Here are concise, exam-focused notes on Blood Physiology organized in clear bullet points 👇
🩸 Blood Physiology (Quick Notes)
1. Definition of Blood
- Blood is a specialized connective tissue.
- Composed of:
- Plasma (55%)
- Formed elements (45%) → RBCs, WBCs, Platelets
2. Functions of Blood
- Transport: O₂, CO₂, nutrients, hormones, waste
- Regulation:
- pH (buffer system)
- Body temperature
- Fluid balance
- Protection:
- Immunity (WBCs)
- Clotting (platelets)
3. Composition of Blood
A. Plasma
- ~90% water
- Proteins:
- Albumin → maintains osmotic pressure
- Globulin → immunity
- Fibrinogen → clotting
- Other:
- Electrolytes (Na⁺, K⁺, Ca²⁺)
- Nutrients, hormones, gases
B. Formed Elements
1. RBCs (Erythrocytes)
- Shape: Biconcave, no nucleus
- Lifespan: ~120 days
- Function: Transport O₂ via hemoglobin
- Normal count:
- Male: ~5–6 million/mm³
- Female: ~4–5 million/mm³
Hemoglobin (Hb)
- Iron-containing protein
- Normal:
- Male: 13–18 g/dL
- Female: 12–16 g/dL
2. WBCs (Leukocytes)
- Function: Defense & immunity
- Normal count: 4,000–11,000/mm³
Types:
- Granulocytes:
- Neutrophils → phagocytosis
- Eosinophils → allergy, parasites
- Basophils → histamine release
- Agranulocytes:
- Lymphocytes → immunity (B & T cells)
- Monocytes → macrophages
3. Platelets (Thrombocytes)
- Count: 150,000–400,000/mm³
- Lifespan: 7–10 days
- Function: Blood clotting
4. Hemopoiesis (Blood Cell Formation)
- Occurs in red bone marrow
- Stimulated by:
- Erythropoietin (from kidneys)
- Requires:
- Iron, Vitamin B₁₂, Folic acid
5. Blood Groups
ABO System
- A, B, AB, O based on antigens
- Important for transfusion compatibility
Rh System
- Rh⁺ / Rh⁻
- Important in pregnancy (Hemolytic disease of newborn)
6. Hemostasis (Clotting Process)
Steps:
- Vasoconstriction
- Platelet plug formation
- Coagulation (fibrin clot)
Clotting Cascade (Simplified)
- Prothrombin → Thrombin
- Fibrinogen → Fibrin
7. Anticoagulants
- Heparin (natural)
- EDTA, Citrate (lab use)
8. Blood Volume
- ~5–6 liters in adults
- ~7–8% of body weight
9. Blood pH
- Normal: 7.35 – 7.45
- Maintained by buffers:
- Bicarbonate system (most important)
10. Disorders (Important for Exams)
- Anemia → ↓ RBC/Hb
- Leukemia → cancer of WBCs
- Thrombocytopenia → ↓ platelets
- Hemophilia → clotting disorder
BLOOD PHYSIOLOGY Study Notes for Medical Students
- Total circulating blood is 8% of total body weight
- Active bone marrow forming the blood cells, is called red marrow,w and inactive marrow is called yellow marrow. Inactive marrow is filled with fats.
- 75% bone marrow belongs to white blood cells, ls producing the myeloid series
- Neutrophils and monocytes are produced from a single precursor. There are separate pools for progenitors of megakaryocytes, lymphocytes, erythrocytes, eosinophils, and basophils.
- Mast cells, Kupfer cells, dendritic cells, osteoclasts, and Langerhans cells also originate from bone marrow.
- The best source of hematopoietic stem cells is umbilical cord blood
- The average half-life of neutrophils in circulation is 6 hours
- Nutrophils, eosinophils, and basophils are collectively called granulocytes/polymorphonuclear cells
- Eosinophils are abundant in the GIT and the respiratory mucosa
- Mast cells are abundant in areas rich in connective tissue, e.g., beneath epithelium
- Monocytes leave the circulation and become macrophages in tissues. They do not reenter the circulation.
- Pluripotent uncommitted stem cells become committed by the action of IL1, IL6, followed by IL3(I,3,6 commits the stem cells, kind of love guru )
- Cytokines are hormone-like molecules that act generally in a paracrine fashion.
- IL1 increases slow-wave sleep and reduces appetite
- Platelets don’t have nuclei. They have a half-life of 4 days
- Splenectomy causes an increase in circulating platelets.
- Cytoplasm of platelets contains actin, myosin, glycogen, lysosomes, and two types of granules: a. Dense granules: they have nonprotein substances. They contain serotonin and ADP b. Alpha granules: contain clotting factors, PDGF
- Platelet production is controlled by colony-stimulating factor and thrombopoietin. Thrombopoietin controls the maturation of megakaryocytes and is produced by the kidney and liver.
- Osmotic fragility of RBC starts at 0.5% saline. Almost half the RBCs are lysed at 0.40 to 0.42% saline. Complete lysis occurs at 0.35% saline.
- 2.5 % hb in adults is HbA2
- Hb F has the ability to decrease the polymerization of deoxygenated HbS. Hydroxyurea causes HbF production and is used in the treatment of HbS.
- Blood group antigens are called agglutinogens.
- Blood group antibodies are called agglutinins.
- Blood group antigens are also present in the salivary gland, saliva, kidney, pancreas, liver, lungs, testes, semen, and amniotic fluid.
- A and B antigens are actually oligosaccharides that differ in their terminal sugar. In RBCs, they are mostly OLIGOSPHINGOLIPIDS, and in other tissues, they are glycoproteins. (past MCQ)
- An antigen called the H antigen is present in all RBCs in all individuals. In blood group A, the A antigen is attached to the H antigen; in blood group B antigen is attached to the H antigen, whereas in blood group O, no antigen is attached to the H antigen, i.e., the terminal part of blood group O is the H antigen(past MCQ). Blood group AB has both antigens at the terminal.
- Bilirubin rarely penetrates the blood-brain barrier in adults. But in neonates and fetuses, the BBB is permeable to it, and in erythroblastosis feotalis it causes KERNICTERUS.
- If whole blood is allowed to clot and the clot is removed, remaining is called serum. (plasma minus factor 2,5,8,fibrinogen is called serum)(past MCQ)
- Serum has a high serotonin level due to the breakdown of platelets.
- Thrombomodulin is produced by all endothelial cells except those of the microcirculation of the brain.
- Thrombin is a procoagulant in circulation blood. It becomes an anticoagulant when it binds to thrombomodulin.
- Lymph has lower protein content than plasma.
- Blood Storage
Storage of different blood products notes
- Whole blood is stored at 4° C for 3 weeks.
- Packed cells (RBCs) are stored at 1-6° C for 35 days.
- FFP (fresh frozen plasma) and cryoprecipitate can be stored at -40° C for 2 years.
- Platelets are stored at 22° C for 5 days
- mitral regurgitation =pansystolic murmur
- mitral stenosis = mid-diastolic murmur
- Aortic regurgitation = end-diastolic murmur
- aortic stenosis =ejection Systolic murmur
- pulmonary regurgitation =diastolic murmur
- pulmonary stenosis =Systolic murmur
- throtoxicosis=innocent murmur
- decrease hematocrit =continuous murmur
- Gastric Motility increased by GASTRIN
- Gastric Motility decreased by CCK
- Intestinal Motility increased by CCK
- Intestinal Motility decreased by SECRETIN
- Gastric Emptying increased by Motilin
- Gastric Emptying decreased by CCK
- Gastric secretions are inhibited by SECRETIN
- If the newborn is 14 years of age or younger, the most common cause is acute lymphoblastic leukemia.
- If the age is between 40 and 60, the most likely cause will be AML and CML
- If the age is more than 60, most likely causes r CLL and CML.
- Repeated blood Transfusion…..HAEMOCHROMATOSIS
- Multiple Transfusions….HYPOCALCEMIA
- Massive Transfusion. ….HYPERKALEMIA, HYPOCALCEMIA, and HYPOTHERMIA
- -Eosinophilia present in:
Hodgkin lymphoma and polyarteritis nodosa.
-PGI2__by endothelial cells
-TXA2__by platelets - Blood transfusion-induced electrolyte balance is as follows:
-hypocalcemia
-hyperkalemia
-hypothermia
-metabolic acidosis
-left shift of oxy-hem curve
Hypokalemia and Hyperkalemia Important Points
| Hypercalcemia causes pancreatitis & Pancreatitis causes hypocalcemia |
| Sodium influx causes depolarization.& Potassium efflux causes hyperpolarization. |
| Hypokalemia causes alkalosis & Metabolic alkalosis causes hypokalemia. |
| Hypokalemiainhibitst insulin releases & Insulin causes hypokalemia |
| Insulin deficiency causes hyperkalemia.&Hyperkalemia causes insulin release. |
| Sodium influx causes depolarization.&Potassium efflux causes hyperpolarization. |
| Hypokalemia causes rhabdomyolysis & Rhabdomyolysis causes hyperkalemia |
| Acidosis causes hyperkalemia.&Hyperkalemia causes metabolic acidosis |
🧠 Blood Physiology Mnemonics
1. Functions of Blood
👉 “TRP”
- T – Transport
- R – Regulation
- P – Protection
2. Plasma Proteins
👉 “All Good Friends”
- A – Albumin
- G – Globulin
- F – Fibrinogen
3. Types of WBCs
👉 “Never Let Monkeys Eat Bananas”
- N – Neutrophils
- L – Lymphocytes
- M – Monocytes
- E – Eosinophils
- B – Basophils
4. Functions of WBCs
👉 “Naughty Little Monkeys Eat Bananas”
- N – Neutrophils → phagocytosis
- L – Lymphocytes → immunity
- M – Monocytes → macrophages
- E – Eosinophils → parasites/allergy
- B – Basophils → histamine
5. Hemostasis (Clotting Steps)
👉 “VPC”
- V – Vasoconstriction
- P – Platelet plug
- C – Coagulation
6. Clotting Factors Pathway
👉 “Extrinsic is EXIT (7)”
- Extrinsic pathway → Factor VII
👉 “Intrinsic = 12, 11, 9, 8”
(Just remember descending order)
7. RBC Production Requirements
👉 “Iron B-Fit”
- Iron
- B₁₂
- Folic acid
8. Blood Groups (ABO)
👉 “O = Zero antigen”
- O → no antigen
- AB → both antigens (universal recipient)
👉 “O gives All”
- O = universal donor
9. Platelet Function
👉 “Plug the Leak”
- Platelets = plug formation
10. Granulocytes vs Agranulocytes
👉 “BENE fits in GRANules”
- B – Basophil
- E – Eosinophil
- N – Neutrophil
👉 Remaining:
- Lymphocyte & Monocyte = Agranulocytes
11. Lifespan Trick
👉 “120 → RBC done”
- RBC lifespan = 120 days
12. Blood pH
👉 “7.4 = Life”
- Normal pH ≈ 7.35–7.45
13. Anticoagulants
👉 “HEC stops clot”
- H – Heparin
- E – EDTA
- C – Citrate
