Structures HR Flashcards
apex of the heart
is the pointed end of the heart, formed by the tip of the left
ventricle (lower chamber of the heart).
base of the heart
is formed by the atria (upper chambers of the heart).
Heart lies
2/3 of its mass lies to the left of the midline
Two parts of the pericardium:
Fibrous pericardium
Serous pericardium
Fibrous pericardium:
Tough, inelastic and outer connective tissue.
Pericardium functions to protect the heart by:
(a) Anchoring in place (attached to the diaphragm).
(b) Prevents it from over stretching.
Parietal layer:
Fused to the fibrous pericardium
Visceral layer (epicardium):
Adheres tightly to the heart
Made up of three layers: HR
Epicardium
Myocardium
Endocardium
Epicardium
to include the visceral layer of the serous pericardium).
Myocardium
Forms two separate networks via gap junctions and intercalated disks: Atrial
and ventricular.
Each network contracts as a unit.
Endocardium
Lines inside of myocardium and covers valves.
The heart is composed of four chambers:
Two atria [base] and two ventricles. [top]
The two Atrioventricular (AV): Located between atria and ventricles.
(a) Tricuspid Valve (3 cusps).R
(b) Bicuspid (also known as Mitral) Valve (2 cusps). L
Chordae tendineae
connect to papillary muscles (located on ventricle side).
(a) Prevent valve cusps from pushing up into the atria when ventricles contract.
The Semilunar (SL) Valves, close secondary to a pressure change.
(a) Aortic Valve L
(b) Pulmonic Valve R
Superior and Inferior Vena Cava
(1) Both drain deoxygenated blood from the upper and lower body into the right
atrium.
Coronary Sinus
(1) Drains deoxygenated blood from the coronary veins into the right atrium.
Pulmonary trunk and Pulmonary artery
(1) Blood is pumped from the right ventricle into the pulmonary trunk which then
branches into the pulmonary arteries that then carry this deoxygenated blood into
the lungs to be oxygenated.
Pulmonary veins
(1) Carries oxygenated blood from the lungs and transports it to the left atrium.
(a) Left atrium empties into the left ventricle which then pumps blood into the
aorta.
Aorta
Carries oxygenated blood to the entire body from the left ventricle.
DESCRIBE how Blood Flows through the Heart.
Deoxygenated blood enters the heart via the superior and inferior vena cava or coronary sinuses, drains into the right atrium, empties into the right ventricle, then pumped to the lungs via the pulmonary trunk and left and right pulmonary arteries to be oxygenated.
After oxygenation, blood is pumped to the heart by the pulmonary vein into the left
atrium, which empties into left ventricle and is pumped through the body via the
aorta.
A constant, uninterrupted blood supply is essential for the heart’s function.
Blood flow through the myocardium is known as coronary circulation.
There are two principal coronary vessels:
(a) Right coronary artery
(b) Left coronary artery
coronary sinus
collects the heart’s deoxygenated blood and returns it to the right atrium.
Cardiac excitation normally begins in the sinoatrial (SA) node, and is then conducted
through:
(1) The atria (via Bachmann’s bundle) causing contraction.
(2) Atrioventricular (AV) node
(3) AV bundle branches (known as the bundle of his).
(4) Right and left bundle branches
(5) Purkinje fibers
How a wave form is created on electrocardiogram?
Waves on an ECG are created by placing electrodes on the skin to pick up the electrical current generated by the heart.
When reviewing an ECG recording three discernible waves will be noted:
(a) P wave: Representing atrial depolarization
(b) QRS Complex: Representing ventricular depolarization (masks atrial repolarization due to size).
(c) T wave: Representing ventricular repolarization
A cardiac cycle represents everything associated with one heartbeat, typically lasting
0.8 seconds.
P wave:
Representing atrial depolarization
QRS Complex:
Representing ventricular depolarization (masks atrial repolarization due to size).
T wave:
Representing ventricular repolarization
Relaxation period;
the ventricles start to relax and repolarize (repolarization is indicated as the T wave on an EKG); all four chambers of the heart, including the atria enter into a period of diastole (dilation), during diastole, the ventricles are filled to 75%.
atrial systole
(contraction) both atria depolarize (noted as the P wave). After depolarization the last 25% of blood is ejected from the atria to the ventricles.
Ventricular systole
(contraction) is indicated by the QRS complex. The
ventricles depolarize then contract ejecting the blood into either the pulmonary trunk (right ventricle) or the aorta (left ventricle).