The circulatory system

• The circulatory system is the transport system of the body
• It transports food and oxygen to the cells for use in respiration and removing waste
• Main components of circulatory system

  1. Heart
  2. Blood vessels
  3. Blood
• The heart is a muscular pump and it is the size of a clenched fist
• The heart is surrounded by a membrane called the pericardium
• The pericardium holds the heart in place and prevents it from over stretching
• The sides of the heart are separated by the septum
• Each side of the heart has 2 champers → atria + ventricles
• Atria → Thinned walled, they collect blood entering the heart
• Ventricles → Thicker and more muscular, they pump blood, left is thicker (has to pump to the body)
• Valves → Prevent back flow of blood or blood flowing in the wrong direction (Tri - Bi)
• Cordae teninae → They prevent the valves from turning inside out
• Arteries → Transport blood away from the heart
• Arteries

  Thick walls, muscular, elastic → for high blood pressure

  Blood pressure fluctuates as the heart contracts and relaxes
• Arteries carry oxygenated blood → besides the pulmonary arteries
• Your pulse is the recoil and expansion of the arteries
• Veins → Transports blood towards the heart
• Veins

  • Low and constant blood pressure
  • Thin, inelastic wall, little muscles
• Most veins carry deoxygenated blood → besides pulmonary veins
• The contraction of skeletal muscles helps push the blood along in the veins
• Capillaries → transport blood close to cells
• Capillaries

  • Connect arteries to veins
  • Tiny vessels → one cells thick
  • Semi-permeable walls → e.g. oxygen out, carbon in
• Arterial end (capillaries)→ connect to arteries, high blood pressure
• Venous end (capillaries)→ connect to veins, low blood pressure
• Erythrocytes → red blood cells
• Erythrocytes 


  Shaped like bi-concave discs to increase their carrying capacity for gases
• Red blood cells contain haemoglobin which increases the oxygen carrying capacity of cells and also increases the rate at which O2 moves to the cell
• Haemoglobin combines with O2 in the lung capillaries to from oxyhaemoglobin
• Haemoglobin combines with CO2 in the tissues to from carbaminohaemoglobin
• Mature red blood cells don’t have a nucleus → more room for the haemoglobin
• • Red blood cells have elastic membranes which allow them to squeeze through tiny capillaries
  • They are made in the red bone marrow → life span of 120 days
• Aged red blood cells are removed → liver + spleen
• Leucocytes → white blood cells
• Since white blood cells have a nucleus → no haemoglobin
• White blood cells are made in the red bone marrow, thymus glad and lymphatic tissues
• White blood cells

  They defend the body from disease → remove dead or injured cells using phagocytosis
• White blood cells live for only a few hours or few days
• Thrombocytes → platelets
• Platelets are Small cell fragments
• Blood clotting (platelets) → they from initial plus, then they initiate clotting factors which act as scabs