Human Immunity and Blood

Only mammals have Platelets. Non-mammals possess thrombocytes which are nucleated cells which have been shown to have a haemostatic function paralleling that of mammalian platelets.

A megakaryocyte is a large bone marrow cell with a lobated nucleus responsible for the production of blood thrombocytes (platelets), which are necessary for normal blood clotting.

Platelets, also called thrombocytes, are blood cells whose function is to stop bleeding. Platelets have no nucleus: they are fragments of cytoplasm, which are derived from the megakaryocytes of the bone marrow, and then enter the circulation. These unactivated platelets are biconvex discoid structures. They are smallest of the three major blood types. They make up a tiny portion of the blood volume.

Megakaryocytes cells is thrombocyte producer. A megakaryocyte is a large bone marrow cell with a lobulated nucleus responsible for the production of blood thrombocytes, which are necessary for normal blood clotting. Megakaryocytes normally account for 1 out of 10,000 bone marrow cells but can increase in number nearly 10- fold during the course of certain diseases.

Platelets are a source of thromboplastin. Thromboplastin is a plasma protein aiding blood coagulation through catalyzing the conversion of prothrombin to thrombin. It is a complex enzyme that is found in the brain, lung, and other tissues and especially in blood platelets and that functions in the conversion of prothrombin to thrombin in the clotting of blood, called as thrombokinase.

Structure absent from fresh frozen blood plasma are platelets. Platelets have no nucleus: they are fragments of cytoplasm which are derived from the megakaryocytes. The main function of platelets is to contribute to hemostasis: the process of stopping bleeding at the site of interrupted endothelium. They gather at the site and unless the interruption is physically too large, they plug the hole. In the fresh frozen blood plasma, there will be an absence of blood cells. So, in frozen plasma platelets are also absent.

A megakaryocyte is a large bone marrow cell with a lobulated nucleus, responsible for the production of blood thrombocytes (platelets), which are necessary for normal blood clotting. Megakaryocytes normally account for 1 out of 10,000 bone marrow cells but can increase in number nearly 10-fold during the course of certain diseases.

Blood is living tissue which is made up of liquid and solids. The liquid part, called as plasma, is made of water, salts, and protein. Over half of your blood is plasma. The solid part of your blood contains red blood cells, white blood cells, and platelets. Red blood cells deliver oxygen from your lungs to your tissues and organs. White blood cells fight infection and are part of your body's defense system. Platelets help blood to clot when you have a cut or wound. Bone marrow, the spongy material inside your bones, makes new blood cells. Blood cells constantly die and your body makes new ones. Red blood cells live about 120 days, and platelets live about 6 days. Some white blood cells live less than a day, but others live much longer. 

An antibody is a large, Y-shaped protein produced by the plasma cells that is used by the immune system to identify and neutralize pathogens such as bacteria and viruses. The antibody recognizes a unique molecule of the harmful agent (antigen), via the variable region. They are not formed by the stem cells. All the other statements are correct.
Therefore, the correct answer is option B.

The platelets are formed by fragmenting from cells found in bone marrow called as megakaryocytes, and similar to red blood cells, they do not have a nucleus. The average lifespan of a platelet is normally just 5 to 9 days.  

Red blood cells or RBCs are the most common type of blood cell and contains hemoglobin, which is the principal means of delivering oxygen.
Lymphocyte is a type of white blood cell, that is important in the immune system.
Basophils are granulocytes i.e., they contain large cytoplasmic granules in the cell nucleus and it stores histamine (a vasodilator).
Thrombocyte is a platelet and is crucial for blood clotting.
Thus, the correct answer is option (C), 'Thrombocytes'.

Platelets or thrombocytes are cell fragments produced from megakaryocytes (special cells in the bone marrow). Formation of platelets by fragmentation of megakaryocytes in bone marrow is known as thrombopoiesis.

The blood cells are of three major types they are erythrocytes(RBC), leucocytes(WBC) and platelets. Platelets or thrombocytes are cell fragments produced from megakaryocytes (special cells in the bone marrow). Formation of platelets by fragmentation of megakaryocytes in bone marrow is known as thrombopoiesis. As blood platelets are cell fragments they do not have any nucleus i.e Denucleated.

Thrombocytes are pieces of very large cells in the bone marrow called megakaryocytes. They help form blood clots to slow or stop bleeding and to help wounds heal.