Of Medical Physiology | Fundamentals

In the beginning, there was a void. Not an empty one, but a bustling, hypoxic darkness deep within the spongy red marrow of a human femur. Here, in the hematopoietic niche, a humble hematopoietic stem cell received a signal: a whisper of the cytokine erythropoietin, released by the kidneys because the blood’s oxygen levels had dipped slightly below a set point.

And E-1173 obeyed. The oxygen disassociated from its hemoglobin and diffused down its concentration gradient into a muscle cell. Inside that muscle cell, the oxygen was immediately consumed by the in the mitochondria, the final step of aerobic respiration, to produce ATP. The jogger’s leg contracted. Homeostasis, at this microscopic level, was being maintained. fundamentals of medical physiology

But a crisis loomed.

When a patient presents with hypertension, kidney failure, or an arrhythmia, the clinician is essentially witnessing a breakdown in one of the mechanisms described above. Mastery of these fundamentals allows a doctor to move beyond memorizing symptoms and instead understand the mechanism of the disease, leading to more precise diagnosis and treatment. In the beginning, there was a void

As E-1173 made its return journey, now a tired, deoxygenated blue, it entered the renal circulation. The kidney was a master of . Blood pressure forced plasma through the glomerulus, but E-1173 was too large to pass. It tumbled through the vasa recta, past the loop of Henle, where countercurrent multiplication was busy concentrating urine. Suddenly, the vessel ruptured. A microscopic tear in the arteriole wall. And E-1173 obeyed

: Physiology begins at the cellular level, focusing on membrane transport, cell signaling, and energy metabolism. 2. Major Organ Systems

The primary function is gas exchange: obtaining $O_2$ and eliminating $CO_2$.