Human Immunity and Blood

Without neutralizing antibodies, diphtheria toxin can enter the bloodstream and damage various tissues throughout the body, particularly targeting nerve cells, heart muscle cells (myocarditis), and kidney cells.

Antibodies are crucial because they bind specifically to foreign antigens (like viruses or toxins), neutralizing them by physically blocking them from attaching to and infecting host cells.

Bone marrow contains hematopoietic stem cells, which are a classic example of adult stem cells. These cells are responsible for replenishing the body's blood cells throughout a person's life.

Platelets are small, irregular cell fragments in the blood that clump together to form clots, preventing excessive bleeding when blood vessels are damaged. Plasma is the liquid component of blood, red blood cells carry oxygen, and white blood cells are part of the immune system.

White blood cells, or leukocytes, are the primary cells of the immune system responsible for defending the body against pathogens, infections, and foreign materials. Red blood cells are responsible for oxygen transport, platelets assist in blood clotting, and plasma is the liquid medium that carries these cells.

Blood is considered a fluid connective tissue because it consists of cells suspended in a matrix (plasma).

An antigen is any substance, such as a bacterium, that the body recognizes as foreign and triggers an immune response.

Antibodies are proteins produced by the immune system in response to specific antigens to help neutralize or destroy them.

Neutrophils are the most abundant type of white blood cell and are the first responders to bacterial infections. They use phagocytosis to destroy pathogens.

Leukocytes is the general term for all white blood cells. While some are granulocytes, the term leukocytes encompasses all types involved in the immune response.

Granulocytes are a category of white blood cells characterized by the presence of granules in their cytoplasm. This group includes neutrophils, eosinophils, and basophils.

The spleen plays important roles in regard to red blood cells and the immune system. It removes old red blood cells and holds a reserve of blood, which can be valuable in case of hemorrhagic shock, blood loss and also recycles iron. It purifies the blood and helps the immune system to recognize and attack foreign antibodies and disease. The spleen is composed of the red and white pulp. The white pulp produces and grows immune cell as well as blood cells. On the other hand, the red pulp is responsible for purifying the blood and removing dead or old blood cells.

The lymphatic system returns excess interstitial fluid to the blood. Of the fluid that leaves the capillary, about 90 percent is returned. The 10 percent that does not return becomes part of the interstitial fluid that surrounds the tissue cells. It helps in exchange of gasses, nutrients and removes the metabolic waste. It is devoid of RBC. So, the correct answer is option B.

The lymphatic system returns excess interstitial fluid to the blood. Of the fluid that leaves the capillary, about 90 percent is returned. The 10 percent that does not return becomes part of the interstitial fluid that surrounds the tissue cells. It helps in exchange of gasses, nutrients and removes the metabolic waste. It is devoid of RBC. It contains fewer proteins than plasma and lacks RBC.  So, the correct answer is option A.

WBCs are divided into leucocytes and lymphocytes. Lymphocytes are further divided into macrophages and monocytes. These cells help in the engulfment of any foreign particles inhaled or ingested by our body. Lymphocytes are considered as soldier cells of our body. A Large proportion of these cells is found in the lymphatic system wherein the lymph is present. Thus lymph provides immunity. So, the correct answer is option A.