Although up to 2% of the cells die most migrate from the blood to the tissues, mainly the intestines and lungs, where pathogens are most likely to be encountered.Some monocytes leave the blood circulation and migrate to the muscles where they differentiate and become macrophages. These cells differentiate into two types: proliferative macrophages, which are responsible for increasing the number of stem cells  and restorative macrophages, which are involved their maturing to muscle cells. Repair and regeneration
The immune system, particularly the innate component, plays a decisive role in tissue repair after an insult. Key actors include macrophages and neutrophils, but other cellular actors, including γδ T cells, innate lymphoid cells (ILCs), and regulatory T cells (Tregs), are also important. The plasticity of immune cells and the balance between pro-inflammatory and anti-inflammatory signals are crucial aspects of efficient tissue repair. Immune components and pathways are involved in regeneration as well, for example in amphibians such as in axolotl limb regeneration. According to one hypothesis, organisms that can regenerate (e.g., axolotls) could be less immunocompetent than organisms that cannot regenerate. Disorders of human immunity
Failures of host defense occur and fall into three broad categories: immunodeficiencies, autoimmunity, and hypersensitivities. Immunodeficiencies
Immunodeficiencies occur when one or more of the components of the immune system are inactive. The ability of the immune system to respond to pathogens is diminished in both the young and the elderly, with immune responses beginning to decline at around 50 years of age due to immunosenescence.
Classically, hemoperitoneum was an indication for emergency surgery to locate the source of bleeding and also to recover spilled blood from the peritoneal cavity and to use it for auto-transfusion if it has not been contaminated by ruptured bowel contents. The method of control depends on the source of blood loss. Vascular bleeding, i.e. from a blood vessel, would be treated by clamping and ligation of the offending vessel, or repair of the vessel in the case of major arteries such as the aorta or mesenteric arteries. Bleeding from the spleen most often requires splenectomy, or removal of the spleen, usually but not always in the form of a total splenectomy. Bleeding from the liver might be controlled by application of hemostatic sponges, thrombin, or more recently, argon beam cauterization.With modern diagnostic aids such as computed tomography (CT) scans, certain injuries such as low-grade lacerations of the spleen may be diagnosed early and observed, with surgical options deferred unless clinical deterioration obligates them. In rare occasions, rupture of an Abdominal Aortic Aneurysm may be repaired via an endovascular technique, though this is generally not performed in the setting of acute rupture. References


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