There is an FCT structure within the substance of the heart. This structure is known as the fibrous skeleton of the heart.

This fibrous skeleton serves two general purposes:

• as sites of attachment for muscle tissues

• as supporting structures for the cardiac valves.

Page 2 Fibrous Structures
All of the fibrous structures are continuous and form the fibrous skeleton of the heart.

However they can be divided into three parts as follows:

• The fibrous portion of the interventricular septum.

• The atrioventricular (AV) rings.

• Cylinders at the bases of the great arteries.

Page 3 Fibrous Portion of the Interventricular Septum
The fibrous portion of the interventricular septum - the uppermost portion (also called the membranous portion) of the interventricular septum is a part of the fibrous skeleton of the heart.

Page 4 Atrioventricular Rings
The atrioventricular (AV) rings - each atrioventricular valve of the heart is surrounded by a dense fibrous ring. This ring maintains the valve opening.

Page 5 Cylinders at Bases of Great Arteries
Cylinders at bases of great arteries - each of the semilunar valves of the heart is located within a short fibrous cylinder. This cylinder maintains the structure and function of the valve.