Final answer:
The sternal angle is a landmark for locating the level of the second costal cartilage and is significant for identifying and counting the lower ribs in the thoracic cage.
Step-by-step explanation:
The sternal angle, also known as the sternal notch or the angle of Louis, is an important landmark for locating the level of the second costal cartilage. It is the junction line between the manubrium and body of the sternum, and it is also the site for the attachment of the second rib to the sternum.
The sternal angle is significant because it serves as a reference point for identifying and counting the lower ribs. Since the first rib is hidden behind the clavicle, the second rib is the highest rib that can be palpated, making it important for identifying the level of other ribs in the thoracic cage.
In summary, the sternal angle is a key anatomical landmark found between the manubrium and body of the sternum. It serves as a reference point for locating the second costal cartilage and is used to identify and count the lower ribs in the thoracic cage.