The apex of an adult heart usually lies in the left4thintercostal space mid axillary line5thintercostal space mid axillary line5th intercostal space mid clavicular line6th intercostal space mid clavicular line

The apex of an adult heart usually lies in the 5th intercostal space mid clavicular line.

Here's a step-by-step explanation:

1. The heart is located in the chest, between the lungs, behind the sternum, and slightly to the left. It is surrounded by the rib cage.

2. The intercostal spaces are the spaces between the ribs. There are 11 intercostal spaces on each side of the chest, numbered from top to bottom.

3. The clavicular line is a vertical line running down from the midpoint of the clavicle (collarbone).

4. The apex of the heart, the lower pointed end, tilts towards the left and is located at the level of the 5th intercostal space in the midclavicular line.

So, when you're trying to locate the apex of the heart, you would count down to the 5th space between the ribs from the top, and then find the midpoint of the collarbone and draw an imaginary line down, where this line crosses the 5th intercostal space is typically where you'd find the apex of the heart.