We are closer to him than his jugular vein

Question 18: Allah swt said,
{O you who believe, respond to Allah and the messenger when he calls you to that which vivifies you, and know that Allah intervenes between the man and his heart, and [know] that unto Him you will be gathered.} [The Quran 8:24]
And He swt said,
{We verily created the human and We know what his soul whispers to him, and We are closer to him than his jugular vein.} [The Quran 50:16]
What is intended by “the heart” and the “jugular vein” in the two verses?