Circulation Flashcards
Open circulation
Exchange of materials takes place directly between blood and cells or the tissues of the body. The blood flows with low pressure and does not carry any respiratory pigment called haemoglobin and thus it does not transport respiratory gases
Eg. arthropoda and molluscs
In all vertebrates , higher molluscs and annelids blood is circulated through the body through a network of blood vessels , so the blood does come in contact with the cells. Exchange of materials takes place through an intermediate fluid called lymph. Blood flows with high pressurre and contains respiratory pigments like haemoglobin for transportation of resporatory gases. It is divided into : single and double circulation
Closed circulation
Single circulation
In this type of circulation the blood passes through the heart only once in each cycle eg.fishes. Deoxygenated blood is pumped through the heart to the gills where it is oxygenated and from there to various parts of the body , gets deoxygenated and returns to the heart for the next cycle. The heart of fishes only pumps deoxygenated blood, it is called ‘venous heart’
Double circulation
In double circulation blood passes through the heart twice during each cycle it occurs in mammals and birds .in these animals, heart pumps deoxygenated blood to the lungs for oxygenation And it returns to the heart as oxygenated blood. This is pulmonary circulation. the oxygenated blood is pumped from the heart towards various parts of the body and returns back to the heart as Deoxygenated blood this is systematic circulation. human heart shows double circulation
Blood composition
An average adult pumps 4 to 6 litres of blood. It is a red coloured fluid connective tissue derived from embryonic Mesoderm. it is slightly alkaline, salty and visious fluid. it has two main components: the fluid plasma and the formed elements. these can be separated by centrifugation
Plasma
It consists 55% of the blood it is a straw coloured slightly alkaline vicious fluid and consists of the following:90% water 7 to 8% protein like Prothrombin , fibrinogen , 1% of inorganic salts like Na,K,Mg ,1 to 2% of others like…food(glucose,amino acids, etc) , wastes(urea, uric acid,etc) , regulators (hormones,enzymes) , anticoagulators (heparine) , cholestrol and antibiotics , dissolved gases(O2, CO2,etc).
Formed elements
The blood cells produced in the body are collectively called formed elements. There are 3 types : red blood cells, white blood cells and platelets
Rbc
They are enucleated. The red colour in rbcs is due to an oxygen vpcarrying pigment haemoglobin in its cytoplasum. The average life of an rbc is 120 days
The process of formation of rbcs
Erythropoiesis
RBCs are produced from and in…
From haemocytoblasts/reticulocytes in a foetus it is formed in liver and spleen and in adults it is mainly in the red bone marrow. The hormone erytropoietin produced by the kidney cells stimulates the bone marrow for production of RBCs
Increase in no of RBCs
Polycythemia
Decrease in no of RBCs
Erythrocytopenia
Mature erythrocytes
Mature erythrocytes is deviod of nucleus, mitochondria or orther membrane bond cell organelles. Its cytoplasm is rich in haemoglobin and o2 carrying proteinaceous pigment that gives red colour to the rbcs and blood. It also contains an enzyme, carbonic anhydrase. Erythrocytes are responsible for transport of respiratory gases, maintaining pH and viscosity of blood. They also contribute on the process of blood clothing.
Hematocrit
Hematocrit is the ratio of the volume of RBCs to total blood volume of blood. = RBCs upon blood. It is different for men and women
Leucocytes or WBCs
Leucocytes are colourless, nucleated and amoeboid ells larger than rbcs.
Diapedesis
Due to amoeboid movement of WBCs they can move out of the capillary walls by the process of diapedesis
Decrease in no of WBCs
Leucopenia
Increase in no of WBCs
It is called leucocytosis and it is temporary. It is due to infection.
It also occurs during pregnancy and in new borns. Uncontrolled increase in WBCs is a type of blood cancer called leukemia
Granulocytes
These are wbcs with a granular cytoplasm also called Polymorpho nuclear leucocyte cells. They are formed from myeloid stem cells and once formed they do not divide. They consist 72% of total wbcs.they contain various secretions and enzymes based on their staining property they are classified into 3 types: neutrophils,cyanophils/basophils,eosinophils/acidophills.
Neutrophils
These are able to perform amoeboid movements and phagocytosis. They are responsible for destroying pathogens by the process of phagocytosis. Pus is the mixture of dead neutrophils , damaged tissues and dead microbes
Basophils/cyanophils
They are present in allergic or infected conditions only.
They secrete heparin,histamine and serotonin
Eosinophils/acidophills
They destroy antigen-antibody complex by phagocytosis. Their no increases in allergic conditions and they show antihistaminic property. They are also responsible for detoxification as they produce antitoxins.
Agranulocytes
They are 28% of WBCs. Their cytoplasm is without granules. They are formed from lymphoid stem cells and can divide by mitosis. Nuclei is not lobulated. There are 2 types: lymphocytes and monocytes
Lymphocytes
Lymphocytes are the smallest WBCs .they constitute about 25 to 30% of total WBCs. Depending upon function two types of lymphocytes are present as be in lymphocytes and T-lymphocytes B-lymphocytes mature in bone marrow and are responsible for antibody production or hormonal immunity. It is a highly specific antigen. T-lymphocytes mature in thymus and are responsible for cell mediated immunity. helper T-cells killer T-cells memory T-cells and suppress T-cells are four main subtypes of T-lymphocytes
Monocytes
They from 3 to 5% of WBCs. monocytes or actively motile and give rise to macrophages. they are mainly phagocytic and destroy the bacteria and dead or damaged tissue by phagocytosis
If the number of thrombocytes decrease
Thrombocytopenia. This can cause internal bleeding.
Main function of thrombocytes
Platelet secrete platelet factors which are essential in blood clotting
What is platelet plug or thrombus
Platelets seal the ruptured blood vessels by formation of platelet plug or thrombus they secrete serotonin a local vasoconstrictor
Blood clotting or coagulation of blood
Clotting or coagulation of blood maybe intrinsic or extrinsic these processes involve interaction of various substances call clotting factors buy a stepwise or a casket mechanism .interaction of these factors in a cascade manner leads to formation of enzyme thrombin. thromboplastin helps in the formation of enzyme prothrombinase.This enzyme in activates heparin and it also converts inactive prothrombin into its active thrombin. Thrombin converts soluble blood protein fibrinogens into soluble fibrin. Fibrin forms a mess in which platelets and other blood cells are trapped to form the cloth.
