Mediastinum: pl. Mediastina 1. A septum or cavity between two principal portions of an organ. 2. The mass of organs and tissues separating the lungs. It contains the heart and its large vessels, trachea, esophagus, thymus, lymph nodes, and connective tissue.
Right atrium tricuspid valve right ventricle Right ventricle pulmonary semilunar valve pulmonary arteries lungs Lungs pulmonary veins left atrium Left atrium bicuspid valve left ventricle Left ventricle aortic semilunar valve aorta Aorta systemic circulation
Cardiovascular System (CVS)
The central blood pumping organ that
receives & pumps out blood to the whole
Position: In middle mediastinum in between
the two lungs, behind body of sternum,
about 1/3rd of it is on the right side &2/3rd are
on the left side of the body
Superficial Anatomy of the Heart
Inside heart there are
Four openings, guarded by
Right & Left Atrium are receiving chambers
Right & Left Ventricle are distributing chambers
Openings of Heart
Right atrio-ventricular opening
Left atrio-ventricularLeft atrio-ventricular
3. Aortic opening
4. Pulmonary opening
Valves of Heart
There are four valves:
1. Right atrioventricular
2. Left atrioventricular valve
3. Pulmonary valve
4. Aoritc valve
Heart valves ensure unidirectional blood flow through the
Atrio-ventricular (AV) valves lie between the atria and the
AV valves prevent backflow into the atria when ventricles
Aortic semilunar valve lies between the left ventricle and
the aorta .
Pulmonary semilunar valve lies between the right ventricle
and pulmonary trunk.
Semilunar valves prevent backflow of blood into the
Functions of Valves
• Maintain unidirectional flow of blood
• Prevent backflow
• Produce heart sound
• Cardiac muscle fibers are striated –
sarcomere is the functional unit
• Fibers are branched; connect to one
another at intercalated discs. The
discs contain several gap junctions
• Nuclei are centrally located
• Abundant mitochondria
• SR is less abundant than in skeletal
muscle, but greater in density than
• Sarcolemma has specialized ion
channels that skeletal muscle does
not – voltage-gated Ca2+ channels
• Fibers are not anchored at ends;
allows for greater sarcomere
shortening and lengthening
Major Types of Cardiac Muscle
• Atrial Muscle
• Ventricular Muscle
• Specialized excitatory and conductive muscle
The AV Bundle
The left & right bundles of purkinje fibers
Heart Muscle: Cardiac Conduction System
• Specialized muscle cells “pace” the
rest of the heart; cells contain less
actin and myosin, are thin and pale
• Sinoatrial (SA) node; pace of about
• Internodal pathways connect SA
node to atrioventricular (AV) node
• AV node could act as a secondary
pacemaker; autorhythmic at about
• Bundle of His
• Left and right bundle branches
• Purkinje fibers; also autorhythmic at
about 45 bpm
Properties of Heart Muscle
Excitability & Contractility
All or none law
Frank Starling Law
Hollow tubes, which carry blood along with
oxygen, nutrients & metabolic waste
products within the body.
• Coronary circulation is the functional blood
supply to the heart muscle itself
• Collateral routes ensure blood delivery to heart
even if major vessels are occluded
Coronary Circulation: Arterial Supply
1. the right and left
2. marginal arteries
3. anterior and
4. the circumflex
Coronary Circulation: Venous Supply
• the great cardiac
• anterior and
• the middle
cardiac vein and
• the small cardiac
Importance of Circulation
• Supply oxygen, nutrients to tissue
• Carry away CO2 & waste products
• Prevent intravascular coagulation
• Thermal balance
• Cardiac output: The amount of blood that is
ejected by heart per minute.
• Stroke Volume: The amount of blood pumped out
by ventricles in each beat/contraction. It is about
• Heart rate: The number of contractions of heart
• Cardiac Output = Stroke Volume Heart rate
Abnormalities of Heart Rate
Tachycardia: Increased heart rate above the
upper normal physiological limit
Bradycardia: Decreased heart rate below
normal physiological limit
The rhythmic dilatation & elongation of arterial
wall by intermittent ejection of blood from heart
transmitted as a wave to the periphery.
• Heart rate is counted
• Few clinical condition can be recognized:
Hypertrophy, arrhythmia, Fibrillation etc.
• Myocardial Infarction: Acute ischaemic necrosis
of an area of heart muscle.
• Heart Block: Transmission of impulse through the
heart is blocked.
• Shock: Widespread hypo perfusion of tissue due to
reduction of blood volume or cardiac output is
• Angina Pectoris: Cardiac pain due to impaired
coronary blood flow.
It is the lateral pressure exerted by
blood on the vessel wall while
flowing through it.
BP is expressed as
systolic (during systole) and
diastolic (during diastole) blood pressure.
Normal BP in healthy adult:
Systolic: 120 ± 15 mm Hg
Dialstolic: 80 ±10 mm Hg
Blood pressure =
Cardiarc output × Peripheral resistance
• Peripheral resistance is the resistance of the
vessels to blood while passing within it.
Build & Posture
Persistent rise of blood pressure above normal
range in respect of age & sex.
• Essential Hypertension: 85 to 90%
• Secondary Hypertension: 10 to 15%
Stricture of Aorta
Drugs like oral contraceptives, steroids etc.
Receptors & Neurotransmitters
Receptors are substances, lipoprotein in nature,
present in the cell membrane or inside the cell, with
which neurotransmitters and drugs combine in
order to produce various effects.
Neurotransmitters are chemical substances
released from nerve terminals and acts on various
receptors to produce physiological effects.
The receptors of the sympathetic nervous systems
are called adrenergic receptors. Sympathetic
neurotransmitters like adrenaline and noradrenaline
stimulates these receptors.
There are mainly two types of adrenergic receptors:
α (alpha) and β (beta) receptors. They are further
subdivided into α1, α2, β1 and β2 receptors.
These receptors are found in heart, blood vessels,
kidney, pancreas, uterus and some other organs.
Drugs that are used to control hypertension are called
Antihypertensives are mainly of following groups:
• Alpha Blocker
• Beta Blocker
• Calcium Channel Blocker
• ACE inhibitor
• Angiotensin II antagonist
Diuretics promote the excretion of water
and electrolytes by the kidneys.These are
used either alone or in combination to
reduce blood pressure.
Classification of Diuretics:
1. Loop diuretics (high efficacy)
2. Thiazides (moderate efficacy)
3. K+ sparing diuretics (low efficacy)
Alpha Blocking drugs
Alpha (α) blockers block the α1 & α2 adrenoceptors.
Blockade of α1 receptor results in vasodilatation
leading to fall of blood pressure due to decrease in
Beta blockers block beta adrenergic receptor
and are used in the management of
cardiovascular disorder like hypertension,
angina pectoris , cardiac arrhythmia and
β1 and β2
β1, β2 and α1
Calcium Channel Blockers
Calcium Channel Blockers inhibit the influx
of calcium in vascular smooth muscle and
myocardial cells. This results in dilatation
of coronary and peripheral arteries &
CCB have no effect in venous tone.
Drugs used as calcium channel blockers are
• Lercanidipine etc.
Angiotensin II is a very potent vasoconstrictor.
ACE Inhibitors inhibit angiotensin converting
enzyme (ACE) thus preventing conversion of
Angiotensin I to Angiotensin II . This results in
vasodilation and fall of blood pressure.
Drugs used as ACE Inhibitors are:
Angiotensin II Receptor
These act mainly by selective blockade of
Angiotensin II receptors resulting in vasodilation
and fall of BP
Grading of Hypertension
Hypertension can be graded on the basis of
diastolic blood pressure.
90 to 105 mm Hg
105-120 mm Hg
>120 mm Hg
rising rapidly over 140 mm Hg
Treatment of Mild & Moderate
First line treatment (any one drug)
Particularly in the elderly
Thiazides are the drug of choice
2. Beta blockers
3. ACE inhibitors or Angiotensin II antagonists
can be used as alternative first line therapy, if the
above drugs are not tolerated
Sencond line treatment (addition of a 2nd drug)
• If first line therapy fails
• To minimize side effects
Logical combination of drugs:
First line drug
Treatment of Severe Hypertension
In case of severe hypertension or despite second
line therapy hypertension is not controlled, a third
drug, especially, Vasodilators is added with second
Treatment of Malignant
Emergency management is lowering diastolic
BP upto 100 mm Hg with Intravenous
Next management is as for severe hypertension.
If hypertension is associated with other disease:
Choice of drugs
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