MedPhysio Tutorials | Physiology Made Clear

Quick foundationRead time: 3 minutes

Blood is a specialized connective tissue that circulates through the cardiovascular system to transport substances and maintain homeostasis.

Blood is made up of plasma and formed elements.

~55%

Pale yellow fluid. It is 90% water, together with proteins, nutrients, hormones, electrolytes and waste products.

Main proteins: Albumin, globulins and fibrinogen.

~45%

The cellular components of blood: red blood cells, white blood cells and platelets.

RBC

Erythrocytes

Biconcave and without a nucleus. They contain hemoglobin and transport O₂ and CO₂.

WBC

Leukocytes

Nucleated cells that defend against infection: neutrophils, lymphocytes, monocytes, eosinophils and basophils.

PLT

Thrombocytes

Cell fragments that function in hemostasis and blood clotting.

Transport O₂, CO₂, nutrients, hormones, waste products and heat.

Protection WBCs fight infection; platelets and clotting factors prevent blood loss; antibodies provide immunity.

Regulation Maintains pH, body temperature, and fluid and electrolyte balance.

Clinical relevance

Anemia Low RBC count or hemoglobin → fatigue and pallor.

Leukemia Abnormal WBC proliferation.

Thrombocytopenia Low platelets → bleeding and bruising.

Blood transfusion Replaces deficient components.

Examination tip

Remember: 55% plasma, 45% formed elements.

For WBCs, use “Never Let Monkeys Eat Bananas” → Neutrophil, Lymphocyte, Monocyte, Eosinophil, Basophil.

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