The mediastinum is the region between the
(a) Lungs and heart
(b) Two pleural cavities
(c) Chest and abdomen
(d) Heart and pericardium

Verified step by step guidance

1. Understand the anatomical location of the mediastinum. It is a central compartment within the thoracic cavity.
2. Recall that the thoracic cavity is divided into two pleural cavities, each containing a lung, and the mediastinum lies between these two cavities.
3. Identify the structures contained within the mediastinum, which include the heart, trachea, esophagus, and major blood vessels.
4. Analyze each option: (a) Lungs and heart - the heart is inside the mediastinum, so this is not the space between lungs and heart; (b) Two pleural cavities - the mediastinum lies between these cavities; (c) Chest and abdomen - these are separated by the diaphragm, not the mediastinum; (d) Heart and pericardium - the pericardium surrounds the heart, so no space between them.
5. Conclude that the mediastinum is the region between the two pleural cavities, making option (b) the correct description.

Key Concepts

Mediastinum Anatomy

The mediastinum is the central compartment of the thoracic cavity, located between the two pleural cavities that contain the lungs. It houses vital structures such as the heart, trachea, esophagus, and major blood vessels.

Pleural Cavities

Pleural cavities are the two separate spaces within the thorax that each surround a lung. They are lined by the pleura, a double-layered membrane, and are separated by the mediastinum.

Thoracic Cavity Boundaries

The thoracic cavity is bounded superiorly by the thoracic inlet, inferiorly by the diaphragm, and laterally by the ribs and muscles. Understanding these boundaries helps define the location of the mediastinum relative to other structures.