HEART
Feilong, MBBS,
MSc surg.
Bio heart
club 2022
Objectives
•
Describe the three tissue layers of the heart wall.
•
Compare the functions of the right and left chambers of the heart.
•
Name the valves at the entrance and exit of each ventricle.
•
Briefly describe blood circulation through the myocardium.
•
Briefly describe the cardiac cycle.
•
Name and locate the components of the heart’s conduction system.
•
Define and explain common variations in heart rate.
•
Explain the effects of the autonomic nervous system (ANS) on the heart.
•
Explain what produces each of the two normal heart sounds, and identify the usual cause of a
murmur.
•
Briefly describe five methods used to study the heart.
•
Describe six types of heart disease.
•
List at least 3 risk factors for coronary artery disease that cannot be modified.
•
List at least 4 risk factors for coronary artery disease that can be modified.
•
Describe three approaches to the treatment of heart disease.
•
Describe at least 3 changes that may occur in the heart with age.
INTRODUCTION*
• The heart is a roughly cone
shaped hollow muscular organ
• Position/location: the heart lies in
the thoracic cavity in the
mediastinum (the space between
two lungs)
• It lies obliquely little more to the
left that right and presents a base
above and apex below
ORGANS ASSOCIATED WITH THE HEART
Inferiorly
•The apex rests on the central tendon of the diaphragm
Superiorly
•
•
•
•
•
The great blood vessels
Aorta
superior vena cava
pulmonary artery
pulmonary veins
Posteriorly
•
•
•
•
•
•
•
The esophagus
Trachea
Left bronchus
Inferior right bronchus
Descending aorta
Vena cava
Thoracic vertebrae
Laterally
•The lungs: the left lung overlaps the left side of the heart
Anteriorly
•The sternum
What
What its
it ismade
madeofofand
andwhat
whatholds
holdsit*it
▪ Fibrous Pericardium
▪ Serous Pericardium
▪ Pericardial Cavity
▪ Epicardium
▪ Myocardium
▪ Endocardium
▪ Ventricle walls
Visible Body A& P Video 29.5 Heart
Wall
INTERIOR OF THE HEART
• The heart is divide into right and left sided
by the septum. This is a partition consisting
of myocardium covered by endocardium
• Each side is divided by an atrioventricular
valve into the upper atrium and the ventricle
below
• Atrioventricular valve: these are formed by
a double layer of endocardium
• Strengthen by fibrous tissue
Atrioventricular Valves
• AV Valves: The AV valve
on the right has three
flaps and is known as the
tricuspid valve, which
separates right atrium
and right ventricle
• The AV valve on the left
has two flaps and is
known as bicuspid valve
(aka mitral valve), which
separates left atrium
and left ventricle
4 4 Chambers of the Heart*
1. Right Atrium
2. Right ventricle
3. Left atrium
4. Left Ventricle
BLOOD FLOW THROUGH THE
HEART
• The two largest veins of the body, the
superior vena cava and inferior vena
cava empty their contents into the
right atrium
• This blood passes via the right
atrioventricular valve into right
ventricle and from there blood is
pumped out into the pulmonary artery
(the only artery in the body which
caries deoxygenated blood).
Blood Flow through the heart cont.
• At the opening of pulmonary artery
pulmonary valve is present which
prevents backflow of the blood into
right ventricle, it is also known as the
semi-lunar valve
• After leaving the heart the pulmonary
artery divides into left and right
pulmonary arteries, which carry the
blood to the lungs where the exchange
of gases takes place, carbon dioxide is
excreted and oxygen is absorbed
Blood Flow through the heart cont.
• After purification of blood in the lungs the two
pulmonary veins carry oxygenated blood back
to the left atrium
• Blood than passes through the left
atrioventricular valve (mitral valve aka bicuspid
valve) into the left ventricle and from there
blood Is pumped out into the aorta (the first
artery of general circulation)
• The opening of aorta is guarded by the aortic
valve. At the opening of aorta there are valve
present which is called as semilunar or aortic
valve
• It should be noted that both atria contract at the
same time and this followed by the
simultaneous contraction of both ventricles
Coronary Circulation*
CONDUCTIVE SYSTEM OF THE HEART
• Autorhythmicity: The heart posses
the property of generating its own
electrical impulse & beats
independently of the nervous or
hormonal control.
• It is with both sympathetic &
Parasympathetic autonomic nerve
fibers.
Components:
• SA NODE: sinoatrial node
• AV NODE: atrioventricular node
• AV bundle (bundle of his):
atrioventricular bundle
SA and AV Nodes
SA NODE: SINOATRIAL NODE
• This is small mass of specialized cells lies in the opening of the
superior vena cava
• The Sinoatrial cells generate these regular impulses because they are
electrically unstable
• This is also known as parameters
AV NODE: Atrioventricular node
• This is small mass of neuromuscular tissue that is situated in the wall of
the atrial septum near the atrioventricular valve
• Normally the AV node merely transmits the electrical signals from the
atria into ventricle
Bundle of His
Atrioventricular bundle (bundle of his)
• This mass of specialized fibers originates
from the AV node
• The AV node crosses the fibrous ring that
separates the atria and ventricles, then at
the upper end of the ventricular septum it
divides into right and left bundle branches
• Within the ventricular myocardium the
branches break up into the fibers known
as purkinje fibers, which supply the
electrical impulses into the apex of the
heart
Nerve Supply To the Heart
• Heart is influenced by the
autonomic, sympathetic &
parasympathetic nerves
originating in the cardiovascular
center in the medulla oblongata
• The vagus nerve: supplied
mainly by the SA node, AV
nodes & atrial muscles
Heart Rates and Variations*
❖Bradycardia: less than 60
bpm
❖Tachycardia: more than 100
bpm
❖Sinus arrhythmia: regular
variation associated with
breathing
❖Premature ventricular
contraction (PVC): extra beat
induced by Purkinje fibers
Cardiac Cycle*
❖Action potentials spread rapidly
through conducting cells in a
specific pattern.
❖The components
o Sinoatrial (SA) node
(pacemaker)
o
o
o
AV node
Bundle of His
Purkinje fibers (to ventricular
contracting cells)
Cardiac Output*
❖The volume of blood pumped
by the heart per minute
❖Calculation of cardiac output
o Stroke volume (SV): The
volume of blood pumped
by the heart per heartbeat
o
o
Heart rate (HR): The
number of heartbeats per
minute
CO = SV × HR
Heart Sounds
❖Normal
o S1 Lub: closure of AV valves
o S2 Dub: closure of semilunar
valves
▪
Murmur: abnormal sound
Commonly caused by birth defects
▪
Stenosis: narrowing of the
valve opening and can cause a
murmur
Cardiac Output*
❖ Heart rate set by SA node and
influenced by nervous and endocrine
systems.
o Autonomic nervous system (ANS)
⮚ The sympathetic nervous
system increases heart rate.
⮚ The parasympathetic system
(CN X) slows the heart rate.
o Endocrine system
⮚ Epinephrine and thyroxine
increase heart rate.
❖ Stroke volume is increased by the
sympathetic nervous system.
❖ Changes to Na, K, Ca can alter
heart function
Blood Pressure*
▪ Blood Pressure
▪ Systole
▪ Diastole
Genetic Conditions*
❖Atrial septal defect-ASD
❖Patent foramen ovale-PFO
❖Foramen ovale
❖Patent ductus arteriosus-PDA
❖Ventricular septal defect-VSD
❖Coarctation of the aorta-Coarc
❖All four defects: Tetralogy of Fallot
Heart Disease*
❖ Inflammation of a heart layer
o Endocarditis
o Myocarditis
o necrosis
o Pericarditis
❖ Abnormalities of heart rhythm
o Arrhythmia/dysrhythmia
o Flutter
o Defibrillator—on every code cart/portable AED (automated
external defibrillator)
o Heart block
❖ Valve disease
❖ Stenosis
❖ Insufficiency
Atherosclerosis=Coronary Artery
Disease (CAD)*
❖Plaque (not plague)
❖ Narrowing
❖ Can cause
❖ Occlusion=ischemia
❖
Lack of blood supply to the heart
❖Angina pectoris: moderate
ischemia (stable and unstable
types)
❖ Discomfort/pain associated with
ischemia
❖ More to come in Patho
Myocardial Infarction--MI
❖ Depends on extent and location of the damage
❖ Signs and symptoms
❖ Cardiopulmonary resuscitation (CPR)
❖ Defibrillation
o
Automated external defibrillator (AED)
❖ Thrombolytic drugs
❖ Surgical treatment
o
Angioplasty
o
Coronary artery bypass surgery-CABG
o
Pacemakers
o
VAD
❖ Supportive care
o
Morphine
o
Oxygen
What puts people at risk for MI?
Preventing CAD
❖ Regular physical examinations
❖ Minimize controllable risk factors
❖ Monitor markers of CAD
o C-reactive protein (CRP)
o Protein associated with inflammation
o High levels could be a warning sign
o Cholesterol levels
o HDL-”Good” cholesterol >60
o LDL-”Bad” cholesterol < 70
o Triglycerides-chemical form of how fats exist <150
o Total cholesterol-HDL+LDL+20% of triglyceride level
<200
Congestive Heart Failure
❖ Simply put—enlarged heart
❖ Can be on the left, right or both sides of
the heart
❖ Decreases stroke volume.
❖ Cardiac output is less than cardiac
input.
❖ Blood pools in the chambers,
stretching heart wall.
❖ Excess stretching damages muscle
fibers, further reducing stroke
volume.
❖ Blood will back up into either the
lungs or the body depending on
where the damage is.
❖ Fluid accumulates in the lungs, liver,
abdomen (ascites), and legs (edema).
Interventions for Heart Disease
❖ Lifestyle changes
❖ Medications
o Statins
o Anticoagulants
▪ Aspirin
▪ Warfarin
o Digitalis
o Slows and strengthens heart
contractions
o Beta-blockers
o Reduce stimulation of the heart
o Antiarrhythmic agents
o Regulate rhythm
o Slow calcium channel blockers
o Dilate vessels or regulate conduction
or control contractions
❖ Correct cardiac conduction dysfunction
o
Artificial pacemaker-regular assistance
o
Implantable cardioverter-defibrillator (ICD)-as
needed “jolt”
❖ Heart surgery
o
Coronary artery bypass graft (CABG)
o
o
o
o
o
o
o
o
o
take veins/arteries from different areas of
body
Typically leg
Angioplasty
balloon
Coronary atherectomy
Cut or remove the plaque
Cardiac ablation
Laser beam/microwave to destroy the area
of bad signals
Surgical transplantation
Surgical Interventions
Coronary Angioplasty
Aging and the Heart
❖Heart chambers become smaller.
❖Myocardial tissue atrophies.
❖Less flexible valves.
❖Less responsive conduction system.
o Abnormal rhythms
❖Decreases contraction strength.
❖Decreased cardiac output.
Deeper Dive on your own….
▪
Overall heart with crash course roughly 10 min: https://youtu.be/X9ZZ6tcxArI