Chapter 18: Body Fluids and Circulation - Class 11 NCERT NEET Short Notes

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Chapter 18: Body Fluids and Circulation - Class 11 NCERT*  

_Detailed Short Notes for NEET_

### *1. BODY FLUIDS*

Body fluids are responsible for transport of nutrients, O2, CO2, waste, hormones etc.

*3 main types:*

1. *Blood* - Red, circulates in blood vessels

2. *Lymph* - Colorless, circulates in lymphatic system  

3. *Interstitial fluid* - Fills gap between cells

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### *2. BLOOD*

Blood is a *specialized fluid connective tissue*.  

*Volume*: 5-5.5L in adult. *pH*: 7.4

#### *A. PLASMA - 55%*

- *90-92% Water*

- *6-8% Proteins*: 

    - *Albumin* → Osmotic balance

    - *Globulin* → Immunity, antibodies

    - *Fibrinogen* → Blood clotting

- *Other*: Glucose, amino acids, lipids, hormones, vitamins, Na+, K+, Ca++, HCO3-, Cl-

- *Functions*: Transport, defense, clotting, maintaining body temp

#### *B. FORMED ELEMENTS - 45%*

*1. Erythrocytes / RBCs*

- *Count*: 5-5.5 million/mm³ in males, 4.5-5 million in females

- *Shape*: Biconcave, no nucleus, no mitochondria

- *Color*: Red due to *Haemoglobin* - Fe containing protein

- *Function*: Transport O2 and 20-25% CO2

- *Life span*: 120 days. Destroyed in *spleen* - "graveyard of RBC"

- *Production*: *Bone marrow* - process called *Erythropoiesis*

- *Hormone*: *Erythropoietin* from kidney stimulates RBC production

*2. Leucocytes / WBCs*

- *Count*: 6000-8000/mm³

- *Nucleus present*. Colorless

- *Function*: Defense - Phagocytosis and Antibody production

- *Types - 2 Groups*:

*A. Granulocytes* - Cytoplasmic granules + lobed nucleus

  1. *Neutrophils* 60-65% → Phagocytic, bacterial infection

  2. *Eosinophils* 2-3% → Allergic reaction, parasitic infection, anti-inflammatory

  3. *Basophils* 0.5-1% → Release Histamine, Serotonin, Heparin

*B. Agranulocytes* - No granules

  1. *Lymphocytes* 20-25% → B and T cells, Antibody production. Main in lymph

  2. *Monocytes* 6-8% → Largest, become Macrophages, Phagocytic

*3. Thrombocytes / Platelets*

- *Count*: 1.5-3.5 lakh/mm³

- *Origin*: Fragment of *Megakaryocytes* in bone marrow

- *No nucleus*

- *Function*: Blood clotting, release thromboplastin

- *Life span*: 5-10 days

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### *3. BLOOD GROUPS*

Discovered by *Karl Landsteiner*

#### *ABO Grouping*

Based on *Antigen A, B on RBC* and *Antibody a, b in plasma*

Group Antigen Antibody Genotype Donate to Receive from

**A** A Anti-B IA IA / IA IO A, AB A, O

**B** B Anti-A IB / IB IO B, AB B, O

**AB** A, B None IA IB AB only All - Universal recipient

**O** None Anti-A, Anti-B IO IO All - Universal donor O only

#### *Rh Grouping*

- *Rh+* : D antigen present on RBC - 80% people

- *Rh-* : D antigen absent

- *Problem*: Rh- mother + Rh+ father → 1st child normal, 2nd child *Erythroblastosis fetalis*

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### *4. COAGULATION OF BLOOD*

Prevents excessive blood loss

*Clotting factors*: 13, named Factor I to XIII  

*Key steps*:

1. Injury → Platelets release *Thromboplastin*

2. Prothrombin → *Thrombin* in presence of Ca++

3. *Fibrinogen* → *Fibrin* by Thrombin

4. Fibrin threads form mesh → Trap RBC → *Blood Clot*

Vitamin K needed for clotting factors.

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### *5. LYMPHATIC SYSTEM*

- *Lymph*: Colorless fluid. Has less protein, more WBC, mainly lymphocytes

- *Lymphatic vessels*: Drain excess interstitial fluid back to blood

- *Lymph nodes*: Filter lymph, produce lymphocytes

- *Functions*: Drainage, transport fat from intestine, immune response

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### *6. CIRCULATORY SYSTEM*

*Types*: 

1. *Open* - Arthropods, Molluscs. Blood bathes cells directly

2. *Closed* - Annelids, Chordates. Blood in vessels. More efficient

*Humans have Closed + Double circulation*

#### *DOUBLE CIRCULATION*

Blood passes through heart twice in one complete cycle

1. *Pulmonary circulation*: RV → Lungs → LA. For oxygenation

2. *Systemic circulation*: LV → Body → RA. For supply to body

Advantage: Separate oxygenated and deoxygenated blood

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### *7. HUMAN HEART*

- *Location*: Thoracic cavity, between 2 lungs, slightly left

- *Size*: Adult fist size. *Weight*: 300g

- *Covering*: Double layered *Pericardium* with pericardial fluid

#### *Chambers*

- *Upper*: Right Atrium, Left Atrium - thin wall, receive blood

- *Lower*: Right Ventricle, Left Ventricle - thick wall, pump blood. LV wall thickest

#### *Valves*

1. *Tricuspid valve*: RA and RV between. 3 flaps

2. *Bicuspid/Mitral valve*: LA and LV between. 2 flaps

3. *Semilunar valves*: At base of Aorta and Pulmonary artery. Prevent backflow

#### *Conduction System*

1. *SA Node* → Right upper corner of RA. *Natural pacemaker*. 70-75 impulses/min

2. *AV Node* → Lower left corner of RA

3. *Bundle of His* → From AV node

4. *Purkinje fibres* → Spread to ventricles  

*AV Node delays impulse by 0.1 sec* so atria contract before ventricles

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### *8. CARDIAC CYCLE*

Sequence of events in one heartbeat. *Duration: 0.8 sec*

Phase Duration Event

**Atrial Systole** 0.1 sec Atria contract, blood to ventricles

**Ventricular Systole** 0.3 sec Ventricles contract, blood to aorta + pulmonary artery

**Joint Diastole** 0.4 sec All chambers relax, blood fills atria

*Heart Rate*: 72 beats/min  

*Stroke Volume*: 70ml/beat  

*Cardiac Output*: CO = HR × SV = 72 × 70 = *5 L/min*

*Heart Sounds*: Stethoscope se sunai dete hain

- *1st sound "LUB"* - AV valves close

- *2nd sound "DUB"* - Semilunar valves close

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### *9. ECG - ELECTROCARDIOGRAM*

Graphical recording of electrical activity of heart

- *P-wave*: Atrial depolarization

- *QRS complex*: Ventricular depolarization

- *T-wave*: Ventricular repolarization

Used to detect heart abnormalities

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### *10. BLOOD VESSELS*

1. *Arteries*: Carry blood away from heart. Thick, elastic, no valve. High pressure. Except *Pulmonary artery* carries deoxygenated blood

2. *Veins*: Carry blood to heart. Thin, less elastic, have valves. Low pressure. Except *Pulmonary vein* carries oxygenated blood

3. *Capillaries*: 1 cell thick. Site of exchange of nutrients, gases

*Blood Pressure*: Measured by Sphygmomanometer  

*Normal*: 120/80 mm Hg. *Hypertension*: >140/90

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### *11. DISORDERS OF CIRCULATORY SYSTEM*

1. *Hypertension*: High BP. Leads to heart disease

2. *Coronary Artery Disease*: Plaque deposition in coronary arteries

3. *Angina*: Chest pain due to insufficient O2 to heart muscles

4. *Heart Failure*: Heart can't pump enough blood. Also called Congestive heart failure

5. *Heart Attack*: Death of cardiac muscle due to blockage

6. *Atherosclerosis*: Thickening of artery wall due to fat deposition

7. *Anemia*: Low Hb or low RBC count

8. *Leukemia*: Blood cancer, abnormal increase in WBC

9. *Thrombosis*: Abnormal clot formation in vessel

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#### *NEET PYQ FAVORITE POINTS*

- *SA Node* = Pacemaker. *AV Node* = Pace setter

- *Graveyard of RBC* = Spleen

- *CO = 5L/min*

- *Universal donor = O-, Universal recipient = AB+*

- *Fibrinogen is soluble, Fibrin is insoluble*

- *Double circulation* found in Birds, Mammals, Crocodiles