place as blood is pumped through at high pressure.
The middle layer is made up of elastic connective tissue and smooth muscle. This layer also has two sets of nerves, one to make the muscle contract and the other to make the muscle relax.
The inner layer consists of flat epithelial cells, which makes the inner lining of the arteries smooth, reducing friction between blood and lining.
Arteries, with the exception of the pulmonary artery, always carry oxygenated blood away from the heart to the rest of the body.

Veins are responsible for carrying deoxygenated blood back to the heart and lungs in order for it to be reoxygenated. There is less pressure from the heart so the middle layer of muscle is much thinner than in arteries. Veins in fact are collapsible tubes if not filled with blood. They also differ from arteries because they have semi-lunar valves, which prevents blood from flowing backwards.

Capillaries are microscopically small tubes that connect arteries to veins. They from capillary beds in different tissues around the body. Their walls are only one cell thick, they don't have connective outer layers or a middle layer of smooth muscle, capillaries are only made up of the endothelial layer, and are so small that blood cells can only pass through them in single file. The capillary beds are the site of nutrient transfer between blood and tissue cells. This is also where oxygen diffuses from the blood into surrounding tissue to be used in metabolic processes, and where waste from metabolic processes, such as carbon dioxide, diffuse into the blood to be carried away.


References:
www.ehow.com/about_5381728_structure-blood-vessels.htm

www.bcbuwc.ac.za/SCI_ED/grade10/manphys/vessel.htm

How Oxygen and Carbon Dioxide are transported by the blood.

Oxygen is carried primarily in red blood cells. When oxygen enters the blood stream it binds to iron atoms that make up hemoglobin, which then becomes oxyhemoglobin. Each hemaglobin molecule is capable of carrying four oxygen molecules.
Oxygen has to be transported from the lungs to tissues throughout the body. This means that oxygen needs to bind to hemoglobin in the lungs and then release when it gets to its destination. This occurs due to subtle changes in the pH and temperature of blood, allowing hemaglobin to 'catch' and 'release' oxygen at the right time.
Carbon dioxide is transported by red blood cells but in a different way to oxygen. Red blood cels contain an enzyme called carbonic anhydrase, this enzyme together with water converts carbon dioxide into bicarbonate. Bicarbonate is used to control the pH level of blood and is later turned back into carbon dioxide to be exhaled. Some corbon dioxide is dissolved directly into the blood and some is carried by the hemoglobin molecules but the majority of it is converted into bicarbonate.

References:
www.helium.com/items/763669-the-functions-of-red-blood-cells

The structure of a red blood cell and its function.

The primary function of a red blood cell is to carry oxygen from the lungs to tissues around the body, and after to transport carbon dioxide back to the lungs. In order for a red blood cell to carry out its function correctly it requires a unique structure. Red blood cells are approximately 6-8 micrometres in diameter and have a unique biconcave shape. This enables them to squash into the tiny capillaries throughout the body. If they were not able to do this then they would cause obstructions in the circulatory system.

Red blood cells contain a special protein called hemoglobin and it is this that oxygen binds to in order to be transported around the body.

Red blood cells, unlike other cells, contain no nucleus, this combined with their biconcave shape allows for a greater surface area and cytoplasmic volume making them extremely efficient at diffusing oxygen.

The life span of a red blood cell is about 120 days, after which they are retained by the spleen where they are phagocyted by macrophages.

References:

www.helium.com/items/763669-the-functions-of-red-blood-cells

www.funsci.com/fun3_en/blood/blood.hte#3

The compnents of blood and their function

Blood is made up of several different components each with a specific function. These components are:

Red Blood Cells (RBCs)

These give blood its colour. Their function is to transport oxygen throughout the body from the lungs and transport carbon dioxide back to the lungs so it can be exhaled.
The production of red blood cells is regulated by the kidneys. When the kidneys detect that there is a deficiency of red blood cells they release a hormone that stimulates the production of new red blood cells.
Red blood cells are produced within bone marrow.

White Blood Cells (leukocytes)

These are the cells that are responsible for fighting infection. Like red blood cells they are produced in the bone marrow. The body produces a substance known as colony stimulating factors, which encourage the production of white blood cells when they are needed.

Plasma

Plasma is the pale yellow liquid in which all blood cells are suspended. It contains red and white blood cells, antibodies and platelets. In addition to this it also contains proteins that help with clotting in order to seal blood vessels if they get cut.

Platelets

These are fragments of cells that work with the clotting proteins in the plasma to help stop bleeding.
Like red and white blood cells they are usually formed in bone marrow.


References:
American cancer society (2009), Blood and its components [on-line]
Available from: www.cancer.org/docroot/ETO/content/ETO_1_4x_Blood_And_Its_Compnents.asp

The Nervous System and Breathing

Breathing is regulated by the autonomic nervous system, specifically the medulla oblongata. The nerve cells in this centre automatically send signals to the diaphragm and intercostal muscles, making them contract at regular intervals. Another section of the brain involved in regulating breathing is the pons which has two control centres, the Apneustic centre which helps stimulate inspiration and the Pneumotaxic centre which inhibits the Apneustic centre, allowing expiration. Between these respiratory centres a regular rhythm is established so that the average person breaths 15 times per minute.

Breathing can be affected by the pH level of the blood. Chemoreceptors send signals to the medulla and this determines the depth and rate of breathing. At low pH levels the medulla becomes stimulated and this results in an increase in breathing rate. When pH levels are high there is a decrease in breathing rate due to a lack of stimulation.

Most of the time breathing is automatic, however other parts of the brain can override the medulla and pons to make breathing a conscious effort, such as when swimmers hold their breath or when breathing is controlled while meditating.

References:

http://people.hofstra.edu/sina_y_rabbany/engg81/breathingcoordination.html

www.cdli.ca/~dpower/resp/control.htm

The conditions necessary for effective gaseous exchange

In order for effective gaseous exchange to take place certain functions need to be fulfilled. During inspiration a number of things happen. The diaphragm contracts along with intercostal muscles to make room in the thoracic cavity for the lungs to expand. Air can then be drawn down the respiratory tract into the lungs. Upper respiratory infections such as the common cold or flu can inhibit inspiration by narrowing the respiratory tract.

Air that has passed through the upper respiratory tract has been humidified. This so that when it reaches the lungs it is easily dissolved in water before being diffused in to the blood stream.


Within the lungs themselves the conditions have to be in a constant state of balance. Gas exchange happens by diffusion, high concentrations of carbon dioxide in the blood diffuse into the alveoli where concentrations are lower. Oxygen concentrations are high in the alveoli and low in the blood.

Another important factor for gas exchange is pulmonary surfactant. This is produced by cells within the alveoli and consists of a mixture of lipids and proteins that reduces surface tension of the thin liquid film that lines each alveolus. (Sherwood 2007). The tension of this liquid is such that without the surfactant each alveolus would collapse in on itself.

In order for effective gaseous to take place effectively the entire respiratory tract needs to be functioning correctly and be free from infection. Any number of infections can cause this delicate system to function below optimum capacity.

References:

Sherwood L (2007), 'Human Physiology', From Cells to Systems
Thomson, Brooks/Cole

The Structure of the Respiratory System.

The respiratory tract begins at the nose. During inspiration air is drawn into the nasal cavity where it is warmed and humidified. The nasal cavity contains microscopic hairs known as cilia, there are also cells that produce mucus. Together these serve to trap dust, bacteria and other foreign particles that are in the air we breath and prevent them from reaching the lungs. The nasal cavity also contains a large number of capillaries in order to warm the air before it passes to the pharynx http://www.cdli.ca/~dpower/resp/struct~1.htm

From the nasal cavity air moves into the pharynx (throat) and then into the larynx. The larynx contains the vocal chords, and it is the act of air flow (expiration) across these that cause them to vibrate, enabling humans to make sounds for speech. The entrance to the larynx is blocked by the epiglottis, this prevents food and liquid from entering and diverts it down the oesophagus http://www.cdli.ca/~dpower/resp/struct~1.htm

The nasal cavity, pharynx and larynx are known as the upper respiratory tract. Their main function is to warm and humidify the air, as well as removing dust and bacteria from the air before it moves into the lower respiratory tract.

http://www.encognitive.com/node/1128

The larynx leads directly into the trachea. This is a tube approximately 12cm in length and 2.5cm wide. The trachea is kept open with 16 rings of cartilage that form a 'c' shape. Like the nasal cavity the trachea is lined with cilia which move mucus back to the pharynx http://www.bbc.co.uk/dna/h2g2/A27019505.

At the centre of the chest the trachea splits into the left and right primary bronchi. The right bronchus is wider than the left and is often where inhaled foreign objects end up. These two primary bronchi divide into secondary bronchi which divide further into tertiary bronchi, with eight on the left and ten on the right http://www.bbc.co.uk/dna/h2g2/A27019505.

These tertiary bronchi then split into a network of bronchioles each ending in an alveoli. This network is what makes up the lungs. Each lung is split into lobes with two on the left and three on the right. The reason the left only has two is because the heart sits on that side of the body.

Alveoli are tiny air sacs at the end of bronchioles, it is here that gaseous exchange takes place. Alveoli are only one cell thick, this is so that air can diffuse quickly into the blood stream. There are thought to be around 600 million alveoli in an adult human giving a surface area of 100 square meters. This provides a hugh area for gaseous exchange.http://www.bbc.co.uk/dna/h2g2/A27019505