CVS

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cardiovascular system

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CARDIOVASCULAR SYSTEM:

CARDIOVASCULAR SYSTEM

BLOOD:

BLOOD Blood is connective tissue It provides one of the means of communication between the cells of different parts of the body and the external environment.

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It carries Oxygen from lungs to the tissue and CO 2 from the tissues to the lungs for Excretion Nutrients from the alimentary tract to the tissues and cell wastes to the excretory organs, principally the kidneys Hormones secreted by endocrine glands to their target glands and tissues Heat produced in active tissues to other less active tissues Protective substances e.g.: antibodies to area of infection Clotting factors that coagulate blood, minimizing bleeding from ruptured blood vessels

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Blood makes up about 7% of body weight i.e. 5.6 litres in a 70 Kg man. Blood in the blood vessels is always in motion because of the pumping action of the heart. The continual flow maintains a fairly constant environment for the body cells. Blood is composed of a straw-colored transparent fluid, plasma, in which different types of cells are suspended. Plasma constitutes 55% and cells about 45% of blood volume

PLASMA :

PLASMA Constituents of Plasma are water (90-92%) and dissolved substances include Plasma proteins---- Albumins,globulins,antibodies,carrier molecules, proteolytic Enzymes & Clotting factors Inorganic salts Nutrients principally from digested foods Waste materials Hormones Gases

CELLULAR CONTENT OF BLOOD:

CELLULAR CONTENT OF BLOOD Cellular content of blood are Red blood cells (R.B.C ) / Erythrocytes White blood cells (W.B.C ) / Leukocytes Platelets / Thrombocytes

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Erythrocytes Carriage of O 2 & CO 2 Leukocytes Defence of the host against bacterial / viral / foreign body invasion, defence against cancer Thrombocytes Hemostasis arrest of bleeding

Red Blood Corpuscles:

R ed B lood C orpuscles Normal R.B.C count in Males—5millions/cmm Females----4.5millions/cmm Infants-----6-7millions/cmm Foetus------7-8millions/cmm Increase in R.B.C count is known as Polycythemia Decrease in R.B.C count is known as Anaemia

white Blood Corpuscles:

w hite B lood C orpuscles Normal W.B.C count is 4,000-11,000/cmm If count goes below 4,000/cmm, it is known as Leucopenia If total WBC count goes beyond 11,000/cmm it is known as Leucocytosis Leukaemia is malignant disease in which total WBC count goes beyond 1,00,000 / cmm.

DIFFERENTIAL W.B.C:

DIFFERENTIAL W.B.C Eosinophils---150-400/cmm--0-5% Basophils---100/cmm--0-5% Neutrophils---3000-6000/cmm--60-70% Lymphocytes--25% Monocytes--5%

ERYTHROCYTES:

ERYTHROCYTES Human RBC is a circular biconcave cell without a nucleus and with diameter of about 7.5µ It is considered as a kind of a living bag containing haemoglobin.

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The biconcavity of RBC has some advantages as mentioned below …. Because of the biconcavity, the thickness of RBC in its central part is not great, so that O 2 does not have to travel a great distance for the diffusion. The presence of biconcavity increases the surface area of RBC, so that O 2 gets a bigger area for diffusion. Because of concavity, the RBC can squeeze itself through a capillary more easily.

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RBC is devoid of mitochondria, ribosomes endoplasmic reticulum and centriole. Some special chemical substances like blood group antigens are associated with RBC cell membrane.

ERYTHROPOIESIS:

ERYTHROPOIESIS The generation of erythrocytes is called Erythropoiesis It starts in 3rd week of intrauterine life and continues as long as the person remains alive. Blood forming tissues, which produce the RBC, WBC and platelets are usually divided in to two great classes i.e. 1. Myeloid tissue —means the red bone marrow. It produces the RBC granulocytes, Monocytes and platelets. 2. Lymphoid tissue —includes the lymph nodes, thymus gland and the spleen. They produce lymphocytes.

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Bone marrow is of two types Red bone marrow--because it has a red color. Erythropoiesis occurs in the red bone marrow only. Yellow bone marrow—It looks yellowish Factors influencing Erythropoiesis are … Haemopoetic growth factors---Erythropoietin, Interleukins, stem cell factor, Vitamins---Vit B 12 , folic acid, pyridoxine and vit C Iron and copper

ERYTHROPOIETIN:

ERYTHROPOIETIN Erythropoietin is most important haemopoietic growth factor which causes erythropoiesis. Stimulus for erythropoietin is hypoxia. When tissues of the body become hypoxic, the kidneys produce erythropoietin

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Tissue hypoxia ↓ Kidneys secrete erythropoietin in to the blood ↓ Bone marrow increase erythropoiesis ↓ Red blood cell number rise ↓ Increased blood oxygen carrying capacity reverses tissue hypoxia

HAEMOGLOBIN :

HAEMOGLOBIN Haemoglobin is present inside the RBC’s. It is required for Transport of O 2 Transport of CO 2 It also haves behaves as a blood buffer. Normal values for the concentration of Hb is around 15gm/100ml In males it is between 14 to 17gm/100ml In females it is between 12 to 16gm/100ml

BLOOD GROUPS:

BLOOD GROUPS Individuals have different types of antigen on the surfaces of their red blood cells. These antigens are inherited, determine the individuals blood group. Individuals make antibodies to these antigens, but not to their own type of antigen, since if they did the antigens and antibodies would react, causing a transfusion reaction, which can be fatal. There are many different collections of red cell surface antigens, but the most important are the ABO and the Rhesus systems.

THE ABO SYSTEM:

THE ABO SYSTEM About 55% of the population has either A-type antigens (Blood group A), B-type antigens (Blood group B) or both (Blood group A&B) on their red cell surface. The remaining 45% have neither A nor B type antigens (Blood group O)

THE RHESUS SYSTEM:

THE RHESUS SYSTEM The red blood cell membrane antigen important here is the Rhesus antigen (Rh). About 85% of people have this antigen, they are rhesus positive (Rh+) and therefore do not make anti rhesus antibodies. The remaining 15% have no rhesus antigen, they are rhesus negative (Rh-), Rh- are capable of making anti rhesus antibodies.

THE ABO SYSTEM OF BLOOD GROUPING:

THE ABO SYSTEM OF BLOOD GROUPING BLOOD GROUP ANTIGEN+ANTIBODY PRESENT AS DONOR, IS AS RECIPIENT, IS A Antigen A & Makes Anti B Compatible with A and AB Incompatible with B and O Compatible with A and O Incompatible with B and AB B Antigen B & Makes Anti A Compatible with B and AB Incompatible with A and O Compatible with B and O Incompatible with A and AB AB Antigens A&B & Makes neither Anti A nor Anti B Compatible with AB only Incompatible with A, B and O Compatible with all groups UNIVERSAL RECIPIENT O Neither A nor B & Makes both Anti A & Anti B Compatible with all groups UNIVERSAL DONOR Compatible with O only Incompatible with A, B and AB

ANAEMIAS :

ANAEMIAS In anaemia there is not enough haemoglobin available to carry sufficient oxygen from the lungs to supply the needs of the tissues. The classification of anaemia is based on the cause Impaired erythrocyte production Iron deficiency anaemia Megaloblastic anaemia Hypoplastic anaemia Increased erythrocyte loss Haemolytic anaemia Normocytic anaemia

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TERM DEFINITION EXAMPLE Normocytic Cells normal sized Acute haemorrhage Microcytic Cells smaller than normal Iron deficiency Macrocytic Cells bigger than normal Vit.B 12 /Folic acid deficiency Hypocromic Cells paler than normal Iron deficiency anaemia Haemolytic Rate of cell destruction raised Autoimmune disease & sickle cell anaemia

IRON DEFICIENCY ANAEMIA :

IRON DEFICIENCY ANAEMIA Normal daily requirement of iron intake in men is about 1-2mg, derived from meet and highly colored vegetables. In women it is 3mg because of blood loss during menstruation and to meet the needs of growing fetus during pregnancy. In this type of anemia erythrocytes are microcytic and hypochromic because their haemoglobin content is low.

MEGALOBLASTIC ANEMIA :

MEGALOBLASTIC ANEMIA Maturation of erythrocytes is impaired when deficiency of Vit.B 12 or folic acid occurs and abnormally large erythrocytes (megaloblasts) are found in blood During normal erythropoiesis several cell divisions occur & daughter cells at each stage are smaller than parent cell because there is not much time for cell enlargement between divisions

VIT. B12 DEFICIENCY ANAEMIA:

VIT. B 12 DEFICIENCY ANAEMIA PERNICIOUS ANAEMIA Most common form of Vit. B 12 deficiency anaemia Occurs more often in females than males at age of 45 to 65 years It is an autoimmune disease in which auto antibodies destroy intrinsic factor(IF) and parietal cells in the stomach 2. Dietary deficiency of Vit. B 12 3. Other causes of Vit. B 12 deficiency includes

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Gastrectomy leaves fewer cells available to produce IF after partial resection of stomach Chronic gastritis, malignant disease and ionizing radiation—damage gastric mucosa including parietal cells that produce IF Malabsorption —If terminal ileum is removed or inflamed, the vitamin cannot be absorbed Eg: Crohn’disease.

COMPLICATIONS OF VIT. B12 DEFICIENCY ANAEMIA :

COMPLICATIONS OF VIT. B12 DEFICIENCY ANAEMIA These may appear before the signs of anaemia. Because Vit. B 12 is used in myelin production, deficiency leads to irreversible neurological damage, commonly in the spinal cord. Mucosal abnormalities, such as glossitis are also common, although they are reversible.

FOLIC ACID DEFICIENCY ANAMEIA:

FOLIC ACID DEFICIENCY ANAMEIA Deficiency in the bone marrow causes a form of megaloblastic anaemia identical to that seen in Vit. B 12 deficiency, but not associated with neurological damage. It may be due to : Dietary deficiency, e.g. in infants if there is delay in establishing a mixed diet, in alcoholism ,in anorexia and in pregnancy when the requirement is raised. Malabsorption from the jejunum caused by e.g. celiac disease, oral anti convulsant drugs Interference with folate metabolism by e.g. cytotoxic and anticonvulsant drugs.

HYPOPLASTIC AND APLASTIC ANAEMIAS:

HYPOPLASTIC AND APLASTIC ANAEMIAS Hypoplastic and Aplastic Anaemias are due to varying degrees of bone marrow failure. Bone marrow function is reduced in hypoplastic anemia, and absent in aplastic anemia. Since the bone marrow produces leukocytes and platelets as well as erythrocytes, leucopenia and thrombocytopenia are likely to accompany diminished red cell numbers. when all three cell types are low, the condition is called pancytopenia, and accompanied by anemia, diminished immunity and a tendency to bleed.

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HAEMOLYTIC ANAEMIAS These occur when red cells are destroyed while in circulation or are removed prematurely from the circulation because the cells abnormal or the spleen in overactive. CONGENITAL HAEMOLYTIC ANAEMIAS Genetic abnormalities leads to synthesis of abnormal haemoglobin and increased red cell membrane friability, reducing their oxygen carrying capacity and life span. The most common forms are Sickle cell anaemia and Thalassaemia

SICKLE CELL ANAEMIA:

SICKLE CELL ANAEMIA The abnormal haemoglobin molecules become misshapen when deoxygenated, making the erythrocytes sickle shaped. If the cells contain a high proportion of abnormal molecules, sickling is permanent. The life span is reduced by early haemolysis which causes anaemia. Blacks are more effected than other races.

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Complications Pregnancy, infection and dehydration predispose to the development of sickle crisis due to intra vascular clotting and ischaemia causing severe pain in long bones, chest or the abdomen. The formation of gallstones (Cholelithiasis) and inflammation of gall bladder occurs (Cholecystitis ).

THALASSAEMIA :

THALASSAEMIA There is reduced globin synthesis with resultant reduced haemoglobin production and increased friability of the cell membrane leading to early haemolysis. Severe cases may cause death in infants or young children.

HAEMOLYTIC DISEASE OF THE NEW BORN:

HAEMOLYTIC DISEASE OF THE NEW BORN In this disorder, the mothers immune system makes antibodies to the babys red cells, causing haemolysis and phagocytosis of fetal erythrocytes. A Rh- mother carries no Rh antigen on her RBC, but she has the capacity to produce anti Rh antibodies. If she conceives a child fathered by a Rh+ man, and the baby inherits the Rh antigen from him, the baby may also be Rh+ i.e different from the mother. During pregnancy, the placenta protects baby from the mothers immune system, but at delivery a few fatal RBC may enter the maternal circulation.

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Because they carry antigen foreign to the mother, her immune system will be stimulated to produce antibodies to it The red cells of second and subsequent Rh+ babies are attacked by these maternal antibodies, which can cross the placenta and enter the fetal circulation. In most severe cases the baby dies in the womb from profound anemia In less serious circumstances baby is born with some degree of anemia, which is corrected with blood transfusion

ACQUIRED HAEMOLYTIC ANEMIA:

ACQUIRED HAEMOLYTIC ANEMIA There are several causes Chemical agents : Some drugs when taken long term in large doses e.g.. Sulphonamides Chemicals encountered in the general or work environment eg. Lead, arsenic compounds Toxins produced by microbes eg. Streptococcus, pyrogens, Clostridium perfringes Autoimunity: Individuals makes antibodies to their own red cell antigens, causing haemolysis Blood transfusion reactions :

NORMOCYTIC NORMOCROMIC ANEMIA:

NORMOCYTIC NORMOCROMIC ANEMIA The cells are normal but the numbers are reduced, and the proportion of reticulocytes in the blood may be increased as the body tries to restore erythrocyte numbers to normal. This occurs In many chronic conditions eg. In chronic inflammation Following severe haemorrhage In haemolytic disease

References:

References http://en.wikipedia.org/wiki/Blood http://en.wikipedia.org/wiki/Erythropoiesis http://en.wikipedia.org/wiki/Plasma http://en.wikipedia.org/wiki/Anemia http://en.wikipedia.org/wiki/Thrombocytopenia http://en.wikipedia.org/wiki/Normochromic_anemia http://en.wikipedia.org/wiki/Acquired_haemolytic_anaemia http://en.wikipedia.org/wiki/Erythropoiesis http://en.wikipedia.org/wiki/Red_blood_corpuscles http://en.wikipedia.org/wiki/Blood_grouping_and_crossmatching

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