Thursday, February 7, 2013

Anatomy and the Importance of the Coronary Circulation


Anatomy and the Importance of the Coronary Circulation
Introduction
The circulatory system is responsible for the movement of blood and other body fluids within the body. These body fluids are within the confines of special structures called the blood vessels. Following the pumping of the blood by the heart, blood flows to all parts of the body through systemic, pulmonary and portal circulation. The heart has special muscles called the cardiac muscles whose major role is to contract and relax thus pumping and receiving blood from all parts of the body. The pumping activity of the heart is continuous thus the cardiac muscles require constant supply of oxygen and other nutrients and removal of the waste products. The cardiac muscles receive blood through the coronary artery while the coronary vein drains blood back to the heart chambers. This movement of blood within the heart muscles is called coronary circulation. Understanding circulation requires the understanding of the structure of the heart that shows how the blood vessels are ramified. The study of the body structures in relation to their functions is called anatomy.
 This essay seeks to introduce the anatomy of the heart in relation to its contraction and relaxation thus pumping and receiving blood from other parts of the body. It will also address the importance of coronary circulation in relation to the whole body and in the process show the anatomical changes that may affect the heart and the whole body systems.
The Anatomy of the Heart
The anatomy of the heart is very vital in the explanation of the movement of blood to all parts of the body as it shows the exact structures involved and how effects on the structures affect other body organs. Located in the chest cavity and just posterior to the breast bone, between the lungs and superior to the diaphragm is the heart.
Heart walls
Forming the heart walls are the cardiac muscles whose pumping activity and heart beat enables constant flow of blood to and from other body parts. The cardiac muscles are dividing into three layers epicardium the outer covering layer of the heart, myocardium the middle layer made up of muscles and the endocardium; the inner layer. The endocardium is continuous with the inner lining of the coronary blood vessels. The coronary blood vessels ramify the walls of the heart.
Heart chambers
The heart is divided into four chambers namely; the left and the right ventricles, the left and the right atria. The walls of these chambers are made of the cardiac muscles and are supplied by the coronary blood vessels. Also subdividing the heart vertically is the septum made of the purkinje tissues.

The hearts blood vessels
The blood vessels are hollow tubes that form a network that transports blood throughout the body. From the heart are two types of blood vessels namely the arteries and the veins, The arteries transport oxygenated blood away from the heart except the pulmonary artery that transports deoxygenated blood from the lungs back to the heart. All veins carry deoxygenated blood back to the heart except the pulmonary vein that carries oxygenated blood away from the heart to the lungs.  Among the arteries is the aorta which forms the largest artery in the body and from which branch several arteries including the coronary artery (Seiler, 2009).
 Once blood is pumped from the heart, it leaves the heart through the aorta which now branches down to various arteries supplying the other body organs. Among the branches are the carotid arteries which supply blood to the head region, the subclavian arteries which supply blood to the upper limbs and the coronary artery which supply blood to the heart muscles. The movement of blood through these blood vessels is called systemic circulation.
The coronary blood vessels
These are the blood vessels that supply the heart muscles. They include the coronary arteries and the coronary veins.





The coronary arteries
The Heart and Coronary Arteries
Source: Gaziano, Ridker and Libby (2011)
These are the first branches of the aorta and are further divided into the left coronary artery and the right coronary artery. The left coronary artery branches further into the Left Anterior Descending Artery that supplies oxygenated blood to the septum and the walls of the ventricles and the left atrium on the front side of the heart and the Left Circumflex Artery that supplies oxygenated blood to the walls of the ventricles and the left atrium in the back region of the heart.
 The Right Coronary Artery branches supplies oxygenated blood to the walls of the ventricles and the right atrium and it branches into the Posterior Descending Artery that supplies oxygenated blood to the inferior walls of the left ventricle and the septum. (Gaziano et al 2011)

Coronary veins
            The supply of blood rich in oxygen and nutrients to the heart muscles also leaves with the waste products due to physiological processes like respiration. The ramification of the coronary arteries in the heart walls eventually branch into fine capillary beds that join to form coronary veins that drain blood back into right atrium of the heart.
 Importance of the coronary circulation
The heart is a vital organ of the body whose major function is to transport blood and required nutrients to all body parts through its pumping activity. This means that the heart supplies must be kept constant. To facilitate this blood moves to the heart muscles through the coronary circulation. Coronary circulation therefore promotes the working of the heart through provision of the oxygen and nutrients and removing accumulating waste products.
When there is lack of oxygen reaching the heart muscles, the resulting effect are that the muscles die thus losing their basic function. This is very dangerous as it could cause a heart attack and in severe cases death. Therefore continuous coronary supply helps in promoting good health of the heart thus reducing heart complications.
Coronary circulation promotes the heart beat through contraction and relaxation of the heart muscles. The waves of electrical excitations arising from the Sino Atrial Node (SAN) located in the right atrium reach the base of the heart through the contraction and relaxation of the heart muscles.
Coronary circulation plays a crucial role in transportation of nutrients, oxygen and other chemical substances like drugs to the heart patients targeting the activities of the heart muscle. The drugs may be used to dissolve blood clots within the coronary artery and if so the clots are removed through the coronary veins.
The major organs of the body require oxygen and nutrients that are transported through blood and this is only possible with the effective contraction and relaxation of the heart muscles that occurs when there is good supply of oxygen to the heart muscles through coronary circulation. In essence coronary circulation promotes the good health of the body organs and the body as a whole.
Problems arising from the coronary circulation
According to O'Connor, Brady, Brooks, et al (2010) there are several conditions that arise from the heart and whose effect to the human body and health are worth discussion
Coronary Heart Disease
The coronary artery transports oxygenated blood form the heart to the heart muscles though sometimes, there is accumulation of fatty substances and other materials forming a plaque along the artery walls. This plaque accumulation results in the narrowing of the artery thus may cause slowing or stoppage of blood supply to the heart causing heart complications and even death.
Congestive Cardiac Failure
The Coronary Heart Disease block sufficient blood flow to the heart and coupled with diseases like the High Blood Pressure, there is inability of the heart to pump enough blood to meet the body needs. This means that vital organs of the body may lack important nutrients like oxygen and in return there is accumulation of the wastes in the organs. This disease is characterized by edema shown by the accumulation of the body fluid due to the lack of the pump action of the heart. When these fluids accumulate in the lungs they move into the air spaces causing difficulty inn breathing.
Heart attack
 Also called myocardial infarction and occurs when a section of the heart has no blood supply due to the blockage of the coronary arteries. The accumulation of the plaque in the artery leads to the narrowing of the vessel a condition called atherosclerosis. The section that does not receive the blood may begin to die and if this spreads, the heart ability is lowered. Heart attack can also be caused by coronary artery spasm which involves the tightening of the coronary artery and characterizes blockage of blood flow to the heart. The symptoms of the disease include chest pains, shortness of breath and nausea among others (Zbinden & Meier, 2007)
 Both Heart Attack and Coronary Heart Disease can be illustrated by the diagram below.    
Sources: Valensi, Lorgis, Cottin (2011)

Factors Affecting Coronary Circulation
Coronary circulation can be improved through several factors.
Exercise
Exercise promotes blood flow within the body thus consistent exercises improves the heart pumping capability and eliminates the accumulation of the wastes in the body.
Diet
Foods rich in cholesterol cause the accumulation of cholesterol in the arteries that cause atherosclerosis. Thus by promoting a balanced diet with low cholesterol reduces the risk of heart diseases. (Williams & Restieaux, 2002)  
Conclusion
The anatomy of the heart is important in the explanation of the circulation of blood to various parts of the body. From the essay, it is evident that the coronary circulation plays a guiding role in the performance of other vital body organs through the regulation the supply of oxygen and nutrients to the heart muscles thus regulating the heart pumping capacity. The human coronary circulation functions to prevent various diseases of the heart including Coronary Heart Disease, Heart Attach and Congestive Cardiac Failure. Therefore there is need to protect the heart from damage.




References
Valensi P, Lorgis L, Cottin Y (March 2011). "Prevalence, incidence, predictive factors and           prognosis of silent myocardial infarction: a review of the literature". Arch         Cardiovascular Dis 104 (3): 178–88
Gaziano JM, Ridker PM, Libby P. Primary and secondary prevention of coronary heart disease.    In: Bonow RO, Mann DL, Zipes DP, and Libby P, eds. Braunwald's Heart Disease: A        Textbook of Cardiovascular Medicine. 9th ed. Philadelphia, Pa: Saunders Elsevier; 2011:           chap 49.
O'Connor RE, Brady W, Brooks SC, et al. (November 2010). "Part 10: acute coronary      syndromes: 2010 American Heart Association Guidelines for Cardiopulmonary          Resuscitation and Emergency Cardiovascular Care". Circulation 122 (18 Suppl 3): S787     817
Seiler C. Collateral Circulation of the Heart, 1st edn. Vol. 1. London: Springer; 2009
Zbinden R, Meier P. Coronary collateral flow in response to endurance exercise training. Eur J      Cardiovascular Prev Rehabil 2007; 14:250–7
Williams MJ, Restieaux NJ, (February 2002). "Myocardial infarction in young people        with normal coronary arteries". Heart79 (2): 191–4. PMC 1728590. PMID 9538315