2. Objectives
At the end of this session, the students will be able
to:
• Define Heart and it functions
• Define blood vessels and list its functions
• Show electrical activity of heart
• define mechanical events of heart
• Show Cardic output and its control
3. Parts of the Circulatory System
• Divided into three major parts:
– Heart
– Blood
– Blood Vessels
8. Functions of C-V System
• Circulate blood throughout entire body for
– Transport of oxygen to cells.
– Transport of CO2 away from cells.
– Transport of nutrients to cells.
– Movement of immune system components. (cells,
antibodies)
– Transport of endocrine gland secretions.
9. Heart
• Location: mediastinum and rests on the diaphragm.
• Size: as much as one’s close fist.
• Weight: 250 g in adult female and 300 g in male.
• Structure: Cone shaped with pointed apex inferiorly to left
and broad base superiorly to the right.
Membranous Layers
• Two Pericardiums as superficial fibrous pericardium of
connective tissue and deeper serous pericardium of
epithelial tissue connected with the fibrous pericardium.
• Serous pericardium—Parietal and visceral membrane.
Pericardial cavity with pericardial fluid.
10. Right Side of the Heart
• Right atrium is a thin walled and low pressure chamber
• It has sinoatrial (SA) and atrioventricular (AV) node
• It receives venous blood via two large veins i.e. Superior and
inferior vena cava
• It communicate with right ventricle through tricuspid valve
• Walls of right ventricle is thick and receives blood from right
atrium
• From the right ventricle, pulmonary trunk carries the venous
blood to lungs
• In the lungs, the deoxygenated blood become oxygenated
12. Left Side Of The Heart
• Left atrium is a thin walled and low pressure
chamber
• It receives oxygenated blood from the lungs
through four pulmonary veins
• Blood from left atrium enters the left ventricle
through mitral valve
• Wall of the left ventricle is very thick
• Left ventricle pumps blood to different parts of
the body through systemic aorta
13. Septa Of the Heart
• Right and left atria are separated by a fibrous
septum called interatrial septum
• Right and left ventricles are separated from
one another by interventricular septum
• The upper part of this septum is a
membranous, whereas the lower part is
muscular in nature
15. Layers of heart
• —three layers
Epicardium or visceral layer
Myocardium—muscular layer
Endocardium—endothelial layer
16. • Pericardium is made up of two layers
1. Outer parietal pericardium
2. Inner visceral pericardium/ epicardium
• The space between the two layers is called
pericardial cavity or space and contains a thin
film of fluid
17. MyoCardium
• It is formed by cardiac muscle fibers or cardiac
myocytes
• Myocardium forms the bulk of the heart and it is
responsible for pumping
• Myocardium has three types of muscle fibers
i. Muscle fibers which form contractile unit of
heart
ii. Muscle fibers which form pacemaker
iii. Muscle fibers which form conductive system
18. Myocardium
• These are striated and resemble the skeletal muscle in
structure
• But, it is branched
• It is bound by sarcolemma having central nucleus
• Sarcomere have all the contractile proteins
• Neighboring fibers are fused by a tough double
membranous structure, that form junction called
intercalated disk
• At the sides, the membranes of the adjacent muscle
fibers fuse together to form gap junctions
20. Valves
Your heart has four valves. They act like gates,
keeping the blood moving in the right direction:
aortic valve - on the left side
mitral valve - on the left side
pulmonary valve - on the right side
tricuspid valve - on the right side
21. Valves permit the flow of blood in only one direction
Two atrioventricular valves
1. Bicuspid valve
2. Tricuspid valve
Cusps of the valves are attached to papillary muscles by
means of chordae tendineae
Two semilunar valves
3. Aortic valve
4. Pulmonary valve
Semilunar valves are made up of three flaps
22. Blood vessels
Your blood is pumped around your body through a network of
blood vessels:
arteries - they carry oxygen-rich blood from your heart to all
parts of your body, getting smaller as they get further away from
the heart
capillaries - they connect the smallest arteries to the smallest
veins, and help exchange water, oxygen, carbon dioxide and other
nutrients and waste substances between the blood and the
tissues around them
veins - they carry blood, lacking in oxygen, back towards your
heart, and get bigger as they get nearer your heart
Blood vessels are able to widen or narrow depending on how
much blood each part of your body requires. This action is partly
controlled by hormones.
26. Walls of the arterial system are formed by
three layers:
1. Artrial System
2. Walls of the arterial system are formed by
three layers:
3. Outer tunica adventitia- connective tissue
layer
4. Middle tunica media- smooth muscles
5. Inner tunica intima- endothelium
6. It have two laminae of elastic tissues:
i. External elastic lamina- adventitia and media
ii. Internal elastic lamina- media and intima
1. Aorta and arteries have more elastic tissues
and the arterioles have more smooth muscles
2. Outer tunica adventitia- connective
tissue layer
27. Arterial branches become narrower and walls become
thinner while reaching the periphery as:
AortiCoCCont....
Arterial branches become narrower and walls become
thinner while reaching the periphery as:
Aortic diameter = 25 mm
Diameter of end arteries = 4 mm
Diameter of ends arterioles = 10 µ
Resistance is offered to blood flow in the arterioles and
are called resistant vessels
Arterioles are continued as capillaries, which are small,
thin walled having a diameter of about 5 to 8 µ
The exchange of materials between the blood and the
tissues occurs through capillaries
c diameter = 25 mm
28. Venous Systm;
From the capillaries, venous system starts as it
end on venules
Venules are smaller and thinner than the
arterioles
At a time, a large quantity of blood is held in
venules and are called capacitance vessels
Venules are continued as veins, that form venae
cavae
The elastic tissue is less but the smooth muscle
fibers are more
29. 29
3 Major types of blood
vessels
• Body
• RA
• RV
• Lungs
• LA
• LV
• Boby
1.Arteries
2.Capillaries
3.Veins
Arteries carry blood away from the heart
-”branch,” “diverge” or “fork”
Veins carry blood toward the heart
-”join”, “merge,” “converge”
30. 30
Capillaries
Heart to arteries to capillaries to veins to heart
• Capillaries are smallest
– 8-10um
– Just big enough for single file erythrocytes
– Composed of: single layer of endothelial cells surrounded by
basement membrane
• Universal function
– Oxygen and nutrient delivery to tissues
– CO2 and nitrogenous waste removal
43. Electrical system
For your heart to keep pumping regularly, it
needs electrical signals which are sent to the
heart muscle telling it when to contract and relax.
The electrical signal starts in the right atrium
where your heart’s natural pacemaker - the sino–
atrial node - is situated. This signal crosses the
atria, making them contract. Blood is pumped
through the valves into the ventricles.
44. Where the atria meet the ventricles, there is an area
of special cells - called the atrio-ventricular node -
which pass the electrical signals throughout your
heart muscle by a system of electrical pathways,
known as the conducting system.
The muscles of the ventricles then contract, and
blood is pumped through the pulmonary and aortic
valves into the main arteries.
The heart’s natural ‘pacemaker’ - the sino-atrial
node - produces another electrical signal, and the
cycle starts again.
45. Blood pressure
This is the measurement of the pressure within the
arteries. It plays a vital role in the way your heart
delivers fresh blood to all your blood vessels. For blood
to travel throughout your body quickly enough, it has
to be under pressure. This is created by the relationship
between three things:
your heart’s pumping action
the size and stretchiness of your blood vessels
the thickness of the blood itself
48. • Atrial systole (Atrial Contraction)
Lasts about 0.1 sec.
• It follows the impulse generation in SA node
and atrial depolarization.
When the atrial muscle contracts, pressure in
atria increases.
30% of blood is propelled into ventricle.
Narrowing of opening of SVC and IVC and
pulmonary veins occur.
49. • Ventricular systole
Isovolumetric contraction
In isovolumetric contraction ventricular pressure exceed atrial
pressure closure of AV valves occur producing first heart sound.
Opening of aortic valve occur when left ventricular pressure is >
8OmmHg.
Opening of pulmonary valve is seen when right ventricular
pressure > 10 mmHg.
This will result in small rise in atrial pressure.
Rapid ejection
After opening of the aortic and pulmonary valves, ventricular
ejection begins.
Intraventricular pressure rises to a maximum of 120 mmHg in
left ventricle and 25mmHg in right ventricle.
2/3rd stroke volume is ejected during this phase.
50. • Reduced ejection phase
Ventricular pressure decreases during this phase.
Arterial pressure increases.
• Ventricular diastole
1.Protodiastole
At the end of ventricular systole, ventricular pressure falls, arterial
pressure is more than pressure inside the ventricle resulting in closure
of semilunar valves which produce second heart sound.
2.Isovolumetric ventricular relaxation
Ventricular pressure drop rapidly in this phase ,the ventricular muscle
relax without change in ventricular volume.
This phase ends when ventricular pressure drops below atrial pressure
resulting in opening of AV valves.
51. • 3.Phase of earlier rapid filling
Rapid filling of ventricles occur.
Pressure inside the ventricles remains low.
4.Phase of reduced filling
Filling of ventricles is due to continous venous return filling
both atria and ventricle.
70% ventricular filling.
5.Last rapid filling
Corresponds to atrial systole.
30% filling occur in this phase.
• Atrial diastole
Atrial muscle relax and atrial pressure increase gradualy due
to continous venous return.
After the opening of atrioventricular valves pressure drops
to zero and again slowly rises until the next atrial systole.
53. Cardiac Output
• The amount of blood ejected by each ventricle in
one minute is called cardiac output (CO).
• Cardiac output = Heart rate × Stroke volume
• Pulse pressure (PP) is the difference between
systolic blood pressure (SBP) and diastolic blood
pressure (DBP).
• Cardiac Reserve:
• The difference between the maximum and resting
cardiac output is called cardiac reserve.
54. CORONARY CIRCULATION
• Heart is supplied by TWO CORONARY arteries:
1- Left coronary artery---(LCA)
2- Right coronary artery---(RCA)
• These coronary arteries arise at the root of
the aorta.
54
57. 57
Special features of veins
• Valves
– Prevent backflow
– Most abundant in legs (where blood
has to travel against gravity)
• Muscular contraction
– Aids the return of blood to heart in
conjunction with valves
59. 59
Vascular System
(Blood vessels of the body)
• Two circulations
– Systemic
– Pulmonary
• Arteries and veins usually run together
• Often nerves run with them
60. 60
Pulmonary Circulation
• Pulmonary trunk branches
– Right and left pulmonary arteries
– Division into lobar arteries
• 3 on right
• 2 on left
– Smaller and smaller arterioles, into capillaries surrounding alveoli
• Gas exchange
61. 61
Pulmonary Circulation
• After gas exchange blood enters venules
• Larger and larger into Superior and Inferior Pulmonary
veins
• Four Pulmonary Veins empty into left atrium
63. 63
Systemic Circulation
• Oxygenated blood to body
• Leaves LV through Ascending Aorta
– Only branches are the 2 coronary arteries to the heart
• Aortic Arch has three arteries branching from it:
1. Brachiocephalic trunk, has 2 branches:
• Right common carotid a.
• Right subclavian a.
2. Left common carotid a.
3. Left subclavian a.
Ligamentum arteriosum
connecting to pulmonary a.
64. 64
• Hepatic portal system
– Picks up digested nutrients from stomach & intestines and
delivers them to liver for processing and storage
• Storage of nutrients
• Detoxification of toxins, drugs, etc.
Tributaries of hepatic
portal vein:
-superior mesenteric vein
-splenic vein
-inferior mesenteric vein
