#immunity #bloodcells #virus #bacteria

The Body Defense System
The body defense system, also known as the immune system, is a complex network of cells, tissues, and organs that work together to protect the body from harmful pathogens such as bacteria, viruses, fungi, and parasites. It also identifies and neutralizes harmful substances and abnormal cells, including cancer cells.

Key Components of the Body Defense System:
Physical Barriers:

Skin: Acts as the first line of defense, preventing the entry of pathogens.
Mucous Membranes: Found in the respiratory, digestive, and urogenital tracts, these trap and expel pathogens.
Cilia: Hair-like structures in the respiratory tract that move mucus and trapped pathogens out of the lungs.
Tears and Saliva: Contain enzymes like lysozyme that kill bacteria.
Innate Immunity:

Phagocytes: White blood cells (e.g., macrophages and neutrophils) that engulf and destroy pathogens.
Natural Killer (NK) Cells: Destroy infected or cancerous cells.
Inflammatory Response: Activated by injury or infection, leading to redness, heat, swelling, and pain, which help isolate and eliminate the threat.
Complement System: A group of proteins that enhance the ability of antibodies and phagocytic cells to clear pathogens.
Adaptive Immunity:

Lymphocytes:
B Cells: Produce antibodies that target specific pathogens.
T Cells: Include helper T cells (which activate B cells and other immune cells) and cytotoxic T cells (which kill infected cells).
Memory Cells: Created after an infection, they allow for a faster and stronger response if the same pathogen invades again.
Other Defense Mechanisms:

Fever: Raises body temperature to slow down pathogen growth.
Microbiome: Beneficial microbes that outcompete harmful pathogens in the body.
Key Features:
Specificity: Adaptive immunity targets specific pathogens.
Memory: The immune system remembers previous infections for quicker responses in the future.
Self-tolerance: It distinguishes between the body’s cells and foreign invaders to avoid attacking itself (although this can fail in autoimmune diseases).
The body defense system is vital for maintaining health and preventing infections. A healthy lifestyle, including proper nutrition, exercise, and vaccination, helps strengthen this system.