Biology · Body Fluids and Circulation · NEET
No. Plasma is the fluid matrix of blood, not a formed element. Blood has two parts: the liquid part (plasma, about 55%) and the cellular part (formed elements, about 45%). Formed elements are only the cells and cell fragments — RBCs, WBCs and platelets. NEET often frames a trap question mixing these two, so remember: plasma = matrix, formed elements = cells.
Formed elements make up nearly 45% of the blood by volume, and plasma makes up about 55%. This 45/55 split is a direct NCERT line and a common one-mark question. RBCs form the bulk of this 45% because they are by far the most numerous cells.
Platelets (thrombocytes) are cell fragments, not complete cells. They are produced from large bone-marrow cells called megakaryocytes. So of the three formed elements, RBCs and WBCs are cells, while platelets are fragments. They still count as formed elements. A healthy person has 1.5 to 3.5 lakh (150,000-350,000) platelets per mm³ of blood.
Erythrocytes (RBCs) are the most abundant of all cells in blood. A healthy adult man has on average 5 to 5.5 million RBCs per mm³. Among white blood cells specifically, neutrophils (60-65%) are the most abundant type. Do not confuse the two: RBC is the most abundant formed element, neutrophil is the most abundant WBC.
RBCs are formed in the red bone marrow in adults. Platelets are produced from megakaryocytes, which are also special cells of the bone marrow. Most WBCs also originate from bone marrow (some lymphocytes mature in lymphoid organs). So the bone marrow is the main factory for formed elements.
They mean nearly the same thing. 'Formed elements' is the NCERT term and is preferred for NEET. It covers erythrocytes, leucocytes and platelets. 'Blood corpuscles' is an older term usually meaning RBCs and WBCs (the true cells). To be safe in exams, use the NCERT phrasing: erythrocytes, leucocytes and platelets are collectively called formed elements.
Name the blood cells, whose reduction in number can cause clotting disorder, leading to excessive loss of blood from the body.
Match List-I (WBC) with List-II (percentage): (A) Eosinophils (B) Lymphocytes (C) Neutrophils (D) Monocytes | (I) 6-8% (II) 2-3% (III) 20-25% (IV) 60-65%
The WBC count of a person's blood sample is 8000/cu mm. How many eosinophils and lymphocytes would be in the same sample approximately?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Erythrocytes (red blood cells), leucocytes (white blood cells) and platelets (thrombocytes). Together they are collectively called formed elements and constitute nearly 45% of blood.
Nearly 45% by volume. The remaining ~55% is plasma, the fluid matrix. RBCs contribute most of this 45% because they are the most numerous.
Erythrocytes (RBCs). A healthy adult man has about 5 to 5.5 million RBCs per mm³ of blood, far more than WBCs or platelets.
No. Platelets are cell fragments budded off from megakaryocytes in the bone marrow. They lack a nucleus and are not complete cells, but they are still classed as formed elements.
Because they are the solid, structured (formed) cellular components of blood, as opposed to the liquid plasma matrix. The term groups RBCs, WBCs and platelets together.
