Blood Composition and Functions PDF

# BLOOD ## Composition of blood: - About 55% is composed of plasma. - 45% is made of three major types of cells: - The red blood cells (erythrocytes). - The white blood cells (leucocytes). - The platelets (thrombocytes). ## GENERAL FUNCTIONS OF THE BLOOD 1. Respiration: it carries O2...

# BLOOD ## Composition of blood: - About 55% is composed of plasma. - 45% is made of three major types of cells: - The red blood cells (erythrocytes). - The white blood cells (leucocytes). - The platelets (thrombocytes). ## GENERAL FUNCTIONS OF THE BLOOD 1. Respiration: it carries O2 from the lung to the tissue and Co2 from the tissue to the lung. 2. Temperature regulation. 3. Nutrition: it carries food absorbed from intestine to the cells which use them. 4. Excretion: it carries the waste products to the excretory organs. 5. Immunity: it transports leucocytes, antibodies. 6. It carries hormones from the endocrinal glands to regulate the functions of the organs. ## PLASMA ### Composition of plasma: 1. Water 90% 2. Plasma proteins 7.1% formed of: - Plasma albumin 4-4. 5 gm%. - Plasma globulins 2.5 gm%. - The albumin/globulin ratio (A/G) is 1.2-1.6 - Blood coagulation factors e.g.: - Fibrinogen 400 mgm%. - Prothrombin 10 mgm%. ### Significance of A/G ratio: - It decreased in: - Decrease plasma albumin level as in: - Liver diseases because the hepatic synthesis is depressed. - Decrease intake as in malabsorption and malnutrition. - Severe burns due to loss of albumin by skin. - Increase plasma globulins level as in severe infections. ### Functions of plasma proteins: 1. Nutrition. The plasma proteins are used in protein metabolism. 2. Hogen, prothrombin and thromboplastin are 3. va of blood. 4. haintain the A.B.P. 5. in is important for the retention of water within ## HAEMOSTASIS AND BLOOD COAGULATION ### Definition of haemostasis: - It is stoppage (prevention) of bleeding from injured blood vessel. ### Mechanisms of haemostasis: 1. **Local Vascular spasm** - If the blood vessel is injured its wall be contracted to reduce the blood loss. 2. **Platelet plug formation** - When a blood vessel is damaged => the endothelium is removed and the underlying collagen fibers are exposed. - exposed to the collagen fibers in vascular wall => on occurs. 3. **Blood Coagulation** - The conversion of the soluble fibrinogen into twork with blood cells in its meshes, by complex reactions involve clotting factors). 4. **Clot retraction** - It means shrinkage of the blood clot to decrease the lumen of the damaged vessel and the clot become firmer. 5. **Repair of the damaged blood vessels** ### Mechanisms of Blood Coagulation: - Blood coagulation can occur through the following four stages: 1. **Formation of prothrombin activator**, through intrinsic or extrinsic mechanism. 2. **Conversion of prothrombin into thrombin by prothrombin activator**. 3. **Conversion of fibrinogen into soluble fibrin by thrombin.** 4. **Conversion of soluble fibrin into insoluble fibrin in presence of Ca++ and F XIII(fibrin stabilizing factor).** ### Extrinsic mechanism 1. It is initiated by a factor not normally found in blood but added externally from the injured tissue. 2. Initiated by injury of blood vessel 3. It occurs in *vivo* only ### Intrinsic mechanism 1. All needed clotting factors are found in the blood. - i.e. it depends on the intrinsic components of blood. 2. It is initiated by contact with rough surface. 3. It occurs in *vivo* and *vitro* 4. It is slow (occurs within 3-6 minutes) - evel is so essential for normal blood - - bsence of Ca++ => blood clotting doesn't ## Anti-coagulants ### Definition - They are substances which prevent or delay coagulation of blood. ### Types of anticoagulants **(a)** Anticoagulants in *vivo:* - It means "prevention of blood coagulation inside the body". - (I) Heparin - (II) Dicoumarol | | Heparin | Dicoumarol | | :------- | :---------- | :---------- | | Origin | Animal in origin | Plant in origin | | Latent period of action | After few minutes | After two days | | Duration of action | 4-6 hours | Few days | | Route of administration | I.V. or I.M. injection | Oral | | Mechanisms of action | Anti-prothrombin activator. <br> Anti-prothrombin. <br> Anti-thrombin. <br> In vivo, in vitro | Competitive inhibition of vitamin K (i.e. anti F II, VII, IX and X). <br> In vivo only | | Site of action | In vivo, in vitro | In vivo only | | Dose test | Coagulation time | Prothrombin time | | | Protamin sulphate | Vitamin K. | - I (stable factor), F IX (Christmas factor), F X thesized in the liver and catalyzed by Vit K. **(b)** Anticoagulants in *vitro*: - It means prevention of blood coagulation outside the body. - It is done by: - (1) Cold: Delays clotting. - (2) Collecting the blood in smooth paraffin or silicon lined vessels. - (3) Decalcifying agents: - a) K Oxalate: => Precipitates Ca oxalate. - b) Na citrate: => combines with Ca++ to form unionized Ca compound. - c) EDTA: "Ethyl diamine tetra acetic acid" => it is chelating calcium ions. - (4) *Defibrination*: => Removals of the fibrin.