Function. Mechanical contractors are the professionals responsible for the installation of plumbing, heating, cooling, air-conditioning, refrigeration and ventilation systems.efore beginning a job, a mechanical contractor estimates in writing how long it will take to complete a particular job and how much it will cost, and then must complete all required work according to that schedule and in that price range.
In mammals, B cells mature in the bone marrow, which is at the core of most bones. In birds, B cells mature in the bursa of Fabricius, a lymphoid organ. (The B from B cells comes from the name of this organ, where it was first discovered by Chang and Glick, and not from bone marrow as commonly believed). B cells, unlike the other two classes of lymphocytes, T cells and natural killer cells, express B cell receptors (BCRs) on their cell membrane.
Red blood cells are made in the bone marrow in the skull, ribs, sternum (breast bone), spine and pelvis. The stem cells divide and multiply to make the blood cells. These cell â¦ s differentiate (develop and mature) as they grow into white cells, red cells or platelets.1 person found this useful.retty much everything in your body. Without red bloo â¦ d cells or low red blood cells you are either dying, anemic, or could have sickle cell anemia. Red blood cells also help remove CO2 and other waste gases from your body.