Lecture 5 Blood Physiology PDF

Lecture 5 Blood Physiology Blood - Blood is part of the ECF which circulates within the cardiovascular system. - Blood volume is about 80 ml/kg (5 – 5.5 liters) General functions of the blood: 1-Transport → O2 & CO2 → Nutrients → Hormones → Removal of waste...

Lecture 5 Blood Physiology Blood - Blood is part of the ECF which circulates within the cardiovascular system. - Blood volume is about 80 ml/kg (5 – 5.5 liters) General functions of the blood: 1-Transport → O2 & CO2 → Nutrients → Hormones → Removal of waste products. 2- Regulatory functions → PH of the blood → Body temperature → Regulation of ABP 3- Protective function → Gamma globulin which form antibodies for immunity. → White blood cell (WBC) phagocytosed microorganism → Clotting factors prevent blood loss. Composition of the blood: Blood Plasma (55% of blood volume) Blood cells (45% of blood volume)  Plasma proteins: Concentration: 6 – 8 gm /dl Types: (1) Albumin (3.5 – 5 gm/ dl) (2) Globulin (2.4 – 2.7 gm/ dl) (3) Fibrinogen (0.2 – 0.4 gm/ dl) (4) Clotting factors and hormones N.B. All plasma proteins except the -globulins are synthesized in the liver. Functions of plasma proteins: 1) Blood viscosity: fibrinogen and RBCs give the blood its viscosity 2) Plasma proteins create an osmotic pressure equal 25 mmHg at capillary 3) Carry many substances to be circulated with the blood as hormones & vitamins. 4) Blood clot formation as most of clotting factor are PP. 5) Help immunity which is the function of -globulins  Red blood corpuscle (RBCs) Normal RBCs count: – Child : 3.5 – 4.5 million/ mm3 – Adult male : 5 - 5.5 million/ mm3 – Adult female : 4.5 – 5 million/ mm3 Life span of RBCs”: live in the circulation for an average of 120 days. Contents: - hemoglobin (34% of RBC volume) - not contain nucleus or mitochondria Normal Hemoglobin content: ▲ Adult male →14 – 18 gm/ dl. ▲Adult female → 12 – 16 gm/ dl. ▲ Child at 5 years → 12 gm/ dl. ▲ Newborn → 18 gm/ dl. Functions of RBCs: 1. The main function is the carriage of O2. 2. Share in CO2 carriage in the blood. 3. Give the blood its viscosity Anemia: deficiency of hemoglobin (< 14 gm/dl for men and < 12 gm/dl for women) Polycythemia: Increase RBCs number above normal (6-8 millions/ mm3).  Erythropoiesis Definition: It is the process of new RBC’s production. Sites of Erythropoiesis: red bone marrow 1- After birth, all bones contain red bone marrow 2- After the age of 20 years, the red bone marrow is present only in membranous bones (vertebrae, sternum, ribs, and ilia) Factors affecting erythropoiesis: 1- O2 supply to the tissue: ↓ O2 to tissue → increase RBCs production 2- Nutritional factors: The diet must contain → protein → Mineral (iron, copper, cobalt) → Vitamins (vit B12 & folic acid) 3- Hormonal factors: thyroid hormone & androgens. 4- Healthy bone marrow. 5- Healthy liver Total count → 4000 – 11000/mm3 Life span of leukocytes: Granulocytes live for 4 – 5 days. The lymphocytes & monocytes may live for months even years Functions of leukocytes: have powerful defense mechanisms (body immunity) 1. Neutrophils → phagocytosis of bacteria 2. Eosinophils → killing of parasites 3. Lymphocytes: - B lymphocytes → formation of antibodies - T lymphocytes → killing of viruses & tumor cells  Immunity Innate (non specific) Acquired (specific)  Innate (non specific) immunity 1) Mechanical barriers - The skin & epithelial lining of GIT, respiratory and urinary tracts. 2) Chemical barriers b) Mucous secretion of the respiratory tract. c) Acid secretion of the stomach. 3) Non specific cellular defense mechanisms: a) Phagocytic cells (neutrophils, eosinophils & macrophages). b) Natural killer cells  Acquired (Specific) immunity It depends on the B & T lymphocytes.  It means the ability of the immune system to respond specifically to antigens (bacteria, viruses, tumor cells & foreign tissue). Types of Acquired Immunity a) Humoral immunity b) Cell-mediated immunity 1) Humoral immunity: → depend on B lymphocytes → The B-lymphocytes produce specific antibodies → It is the major defense against bacterial infection  T - cell immunity → It's a major defense against viruses, fungi & tumor cells → It is also responsible for rejecting transplanted organs (cytotoxic T – cells). → Types of T-lymphocytes : 1) Helper T – cells → responsible for the regulation of all the immune system 2) Cytotoxic T – cells. 3) Suppressor T – cells. N.B.: TH-cell are destroyed by the AIDS virus, which leaves the body almost totally unprotected against infectious diseases.  Blood Platelets Shape →oval or round discs → non-nucleated → 1 - 4 micrometer in diameter Count: 150,000 – 400.000/mm3. Life span: 10 days  They are concerned with hemostasis through: 1) Induces vascular spasm (serotonin & thromboxane A2 ) 2) Formation of primary platelet plug 3) Release of platelets phospholipid ( Pf 3 ) which is essential for clotting mechanism. 4) Stabilization of blood clot (fibrin – stabilizing factor) 5) Clot retraction (Ca2+ ). 6) Repair of damaged vessels wall ( platelet derived -growth factor)  Hemostasis Def: Hemostasis is the stoppage of bleeding from injured blood vessels. Steps: 1. Vascular spasm → platelet release VC substances as ( thromboxane A2) 2. Platelet Plug Formation 3. Blood Clot Formation (Coagulation) Blood Clot Formation (Coagulation) Within 3- 6 m blood clot will be formed The main three steps of this series of reactions are: 1) Formation of Prothrombin activator complex 2) Conversion of Prothrombin into thrombin Prothrombin activator complex Prothrombin Thrombin 3) Thrombin catalyzes the conversion of fibrinogen to a fibrin threads Thrombin Fibrinogen Fibrin threads N.B. Role of Ca+2 in blood clotting:  Ca+2 required for acceleration of most of blood clotting reactions  Absence of Ca+2 prevent blood clotting.  Citrate and oxalate salts (precipitate Ca+2) used as in vitro anticoagulants. Role of vit. K in hemostasis: Vit K is necessary for the formation of factors II, VII, IX, X, and protein C. In the absence of vit K  bleeding disorders.  Bleeding Disorders Purpura Haemophilia  Bleeding Disorders 1- Purpura - It is due to a deficiency of blood platelets (count below 50,000/mm3) - It is accompanied by prolongation of bleeding time. 2- Vitamin K-deficiency - As in cases of obstructive jaundice and in cases of severe liver diseases. 3- Hemophilia - It is a congenital sex-linked, recessive disease carried on the X chromosome. - It is carried by females and manifested always in males. - It is characterized by: →Excessive bleeding after mild trauma. → Prolongation of coagulation time. - Types of hemophilia; 1. Hemophilia A: is the classic hemophilia. It is caused by a deficiency of factor VIII and represents 85% of cases of hemophilia. 2. Hemophilia B: is due to the absence of factor IX. 3. Hemophilia C: is due to the absence of factor XI.