Circulatory

• Blood is a special connective tissue comprising of a fluid matrix, plasma and formed elements
• plasma is a straw coloured liquid that contains dissolved substances and proteins and is slightly alkaline
• plasma without the blood clotting factors is called serum
• erythrocytes - RBC
• erythrocytes are the most abundant of all cells found in the blood, they are red due to the presence of haemoglobin
• the formation of RBC takes place in the bone marrow in adults
• RBCs are biconcave, disc shaped cells without nucleus having diameter of 7-8 micron
• total lifespan of RBC is 120 days
• Leukocytes - WBC
• leukocytes are colourless in nature as they do not possess the red colour pigment in them
• types of Leukocytes-

  • granulocytes
  • agranulocytes
• Types under granulocytes

  • neutrophils
  • eosinophils
  • basophils
• types under agranulocytes

  • lymphocytes
  • monocytes
• neutrophils are the most abundant cells of the total WBCs, they are neutral in nature and are phagocytiez cells that destroy foreign organisms entering the body
• eosinophils are stained bright red with acidic dye, they resist infections and are also associated with all allergic reactions
• Basophils contain fewer coarse granules than the eosinophils and can be stained with basic dyes such as methylene blue

  they secrete histamine, serotonin, heparin and are involved in inflammatory reactions
• lymphocytes are smaller in size and have rounded nucleus

  they have two types B-cells and T-cells, both are responsible for the immune responses of the body
• monocytes are the largest of all WBCs but fewer in number

  mature ones are called macrophages

  they help to kill foreign particles

  these are phagocytic in nature
• O is universal donor

  AB is universal acceptor
• thrombocytes - blood platelets
• thrombocytes are cell fragments produced from megakaryocytes that are responsible for clotting
• the plasma membrane of RBCs contain certain glycoproteinaceous molecules known as antigens
• individuals having Rh antigen are called Rh positive
• Individuals having no Rh antigen are called Rh negative
• Formation of a Clot

  1. Injury or trauma causes stimulation of platelets cells

  2. Platelets release certain platelet factors

  3. Activates the mechanism of coagulation or clotting of blood at the site of injury
• Clotting mechanism

  1. Thromboplastin helps in formation of prothrombinase enzyme

  2. Prothrombinase converts inactive prothrombin into active thrombin

  3. Thrombin converts fibrinogen into insoluble fibrin monomer

  4. Fibrin monomers polymerise to long, sticky fibres

  5. Fibrin threads form a fine network trapping formed elements of blood

  6. Leads to formation of a clot or coagulum
• Clotting process

  • Requires Ca ions for the reactions
  • Involves a series of linked enzymatic reactions with cascade effects
• Fibrinogen is produced from the liver in the presence of vitamin-K
• Thrombokinase is an enzyme complex formed by the series of linked enzymatic reactions
• Lymph is a connective tissue that flows inside the specialized vessels called lymph vessels
• Circulatory system in humans

  Also known as blood vascular system, consists of a muscular chambered heart, a network of closed branching blood vessels and the fluid which is circulated, i.e. blood
• Heart


  • Mesodermally derived organ, situated in the thoracic cavity in between the two lungs, appears to be slightly tilted towards the left side, upper broad part is called the base and the lower narrow part known as the apex, size of a clenched fist
• External structure of heart

  Heart is protected by a double-walled membranous sac or a bag called pericardium, fluid between two membranes is called pericardial fluid, helps in keeping the surface of the heart moist and also protects it from shock and mechanical injuries
• Right atrium


  Slightly larger than the left atrium, meant to receive blood from different body parts
• Internal structure of heart

  Chambers of heart (two auricles and ventricles) are separated by different septa and valves
• Atria


  Upper two thin-walled and smaller chambers, serve to receive the blood, therefore, are called receiving chambers (right atrium and left atrium), separated by a thin, muscular wall known as inter-atrial septum
• Right atrium


  Deals with only impure (deoxygenated) blood, receives impure blood from various parts of the body, through two vena cava
• Left atrium

  Deals with only pure (oxygenated) blood, receives blood (pure) from lungs through two pulmonary veins (one from each lung)
• Ventricles


  Lower two chambers of the heart, pump the blood away from the heart, ventricular walls are thicker than that of the atria, function as pumping chambers, separated by the interventricular septum
• Right ventricle


  Receives impure blood from right atrium and pumps blood into pulmonary artery, which further takes this blood for lung oxygenation