Responses of tissues to injury

Inflammation is the first response of tissues to injury, leading to the removal of harmful stimuli and damaged tissue.
Neutrophils, a type of white blood cell, are usually the first cells to arrive at the site of an injury.
These immune cells release substances that kill and digest bacteria and damaged tissue, a process called phagocytosis.
Lymphocytes, another white blood cell type, respond later, producing antibodies that target the invaders.
Platelets help to minimise blood loss from injury by forming a clot and releasing substances that help repair damaged blood vessels.

The repair process occurs in two phases: regeneration and fibrosis.
Regeneration involves replacing the damaged tissue with cells of the same type, restoring normal function.
However, not all tissues can regenerate efficiently. In these cases, fibrosis occurs, a process where connective tissue replaces the damaged tissue, forming a scar.
Wound contraction can also take place, where the wound edges move towards each other to reduce the wound size.
Angiogenesis, the creation of new blood vessels, is another important part of the healing process, providing nutrients to the healing tissue.

Responses to chronic injury often involve persistent inflammation and fibrosis, which can lead to loss of normal tissue structure and function.
Conditions like chronic lung diseases, liver cirrhosis, and kidney disease are all associated with chronic tissue injury.
These conditions are often the result of ongoing harmful stimuli such as smoking, alcohol consumption, or persistent infection.

Several factors may affect tissue repair including the type and extent of injury, individual’s age, nutrition status, presence of underlying health conditions, and whether or not infection is present.
Understanding these factors can aid in the management of the healing process and the outcome of tissue repair.

Apoptosis is the process of programmed cell death, which often occurs when a cell is damaged beyond repair.
It’s an important part of tissue homeostasis, eliminating potentially harmful cells in a streamlined and well-managed way.
Malfunction in apoptosis can contribute to diseases such as cancer or degenerative diseases.