ANATOMY

Detailed explanation-1: -The first line of defense includes the skin, mucus, sweat, and tears. These defenses are the body’s barriers against threatening factors in the environment. Therefore, A is the correct answer. Red blood cells do not have the ability to fight pathogens.

Detailed explanation-2: -Skin, tears and mucus are part of the first line of defence in fighting infection. They help to protect us against invading pathogens. You have beneficial bacteria growing on your skin, in your bowel and other places in the body (such as the mouth and the gut) that stop other harmful bacteria from taking over.

Detailed explanation-3: -Some directly fight intruders. They are attracted towards the infective agents, then surround and engulf them. Once inside the cell, these white cells then release chemicals that break the organism down and destroy it. Other white cells, called lymphocytes, target attacks in another way, by making antibodies.

Detailed explanation-4: -For adults, the usual range is generally 4.35 to 5.65 million red blood cells per microliter (mcL) of blood for men and 3.92 to 5.13 million red blood cells per mcL of blood for women. In children, what’s thought of as high depends on age and sex.

Detailed explanation-5: -The bone marrow produces stem cells, the building blocks that the body uses to make the different blood cells – red cells, white cells and platelets. The erythropoietin sends a message to the stem cells telling more of them to develop into red blood cells, rather than white cells or platelets.