Downloaded from

Transcription

1 POINTS TO REMEMBER : 18. Bdy Fluids and Circulatin Bld: A special cnnective tissue that circulates in principal vascular system f man and ther vertebrates cnsisting f fluid matrix, plasma and frmed elements. Plasma : The liquid part f bld r lymph which is straw clured, viscus fluid cnstituting nearly 55 per cent f bld percent f plasma is water and 6-8% prteins. Fibringen, glbulin and albumins are the majr prtein fund in plasma. Fibringen is required in bld cltting r cagulatin f bld. Glbulins invlved in defense mechanism f the bdy. Albumin helps in smtic balance f bld. Plasma als cntains small amunts f minerals, glucse, amin acids, lipids etc. Plasma withut the cltting factrs is called serum. Frmed elements : Erythrcytes : Als knwn as RBC (red bld cells) is the mst abundant f all the cells f bld millin RBC fund per mm-3 f the bld. Prduced frm the red bne marrw in the adult. RBCs devid f nucleus in mst f mammals. Bicncave in shape Red in clr due presence f cmplex cnjugated prtein called haemglbin gm f haemglbin present per 100 ml f bld in a healthy adult. RBCs have average life span f 120 days after which is destryed in the spleen. Spleen is cmmnly knwn as the graveyard f RBCs. Leukcytes : Als knwn as white bld cells (WBC). They are clrless due t lack f haemglbin. They are nucleated and relatively lesser in number which averages mm-3 f bld. We have tw main categry f WBC; Granulcytes Neutrphils Basphils Esinphils Agranulcytes. Lymphcytes Mncytes.

2 Neutrphils (60-65%) f the ttal WBCs are phgcytic in nature. Basphils (0.5-1 %), secretes histamine, sertnin and heparin and als invlved in inflammatry reactins. Esinphils (2-3 %) resist infectin and als assciated with allergic reactin. Lymphcytes (T cells and B cells) cnstitute percent and invlved in the immune respnse f the bdy. Mncytes (10-15%), becmes macrphages. Thrmbcytes : Als knwn as bld platelets. Prduced frm fragmentatin f megakarycytes. Bld nrmally cntain 1, 500, 00 3, 500, 00 platelets mm-3. Invlved in releasing thrmbplastin required t initiate bld cagulatin. BLOOD GROUPS : Tw bld gruping mechanisms ABO and Rh system. ABO gruping : ABO gruping is based n the presence r absence f tw surface antigens n the RBCs namely A and B. Plasma f different individuals cntains tw natural antibdies, anti A and B. In a mismatched transfusin the antigen f the dnr reacts with antibdy f the recipient t cause a reactin calledclumping f agglutinatin. Persn with bld grup O has n antigen hence can dnate bld anybdy, called universal dnr. Persn with bld grup AB has n antibdy in his plasma hence can receive bld frm anybdy, called universal recipient. Rh gruping : Anther antigen, the Rh antigen similar t ne present in Rhesus mnkeys (hence Rh), is als bserved n the surface f RBCs n majrity (nearly 80 %). Persn with Rh antigen is said t be Rh psitive (Rh+). Persn withut Rh antigen is said t be Rh negative (Rh-). Persn with Rh- bld transfused with Rh+ bld, frms anti Rh antibdy and destry the Rh+ RBCs. A special case f Rh incmpatibility (mismatching) has been bserved between the Rh- blds f pregnant mther with the Rh+ bld f the fetus. During parturitin the Rh+ fetal bld mixed with the Rh- maternal bld, hence anti Rh antibdy frmed in mthers bld. In successive pregnancy the anti Rh antibdy frm mther s bld leaks int the fetal bld and destry the Rh+ RBCs.

3 This caused HDN (haemlytic disease in new brn) r Erythrblastsis fetalis. This can be prevented by administering anti-rh antibdy t the mther immediately after the delivery f the first child. COAGULATION OF BLOOD : Injury t the bld vessel leads t lss f bld called haemrrhage. There is an intrinsic mechanism t stp haemrrhage is called haemstasis r cagulatin f bld r bld cltting. Clt r cagulum is frmed mainly f a netwrk f threads called fibrins in which dead and damaged frmed elements f bld are trapped r entangled. Fibrin is frmed by the cnversin f inactive fibringens in the plasma by an enzyme called thrmbin. Thrmbin frmed frm inactive prthrmbin f the plasma due t presence f enzyme thrmbkinase. All these activatin required the initial cltting factr called thrmbplastin either released frm the injured tissue r platelets. Calcium ins play a very imprtant rle in the cagulatin f bld. Lymph The clrless mbile fluid cnnective tissue drains int the lymphatic capillaries frm the intercellular spaces. Cmpsitin : It is cmpsed f fluid matrix, plasma, white bld crpuscles r leuccytes. Cntains less amunt f prtein than plasma. Devid f RBCs. Functins : It drains excess tissue fluid frm extra cellular spaces back int the bld. It cntains lymphcytes and antibdies. It transprt digested fats. CIRCULATORY PATHWAYS : Open circulatry system :

4 Fund in arthrpds and mllusks. Bld frm the heart pumped int the pen spaces in the bdy cavity called sinuses. The bdy cavity remained filled with bld (haemlymph) called haemcel. Clsed circulatry system : Fund in annelids, echinderms and all chrdates. Bld frm the heart pumped int definite bld vessels. Bld circulated in a wide netwrk f bld vessel thrughut the bdy. Bld circulated in a regulated manner. Heart and circulatin in vertebrates : Fishes: have 2 chambered hearts with ne atrium and ne ventricle. Amphibian and reptilian (except crcdile) has three chambered heart with tw atria and ne ventricle. Crcdiles, birds and mammals pssesses a 4-chambered heart with tw atria and tw ventricles In fishes the tw chambered heart pumped dexygenated bld t the gills fr xygenatin and then circulated t the bdy. (singlecirculatin) In amphibians and reptilians the left atrium receives xygenated bld frm the lungs and right atrium receives dexygenated bld frm the bdy. Bld frm the atria pumped int the ventricle frm which the mixed bld pumped int the bdy. (Incmplete duble circulatin). In birds and mammals xygenated and dexygenated bld received by left and right atria respectively passed int ventricle f their side. The ventricles pump it ut withut any mixing up. (duble circulatin) HUMAN CIRCULATORY SYSTEM : Heart : Originated frm embrynic mesderm. Situated in the thracic cavity, in between tw lungs, slightly tilted twards left. It has the size f the clenched fist. Heart is cvered by a duble walled bag, pericardium. Our heat is fur chambered, tw relatively smaller upper chamber called atria and tw lwer larger chamber calledventricles. Tw atria are separated by thin muscular wall called inter-atrial septum. A thick walled inter-ventricular septum separates tw ventricles. Atrium and ventricle f same side is separated by a thick fibrus tissue called the atri-ventricular septum. Each f atri-ventricular septa is prvided with an pening thrugh which the atrium and ventricle f same side are cnnected, called atri-ventricular pening. Right atri-ventricular pening is guarded by tricuspid valve. Left atri-ventricular pening is guarded by bicuspid r mitral valve. The right ventricle pens int systemic arta and left ventricle pens int pulmnary arta. Bth the arta is guarded by semilunar valves. The valves in the heart allw unidirectinal flw f bld i.e. frm atria t ventricles and frm ventricles t their respective arta. Cnducting system f human heart : The entire heart is made f cardiac muscles. The wall f the ventricle is much thicker than the atria. A patch f ndal tissue is present in the right upper crner f the right atrium called the Sin-atrial nde(s A Nde). Anther ndal tissue present in the psterir t the inter-ventricular septum called A V Nde (Atri-ventricular nde).

5 A bundle f ndal fibres, atri-ventricular bundle ( AV bundle) cntinued as A V bundle thrugh the inter-ventricular septum and divided int right and left A V bundle, als called bundle f His. The bundle f His gives rise t prfuse branches t the wall f the ventricles called perkinji fibres. S A nde generates the frce f cntractin fr aut rhythmicity f heart, hence called pace maker f the heart. Our heart nrmally beats times in minutes (average f 72 beats per minutes). Cardiac cycle : The cyclic events takes place in each heart beat is called ne cardiac cycle. Lets starts with all the fur chambers f heart are in a relaxed state i.e. in jint diastle. As the tricuspid and bicuspid valves are pen, bld frm the pulmnary veins and vena cava flws int the left and right ventricles respectively thrugh left and right atria. Semilunar valves are clsed at this stage. SAN generates the actin ptential which stimulates cntractin f bth atria, called atrial systle. This increases the bld flw frm atria t their respective ventricles by 30 %. The actin ptential frm SAN passed t AVN and then t perkinji fibres thrugh AV bundles. This initiates ventricular systle. The atria underg relaxatin (diastle). During ventricular systle the intra-ventricular bld pressure increases that lead t clsing f tricuspid and bicuspid valves leads t prductin f first heart sund called lub sund. Further increase in pressure leads t pening f semilunar valves. Oxygenated bld frm the left atrium pumped int systemic arta and dexygenated bld frm the right atrium pumped int the pulmnary arta. Ventricular systle fllwed by ventricular diastle. Intra-ventricular bld pressure decreases leads t clsing f semilunar valves causing secnd heart sund (dub). As the ventricular pressure declines further there is pening f bicuspid and tricuspid valves, bld frm the atria flws int the ventricles freely. The ventricle and atria relaxed simultaneusly called jint diastle. This sequential event in the heart which cyclically repeated called cardiac cycle. The heart beats 72 times per minutes. Each cardiac cycle takes 0.8 sec t cmplete. During a cardiac cycle the ventricles pumped 70 ml bld t the arta called strke vlume. Stke vlume multiplied by heart rate (heart beat per min.) gives the cardiac utput. Cardiac ut put fr human heart is 5000 ml. Electrcardigraph (ECG) : ECG is a graphical representatin f the electrical activity f the heart during a cardiac cycle. Each peak in the ECG is identified with a letter frm P t T that crrespnds t a specific electrical activity f the heart. The P-wave represents the electrical excitatin (r deplarizatin) f the atria. The QRS cmplex represents the deplarizatin f the ventricles. The ventricular cntractin starts shrtly after the Q and marks the beginning f the ventricular systle. T-wave represents the ventricular diastle (replarisatin). DOUBLE CIRCULATION : Pulmnary circulatin: Right ventricle (dexygenated bld) pulmnary artery lungs (xygenatin) pulmnary vein (xygenated bld) left atrium. Systemic circulatin: left ventricle (xygenated bld) systemic arta bdy (dexygenated) vena cava (dexygenated bld) right atrium. Prtal system: the dexygenated bld cllected frm ne rgan by means f a vein (prtal vein) entered int anther rgan befre it is delivered t the systemic circulatin.

6 Hepatic prtal system: the hepatic prtal vein carries dexygenated bld frm the intestine t the liver befre it is delivered t the systemic circulatin by means f hepatic vein. Crnary circulatin: A special bld vessel (crnary vessel) is present in ur bdy exclusively fr the circulatin f bld t and frm the cardiac musculature. REGUALTION OF CARDIAC ACTIVITY : Rhythmicity f human heart is regulated by specialized (ndal tissues), hence the heart is called mygenic. A special neural centre in the medulla blngata can regulate cardiac functin mderately. Neural signal thrugh sympathetic nerve can increase the heart rate and cardiac utput. Neural signal thrugh parasympathetic nerve can decrease the heart rate and cardiac utput. Hrmnes f adrenal medulla (adrenaline) als increase the cardiac utput. DISORDERS OF CIRCULATORY SYSTEM : Hypertensin : Hypertensin is the term fr bld pressure that is higher than nrmal (120/80). 120 mm Hg is the systlic pressure and 80 mm Hg is the diastlic pressure. Sustained bld pressure f 140/90 r higher is said t be hypertensin. Bld pressure is measured by sphygmmanmeter. High bld pressure leads t heart disease and als affects vital rgan like brain and kidney. Crnary Artery Disease (CAD) : Often referred as athersclersis, affects the bld supply t the heart muscles. It is caused by depsitin f calcium, fat, chlesterl and fibrus tissue which makes the lumen f crnary artery narrwer. Angina : It is als knwn as angina pectris. Causes acute chest pain due t inadequate xygen supply t the heart. It ccurs due t blckade t crnary artery. Heart failure : It is the state f the heart when it is nt pumping bld effectively Cardiac arrest: the heart stps beating. Heart attack: heart muscle damaged suddenly by an inadequate bld supply t the heart muscles.