The Heart and Circulatory System

DK & PK Declarative Knowledge Procedural Knowledge Name the organs of the circulatory system and describe how they function Label parts of the human heart and describe the flow of blood through the body

The next organ system we will be considering can be known by two names….. How are substances transported around the body? Blood system Circulatory system The circulatory system is made of three parts: 1.The heart 2.The blood vessels 3.Blood

One of the substances that the circulatory system transports are respiratory gases. For example, the Oxygen that the body needs, must be taken to the cells and the Carbon Dioxide waste gas must be taken away from the cells. As these gases are carried by the blood, it means that in terms of the presence of gas, we have two types of blood. Blood high in oxygenBlood low in oxygen DeoxygenatedOxygenated

right deoxygenated This section of the system including the right side of the heart, deals with the deoxygenated blood. left oxygenated This section of the system including the left side of the heart, deals with the oxygenated blood. Lungs Body cells At all times these two types of blood cannot mix. Why do you think this is? Because of this our circulatory system is in two parts. It is in fact called a double circulatory system.

The Human Circulatory System

The Heart

Aorta Pulmonary Artery Left Atrium Pulmonary Veins Atrioventricular valve Semilunar valve Left ventricle Right ventricle Posterior Vena Cava Atrioventricular valve Right Atrium Pulmonary veins Semilunar valves Pulmonary Artery Anterior Vena Cava Oxygenated Blood Deoxygenated Blood

Besides the chambers there is also another very important part of the heart – the valves. These valves are found between the top and bottom chambers on both sides of the heart. blood valve These valves are rather like doors that only open in one direction.

As the atrium fills with blood, the valves are closed. When the atrium contracts and squeeze the blood, the valves are pushed open These valves are connected to the side wall of the heart by tough tendons. These tendons allow the valves to close but not invert.

The blood will naturally push against the valve. However, the valves remain firmly shut. In this way, the blood can be moved from chamber to chamber quite efficiently. The valves prevent the blood from moving in the wrong direction.

Now that we can name all of the parts of the heart it is time to see how they work to push blood around the body. The heart pumps blood when its muscle contracts. As the muscle contracts the chamber gets smaller and squeeze the blood out. The two sides of the heart work together. The atria contract and relax at the same time, as do the ventricles. The next two slides describe what occurs inside the heart during one heart cycle.

Blood from the body Blood from the lungs 1. The heart beat begins when the heart muscles relax and blood flows into the atria. 2.The atria then contract and the valves open to allow blood into the ventricles.

The staged cycle then repeats itself. 3.The Ventricles contract forcing the blood to leave the heart. At the same time, the atria are relaxing and once again filling with blood.

Just before we finish our study, let’s take a last look at the heart….. Do you notice anything different about the two sides of the heart? Well, the left ventricle wall is clearly thicker than the right ventricle wall. Why is this? To answer this question, think about where the blood is going when it leaves the right and left ventricles.

This journey is enormous. The left ventricle has to pump blood all over the body! This journey is far less demanding. The right ventricle only has to pump blood from the heart to the adjacent lungs. Therefore, the left ventricle needs a thicker wall to generate a stronger ‘squeeze’ on the blood. Body cells Lungs

Now, let’s consider the blood vessels... We can get an idea of what they could look like from considering the job they have to do. 3 Let us look at a small section of the circulatory system. There seems to be 3 types of blood vessel present One One takes blood away from the heart One One takes blood to the heart One One joins the other two together

So we have 3 types of blood vessels doing 3 different jobs.1. ARTERIES Blood vessels that take blood away from the heart are known as ARTERIES. 2. VEINS Blood vessels that take blood back to the heart are known as VEINS. aa Remember, arteries (away) inin Remember, veins (into the heart)

3. arteries veins Finally, if arteries take blood away from the heart and veins take blood back to the heart, when does an artery turn into a vein? Well, our third type of blood vessel links the two. In other words, we find it present where an artery finishes and a vein is about to begin. CAPILLARY. This third type of blood vessel is known as a CAPILLARY.

Let us consider each vessel in turn to see how its shape is related to the job it has to do. ARTERY In each case we will look at a cross-section of the vessel small lumen thick muscle and elastic fibres

The blood flowing through an artery will be under high pressure and moving extremely fast. no valves There is no chance that the blood will turn around and start travelling in the opposite direction. Therefore there are no valves present in arteries.

VEINS large lumen thin muscle and elastic fibres

The veins are carrying blood back towards the heart. Materials have been exchanged and now it is running out of energy. It needs to return to the heart to receive another pump. Unfortunately, this could lead to a realProblem.. human leg What happens if blood loses so much energy that it stops and turns around? vein

This situation could arise where blood is flowing against gravity. However, there is a solution to this problem. It comes in two parts. 1. Firstly, veins have valves which act to stop the blood from going in the wrong direction. (These valves are similar to those found in the heart) valves open blood valves close

CAPILLARIES These vessels link arteries with veins. They are found all over the body and are essential for the exchange of materials between the blood and other body cells. arteryvein capillaries

very narrow lumen The wall of a capillary is only one cell thick! Capillaries are so small that they can only be seen using a microscope. capillary bed A collection of capillaries is known as a capillary bed.

Substances can diffuse across the lining of the capillary. This allows useful substances which are dissolved within the blood to move into surrounding cells whilst cellular waste moves in the opposite direction The exchange of materials between the blood and the body can only occur through capillaries.

One such exchange that occurs in the capillaries is that of oxygen and carbon dioxide.

Summary The respiratory system is responsible for providing the body with oxygen and removing carbon dioxide. The circulatory system is responsible for transporting oxygen, carbon dioxide and other substances around the body. These two systems work hand-in-hand and are crucial for life.