23/24. Heart Flashcards
Sides of the heart and their functions
2 sides, 4 chambers
Right side: receives deoxygenated blood from body and pumps blood to lungs (pulmonary circuit)
Left side: receives oxygenated blood from the lungs and pumps to the body (systemic circuit)
Location and physical characteristics of heart
About fist sized
Lies behind sternum but assymetrical
Apex: down to the left
Base: posterior side
Mediastinum: area between lungs
Components of the pericardium
Triple layered sac around the heart
Consists of fibrous pericardium and serous pericardium
Forms pericardial sac (fibrous + parietal layers) and pericardial space (between parietal and visceral layers)
Fibrous pericardium
Outer layer of dense CT
Serous pericardium
Consists of parietal and visceral (aka epicardium) layers
Parietal: outer layer (adhered to fibrous pericardium)
Visceral: inner layer (adhered to heart)
Components of the heart wall
Epicardium = visceral pericardium
Myocardium = cardiac muscle
Endocardium = endothelium + connective tissue
Characteristics of the heart wall in regards to ventricles and atria
Ventricles are thicker than atria
Includes pectinate muscle and trabeculae carnae
Ventricles separated by interventricular septum
Atria separates by interartrial septum
Pectinate muscle
Bands of muscle in atria
Trabeculae carneae
“Beams of meat”
Bands of muscle in ventricles
Passage of oxygen-poor blood through the heart
- Superior vena cava, inferior vena cava, and coronary sinus
- Right atrium
- Through the tricuspid valve
- Right ventricle
- Through the pulmonary semilunar valve
- Pulmonary trunk
Passsage of oxygen-rich blood through the heart
- Four pulmonary veins
- Left atrium
- Through the mitral valve
- Left ventricle
- Through the aortic semilunar valve
- Aorta
Heart valves
2 atrioventriclular (AV) valves and 2 semilunar valves
Atrioventricular (AV) valves of the heart
Between atria and ventricles
Right AV valve (tricuspid valve)
Left AV valve (bicupsid valve)
Semilunar valves of the heart
Between ventricles and arteries
Pulmonary semilunar valve
Aortic semilunar valve
Tricuspid valve
3 cusps
Between right atrium and right ventricle
Includes chordae tendineae - “strings” attach cusps to papillary muscles
Function of tricuspid valve
During ventricle contraction (systole):
Blood pushes valve closed
Papillary muscles contract to pull chordae tendineae taught
Prevents prolapse of cusps into right atrium
Characteristics of bicupsid valve
Also called mitral valve
Has 2 cusps and 2 papillary muscles
Between left atrium and left ventricle
Characteristics of semilunar valves
Pulmonary semilunar valve opens to pulmonary trunk
Aortic semilunar valve opens to aorta
Ventricular systole
Contraction of ventricles
Atrioventricular valves shut
Semilunar valves open
Blood pumped through semilunar valves into pulmonary trunk and aorta
Ventricular diastole
Relaxation of ventricles
Atrioventricular valves open
Semilunar valves shut
Blood pumped from atria into ventricles
Sounds of the heart
We hear “lub-dub”
“Lub” is from atrioventricular valves closing during ventricular systole
“Dub” is from semilunar valves closing during ventricular diastole
Heart murmur
Unusual sound due o faulty heart valve
Can be caused by a valve that doesn’t close properly or a calcification of the valve (stenosis)
In severe cases, surgery or valve replacement is required
Coronary arteries
Aorta, pulmonary trunk, right coronary artery, left coronary artery, circumflex artery, anterior interventricular artery, and posterior interventricular artery
Cardiac veins
Anterior cardiac veins, great cardiac vein, coronary sinus, and middle cardiac vein
Overview of blood supply to cardiac muscle
Anterior interventricular artery runs with great cardiac vein
Anterior cardiac veins cross over right coronary artery
Posterior interventricular artery runs with middle cardiac vein
Atherosclerosis
Fatty deposits in arteries that become plaque and restrict blood flow
Myocardial infarction
Heart attack
Coronary arteries blocked with plaque can’t deliver blood to the cardiac muscle
Muscle cells die and heart can’t function
Bypass graft
Donor blood vessel is sewn to the aorta… “bypassing” the occluded vessel
Operation for MI
Conduction system of the heart
Heart contracts ~72 beats per min
Specialized cardiac muscle cells in the sinoatrial (SA) node generate and propagate an impulse through heart (autorhythmicity)
Impulses travel through walls of atria, then converge on atrioventricular (AV) node
AV bundle carries the impulse down interventricular septum, divides into left and right bundle branches
Purkinje fibers (subendocardial network) extend from apex of heart to walls of ventricles
SA and AV nodes
SA node is the pacemaker of the heart located in right atrium
AV node receives impulses in the right atrium near the tricuspid valve and divides them into bundles
Characteristics of cardiac skeleton
Fibrous connective tissue around heart valves
Prevents spread of conduction directly from atrial walls to ventricle walls
Cardiac skeleton bypassed by AV bundles
Abnormal heart beats
Arrhythmia: abnormal heart rhythm
Ventricular fibrillation: rapid, random electrical firing into the ventricles that leads to cardiac arrest
Atrial fibrillation: random bursts of electrical activity in the atria that creates poorly coordinated contractions and leads to blood clots & stroke
Tachycardia: abnormally high heart rate
Bradycardia: abnormally low heart rate
Innervation of the heart
SA node spontaneously depolarizes ~72 bpm
However, autonomic influence heart rate
Cardiac control center located in medulla oblongata
Sympathetics from the sympathetic trunk increase HR
Parasympathetics from the vagus nerve (CN X) decrease HR
Characteristics of fetal circulation
Lungs are not truly functional until after birth
Developing fetus receives oxygenated blood from the placenta
Umbilical vein carries mother’s blood from placenta to right atrium
Oxygenated blood needs to bypass pulmonary circulation to reach aorta and body tissues
Structures of fetal circulation
Foramen ovale: opening between right and left atria that moves oxygenated blood from right side to left side of heart, bypassing lungs
Ductus arteriosus: connection between pulmonary trunk and aorta
Both structures close off at birth
Congenital heart defects: patent foramen ovale
Also known as atrial septal defect
Foramen ovale between atria fails to close after birth
Leads to symptoms of heart murmur, shortness of breath with exercise, fatigue, cyanosis, and stork due to blood clots passing through opening and traveling to brain
