Final answer:
The internal jugular vein drains blood mainly from the brain and empties into the subclavian vein, while the external jugular vein drains the superficial areas of the head and neck. Jugular venous distension (JVD) is an important clinical sign indicating increased right-sided heart pressure. JVD reveals potential issues such as heart failure or fluid overload.
Step-by-step explanation:
The internal jugular vein is one of a pair of major veins located in the neck region that drains blood primarily from the brain. It runs parallel to the common carotid artery through the jugular foramen and canal, receives blood from the superficial facial vein, and empties into the subclavian vein. The external jugular vein, another major vein in the superficial neck, drains blood from the more superficial parts of the head, like the scalp and cranial regions. Jugular venous distension (JVD) can be an important sign, revealing increased pressure in the right side of the heart, often associated with heart failure, fluid overload, or constriction of the heart or the pericardium.
Both internal and external jugular veins have anastomoses near the thoracic region. JVD is an enlargement of the jugular vein which can indicate that the right atrium or ventricle is challenged in pumping blood effectively, causing blood to back up into the venous system. The systemic circulation involves the flow of blood away from the heart to various organs and limbs and then back to the heart, with the superior vena cava playing a role in draining blood from the jugular veins from the brain and the subclavian veins from the arms.