Circulatory System

What is blood made up of?

Blood is made up a liquid part called plasma and a non-liquid part consisting of cells and cells fragments, which together are called formed elements.

Describe plasma

* Blood plasma is mainly water, 91%


* Proteins, which give blood its viscosity, make up 7% of plasma.
* The remaining 2% is dissolved solutes such as hormones, gases, nutrients, cell wastes and soluble proteins
* Makes up 55% of blood volume.

What is plasma’s function?

Function is to transport the components of blood, including cells, nutrients, wastes, hormones, proteins and antibodies, throughout the body

Describe Erythrocytes (red blood cells)

* Account for 40-45% of its volume


* Give blood its colour
* Biconcave discs
* No nucleus
* Contain haemoglobin which carries oxygen
* 120 day life span (42 day shelf life)
* Produced in bone marrow
* Destroyed in liver and spleen
* Anaemia = low red blood cell count

What is erythrocytes’ function?

Function is to transport oxygen from the lungs to the cells throughout the body

Describe Leucocytes (white blood cells)

* Larger but fewer in number than erythrocytes


* Different types including granulocytes, monocytes and lymphocytes
* Removing dead or injured cells and invading microorganisms
* Life span of several hours to several years
* 1% of blood volume

What are the types of leucocytes?

1. Neutrophils
2. Monocytes
3. Lymphocytes
4. Basophils


1. Eosionphils

What is neutrophils function?

Contain enzymes to digest pathogens

What is monocytes function?

form other cells, including macrophages that engulf pathogens and aged or damaged cells by phagocytosis

What is lymphocytes function?

involved in the immune response

What is basophils function?

Responsible for allergic reactions

What is eosionphils function?

lead to inflammatory responses; they respond to larger parasites such as worms

Describe thrombocytes (platelets)

* Very small cell fragments


* No nucleus
* Formed in red bone marrow
* 7 day life span (5 day shelf life)
* Involved in blood clotting

What are the functions of blood? (7)

* Transporting oxygen and nutrients to cells


* Transporting carbon dioxide and other wastes away from cells
* Transporting chemical hormones to cells
* Maintaining pH of body fluids
* Distributing heat and maintaining body temperature
* Maintaining water content and ion concentrations of body fluids
* Protecting against disease-causing microorganisms

How does blood transport oxygen?

Oxygen is not very soluble in water, so only about 3% of oxygen is carried in blood plasma. The other 97% is carried in combination with haemoglobin molecules found in red blood cells.

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When oxygen levels are high, like in the lungs, haemoglobin combines with oxygen to form oxyhaemoglobin. Oxyhaemoglobin breaks down when oxygen levels are low, releasing oxygen to diffuse into cells.

How does blood transport carbon dioxide?

Carbon dioxide is carried in the blood in several ways - about 8% is dissolved in blood plasma, another 22% combines with haemoglobin to form carbaminohaemoglobin and the remaining 70% is carried as bicarbonate ions, HCO3-

CO2+H2OH2CO3H++HCO3-

What is nutrients and wastes?

Nutrients and wastes are dissolved and transported in the blood plasma.

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Nutrients are essential substances contained in our food such as glucose, vitamins, mineral ions, amino acids, fatty acids and glycerol.

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Metabollic wastes are substances produced by our cells that cannot be used and would be harmful if allowed to accumulate. Organic wastes include urea, creatine and uric acid.

How does blood protect against disease-causing microorganisms?

Some white blood cells are phagocytic, meaning they are able to ingest foreign cells and particles. Other white blood cells fight off infection by producing antibodies.

What is the heart and where is it located?

The heart is the pump that pushes the blood around the body. It is located between the two lungs in the mediastinum, behind and slightly to the left of the sternum.

What is the heart’s shape?

The heart is a conical shape approximately 12cm long, 9 cm at its widest point and 6 cm thick. It is completely enclosed in a membrane called the pericardium. This membrane holds the heart in a place, but also allows the heart to move as it beats. It also prevents the heart from overstretching. The wall of the heart itself is made up of a special type of muscle, called cardiac muscle.

What is the function of the left and right side of the heart?

The left and right sides of the heart are separated by a wall called the septum. The right side of the heart collects blood from the body and pumps it to the lungs, whereas the left side receives blood from the lungs and pumps it to the rest of the body.

What are the four chambers and what are their functions?

* The right atrium receives blood from the body and passes it to the right ventricle


* The right ventricle pumps blood to the lungs
* The left atrium receives blood from the lungs and passes it to the left ventricle
* The left ventricle pumps blood to the body

Which ventricle wall is thicker and why?

The wall of the left ventricle is thicker than the wall of the right ventricle. This is because it needs to be much stronger to pump the blood through the blood vessels supplying the body.

What do valves in the heart ensure?

Valves in the heart ensure that the blood can only flow in one direction

What is between the atria and the ventricles?

Between the atria and the ventricles are the atrioventricular valves

What are the atrioventricular valves?

These are flaps of thin tissue with the edges held by tendons, called chorda tendineae, that attach to the heart on papillary muscles. When the ventricles contract, the blood catches behind the flaps and they billow out like a parachute, sealing off the opening between the atria and the ventricles. Blood must then leave the heart through the arteries and not flow back into the atria.

What are the valves where the arteries leave the heart?

Semilunar valves

What does the semilunar valves do?

They stop blood from flowing back into the ventricles when the ventricles relax

What does each semilunar valve have and what do they do?

Each semilunar valve has three cusps. When blood flows into the artery, the cusps fill out and seal off the artery, ensuring that the blood only flows in one direction. It is the closing of the valves that gives the heartbeats their characteristic ‘lub dub’ sound. The two sounds are due to the closing of the atrioventricular and then semi-lunar valves.

Where is the blood pumped the heart go to?

Blood vessels

What do the blood vessels do?

carry the blood to the cells of the body or the lungs, and then bring it back to the heart again

What is circulation?

The same blood flows continuously through the heart, and this movement of blood is referred to as the circulation.

What are the three main types of blood vessels and how are they joined together?

joined together to form the channels through which the blood flows: arteries, capillaries and veins

What are the arteries?

Arteries are the blood vessels that carry blood away from the heart.

What is the largest artery and what does it do?

The largest artery is the aorta, which takes blood from the left ventricle to the body.

What is another important artery and what does it do?

Another important artery is the pulmonary artery, which takes blood from the right ventricle to the lungs.

What do the walls of an artery contain?

The walls of an artery contain smooth muscle and elastic fibres.

What happens when the ventricles contract?

When the ventricles contract and push blood into the arteries, the walls of the arteries stretch to accommodate the extra blood. When the ventricles relax, the elastic artery walls recoil. This elastic recoil keeps the blood moving and maintains the pressure. The muscle in the artery walls does not contract and relax to pump the blood along. However, the muscle can contract to reduce the diameter of the artery and thus reduce blood flow to an organ. Such contraction of a blood vessel is called vasoconstriction. Conversely, the muscle may relax to increase blood flow to an organ in a process called vasodilation. In this way, blood flow may be controlled to allow for the changing needs of the body.

What are arterioles?

The very large arteries that receive blood pumped by the ventricles divide into smaller arteries. These in turn divide into very small arteries, known as arterioles.

What do the arterioles do?

It is the arterioles that supply blood to the capillaries. Like the larger arteries, the arterioles have smooth muscle in their walls. Contraction or relaxation of this muscle is very important in regulating blood flow through the capillaries.

What are vasodilators?

Substances that produce a local widening, or dilation of arterioles

What happens as the body exercises?

As the body exercises, the muscle cells continually require energy. Cellular respiration in the muscle cells make the energy available, but also produces large amounts of wastes, including carbon dioxide and lactic acid. These wastes act as vasodilators. This results in increased blood flow through the muscle tissues, ensuring that the cells are adequately supplied with oxygen and nutrients for continued functioning. Cellular respiration also releases heat energy, which tends to increase blood temperature. It also contributes to an increase in heart rate.

What are capillaries?

Capillaries are the link between the arteries and veins. They are microscopic blood vessels that form a network to carry blood close to nearly every cell in the body.

What do capillaries enable?

This enables the cells to get their requirements from the blood and to pass their waste into the blood. The structure of the capillaries makes them suitable for this function, as their walls have only one layer of cells. This allows substances to pass easily between the blood and the surrounding cells

What do veins do?

Veins carry blood towards the heart. The capillaries join into small veins, venules, which then join up to make larger veins

What are the type of large veins?

1. inferior vena cava and superior vena cava
2. pulmonary veins

What do inferior and superior vena cava do?

bring blood from the body to the right atrium. The superior vena cava brings blood from above the heart, while the inferior vena cava brings blood from below the heart

What do pulmonary veins do?

which bring blood from the lungs to the left atrium. There are 4 pulmonary veins - two from each lung

What is the veins and venules structure?

Veins and venules do not have muscular walls and are not able to change their diameter in the way that arteries do. Blood pressure in the veins is relatively low because the blood loses most of its pressure as it flows through the tiny capillaries. The walls of veins are therefore much thinner than those of arteries; also, the pressure in veins is constant so the walls do not have to be elastic. Because of the low blood pressure, many veins have valves to prevent the blood from flowing backwards.

What is blood flow?

Blood is the transport medium that delivers oxygen and nutrients to cells and carries away their wastes. The requirements of cells vary depending on their level of activity. For example, when we are actively exercising, the muscles use up much more oxygen and nutrients, and produce more carbon dioxide and other wastes, than when we are sitting at rest. To cater for these changes in requirements, the blood flow to and from the cells must be able to change. There are two ways that this can occur:

* By changing the output of blood from the heart
* By changing the diameter of the blood vessels supplying the tissues

What is the cardiac cycle?

The cardiac cycle, or heartbeat, is the sequence of events that occurs in one complete beat of the heart.

What is systole?

The pumping phase of the cardiac cycle, when the heart muscle contracts,

What is diastole?

The filling phase, as the heart muscle relaxes

What happens in diastole?

the atria fill with blood and the ventricles also receive blood as the valves between them are open

What happens in systole?

Atrial systole, the contraction of the atria, then follows and forces the remaining blood into the ventricles. The atria then relax and refill while the ventricles contract in ventricular systole. Ventricular systole forces blood into the arteries. Although the left and right sides of the heart are two pumps, they operate together. Both atria contract simultaneously, as do both ventricles.

What is cardiac output?

How quickly the blood flows around the body depends on how fast the heart is beating and how much blood the heart pumps with each beat.

What is heart rate?

The heart rate is the number of times the heart beats per minute

What is the stroke volume?

the stroke volume is the volume of blood forced from a ventricle of the heart with each contraction

What influences the cardiac output?

the heart rate, and the stroke volume

Compare and contrast vasodilation and vasoconstriction?

Compare: Both are referencing the change in the size of the lumen of arteries. Both require smooth muscle in the walls of the arteries.

Contrast: Vasoconstriction narrows the lumen of the arteries/arterioles by contracting the muscles in the artery wall and reduces blood flow to an organ.

Vasodilation widens the lumen of the arteries by relaxing the muscles in the artery wall and increasing blood flow to an organ.

Explain the importance of papillary muscles

Papillary muscles attach to the chordae tendineae which hold in place the atrioventricular valves. When the ventricles contract the atrioventricular valves billow shut, preventing backflow of blood in the heart. Without the papillary muscles, the tendons would not have anything to attach to, meaning that with every ventricular contraction blood would flow back into the atria, rather than to the arteries.

Explain why the pulmonary artery carries deoxygenated blood, while other arteries carry oxygenated blood

Arteries carry blood away from the heart. The pulmonary artery is carrying the deoxygenated blood away from the right ventricle of the heart toward to lungs for gas exchange to occur. The other arteries are also carrying blood away from the heart, but from the left ventricle, and as such carry oxygenated blood.

Discuss the importance of the septum in the heart

The septum separates the left and right side of the heart. Its presence ensures that oxygenated and deoxygenated blood do not mix in the heart.

What is the heart protected by?

The sternum and ribcage

What is the weight of a human heart?

The average weight is 250-300g

How many layers does the heart have?

3

endocardium, myocardium, epicardium

What is the endocardium?

The smooth, inside lining of the heart

What is the myocardium?

The middle layer of heart muscle

What is the epicardium?

The outer layer, surrounded by a fluid filled sac called the pericardium

What happens to the cells while the heart pumps blood around the body?

While the heart pumps blood around the body, the cells of the heart require oxygen and other nutrients.

How does the heart obtain nutrients and oxygen?

The heart does not obtain oxygen and other nutrients from the blood flowing inside it - it gets its blood from coronary arteries that carry blood within the heart muscle. Approximately 4-5% of the blood output of the heart goes to the coronary arteries, about 225mL/min.

How is the heart divided?

Divided into 4 chambers: the right atrium, the right ventricle, the left atrium and the left ventricle

How does the blood enter the heart?

All blood enters the right side of the heart through two veins: the superior vena cava and the inferior vena cava

What happens when the right atrium contracts?

When the right atrium contracts, the blood goes through the atrioventricular valve (or tricuspid valve) and into the right ventricle

What happens when the right ventricle contracts?

When the right ventricle contracts, blood is pumped through the pulmonary valve, into the pulmonary artery and into the lungs where it picks up oxygen.

Blood returns to the heart from the lungs through the pulmonary vein and goes into the left atrium..

What happens when the left atrium contracts?

When the left atrium contracts, blood travels through the atrioventricular valve (or bicuspid valve) and into the left ventricle.

The left ventricle pumps blood through the aortic valve and into the aorta. The aorta is the main artery of the body. It receives all the blood that the heart has pumped out and distributes it to the rest of the body

What do the one-way valves prevent?

The one-way valves prevent blood from flowing backwards. When each chamber contracts, the valve at its exit opens. When it is finished contracting, the valve closes so that blood does not flow backwards.

Why does the left ventricle have a thicker muscle?

The left ventricle has a thicker muscle than any other heart chamber because it must pump blood to the rest of the body against much higher pressure in the general circulation.

What is the cardiac cycle?

The cardiac cycle is the sequence of events that occurs in one complete beat of the heart.

What happens first in the cardiac cycle?

First, the heart muscle relaxes, called diastole, allowing the atria to fill with blood. The blood flows into the ventricles as soon as their walls relax

What happens second in the cardiac cycle?

The heart contracts. This occurs in two stages. Firstly, the right and left atria contract at the same time, called atria systole. This pumps blood to the right and left ventricles.

What happens third in the cardiac cycle?

The ventricles contract, called ventricular systole. Which pumps blood into the pulmonary arteries and aorta.

What is the lub' dub’ sound you hear?

The ‘lub dub’ sound you hear when you listen to a person’s heart is the closing of the valves.

The ‘lub’ is the closing of the AV valves before ventricular systole. This prevents blood from flowing back into the atria

The ‘dub’ is the closing of the aortic and pulmonary valves at the end of the ventricular systole, which prevents blood flowing back into the heart from mthe blood vessels.

Why check your blood pressure?

* High blood pressure is a risk factor for heart disease and stroke.


* It’s important to know if you have high blood pressure, so it can be treated.
* A combination of medications and lifestyle changes can be successful in lowering your blood pressure

What does the health of your whole body depend on?

Depends on the good health of your cardiovascular system

What is one measure of the cardiovascular system?

Blood pressure

How does blood pressure occur?

Blood pressure occurs when circulating blood puts pressure on the walls of blood vessels.

Since blood pressure is primarily caused by the beating of your heart, the walls of the arteries move in a rhythmic fashion.

What has greater blood pressure in the body: arteries or veins?

Blood in arteries is under the greatest amount of pressure. The pressure of the circulating blood slowly decreases as blood moves from the arteries and into the smaller blood vessels. Blood in veins is not under much pressure

How to read blood pressure?

Blood pressure is read as two numbers; first is the systolic pressure, second is the diastolic pressure

What is the systolic pressure?

The systolic pressure is the pressure on the blood vessels when the heart beats. This is the time when there is the highest pressure in the arteries

What is the diastolic pressure?

The diastolic pressure is when your blood pressure is lowest, when the heart is resting between beats

What are healthy ranges for blood pressure?

Systolic: less than 120

Diastolic: less than 80

How is blood pressure written?

Systolic/diastolic E.g. 120/80

How can blood pressure vary?

Pressure varies with exercise, emotions, sleep, stress, nutrition, drugs or disease

What have studies shown with people with lower systolic pressure?

Studies have shown that people whose systolic pressure is around 115, rather than 120, have fewer health problems. Clinical trials have shown that people who have blood pressures at the low end of these ranges have much better long term cardiovascular health

How is blood pressure measured?

With a sphgmomanometer

When does hypertension occur?

Hypertension (high blood pressure) occurs when a person’s blood pressure is always high

When is hypertension said to be present?

Hypertension is said to be present when a person’s systolic blood pressure is always 140 or higher and/or if the person’s diastolic blood is always 90 or higher

What does having hypertension increase?

Having hypertension increases a person’s chance for developing heart disease, having a stroke, or suffering from other serious cardiovascular diseases.

What are symptoms of hypertension?

Hypertension often does not have any symptoms, so a person may not know that he or she has high blood pressure. For this reason, hypertension is often called the “silent killer”