Physical lines of defense include
1) Skin: The outermost layer of the body acts as a barrier to prevent the entry of harmful pathogens.
2) Mucous membranes: These line the inside of various body systems such as the respiratory, digestive, and reproductive systems. They secrete mucus, which traps foreign particles and prevents their entry into the body.
3) Cilia: These tiny hair-like structures are found in the respiratory tract and help to move mucus and trapped particles out of the body.
4) Saliva and tears: Both saliva and tears contain enzymes and antibodies that can help to kill or neutralize pathogens.
5) Stomach acid: The high acidity of the stomach helps to kill many pathogens that are ingested.
6) Urine: The urinary system helps to flush out bacteria and other pathogens from the body.
7) Coughing and sneezing reflexes: These reflexes help to expel pathogens from the respiratory system.
8) Inflammation: When there is tissue damage or infection, the body responds by increasing blood flow to the area, which results in redness, swelling, and heat. This inflammation helps to isolate and destroy pathogens.
9) Fever: An increase in body temperature can help to inhibit the growth of certain pathogens and stimulate the immune system.
10) Phagocytic cells: These cells, such as macrophages and neutrophils, can engulf and destroy pathogens through a process called phagocytosis.
These physical lines of defense work together to prevent the entry and spread of harmful pathogens in the body.