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structure and function of the cardiovascular system

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sinead dollard

on 3 November 2013

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Transcript of structure and function of the cardiovascular system

Structure and Function of the Cardiovascular System
Structure - Tricuspid value , Aortic value, Pulmonary value and Aorta
The tricuspid value is situated between the right atrium and the right ventricles, it allows blood to flow from the right atrium to the right ventricles without backflow. The tricuspid is made up of the 3 valve leaflets, the annulus, the supporting chordae tendineae, and the papillary muscles.These "chords" help prevent hold the valve in place.

The aortic value is another one of the four values in the heart. The aortic value is situated between the left ventricle and the aorta, this prevents backflow from the aorta into the left ventricle. It is located at the base of the aorta. It opens to allow blood to leave the left ventricle as it contracts. When the ventricular muscles relax, the valve closes to prevent blood from backing up into the ventricular chamber.

The pulmonary value is another one of the four values in the heart. Its located between the right ventricle and the pulmonary artery, preventing back flow from the pulmonary artery. The pulmonary value is made up of three leaflets or cusps. It located at the base of the pulmonary trunk. This valve opens when the right ventricle contracts. When the right ventricular muscles relax, blood starts back up the pulmonary trunk, causing the valve to close to prevent the flow from returning into the ventricular chamber.

The Aorta is the bodies main artery. It originates in the left ventricles and carries oxygenated blood to all parts of the body expect the lungs. Three major arteries originate from the aortic arch: the brachiocephalic artery, which supplies blood to the brain and head; the left common carotid artery and the left subclavian artery.

Structure - Atria, Ventricles and Bicuspid value
The atria is located in the upper chamber of the heart. The upper chamber is split into two the right atrium and the left atrium. They receive blood returning to the heart from the body or the lungs. the right atrium receives deoxygenated blood from superior and inferior vena cava.These veins return blood that is low in oxygen from various sites in the body. A smaller vein, called the coronary sinus, also drains blood into the right atrium from the wall of the heart. The left atrium receives oxygenated blood from the left and right pulmonary veins. The left atrium receives most of its blood supply from the left circumflex coronary artery. Drainage of the veins is carried out, in part, through left atrium's oblique vein.

The ventricles are located in the lower chambers of the heart. The lower chamber is also split into two the right ventricle and the left ventricle. They are the pumping chambers of the heart, because of this they have thicker walls than the atria. The right ventricle pumps blood to the pulmonary circulation for the lungs and the left ventricle pumps blood to the systemic circulation for the body. The left ventricle has a much thicker wall than the right ventricle. It must force blood to all other parts of the body against a great flow of resistance, so the walls are stronger than that of the right ventricle. The right ventricle pumps blood a fairly short distance to the lungs.

The Bicuspid (mitral) value is one of the four values in the heart, situated between the left atrium and the left ventricle. It allows the blood to flow in one direction only, from the left atrium to the left ventricle. The bicuspid valve opens to allow oxygen-rich blood from the left atrium to enter the left ventricle. This same structure also is what prevents blood in the left ventricle from backing up into the left atrium.

Structure - Superior vena cava, Inferior vena cava, Pulmonary vein and Pulmonary artery
The superior vena cava is a vein that receives deoxygenated blood from the upper body to empty into the right atrium of the heart. The superior vena cava is one of the two major paths into which the veins from all parts of the body (except from the lungs back to the heart) converge to lead to the right atrium of the heart.

The Inferior vena cava is a vein that receives deoxygenated blood from the lower body to empty into the right atrium of the heart. The inferior vena cava is a large vein ascending through the abdomen. It collects blood from the hepatic veins, lumbar veins, gonadal veins, renal veins, and phrenic veins. These vessels usually drain regions that are supplied by arteries with corresponding names. The inferior vena cava enters the heart through the right atrium.

The pulmonary vein carries oxygenated blood from the lungs to the left atrium of the heart.

The pulmonary artery carries deoxygenated bllod from the heart back to the lungs. it is the only artery that carries deoxygenated blood. The right pulmonary artery is also known as the right branch of the pulmonary artery. It is a thicker artery, and a longer one, compared to the left pulmonary artery. The right pulmonary artery provides the right lung's blood supply; it runs down to the root of the right lung and from there it branches out into two separate arteries. These smaller arteries each transport blood to one of the lung's right lobes.The left pulmonary artery is also known as the left branch of the pulmonary artery. It supplies blood to the left lung; it runs down to the root of that lung and from there it branches out into two separate arteries. These smaller arteries each transport blood to one of the lung's left lobes.

Cardiovascular System
The cardiovascular system consists of the heart, blood vessels and blood. The circulatory system as it is also known, is the major transport system in the body, carrying food, oxygen and other essential products to all the cells within the body but also removes waste products and carbon dioxide from the body.
The human body is a double circulatory system. It comprises two separate circuits and blood passes through the heart twice. The circulatory system consists of two circuits that blood travels through; pulmonary and systemic.
The pulmonary circuit carries blood to the lungs to be oxygenated and then back to the heart. In the lungs, carbon dioxide is removed from the blood, and oxygen taken up by the hemoglobin in the red blood cells.
The systemic circuit carries blood around the body to deliver the oxygen and returns de-oxygenated blood to the heart. Blood also carries nutrients and waste.

Structure - Heart
The heart is the center of the cardiovascular system. It is situated in the left hand side of the chest beneath the sternum. The heart is about the size of an adults closed fist. It is a hollow muscular pump that drives blood into and through the arteries in order to deliver it to the tissues and working cells. Deoxygenated blood flows into the right side of the heart, which pumps it to the lungs to pick up oxygen. The deoxygenated blood is returned to the left side of the
heart which then pumps it around the body. The heart is surrounded by a twin layered ‘sac’ known as the percidium. The cavity between the layers is filled with pericardial fluid, which have the purpose of preventing friction as the heart beats. The heart wall is made up of three layers:
The epicardium; the outer layer, the myocardium; the strong middle layer that form most of the heart wall and the endocardium; the inner layer. The right side of the heart is separated from the left by a solid wall known as the septum, this prevents the blood the right side coming into contact with the blood on the left side. the heart is split up into four chambers two on the left and two on the right, these chambers function separately. the chambers on the right supply blood at a low pressure to the lungs via the pulmonary arteries, arterioles and capillaries, for gaseous exchange to take place. . Blood returning from the lungs containing oxygen, travels to the left side of the heart via the capillaries, venules and veins.
when the left chambers are full, it contracts simultaneously with the right side acing as a high pressure
pump. Oxygenated blood is supplied via the arteries, arterioles and capillaries to cells all around the body.
Oxygen is passes from the blood to the cells and then carbon dioxide which is a waste product is
taken away. The blood then returns to the heart via capillaries, venules and veins.

Blood Vessels

As the heart contracts, blood flows around the body in a complex network of vessels, these are: Arteries, Artioles, Capillaries, Venules and Veins. These maintain the bloods circulation throughout the body. The structure of these different vessels within the cardiovascular system are determined by their functions and the pressure of blood traveling through them. Blooding flowing through arteries appears bright red due to being oxygenated. As it continues moving through the capillaries it drops off oxygen and picks up carbon dioxide. By the time the blood reaches the veins it is much bluer due to the deoxygenating c02.

An artery is an elastic blood vessel that transports blood away from the heart. There are two main types of arteries: pulmonary arteries and systemic arteries. Pulmonary arteries carry blood from the heart to the lungs where the blood picks up oxygen. The oxygen rich blood is then returned to the heart via the pulmonary veins. Systemic arteries deliver blood to the rest of the body. The aorta is the main systemic artery and the largest artery of the
body. They have two main properties elasticity and contractility. They have a thick muscular
walls to carry blood at high speeds under high pressure. When the heart ejects blood into large
arteries, the arteries expand to accommodate the extra blood. The smooth muscle surrounding
the arteries enables them to increase and decrease in size when they need to. The contractility
of the arteries helps to maintain blood pressure in relation to blood flow. The arteries are largely
deep, except where they can be felt at a pulse point. Arteries branch off into arterioles that
deliver blood to the capillaries.

Blood vessels

Arterioles have much thinner walls than arteries. They control blood distribution by changing their size. Arterioles are essentially responsible for controlling blood flow to the capillaries. they are strong, have a relatively thick wall for their size, and contain a high percentage of smooth muscle. The structure of the arteriole is in form of a small diameter blood vessels that have tiny branches of arteries that lead to capillaries.

Capillaries form an network that connects arteries and veins by uniting arterioles and venules. They are the smallest blood vessels, they are narrow and very thin. They are very important as they allow diffusion of oxygen and essential nutrients that are needed by the body. Capillaries are so small that red blood cells can only travel through them in single file. Oxygen, carbon dioxide, nutrients and wastes are exchanged through the thin walls of the capillaries. Capillaries play an important role in microcirculation. Microcirculation deals with the circulation of blood from the heart to arteries, to smaller arterioles, to capillaries, to venules, to veins and back to the heart.
Capillaries surround muscles, ensuring they get oxygen and nutrients, so that
they can produce energy. The walls of these blood vessels are only one cell
think which allow nutrients, carbon dioxide and oxygen to be transferred.
Pressure in capillaries is higher than in veins but less than in arteries.

Blood Vessels
Veins return deoxygenated blood to the heart. They have thinner walls then arteries and
are quite big in size. By the time blood actually reaches the veins, the pressure is quite
low and blood is flowing slowly. Contracting muscles push the thin walls inwards to help
squeeze the blood back towards the heart. As muscle contractions are intermittent, there
are a number of pocket values in the veins that assist in preventing any back flow when
the muscles relax. veins are mainly close to the surface and can be seen under the skin.
they branch into smaller vessels called venules, which expand to the capillary network.
The smallest veins in the body are called venules. They receive blood from the arteries via
the arterioles and capillaries. The venules branch into larger veins which eventually carry
the blood to the largest veins in the body, the vena cava. The blood is then transported
from the superior vena cava and inferior vena cava to the right atrium of the heart.
The circulatory cycle
When the body (muscles) begins to exercise the muscles start to require oxygen. This leads to the blood becoming de-oxygenated. The deoxygenated blood starts by entering the heart by the vena cava: the inferior (lower body) and the superior (upper body). The two vena cava, collect the de-oxygenated blood. From the vena cava blood travels into the right atrium, then when full, pressure builds causing the tricuspid value to force open., letting the blood flow through to the right ventricle. The right ventricle then begins to fill, when full, pressure becomes great and forces the pulmonary value open, which send blood to the pulmonary artery so that de-oxygenated blood can be transported to the lungs from the heart to become oxygenated again.

Once the blood is oxygenated again, the pulmonary veins bring it back into the heart, into the left atrium. The left atrium fills up with oxygenated blood until the pressure is too much and pushes the bicuspid value (also known as the mitral value) open. This allows blood to flow into the left ventricle. The left ventricle is the bigger and stronger than all the other chambers. It pumps blood to the rest of the body so therefor need to have a better muscular wall than the other chambers. From the left ventricle, blood fills again until the pressure is high and pushes the aortic value open, which allows the blood to flow into the aorta, which is one of the main blood vessels. The aorta, carrying the oxygenated blood, sends the blood around the whole of the body to working muscles. The oxygenated is then used by these working muscles and the cycle starts again.

Functions of the cardiovascular system
Delivery of oxygen and nutrients - The key function of the cardiovascular system is to supply oxygen and nutrients to the tissues of the body via the bloodstream.

Removal of waste products - the circulatory system carries waste products from the tissues to the kidneys and the liver and returns carbon dioxide from the tissue to the lungs. Once the capillaries release the nutrients into the cell bodies, they then pick up cellular wastes. This waste consists of carbon dioxide, nitrogen and heat, and it is then transported via the veins to various other body systems in order to be expelled. For example, your body releases carbon dioxide from the lungs when you exhale. Nitrogenous waste, in the form of ammonia, urea and uric acid, is excreted by the kidneys as urine. And the body releases heat from the skin so that it maintains a constant temperature.

Thermoregulation - increased energy expenditure during exercises requires adjustments in the blood flow that affects the cardiovascular system. The cardiovascular system is responsible for the distribution of heat within your body to maintain thermal balance during exercise.For example, the cardiovascular system regulates body temperature by removing excess heat when the body is too hot, or by diverting more blood to vital organs and away from extremities when the body is too cold. Human enzymes usually work best at 37ºC, which is human body temperature. A part of the brain called the thermoregulatory centre monitors and controls body temperature. It gathers information as nerve impulses from temperature receptors in: the brain - these are sensitive to the temperature of the blood flowing there. Also the skin - these are sensitive to skin temperature. Extremes of body temperature are dangerous: high temperatures can cause dehydration, heat stroke and death if untreated. Where as low temperatures can cause hypothermia and death if untreated.

Functions of the cardiovascular system
During exercise the vascular portion of active muscles increases through dilation of arterioles, this is to allow more blood to an area. This process is called vasodilation. Vasodilation causes an increase in the diameter of blood vessels to decrease resistance to flow of blood to the area supplied by the vessels. This also causes more heat to be carried by the blood to the skin, where it can be lost to the air.

Vasoconstriction is when blood vessels temporally shut down blood flow to tissues, this increases blood pressure. It is the narrowing (constriction) of blood vessels by small muscles in their walls. When blood vessels constrict, blood flood is slowed or blocked. This reduces the flow of warm blood near the surface of the skin, and reduces heat loss. The process works by stopping a person from severe blood loss by restricting overall blood flow in a time of need, such as while sustaining an injury. It causes a decrease in the diameter of blood vessels. contraction of involuntary muscle fibres in the vessel walls increases resistance to blood flow.
Functions of the cardiovascular system
Oxygen transport
Exercise increases the demand for oxygen. The blood transports oxygen to all the parts of the body that require it. it also transports metabolic waste from cells to areas of disposal. Oxygen is carried around in the blood by red blood cells. Red Blood Cells are responsible for carrying oxygen and carbon dioxide. Red Blood Cells pick up oxygen in the lungs and transport it to all the body cells. After delivering the oxygen to the cells it gathers up the carbon dioxide and transports carbon dioxide back to the lungs where it is removed from the body when we exhale.

Fighting infection
blood contains and transports antibodies and white blood cells which help defend against viruses and bacteria. White Blood Cells help the body fight off germs. White Blood Cells attack and destroy germs when they enter the body. When you have an infection your body will produce more White Blood Cells to help fight an infection. proteins produced by the body when it detects an antigen. Antigens are any harmful substance to the body, usually bacteria, viruses, fungi, parasites and chemicals. Finally, platelets are the blood component that aid in the clotting process when you receive a cut to your skin.

When blood vessels are cut or damaged, the loss of blood from the system must be stopped before shock and possible death occur. clotting is a process where white blood cells form solid ‘barriers’. Damaged blood vessels walls are covered in a fibrin clot to assist repair of the damaged vessel. Platelets form a plug and the plasma components known as coagulation respond to form fibrin strands which help to strengthen the platelet plug. This stops bleeding.

Functions of the cardiovascular system
Function of blood
Blood provides the fluid environment for cells and is the medium by which
many materials are carried to and from these cells. Blood has four
principle constituents: plasma, red blood cells (erythrocytes), white
blood cells (leucocytes) of which there are different types, and platelets
or cell fragments (thrombocytes). Blood has a number of functions: distribution,
regulation and protection. The blood helps the body help a round about temperature
by absorbing and distributing heat. life- sustaining nutrients are transported from
the intestines to the liver and body cells, and waste products from the tissues
are transported to the kidneys. protective white blood cells, antibodies, hormones
and medicines are also transported in the blood.

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