Body Fluids and Circulation | Complete NEET Hinglish Notes

1. Transportation of Substances in Human Body – Blood and Lymph Explained

Har living organisms me, ye zaruri hai ki har cell ko important substances jaise oxygen (O₂), nutrients, aur dusre essentials supply kiye jayein. Saath hi, waste products ya toxic substances jo cell functions ke dauran bante hain, unko regularly remove karna bhi zaruri hai taaki tissues ki health maintain rahe. Isliye ek efficient transport system zaruri hai jo useful materials ko cells tak le jaye aur wastes ko cells se remove kare.

Different types ke animals ne internal transport ke liye alag-alag tareeke develop kiye hain. Simple animals jaise sponges aur coelenterates me, surrounding environment ka water unke body cavities se flow karta hai, jo cells ke saath direct substance exchange allow karta hai. Lekin complex organisms, including humans, special body fluids ka use karte hain ye function perform karne ke liye.

Sabse important body fluid jo humans aur higher organisms me transportation ke liye use hota hai, wo hai blood. Ye central role play karta hai oxygen, nutrients, hormones, aur waste materials ko body me carry karne me. Blood ke saath, ek aur important fluid lymph bhi help karta hai certain substances ko transport karne me, especially fats aur immune cells.

Is chapter me hum blood aur lymph ke composition, functions, aur blood circulation ka mechanism detail me explore karenge 🥰Learn Sufficient Notes🥰. In concepts ko samajhna key hai ye seekhne ke liye ki kaise humara body healthy aur functional rehta hai by constantly essential substances ko unke required places par move karke.

2. What is Blood ? – Composition and Function of Human Blood

Blood human body me ek vital connective tissue hai jo life maintain karne me key role play karta hai. Ye do main parts se bana hai: ek fluid matrix jise plasma kehte hain, aur ek variety of formed elements jaise red blood cells (RBCs), white blood cells (WBCs), aur platelets. Ye special fluid responsible hai oxygen, nutrients, hormones, aur waste products ko body ke different parts me transport karne ke liye. Iske complex composition aur circulation me essential role ki wajah se, blood ko aksar lifeline of the body kaha jata hai.

2.1 Plasma in Blood – Composition and Functions of Blood Plasma

Plasma ek straw-colored, slightly thick (viscous) fluid hai jo human blood ka lagbhag 55% banata hai. Ye mainly 90–92% water se bana hota hai, jo various substances ko dissolve aur carry karne me help karta hai. Lagbhag 6–8% plasma proteins se bana hota hai, jisme teen major types hain – fibrinogen, globulins, aur albumins. Har ek ka specific aur vital function hai: fibrinogen blood clotting ke liye essential hai, globulins body ki immune defense support karte hain, aur albumins blood me osmotic balance maintain karne me help karte hain.

Proteins ke alawa, plasma me chhote lekin important minerals bhi hote hain jaise sodium (Na⁺), calcium (Ca²⁺), magnesium (Mg²⁺), bicarbonate (HCO₃⁻), aur chloride ions (Cl⁻). Saath hi, glucose, amino acids, aur lipids bhi present hote hain, kyunki ye continuously body ke different parts me transport hote rehte hain. Plasma inactive clotting factors bhi carry karta hai, jo blood clotting ke waqt active ho jate hain. Jab ye clotting factors plasma se remove kar diye jate hain, to remaining clear fluid ko serum kehte hain. Overall, plasma ek transport medium ka kaam karta hai jo nutrients, hormones, waste, aur aur substances ko circulatory system me le jata hai.

2.2 Formed Elements in Blood – Detailed Explanation

1. Red Blood Cells (RBCs) – Oxygen Carriers of the Body

Red blood cells (RBCs), jise erythrocytes bhi kehte hain, human blood me sabse abundant cells hote hain aur ye mainly oxygen ko body ke sabhi tissues tak le jane ke liye responsible hote hain. Healthy adult male me RBCs ka count lagbhag 5 se 5.5 million per mm³ of blood hota hai. Ye cells red bone marrow me produce hote hain aur biconcave disc shape ke hote hain, jo gas exchange ke liye maximum surface area provide karta hai. Bahut se cells ke unlike, mammalian RBCs me nucleus nahi hota, jo haemoglobin ke liye zyada space provide karta hai—ye ek red-colored, iron-rich protein hai jo oxygen aur carbon dioxide se bind karta hai. Ek person me normal haemoglobin level lagbhag 12 se 16 grams per 100 ml of blood hota hai, jo respiratory gases ko transport karne me crucial role play karta hai. RBC ka average life span lagbhag 120 days hota hai, jiske baad ye spleen me break down ho jate hain, jo aksar graveyard of RBCs ke naam se jana jata hai.

2. White Blood Cells (WBCs) – Body’s Defense Warriors

White blood cells (WBCs), ya leucocytes, colorless aur nucleated cells hote hain jo immune system ka ek important part banate hain. RBCs ke unlike, ye kam number me hote hain, typically 6,000 se 8,000 per mm³ of blood, aur inka life span bhi chhota hota hai. Inka main function body ko infections aur foreign substances se defend karna hai. WBCs do groups me classified hote hain: granulocytes (jinme visible granules hote hain) aur agranulocytes (jinme nahi hote). Granulocytes me neutrophils, eosinophils, aur basophils shamil hain, jabki agranulocytes me monocytes aur lymphocytes hote hain. Inme se neutrophils sabse abundant hote hain (60–65% of total WBCs) aur basophils sabse rare hote hain (0.5–1%). Neutrophils aur monocytes phagocytic cells ke roop me kaam karte hain, matlab ye pathogens ko engulf aur destroy karte hain. Basophils chemicals release karte hain jaise histamine, serotonin, aur heparin, jo inflammatory reactions me help karte hain. Eosinophils (2–3%) parasitic infections se fight karte hain aur allergic responses me active hote hain. Lymphocytes (20–25%) B aur T cells ke roop me exist karte hain, dono hi specific immunity build karne me help karte hain against various diseases.

3. Platelets – Blood Clotting Agents

Platelets, ya thrombocytes, chhote cell fragments hote hain jo megakaryocytes se originate hote hain, ye special bade cells hote hain jo bone marrow me paye jate hain. Ek normal blood sample me lagbhag 1,50,000 se 3,50,000 platelets per mm³ hote hain. Halanki ye full cells nahi hote, platelets body me life-saving role play karte hain by clotting process me participate karke. Jab injury ya bleeding hoti hai, platelets clotting substances release karte hain jo wound ko seal karte hain aur excessive blood loss ko prevent karte hain. Agar platelet count kam ho jaye, to ye clotting disorders cause kar sakta hai, jisse minor injuries se bhi uncontrolled bleeding ho sakta hai. Yehi wajah hai ki platelets body ke internal balance ko maintain karne me ek critical component hote hain.

3. Blood Groups – Understanding ABO and Rh Blood Grouping in Humans

Halanki human blood sab me ek jaisa lagta hai, lekin molecular level par ye alag hota hai, isiliye blood grouping zaroori hai. Scientists ne blood ko alag-alag types me classify kiya hai based on specific antigens aur antibodies jo red blood cells (RBCs) ke surface par hote hain. Do sabse widely recognized systems jo globally use hote hain, wo hain ABO blood group system aur Rh factor grouping. Ye classifications blood transfusions, organ transplants, aur pregnancy care me bahut important hain, kyunki blood group mismatch se serious complications ho sakte hain. Sahi blood group identify karke, doctors safe aur compatible transfusions ensure karte hain, jisse blood grouping ek life-saving diagnostic tool ban jata hai medicine me.

3.1 Rh Blood Grouping in Humans – Importance, Pregnancy Complications, and Prevention

ABO blood group system ke alawa, ek aur important antigen hai jise Rh factor kehte hain, jo apne pehle discovery ke time Rhesus monkey me paya gaya tha. Ye Rh antigen red blood cells (RBCs) ke surface par lagbhag 80% human population me hota hai, aur aise individuals ko Rh-positive (Rh⁺) kaha jata hai. Jo log is antigen se free hote hain, unhe Rh-negative (Rh⁻) kehte hain. Agar koi Rh⁻ person Rh⁺ blood receive karta hai, to unka immune system Rh antigen ke khilaf antibodies banata hai, jo dangerous transfusion reactions cause kar sakta hai. Isiliye blood transfusions me Rh groups ka match karna bahut zaroori hai.

Ek serious complication Rh incompatibility ki wajah se pregnancy me bhi ho sakta hai, jab ek Rh-negative mother ka fetus Rh-positive ho. Pehli pregnancy me usually koi problem nahi hoti kyunki placenta mother aur baby ka blood alag rakhta hai. Lekin childbirth ke time, thodi si Rh-positive fetal blood mother ke circulation me aa sakti hai, jisse mother ka immune system anti-Rh antibodies banana start kar deta hai. Dusri ya uske baad ki pregnancies me, ye antibodies placenta cross karke fetal red blood cells ko attack kar sakti hain, jisse dangerous condition erythroblastosis foetalis ho sakta hai. Ye severe anemia, jaundice, ya untreated case me fetus ki death tak cause kar sakta hai. Thankfully, is condition ko prevent kiya ja sakta hai by injecting anti-Rh antibodies (Rh immunoglobulin) Rh-negative mother ko pehli delivery ke turant baad, jo Rh-positive cells ko neutral kar deti hai aur antibodies formation rok deti hai.

3.2 ABO Grouping – Concept, Antigens, Antibodies, and Compatibility in Blood Transfusion

ABO blood group system ka base hai do specific surface antigens par jo red blood cells (RBCs) par hote hain – antigen A aur antigen B. Ye antigens body me immune response trigger kar sakte hain. Iske corresponding, plasma me naturally specific antibodies hoti hain – anti-A aur anti-B, jo foreign antigens ke khilaf react karti hain.

Blood groups is combination ke hisaab se 4 major types me divide hote hain: A, B, AB, O.

Blood group A: RBCs par antigen A, plasma me anti-B antibody.
Blood group B: RBCs par antigen B, plasma me anti-A antibody.
Blood group AB: RBCs par antigens A & B, plasma me no antibodies → universal plasma recipient.
Blood group O: RBCs par no antigens, plasma me anti-A & anti-B antibodies → universal RBC donor.

Blood transfusion me matching bahut important hai. Agar incompatible blood transfuse hota hai, to recipient ke antibodies donor ke RBC antigens se react karke agglutination (clumping) aur RBC destruction cause karte hain. Isse serious complications ho sakte hain, jaise kidney failure aur extreme cases me death. Isiliye transfusion se pehle careful blood group matching zaruri hai.

4. Blood Clotting Mechanism

Jab koi vyakti cut ya injury experience karta hai, to bleeding indefinite nahi chalti. Ye stoppage of blood flow ek biological process ki wajah se hota hai jise blood coagulation ya clotting kehte hain. Ye body ka ek protective mechanism hai jo injury ya trauma ke baad excessive blood loss ko rokta hai. Samay ke saath, wound site par ek dark reddish-brown scum ya clot banta hai. Is clot ko scientifically coagulum kehte hain. Ye mainly thread-like protein structures jise fibrins kehte hain, ka network hota hai, jisme dead aur damaged blood cells trap ho jaate hain.
Fibrins fibrinogen se produce hote hain, jo ek inactive protein hai aur normally plasma me circulate karta hai. Jo enzyme fibrinogen ko fibrin me convert karta hai, use thrombin kehte hain. Lekin, thrombin khud bhi initially active form me present nahi hota. Ye ek aur inactive plasma protein se derive hota hai jise prothrombin kehte hain. Prothrombin ko thrombin me convert karne ke liye ek special enzyme complex ki zarurat hoti hai jise thrombokinase (ya prothrombinase) kehte hain. Ye enzyme complex directly available nahi hota, balki ek cascade of enzymatic reactions ke through banta hai, jisme har step me clotting factors involve hote hain jo normally blood plasma me inactive form me present hote hain.
Jab injury hoti hai, to ye platelets ko activate karta hai, jo chhote blood components hote hain aur clotting start karne ke liye responsible hote hain. Ye activated platelets various clotting factors release karte hain, jo thrombokinase ke formation ko kickstart karte hain. Saath hi, trauma ke site par injured tissue cells bhi chemical substances release karte hain jo clotting mechanism ko trigger kar sakte hain. Is poore clotting cascade me sabse critical component calcium ions (Ca²⁺) hote hain, jo in biochemical conversions aur interactions ko enable karne me essential aur irreplaceable role play karte hain. Calcium ke bina, clotting process efficiently proceed nahi kar paata.

5. Physiology of Tissue Fluid (Lymph)

Lymph, jise tissue fluid bhi kehte hain, human circulatory aur immune systems ka ek vital component hai. Jab blood body ke various tissues me thin-walled capillaries se flow karta hai, to water ka ek portion aur kai chhote, water-soluble substances intercellular spaces me filter ho jaate hain. Ye extravascular fluid interstitial fluid ya tissue fluid ke naam se jaana jata hai. Jabki iska mineral composition nearly plasma ke barabar hota hai, isme bade plasma proteins aur zyada tar formed elements jaise red aur white blood cells nahi hote, jo blood vessels ke andar hi rehte hain. Ye tissue fluid ek crucial intermediary role play karta hai, kyunki blood aur tissue cells ke beech essential substances jaise oxygen, carbon dioxide, nutrients, aur metabolic waste ka exchange isi ke through hota hai. Human body me specialized network of lymphatic vessels hota hai jo is interstitial fluid ko collect karke gradually bloodstream me major veins ke through return karte hain, is tarah fluid balance maintain hota hai.
Jab ye fluid lymphatic vessels me aata hai, to ise lymph kehte hain. Lymph ek clear, pale fluid hai jo ek unique population of white blood cells contain karta hai jise lymphocytes kehte hain. Ye lymphocytes body ke immune responses me pivotal hote hain, aur pathogens jaise bacteria aur viruses ko identify aur neutralize karte hain. Apni immune function ke alawa, lymph nutrients aur hormones ka transport medium bhi kaam karta hai, aur inhe body me distribute karne me help karta hai. Additionally, lymphatic system fat absorption me bhi critical role play karta hai. Specialized lymphatic capillaries jise lacteals kehte hain, small intestine ke intestinal villi me located hote hain, ye dietary fats aur fat-soluble vitamins ko absorb karte hain, jo phir lymph ke through bloodstream me transport hote hain. Is tarah, lymphatic system sirf fluid homeostasis maintain nahi karta balki human body me nutrition aur defense mechanisms me bhi significantly contribute karta hai.

6. Pathways of Circulation: Double and Single

Animals me paye jane wale circulatory systems do main types ke hote hain: open circulatory system aur closed circulatory system.

Ek open circulatory system me, blood heart dwara large vessels me pump hota hai jo open spaces ya body cavities me empty hote hain jise sinuses kehte hain. Ye type ka system arthropods aur molluscs me paya jata hai.

Iske contrast me, closed circulatory system annelids aur chordates me dekha jata hai, jahan blood ek closed network of blood vessels ke through flow karta hai. Ye system zyada advantageous hai kyunki blood ka flow precisely regulate aur specific tissues tak direct kiya ja sakta hai.

Types of Heart in Vertebrates

All vertebrates possess a muscular, chambered heart, but the number and arrangement of chambers vary:

Fishes have a 2-chambered heart, consisting of one atrium and one ventricle.
Amphibians and most reptiles (except crocodiles) have a 3-chambered heart with two atria and one ventricle.
Crocodiles, birds, and mammals possess a 4-chambered heart with two atria and two ventricles, which ensures complete separation of oxygenated and deoxygenated blood.

Circulatory Patterns

Single Circulation:
Fishes me, heart deoxygenated blood ko gills tak pump karta hai oxygenation ke liye. Oxygenated blood phir body me distribute hota hai, aur body se deoxygenated blood wapas heart me return hota hai. Ye pattern sirf ek cycle involve karta hai heart ke through, isliye ise single circulation kehte hain.
Incomplete Double Circulation:
Amphibians aur reptiles me, left atrium oxygenated blood receive karta hai lungs, skin, ya gills se, jabki right atrium deoxygenated blood receive karta hai body se. Dono types ke blood single ventricle me mix ho jaate hain, jo phir mixed blood ko pump karta hai. Isse incomplete double circulation kehte hain kyunki partial mixing hoti hai.
Double Circulation:
Birds aur mammals me, left atrium oxygenated blood receive karta hai, aur right atrium deoxygenated blood receive karta hai. Ye blood phir apne respective ventricles me pump hota hai, aur wahan se body aur lungs me respectively bheja jata hai. Yahan oxygenated aur deoxygenated blood ka koi mixing nahi hota, isliye ise true double circulation kehte hain.

6.1 Cycle of Cardiac Events

Cardiac cycle ka matlab hai wo cyclical sequence of events jo human heart me har heartbeat ke dauran hoti hai, taaki blood circulation efficiently poore body me ho sake. Ye cycle ek phase se start hoti hai jisme heart ke sabhi four chambers—do atria aur do ventricles—relaxed state me hote hain, is phase ko joint diastole kehte hain. Is stage me tricuspid aur bicuspid (mitral) valves open rehte hain, jisse vena cava se blood right atrium me aur pulmonary veins se blood left atrium me flow karta hai. Wahan se blood directly right aur left ventricles me pass hota hai, respectively. Saath hi, semilunar valves—jo pulmonary artery aur aorta ko guard karte hain—closed rehte hain, jisse blood ka backflow heart me nahi hota.
Ye process tab start hoti hai jab sino-atrial node (SAN), jo heart ka natural pacemaker hai, action potential generate karta hai. Ye electrical impulse dono atria ko simultaneously contract karne ke liye stimulate karta hai—iske phase ko atrial systole kehte hain—jo blood flow ko ventricles me lagbhag 30% tak badha deta hai. Iske baad, impulse atrioventricular node (AVN) tak conduct hota hai, fir AV bundle (jise bundle of His bhi kehte hain) ke through signal Purkinje fibers me transmit hota hai, jo ventricular musculature ko trigger karta hai ventricular systole ke liye. Jab ventricles contract karte hain, to atria relax karte hain—iske phase ko atrial diastole kehte hain.
Ventricles ke contraction se intraventricular pressure increase hoti hai, jisse tricuspid aur bicuspid valves close ho jaate hain, aur is tarah blood ka atria me backflow prevent hota hai. Jaise hi pressure aur badh jati hai, ye semilunar valves ko open karne ke liye force karta hai, jisse blood right ventricle se pulmonary artery me aur left ventricle se aorta me flow karta hai, is tarah blood ko systemic aur pulmonary circulation me push kiya jata hai.
Iske baad, ventricles diastole me enter karte hain, relax hote hain aur ventricular pressure reduce hoti hai, jisse semilunar valves close ho jaate hain aur arteries se blood ka backflow prevent hota hai. Jab ventricular pressure atria ke pressure se kam ho jati hai, to tricuspid aur bicuspid valves dobara open ho jaate hain, aur blood phir se atria se ventricles me flow karta hai. Isse heart wapas initial joint diastole me aa jata hai, aur cycle next SAN impulse ke saath repeat hone ke liye ready hota hai.
Har complete cardiac cycle me dono atria aur ventricles ki systole aur diastole shamil hoti hai, aur ye cycle ek normal adult me lagbhag 72 times per minute repeat hoti hai, matlab har cycle 0.8 seconds tak chalti hai. Har cycle ke dauran, har ventricle lagbhag 70 mL blood pump karta hai, jise stroke volume kehte hain. Jab ise heart rate se multiply kiya jata hai, to ye cardiac output deta hai. Isliye, cardiac output define kiya jata hai as volume of blood pumped by each ventricle per minute, jo typically healthy adult me 5000 mL ya 5 litres hota hai. Body stroke volume aur heart rate ko regulate karke cardiac output adjust kar sakti hai, isiliye trained athletes ka cardiac output non-athletes ke comparison me significantly higher hota hai.
Additionally, har cardiac cycle ke dauran do distinct heart sounds produce hote hain aur ye clearly stethoscope se suna ja sakta hai. Pehla heart sound (commonly “lub”) atrioventricular valves (tricuspid aur bicuspid) ke closure se produce hota hai, jabki doosra heart sound (“dub”) semilunar valves ke close hone par generate hota hai. Ye sounds clinically significant hote hain aur heart ke functional condition ko assess karne ke liye use kiye jaate hain.

6.2 Blood Circulation Mechanism in Humans

Human circulatory system, jise blood vascular system bhi kehte hain, ek highly specialized internal transport mechanism hai jo three key components se bana hai: ek muscular chambered heart, branching blood vessels ka closed network, aur blood, jo circulating fluid hai aur nutrients, gases, hormones, aur waste products ko poore body me transport karta hai. Heart, jo mesodermally derived hai, thoracic cavity me located hai, do lungs ke beech aur thoda left ki taraf tilted. Ye lagbhag ek clenched fist ke size ka hota hai aur double-walled membranous sac jise pericardium kehte hain, dwara safeguard hota hai, jo pericardial fluid enclose karta hai taaki heartbeats ke dauran friction reduce ho.
Human heart me four chambers hote hain—do chhote upper chambers jise atria kehte hain aur do bade lower chambers jise ventricles kehte hain. Right aur left atria ek thin muscular wall jise inter-atrial septum kehte hain, se separate hote hain, jabki right aur left ventricles ek thick muscular wall jise inter-ventricular septum kehte hain, se divided hote hain. Har atrium aur uske corresponding ventricle ko ek fibrous tissue jise atrioventricular septum kehte hain, se separate kiya jata hai, jo openings contain karta hai jo same side ke chambers ko connect karte hain. Ye openings valves se guarded hote hain taaki blood ka flow unidirectional ho. Right atrium aur right ventricle tricuspid valve ke through connected hote hain, jisme three muscular flaps ya cusps hote hain, jabki left atrium aur left ventricle bicuspid valve (ya mitral valve) ke through connected hote hain, jisme do flaps hote hain.
Right aur left ventricles ke exit points—respectively pulmonary artery aur aorta me—semilunar valves se secured hote hain. Heart ke sabhi valves blood ka flow sirf ek direction me allow karte hain, effectively contractions aur relaxations ke dauran koi backflow prevent karte hain. Heart ki walls puri tarah cardiac muscle se bani hoti hain, jisme ventricular walls atria ke walls se kaafi thicker aur stronger hote hain, kyunki blood ko body aur lungs me pump karne ke liye zyada force ki zarurat hoti hai.
Heart muscle me embedded ek specialized tissue hota hai jise nodal tissue kehte hain, jo heart ke rhythmic contractions ko regulate karne me critical role play karta hai. Nodal system ka ek important part hai sino-atrial node (SAN), jo right atrium ke upper right corner me located hai. Ek aur vital component hai atrioventricular node (AVN), jo right atrium ke lower left corner me, atrioventricular septum ke paas situated hai. AVN se extend hota hai ek bundle of specialized fibers jise atrioventricular bundle (AV bundle) kehte hain, jo atrioventricular septum se pass karte hue quickly right aur left bundle branches me divide hota hai. Ye further fine fibers jise Purkinje fibers kehte hain, me spread hota hai, jo ventricular muscle me distribute hote hain aur coordinated contractions enable karte hain.
Nodal musculature ka ek remarkable feature hai iska auto-excitability—ye external stimuli ke bina action potentials generate kar sakta hai. Nodal system ke sabhi parts me, SAN ka impulse generation rate sabse highest hai, jo 70–75 action potentials per minute produce karta hai. Ye inherent rhythmicity SAN ko heart ka natural pacemaker banati hai. Iske result me, healthy adult me normal resting heart rate lagbhag 72 beats per minute hoti hai, halanki ye person to person thodi vary kar sakti hai.

6.3 Electrocardiographic Tracing of Heartbeats

Electrocardiogram (ECG) ek diagnostic tool hai jo complete cardiac cycle ke dauran heart ki electrical activity ko record karta hai. Ye commonly hospitals me heart ke functioning ko real-time me monitor karne ke liye use hota hai.

What is an ECG ?

ECG ek graphical recording hai jo dikhata hai ki har heartbeat ke dauran heart ke electrical signals kaise change hote hain. Ye signals heart muscles ke contraction aur relaxation ko control karte hain, jisse blood ka proper pumping ensure hota hai.

How is ECG Taken ?

To record a standard ECG:

Patient ko ek machine se connect kiya jata hai using three electrical leads:
- Ek lead har wrist se attach kiya jata hai.
- Ek lead left ankle se attach kiya jata hai.
Ye leads skin par hone wale tiny electrical changes detect karte hain, jo heart muscle ki electrical activity se arise hote hain.
Clinical settings me, zyada detailed monitoring ke liye multiple leads aksar chest area ke around place kiye jaate hain.

Waves of ECG and Their Meaning

Har ECG tracing me kai waves hote hain, jo cardiac cycle me ek specific event ko represent karte hain:

Wave	Description
P-wave	Ye atrial depolarization (electrical activation) ko indicate karta hai, jisse atria contract karte hain.
QRS Complex	Ye ventricular depolarization ko represent karta hai, jo ventricular contraction ko initiate karta hai (systole Q ke just baad start hoti hai).
T-wave	Ye ventricular repolarization (resting state me return) ko dikhata hai, jo systole ke end ko mark karta hai.

Heart Rate from ECG

Ek specific time interval me QRS complexes ki counting karke, easily heart rate calculate ki ja sakti hai.

Clinical Significance

ECG waves ka shape aur size generally healthy individuals me same lead configuration ke liye similar hota hai.
Waveform me koi bhi deviation heart diseases ya abnormalities indicate kar sakta hai, jaise:
- Arrhythmias
- Myocardial infarction (heart attack)
- Conduction disorders

Isliye, ECG ek non-invasive, quick, aur valuable diagnostic tool hai, jo widely heart health assess karne ke liye use hota hai.

7. Blood Circulation Through Two Pathways

1. Fixed Path of Blood Flow through Blood Vessels
Human circulatory system me, blood ek definite aur fixed pathway ke along move karta hai specific blood vessels—arteries aur veins ke through. Har ek blood vessel three distinct layers se bana hota hai. Sabse inner layer ko tunica intima kehte hain, jo squamous endothelium se lined hoti hai. Agli layer middle layer hai, jise tunica media kehte hain, jo smooth muscle fibers aur elastic tissues se bani hoti hai. Aur finally, outermost layer, jise tunica externa kehte hain, fibrous connective tissue se bani hoti hai jo collagen fibers me rich hoti hai. Dhyan dene wali baat hai ki tunica media veins me arteries ke comparison me thinner hoti hai, jo unke respective functions me key structural difference provide karti hai. Ye structural organization blood ka efficient transport aur regulation poore body me allow karti hai.

2. Pulmonary Circulation – Right Ventricle to Lungs
Jab blood right ventricle se pump hota hai, to ye pulmonary artery me enter karta hai, jo unique hai kyunki ye deoxygenated blood carry karta hai. Ye blood lungs tak transport hota hai, jahan ye oxygenation undergo karta hai. Oxygen-rich hone ke baad, blood left atrium me pulmonary veins ke through return hota hai. Ye poora loop of blood movement—right ventricle se lungs tak aur wapas left atrium me—pulmonary circulation ke naam se jana jata hai. Ye gas exchange me crucial role play karta hai, ensuring ki blood oxygen receive kare aur carbon dioxide expel kare, uske baad ye main circulatory system me wapas enter hota hai.

3. Systemic Circulation – Left Ventricle to Body Tissues
Jab oxygenated blood left ventricle me enter karta hai, to ye aorta, jo body ka largest artery hai, me pump hota hai. Aorta se, oxygenated blood arteries, arterioles, aur capillaries ke network ke through body tissues tak travel karta hai. Yahan oxygen aur nutrients deliver kiye jaate hain, aur carbon dioxide aur waste products tissues se absorb hote hain. Ye ab deoxygenated blood venules ke through collect hota hai, jo merge hoke veins banate hain aur eventually vena cava me drain karte hain—jo main vein hai jo blood right atrium me return karta hai. Ye circulation route systemic circulation ke naam se jana jata hai, aur ye tissues ko oxygen, nutrients provide karne aur metabolic wastes remove karne ke liye essential hai.

4. Hepatic Portal System – Special Digestive-Liver Connection
Ek interesting aur unique vascular arrangement jise hepatic portal system kehte hain, digestive tract aur liver ke beech exist karta hai. Is system me, hepatic portal vein intestine se nutrient-rich blood collect karta hai aur ise directly liver tak transport karta hai. Systemic circulation me enter karne se pehle, ye blood liver dwara process hota hai—harmful substances ko detoxify karna aur nutrients ko regulate karna. Ye mechanism metabolic balance maintain karne aur food ke through absorb hone wale toxins se body ko protect karne ke liye crucial hai.

5. Coronary Circulation – Dedicated Pathway for the Heart
Heart, being ek muscular organ jo continuously blood pump karta hai, apne liye oxygen aur nutrients ka supply require karta hai. Is purpose ke liye, body me ek specialized coronary circulation system hota hai. Ye system coronary arteries aur veins se bana hai, jo blood ko cardiac muscles (myocardium) tak circulate karte hain aur wapas le jate hain. Is dedicated vascular network ke through, heart muscles ko constant aur uninterrupted supply of oxygenated blood milti hai, jo heart ke efficient contraction aur functioning ko ensure karti hai.

8. Heart Activity Regulation Mechanism

Human heart ka functioning primarily self-regulated hota hai apne specialized muscle tissue ke dwara, isiliye ise myogenic nature ka kehte hain. Ye intrinsic regulation nodal tissues jaise sinoatrial (SA) node aur atrioventricular (AV) node) ke through control hoti hai, jo heart ko external commands ke bina apne aap beat karne enable karti hai.

Lekin, heart ka rhythm aur efficiency externally bhi modulate kiya ja sakta hai autonomic nervous system (ANS) ke through. Brain ke medulla oblongata me ek specific neural center cardiac activity ko monitor aur modify karne me crucial role play karta hai. Jab sympathetic nerves—jo autonomic nervous system ka ek division hai—activate hote hain, ye impulses heart tak bhejte hain jo heart rate increase karte hain, ventricular contractions ko stronger banate hain, aur ultimately higher cardiac output produce karte hain. Iske contrast me, parasympathetic nervous system, especially vagus nerve ke through, antagonistically act karta hai, heart rate reduce karta hai, action potentials ki conduction speed slow karta hai, aur consequently overall cardiac output ko lower karta hai.

Neural control ke alawa, hormonal regulation bhi cardiac activity ko influence karta hai. Adrenal medulla hormones jaise adrenaline aur noradrenaline secrete karta hai, jo heart rate aur force of contraction ko significantly enhance karte hain, is tarah stress, excitement, ya physical activity ke dauran cardiac output boost hota hai. Ye coordinated regulation ensure karta hai ki heart hamesha body ke physiological demands ke according appropriately respond kare.

9. Common Circulatory System Diseases

High Blood Pressure (Hypertension): High blood pressure, jise hypertension bhi kehte hain, ek medical condition hai jisme arteries me blood pressure consistently normal se higher rehta hai. Normal blood pressure reading ko 120/80 mm Hg mana jata hai, jahan 120 mm Hg systolic pressure hai (jab heart blood pump karta hai) aur 80 mm Hg diastolic pressure hai (jab heart relax karta hai). Agar kisi individual ke multiple blood pressure readings consistently 140/90 mm Hg ya usse higher ho, to us person ko hypertensive consider kiya jata hai. Persistent hypertension significantly cardiovascular diseases develop karne ka risk increase karta hai aur over time brain aur kidneys jaise vital organs ko damage kar sakta hai. Ye condition aksar undiagnosed rehti hai kyunki iske clear symptoms nahi hote, isliye regular monitoring essential hai.
Coronary Artery Disease (CAD): Coronary Artery Disease, commonly CAD ya atherosclerosis ke naam se jana jata hai, ek disorder hai jisme coronary arteries (jo heart muscle ko blood supply karte hain) narrow ya blocked ho jati hain. Ye narrowing cholesterol, fat, calcium, aur fibrous tissues ke inner walls me deposit hone ki wajah se hoti hai. Ye deposits ek plaque banate hain jo arteries ka lumen (inner diameter) reduce karta hai, aur heart tak blood flow ko restrict karta hai. Iske result me, heart muscles ko insufficient supply of oxygen-rich blood milta hai, jo chest pain (angina), shortness of breath, ya even heart attack tak lead kar sakta hai. CAD globally death ka ek leading cause hai aur directly lifestyle choices, diet, lack of exercise, aur stress se linked hai.
Heart Failure: Heart failure ek chronic condition hai jisme heart efficiently blood pump nahi kar pata taaki body ke metabolic demands ko meet kiya ja sake. Is condition ke result me poor circulation hoti hai, jo fatigue, breathlessness, aur fluid retention cause karti hai. Heart failure ko aksar congestive heart failure (CHF) ke naam se bhi refer kiya jata hai, kyunki ek major sign lungs ka congestion hai, jo breathing me difficulty create karta hai. Ye samajhna important hai ki heart failure cardiac arrest (jahan heart suddenly beat karna stop kar deta hai) ya heart attack (jahan heart muscle ka ek part blood supply ke lack ki wajah se damage ho jata hai) ke same nahi hai. Heart failure usually gradually develop hoti hai due to long-term conditions jaise hypertension, CAD, ya previous heart attacks.
Angina (Angina Pectoris): Angina, medically termed angina pectoris, ek clinical symptom hai jo acute chest pain se characterized hai. Ye pain tab arise hota hai jab heart muscle ko sufficient oxygen nahi milta due to reduced blood flow, aksar narrowed coronary arteries ke result me. Ye discomfort shoulders, arms, neck, ya jaw tak bhi radiate kar sakta hai. Angina middle-aged aur elderly individuals me zyada prevalent hai, halanki ye kisi bhi age me ho sakta hai. Factors jaise stress, physical exertion, ya emotional disturbances angina attacks ko trigger kar sakte hain. Heart attack ke unlike, angina heart ko permanent damage nahi karta, lekin ye ek underlying heart condition ko indicate karta hai jo medical attention require karti hai.

Final Overview of Body Fluids and Circulation – Class 11 Biology Chapter Notes

Circulatory system vertebrates me essential hai oxygen, nutrients, hormones ke transportation ke liye, aur metabolic waste products ke removal ke liye. Is function me do main body fluids involved hote hain: blood aur lymph.

🔹 Blood Composition and Blood Groups

Blood ek fluid connective tissue hai jo ek liquid portion plasma aur cellular components jise formed elements kehte hain, se bana hai. Ye formed elements include karte hain:

Red Blood Cells (RBCs or Erythrocytes) – Transport oxygen.
White Blood Cells (WBCs or Leucocytes) – Provide immune defense.
Platelets (Thrombocytes) – Help in blood clotting.

Blood ko different ABO groups me classify kiya jata hai based on antigens A aur B ke presence ya absence par RBCs ke surface par. Ek aur important classification hai Rh factor, jo Rhesus antigen ke presence ya absence par based hai.

🔹 Lymph (Tissue Fluid)

Lymph ek clear fluid hai jo blood plasma se derived hota hai. Isme RBCs nahi hote aur protein content lower hota hai. Ye nutrients, fats, aur immune cells ke transport me help karta hai, aur excess fluid ko tissues se wapas blood me return karta hai.

🔹 Types of Circulatory Systems

Open Circulatory System: Found in arthropods and mollusks.
Closed Circulatory System: Ye sabhi vertebrates, including humans, me paya jata hai; blood ek closed network of blood vessels ke through flow karta hai.

🔹 Structure and Function of the Human Heart

Human heart ek muscular, four-chambered organ hai jisme do atria aur do ventricles hote hain. Ye myogenic nature ka hai, matlab ye apni contraction ko external nervous input ke bina initiate kar sakta hai.

Sino-atrial Node (SAN) natural pacemaker ke roop me act karta hai, jo highest number of action potentials generate karta hai (70–75/min).
SAN se electrical impulses atrial systole cause karte hain, followed by ventricular systole, ensuring one-way blood flow.
Ye sequence of events cardiac cycle kehlaata hai, jo lagbhag 0.8 seconds tak last karta hai aur healthy adult me approximately 72 times per minute repeat hota hai.

🔹 Cardiac Output and Stroke Volume

Stroke Volume: Ek ventricle dwara har cardiac cycle me pump kiya gaya blood ka amount (~70 mL).
Cardiac Output: Ek ventricle dwara per minute pump kiya gaya total blood volume = Stroke Volume × Heart Rate = ~5 Litres/min.

🔹 Electrocardiogram (ECG)

Heart ki electrical activity ko record karne ke liye electrocardiograph use kiya jata hai. Iska output, jise electrocardiogram (ECG) kehte hain, P, QRS, aur T waves ke basis par various heart abnormalities detect karne me useful hai.

🔹 Double Circulation in Humans

Humans have double circulation, which includes:

Pulmonary Circulation: Right ventricle deoxygenated blood ko lungs tak pump karta hai oxygenation ke liye. Oxygenated blood wapas left atrium me return hota hai.
Systemic Circulation: Left ventricle oxygenated blood ko aorta ke through poore body me pump karta hai.

🔹 Neural and Hormonal Regulation

Halanki heart self-regulated hai, autonomic nervous system (ANS) aur hormones (jaise adrenaline) heart rate aur contraction ki strength ko influence kar sakte hain.

Sympathetic nerves increase heart rate and output.
Parasympathetic nerves (via vagus nerve) slow it down.

✅ Key Takeaways for NEET and Class 11 Exams:

Blood = Plasma + RBCs + WBCs + Platelets
SAN = Natural pacemaker
Double circulation = Pulmonary + Systemic circulation
ECG detects heart function
Cardiac output ≈ 5 litres/min
Lymph = tissue fluid, returns excess fluid to blood
Regulation by ANS and hormones