Fibrous Skeleton of the Heart

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Hello, I would like to ask for a clarification regarding a passage of my anatomy textbook: I am currently studying the left ventricle of the heart and the mitral valve. The book is Gray's Anatomy but it is a translated version (I'm not from an English-speaking country), so I re-translated it back to English. My doubt is: what are the anterior and posterior coronary fascicles (fascicula)? Could you please explain that to me or link me a picture that shows them?

"The mitral valve ring is stronger near the inner border of the fibrous trigones, from which the anterior and posterior coronary fascicles originate, partially surrounding the valve's orifice at the level of the atrioventricular junction".

Thanks in advance!