Body Fluids and Circulation PDF

Circulation is the transport of nutrients, oxygen, CO2 and excretory products to the concerned tissues or organs. For circulation, simple organisms (sponges, coelenterates etc) use water from their surroundings. Complex organisms use body fluids (blood & lymph) for circulation. Here, the blood pum...

Circulation is the transport of nutrients, oxygen, CO2 and excretory products to the concerned tissues or organs. For circulation, simple organisms (sponges, coelenterates etc) use water from their surroundings. Complex organisms use body fluids (blood & lymph) for circulation. Here, the blood pumped by the heart passes through large vessels into open spaces or cavities called sinuses. E.g. Arthropods and molluscs. Here, blood pumped by the heart is circulated through blood vessels. It is more advantageous as the flow of fluid can be precisely regulated. E.g. Annelids and chordates. It is seen in fishes. Heart receives impure blood only (venous heart). Deoxygenated blood from heart → oxygenated by gills → supplied to body parts → deoxygenated blood → to heart. It is seen amphibians & reptiles. Left atrium receives oxygenated blood from gills/lungs/skin. Right atrium gets deoxygenated blood from other body parts. However, they get mixed up in the single ventricle. Ventricle pumps out mixed blood. It is seen in birds & mammals. Left atrium receives Oxygenated blood. It passes on to left ventricle. Right atrium receives Deoxygenated blood. It passes on to right ventricle. Ventricles pump it out separately without any mixing up.  Constituents of plasma Functions Solvent. Transports vitamins, hormones, enzymes, Water (90-92%) nutrients etc. Fibrinogen For blood coagulation (clotting) Plasma proteins Globulins Act as antibodies (for defense of the body) (6-8 %) Albumins Osmotic balance & regulation of blood pressure. Glucose, amino acids, lipids, For energy production and growth cholesterol Inorganic: (Na+, K+, Mg2+, Cl-, Regulation of osmosis etc. HCO3- , Ca2+ ) Ca2+ For blood clotting and muscle contraction Gases (CO2, O2, N2 etc) For transport Features of RBC (Erythrocytes) Colour Red (due to haemoglobin) Lifespan 120 days Count 5 - 5.5 millions/mm-3 Formed in Red bone marrow Biconcave in shape. Structure No nucleus, mitochondria etc. Functions CO2 and O2 transport  Features of WBC (Leucocytes) Colour Colourless Lifespan 1-15 days Count 6000-8000 /mm-3 Bone marrow, lymph glands, Formed in spleen Structure Nucleated. Different types Functions Part of immune system Types of WBC % Functions Neutrophils (Heterophils) 60-65% Phagocytosis. Soldier of the body. Granulocytes Resist infections. Eosinophils (Acidphils) 2-3% Cause allergic reactions. Secrete histamine, serotonin, heparin. Basophils (Cyanophils) 0.5-1% Cause inflammatory reactions. Monocytes (Largest WBC) 6-8% Phagocytosis Agranulocytes Lymphocytes B- lymphocytes Immune responses of the body. (Smallest WBC, 20-25% Secrete antibodies. largest nucleus) T- lymphocytes  Features of Platelets (Thrombocytes) Colour Colourless Lifespan 7 days Count 1.5 - 3.5 lakhs/mm-3 Formed in Megakaryocytes in Bone marrow Non-nucleated cell fragments. Structure Release clotting substances. Functions Blood clotting It is a mechanism for haemostasis (prevention of blood loss through injuries). It involves the following events:  Blood groups were discovered by Carl Landsteiner. It includes ABO grouping & Rh Grouping. It is based on presence or absence of 2 surface antigens (chemicals that induce immune response) on RBCs namely A & B. Similarly, plasma contains 2 antibodies (proteins produced in response to antigens) namely anti-A & anti-B. Can receive blood Antigens on Antibodies in Can donate blood Blood group from (Donor’s RBC plasma to group) A A Anti-B A and AB A, O B B Anti-A B and AB B, O AB A, B Nil AB only A, B, AB & O O Nil Anti-A & Anti-B A, B, AB & O O only Antigen A reacts with anti-A. Antigen B reacts with anti-B. Mixing of bloods with interactive antigens & antibodies causes clumping (agglutination) of RBCs. O group persons are called Universal donors as they can donate blood to persons with any blood group. AB group persons are called Universal recipients because they can accept blood from all groups.  Rhesus (Rh) factor is an antigen found on RBC. Rh+ve means the presence of Rh factor and Rh-ve means absence of Rh factor. Nearly 80% of humans are Rh+ve. It is an Rh incompatibility between the Rh-ve blood of a pregnant mother and Rh+ve blood of the foetus. Rh antigens do not get mixed with maternal blood in first pregnancy because placenta separates the two bloods. But at the time of first delivery, there is a possibility of exposure of the maternal blood to small amounts of the Rh+ve blood from the foetus. This induces the formation of Rh antibodies in maternal blood. In case of her subsequent pregnancies, Rh antibodies from mother leak into the foetal blood (Rh+ve) and destroy the foetal RBCs. This is fatal to foetus or cause severe anaemia and jaundice to the baby. This condition is called Erythroblastosis foetalis. Erythroblastosis foetalis can be avoided by administering anti-Rh antibodies to the mother immediately after the delivery of first child. They carry blood from heart to other tissues. They contain oxygenated blood (except pulmonary artery). Their smaller branches are called arterioles. Arteries have 3 layers: Tunica intima: Squamous endothelium. Inner layer. Tunica media: Smooth muscles & elastic fibres. Middle layer. Tunica externa: Fibrous connective tissue with collagen fibres. Outer layer. They carry blood towards heart. They contain deoxygenated blood (except pulmonary vein) Their smaller branches are called venules. Veins are also 3-layered but tunica media is comparatively thin. In tissues, arterioles divide into thin walled and single layered vessels. They are called capillaries. They unite into venules. Heart is a mesodermally derived organ located in mediastinum. It is protected by double-layered pericardium. The pericardial space (between pericardial membranes) is filled with pericardial fluid. It reduces the friction between the heart walls, and surrounding tissues. Heart is 4 chambered- 2 upper atria (auricles) & 2 lower ventricles. The walls (cardiac muscles) of the ventricles are much thicker than that of the atria. Atria are separated by inter-atrial septum. Ventricles are separated by inter-ventricular septum. In b/w atrium and ventricle there is a thick fibrous atrio-ventricular septum with an opening. A tricuspid valve (3 muscular flaps or cusps) guards the opening between right atrium and right ventricle. A bicuspid (mitral) valve guards the opening between left atrium and left ventricle.  These valves allow the flow of blood only in one direction, i.e. from atria to ventricles. The openings of right & left ventricles into pulmonary artery and aorta respectively are provided with the semi-lunar valves. They prevent backwards flow of blood. Human heart is myogenic, i.e. normal activities of heart are auto regulated by nodal tissues (a specialized cardiac musculature present in heart wall). It consists of Sino-atrial node (SAN) in the right upper corner of the right atrium. Atrio-ventricular node (AVN) in the lower left corner of the right atrium close to the atrio- ventricular septum. From the AVN, a bundle of fibrous atrio- ventricular bundle (AV bundle) passes through atrio-ventricular septa and divides into a right & left branches. Each branch passes through the ventricular walls of its side. In the ventricular wall, it breaks up into minute fibres (Purkinje fibres). These fibres along with the bundles are known as bundle of His. Nodal tissues generate action potential without any external stimuli, i.e. it is autoexcitable. SAN initiates and maintains contraction of heart by generating action potentials (70-75/min). So it is called the pacemaker. Firstly, all chambers of heart are in relaxed state (joint diastole). When the tricuspid & bicuspid valves open, blood from pulmonary vein and vena cava flows into left & right ventricles respectively through left & right atria. Semilunar valves are closed at this stage. The SAN generates an action potential. It stimulates both the atria to undergo contraction (atrial systole). This increases the flow of blood into the ventricles by about 30%. Action potential is conducted to ventricular side by AVN & AV bundle from where bundle of His transmits it through the ventricular musculature. It causes contraction of ventricles (ventricular systole). During this, the atria undergo diastole. Ventricular systole increases the ventricular pressure. It causes the following events: Closure of tricuspid and bicuspid valves due to attempted backflow of blood into the atria. Semilunar valves open. So deoxygenated blood enters the pulmonary artery from right ventricle and oxygenated blood enters the aorta from left ventricle. The ventricles now relax (ventricular diastole) and the ventricular pressure falls. It causes the following events: Closure of the semilunar valves. It prevents the backflow of blood into the ventricles. Tricuspid & bicuspid valves are opened by the pressure in the atria. Ventricles & atria again undergo joint diastole and the above processes are repeated. This is called cardiac cycle. A cardiac cycle= atrial systole + ventricular systole + diastole A cardiac cycle is completed in 0.8 seconds. One heartbeat = a cardiac cycle. So number of normal heartbeat: 70-75 times/min (average: 72/min). Stroke volume: Volume of blood pumped out by each ventricle during a cardiac cycle. It is about 70 ml. Cardiac output: Volume of blood pumped out by each ventricle per minute, i.e. stroke volume x heart rate (70 x 72). It is about 5000 ml (5 litres). Cardiac output of an athlete is very high. During each cardiac cycle, 2 prominent sounds are produced. First sound (lub) is due to the closure of tricuspid & bicuspid valves. Second sound (dub) is due to the closure of the semilunar valves. One heartbeat = a lub + a dub. Human heart is myogenic because normal activities of heart are auto regulated by nodal tissues. Medulla oblongata regulates cardiac activity through ANS. Sympathetic nerves of ANS increase the rate of heartbeat, the strength of ventricular contraction and cardiac output. Parasympathetic nerves of ANS decrease the heart beat, conduction of action potential and the cardiac output. Adrenal medullary hormones increase the cardiac output.  In man, blood flows through the heart twice for completing its circuit. This is called double circulation. It includes, Pulmonary circulation Systemic circulation It is the circulation b/w lungs and heart. Deoxygenated blood pumped into the pulmonary artery is passed on to lungs from where oxygenated blood is carried by pulmonary veins into the left atrium. It is the circulation b/w heart & various body parts. Oxygenated blood is passed through aorta, arteries, arterioles & capillaries and is reached the tissues. Deoxygenated blood collected from tissues by venules, veins & vena cava is carried to the right atrium. Systemic circulation provides nutrients, O2 and other substances to the tissues and takes CO2 and other harmful substances away for elimination.  It is a system which includes the hepatic portal vein that carries blood from intestine to the liver before it is delivered to the systemic circulation. It is a system of coronary vessels that circulate blood to and from the cardiac musculature.  It includes Lymph, Lymph vessels & Lymph nodes. As the blood passes through the capillaries in tissues, some water and soluble substances are filtered out from plasma to the intercellular spaces, to form tissue (interstitial) fluid. It has the same mineral distribution as that in plasma. Exchange of nutrients, gases, etc between the blood & cells occur through this fluid. Some tissue fluid enters lymphatic system (a system of lymph vessels and lymph glands) and the tissue fluid in them is called lymph. Lymph drains back to the major veins. It is the middleman between blood & tissues. It carries plasma proteins synthesized in liver to the blood. Transports digested fats (through lacteals in the intestinal villi), fat soluble vitamins, hormones etc. Filtration of bacteria and foreign particles. Lymph nodes produce WBC (lymphocytes) & antibodies. It helps in the defensive mechanism of body. It is an instrument used to obtain electrocardiogram (it is a graphical representation of the electrical activity of the heart during a cardiac cycle). To get an ECG, a patient is connected to the machine with 3 electrical leads (one to each wrist and to left ankle) that monitor heart activity. For a detailed evaluation of heart’s function, multiple leads are attached to the chest region. An ECG consists of the following waves: P-wave: Represents the excitation (depolarization) of atria which causes atrial systole. QRS-complex: Represents depolarization of ventricles (Ventricular systole). T-wave: Represents the repolarisation of ventricles. Deviation in the ECG indicates the abnormality or disease. So ECG has great clinical significance. Here, the blood pressure is higher than normal systolic (pumping) pressure (120 mm Hg) and normal diastolic (resting) pressure (80 mm Hg), i.e. above 120/80 mm Hg. If the BP is 140/90 or above, it is hypertension. It leads to heart diseases and affects vital organs (brain, kidney etc). It is the deposition of Ca, fat, cholesterol and fibrous tissue in coronary arteries. It makes the lumen of arteries narrower and thereby affect the blood supply. An acute chest pain due to O2 deficiency to heart muscles. It occurs due to improper blood flow. It is common among middle-aged and elderly. It is the condition in which heart is not pumping blood enough to meet the needs of the body. Congestion of the lungs is the main symptom. Heart failure is not same as cardiac arrest (heart stops beating) or a heart attack (sudden damage of heart muscle due to inadequate blood supply).