circulatory system

• Circulation


  The blood flows constantly around the body from the heart, to the cells, and then returns to the heart
• Components of the circulatory system

  • Blood
  • Heart
  • Blood vessels (arteries, capillaries and veins)
• Blood


  A complex fluid circulated by the pumping action of the heart that nourishes every cell of the body
• Functions of blood

  • Transportation of oxygen and nutrients to the tissues and removal of carbon dioxide and wastes
  • Protection of the body via the immune system and by clotting to prevent blood loss
  • Regulation of the body's temperature and the fluid content of the body's tissues
• Components of blood

  • Plasma (liquid component)
  • Red blood cells
  • White blood cells
  • Platelets
• Plasma


  A straw-coloured liquid mainly consisting of water (about 90%) with substances such as plasma proteins, nutrients, hormones, mineral salts and wastes dissolved in it
• Much of the carbon dioxide and very small amounts of oxygen are also carried in a dissolved state in plasma
• Water is a significant component of the circulatory system and controls body heat through sweating
• Red blood cells

  Formed in bone marrow, their main role is to carry oxygen and carbon dioxide around the body, they contain iron and haemoglobin
• Red blood cells outnumber white blood cells by about 700 to one
• Men have 16 grams of haemoglobin per 100 millilitres of blood, while women average 14 grams per 100 millilitres of blood
• Women have lower levels of haemoglobin and a slightly lessened ability to carry oxygen in the blood
• White blood cells

  Formed in the bone marrow and lymph nodes, they provide the body with a mobile protection system against disease
• Diseases such as HIV/AIDS, which suppress the activity of the immune system, do so by disrupting the normal functioning of the white blood cells
• Platelets


  Tiny structures made from bone marrow cells that have no nucleus, they help to produce clotting substances that are important in preventing blood loss when a blood vessel is damaged
• Heart


  A muscular pump that contracts rhythmically, providing the force to keep the blood circulating throughout the body
• The heart beats an average of 70 times per minute at rest, amounting to more than 100,000 beats per day
• In one day the heart pumps approximately 12,000 litres of blood
• Parts of the heart

  • Atria (upper, thin-walled chambers that receive blood coming back to the heart)
  • Ventricles (lower, thick-walled chambers that pump blood from the heart to the body)
• A system of four one-way valves allows blood to flow in only one direction through the heart
• Deoxygenated blood (blue) is pumped to the lungs, where after receiving oxygen, it turns reddish and returns to the heart to be pumped through the body
• the heart is located between the lungs
• The right side of the heart receives deoxygenated blood from the vena cava and pumps it into the pulmonary artery which carries it to the lungs.
• The left side of the heart receives oxygenated blood from the pulmonary vein and pumps it out to the rest of the body via the aorta.
• Blood pressure refers to the force exerted by blood against the walls of the vessels as it flows through them.
• the heart has four chambers, two atria and two ventricles
• the right side of the heart pumps blood to the lungs
• Systolic pressure is the maximum pressure reached during contraction of the ventricle when blood is being ejected into the arteries.
• Diastolic pressure is the lowest point reached during relaxation of the ventricles when blood is returning to the heart.