An embolism is a blood clot that forms in a blood vessel. Based on that description, explain what a pulmonary embolism is and its potential effect on the body’s circulation.

A pulmonary embolism (PE) is a serious medical condition that occurs when a blood clot (embolus) travels to the lungs and obstructs one or more pulmonary arteries. This typically happens when a blood clot forms in a deep vein, usually in the legs (a condition known as deep vein thrombosis or DVT), and then dislodges and travels through the bloodstream to the lungs.

**Potential Effects on the Body’s Circulation:**

1. **Obstruction of Blood Flow**: The primary consequence of a pulmonary embolism is the blockage of blood flow to lung tissue. This can lead to reduced oxygen exchange, as the affected areas of the lung can no longer receive adequate blood supply.

2. **Reduced Oxygen Levels**: As blood flow is obstructed, the body’s ability to oxygenate blood is compromised. This can result in lower oxygen levels (hypoxemia) in the bloodstream, which can affect the oxygen supply to vital organs.

3. **Increased Pressure in Pulmonary Circulation**: The blockage increases pressure in the right side of the heart and the pulmonary arteries, leading to a condition known as pulmonary hypertension. This can strain the heart and may eventually lead to right heart failure if the pressure remains elevated.

4. **Potential Damage to Lung Tissue**: Prolonged obstruction can lead to ischemia (lack of blood flow) in the lung tissue, resulting in pulmonary infarction where parts of the lung become necrotic (dead), leading to further complications such as pneumonia or pleural effusion.

5. **Systemic Effects**: Severe cases of PE can lead to systemic hypotension (low blood pressure) and, in extreme cases, cardiovascular collapse or shock. This can manifest as symptoms including rapid heartbeat, shortness of breath, chest pain, dizziness, or even loss of consciousness.

Overall, a pulmonary embolism constitutes a medical emergency that requires prompt diagnosis and treatment to restore blood flow and minimize complications. Treatment often includes anticoagulants (blood thinners), thrombolytics (clot-busting medications), and in some cases, surgical intervention.