Heart Flashcards
Where is the heart located?
- Heart rests on the diaphragm
- 2/3 of the heart lies to the left of the midline
- Located within the mediastinum
Where is the mediastinum?
Between the lungs, from 1st rib to diaphragm, from sternum to vertebral column
What does the mediastinum contain?
- Heart
- Ascending aorta
- SVC
- Trachea
- Main stem bronchi
- Esophagus
What is contained within the thoracic cavity?
contains 2 pleural cavities and the mediastinum
What is the pericardium?
- Membrane that surrounds and protects the heart
- Confines the heart to its position within the mediastinum while providing sufficient movement during vigorous contractions
What are the parts of the pericardium?
fibrous and serous pericardium
What is the fibrous pericardium? What does it attach to?
- attaches to the adventitial layers of the aorta, pulmonary trunk and SVC
- stabilizes position of heart and prevents overstretching
What is the serous pericardium?
- thinner, more delicate
- parietal layer -> pericardial fluid -> visceral layer
What is the CT ratio?
widest part of the heart/ widest part of the thorax = cardiac thoracic ratio
what CT ratio is normal?
less than 50%
what is a hole in the middle of a left lateral chest?
left main stem bronchus as it is fairly horizontal
What are the layers of the heart wall?
- epicardium
- myocardium
- endocardium
what is the epicardium?
visceral layer of serous pericardium
What is the myocardium?
95% of wall
- straited muscle - but not skeletal
What is the endocardium?
smooth inner layer
- continuous with the endothelial lining of the attached large blood vessels
What are the parts of the heart?
base, apex, 4 chambers and sulci
diagram - slide 18 of heart lecture
layers of heart wall - label
layers of pericardium and pericardial cavity
what is the base of the heart?
- SVC and IVC enter, and Ascending Aorta and Pulmonary Arteries/Trunk exit
- Towards right shoulder
- Formed by atria
what is the apex?
- tip of right and left ventricles
- points towards left hip
what are the 4 chambers of the heart?
2 atria
2 ventricles
what is the sulci?
- Separate the chambers
- Coronary vessels travel in the sulci
- Contains variable amount of fat
what are the 2 types of sulci?
coronary sulcus
inter ventricular sulci (2)
what is the coronary sulcus?
separates atria from ventricles
what are the interventricular sulci (2)?
- separates the ventricles
- anterior and posterior
use diagrams slide 22 and 23
understand atria and ventricles
coronary sinus
On an AP/PA chest you never see which atrium?
left
- you see the left auricle which sits on top of the left atrium
what is the coronary sinus?
enlarged vein
what is an auricle?
anterior surface of each atrium
increases capacity of atria
what is the structure of the right atrium?
- receives blood from SVC, IVC and coronary sinus (posterior surface)
- pectinate muscles - anterior surface
- fossa ovalis - remnant of foramen ovale
- tricuspid valve
where is the SVC bringing blood from?
upper extremities, head and neck
where is the IVC bringing blood from?
lower extremities, abdomen and thorax
What is the right ventricle?
- trabecular carneae
- chord tendineae
- pulmonary valve ( 3 cusps) -> pulmonary trunk -> right and left pulmonary arteries
What is the foramen ovale?
opening between right and left atrium in a fetus
where is the tricuspid valve located?
in the right atrium
what does the trabecular carneae form?
papillary muscles
what does the chord tendineae do?
attaches cusps of tricuspid valve to papillary muscles
where is the pulmonary valve located?
superior part of the right ventricle
what is the left atrium?
- receives blood from 4 pulmonary veins
- pectinate muscles are only in the auricle
- mitral valve - bicuspid valve
what is the left ventricle?
- same structures as the right ventricle
- 2 to 3 x’s thicker than the right ventricle
- aortic valve (3 cusps) -> aorta
which valve is more superior, tricuspid or pulmonary valve?
pulmonary valve
which valve is more superior, aortic valve or mitral valve?
aortic valve
Why is the left heart wall thicker?
the left side has much lower pressure than the right, and has to overcome this pressure
diagram slide 32 of heart lecture
understand where the parts of the heart are sitting
what is the most anterior heart structure?
right ventricle
what is the most poterior heart structure?
left atrium
**How much of the heart should be touching the body of the sternum?
1/3 if normal
if exceeding 1/3 enlarged right ventricle - right ventricular enlargement
which valves are more superior
Aortic and pulmonary are more superior than mitral and tricuspid valves
slide 36 diagram
mitral not bicuspid
how do the mitral and tricuspid valves work?
valves open
- cusps project into ventricle
- atria contract - ventricles are relaxed
- blood goes from high pressure to low pressure - from atria to ventricles
what happens to the mitral and tricuspid valves when ventricles contract?
- blood forces cusps together (closes)
- papillary muscles tighten - prevents cusps from entering into atria - prevents back flow of blood into atria
what is a murmur?
regurgitation, when the cusps close some blood leaks through
slide 40 diagram
study
semilunar valves (aortic and piulmonary)
- Each cusp attaches to the arterial wall
- Free borders project into the lumen of the artery
- Open into artery
- Prevent backflow into ventricle
blood flow through semilunar valves
Ventricles contract > blood flows into artery
Ventricles relax > blood flows back toward the heart > fills the free edge of the cusps > closes the valve
what is stenosis?
narrowing of the valves
what are insufficient or incompetent valves?
failure to completely close
why are the aortic and mitral valves replaced more commonly?
greater pressure on the left side than the right
pressure in the pulmonary trunk
20
**pressure in the aorta **
80
fetal heart
lungs are not functional - blood bypasses
foramen ovale - opening between atria, closes at birth to become fossa ovalis
ductus arteriosus - between pulmonary trunk and distal part of aortic arch - closes at birth to become ligament arteriosum
if either is open after birth, left to right shunt, pulmonary hypertension
PFO - patent foramen ovale
foramen ovale didn’t close
diagram slide 47
what they are demonstrating
heart position
- rotated to the left
- sits on an angle with the apex further to the left
what is levocardia?
means heart sits to the left side of the body
What is dextrocardia?
right sided heart
average size of adult heart
closed fist
right heart border
mostly right atrium
left heart border
left ventricle and some of left auricle
- slopes superiorly and medially from apex
when giving CPR which part of the heart are you pressing on?
right ventricle
diagram slide 50
know purple is left auricle not left atrium
why do we have sulci in the heart?
where coronary arteries pass through
what increases the area of the heart?
the auricles
what are the elements of the conduction system of the heart?
- contractile fibers
- autorhythmic fibers
what are contractile fibers?
- “working” fibers that cause contractions
- 99% of cardiac cells
what are auto rhythmic fibers?
- self-excitable
- generate action potentials that trigger contractions
- nodal cells
- 1% of cardiac cells
nodal cells and conducting cells
- SA node
- AV node
- AV bundle (Bundle of His)
- Right and Left bundles
- Purkinje fibers
What is the SA Node?
sinoatrial node
- pacemaker - sets the rate at about 100 beats/minute
- contains auto rhythmic fibers
** right atrial wall near opening of SVC **
What is the AV node?
Atrioventricular Node
** interatrial septum superior to the ventricles (near the centre of the heart) **
*slows the speed of travel of the action potentials
- smaller diameter fibers
- fewer gap junctions
SA Node Pacemaking
- normally discharges at a rate of 70-75 bpm during rest
- if SA node fails, pacemaker function shifts to AV node
- “ectopic pacemaker” fires more lowly than SA node
What does ECG stand for?
Electrocardiogram
What is an ECG?
- monitors the electric currents generated by the heart
- depolarization (contraction follows
- repolarization
- 3 deflection waves
what are the 3 deflection waves?
P wave - 0.08 sec
QRS wave - 0.08 sec
T wave - 0.16 sec
what is the p wave?
- depolarization of both atria
- impulse moves from SA node through atria
What is the QRS complex?
- depolarization of ventricles (specific path through the ventricular tissues)
- depolarization of atria is also occurring
- both occurrences are represented
What is the T wave?
- depolarization of ventricles
- myocardium of ventricles depolarizes in “reverse order”
average heart rate?
75 beats per min
average cardiac cycle?
0.8 sec
each cardiac cycle is?
diastole/systole of both atria and ventricles
atrial systole?
ventricles are in diastole
- lasts 0.1 sec
- blood flows from body to atria to ventricles
- AV valves are open; SL valves are closed
- Firing of SA node = atrial depolarization - P wave
- Atrial systole - pushes rest of blood into ventricles
what is bradycardia?
slow heart rate
**what percent of the ventricles are passively filled by the atrial systole?
70%
what is the end diastolic volume?
ventricles contain 130 mL at the end of diastole
ventricular systole
atria are in diastole
- lasts 0.3 sec
- ventricle depolarization - QRS wave
- ventricular contraction begins; AV valve closes (due to increased pressure)
- “isovolumetric contraction” - all valves are closed
- Ventricular ejection occurs when the pressure inside the ventricle is greater than the artery (SL valves are open)
what is the end systolic volume?
60 mL
ventricular diastole
- pressure decreases in ventricles - SL valves close
- pressure is eventually less in ventricles compared to atria
- AV valves open and blood flows from atria to ventricles (passively)
- Both atria and ventricles are in diastole - ventricles will be 70% full
what is stroke volume?
amount of blood pumped out of the heart each beat
SV = EDV - ESV
SV = 130 mL - 60 mL
SV = 70 mL
Slides 68-71
study for exam questions
what is ejection fraction?
EF = SV/EDV100
EF = 70/130100
EF = 53.8
what is normal ejection fraction?
between 50 and 70
what is considered heart failure for ejection fraction?
<40
what is cardiac output?
the amount of blood pumped out by each side of the heart in 1min
CO = HR*SV
CO = 75 bpm * 70 mL/b
CO = 5250 mL/min
CO = 5.25 L/min
what are the factors affecting stroke volume?
preload
contractility
afterload
what is preload?
degree of stretch on the heart before it contracts
What is contractility?
forcefulness of contraction
What is after load?
the pressure that must be exceeded before ejection of blood from the ventricles can occur
what is the Frank-Starling law (starling’s law)?
- Greater stretch or preload leads to a greater contraction (like a rubber band)
- Preload is proportional to the End-Diastolic Volume (EDV)
- Keeps the 2 ventricles in balance
what is EDV affected by?
- duration of ventricular diastole (filling time)
- venous return
Increased contractility?
- ANS - Sympathetic Division - epinephrine and norepinephrine
- Increased Ca++ levels
- Drugs from the adrenergic category
Decreased contractility?
- Calcium channel blockers
- Anoxia (decreased oxygen)
- Acidosis
**after load of right ventricle?
20 mmHg
**afterload of left ventricle?
80 mmHg
how does an increase in the after load change stroke volume?
a decrease
- hypertension
- atherosclerosis (plaque build up)
cardiac output
measuring actual stroke volume involves catheterization
changes in either SV or HR will have a direct effect on CO
Heart rate affected by?
- Recall that intrinsic rhythm of the heart is set by the cells of the SA node
- Heart rate may be modified by chemical (hormonal), neural influences, age, gender, physical fitness, and body temperature
nervous control of the heart by?
medulla oblongata
ANS
Chemoreceptors and baroreceptors
how does the medulla oblongata control heart rate?
contains the cardiovascular center
how does the ANS control heart rate?
- sympathetic
- parasympathetic and vagus nerve (acetylcholine)
how do the chemoreceptors and baroreceptors control heart rate?
- aortic arch
- carotid sinus (first part of internal Carotid A)
Chemical regulation of the heart?
Epinephrine and norepinephrine - From the adrenal glands
Exercise, stress, and excitement stimulates the release of more hormones - Increase both heart rate and strength of contraction
veins?
carry blood to the heart
arteries?
carry blood away from the heart
capillaries?
exchange vessles
pulmonary and systemic circulations
- circuits are arranged in series
- output of one becomes the input of the other
- starling’s law ensures the same volume of blood flows in each circuit
pulmonary circulation
- right side of the heart is the pump
- deoxygenated blood from the body is pumped out the pulmonary trunk to the pulmonary arteries
- oxygenated blood is returned to the left atrium via pulmonary veins (4)
systemic circulation
- Left side of the heart is the pump
- Oxygenated blood is pumped to the entire body
- Deoxygenated blood is returned to the right atrium
coronary circulation
- Supplies blood to the muscles of the heart
- When heart contracts…little blood flows in coronary arteries (squeezed shut)
- When heart relaxes…high blood pressure in aorta propels blood through the coronary arteries > capillaries > coronary veins>coronary sinus>right atrium
- Coronary arteries are the 1st arteries to come off the ascending aorta
left coronary artery
- left anterior descending artery
- circumflex branch
left anterior descending artery (LAD)
- Anterior interventricular sulcus
- Supplies oxygenated blood to walls of both ventricles
circumflex branch
- Coronary sulcus
- Supplies oxygenated blood to walls of the left ventricle and atrium
right coronary artery
- posterior descending artery (PDA)
- marginal branch
posterior descending artery (PDA)
- Posterior interventricular sulcus
- Supplies oxygenated blood to walls of both ventricles
Marginal branch
- coronary sulcus
- supplies oxygenated blood to the wall of the right ventricle
anastomoses
- many arterial collateral routes provide protection
What are the coronary veins
** all drain into coronary sinus ** to drain into posterior part of the heart into the right atrium
CABG
coronary artery bypass graft
- more commonly the left coronary arteries getting bypassed
