**Question:** Most susceptible cells to hypoxia -

A. Neurons
B. Myocytes
C. Red blood cells
D. Skeletal muscle fibers

**Core Concept:** Hypoxia is a condition where there is a decrease in the availability of oxygen to tissues, leading to cellular dysfunction and potential tissue damage. Most susceptible cells to hypoxia depend on the duration, severity, and type of tissue involved.

**Why the Correct Answer is Right:** In this case, the correct answer is **C. Red blood cells (RBCs)**, as they are the primary cells responsible for transporting oxygen to tissues. Under hypoxic conditions, RBCs lose their affinity for oxygen, causing them to release oxygen to tissues more efficiently. However, this adaptation is not sufficient to protect all cells, especially those with high oxygen demands like neurons and myocytes.

**Why Each Wrong Option is Incorrect:**

A. **Neurons:** Although neurons are sensitive to hypoxia, they possess a unique adaptation called ischemic preconditioning, which helps them survive hypoxic episodes. However, they are still not as resistant as RBCs.

B. **Myocytes (cardiac and skeletal muscle cells):** Myocytes have a lower oxygen demand and better ischemic preconditioning than neurons, making them less susceptible to hypoxia initially. However, prolonged hypoxia can still cause myocyte damage.

D. **Skeletal muscle fibers:** While skeletal muscle fibers have a lower oxygen demand compared to neurons, they are still susceptible to hypoxia, especially during prolonged exercise or strenuous activity, causing muscle fatigue and damage.

**Clinical Pearl:** Hypoxia can lead to various clinical consequences, including impaired cognitive function (neurons), arrhythmias (cardiac myocytes), and muscle fatigue (skeletal muscle fibers). Understanding the susceptibility of different cell types to hypoxia is crucial in clinical practice, especially in diagnosing and managing conditions like stroke, myocardial infarction, and respiratory distress syndrome.