Download Cardiovascular system

Disha .J. Parikh
M.Pharm (Pharmacology)
Cardiovascular system is divided into two main parts:
Circulatory system: consisting of heart, which pumps the blood and the
blood vessels which circulates the blood.
Lymphatic system: consisting of lymph nodes and lymph vessels through
which the colorless lymph flows.
The heart pumps the blood into two separate systems:
- pulmonary circulation
- systemic circulation
The right side of the heart is involved in pulmonary circulation where CO2
leaves the blood and enters the lung and O2 leaves the lung and enters the
blood.
The left side of heart is involved in systemic circulation which supplies to
rest of the body, where tissue waste are passed in blood for excretion and
body cells extracts the nutrition and O2.
The heart is roughly cone-shaped hollow muscular organ, which is about the size of
the owner’s fist.
POSITION:
• It lies in the thoracic cavity in the mediastinum (space between the two lungs).
• It lies obliquely a little more toward left with the base above and apex below.
• The apex is about 9 cm to left of the midline at the level of 5th intercostal
space.
ORGANS ASSOCIATED:
Inferiorly: apex rest on the diaphragm.
Superiorly: aorta, superior vena cava, pulmonary artery and pulmonary vein.
Posteriorly: oesophagus, trachea, left and right bronchus, descending aorta,
inferior vena cava, thoracic vertebrae.
Laterally: the lungs- the left lung overlaps the left side of the heart
Anteriorly: sternum, ribs and intercostal muscles.
COVERINGS OF THE HEART:
Pericardium – a double-walled sac
around the heart composed of:
1.
A superficial fibrous
pericardium
2.
A deep two-layer serous
pericardium
a.
The parietal layer lines
the internal surface of
the fibrous pericardium
b. The visceral layer or
epicardium lines the
surface of the heart
They are separated by the
fluid-filled pericardial
cavity
The Function of the Pericardium:
Protects and anchors the heart
Prevents overfilling of the heart
with blood
Allows for the heart to work in a
relatively friction-free
environment
Myocardium – cardiac muscle layer forming the bulk of the heart.
Endocardium – endothelial layer which lines the chambers of the heart.
It consist of flattened epithelial cells and continues with the endothelial
linings of the blood vessels.
INTERIOR OF THE HEART
BLOOD FLOW THROUGH HEART AND LUNGS
• 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
Ductus arteriosus:
• It is cord like structure between arch of aorta and pulmonary trunk passing
underneath the aorta.
• During foetal life it works as the link between the two vessels to by-pass the
pulmonary circulation.
• After the birth the blood changes the route and starts circualting through the
lungs and therefore the link gets closed
• In rare cases the duct may remain open and the deoxygenated blood may mix
with the oxygenated blood of aorta.
• It can be corrected by surgery.
Septum ovale:
• The atria are seperated by the septum called as inter-atrial septum and the
ventricals are seperated inter-ventrical septum.
• The foramen ovale is the small opening at the inter-atrial septum which
remained open during the foetal life to avoid the blood circulate in the lungs.
• After the birth, with the first breath the foramen ovale gets closed which is then
called as septum ovale.
• In rare case it remains open after the birth which can be corrected surgically.
Blood vessels:
Arteries:
• Vessels which carry blood from heart to body parts.
• Usually carry oxygenated blood except pulmonary arteies which carries
deoxygenated blood.
• The arteries divide into arteriols and the finally into capillaries.
Veins:
• Brings the blood from various parts of the body into the heart.
• Usually carries deoxygenated blood except pulmonary veins which brings the
oxygenated blood into the left atrium
• The veins divide to form venules and finally venous capillaries.
Histology of blood vessels:
Consist of 3 layers:
• Tunica externa/ adventitia (elastic layer)
• Tunica media (muscular layer)
• Tunica intima (serous layer)
Tunica externa: made up of areolar connective tissue. Thicker in veins than in
arteries.
Tunica media: made up of smooth muscle fibres. Thicker in artery than in veins.
Tunica intima: made up of endothelial cells.
The lumen in the artery is wide open than in vein.
BLOOD CIRCULATION
Systemic circulation:
Arterial system
Venous system
Pulmonary circulation:
Coronary circulation:
PROPERTIES OF CARDIAC MUSCLES
Excitability or irritability:
Property of a tissue to respond to a stimulus.
Contractibility:
Property to contract in response to a stimulus.
Automaticity:
Property of cardiac muscle to generate its own impulse. The SA-node initiates the
impulse which is conducted to whole heart by other junctional tissues.
The property of conducting the impulse is known as conductivity. Although the
impulse in the heart comes through junctional tissue, each part of cardiac muscle can
generate its own impulse.
Rhythmicity:
Heart beats in a regular fashion as a result of its automaticity and conductivity. The
atria and ventricals alternatively produce contraction and relaxation at a perticualr
rate i.e. 70-80 beats/min. This is called as rhythmicity.
All or none phenomenon:
Either it contracts to its maximum ability or it does not contract at all. This rule is
applicable to whole heart.
Refractory period:
Period at which the heart does not respond to the external stimuli. It has two
phases
• Absolute refractory period: it is the period during systol when heart do not
respond to any stimuli however strong it be.
• Relative refractory period: it is during diastole , a strong extra stimulus can
provoke a response.
During the refractory period the heart gets time to recover and overcome fatigue.
Tonicity:
The special feature of the cardiac muscle to exert certain amount of pressure on
the blood it contains.
Nutrition of cardiac muscle:
ATP: Cardiac muscles gets its energy in form of ATP by glycolysis and mostly by
oxidation of glucose, free fatty acids and amino acids.
Oxygen: it is the most imp. Gaseous nutrition that regulates the oxidative process
for cardiac energy. Lack of O2 cause hypoxia followed by anoxia which is painful.
Sodium ion: it initiates and maintains the beat.
Calcium ion: it strengthens the systole and inhibits the diastole. Excessive Ca+2
stops the heart at systole
Potassium ion: it inhibits the contraction and prolongs the relaxation, i.e.
diastole. Excessive K+ stops the heart at diastole.
JUNCTIONAL TISSUES
These are the specialized tissues that generate and conduct the impulse.
•
•
•
•
•
Sino- atrial node (SA-node)
Atrio- ventricular node (AV-node)
Atrio- ventricular bundle (AVB) or bundle of His
Right and left branches of AVB
Purkinjee fibres (PF)
CARDIAC CYCLE
• It is the sequence of the events during one cardiac beat
• On an average hearts beats 72 times in a minute, hence it takes 0.8 sec for one
beat
• Both atria and ventricle goes systolic and diastolic phase with every beat.
Atrial events:
• Includes atrial systole and diastole.
• Systole occurs for 0.1 sec where atria contract to pour the blood in the
ventricals which is followed by diastole for 0.7 sec where atria relax and blood
from superior and inferior vena cava fill right atrium and blood from pulmonary
veins fills the left atrium.
Ventricular events:
After the atrial systole the ventricular systole starts which continues for 0.3 sec
followed by diastole for 0.5 sec
Isometric ventricular contraction period:
• At the start of the ventricular systole AV valve of the ventricles gets closed
(first heart sound).
• As s result the ventricles form the close cavities and the pressure inside rises
without decreasing the volume. This is isometric contraction period.
The onset is marked by closure of AV- valves and terminated by opening of the SLvalves (0.05 sec). Intraventricular pressure is highest.
Rapid and slow ejection period:
• After 0.05 sec the SL valves gets opened and the blood is ejected to the respected
arteries. This is rapid ejection period (0.15 sec)
• The intraventricular pressure starts rising but the volume steps down
• In the late phase the pressure lowers and there is slow ejection (0.1 sec)
Prodiastolic and isometric relaxation period:
• The pulmonary artery and aorta recoil and the blood tries to rush back.
• There is sudden closure of the SL valve (second heart sound)
• The interval between the start of ventricle diastole and closure of SL (0.04 sec)
valve is called prodiastolic period.
• Next is isometric relaxation period (0.08 sec) where AV and SL valves are closed
and both the atria and ventricles are at diatole. Thus intra-ventricular pressure is
minimum and heart is relaxing.
Rapid and slow inflow period:
After the isometric relaxation the AV-valve opens and rapis inflow of the blood starts
as the ventricles are at diatole (third heart sound) (0.03 sec), followed by slow
inflow (0.2 sec) also called as diastasis.
When the ventricular diastole ends the atrial systole
starts which overlaps for 0.1 sec. Atria contracts and
rapid filling of ventricle stars (rapid inflow period)
(fourth heart sound).
ELECTROCARDIOGRAM (ECG)
The graphical record of electric changes occurring
during the cardiac cycle is known as electrocardiogram.
The instrument recording ECG is known as
electrocardiograph.
Pair of connection called as leads are used to measure
electrical activity of the heart.
2 types of leads:
• Bipolar limb leads/ standard leads
• Unipolar leads
The bipolar limb leads are obtained by placing two
electrodes on the extremities to record the electrical
activity of the heart facing them. These leads are:
Lead I: right arm and left arm
Lead II: right arm and left leg
Lead III: left arm and left leg
Unipolar leads are obtained by placing
the electrodes at the closer proximity of
the heart
2 types: unipolar limb lead and unipolar
chest leads.
Unipolar limb leads :
Lead aVR: right arm lead
Lead aVL: left arm lead
Lead a VF: left leg lead
Unipolar chest leads:
V1:
V2:
V3:
V4:
V5:
V6:
4th inter-coastal space, right sternal boarder
4th inter-coastal space, left sternal boarder
between V2 and V4
5th inter-coastal space in mid clavicular line
5th inter-coastal space in anterior axillary line
mid axillary line at a level of V4.
NORMAL ECG:
Impulse originate from the SA node which is not observed. When it reach the atrial
musculature (0.04 sec) potential rises by 0.2mV (P wave). Followed by repolarization
Now the impulse from AV node to bundle of His and pirkinjee fiber. No deflection so
isoelectric line is obtained. When impulse reach intermuscular septum-negative
deflection (Q wave). Impulse immediately spreads to ventricular musculature, big
wave of 1.8mV (R wave). After these there is ventricular repolarization of 0.4 mV (T
wave)
CARDIAC OUTPUT:
The amount of blood pumped by the heart in one beat is called as stroke volume
(SV).
Now the heart rate (HR) is 70 beats per minute, so cardiac output (CO)is :
CO= SV X HR
The amount of blood pumped out by the heart in one minute is called as minute
output of the heart
Factors controlling the CO:
• Venous return: quantity of blood reaching the heart via superior and inferior
vena cava.
• Force of contraction of heart (inotropic action)
• Frequency of heart beats (chronotropic action)
• Peripheral resistance
CO varies with age, sex, surface area, exercise, posture.
CO increases with: pregnancy, anxiety, anger, hyperthyroidism, anemia, angina
pectoris.
CO reduces with: tachycardia, auricular fibrillation, A-V block, hemorrhage,
myxedema, surgical shock, pneumothorax, arterial hypertension and postoperative
conditions.
HEART RATE
Diff. phases of life
Heart rate (beats/ min)
foetus
140-150
children
100-110
Adult
70-80
old
65-75
Factors affecting the heart rate:
• Autonomic nervous system:
The sympathetic nerves increases force and frequency hence known as cardio
accelerator mechanism. The parasympathetic nerves decreases the heart rate.
• Higher centers of the brain:
Excitement increases and shock decreases the HR
• Respiration:
Inspiration increases and expiration decreases the HR
Reflex stimulation:
Stimulation with pain, cold or heat increases, however severe pain decreases the
HR
• O2 supply:
Anoxia increase the HR but if there is no O2 supply the heart may stop
• CO2 supply:
Moderate CO2 increases while high CO2 decreases the HR and may poison the heart
• Blood Pressure:
Increase in BP decrease the HR
• Temperature:
Every degree rise in the temperature increases the HR by 10 beats/min
• Exercise:
It increases the HR as well as force
• Drugs:
Adrenaline and thyroxine increases the HR and force of contraction. Digitalis
decreases the rate, but increases the force and hence increase CO.
Definition:
• The pressure exerted by the blood on the walls of the blood vessels.
• May be regarded as
1. Arterial B.P.
2. Venous B.P.
3. Capillary B.P.
The phases of the blood pressure are
• Systolic B.P: max pressure during the systole of the heart
• Diastolic B.P: min pressure during the diastole of the heart
• Pulse pressure: diff. between systolic and diastolic pressure
Normal range of
B.P. (mmHg)
Standard B.P.
(mmHg)
SP
110-145
125
DP
70-90
80
PP
40-55
40
Significance of BP:
Systolic pressure:
• It indicates the force with which the heart works.
• It is highly variable
• Increases with excitement, exercise, meals and decreases with shock, sleep, rest
etc.
Diastolic pressure:
• It indicates the extent of peripheral resistance (peripheral resistance that heart
has to withstand)
• It is generally constant
• Variations in diastolic pressure are of great clinical importance
Pulse pressure:
• It indicates the strength of stroke volume of cardiac output.
• Does not have any clinical significance
Methods of B.P. measurement:
It is commonly measured by sphygmomanometer
Two methods for the measurement of B.P:
• Palpatory method
• Ausclatory method
Palpatory method:
• The cuff is tied at the lower part of upper
arm.
• The arterial pulse at the wrist is felt
• BP is raised upto 200mmHg till pulse stops
• The bulb is unscrewed and pressure is
lowered till reappearance of the pulse
• The reading in the sphygmomanometer is
recorded when the pulse reappears
• It gives the systolic pressure.
Ausulatory method:
• The cuff is tied and the pressure is raised up to 200 mmHg.
• The stethoscope is placed in cubital fossa at the bifurcation of the brachial
artery
• The first sound heard at lowering of the pressure indicates the systolic pressure
• Now the pressure is further lowered , the disappearance of the sound indicates
the diastolic pressure.
Factors maintaining B.P:
Heart:
The force and frequency of the heart affects the pumping of the heart which indeed
maintains the B.P.
Cardiac output:
Depends on the venous return and pumping capacity of the heart.
Peripheral resistance:
It is governed by the elasticity and lumen of the blood vessels as well as the velocity
and viscosity of the blood. The peripheral resistance maintains the diastolic blood
pressure.
Blood volume:
Total circulating blood also affects the B.P. the increase in the volume raise where as
decrease in volume lower the pressure
Vasomotor center:
Situated in medulla oblongata
It receives the information about the pressure through baroreceptors and
chemoreceptors
Baroreceptors are found at the arch of aorta and at the base of the bifurcation of each
common carotid artery (carotid sinus).
Chemoreceptors are found at the aortic body (the nodule present at the lower part of
the arch of aorta) and carotid body (nodule present on occipital artery)
Baroreceptors are sensitive to decrease in BP, where as chemorecetors are sensitive
to increase in CO2 or decrease in O2 supply.
The impulse from the carotid sinus and carotid body are taken to vasomotor centres
through IX cranial nerves (glossopharyngeal nerve)
The X cranial nerve (vagus nerve) carry the impulse from aortic arch and aortic body
Vasomotor centers:
Medulla oblongata have two centers – pressor and depressor
Pressor center stimulates of sympathetic nerve and cause vasoconstriction
Depressor center decrease the activity of the sympathetic nerve and inhibit the
pressor center.
Thus when there is fall in BP the baroreceptors and chemoreceptors are stimulated
and they increase the activity of the pressor center
If BP is high, the depressor center inhibits the pressor center to inhibit the
sympathetic nerve and produce vasoconstriction.
Physiological variations:
The physiological variation occur for systolic pressure only.
For the change in diastolic pressure one must seek medical treatment.
Diastolic BP<90 is called mild hypertensive
Diastolic BP<100 is called clinical hypertensive
Age:
Phases of life
Systolic BP (mmHg)
Infancy
70-90
Childhood
90-110
Puberty
110-120
Adult
120-130
Old age
140-150
Body built:
Over weight have a tendency to have higher BP. As well as its is hereditary in nature
Climate:
BP is higher in cold climate than in hot
Diurnal:
BP is max in day, low in morning and lowest during sleep at night
Excitement and shock:
BP increases with excitement and decreases with the shock
Food:
Small rise in BP after meals
Gravity:
Standing> sitting> lying
Hormones:
Adrenaline secreted from adrenal medulla increases the BP by increasing CO and
vasoconstriction
Adrenal cortex secretes glucocorticoids and aldosterone which cause fluid and salt
retention and hence increase the BP.
Thyroxin (thyroid gland) and renin- angiotensin (kidney) also increase blood pressure.
Sleep:
BP is 10-15 mmHg less during sleep
Sex:
Women have slightly lower BP than men.
Renin angiotensin system:
Renin is secreated from the juxtaglomerular cells of kidney found in afferent
arterioles and distal tubules.
Secreted in response to decrease in renal perfusion pressure, mechanical stress,
hypoglycemia, exercise, emotional stress.
Actions of Angiotensin-II:
• Rapid increase in BP due to altered peripheral resistance
• Slow pressure response due to altered renal function
• Vascular and cardiac hypertrophy due to altered cardiovascular structure.
The altered peripheral resistance occurs due to direct vasoconstriction, enhanced
sympathetic- noradrenergic transmission leading to raise in BP
Angiotensin-II also cause increase in Na+ reabsorption from proximal tubules, relase
of aldosterone from adrenal cortex and constriction of renal blood vessels. Thus
produce sustained rise in BP
Besides Angiotensin-II by acting on the AT-1 receptors also cause increase in growth
factors thereby causing cardiac hypertrophy and hyperplasia leading to cardiac
remodeling.
VASCULAR DISORDERS
Hypertension:
It is chronic increase in arterial blood pressure.
Hypertension
diastolic pressure >90mmHg
Systolic pressure >150mmHg
2 types :
Primary hypertension:
Not link to a single aetiology. It may be due to stess, high fat diet, high sodium diet,
etc. the exact cause is unknown. Also called as ‘Essential Hypertension’
Secondary hypertension:
Condition secondary to some disorder.
May be associated with disorder like pheochromocytoma, Cushing syndrome,
primary aldosteronism, hyperthyroidism, myxoedema, renal vascular disorder, etc.
Hypotension:
It is decrease in arterial blood pressure where systolic BP< 100 mmHg and diastolic<
60mmHg.
Chronic in nature and often associated with weak and thin anemic patients.
Postural hypotension:
When a subject changes the posture from lying down to upright position there is
momentary hypotension due to the gravitational pull of the blood to lower
extremities. As a result there is reflux rise in blood pressure.
Thus lowwering of BP due to change in the posture is called as postural hypotension.
Ischemia:
It is temporary sudden loss of blood supply to a particualr part of body, leading to
partial damage to that part due to lack of oxygen supply.
If it is in the heart it is cardiac ischemia.
Aneurysm:
Bulging of the artery due to weakness of the arterial wall or increased pressure or
both.
In relation to aorta it is aortic aneurysm.
Arteriosclerosis:
Hardening and narrowing of the arteries due to fatty deposits resulting in the
decreased blood supply to that part.
In case of brain it is called as cerebral arteriosclerosis.
Peripheral vascular diseases:
It is obliterate disease of arteries of the limbs leading to the functional disorder of
small peripheral vessels.
Thrombosis:
Process of formation of solid clot during the circulation. The solid clot is called as
thrombus. It is usually initiated by platelet aggregation and mainly composed of fibrin.
If formed in vein it is called as venous thrombosis and in case of artery -arterial
thrombosis.
Arterial thrombosis is dangerous if it is coronary, cerebral or renal artery.
Embolism:
It is impaction of the embolus in the blood vessels.
An embolus is the sub transported from thrombus part of the circulation to another
part where it is impacted, cutting off the blood supply. Sometimes the hear
thrombosis may result in cerebral embolism.
Thrombo- angitis obliterans:
Adversely affects blood flow, characterized by acute inflammation with thrombosis
affecting both arteries and veins, following infection.
Raynaud’s disease:
Spasm of arteries and arterioles specially in digits, nose and tongue with intermittent
pallor or cyanosis. Often stops the functioning of the part.
Haemorrhage:
Escape of blood from artery ,vein or capillary. Dangerous if capillary hemorrhage in
brain is involved
Varicose – vein:
Abnormally dilated tortuous veins with incompetent valves.
It occurs frequently in lower extremities.
CARDIAC DISORDERS
Angina pectoris:
Clinical syndrome due to myocardial ischemia producing the sensation of chest pain,
pressure or strangling sensation. May characterize due to exertion.
Myocardial infraction:
It is ischemic type of myocardial necrosis resulting from abrupt reduction in coronary
blood flow. It id more intense and prolonged than angina pectoris. The pain is the
warning cry of heart for oxygen.
Congestive cardiac failure (CCF):
Decreased force of contraction of the heart leading to the inadequate cardiac output,
resulting in diminished blood flow to the tissues and congestion of pulmonary and
systemic circulation. Characterized by progressive breathlessness on exertion. Also
cause edema and enlargement of the orangs thus decreasing their efficiency.
Heart failure:
Condition in heart is unable to function adequately to supply the metabolic needs of
the peripheral tissues. Primary dysfunction occurs in left or right ventricle.
Left ventricular failure can occurs due to due hypertension, ischemic heart disease
etc. The common cause of right ventricular failure is left ventricular failure.
Cardiac arrhythmias:
It is the disorder of origin, rate, rhythm, conduction and spread of impulse in the
heart.
Tachycardia: increase in hear rate
Bradycardia: decrease in heart rate
Palpitation: continuous and fast beating of the heart
Extrasystole: the premature beat that occurs before the next expected beat. This may
be atrial, ventricular or nodal depending on the sight of origin.
Paroxysmal supraventricaular tachycardia: it is condition in which the heart rate
suddenly rise 150-200 beats/min.
Atrial flutter: rapid and but regular beating of atria at a rate 240-400 beats/min
Atrial fibrillation: rapid , irregular continuous, chaotic beating of atria. More
dangerous
Ventricular fibrillation: it is rapid irregular and chaotic beating of ventricles. There
is disorganized spread of impulse throughout the ventricles
Heart block: condition in which the nerve impulse are delayed of failed to get
through from their source in the right atrium and ventricle. It is obstruction in
conduction of impulse in the heart leading to decrease in heart rate and pulse rate.