Phagocytes Physical Barriers The human body constantly faces attack from foreign invaders that can cause infection and disease. Fortunately, the body has a number of external and internal safeguards that prevent most dangerous invaders from entering and causing harm. Skin, the largest body organ, provides both a physical and a chemical barrier against the outside world.
Phagocytes Physical Barriers The human body constantly faces attack from foreign invaders that can cause infection and disease. Fortunately, the body has a number of external and internal safeguards that prevent most dangerous invaders from entering and causing harm.
The physical barriers that keep them at bay commonly are referred to as the body's first line of defense. Skin, the largest body organ, provides both a physical and a chemical barrier against the outside world. The skin forms a protective layer that completely wraps around the body, shielding blood vessels, nerves, muscles, organs, and bones.
Areas of the body not covered with skin do not go unprotected. Mucous membranes, the moist linings of the respiratory system, produce mucus MYOO-kusa sticky substance that traps irritants that enter through the nose.
Structures like tiny hairs, called cilia SIH-lee-uhline the body's airways and constantly wave foreign particles and mucus away from the lungs to where they can be swallowed safely.
Most harmful microbes that make it to the stomach are destroyed by stomach acids. In addition, tears and saliva both contain enzymes that destroy invaders.
Another important defense mechanism is the brain-blood barrier, a specialized "filter" that surrounds the brain and spinal cord and acts as a physical barrier to keep out proteins, toxins, and most microbes, while letting in glucose, the source of the brain's nutrients.
An animal or plant harboring a parasite is called its host. Parasites live at the expense of the host and may cause illness. A virus can only reproduce within the cells it infects.
The Immune System A second line of defense is housed within the body: This allows cells of the immune army to identify and destroy only those enemy antigens. The ability to identify an antigen also permits the immune system to "remember" antigens the body has been exposed to in the past, so that the body can mount a better and faster immune response the next time any of these antigens appear.
Lymphocytes can be divided into two subgroups: B lymphocytes and T lymphocytes. These protein molecules attach themselves to specific antigens and work with another type of white blood cell, called phagocytes FAH-go-sites —scavenger cells that surround and digest infected cells or microorganisms—to destroy the invaders.
T lymphocytes or T cells help control the immune response and destroy foreign antigens directly. The activity of B cells and T cells targets specific antigens.
This means that each time a new kind of antigen invades the body, the immune system must produce a new round of B cells and T cells, which attack only that antigen. It is estimated that the immune system can create more than million types of antibodies.
As B cells and T cells mature, they begin to recognize which tissues belong in the body and which do not. These cells become "memory" cells that remember a particular antigen, so that the next time it appears, the immune response can mobilize quickly.
The immune system works with amazing complexity. When a B cell encounters a foreign invader, it starts to produce immunoglobulins, or antibodies. Like a key designed to fit only a specific lock, an antibody "locks" onto a single type of antigen like an identifying marker.
Once the antibody attaches to an antigen, one class of T cells called helper T cells alerts other white blood cells to head toward the site, while another class called killer T cells begins to destroy the antigen marked by the antibody.
At the same time, millions of antibodies swarm through the bloodstream to attach to any more of that type of antigen and mount a larger attack. The immune system also includes other proteins and chemicals that assist antibodies and T cells in their work.
Among them are chemicals that alert phagocytes to the site of the infection. The complement system, a group of proteins that normally float freely in the blood, move toward infections, where they combine to help destroy microorganisms and foreign particles. They do this by changing the surface of bacteria or other microorganisms, causing them to die.I'm talking about the body's natural defense mechanism, the immune system.
The function of this system is to prevent or reduce the occurrence of infection. This is accomplished through the coordinated function of the body's immune cells.
Researchers at the Salk Institute for Biological Studies have discovered a powerful mechanism by which viruses such as influenza, West Nile and Dengue evade the body's immune response and infect.
However, certain infections, such as typhoid fever, viral infections, and bacterial infections that overwhelm the immune system, can lead to a decrease in the white blood cell count. Inflammation Any injury, including an invasion by microorganisms, causes inflammation in the affected area.
Aug 04, · Due to the lack of T cells, the immune system has difficulties properly coordinating the fight against the pathogens in the tissue. People who have the immune deficiency AIDS often develop a bacterial inflammation of the lungs with streptococci or get fungal or herpes virus infections, for example.
Dec 02, · The most important and powerful system in the body’s defense mechanism is the lymphatic system. During infection, the immune system will .
Start studying Ch 13 Lymphatic and Immune Systems. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Which of the following is NOT considered to be a innate defense mechanism against infection? antibodies in mother's milk.
Anaphylactic shock may occur due to. Immune System. OTHER SETS BY THIS CREATOR.