Module 3 - Heart Flashcards
Structure of Heart
Structure of Heart
In Thoracic cavity
Between lungs in mediastinum
2/3s of heart to left of midline
Size of fist
Board at top and tapers at base
Bottom – Apex
Pericardium
Pericardium – encloses and holds in place
Outer fibrous pericardium – dense connective tissue
Inner serous pericardium – secrets fluid
Parietal layer
Pericardial cavity – pericardial fluid – reduces friction
Visceral layer – Epicardium – shared by membrane and heart wall
Heart walls – superficial to deep
Heart walls – superficial to deep
Epicardium
Myocardium
Endocardium
Epicardium
Epicardium – visceral layer of pericardium – mesothelium and connective tissue
Myocardium
Myocardium – thick cardiac muscle – contracts to pump – collagenous fibers, blood vessels, and nerve fibers – make fibrous rings around valves – thickness varies
Superficial layer – continuous all around the heart – figure 8 pattern
Deep layer – longitudinal – make up inner muscle
Middle layer – circular fibers – surround ventricles – left ventricle is thicker, more force needed b/c pumps further with greater resistance
Endocardium
Endocardium – lines chambers and forms cusps of valves – made of endothelium and connective – help regulate contract and growth – direct contact with blood – double layer for cusps valves
Chambers
4 Chambers: divided upper & lower, and left & right
Two upper atria – blood in
Two lower ventricles – blood out
Septum
Septum – divides atria into left and right – oval depression called fossa ovalis
Auricles
Auricles – extension of an atrium visible on superior surface of heart – small pouches – slightly increase capacity of atria
Valves
4 Valves – open and close w/ pressure changes at contraction and relaxation – prevent back flow
Atrioventricular valves:
Tricuspid valve
Bicuspid/mitral valve
Semilunar valves
Pulmonary semilunar valve
Aortic semilunar valve
Atrioventricular valves
Atrioventricular valves – between atria and ventricles – open when pressure is great in atria – close when pressure is greater in ventricles
Tricuspid valve
Bicuspid/mitral valve
Tricuspid valve
Tricuspid valve – right atrium to right ventricle
Bicuspid/mitral valve
Bicuspid/mitral valve – left atrium to left ventricle
Semilunar valves
Semilunar valves – eject blood from ventricles to body – open when pressure is greater than arteries
Pulmonary semilunar valve
Aortic semilunar valve
Pulmonary semilunar valve
Pulmonary semilunar valve – right ventricle to pulmonary trunk
Aortic semilunar valve
Aortic semilunar valve – left ventricle to aorta
Papillary muscles & Chordae Tendineae
Papillary muscles & Chordae tendineae – support atrioventricular valves in preventing backflow of blood from vents to atria
Pulmonary Circuit
Pulmonary Circuit – Deoxygenated blood – Right Side
From body into Right Atrium – superior and inferior vena cava, and coronary sinus (heart blood)
Right Atrium to Right ventricle – passes tricuspid valve
Right ventricle to lungs – passes pulmonary valve to pulmonary trunk
Trunk to left and right pulmonary arteries
To lungs for gas exchange in pulmonary capillaries
Systemic Circuit
Systemic Circuit – Oxygenated blood – Left side
From lungs into Left Atrium – left and right pulmonary veins
Left atrium to left ventricle – passes bicuspid/mitral valve
Left ventricle to aorta – passed aortic semilunar valve
Aorta to body
Coronary Circulation
Coronary Circulation
Heart needs nutrients and O2
Myocardium and epicardium need blood
Blood supply through coronary arteries
Feeds heart during relaxation (Diastole) – during contraction, heart pushes blood from left ventricle to aorta to body – during relaxation, blood pools at the valve and files arteries
Two Major Arteries - Coronary Circulation
Two major Arteries – left & right – from trunk of Aorta
Left coronary artery:
Left Anterior Descending Artery
Circumflex Artery
Right coronary artery:
SA nodal artery
Right Marginal Artery
Posterior Descending Artery (PDA)
Left Coronary Artery
Left coronary artery – branches at front to:
Left Anterior Descending Artery (LAD) – goes down interventricular septum to apex and goes behind – feeds most of left atrium and left vent
Circumflex Artery – around back – feeds back left of heart – branches to:
Left Marginal artery – down the left lateral heart – feeds left vent
Right coronary artery
Right coronary artery – travels towards back of heart – branches at:
SA nodal artery – on top of right atrium – feeds SA node
Right Marginal Artery – feeds right
Posterior Descending Artery (PDA) – makes CRUX, cross at back of heart – can joins with LAD, Anastomosis
Anastomosis
Anastomosis – two arteries connect – detour if area is blocked
Cardiac Veins
Cardiac Veins – take deoxygenated blood from myocardium back to Right Atrium
Coronary sinus
Great Cardiac Vein
Middle Cardiac Vein
Small Cardiac Vein
Coronary Sinus
Coronary sinus – connected to right atrium, drains all blood in – all three veins drain blood into
Great Cardiac Vein – parallels LAD – starts at anterior apex of heart – Up septum – around to back
Middle Cardiac Vein – starts posterior apex – up septum
Small Cardiac Vein – right margin – around to posterior
Conducting System
Conducting System
Cardiac muscle cells – self-excitable autorhythmic cells – myocardial contractile cells – specialized muscles fibers acting as nerves
60-100/minute
Repeated generating action potentials – trigger heart contractions
Establishes its own fundamental rhythm
ANS and hormones (epinephrine and norepinephrine) modify heartbeat (speed and strength)
Conduction Components
Components
SA Sino-atrial Node – pacemaker – Top of right Atrium
AV Node – bottom of right atrium
Atrioventricular Bundle (bundle of his) – top of septum – bundle of neurons
Right & Left Bundle branches – splits to left and right ventricles
Purkinje Fibers – left and right ventricles – little off shoots it the myocardium of ventricles
Conduction Steps
SA at rest
Initiates action potential – sweeping across atrium to AV
Atria contract – atrial systole
Received trigger
Delay to allow atria complete pump
Impulse travels down and branches
Atrial diastole
Spreads action potential to left and right ventricles
Contraction – ventricle systole
Electrocardiogram
Electrocardiogram
Impulse conductions make electrical currents
Detectable on surface with ECG – electrocardiogram – records action potentials
P wave – atrial depol
QRS complex – ventricular depol
T wave – ventricles repol
P wave
P wave – atrial depol – impulse from SA over atria to AV – atria contract a little after
QRS complex
QRS complex – ventricular depol – impulse spread to ventricles – contraction begins at R
T wave
T wave – ventricles repol
P-Q (PR) interval
P-Q (PR) interval – conduction time from beginning of atrial excite to beginning of ventricle excite – see delay from SA to AV
S-T
S-T – time when ventricles fibers fully depol – plateau phase of impulse – ventricles contract to pump blood
Cardiac Cycle
Cardiac Cycle
Systole – contraction
Diastole – relaxation
1. Relaxation (quiescent)
2. Atrial systole – atrial contracts
3. Atrial diastole – tricuspid and mitral valves close – ventricle fills
4. Ventricular systole – ventricle contracts
5. Ventricular diastole – atria and ventricle fill – AV delay
Heart Sounds
Lub – S1 – atrioventricular valves closing – after ventricular systole – ventricles fill with blood
Dub – S2 – semilunar valves closing – end of ventricular systole – ejected blood
Between each is ventricular systole
After S2 till S1 – ventricular diastole
Cardiac Output
Cardiac Output
CO = SV X HR – normal 5L/m
Cardiac Output (CO) – volume of blood ejected from each ventricle – separately – per minute
Left into aorta
Right into pulmonary trunk
Heart Rate (HR)
Heart Rate (HR) – how fast – beats per minute – influenced by:
ANS innervation
Sympathetic – increases
Parasympathetic – decreases
Endocrine
SV
Stroke Volume (SV)
Stroke Volume (SV) – how strong – volume of blood ejected by the ventricle each contraction – influenced by age, gender, fitness, duration of contraction
SV = EDV – ESV
Preload
Contractility
Afterload
EDV
EDV – end diastolic volume – end of rest – max fill of blood in the heart – 130ml
ESV
ESV – end systolic volume – remaining blood after contraction – 60ml
Preload
Preload – stretch of cardiac muscles at max filled w/ blood before contraction
Contractility
Contractility – force of ventricle contraction – availability of Ca creates contraction force
Positive Inotropic agents
Negative Inotropic agents
Positive Inotropic agents
Positive Inotropic agents – promote availability of Ca
Thyroid hormone
Norepinephrine
Negative Inotropic agents
Negative Inotropic agents – decrease availability of Ca
Electrolyte imbalance
Ca+ blockers
Afterload
Afterload – pressure to be exceeded to eject ventricular blood – measure of resistance against blood as it leaves heart
Frank-Starling – law of the heart
Frank-Starling – law of the heart
Greater preload = increase force of contraction during systole
Heart equalizes output of R & L ventricles to keep same volume in systemic and pulmonary circulation
Autonomic and Chemical Alteration of HR
Autonomic and Chemical Alteration of HR
Body changes HR to get homeostasis
Nervous control in Medulla Oblongata
Sympathetic impulses increase HR and force contraction – epinephrine, norepinephrine, thyroid hormones
Parasympathetic impulses decrease HR
Proprioceptors
Baroreceptors
Chemoreceptors
- Other factors: Ion balance – Na+, K+, & Ca+, Age, Gender, Fitness level, Temperature
Proprioceptors
Proprioceptors – in heart and pericardium
Give info about hearts position and movement
Control cardiac dynamic
Detect dilatation of heart – stretching
Baroreceptors
Baroreceptors – in vessels
Send signals to brain to adjust HR and dilate or constrict BV
Monitor blood pressure
Sense changes in stretch of blood vessel walls
Chemoreceptors
Chemoreceptors – carotid and aorta
Sense changes in blood chemistry – O2 levels, blood pH
Send signals to brain to regulate HR and breathing
Coronary artery disease
Coronary artery disease – build up in arteries – narrowing or blockage – fats, cholesterol, & etc
Myocardial ischemia
Myocardial ischemia – lack of oxygen to tissue due to blocked or reduced coronary arteries
Myocardial infarction
Myocardial infarction – Heart Attack – tissue lack oxygen and die – blood flow decreases or stops in coronary arteries
Atrial septal defect
Atrial septal defect – hole in septum wall that divides atria of heart – incorrect flow of blood
Tachycardia
Tachycardia – increase HR – above 100bpm
Bradycardia
Bradycardia – decrease HR – below 60bpm
