Circulatory system

• The human circulatory system consists of a network of arteries, veins, and capillaries, with the heart pumping blood through it
• Circulatory system


  • Its primary role is to provide essential nutrients, minerals, and hormones to various parts of the body
  • It is also responsible for collecting metabolic waste and toxins from the cells and tissues to be purified or expelled from the body
• Crucial features of the human circulatory system

  • It consists of blood, heart, blood vessels, and lymph
  • It circulates blood through two loops (double circulation) – One for oxygenated blood, another for deoxygenated blood
  • The human heart consists of four chambers – two ventricles and two auricles
  • It possesses a body-wide network of blood vessels comprising arteries, veins, and capillaries
  • The primary function of blood vessels is to transport oxygenated blood and nutrients to all parts of the body, and collect metabolic wastes to be expelled from the body
  • Theoretically, if the veins, arteries, and capillaries of a human were laid out, end to end, it would span a total distance of 1,00,000 kilometres (or roughly eight times the diameter of the Earth)
• Heart


  A muscular organ located in the chest cavity, right between the lungs, enveloped by the pericardium, separated into four chambers - two upper atria and two lower ventricles
• Double circulation


  The way blood flows in the human body, where blood circulates through the heart twice, providing a steady supply of oxygenated blood to every tissue in the body without mixing with deoxygenated blood
• Blood


  The body's fluid connective tissue, circulating nutrients, hormones, minerals and other essential components to different parts of the body
• Components of blood


  • Plasma - the fluid part of the blood composed of 90% water
  • Red blood cells, white blood cells and platelets - the solid part of blood
• Types of blood cells

  • Red blood cells (RBC) / Erythrocytes - transport oxygen, nutrients, and remove waste
  • White blood cells (WBC) / Leukocytes - provide immunity by fending off pathogens and harmful microorganisms
  • Platelets / Thrombocytes - help form clots and stop bleeding
• Arteries


  Blood vessels that transport oxygenated blood from the heart to various parts of the body, thick and elastic
• Veins


  Blood vessels that carry deoxygenated blood towards the heart from various parts of the body, thin and elastic
• Lymphatic system


  Consists of a network of interconnected organs, nodes and ducts that transport and circulate lymph, a colourless fluid containing salts, proteins, water, and digested food and absorbed fat
• Functions of the circulatory system

  • Transporting oxygen throughout the body
  • Sustaining all the organ systems
  • Transporting blood, nutrients, oxygen, carbon dioxide and hormones throughout the body
  • Protecting cells from pathogens
  • Acting as an interface for cell-to-cell interaction
  • Repairing damaged tissue
• Closed circulatory system


  A type of circulation where the blood flows through blood vessels (arteries and veins). This type of circulation is seen in all vertebrates and some invertebrates.
• Advantage of a closed circulatory system

  • More pressure is available in the system, and the blood can reach the body extremities much quicker. This translates to a much faster metabolism rate and quicker movements in organisms with closed circulatory systems.
• Double circulation


  A system of circulation where the blood flows through the heart twice. This type of circulation is very effective as the body has a constant supply of oxygenated blood.
• Dangers of high blood pressure

  • It can cause the inner walls of the arteries to get damaged, arteries to become less elastic, and can potentially cause an aneurysm (a bulge in the artery that can rupture).
• Stroke


  Caused when brain cells do not get enough oxygen and blood supply, resulting in the death of cells and symptoms such as numbness in the face, arms or a part of the body.
• Hypertension


  Another term for high blood pressure, where the blood travels through the blood vessels with more force than normal, resulting in damage to the body. An average healthy human has a blood pressure of 120/80 Hg, and values higher than this are considered hypertension.
• Hypotension

  Also known as low blood pressure, where the blood flows through the blood vessels with unusually low pressure. On average, healthy blood pressure is considered to be between 120/80 Hg, and anything lower than this is considered as hypotension.
• Earliest circulatory system

  • Resembled today's open circulatory system where blood flowed in a hollow enclosed space. Closed circulation evolved much later in ancestors of vertebrates.