Biology BLOOD COAGULATION AND TISSUE FLUID

KEY TOPICS

star Coagulation of Blood
star Lymph
star Circulatory Pathway

COAGULATION OF BLOOD

● When a finger is cut, the wound does not continue to color{violet}("bleed") for a long time; usually the color{violet}("blood stops") flowing after sometime.

● color{violet}("Blood") exhibits color{brown}("coagulation or clotting") in response to ancolor{violet}(" injury or trauma.")

● This is a mechanism to prevent excessive loss of color{violet}("blood") from the color{violet}("body.")

● One can observed a color{violet}("dark reddish brown scum") formed at the site of a cut or an injury over a period of time.

● It is a clot or coagulam formed mainly of a network of threads called color{brown}("fibrins") in which color{violet}("dead and damaged") formed elements of blood are trapped.

● color{violet}("Fibrins") are formed by the conversion of color{brown}("inactive fibrinogens") in the plasma by the enzyme color{brown}("thrombin.")

● color{violet}("Thrombins"), in turn are formed from another inactive substance present in the plasma called color{brown}("prothrombin.")

● An color{violet}("enzyme complex") , color{brown}("thrombokinase,") is required for the above reaction.

● This complex is formed by a series of linked color{violet}("enzymic reactions") ( color{brown}("cascade process")) involving a number of factors present in the plasma in an inactive state.

● An injury or a color{violet}("trauma") stimulates the color{brown}("platelets") in the blood to release certain factors which activate the mechanism of color{violet}("coagulation.")

● Certain factors released by the tissues at the color{brown}("site of injury") also can initiate coagulation.

● color{brown}("Calcium ions") play a very important role in color{violet}("clotting.")

LYMPH (TISSUE FLUID)

● As the color{violet}("blood passes") through the color{violet}("capillaries in tissues"), some water along with many small water soluble substances move out into the spaces between the color{violet}("cells of tissues") leaving the larger proteins and most of the
formed elements in the color{violet}("blood vessels.")

● This fluid released out is called the color{brown}("interstitial fluid or tissue fluid.")

● It has the same color{violet}("mineral distribution") as that in color{violet}("plasma.")

● Exchange of color{violet}("nutrients, gases"), etc., between the color{violet}("blood") and the color{violet}("cells") always occur through this fluid.

● An elaborate network of vessels called the color{brown}("lymphatic system") collects this fluid and drains it back to the major veins.

● The fluid present in the color{violet}("lymphatic system") is called the color{brown}("lymph.")

● color{violet}("Lymph") is a colourless fluid containing color{brown}("specialised lymphocytes") which are responsible for the immune responses of the body.

● color{violet}("Lymph") is also an important carrier for color{violet}("nutrients, hormones"), etc.

● color{brown}("Fats") are absorbed through color{violet}("lymph") in the color{brown}("lacteals") present in the color{violet}("intestinal villi")

CIRCULATORY SYSTEMS

● The circulatory patterns are of two types – color{brown}("open or closed.")

● color{brown}("Open circulatory system") is present in arthropods and color{violet}("molluscs") in which color{violet}("blood pumped") by the heart passes through large vessels into open spaces or body cavities called color{brown}("sinuses.")

● Annelids and chordates have a color{brown}("closed circulatory system") in which the color{violet}("blood pumped") by the color{violet}("heart") is always circulated through a closed network of color{brown}("blood vessels.")

● This pattern is considered to be more advantageous as the color{violet}("flow of fluid") can be more precisely regulated.