The human heart, which is roughly the size and shape of a man’s closed fist, contains 4 chambers and 4 valves. The 4 chambers of the heart that divide its internal cavity into four regions are the right atrium, right ventricle, left atrium and the left ventricle. The atria constitute the upper chambers and the ventricles comprise the lower chambers. The two atria have thin walls and receive venal blood. Deoxygenated blood from the systemic veins is received by the right atrium. The left atrium receives blood which is oxygenated from the pulmonary veins. The two ventricles have thicker walls and pump out blood from the heart (National Cancer Institute).
Since the heart functions like a pump, it requires a set of valves to ensure that blood flows in the proper direction. The heart valves are flaps located at the ends of the ventricles. At one end, the valves act as blood inlets, whereas at the other end, they function as blood outlets. In all, there are 4 valves in the human heart-
-Tricuspid valve- situated between the right ventricle and the right atrium
-Pulmonary valve- that lies between the pulmonary artery and the right ventricle
-Mitral or bicuspid valve- located between the left ventricle and the left atrium
-Aortic valve- placed between the aorta and the left ventricle
All the heart valves have three flaps each, except for the bicuspid valve, which contains two flaps. The valves of the heart function as follows- during ventricular contraction, the atrioventricular valves close thereby preventing blood from returning to the atria. During ventricular relaxation, the semilunar valves i.e. aortic and pulmonary valves close to prevent the re-entry of blood into the ventricles (Standford Hospitals and Clinics).
Importance of the Cardiac Skeleton
The human heart wall contains a dense network of connective tissue called as the fibrous skeleton of the heart or the ‘cardiac’ skeleton. This skeleton comprises of four closely-packed rings of connective tissue that surround the four heart valves. It functions to strengthen the myocardium and helps anchor the heart muscle fibers. It also prevents the valve openings from overdilating, acts as the insertion point for cardiac muscle bundles and prevents electrical impulses from spreading directly from the atrial muscles to that of the ventricles (“Heart 4”).
A Few Definitions
Chordae tendinae- These are ropes of fibrous tissue that are attached on the ends to the tricuspid and bicuspid valves on one side and the papillary muscles on the other. These tendons help to keep the valves closed during systole and open during diastole (MedicineNet).
Papillary muscles- These are small muscles placed within the heart that help to secure the heart valves in place. They also help in the opening and closing of heart valves (MedicineNet).
Mitral valve prolapse- This occurs when the mitral valve does not close properly. In this condition, the flaps of the bicuspid valve bulge into the left atrium during heart contraction. At times, this causes blood to flow back into the left upper chamber in which case the condition is termed as mitral valve regurgitation. Most people with mitral valve prolapse do not require treatment or lifestyle changes (Mayo Clinic Staff).
Valvular heart disease- In this condition, one of the four heart valves is damaged or functions defectively. The valves are too stenotic i.e. too hardened and narrow to open completely thus not allowing smooth blood flow or are incompetent i.e. not able to close fully causing back-flow of blood. Since the pumping action of the heart deteriorates in this condition, the heart muscles are overworked causing a decrease in their efficiency and elasticity. Thus, valvular heart disease might lead to congestive heart failure (John Hopkins Medicine).
Rheumatic heart disease- This refers to permanent heart damage that occurs after rheumatic fever. Rheumatic fever causes inflammation in the heart that leads to permanent damage, particularly of the valves. This condition can lead to heart failure and might require surgery for correction. Symptoms of the disease include breathing troubles especially upon exertion and when lying down, chest pain, swelling, fainting and palpitations (Rheumatic Heart Disease Australia).
“Heart 4: Fibrous Skeleton of the Heart.” macanatomy.mcmaster. McMaster University Health Sciences, 2009. Web. 11 Apr. 2014. <http://macanatomy.mcmaster.ca/index.php?option=com_content&view=article&id=225:heart-4-f.>.
John Hopkins Medicine. “Valvular Heart Disease.” hopkindsmedicine. The John Hopkins Hospital, n.d. Web. 11 Apr. 2014. <http://www.hopkinsmedicine.org/heart_vascular_institute/conditions_treatments/conditions/valvular_heart_disease.html>.
Mayo Clinic Staff. “Mitral Valve Prolapse.” mayoclinic. Mayo Foundation for Medical Education and Research, n.d. Web. 11 Apr. 2014. <http://www.mayoclinic.org/diseases-conditions/mitral-valve-prolapse/basics/definition/con-20024748>.
MedicineNet. “Definition of Chordae Tendinae.” medterms. MedicineNet, n.d. Web 11 Apr. 2014. <http://www.medterms.com/script/main/art.asp?articlekey=2717>.
MedicineNet. “Definition of Papillary Muscle.” medterms. MedicineNet, n.d. Web. 11 Apr. 2014. < http://www.medterms.com/script/main/art.asp?articlekey=4755>.
National Cancer Institute. “Structure of the Heart.” training.seer.cancer. National Institutes of Health, n.d. Web. 11 Apr. 2014. <http://training.seer.cancer.gov/anatomy/cardiovascular/heart/structure.html>.
Rheumatic Heart Disease Australia. “What is Rheumatic Heart Disease.” rhdaustralia. Australian Government Department of Health, n.d. Web. 11 Apr. 2014. <http://www.rhdaustralia.org.au/families-community/what-rheumatic-heart-disease>.
Stanford Hospital and Clinics. “Anatomy and Function of the Heart Valves.” stanfordhospital. Stanford Hospital and Clinics, 2014. Web. 11 Apr. 2014. <http://stanfordhospital.org/healthLib/greystone/heartCenter/heartIllustrations/anatomyandFunctionoftheHeartValves.html>.