Final answer:
The medical term for the collection of coagulated blood under the skin, as experienced by Mr. Chu, is a hematoma, which is the result of bleeding and clotting of blood within tissues due to trauma.
Step-by-step explanation:
The medical term for the accumulation of coagulated blood under the skin, forming a tumor-like area as described in the scenario where Mr. Chu fell and hit his knee, is a hematoma. A hematoma occurs following the rupture of blood vessels, which leads to bleeding and subsequent clotting of blood within the tissues. This process can occur due to trauma, similar to Mr. Chu's situation, or in different scenarios, such as a break in a bone where clotted blood or a hematoma can form at the site of the break. This clotted mass consists of an aggregation of platelets, erythrocytes, and white blood cells caught in a network of fibrin strands. The result is a localized swelling filled with blood that may feel firm or rubbery.
Conditions like thrombocytosis and thrombosis are related to abnormal clot formation within the blood vessels. A thrombus is a clot inside a blood vessel that can restrict or block blood flow, leading to potential complications such as increased local blood pressure or even more severe conditions if parts of the thrombus break off and travel through the bloodstream.