The document describes the structure and function of the human heart. It discusses the heart's location in the thorax, its layers, chambers, valves, blood supply and nerve innervation. It explains the cardiac cycle in detail, describing the different phases of ventricular systole and diastole. It also discusses the generation of the four heart sounds and their timing in the cardiac cycle.

1. BY ; NIKHIL VAISHNAV

2.  Every tissue in the body requires an adequate
supply of oxygen, nutrients and hormones .
 The waste products should be removed from
the tissue from time to time . These functions
are carried out by the blood .
 The blood is pumped out by the heart into
the Aorta from which is it distributed to all
parts of the body .

4.  It is a hollow muscular organ , which is
situated in the middle mediastinum in the
thorax . It lies between the two lungs and just
above the diaphragm.
 The heart is slightly larger than a clinched fist
.
 The heart measures about 12 x 9 cm. and
weighs about 300 gm. In males and 250 gm.
In females .
 The heart is a cone shaped organ.

5.  Anterior – Sternum , costal cartilage and ribs .
 Posterior – Esophagus , thoracic duct, Azygos
vein.
 Superior – superior vena cava,
 Inferior – diaphragm.
 Lateral-lungs

7.  Coverings of the heart – The wall of the heart consists of 3 layers .
 1. Endocardium . 2. Myocardium 3. Pericardium
1. Pericardium – It is a double wall sac around the heart composed of
–
I. A superficial fibrous pericardium .
II. A deep two layer serous pericardium .
a. The parietal layer lines the internal surface of the fibrous pericardium .
b. The visceral layer surface of the heart .
They are separated by the fluid filled pericardial cavity.
2. Myocardium – It is a middle muscular layer . It is the thickest layer and
forms the main mass of the heart . It is responsible for the contraction of the
heart .
3. Endocardium – It is the innermost layer of tissue that lines the
chambers of the heart . They are made up of epithelium tissue.

9.  The heart has a base , an apex and 3 surfaces –
sternocostal, the diaphragmatic, pulmonary surfaces .
It has 4 borders – right , left , sup. And inf.
 The base of the heart is located posteriorerly and is
formed mainly by the left atrium .
 The apex of the heart is formed by the left ventricle .
It is located posterior to the 5th left intercostals space
in adults .
 The sternocostal surface of the heart is mainly
formed by the right ventricle .
 The Diaphragmatic surface is formed by the both
ventricle.
 The pulmonary or the left surface of the heart is
formed mainly by the left ventricle.

10.  The heart has 4 chambers , 2 atria and 2
ventricles .
 The right atrium- It forms the right border of
the heart, between the SVC and IVC . It receives
venous blood from the superior and inferior vena
cava and coronary surface.
 The interatrial septum separates the right atrium
from the left atrium.
 The Sino- atrial node( S.A NODE) lies in the wall
of the right atrium . It is the natural pacemaker
of the heart.
 Tricuspid valve is located between the R.A and
L.A. .

11.  It is the largest part of the sternocostal
surface.
 There are numerous irregular muscle bundle ,
papillary muscles, within the ventricles. A
number of fibrous threads called chorda
tendineae.
 The right atrioventricular valve or tricuspid
valve guards the right atrioventricular orifice.
 The pulmonary valve consist of 3 Semilunar
cusps, guards the pulmonary orifice.

12.  It forms the base or posterior aspect of the
heart.
 Four pulmonary veins enter the posterior wall
of the left atrium.
 The bicuspid ( left atrioventricular valve ) is
located between the left atrium and the left
ventricle.

13.  It forms the apex of the heart
 The wall of left ventricle is twice as thick as
that of the right ventricle, because the left
ventricle performs more work than the .
 The left atrioventricular valve or Mitral valve
or bicuspid valve guards the left
atrioventricular orifice.
 The left ventricle is separated from the right
ventricle by a thick , interventricular septum .

14.  Arterial supply – The heart gets its nutrient and oxygen
from two arteries – The right and left coronary arteries .
 These are the first branches of aorta .
 The right and left coronary arteries are called “ coronary
“ because they encircle the base of the ventricle
somewhat like a crown
1. The Right coronary artery ( RCA) – It arises from the
right aortic sinus . Branches of right coronary artery
are –
A. Posterior Interventricular branch .
B. Marginal branch .
2 . The left coronary artery ( LCA) – It arises from the left
aortic sinus. Branches of left coronary artery are-
A. Anterior interventricular branch.
B. Circumflex branch .

16.  The walls of the heart are drained by veins
that empty into the coronary sinus .
 Tributaries of the Coronary sinus –
1. The Great Cardiac vein .
2. Middle cardiac vein .
3. Small cardiac vein
 Some venous blood of the heart drained by
anterior cardiac vein or Thebesian veins . It
opens directly into the right atrium.

17.  The heart is supplied by Autonomic nerve
fibers.
 Parasympathetic fibers are derived from both
vagus nerves . Sympathetic fibers are derived
from sympathetic trunks .
 Both these Fibers from a Network called the
Cardiac plexus.

19.  This system consists of specialized cardiac muscle cells,
that can initiate impulses and conduct them rapidly
through the heart .
 They co- ordinate the contractions of the 4 chambers of
the heart.
 Parts of conduction system –
1. The Sino- atrial or SA node – It is the “ Natural
pacemaker “ of the heart , because it initiates the
impulses for contraction.
2. The atrioventricular or AV node – It is located in the
interatrial septum.
3. The atrioventricular bundle – It is called Purkinje fibers.
This bundle lies in the interventricular septum .
4. Right and left branches of AV bundle - Within the
interventricular septum , the AV bundle divides into right
and left limbs and branches .

21.  1. TRICUSPID VALVE- Tricuspid valve or right
Atrioventricular valve is located between the right atrium
and right ventricle . It guards the right atrioventricular
orifice.
 2. BICUSPID VALVE- It is also known as mitral valve and
left atrioventricular valve . It is located between left atrium
and left ventricle of the heart . It has two tapered cusps . It
allows oxygenated blood from the left atrium to pass into
left ventricle .
 3. PULMONARY VALVE- The Pulmonary valve , consisting
of 3 semi lunar cusps, guards the pulmonary orifice . It lies
between the right ventricle and the pulmonary artery .
 4. AORTIC VALVE- It also has 3 semilunar cusps . It lies
between the left ventricle and the Aorta . It guards the
Aortic orifice .

22.  The Cardiovascular system is composed of two
circulatory paths ; The pulmonary circulation and
the Systemic Circulation .
 Systemic circulation – Systemic Circulation is the
movement of blood from the heart through the
body to provide oxygen and nutrients and
Bringing deoxygenated blood back to the heart .
 Pulmonary circulation – Pulmonary circulation is
the movement of blood from the heart to the
lungs for oxygenation then back to the heart
again .

23. HEART
AORTA
ARTERIE
S
ARTERIO
LES
CAPILLA
RIES
EXCHAN
GE OF
GASES
VENULES
VEINS
SVC AND
IVC

24.  The wall of each blood vessel contains 3
Concentric coats or Tunics –
1. The Tunica Intima – Innermost Layer.
2. The Tunica media – Middle layer .
3. The Tunica Adventitia- Outermost layer.
 THE TUNICA INTIMA –
It has the following layers
a. Inner Endothelial lining , made up of a single
layer of Simple Squamous epithelium .
b. Underlying Basal lamina.

25.  Cardiac muscle is Involuntary , Striated muscle that is
found in the heart only .
 They have a “ Synci-tium like appreance and cardiac
muscle fibers are connected at regular Intervals by
Intercalated disc .
 Cardiac muscle has One Centrally located Nucleus .
 PROPERTIES OF CARDIAC MUSCLES –
1. Excitability – Excitability is the Knack of Cardiac
cells to respond with A Suitable Amount of Stimuli.
2. Conductivity – Conductivity is the Ability of cardiac
cells to transfer the Action potential from cell to
cell.

26. 3. Contractility – Contractility is a cardiac
muscle cells ability to transform an
electrical signal into a mechanical action .
4. Auto- rhythmicity- Autorhythmicity is
property of Cardiac muscle cells to
generate impulses without the Involvement
of any nerve.
They do not need any Neural stimulation .

27.  RMP- The potential difference between inside and
outside of the cell under resting condition is
known as resting membrane potential .
 ACTION POTENTIAL- When the muscle is stimulated
a series of changes occurs in the membrane
potential which is called Action potential .
 Depolarization – When the impulse reaches the
muscles , The resting membrane potential is
Abolished . The interior of muscles becomes
positive and outside becomes Negative.
 Repolarization – Within a short time , the muscle
obtains The RMP once again . Interior of the
muscle becomes Negative and outside becomes
positive .
 The resting membrane potential of Cardiac
muscle is -90 mV .

28.  Depolarization Phase or Phase 0 – The Membrane
Potential Changes From -90 mV to + 20 mV . The
Initial rapid Depolarization is due to the opening of
voltage gated Na+ channel .
 Initial rapid Repolarisatipon or phase 1- This Phase is
due to Closure of Na+ channels.
 Plateau phase or Phase 2- This Phase is due to slower
but prolonged opening of voltage gated Ca+2
channels.
 Late Rapid Repolarization or phase 3- Closure of
Ca+2 channels is responsible for this phase.
 Phase 4 – This phase is due to opening of K+
channels .It causes K+ efflux. It is helpful for the
muscle to return back to RMP.

29. Definition- The Cardiac cycle refers to a
complete Heartbeat from its generation to the
beginning of the next beat.
OR
Cardiac cycle refers to one complete heartbeat ,
consisting one contraction and relaxation of
the heart.
 The contraction and relaxation of both the atria
of heart are called Atrial systole and atrial
diastole.
The contraction and relaxation of both ventricles
are called ventricular systole and diastole.

30.  SYSTOLE TIME(SECOND
1. Isometric contraction = 0.05
2. Ejection period = 0.22
Total = 0.27
 DIASTOLE
1.Protodiastole = 0.04
2. Isometric relaxation = 0.08
3. Rapid filling = 0.11
4. Slow filling = 0.19
5. Atrial Systole = 0.11
TOTAL O.53
Total duration of Cardiac cycle is 0.27+0.53=0.8
second .

31. 1. Isometric contraction period –
 This is the first phase of ventricular systole.
 Immediately after Atrial systole , The AV Valves are closed. The semi
lunar valves are already closed .
 There is no changes in the volume of ventricular chambers . It is also
called Isovolumetric contraction . Isometric contraction lasts for 0.05
seconds.
2. Ejection Period- Semilunar valves are opened. Ventricles Contracts and
the blood is Ejected out of both the ventricles .The duration of
Ejection period is 0.22 second.
3. Protodiastole-
 Since this is the First stage of Ventricular diastole, it is called
Protodiastole.
 Protodiastole Indicates only the end of systole and the beginning of
diastole.
 It lasts for 0.04 second.
 Due to ejection of blood , the pressure in the Aorta and pulmonary
artery increases and interventricular pressure decreases. So both
Semilunar valves are closed.

32. 4. Isometric Relaxation –
 All of the valves of heart are closed. Both the
ventricles relax.
 No any changes in volume or length of the muscle
fibers. This is also called Isovolumetric relaxation
period.
 Duration of Isometric Relaxation is 0.08 second.
5. Rapid Filling phase-
 When the pressure in the ventricles becomes less
than that in atria , the AV valves open .
 When AV valves are opened , There is a sudden rush
of blood into ventricle. So this period is called Rapid
Filling Period .
 About 70% of Filling Takes place during this stage.
 It lasts for 0.11 second.

33. 6. Slow filling Phase-
 After the sudden rush of blood, the
ventricular filling becomes slow now, it is
called Slow filling . It is also called Diastasis.
 About 20% of filling occurs in this phase.
 This phase lasts for 0.19 second .
7. Atrial Systole-
 After Slow filling period , the atria contract ,
A small amount of blood enters the
ventricles from the atria and the cycle is
repeated.
 The atrial Systole is also called the last rapid
filling phase.
 About 10% of Ventricular filling takes place
during this period .
 Duration of Atrial Systole is 0.11 second .

34.  INTRODUCTION-
 The Mechanical activities of the heart during each
cardiac cycle, produce some sounds , which are called
heart sounds.
 Some of the common mechanisms by which heart
sounds are generated include-
1.Opening or Closure of the heart valves.
2.Flow of blood through the valve orifice.
3. Flow of blood into the ventricular chambers.
4. Rubbing of cardiac surfaces.
 The Heart Sounds Can be heard by placing the ear
over the chest or by using a Stethoscope or
microphone. These Sounds can also be recorded
graphically.

35.  Four heart sounds are produced during each
Cardiac cycle. The First and second heart
sounds are more prominent and resemble the
spoken words ‘LUBB’ and ‘DUBB’ respectively.
 The third heart sound is a mild sound
 The fourth heart sound is an inaudible sound.

36.  FIRST HEART SOUND-
 The first heart sound is produced mainly due
to sudden closure of atrioventricular valves.
 It is produced during isometric contraction
and earlier part of ejection period.
 The first heart sound is a long, soft and low
pitched sound .it resembles the spoken word
‘LUBB’ .
 The duration of this sound is 0.10 to 0.17
second.
 It can be heard by using the stethoscope.

37.  The second heart sound is produced due to
simultaneous closure of both the Semilunar
valves.
 The second heart sound is a short, sharp and
high pitched sound.
 It resembles the spoken word ‘ DUBB’
.Duration of second heart sound is 0.10 to 0.
14 second.
 It is produced during the Prodiastole and part
of isometric relaxation phase.

38.  The Third heart sound is produced due
to the vibrations set up in ventricular
wall, when blood rushes into ventricles
during rapid filling stage.
 Third heart sound is a short and low
pitched sound . The duration of third
heart sound is 0.07 to 0.10 second .
 It can be heard only using microphone.
 It occurs during rapid filling phase.

39.  Fourth heart sound is produced due to the
atrial systole. It is caused by Contraction of
atrial Musculature.
 It is a short and low pitched sound . Duration
of fourth heart sound is 0.02 to 0.04 second .
 It is an Inaudible sound . It is studied only by
Graphical recording that is by
Phonocardiography.

40.  DEFINITION- Cardiac output is the volume of blood pumped by
the heart per minute( mL blood/ minute.
 Cardiac output is the most important factor in Cardiovascular
system ,Because, the rate of blood flow through different parts of
the body depends upon the Cardiac output
 Cardiac output =
Heart rate x Stroke volume
Generally Heart rate 72 beat per minute and stroke volume is 70
mL per minute . So Cardiac output –
72 x 70 = 5040 mL per minute.
So Average Cardiac output is 5 Liter per minute.
 Stroke Volume- The Stroke volume is defined as the amount of
blood pumped out by each ventricle per heart beat. Average
value is 70 ml/ min . Normal range is 55- 100 ml/ min .
 Stroke volume( SV) =
End diastolic volume( EDV) – End systolic volume( ESV)

41.  End diastolic volume(EDV)- It is the volume of blood
remaining at the end of ventricular diastole. Normal value
is 120 ml.
 End systolic volume(ESV) – It is the volume of blood
remaining at the end of ventricular systole. Normal value is
50 ml.
 So Stroke volume- 120 – 50= 70 ml/ minute.
 Ejection fraction- It is the fraction of blood pumped out of
a ventricle in a heart beat.
Normal range= 55-70 % .
EF= SVEDV X 100= 70/ 120 X 100
 Cardiac index- It is defined as amount of blood pumped
out of ventricle per minute per square meter of body
surface area. Normal value is 2.8 liters / minute/ one
square meter of body surface area. The body surface area
of a normal adult is 1.734 square meter.

42.  PHYSIOLOGICAL-
1. Exercise- During Exercise CO is increased.
2. After food intake it is increased.
3. Emotions like excitement, anxiety, etc. increase
cardiac output.
4. A high environmental temperature can increase
cardiac output.
5. Pregnancy- During the later months of
pregnancy cardiac output is increased.
 PATHOLOGICAL-
Cardiac output is increased in fever,anemia and
Hyperthyroidism. It is decreased in
Hypothyroidism, Shock, Hemorrhage and
Cardiac Failure.

43. 1. VENOUS RETURN- Venous blood is the quantity
of blood flowing from veins into the right
atrium per minute. When the venous blood
increases, cardiac output also rises.
2. FORCE OF CONTRACTION- Increase in the force
of contraction of the ventricles increases the
stroke volume and cardiac output. Sympathetic
stimulation increases the force of contraction
and Parasympathetic( vagus nerve) stimulation
decreases the force of contraction.
3. HEART RATE- Within the physiological limits, an
increase in heart rate increases the cardiac
output.
4. PERIPHERAL RESISTANCE- It is the resistance or
load offered by the blood vessels to the flow of
blood. When peripheral resistance is more
cardiac output is reduced.