Human Body - Class 7 Science Revision Notes

• The Blood Circulatory System
  • Parts of the Circulatory System
  • Blood Components and their Functions
  • Types of Blood Vessels and their Functions.
• The Heart
  • The Circulation of Blood
  • The Importance of Blood Circulation.

The Blood Circulatory System

Parts of the Circulatory System

• The heart-The pumping organ
• The blood-The transport fluid.
• The blood vessel-They are pipes through which the blood flows

Blood Components and their Functions

• Plasma-The liquid part of the blood which transport digested food materials, salts and other dissolved substances.
• Red blood cells-They contain red colouring matter called haemoglobin, which gives blood the red colour, red blood cells
  helps in transporting oxygen.
• White blood cells-They have a nucleurs, they help in fighting and killing disease-causing germs.
• Platelets-They help in blood clotting ie further loss of blood through wound.

Types of Blood Vessels and their Functions.

Arteries:

• They carry blood away from the heart
• They have thick walls
• They have a narrow lumen.
• They have no valves since they carry blood at a high pressure  from the heart.
• They carry oxgyeneted blood except pulmonary artery which carry deoxgeneted blood from the heart to the lungs.
• Main artery is Aorta.

Veins:

• They carry blood from other body parts to the heart.
• They have thin walls.
• They have a wide lumen.
• They carry blood at a low pressure.
• They carry deoxygenated blood except pulmonary vein which carry oxygenated blood from lungs to the heart.
• Main vein is Venacava.

Capillaries:

• They are small blood vessels that help to take blood to all parts of the body.
• They are found all over the body.
• They cover a wide surface of the body.

The Heart

• It has four chambers, two chambers are on the upper parts(Auricles) and two chambers on the lower parts(Ventricles)
• The heart is also divide into left and right side which is vertically lateral to how it faced(Your left hand side becomes the right when in paper and vice versa).
• The parts include: Right auricle, Left auricle, Right ventricle and Left ventricle.
• The heart also have valves ie semi lunar valve, tricuspid valve and bicuspid valve.

The Circulation of Blood.

• Blood from all parts of the body flows into the right auricle of the heart through venacava, then its pumped through pulmonary artery to the lungs for oxidation.
• In the lungs, oxygen is added to the blood and carbon dioxide is removed.
• Oxygenated blood then flows to the left auricle of the heart through the pulmonary vein.
• The muscular left ventricle then pumps the blood to all parts of the body through the aorta. This process repeats back and forth making another cycle.
  NB: When one inhales carbon monoxide the chamber of the heart that receives it first will be left auricle, but when one is bitten by a snake the poison will first reach the right auricle through venacava.

The Importance of Blood Circulation.

• It transports food from the small intestine to all parts of the body.
• Transports oxygen from the lungs to all cells of the body.
• Transports carbondioxide from the body tissues to the lungs.
• Wastes materials like urea to the kidney.
• Transports heat to all parts of the body.

Activity: Draw a well labelled diagram of the heart.