Question

Which of the following is not a formed element of blood? a. leukocyte b. eosinophil c. fibrinogen d. platelet

Short answer

The correct answer is c. Fibrinogen, as it is not a cellular component or formed element of blood.

Step-by-step solution

Understand each option

First, we need to understand each of the given options: a. Leukocyte: White blood cells that provide immune defense against foreign substances. b. Eosinophil: A type of leukocyte, involved in allergic reactions and parasitic defenses. c. Fibrinogen: A glycoprotein that is involved in blood clot formation. d. Platelet: Small cell fragments involved in clotting and preventing blood loss.

Identify the non-cellular component

Upon examining the options, note that leukocytes, eosinophils, and platelets are all cellular components of blood, playing roles in various bodily functions. In contrast, fibrinogen is not a cell or cell fragment but a glycoprotein involved in clot formation. It is a soluble protein that becomes insoluble fibrin during clotting.

Select the correct answer

Based on the above understanding, the correct answer is: c. Fibrinogen, as it is not a cellular component or formed element of blood.

Key concepts

Formed Elements of Blood

Blood is a vital fluid in the human body that transports nutrients, gases, and waste products. It consists of two main components: plasma and the formed elements. Formed elements are the cellular components of blood, playing significant roles in body function and protection. They include red blood cells, white blood cells, and platelets. These components are crucial for various bodily functions like oxygen transport, immunity, and clotting.

• Red blood cells (erythrocytes) are responsible for carrying oxygen from the lungs to cells and bringing carbon dioxide back to the lungs for exhalation.
• White blood cells (leukocytes) are a part of the immune system and help the body fight infections and diseases.
• Platelets (thrombocytes) are responsible for blood clotting and wound healing.

Understanding these formed elements is key to recognizing the importance of blood in maintaining homeostasis and overall health.

Leukocytes

Leukocytes, or white blood cells, are a crucial part of the body's immune response. They protect the body against infectious disease and foreign invaders. Unlike red blood cells, leukocytes are colorless because they lack hemoglobin, and they are fewer in number in the blood.
There are several types of leukocytes, each with its own role in immunity:

• Neutrophils: These are the most abundant type of leukocyte and are the first responders to bacterial infection.
• Lymphocytes: They include B cells and T cells, crucial for producing antibodies and enabling immune response memory.
• Monocytes: These are the largest leukocytes, which transform into macrophages and engulf pathogens.
• Eosinophils: These cells are involved in combating parasitic infections and allergic reactions.
• Basophils: They release histamine and are involved in allergic responses.

Each type of leukocyte plays a vital function in the defense system, ensuring the body is protected from harmful pathogens and maintains a balanced immune response.

Blood Clotting

Blood clotting is an essential process that stops bleeding in case of an injury. This process involves the transformation of blood from a liquid to a gel, forming a clot that covers and repairs a wound. It involves several steps and the interaction of different cellular components and proteins.

• When a blood vessel is damaged, platelets gather at the injury site and form a temporary "platelet plug."
• This initial response is followed by the activation of clotting factors in the blood plasma, including proteins like fibrinogen.
• Fibrinogen converts into fibrin, which weaves through the platelet plug, forming a long-lasting clot to prevent further bleeding.

Effective blood clotting prevents excessive blood loss and protects against infection by sealing the wound area. However, improper clotting can lead to conditions such as thrombosis, where clots form inappropriately inside blood vessels.

Cellular Components of Blood

The cellular components of blood, often referred to as the formed elements, fulfill diverse and vital roles in the circulatory system. These components include red blood cells, white blood cells, and platelets. Each of these components plays specific, vital roles in ensuring the body functions correctly.

• Red Blood Cells (RBCs): Their main function is to transport oxygen from the lungs to body tissues and carry carbon dioxide back to the lungs.
• White Blood Cells (WBCs): Also known as leukocytes, their primary function is to defend the body against infections.
• Platelets: They work with blood proteins to stop bleeding by forming clots.

These components originate from bone marrow stem cells and circulate through the bloodstream, contributing to overall bodily health and function. They work together to manage diseases, transport gases, and seal injuries, highlighting the interplay of cellular components in maintaining bodily functions.