Inflammation

Your body works hard to stay safe.

If you get hurt, your body starts to fix itself. This is called inflammation.

When you are hurt, a part of your body gets red. It can also feel hot. You might see swelling, which makes it look puffy.

It might even hurt.

This happens because more blood flows to the spot. This helps your body fight germs. It also helps clear away damaged parts.

Most of the time, this help stops quickly. But sometimes, the swelling lasts a long time. This can make you feel tired or sick.

It is good that your body reacts to keep you well.

Your body has a way to protect itself from harm. This way is called inflammation. It helps fix damaged parts and fights germs.

There are five main signs of inflammation. You might see redness and feel heat. You may also see swelling, which is puffiness. It can also cause pain. Sometimes, it leads to a loss of function. This means it is hard to move that part of your body.

Acute inflammation is a short-term response. It starts very fast after an injury. This can happen from a cut or a burn. To help, your blood vessels widen. This brings more blood to the area. This extra blood causes the redness and heat.

Fluid also leaks out of the vessels. This fluid makes the area swell. Special cells called neutrophils move from the blood into the tissue. They help fight the problem. Once the injury is fixed, the inflammation stops.

Sometimes, inflammation lasts a long time. We call this chronic inflammation. It can last for months or years. This can lead to many different diseases.

Inflammation is a vital part of how your body defends itself. It is a biological response that helps protect your tissues from harm. Many different things can trigger this response. These include physical injuries, germs like bacteria, or even things like toxins and allergens. Inflammation works to stop the cause of an injury and clear out damaged parts. It also helps your body start the work of repairing tissue. Without it, harmful germs could destroy more of your body.

This process happens in a few specific steps. First, special cells in your tissue notice a problem. They use receptors to find germs or damaged cells. These cells then release chemical signals to call for help. Next, your blood vessels widen to let more blood flow to the area. This extra blood flow causes the area to feel hot and look red.

The vessels also become leaky so fluid can move into the tissue. This fluid causes swelling, which is also called edema. Finally, white blood cells like neutrophils move out of the blood to fight the problem.

People have studied these signs for a very long time. A man named Celsus described the first four signs around 38 BC. These classic signs are redness, swelling, heat, and pain. They have special Latin names: rubor, tumor, calor, and dolor. A fifth sign is called loss of function, or functio laesa. This sign was likely added later by other thinkers like Galen, Thomas Sydenham, or Rudolf Virchow. This means it becomes hard to move the injured part.

There are two main types of inflammation: acute and chronic. Acute inflammation is a short-term response that happens very fast. It usually lasts only a few days and stops once the injury is fixed. If it lasts between two and six weeks, it is called subacute. Chronic inflammation is different because it lasts for months or even years. This type involves different cells, like macrophages and lymphocytes. Chronic inflammation can be linked to many health issues, such as asthma, diabetes, or heart disease.

You can think of acute inflammation like a quick emergency crew. It rushes in to fix a sudden problem and then leaves. Chronic inflammation is more like a long-term struggle that stays in the body. While acute inflammation protects you, too much chronic inflammation can cause trouble. It can lead to things like fatigue, weight changes, or even mood disorders. Understanding these two ways helps us see how our bodies work to stay healthy.

Inflammation is a complex biological defense response used by body tissues. It is a mechanism of innate immunity, meaning it is a general way the body protects itself. The primary goals of inflammation are to eliminate the cause of cell injury. It also works to clear out damaged cells and tissues. Finally, it helps initiate the process of tissue repair. This response is triggered by many different stimuli. These include physical trauma, pathogens like bacteria, toxins, and allergens. It can also be caused by irritants, overuse, or even autoimmune responses.

Acute inflammation is the body's immediate response to a harmful stimulus. This process usually appears within minutes or hours. It typically lasts only a few days and ceases once the stimulus is removed. If the process lasts between two and six weeks, it is called subacute inflammation. Acute inflammation involves a coordinated mobilization of immune, endocrine, and neurological mediators. It relies on the movement of plasma and leukocytes into the injured area. Specifically, granulocytes like neutrophils play a major role here.

The mechanism of acute inflammation begins with resident immune cells. These include macrophages, dendritic cells, histiocytes, Kupffer cells, and mast cells. These cells possess pattern recognition receptors, or PRRs. These receptors bind to two types of molecules. The first are pathogen-associated molecular patterns, known as PAMPs. These are compounds found in pathogens that are different from host molecules. The second are damage-associated molecular patterns, or DAMPs. These are compounds associated with host-related injury and cell damage.

Once these receptors recognize a PAMP or DAMP, the cells undergo activation. They release inflammatory mediators that cause specific physical changes. First, the vascular phase involves vasodilation, which is the widening of blood vessels. Macrophages and endothelial cells release nitric oxide to help this happen. Mast cells and macrophages also release vasoactive amines like histamine and serotonin. This increased blood flow causes redness, known as rubor, and heat, called calor. The vessels also become more permeable, meaning they become leaky. This allows plasma proteins and fluid to leak into the tissue. This accumulation of fluid is called edema, which causes swelling, or tumor.

As the vascular phase progresses, the cellular phase begins. The increased permeability allows leukocytes to move from the blood into the tissue. This process is called extravasation. Neutrophils move toward the injury by following a chemotactic gradient. This gradient is created by local cells to guide them to the site. Other biochemical systems also help. The complement system can activate to promote opsonization, which marks microbes for destruction. The coagulation system forms a protein mesh to protect the site. This mesh can act like construction scaffolding to aid in later repair.

Historically, the signs of inflammation have been documented for a long time. The first four cardinal signs were described by Celsus around 38 BC. These are rubor (redness), tumor (swelling), calor (heat), and dolor (pain). Pain is caused by chemicals like bradykinin and histamine stimulating nerve endings. The fifth sign is loss of function, or functio laesa. This sign was likely added later by Galen, Thomas Sydenham, or Rudolf Virchow. Loss of function can happen due to pain or severe swelling. For example, bronchitis can cause difficulty breathing.

While acute inflammation is protective, chronic inflammation can be harmful. Chronic inflammation lasts for months or even years. It involves a shift toward different cells, such as mononuclear cells, lymphocytes, and plasma cells. This type of inflammation involves simultaneous destruction and healing of tissue. It is associated with many diseases, including atherosclerosis, osteoarthritis, and diabetes. Factors like obesity, smoking, and stress can promote chronic inflammation. It can also lead to symptoms like fatigue, insomnia, and even mood disorders.