#16 HEART Flashcards
Heart function and characteristics
On average the heart beats 75/minute, 108,000 / day
Average cardiac output is 5.25 L/minute
Functions as a dual pump for the pulmonary and systemic circuit
heart location and orientation
Within the mediastinum
Lies on the diaphragm, posterior to the sternum
Base: Posterior and superior surface of the heart (where great vessels are)
Apex: Anterior and inferior, points to the left hip (where there is a point towards left)
Three layers of pericardium
fibrous pericardium, visceral serous pericardium, parietal serous pericardium
What is the most superficial layer of pericardium?
fibrous pericardium
what does the pericardial cavity contain?
serous fluid
periacarditis
Inflammation of pericardium
What are the three structures of the heart wall?
myocardium, endocardium, epicardium
myocardium
Cardiac muscle
Bulk of the heart wall
Myocardial infarctions occur here
endocardium
Lines chambers and covers valves
Simple squamous epithelium
Called “endothelium”
epicardium
Visceral layer of serous pericardium
Simple squamous epithelium
4 heart chambers
Right atrium
Right ventricle
Left atrium
Left ventricle
heart chambers and circuits
Atria
Ventricles
Pulmonary circuit
Systemic circuit
pulmonary circuit
Carries blood to and from lungs
Right ventricle is the pump
systemic circuit
Transports blood to and from the body tissues
Left ventricle is the pump
Right Atrium
Receiving chamber for oxygen poor blood from systemic circuit
Superior vena cava (1) Inferior vena cava (2) Coronary sinus (3) Interatrial septum (4) Fossa ovalis (5) Foramen ovale during fetal circulation Pectinate muscles (6) Conducting nodes Sinoatrial node (7) Atrioventricular node (8) Right atrioventricular (AV) valve or Tricuspid valve (9)
Right ventricle
Pump of the pulmonary circuit ejects oxygen-poor blood into pulmonary trunk (1) Trabeculae carneae (2) Papillary muscles (3) Anchor chordae tendineae Chordae tendineae (4) Prevent valves from everting Pulmonary valve (5)
Left atrium
Posterior surface of the heart
Receives oxygen-rich blood from lungs through pulmonary veins
Left atrioventricular (AV) valve or Bicuspid or Mitral valve (1)
Left Ventricle
Pump of the systemic circuit
ejects oxygen-rich blood into the aorta (1)
Aortic semilunar valve (2)
Forms the apex and inferior surface of the heart
Most muscular of the chambers
Wall is three times thicker then right ventricle
What is the structure of the heart valve?
Structure: composed of dense connective tissue
Two or three cusps
the function of the heart valve
Function:
Permit passage of blood in one direction
Prevent backflow of blood.
the connective tissue location and function
located between the atria and the ventricles
Functions:
Separates the atria and ventricles (structurally and electrically)
Anchors heart valves
Framework for cardiac muscle attachment
structure of cardiac muscle cells?
Fibers are short, branched, striated, and contain 1-2 nuclei
Cells are joined by intercalated discs
Gap junctions: increase flow of electrical current
Desmosomes: prevent cardiac muscle from pulling apart
More mitochondria and ATP than skeletal muscle
systole
contraction of a heart chamber
Diastole
relaxation of a heart chamber
cardiac cycle
period of time from start of one heartbeat to the initiation of the next
steps in the cardiac cycle
Atrial systole (both atria contract at the same time)
Ventricular systole (both ventricles contract at the same time)
Note: Atrial diastole occurs during ventricular systole
Ventricular diastole (ventricles relax together)
how does the parasympathetic nervous system regulate the heart?
Emerges from the medulla
Vagus nerve (CN X)
Decreases heart rate
How does the sympathetic nervous system regulate the heart?
Emerges from the thoracic spinal cord
Synapses in sympathetic chain ganglia
Increases heart rate and force of contraction
coronary circulation
hearts own blood supply
Brings nutrients and oxygen to the heart wall
Inadequate circulation causes a heart attack (myocardial infarction)
myocardial infarction
results from a lack of blood flow (ischemia) and oxygen (hypoxia) to a region of the heart, resulting in death of the cardiac muscle cells.
often occurs when a coronary artery is blocked by the buildup of atherosclerotic plaque consisting of lipids, cholesterol and fatty acids, and white blood cells, primarily macrophages.
Or can occur when a portion of an unstable atherosclerotic plaque travels through the coronary arterial system and lodges in one of the smaller vessels. The resulting blockage restricts the flow of blood and oxygen to the myocardium and causes death of the tissue.
MIs may be triggered by excessive exercise, in which the partially occluded artery is no longer able to pump sufficient quantities of blood, or severe stress, which may induce spasm of the smooth muscle in the walls of the vessel.
heart failure
Progressive weakening of heart
Heart can no longer pump enough blood to meet the needs of the body.
Weakened ventricles fail to empty completely. They become overfilled and blood backs up into veins behind the ventricle.
May result in edema (congestion) in the tissues outside the pulmonary or systemic circuits.
