THE CIRCULATORY SYSTEM Y10 Science

Kaupapa / learning outcomes To explain the function of the circulatory system To describe the pathway of blood through the heart and body tissues

Functions of the circulatory system The circulatory system has three functions: 1. Transporting substances around the body. These include oxygen, glucose, carbon dioxide, nutrients, water and waste products. 2. Controlling body temperature. 3. Protecting the body. Blood contains cells and anti-bodies that fight infection and clotting agents to stop bleeding. The circulatory system is described as a double system because it has two loops.

The circulatory system

The circulatory system Oxygenated blood returns to the heart through the pulmonary vein. Deoxygenated blood is pumped from the heart to the lungs through the pulmonary artery. lungs Oxygenated blood is pumped at high pressure from the heart to the body through the aorta. Deoxygenated blood returns to the heart through the vena cava. This simple plan shows the heart and the 4 main blood vessels. Introduce the following: Double circulatory system = (1) PULMONARY CIRCULATION (anything pulmonary should be associated with the lungs) between the heart and the lungs and back (2) SYSTEMIC CIRCULATION between the heart and the rest of the body’s systems and back to the heart. Introduce the idea of the heart as a double pump – the right-hand side receiving and pumping deoxygenated blood, the left-hand side receiving and pumping oxygenated blood. ARTERIES carry blood away from the heart, VEINS carry blood to the heart. body’s cells

Draw up a table Blood Vessel Artery Veins Capilliaries Function Other info Structure

Blood vessels artery vein blood to the heart blood from the heart Fill in table Blood vessels There are three types of blood vessels, as shown in this magnified part of the circulatory system. blood from the heart blood to the heart artery vein There are different types of blood vessel because they perform different functions – arteries carry high pressure blood away from the heart, capillaries are small so that they can reach all of the body’s tissues and veins carry low pressure blood and therefore have valves. This is covered on the next slide. carries blood back into the heart carries blood away from the heart carries blood to and from the body’s cells

Blood vessels Under high pressure thick outer wall ARTERY Fill in table thick outer wall thick inner layer of muscle and elastic fibres VEIN narrow central tube (lumen) Under low pressure thin outer wall thin inner layer of muscle and elastic fibres CAPILLARY wide central tube (lumen) wall only one cell thick Where gas/nutrient exchange happens

Blood vessels: valves When blood is flowing against gravity, or when a vein is squeezed by muscle action, there is a risk that blood will flow in the wrong direction. Veins have valves to prevent backflow. backflow prevented vein valve open vein valve closed The valves allow blood to flow in the correct direction… blood to the heart …but close if blood starts to flow in the wrong direction.

Blood vessels

The body cells The blood carries oxygen and dissolved food to all the body’s cells so that respiration can take place.