Valves of the Human Heart

	Cardiac valves are made of thin fibrous flaps, which  are responsible for maintaining unidirectional blood flow in the heart.

	Maintaining unidirectional blood flow must be maintained for the heart to effectively circulate the blood without causing overexertion.  The four valves of the heart are responsible for maintaining this unidirectional flow.  Following the flow of blood a
s it enters the right atrium from the Venae Cavae, the Tricuspid valve is connects the right atrium and the right ventricle.  The Pulmonic valve prevent the back flow of blood as it is pumped from the right ventricle to the lungs.  The Mitral valve connec
ts the left atrium to the left ventricle, and the Aortic valve prevents the back flow of blood as it is pumped into the aorta from the left ventricle.

	The valves are classified as Semilunar, or Atrioventricular.  The 2 Atrioventricular valves connect the two artia to their respective ventricles, and the 2 Semilunar valves are just outside of each ventricle.  The Mitral valve has 2 cusps, or fibrous fla
ps, while the other three each have 3 cusps.

	Each of the valves opens and closes in a similar manner as will be described here using the mitral valve.  Blood flows into the left atrium, and as the atrium contracts, the mitral valve is forced open by the increase in pressure, and the cusps open into
 the ventricle.  As the ventricle fills, blood will start to leak back into the atria.  This small amount of back flow pushes the almost fully open valves back closed.  Back flow is further prevented by two mechanisms; (1) The cusps in each valve overlap 
as they close, and (2) The papillary muscles in the ventricle prevent the valves from being pushed the wrong way into the atrium during ventricular contraction by pulling them into the ventricle.

Sample Problems:

Problem 1	Draw a diagram of the heart, and label the approximate location of each valve.  Include the valves name, what type it is, how many cusps its has, and what to parts of the heart it connects.


Problem 2	Briefly describe the mechanism by which the heart valves open  and close during blood flow.

Answers:

Answer 1	Refer to diagram and below.
(1)Atrioventricular, 3 cusps, RA and RV
		(2)Atrioventricular, 2 cusps, LA and LV
		(3)Semilunar, 3 cusps, RV and Pulmonary Artery
		(4)Semilunar, 3 cusps, LV and Aorta


Answer 2	Blood flows into the left atrium, and as the atrium contracts, the mitral valve is forced open by the increase in pressure, and the cusps open into the ventricle.  As the ventricle fills, blood will start to leak back into the atria.  This small 
amount of back flow pushes the almost fully open valves back closed.  Back flow is further prevented by two mechanisms; (1) The cusps in each valve overlap as they close, and (2) The papillary muscles in the ventricle prevent the valves from being pushed 
the wrong way into the atrium during ventricular contraction by pulling them into the ventricle.

For more information on this topic, please refer to Berne & Levy , Refer to pages 64-71 in test.

Also, check out the following links that may be helpful:

• Library of Heart Diagrams
• Heart Valves and Their Function
• And, as always, if you have questions, or if you can suggest a helpful link, please e-mail me.

No!
Please don't make me go to any of those pages!
I want to go somewhere completely different!

This page was written by Chris Hass ,a student in this course.

BME 403 Pages maintained by the T.A., Douglas Miles.