Haemostasis An efficient Mechanism is functional to maintain the circulation as a transport system. It prevents blood loss from damaged vessels. It also prevents cessation of blood flow due to thrombosis. Haemostasis depends upon interaction between the vessel walls , platelets and clotting factors.

Mechanism It occurs in two phases primary and secondary. In primary the damaged vessel constricts and platelets aggregates to form platlet plug. In secondary phase plugs get secure by fibrin clot net work formed by the activation of clotting factors.

What are Clotting Factors ? Clotting factors are proteins , synthesized mainly by liver. Factor II , VII , IX and X are vitamin K dependent. These factors are rich in Glutamic acid, which require carboxylation. The enzyme required for this carboxylation is Glutamic acid carboxylase It is Vit.K dependent

Also known as anti hemeregic factor Vitamin K Also known as anti hemeregic factor

Vitamin K The name vitamin K ,has been derived from Danish word “Koagulation” since it has important role in blood clotting.

FORMS OF Vitamin K Vitamin K exists in two forms. Vit K-1 (phyllo quinone) in green plants Vit K-2 (menaquinone) in animals and (Produced by intestinal bacteria) 3. Vit K3 ( Menadione ) is the synthetic form of this vitamin and is most commonly used.

Food sources

Food sources/ Stability ANIMAL SOURCES Liver Kidney STABILITY It is heat stable but can be destroyed by acids, alkalis and irradiation

Requirements Its requirement is not well established in adults, but it is suggested that 20-100 µg/day is sufficient to meet its daily needs. It is advised to administer a single, prophylactic dose of 1 mg of vitamin K1 to a newborn, on the first day of life.

Group Adequate Intake Children 0-6 months 2.0 micrograms/day Children 7-12 months 2.5 micrograms/day Children 1-3 30 micrograms/day Children 4-8 55 micrograms/day Children 9-13 60 micrograms/day Girls 14-18 75 micrograms/day Women 19 and up 90 micrograms/day Pregnant or breastfeeding 75 micrograms/day 

Absorption and metabolism About half of the Vit K required is derived from dietary sources specially green leafy vegetables, and about half is synthesized by the gut flora. As it is fat soluble, requires the presence of bile for its absorption, which occurs mostly in the upper part of the small intestine.

Functions Vitamin K is essential for the maintenance of the normal levels of various blood-clotting factors, specially prothrombin, factor VII, factor IX, and factor x. These proteins are synthesized in the liver in their inactive forms (zymogen) and get converted to their biologically active forms with the help of vitamin K.

Role in Gamma-carboxylation Formation of the clotting factors requires the vitamin K-dependent carboxylation of glutamic acid residues. This forms a mature clotting factor that contains γ-carboxyglutamate (Gla) and is capable of subsequent activation.

Functions Has a role in osteocalcein and C-reactive proteins synthesis and activation Other physiologic functions include electron transport, growth and photosynthesis. Advanced liver damage, as caused by cancer or Cirrhosis, causes prothrombin deficiency that cannot be alleviated by the administration of Vit K

Deficiency Symptoms Deficiency of vitamin K is seen in the newborns, due to their sterile intestine, particularly in premature infants who show reduced levels of vitamin K, prothrombin, and Christmas factor. Common deficiency symptoms include cutaneous and intramuscular hemorrhages with bluish-red coloration in different parts of the body.

Causes of deficiency Deficiency of Vit K can be caused by : Elimination of sources from diet. Suppression of growth of the intestinal microflora by antibiotics Use for a long period. With impaired lipid absorption such as that resulting from the use of mineral oil as a laxative.

Drug Interactions Many drugs can interfere with the effects of vitamin K. Antacids. Laxatives. Blood Thinners like Aspirin Antibiotics and sulfonamides Drugs for cancer, Seizures and High Cholesterol

Vitamin K antagonists The anticoagulants dicumarol and warfarin act as antivitamins for vitamin K, due to their structural similarities with vitamin K1. They act as competitive inhibitors for the enzymes, which are concerned with the activation of prothrombin and other coagulation factors, and require vitamin K for their activation.

Vitamin K Cycle