Preface

Structural insufficiency of cardiac valves is the basic and featured cardiac pathology. Heart valves allow unidirectional and unobstructed passage of blood without regurgitation, trau‐ ma to blood elements, thromboembolism and excessive stress concentrations in the leaflet and supporting tissue. The ultrastructural histo-architecture of the valvular tissue is the ba‐ sis of mechanical properties of heart valves. New technologies for diagnosis, new research for genetic structure, new definitions for the nature of malformations and malfunctions, new classifications for pathologic types and new surgical approaches to replace dysfunctional be‐ havior will improve the survival of patients with these pathologies. This book tries to detail pathophysiology, general forms and also specific types of structural valvular insufficiencies.

> **Professor Dr Kaan Kırali** Director of Kartal Koşuyolu YIEA Hospital Istanbul, Turkey

**Chapter 1**

**Provisional chapter**

**Structure-Function Relationship of Heart Valves in**

**Structure-Function Relationship of Heart Valves in** 

DOI: 10.5772/intechopen.78280

The heart valves allow unidirectional and unobstructed passage of blood without regurgitation, trauma to blood elements, thromboembolism, and excessive stress concentrations in the leaflet and supporting tissue. In order to achieve this, the heart valves rely of their unique macroscale anatomy, histoarchitecture and ultrastructural features that allow them to accommodate repetitive changes in shape and dimension throughout the cardiac cycle. This chapter is focused on the structure-function relationship of the heart valves, with particular focus on the aortic and mitral valves, discussing how the biochemical, histoarchitectural and anatomical features influence valvular function during the cardiac cycle and how valvular function dictates valvular architecture and ECM constitution. The chapter examines the structure-function relationship of valvular tissue by correlating its microscale histoarchitecture and biochemical constitution to its mesoscale biomechanics and macroscale function during the cardiac cycle. Moreover, the chapter examines the influence of pathological alterations on the histoarchitectural and

biochemical characteristics of the valves on their biomechanical behavior. **Keywords:** heart valves, histoarchitecture, biochemistry, biomechanics,

Connective tissues comprise a network of interweaving fibers with polysaccharide ground substance immersed in a pool of ionic fluid. Cells are attached to the fibers and are responsible for replenishing the extracellular matrix (ECM) macromolecules and the ground substance that carry out the physical function. The ECM contains three major classes of macromolecules, including structural proteins, such as collagen, elastin and fibrillin, specialized proteins, such

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

**Health and Disease**

**Health and Disease**

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.78280

Sotirios Korossis

**Abstract**

structure-function

**1. Introduction**

Sotirios Korossis

#### **Structure-Function Relationship of Heart Valves in Health and Disease Structure-Function Relationship of Heart Valves in Health and Disease**

DOI: 10.5772/intechopen.78280

#### Sotirios Korossis Sotirios Korossis

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.78280

#### **Abstract**

The heart valves allow unidirectional and unobstructed passage of blood without regurgitation, trauma to blood elements, thromboembolism, and excessive stress concentrations in the leaflet and supporting tissue. In order to achieve this, the heart valves rely of their unique macroscale anatomy, histoarchitecture and ultrastructural features that allow them to accommodate repetitive changes in shape and dimension throughout the cardiac cycle. This chapter is focused on the structure-function relationship of the heart valves, with particular focus on the aortic and mitral valves, discussing how the biochemical, histoarchitectural and anatomical features influence valvular function during the cardiac cycle and how valvular function dictates valvular architecture and ECM constitution. The chapter examines the structure-function relationship of valvular tissue by correlating its microscale histoarchitecture and biochemical constitution to its mesoscale biomechanics and macroscale function during the cardiac cycle. Moreover, the chapter examines the influence of pathological alterations on the histoarchitectural and biochemical characteristics of the valves on their biomechanical behavior.

**Keywords:** heart valves, histoarchitecture, biochemistry, biomechanics, structure-function

### **1. Introduction**

Connective tissues comprise a network of interweaving fibers with polysaccharide ground substance immersed in a pool of ionic fluid. Cells are attached to the fibers and are responsible for replenishing the extracellular matrix (ECM) macromolecules and the ground substance that carry out the physical function. The ECM contains three major classes of macromolecules, including structural proteins, such as collagen, elastin and fibrillin, specialized proteins, such

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

as fibronectin and laminin, and glycosaminoglycans (GAGs) and proteoglycans. The ECM is involved in many normal and pathologic processes, playing an important role in tissue development and pathology, and mechanotransduction of the cells [1]. The ground substance is a hydrophilic gel that fills the spaces between the cells and the ECM. Dense connective tissues contain a small amount of ground substance and the cells are mostly fibroblasts. Loose connective tissues contain significantly more ground substance. Ground substance in normal connective tissues is clear and colorless and its composition varies with the tissue. It has a dense consistency similar to that of maple syrup, due to the presence of GAGs and proteoglycans.

The structure and hence the properties of a tissue are dependent on the chemical and physical nature of its constituents and their relative amounts. For example, nervous tissue consists almost entirely of cells, whereas bone is composed of collagen fibers and calcium phosphate minerals with minute quantities of cells and ground substance. Depending on the functional requirements on a particular tissue, the organization of its ECM macromolecules, cells and ground substance, as well as its resulting mechanical properties, vary. The simplest structure from the point of view of the collagen fibers consists of parallel fibers, as in tendons and ligaments. The 2D and 3D networks of the skin are more complex, whereas the structure of blood vessels and heart valves are the most complex ones. This chapter describes the basic biochemistry and function of the major structural proteins, collagen and elastic fibers, as well as the major GAGs and proteoglycans, present in the ECM of the heart valves, and illustrates their physiological and pathological significance. In addition it examines the structural basis, organization and structure-function relationship of valvular tissue, with particular focus on the aortic and mitral valves, by correlating its microscale histoarchitecture and biochemical constitution to its mesoscale biomechanics. Finally, the chapter examines the influence of pathological alterations, as a result of major valvular disease, on the histoarchitectural, constitutional and biomechanical characteristics of the valves.
