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Assignment 3: Cardiovascular system
Transcript of Assignment 3: Cardiovascular system
P5: Describe the structure and function of the cardiovascular system
M2: Explain the function of the cardiovascular system
Structure of the heart
The CV system is also referred to as the circulatory system. It is responsible for transporting oxygen, nutrients, hormones, and cellular waste products throughout the body, the cardiovascular system is powered by the body’s hardest-working organ — the heart.
The CV system consists of:
Blood Vessels (arteries, vein, capillaries)
The human circulatory system consists of two circulatory loops:
Pulmonary circuit - pumps deoxygenated blood from the
right side of the heart to the lungs, where the blood picks
up oxygen and returns to the left side of the heart.
Systemic circuit - pumps oxygenated blood from the left
side of the heart to all of the tissues of the body. The
systemic circuit removes waste products and carries
deoxygenated blood to the left side of the heart.
Location of the heart
The heart is at the centre of the CV system. It is located in the left hand side of the chest beneath the sternum and rib cage which provide protection.
An adult's heart is the size of a closed fist. The heart is a hollow muscular pump that drives blood into and through the arteries in order to deliver it to the working tissues and muscles.
Structure of the
The heart is surrounded by a twin layered sac known as the
. The cavities between the layers are filled with pericadrial fluid, whose purpose is to prevent friction as the heart beats.
The heart wall itself is made up of three layers:
(the strong middle layer that forms most of the heart wall)
(the inner layer)
The right side of the heart is separated from the left by a solid wall known as the
. This prevents blood on the right side coming into contact with the blood on the left.
The heart is divided into four chambers:
The two top chambers (the superior part of the heart) are called the atrium
The two lower (Inferior chambers) are called the ventricles.
The chambers on the right supply blood at a low pressure to the lungs via the pulmonary arteries, arterioles and capillaries, where gaseous exchange takes place. Here carbon dioxide passes from the blood to the alveoli of the lungs and oxygen is taken on board. This blood is the returned to the left side of the heart via the caperillaries, venules and veins.
When the chambers of the left side of the heart are full it contracts simultaneously with the right side, acting as a high pressure pump. It supplies oxygenated blood via the arteries, arteriols, and caperillaries to the tissues of the body such as muscle cells. Oxygen passes from the blood to the cells and carbon dioxide is taken on board. The blood then returns to the right atrium of the heart via the capillaries, venules and veins.
Task: Label the heart
Atria - the upper two chambers of the heart. It receives blood returning to your heart from either the body or the lungs. The right atrium receives deoxygenated blood from the superior and inferior vena cava. The left atrium receives oxygenated blood from the left and right pulmonary veins.
Ventricles - the bottom two chambers of the heart. The wall of the left ventricle is thinker because it has to pump blood around the body which requires a more forceful contraction. 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.
Atrioventricular valves - the purpose of these valves is to prevent blood from flowing in the wrong direction.
Tricusip valve - situated between the right atrium and the right ventricle.
Bicsupid valve - situated between the left atrium and the left ventricle
Following the movement of blood from the atrium, into the ventricle, the AV valve snaps shut which causes the first sound of the heart beat 'lub'
Pulmonary valves - prevent blood flowing in the wrong direction. These are located between each ventricle and the artery leaving the heart. They make the sound 'dub' the second sound of the heart beat.
Aorta - The body's main artery. It originates in the left ventricle and carries oxygenated blood to all parts of the body expect the lungs
Superior Vena Cava - A vein that receives deoxygenated blood from the upper body to empty into the right atrium of the heart
Inferior Vena Cava - A vein that receives deoxygenated from the lower body to empty into the right atrium of the heart
Pulmonary vein - Carries oxygenated blood from the lungs to the left atrium of the heart
Pulmonary artery - Carries deoxygenated blood from the heart back to the lungs. It is the only artery that carries deoxygenated blood
Flow of blood through the heart
Blood enters the heart from the superior and inferior vena cava
then to the right atrium
through the tricuspid valve
to the right ventricle
through the pulmonic valve
to the pulmonary artery
to the lungs
The blood picks up oxygen in the lungs, and then flows from the lungs:
to the pulmonary veins
to the left atrium
through the bicuspid valve
to the left ventricle
through the aortic valve
to the aorta
to the body
Task: draw the flow of blood through the heart
(deoxygenated blood in blue and oxygenated blood in red)
As the heart contacts blood flows around a complex network of vessels:
The structure of these different vessels within the cardiovascular system is determined by their different functions and the pressure of blood within them.
Blood flowing through the arteries is rich in oxygen and appears red, as the blood travels through the capillaries it drops off oxygen and picks up carbon dioxide. By the time it reaches the veins the blood appears blue as it is deoxygenated.
Carry blood away from the heart (always oxygenated apart from the pulmonary artery which goes to the lungs)
Have thick muscular walls to help carry blood under high pressure
Have elastic fibres that allow the artery to expand to accommodate blood ejected from the heart
Carry blood under high pressure
They do not requrie valves as the pressure remains so high
The arteries branch into arterioles that ultimately deliver blood to the caperilaies
Transport blood from arteries to capillaries
Arterioles are the main regulators of blood flow and pressure.
During exercise, muscles require an increased blood flow in order to get extra oxygen. To accommodate this, the diameter of arterioles leading to the muscles dilates. Other areas, like the gut, have their blood flow temporarily reduced to compensate for this, and the diameter of their arterioles is decreased.
The walls of arteriols are slightly thiner compared to the walls of arteries
They contain a high percentage of smooth muscle
Capillaries form an extensive network that connects arteries and veins by uniting arterioles and venules.
Found in the muscles and lungs
They are the smallest of all the blood vessels, one cell thick which allows nutrients, oxygen and waste products to be transferred.
Where gas exchange takes place. Oxygen passes through the capillary wall and into the tissues, carbon dioxide passes from the tissues into the blood
The pressure of blood within the capillaries is higher than that in veins, but less than in arteries.
The number of capillaries in muscle may be increased through frequent exercise.
Carries blood to the heart (always de-oxygenated apart from the pulmonary vein which goes from the lungs to the heart)
Have thin walls
Have larger internal lumen
Blood flow is slow and under low pressure
Have valves to prevent blood flowing backwards
They branch into smaller vessels called venules, which extend to the capillary network.
Venules are tiny vessels that drain blood from capillaries into veins.
Venule walls have three layers
Venules have thinner walls than arterioles
Function of the cariovascular system
Function of the cardiovasular system
The key functions of the cardiovascular system:
Deliver oxygen and nutrients to the body
Remove waste products
The key functions of the blood:
Delivery of oxygen and nutrients
The cardiovascular system works in conjunction with the respiratory system to deliver oxygen to the tissues of the body and remove carbon dioxide. In order to do this effectively the cardiovascular system is divided into two circuits, known as the pulmonary circuit and the systemic circuit.
Nutrients such as glucose from digested carbohydrate are delivered from the digestive tract to the muscles and organs that require them for energy.
Removal of waste products
Blood also absorbs the waste products made by cells, and transports them to the excretory organs (kindneys or lungs) for removal from the body.
When we are too cold the blood vessels supplying warm blood to the skin become narrow or constrict (vasoconstriction). This reduces the flow of warm blood near the surface of the skin, and reduces heat loss.
This is why some people's skin looks paler when they feel too cold.
Thermoregulation is the process of temperature regulation e.g keeping the body at a healthy temperature and be able to warm or cool the body whenever it is needed.
Temperature changes within the body are detected by sensory receptors called thermoreceptors, which in turn relay information to the hypothalamus in the brain.
When a change in temperature is recorded the hypothalamus reacts by initiating certain mechanisms in order to regain a safe temperature range:
When we are too hot, blood vessels supplying blood to the skin can swell or dilate (vasodilation). This allows more warm blood to flow near the surface of the skin, where the heat can be lost to the air.
This is why some people's skin looks redder when they feel too hot.
Functions of the blood
Function of the blood
The average adult has 4-5 litres of blood. Blood is made up of four constitutes:
Red blood cells (erythrocytes)
White blood cells (leucocytes)
Blood has a number of functions including:
Exercise increases the demand of oxygen. Blood transports oxygen from the lungs to the parts of the body that require it. It also transports metabolic waste from cells to areas of disposal e.g. waste products from the tissues ae transported to the kidneys.
Blood contains tiny fragments of cells called platelets. These platelets are involved in blood clotting and scab forming.
When skin is wounded, platelets are able to:
Release chemicals that cause soluble fibrinogen proteins to form a mesh of insoluble fibrin fibres across the wound
Stick together to form clumps that get stuck in the fibrin mesh
Red blood cells also get stuck in the fibrin mesh, forming a clot. This develops into a scab, which protects the wound as it heals
About 25 per cent of the white blood cells are lymphocytes. They are part of the body’s immune system and produce soluble proteins called antibodies. They help defend against viruses and bacteria.
Antibodies can neutralise toxins produced by pathogens. They can also cause the destruction of pathogens by:
Causing bacteria to burst open and die
Labelling the pathogen so that it is recognised more easily by phagocytes
Sticking pathogens together in clumps so that they can be engulfed by phagocytes more easily