FunctionsTransport oxygen and nutrients to the lungs and tissuesForm blood clots to prevent excess blood lossCarry cells and antibodies that fight infectionBring waste products to the kidneys and liver to filter bloodRegulate body temperature
2. 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
White blood cells
Red 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
3. 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)
4. 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)
5. 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
6. 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
8. 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
9. 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)
10. 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
12. 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
14. 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
15. 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
16. 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
18. 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
19. 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
20.
21. 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
22. 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
23. 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
24. 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
25. 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
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
26. 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
27.
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
28. 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
30. 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
31. 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
32. 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)
33.
34. 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
35. 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
37. 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)