Blood — Revision Notes

⚡ 30-Second Revision

Blood Composition — Plasma (55%) + Formed Elements (45%).
Plasma — 90-92% water, 6-8% proteins (Albumin, Globulins, Fibrinogen).
RBCs (Erythrocytes) — Biconcave, anucleated, $5-5.5,\text{million/mm}^3$. Contain Hemoglobin (Hb) for $O_2$ transport. Life span ~120 days.
WBCs (Leukocytes) — Nucleated, $6000-8000/\text{mm}^3$. Immune function. Types:

- Granulocytes: Neutrophils (phagocytic, 60-65%), Eosinophils (allergy/parasites, 2-3%), Basophils (histamine/heparin, 0.5-1%). - Agranulocytes: Lymphocytes (specific immunity, 20-25%), Monocytes (macrophages, 6-8%).

Platelets (Thrombocytes) — Cell fragments, $1.5-3.5,\text{lakh/mm}^3$. Blood clotting.
Blood Groups (ABO) — Antigens on RBCs, Antibodies in plasma. O = Universal Donor (no antigens), AB = Universal Recipient (no antibodies).
Rh Factor — Rh+ (antigen present), Rh- (antigen absent). Rh- mother + Rh+ fetus $\rightarrow$ Erythroblastosis fetalis.
Coagulation — Platelets $\rightarrow$ Prothrombin $\rightarrow$ Thrombin $\rightarrow$ Fibrinogen $\rightarrow$ Fibrin (clot).

2-Minute Revision

Blood is a fluid connective tissue vital for transport, regulation, and protection. It's composed of plasma (the liquid matrix) and formed elements (cells and cell fragments). Plasma, mainly water, carries proteins like albumin (osmotic balance), globulins (immunity), and fibrinogen (clotting).

Red Blood Cells (RBCs) are biconcave, anucleated, and packed with hemoglobin for oxygen transport. White Blood Cells (WBCs) are the immune defenders, categorized into granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes), each with specific roles in fighting infection and inflammation.

Platelets are crucial for initiating blood clotting (coagulation) to prevent blood loss. Blood grouping (ABO and Rh systems) is based on antigens on RBCs and is critical for safe transfusions; Rh incompatibility can lead to erythroblastosis fetalis.

The coagulation cascade is a complex process involving multiple factors, culminating in the conversion of fibrinogen to fibrin by thrombin, forming a stable clot. All blood cells are produced in the bone marrow through hematopoiesis.

5-Minute Revision

Blood, a specialized fluid connective tissue, is approximately 7-8% of body weight, with a pH of 7.35-7.45. It's divided into plasma (55%) and formed elements (45%). Plasma, a straw-colored fluid, is 90-92% water, containing 6-8% proteins (albumin for osmotic pressure, globulins for immunity/transport, fibrinogen for clotting), along with nutrients, hormones, and waste. Formed elements include:

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Erythrocytes (RBCs) — Most numerous ($5-5.5,\text{million/mm}^3$), biconcave, anucleated, contain hemoglobin for $O_2$ transport. Life span ~120 days. Deficiency causes anemia.
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Leukocytes (WBCs) — $6000-8000/\text{mm}^3$, nucleated, immune function. Divided into:

* Granulocytes: Neutrophils (60-65%, phagocytic), Eosinophils (2-3%, allergy/parasites), Basophils (0.5-1%, histamine/heparin). * Agranulocytes: Lymphocytes (20-25%, specific immunity - B & T cells), Monocytes (6-8%, differentiate into macrophages).

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Thrombocytes (Platelets) — $1.5-3.5,\text{lakh/mm}^3$, cell fragments, crucial for hemostasis.

Blood Groups: ABO system (A, B antigens on RBCs; anti-A, anti-B antibodies in plasma). Group O is universal donor (no antigens), Group AB is universal recipient (no antibodies). Rh system: Rh antigen (D antigen) presence (Rh+) or absence (Rh-). Rh- mother carrying Rh+ fetus can lead to erythroblastosis fetalis in subsequent pregnancies due to maternal antibody production.

Blood Coagulation: A cascade preventing blood loss. Injury $\rightarrow$ Platelet plug $\rightarrow$ Release of clotting factors $\rightarrow$ Prothrombin $\xrightarrow{\text{Factor Xa}}$ Thrombin $\rightarrow$ Fibrinogen $xrightarrow{\text{Thrombin}}$ Fibrin (clot). Calcium ions ($Ca^{2+}$) are essential for this process. Heparin is a natural anticoagulant.

Hematopoiesis: Blood cell formation, primarily in red bone marrow, regulated by hormones like erythropoietin.

Example: A patient with blood group A needs a transfusion. They have A antigens and anti-B antibodies. They can receive blood from Group A (compatible) or Group O (no antigens to react with). They cannot receive Group B or Group AB blood due to their anti-B antibodies reacting with B antigens.

Prelims Revision Notes

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Blood Volume & pH — Approx. 5-6 liters in adults, 7-8% body weight. pH $7.35-7.45$ (slightly alkaline).
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Plasma (55%)

* Water (90-92%): Solvent. * Proteins (6-8%): * Albumin: Most abundant, maintains osmotic pressure. * Globulins: Immunoglobulins (antibodies) for defense; transport proteins. * Fibrinogen: Clotting factor (Factor I). * Other: Glucose, amino acids, lipids, hormones, salts, waste products.

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Formed Elements (45%)

* Erythrocytes (RBCs): * Count: $5-5.5,\text{million/mm}^3$ (males), $4.5-5,\text{million/mm}^3$ (females). * Structure: Biconcave, anucleated (in mammals), no mitochondria. * Function: $O_2$ transport via Hemoglobin (Hb).

Hb also transports some $CO_2$. * Life span: ~120 days. Destroyed in spleen ('graveyard'). * Erythropoiesis: RBC formation in red bone marrow, stimulated by erythropoietin (kidneys). * Leukocytes (WBCs): * Count: $6000-8000/\text{mm}^3$.

Larger than RBCs, nucleated. * Function: Immunity. Capable of diapedesis and amoeboid movement. * Granulocytes (lobed nucleus, granular cytoplasm): * Neutrophils (60-65%): Most abundant, phagocytic (bacteria).

* Eosinophils (2-3%): Bilobed nucleus, allergy, parasitic infections. * Basophils (0.5-1%): Least abundant, release histamine (inflammation), serotonin, heparin (anticoagulant). * Agranulocytes (non-lobed nucleus, agranular cytoplasm): * Lymphocytes (20-25%): B-cells (antibodies), T-cells (cell-mediated immunity).

* Monocytes (6-8%): Largest WBCs, kidney-shaped nucleus, differentiate into macrophages (phagocytic). * Thrombocytes (Platelets): * Count: $1.5-3.5,\text{lakh/mm}^3$. * Structure: Cell fragments from megakaryocytes.

* Function: Blood coagulation (hemostasis).

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Blood Groups (ABO System)

* Based on A and B antigens on RBC surface and anti-A/anti-B antibodies in plasma. * Group A: A antigen, anti-B antibodies. * Group B: B antigen, anti-A antibodies. * Group AB: A & B antigens, no antibodies (Universal Recipient). * Group O: No antigens, anti-A & anti-B antibodies (Universal Donor).

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Rh System

* Rh antigen (D antigen) presence = Rh+; absence = Rh-. * Rh- mother + Rh+ fetus $\rightarrow$ Erythroblastosis fetalis (Hemolytic Disease of Newborn) in subsequent Rh+ pregnancies.

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Blood Coagulation (Clotting)

* Mechanism: Injury $\rightarrow$ Platelets activate $\rightarrow$ Release of clotting factors $\rightarrow$ Prothrombin $\xrightarrow{\text{Thrombin}}$ Thrombin $\rightarrow$ Fibrinogen $\xrightarrow{\text{Thrombin}}$ Fibrin (insoluble mesh). * Essential ions: $Ca^{2+}$ (Factor IV). * Anticoagulants: Heparin (natural), EDTA, Sodium Citrate (in vitro).

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Disorders — Anemia (low RBC/Hb), Polycythemia (high RBC), Leukemia (WBC cancer), Leukopenia (low WBC), Thrombocytopenia (low platelets), Hemophilia (clotting factor deficiency).

Vyyuha Quick Recall

To remember the order of WBC abundance (Neutrophils, Lymphocytes, Monocytes, Eosinophils, Basophils - from most to least):

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