Science 6
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Unit 1 You and others Like You
Our body is made up of very tiny cells. They are the building blocks of life. A group of cells working together forms a tissue. Sets of tissues of the same function form an organ. Sets of organs make a system. All the systems make up the human body.
Chapter 1 The Circulatory System
Your body needs oxygen and digested food for it to live and grow. how do these materials reach the different parts of your body? They reach to the different parts of your body through the process of circulation. Circulation is a process in which blood flows into the different parts of the body. This is made possible through the circulatory system, the transport system of the body..................
MAJOR PARTS OF THE CIRCULATORY SYSTEM : The human circulatory system has three major parts :
1. Blood- A fluid that serves as a medium of transport
2. Blood Vessels- A system of vessels that conducts the blood throughout the body.
3. Heart- a pump that keeps the body circulating
The blood, blood vessels, and heart work together to preform several functions that include :
1. Regulation of the body temperature. This is achieved by adjustments in the blood flow. The faster the blood flows, the higher the body temperature.
2. Transport of oxygen from the lungs to the tissues; of carbon dioxide from the tissues to the lungs.
3. Protection of the body from harmful bacteria and viruses by circulating antibodies and white blood cells.
4. Distribution of nutrients that come from the digestive system to all the body cells.
5. Transport of waste products to the liver, then to the kidney for excretion release.
6. Distribution of hormones from the organs that produce them to the tissues. Hormones are chemicals sythenized by one group of cells and carried in the bloodstream to other cells.
7. Prevention of blood loss by means of clotting.
The Parts of the Blood :
1. Plasma- is the liquid part of the blood.
2. Red blood cells or erythrocytes- contains haemoglobin, which is the red pigment of the blood. Haemoglobin helps transport oxygen to the body.
3. White blood cells or leukocytes- fight the infections in the body.
4. Platelets or thrombocytes- it clots (hardens) the blood when you have a cut or a wound.
The Parts of the Blood Vessels :
1. Arteries- carries blood containing oxygen away from the heart.
2. Veins- carry blood containing carbon dioxide back to the heart.
3. Capillaries- are tiny vessels where exchange of materials take place and it connects the arteries and veins together.
The Heart
The heart is divided into two main parts, the left half and the right half. The upper chamber is called artria and the lower chambers are called ventricles.
The ventricles are responsible for keeping the blood moving through the parts of the body. the artria are merely the containers where the blood collects.
Blood enters each ventricle of the heart through the valves. Valves are special one-way openings. They allow the blood to move in one direction. The valves prevent the blood from flowing back.
How does Blood Flow in the Heart?
The blood enters the right side of the heart through the two largest veins; namely the superior vena cava and the inferior vena cava. The superior vena cava allows the oxygen-poor blood to flow from the upper part of the body. The inferior vena cava allows the oxygen-poor blood to flow from the lower part of the body. The oxygen-poor blood is deposited into the right atrium. From the right atrium, blood goes to the tricuspid valve and enters the right ventricle. When the right ventricle contracts, blood is pumped through the pulmonary valve going to the pulmonary artery and into the lungs. There blood deposits carbon dioxide and picks up oxygen. Blood returns to the heart from the lungs through the pulmonary vein and goes into the left atrium. When the left atrium contracts, blood goes through the mitral valve and into the left ventricle. The left ventricle, the largest chamber of the heart, pumps blood through the aortic valve and into the arteries for distribution of oxygen-rich blood to all body cells.
