Nursing students at UEA study Anatomy and Physiology (A & P) during year 1 and year 2. And at the end of year 2 they get examined. Each organ and part of the human body needs to be studied in detail. Let’s study the heart and prepare for the A & P exam at the end of the year. Each week I will study anatomy and physiology in order to pass.

One of the most fascinating and important organs of the human body is the heart.

Size, Location and Orientation
– approximately the size of the person’s fist, weighs less than a pound
– at the level of the fifth intercostal space, flanked by the lungs, rests on the diaphragm

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(Marieb, 2012)

Coverings and walls of the hear
– lined by the ‘pericardium
– the surface of the heart is the ‘epicardium
– inner layer of the heart wall is the ‘myocardium‘, also know as the ‘skeleton of the heart
– the inner layer of the heart is ‘endocardium

Chambers
– the heart consists of four hollow chambers
– the two upper (receiving) chambers are called right and left ‘atrium
– the two lower (discharging) chambers are called right and left ‘ventricles

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(Marieb, 2012)

Vessels, valves and blood flow
– deoxygenated blood from the body enters the right atrium via the superior and inferior vena cava, passes through the tricuspid valve and into the right ventricle
– deoxygenated blood then passes through the pulmonary valve, and via the left and right pulmonary artery (known as the pulmonary trunk) travels to the lungs where it becomes oxygenated
– oxygenated blood from the lungs then enters the heart via four pulmonary veins, flows into the left atrium, passes through the mitral valve into the left ventricle, passes through the aortic valve and travels to the body rest of the body via the aorta
pulmonary circulation is when blood travels to the lungs and back to the heart
systemic circulation is when blood travels to the rest of the body/all body tissues and back to the heart
Watch KhanAcademyMedicine’s ‘Lub dub’ video explaining how valves work and the ‘lub dub’ sound of the heart:

Function
– acts as a double pump
– pumps blood to the lungs and the rest of the body
– the heart is cover with arteries which provide it with nutrients and oxygen in order to work, if any of these gets blocked then this causes a ‘heart attack’ or heart damage

Nodal system of the heart
– the heart is a muscle, and like any muscle when electric impulses pass through it it contracts
– atrial cells contract once every second or 60 times per minute
– ventricular cells contract slower, about 20-40 times per minute
– the SA node is a mass of cells which starts each heartbeat, also known as ‘pacemaker’

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(Marieb, 2012)

That’s all for this week. Will study more next time.
References:

Marieb, E. N.(2012) ‘Essentials of human anatomy & physiology‘; 10th ed.;  Boston, [Mass.] ; London : Benjamin Cummings, p. 360-366,

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