Fundamentals Of Medical: Physiology

But a crisis loomed.

E-1173 was now free in the interstitial space. This was a . Immediately, local smooth muscles in the vessel wall constricted ( vasospasm ). Circulating platelets, sensing exposed collagen, began to adhere, activate, and aggregate. They released ADP and thromboxane A₂, recruiting more platelets. A positive feedback loop had begun. Then, a cascade of inactive enzymes in the blood—the coagulation factors—catalyzed one another in a chain reaction, converting fibrinogen into sticky fibrin threads. Within minutes, a stable clot had formed, sealing the leak. fundamentals of medical physiology

E-1173, however, was trapped and doomed. A macrophage, the tissue’s resident sentinel, engulfed it in a quiet act of . The heme group was broken down into biliverdin, then bilirubin, which the liver would eventually excrete in bile. The iron atom was carefully saved, bound to transferrin, and shipped back to the bone marrow to build a new red blood cell. But a crisis loomed

Now bright and buoyant, E-1173 returned to the left heart and was launched into the systemic circulation. It traveled at breakneck speed through the aorta, then into arteries, then arterioles. The flow was not silent. It heard the faint, rhythmic thump-thump of each heartbeat—the —and felt the pressure wave that would be measured as 120/80 mmHg on a clinician’s cuff. Immediately, local smooth muscles in the vessel wall