Chapter 19 - Section 19.4 - Study Guide - Assess Your Learning Outcomes - Page 740: 5

The twisting mode of ventricular contraction, also known as the "ventricular torsion," refers to the spiral or helical twisting motion that occurs during the contraction of the ventricles in the heart. This twisting motion plays a crucial role in optimizing the efficiency of blood ejection and circulation. Additionally, the tendinous cords, also called chordae tendineae, are essential structures that prevent valvular prolapse and maintain proper heart function. **Twisting Mode of Ventricular Contraction:** During ventricular contraction, the myocardial fibers in the ventricular walls undergo a unique twisting motion. This motion is primarily due to the orientation of these fibers, which are arranged in a helical or spiral pattern around the ventricles. As the ventricles contract, they don't just shorten in a uniform manner; they also twist and wring like a towel being wrung out. This twisting motion results in the apex of the heart moving slightly upward and to the left while the base moves downward and to the right. This motion enhances the ejection of blood from the ventricles by improving the efficiency of ventricular emptying. The twisting mode of contraction also contributes to the maintenance of an effective ventricular contraction pattern and helps prevent turbulence in the blood flow, reducing the risk of stasis and thrombosis. **Importance of Tendinous Cords (Chordae Tendineae):** The tendinous cords are fibrous strands that connect the cusps of the atrioventricular (AV) valves (tricuspid and mitral valves) to the papillary muscles within the ventricles. The papillary muscles are small muscular structures attached to the ventricular walls. The tendinous cords serve several important functions: 1. **Preventing Valvular Prolapse:** During ventricular contraction, the pressure within the ventricles increases. The tendinous cords, anchored by the papillary muscles, prevent the cusps of the AV valves from being pushed back into the atria. This prevents valvular prolapse, which could lead to regurgitation (backflow) of blood into the atria during ventricular contraction. 2. **Maintaining Valve Integrity:** The tendinous cords provide structural support to the AV valve cusps, ensuring that they remain properly aligned and functional during the cardiac cycle. 3. **Coordinating Valve Movement:** The papillary muscles contract slightly before the main contraction of the ventricles. This tension on the tendinous cords ensures that the valve cusps are taut and properly positioned, preventing any backward flow of blood. In summary, the twisting mode of ventricular contraction optimizes blood ejection from the ventricles, while the tendinous cords play a critical role in preventing valvular prolapse and maintaining proper valve function. Together, these mechanisms contribute to the efficient and coordinated pumping action of the heart.

The twisting mode of ventricular contraction, also known as the "ventricular torsion," refers to the spiral or helical twisting motion that occurs during the contraction of the ventricles in the heart. This twisting motion plays a crucial role in optimizing the efficiency of blood ejection and circulation. Additionally, the tendinous cords, also called chordae tendineae, are essential structures that prevent valvular prolapse and maintain proper heart function. **Twisting Mode of Ventricular Contraction:** During ventricular contraction, the myocardial fibers in the ventricular walls undergo a unique twisting motion. This motion is primarily due to the orientation of these fibers, which are arranged in a helical or spiral pattern around the ventricles. As the ventricles contract, they don't just shorten in a uniform manner; they also twist and wring like a towel being wrung out. This twisting motion results in the apex of the heart moving slightly upward and to the left while the base moves downward and to the right. This motion enhances the ejection of blood from the ventricles by improving the efficiency of ventricular emptying. The twisting mode of contraction also contributes to the maintenance of an effective ventricular contraction pattern and helps prevent turbulence in the blood flow, reducing the risk of stasis and thrombosis. **Importance of Tendinous Cords (Chordae Tendineae):** The tendinous cords are fibrous strands that connect the cusps of the atrioventricular (AV) valves (tricuspid and mitral valves) to the papillary muscles within the ventricles. The papillary muscles are small muscular structures attached to the ventricular walls. The tendinous cords serve several important functions: 1. **Preventing Valvular Prolapse:** During ventricular contraction, the pressure within the ventricles increases. The tendinous cords, anchored by the papillary muscles, prevent the cusps of the AV valves from being pushed back into the atria. This prevents valvular prolapse, which could lead to regurgitation (backflow) of blood into the atria during ventricular contraction. 2. **Maintaining Valve Integrity:** The tendinous cords provide structural support to the AV valve cusps, ensuring that they remain properly aligned and functional during the cardiac cycle. 3. **Coordinating Valve Movement:** The papillary muscles contract slightly before the main contraction of the ventricles. This tension on the tendinous cords ensures that the valve cusps are taut and properly positioned, preventing any backward flow of blood. In summary, the twisting mode of ventricular contraction optimizes blood ejection from the ventricles, while the tendinous cords play a critical role in preventing valvular prolapse and maintaining proper valve function. Together, these mechanisms contribute to the efficient and coordinated pumping action of the heart.