Papillary Muscles

Overview

Papillary muscles are located in the ventricles of the heart. They attach to the cusps of the atrioventricular valves (also known as the mitral and tricuspid valves) via the chordae tendineae and contract to prevent inversion or prolapse of these valves on systole (or the contraction phase of the heartbeat).

Components of the Papillary Muscles

1. Muscular Projections
   • The papillary muscles themselves are muscular projections that arise from the walls of the ventricles. They are named for their shape, which is similar to that of nipples or small, rounded cones.
2. Chordae Tendineae
   • The chordae tendineae are thin, string-like structures that connect the papillary muscles to the cusps of the atrioventricular valves. They transmit the force from the contracting papillary muscles to the valves.
3. Atrioventricular Valves
   • The atrioventricular valves, specifically the mitral valve (in the left ventricle) and the tricuspid valve (in the right ventricle), are the valves that the papillary muscles help to control. They prevent backflow of blood from the ventricles to the atria during systole.

Functions of the Papillary Muscles

The main functions performed by the papillary muscles include:

1. Preventing Valve Prolapse: The primary function of the papillary muscles is to prevent the atrioventricular valves from inverting (prolapsing) into the atria when the ventricles contract. This ensures that blood flows in the correct direction - from the atria to the ventricles, and then out to the body and lungs.
2. Regulating Blood Flow: By controlling the opening and closing of the atrioventricular valves, the papillary muscles play a key role in regulating the flow of blood through the heart, and therefore to the rest of the body.
3. Supporting Heartbeat: The contraction and relaxation of the papillary muscles, in coordination with the rest of the heart muscle, contribute to the rhythmic beating of the heart.

Diseases and Disorders of the Papillary Muscles

Several diseases or disorders can affect the papillary muscles, such as:

1. Mitral Valve Prolapse: This condition occurs when the mitral valve bulges back into the left atrium when the left ventricle contracts. It can be caused by a variety of factors, including the weakening or stretching of the papillary muscles or chordae tendineae.
2. Papillary Muscle Rupture: This is a severe condition that can occur after a heart attack. If the blood supply to the papillary muscles is disrupted, they can become damaged and potentially rupture, leading to severe mitral regurgitation and heart failure.
3. Papillary Muscle Dysfunction: This can occur as a result of ischemic heart disease or cardiomyopathy, and can lead to mitral regurgitation.

Frequently Asked Questions

1. What are the papillary muscles?
   • The papillary muscles are small muscles located within the ventricles of the heart. They play a crucial role in the functioning of the heart by preventing the inversion of the atrioventricular valves during the contraction phase of the heartbeat.
2. What happens if the papillary muscles are damaged?
   • If the papillary muscles are damaged, they may not be able to perform their function effectively. This can lead to conditions such as mitral valve prolapse or mitral regurgitation, where blood flows back into the atria when the ventricles contract. In severe cases, such as papillary muscle rupture, it can lead to heart failure.

¹ "Papillary muscle." Encyclopædia Britannica, Encyclopædia Britannica, Inc., 2021, www.britannica.com/science/papillary-muscle. ↩