Human heart anatomy and physiology Part -1

HUMAN HEART
ANATOMY AND PHYSIOLOGY

INTRODUCTION TO THE CIRCULATORY SYSTEM
 BLOOD
 Is a fluid connective tissue a specialized body fluid
 Blood is a mixture of about 55 percent plasma and
45 percent blood cells
 About 7 to 8 percent of total body weight is blood
 It has four main components
Plasma Red blood cells
White blood cells Platelets
 Functions
 Transport oxygen and nutrients to the lungs and tissues
 Form blood clots to prevent excess blood loss
 Carry cells and antibodies that fight infection
 Bring waste products to the kidneys and liver to filter
blood
 Regulate body temperature

 PLASMA
The liquid component of blood
 Mixture of water sugar fat protein and salts
 Transports blood cells throughout the body
 Besides nutrients waste products antibodies clotting proteins
 Chemical messengers such as hormones and proteins
 That help maintain body fluid balance
 RED BLOOD CELLS ( Erythrocytes)
 Bright red coloured cells
 The most abundant cell in the blood
 The shape of a red blood cell is a biconcave disc
(looks like a donut)

 Small size- Helps red blood cells pass through narrow
capillaries
 Flattened disc shape- Provides a large surface area, allowing
rapid diffusion of oxygen
 Contains special protein haemoglobin- It absorbs oxygen in
the lungs and releases oxygen in the rest of the body
 Does not contain a nucleus-Increases amount of space inside
the cell for haemoglobin
 Production of red blood cells is controlled by erythropoietin
( a hormone produced primarily by the kidneys)

 White Blood Cells (Leukocytes)
 White blood cells protect the body from infection
 Much fewer in number than red blood cells
(about 1 percent of blood)
 The most common type of white blood cell is the neutrophil
 Account for 55 to 70 percent of the total WBC count
 Each neutrophil lives less than a day
 So bone marrow constantly makes new neutrophils

COMPONENTS OF BLOOD
Platelets (thrombocytes)
Unlike red and white blood cells
platelets are not actually cells
Rather small fragments of cells
Platelets help the blood clotting
(coagulation)
 Assemble at the site of an injury
 Stick to the lining of the injured
blood vessel
 Form a platform on which blood
coagulation can take place

ARTERIES AND VEINS
 Arteries
 Red blood vessels that carry blood away from the heart
 Arteries carry oxygenated blood with the exception of
(pulmonary artery and umbilical artery)
 Blood flows from the heart to various parts of the body
 Thick, elastic muscle layer that can handle high pressure of
the blood
 Located deeper in the body walls
 Arterial walls are more rigid
 Valves aren't present
 Except for semi-lunar valves

 Veins
 Blue blood vessels that carry blood towards the heart
 Veins carry deoxygenated blood with the exception of
(pulmonary veins and umbilical veins)
 Blood flows from various parts of the body to the heart
 Thin elastic muscle layer with semi lunar valves
that prevent
 Blood from flowing in opposite direction
 Located closer to the skin
 Veins have collapsible walls
( Present mainly in limbs)

PRESSURE OF BLOOD IN ARTERIES AND VEINS
 Blood is pumped at high pressure away from the heart in arteries
 It travels through networks of thin capillaries
 Where it can exchange materials with the tissues
 It's then collected up and returned to the heart at low pressure
in veins
 ARTERIES
 The blood in the arteries is under high pressure generated
by the heart therefore
 The arteries have
 Thick outer walls
 Thick layers of muscle and elastic fibers

DIAGRAM SHOWING ARTERIES AND VEINS

 Veins
 The blood in veins is under lower pressure than
the blood in the arteries therefore
 The veins have
 Thin walls
 Thin layers of muscle and elastic fibers

SIZE AND LOCATION OF THE HEART
 Heart is a hollow conical muscular organ
 It is situated in the middle of the thoracic cavity above the
diaphragm
 Under the rib cage, under and to the left of the breastbone
(sternum) between the lungs
 It is of the size of a fist measuring 12cm from base to apex
 8cm broad and 6cm anterio posteriorly
 An adult human heart weighs between 250-350 grams
 It is the most important muscle in the body
 It beats more than a 100,000 times a day
 It pumps about 2000 gallons of blood through a 60,000 times
network of vessels in our body

BASIC ANATOMY OF HUMAN HEART
 Human heart is a four chambered structure
 Two upper chambers called the auricles (Pl: atria )
 Two lower chambers called the ventricles
 The four chambers of the heart are separated by means of
a partition called the septum
 In auricles this partition is called inter auricular septum
 In ventricles it is called inter ventricular septum

THE TWO CHAMBERS OF THE HEART
 The chambers on the left are the left auricle (atrium) and the
left ventricle
 The chambers on the right are called the right auricle(atrium)
and the right ventricle
 The right atrium and right ventricle are often referred to as
the right heart
 similarly the left atrium and left ventricle are often referred to
as the left heart

BLOOD VESSELS OF THE HEART
 Aorta – It is a largest artery in the human body .It leaves
the left side of the heart and supplies oxygenated blood to
the body tissues (Systemic Circulation)
 Pulmonary Veins - They are the blood vessels that deliver
oxygenated blood from the lungs to heart. Two pulmonary
veins enter the left side of the heart from each lung
 Pulmonary Artery - It is a blood vessel that carries
deoxygenated blood from right side of the heart to the
lungs (Pulmonary Circulation)
 Venacavae - (Latin :hollow veins) These are two large
veins that return deoxygenated blood from body tissues to
the right side of the heart

 Inferior Venacava (IV) - It is the largest vein in the human
body
 It carries deoxygenated blood from lower and middle body
into the right atrium
 It is formed by joining of the right and left Iliac veins
 The Iliac veins drain blood from the pelvis and the lower limbs
and come together in the abdomen
 Superior venacava(SVC) - Returns deoxygenated blood
from the systemic circulation to right atrium of the heart
 It has a large diameter 24mm
 It receives blood from the upper half of the body (upper
limbs eyes neck and head)
 Large valveless venous channel formed by the union of the
brachiocephalic veins (internal jugular and subclavian veins)
 Coronary sinus- Is a collection of veins joined together to
form a large vessel
 It collects blood from myocardium (the heart muscle)
 Delivers blood to the right atrium as do the IVC and SVC

DOUBLE CIRCULATION
 Mammals have a double circulatory system which means
One circuit links the heart and lungs
The other circuit links the heart with the rest of the body
 During a single cycle blood goes twice in the heart
 This means that there are two loops in our body in
which blood circulates
 One is oxygenated blood ( oxygen rich)
 The other is deoxygenated blood (it has little or no oxygen
but a lot of carbon dioxide)
IMPORTANCE OF DOUBLE CIRCULATION
It is necessary to separate oxygenated and de-oxygenated blood
 It makes the circulatory system more efficient
 Higher blood pressure so a greater flow of blood to the tissues
 Helps to maintain a constant body temperature

WALLS OF AURICLES AND VENTRICLES
The myocardium has four chambers
two atria superiorly
two ventricles inferiorly
The atria are blood collection chambers
The ventricles are blood pumping chambers
 The right hand side of the heart is smaller than the left
 The muscle of the left ventricle is 2-3 times thicker than that
of the right
 Although the size of the cavity is about the same as the right
 The ventricles have thicker muscular walls than the atria
 Because blood is pumped out of the heart at greater pressure
from the ventricles compared to the atria

The left ventricle also has a thicker muscular wall than the right
ventricle
 Because the left ventricle has to pump blood all around the body
 But the right ventricle has to pump blood only to the lungs
 Higher force is needed to pump blood through the systemic circuit
compared to the pulmonary circuit

VALVES OF THE HEART
There are two types of valves in the
heart
THE ATRIOVENTRICULAR VALVES
Separate the atria from the ventricles
 tricuspid valve (right
atrioventricular valve)
 bicuspid or mitral valve ( left
atrioventricular valve)
THE SEMI LUNAR VALVE
•Found at the base of the aorta and
the pulmonary artery
•Also called the aortic semi lunar valve
and the pulmonary semi lunar valve

Leaflets of the mitral and tricuspid valves
 Are attached to and supported
 By a ring of tough fibrous tissue (Annulus)
 Annulus helps to maintain the proper
shape of the valve
Also
 Supported by tough fibrous string
(chordae tendenae)
 Which extend from valve leaflets to small
muscle (papillary muscles)
 Papillary muscles are part of the inside
walls of ventricles
Each valve has a set of flaps called leaflets or cusps
Bicuspid valve- Mitral valve has two cusps
flaps or leaflets
Tricuspid valves- Tricuspid, Pulmonary and
Aortic valve have three cusps

OUTER COVERING OF THE HEART
The heart is a large muscular organ comprised of four different
layers (from the outside to the inside)
the Pericardium
the Epicardium
the Myocardium
the Endocardium
 Pericardium
 A tough double layered fibro serous sac
 Contain the heart and the roots of the great vessels
The pericardial sac has two layers
1. serous layer
2. fibrous layer
 The space between the two layers of serous pericardium is
 Pericardial cavity which is filled with serous fluid
 The pericardial fluid
 It protects the heart from any kind of external jerk or shock

 Fibrous Pericardium- It is the most external layer made of
dense connective tissue
Functions
 It protects the heart
 Anchor it to the surrounding walls
 Prevent it from over filling with blood
 Serous Pericardium- It has two layers
• parietal pericardium
(combined to and inseparable from the fibrous pericardium)
• visceral pericardium (part of the epicardium)
 The visceral layer extends till the opening of the great vessels
It joins with the parietal layer where
 the aorta and pulmonary arteries leave the heart
 the venacavae and pulmonary veins enter the heart

FUNCTION
Help to lubricate heart to avoid friction
during heart activity
 EPICARDIUM
 A thin layer of connective tissue and fat
 Provide an extra layer of protection for
the heart
 It is considered an extension of serous
pericardium
 MYOCARDIUM
 Muscle tissue of the heart
 Composed of cardiac muscle cells
(cardiomyocytes)
 Receives nervous stimulation from the
sinoatrial node (SA) and atrioventricular
(AV) node via purkinje fibres

 ENDOCARDIUM
 Innermost layer of tissue
 Simple squamous
endothelial
 Is continuous with
 Endothelial lining
of great blood vessels
FUNCTION
 Lines the inside of the heart
 Offer a smooth lining
for chambers of the heart
 Cover the valves
A SECTION OF THE HEART WALL

STRUCTURE OF THE CARDIAC MUSCLE
Cardiac muscles are
 Involuntary and striated
 The cells that make up the cardiac muscle are cardiomyocytes
 Muscle fibers are shorter in length and larger in diameter
 Show branching therefore individual fibre looks Y-shaped
 A typical fibre is 50-100μm long
 Has a diameter of about 14μm
 Usually mononucleated
 Rarely two or four nuclei can be present
 Cells are interconnected by intercalated discs
 The sarcoplasm(the cytoplasm of striated muscles) is abundant
 Mitochondria are large and numerous
 Actin filaments are thin and myosin filaments are thick
 Cardiac muscle does not fatigue
 Cannot be repaired when damaged
 Regulated by the Autonomic Nervous System

 Intercalated discs
 Are located between cardiac
muscles cells
 Anchoring structures of
cardiac muscle cells
 Hold gap junctions
 Which allow cells to contract
as a unit
(synchronized contraction)

BLOOD FLOW THROUGH THE HEART
The right and left sides of the heart work together causing blood
to flow continuously to the heart lungs and body
 Right side of the heart
 Blood enters the heart through two large veins
 The inferior and superior vena cava emptying oxygen-poor blood
(from the body) into the right atrium
 As the right atrium contracts blood flows into right ventricle
(through the open tricuspid valve)
 When the ventricle is full the tricuspid valve shuts
 Prevents blood from flowing backward into the right atrium while
the right ventricle contracts
 As the ventricle contracts blood leaves the heart
(through the pulmonic valve)
 Into the pulmonary artery and to the lungs where it is oxygenated

The oxygenated blood then returns to the heart through the
pulmonary veins
 Left side of the heart
Pulmonary veins empty
 Oxygen-rich blood from the lungs into the left atrium
 As the atrium contracts
 Blood flows from atrium into the ventricle
(through the open mitral valve)
• When the ventricle is full
(the mitral valve shuts)
 Prevents blood from flowing backward into the atrium
(while the ventricle contracts)
• As the ventricle contracts
 Blood leaves the heart
(through the aortic valve)
 Into the aorta and to the body

Blood Flow Through Lungs
 Blood travels through the pulmonic valve enters the lungs
(pulmonary circulation)
From the pulmonary valve
 Blood travels to the pulmonary arteries
 Finally to small capillary vessels in the lungs
 Oxygen passes into the blood through
 Capillaries located in the walls
 Of tiny air sacs in the lungs (alveoli)
At the same time
 Carbon dioxide (waste product of metabolism)
 Passes from the blood into the alveoli
 Carbon dioxide leaves the body as we exhale
 As the blood is oxygenated
 It travels back to the left atrium through the pulmonary veins
 Lastly from left ventricle to the body tissues through aorta
(Systemic circulation)

THANK YOU
Prepared by
Ritu sharma

Human heart anatomy and physiology Part -1

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