Blood Composition
இரத்தத்தின் அமைப்பு
Blood is not just a liquid; it is a specialized connective tissue. If you think it is merely a transport medium, you are failing to see its role as a homeostatic regulator. Remember, the matrix is non-living, but the formed elements are cellular. Do not confuse the two.
The idea
Blood consists of a fluid matrix called plasma and formed elements including erythrocytes, leukocytes, and platelets. Plasma constitutes 55% of blood, while formed elements make up the remaining 45%. It acts as the primary medium for the transport of respiratory gases, nutrients, and metabolic waste products. This composition is essential for maintaining the physiological integrity of higher organisms.
Why it matters
It exists to provide an efficient transport mechanism for essential substances to cells and to remove metabolic waste products for homeostasis.
NEET lens
NEET focuses on the percentage distribution of plasma versus formed elements. Expect questions distinguishing between serum and plasma; remember, serum lacks clotting factors. Memorize the specific cell types and their relative abundance to avoid traps in matching-type questions.
Clinical significance
When the balance of formed elements is disrupted, clinical pathology ensues. Anemia results from a deficiency in erythrocytes or hemoglobin, while leukemia involves the uncontrolled proliferation of leukocytes. These conditions demonstrate that blood composition is the frontline indicator of systemic health.
Introduction
Blood is a specialized connective tissue consisting of plasma (55%, the fluid matrix) and formed elements (45%, the cells and cell fragments) — performing transport, defense, regulation, and hemostasis functions.
Core concept
Total blood volume: ~5-6 litres (adult male). Hematocrit (PCV): % of blood that is RBCs ≈ 45% (male), 40% (female). Plasma (55%): 90% water, proteins, electrolytes, nutrients, hormones, waste, gases. Formed elements (45%): RBCs (99% of cells), WBCs, Platelets. RBCs: 5 million/mm³, biconcave, no nucleus. WBCs: 6000-8000/mm³, nucleated, 5 types. Platelets: 1.5-3.5 lakh/mm³, fragments. Blood pH: 7.35-7.45 (slightly alkaline). Blood is 4-5× more viscous than water.
Go deeper
Blood as connective tissue: all connective tissues have cells suspended in extracellular matrix. In blood, the matrix is liquid (plasma). Blood cells are produced in red bone marrow from common precursor (hematopoietic stem cells). All blood cells ultimately derive from one multipotent stem cell type.
From Class 10
Blood is a connective tissue — it has a fluid matrix (plasma) with cells suspended in it. Understanding blood composition helps explain how it performs its many functions.