The cardiovascular system consists of the heart and blood vessels. The heart has four chambers and uses valves to ensure one-way blood flow. It pumps deoxygenated blood to the lungs and oxygenated blood throughout the body. Blood travels through arteries, capillaries, and veins in both pulmonary and systemic circuits. The heart's conduction system uses electrical signals to coordinate contractions. Factors like preload and afterload influence cardiac output. Blood pressure is regulated by baroreceptors, chemoreceptors, and the renin-angiotensin system.

1. Cardiovascular System:
Heart & Circulation

5. I. Anatomy of the Heart
A. Coverings
1. Pericardium
• fibrous pericardium
• serous pericardium
• parietal pericardium
• visceral pericardium
B. Heart wall layers
1. Epicardium – (visceral pericardium)
• protects heart
2. Myocardium – cardiac muscle
3. Endocardium – epithelial/ connective/ fibers

6. C. Chambers, Vessels, and Valves
1. Four chambers
• upper chambers – rt and left atria
Collects blood
• lower chambers – rt and left ventricle
pumps blood from heart
2. Arteries
• carry blood away from heart
3. Veins
• blood toward heart

8. 4. Valves
• AV valves
Tricuspid – rt atrium
Bicuspid or mitral - lt atrium
• Semilunar valves
Pulmonary semilunar (pulmonary trunk)
Aortic semilunar (aortic arch)
II. Pulmonary and Systemic Circulation
A. Pulmonary pathway
oxygenated blood –rt ventricle from rt atrium
myocardium (rt ventricle) contracts

12. low oxygen blood through pulmonary semilunar
pulmonary trunk -> arteries -> lungs
oxygenated blood -> rt & lt pulmonary veins ->
left atrium
B. Systemic pathway
Oxygenated blood -> Lt atrium to Lt ventricle
Left ventricle contracts ->aortic semilunar
Aortic arch -> arteries to tissues
oxygen depleted blood from tissues ->
veins to heart -> rt atrium (vena cava)

13. Passage of Blood Through the
Heart
 Blood follows this sequence through the heart:
superior and inferior vena cava → right atrium
→ tricuspid valve → right ventricle →
pulmonary semilunar valve → pulmonary trunk
and arteries to the lungs → pulmonary veins
leaving the lungs → left atrium → bicuspid
valve → left ventricle → aortic semilunar valve
→ aorta → to the body.

14. Direction of blood flow through the heart

15. The relationship between the systemic and pulmonary circulations

16. Blood supply to the heart or
coronary circulation
The coronary arteries

17. Blood supply to the heart
Arterial supply
 The heart is supplied with arterial
blood by the right and left coronary
arteries, which branch from the aorta
immediately distal to the aortic
valve
 The coronary arteries receive about
5% of the blood pumped from the
heart, although the heart comprises a
small proportion of body weight
 This large blood supply, especially
to the left ventricle, highlights the
importance of the heart to body
function
 The coronary arteries traverse the
heart, eventually forming a vast
network of capillaries

18. Blood supply to the heart –
Venous drainage
 Most of venous blood is collected
into several small veins that join
to form coronary sinus, which
opens into right atrium
 The remainder passes directly into
the heart chambers through little
venous channels

21. THE CARDIAC CYCLE
What is the cardiac cycle
The cardiac cycle is the sequence of
events that occur when the heart beats
There are two phases of this cycle:
Diastole - Ventricles are relaxed
Systole - Ventricles contract

22. The cardiac cycle
Exercise increases blood flow through the heart so that the
cardiac cycle accelerates to accommodate the increased
demand for oxygen
The normal cycle is around 0.8 seconds. This accelerates with
faster and more powerful atrial and ventricular contraction,
which is stimulated by the cardiac centre in the brain
Heart rate:- is defined as the number of heart contractions in
each minute
# There are two distinct periods in the cardiac cycle- one of the
heart muscle relaxation (cardiac diastole), the other of
contraction (cardiac systole)

23. Cardiac diastole
During cardiac diastole
• The bicuspid and tricuspid
valves are closed and the
atrium is full
• Once full with blood, the
atria forces the bicuspid and
tricuspid valves to open and
fill the ventricles
• This lasts for around 0.4
seconds at rest

24. Cardiac systole
Cardiac systole
• The atria contract and send
blood via the bicuspid and
tricuspid valves into the
ventricles
• When full, these contract
causing blood to be expelled
from the heart via the semi-
lunar valves
• (the bicuspid and tricuspid
valves are closed at this time)
• This lasts around 0.4 seconds at
rest

25. The Cardiac Cycle
Heart at rest
– Blood flows from large veins into atria
– Passive flow from atria into ventricles
Atria (R & L) contract simultaneously
– Blood forced into ventricles
Ventricles (R & L) contract simultaneously
– Atrioventricular valves close  “lubb” sound
– Blood forced into large arteries
Ventricles relax
– Semilunar valves close  “dub” sound
Heart at rest

27. Heart valves
• Valves are flap-like structures that allow blood to flow in
one direction
• The heart has two kinds of valves, atrioventricular and
semilunar valves
Heart sounds
The audible sounds that can be heard from the heart are
made by the closing of the heart valves
These sounds are referred to as the “lub-dupp” sounds
The “lub” sound is made by the contraction of the
ventricles and the closing of the atria-ventricular valves
The “dupp” sound is made by the semi-lunar valves
closing

28. Conducting system of Heart

29. Stimulation of the heart originates in the
cardiac centre, in the “medulla oblongata.”
The “sympathetic and parasympathetic
nervous systems” work antagonistically and
provide the stimulation for acceleration and
deceleration of the heart rate
Cardiac systole (contraction) is initiated by
the electrical cardiac impulse from the “sinu-
atrial node” (the pace-maker found in the
right atria wall)
This distributes electrical stimulus through
the “myocardial” (heart muscle) wall
between the heart chambers
where the “atrio-ventricular node” (between
the right atrium and right ventricle)
continues distribution of the electrical signal
across the ventricles

30. The SA node
• In the upper part of the right atrium of the heart is a specialized bundle of neurons
known as the sino-atrial node (SA node)
• Acting as the heart's natural pacemaker, the SA node "fires" at regular intervals to
cause the heart of beat with a rhythm of about 60 to 70 beats per minute for a
healthy, resting heart
• The electrical impulse from the SA node triggers a sequence of electrical events in
the heart to control the orderly sequence of muscle contractions that pump the
blood out of the heart
The AV node
• The AV node (AV stands for atrioventricular) is an electrical relay station
between the atria (the upper) and the ventricles (the lower chambers of the
heart)
• Electrical signals from the atria must pass through the AV node to reach the
ventricles

31. AV node (bundle of his)
The bundle of His is located in the proximal interventicular septum
It emerges from the AV node to begin the conduction of the impulse from the AV
node to the ventricles

32. Purkinje fibers
Purkinje fibers are heart muscle tissues that are specialized to
conduct electrical impulses to ventricular cells, which induce the
lower chambers of the heart to contract
Impulses from the upper chambers of the heart are relayed by this
node to large bundles of Purkinje fibers referred to as the Bundle
of His
These bundles branch into smaller elements and eventually form
terminal ends that burrow into left and right ventricular chamber
muscles
As the impulse is passed to the ventricles, the muscles contract and
pump blood
The contraction caused by the specialized fibers begins from the
bottom of the ventricles and move upwards so that the blood leaves
the lower chambers through the pulmonary arteries and the aorta

34. Signal Conduction Pathway
• SA action potentials -> contraction in atrium
• AV action potentials (slower) -> bundle of HIS->
through septum -> Purkinje fibers -> contraction
C. Electrocardiography
• electrical events corresponding to mechanical
• P wave: atrial fibers depolarize
• QRS complex: ventricles depolarize
• T wave: ventricles repolarize

35. Electrocardiography

36. Cardiac Output (CO)
 CO is the amount of blood pumped by each
ventricle in one minute
 CO is the product of heart rate (HR) and
stroke volume (SV)
 HR is the number of heart beats per minute
 SV is the amount of blood pumped out by a
ventricle with each beat

37. Cardiac Output: Example
 CO (ml/min) = HR (75 beats/min) x SV
(70 ml/beat)
 CO = 5250 ml/min (5.25 L/min)

38. Regulation of Stroke Volume
 SV = end diastolic volume (EDV) minus
end systolic volume (ESV)
 EDV = amount of blood collected in a
ventricle during diastole
 ESV = amount of blood remaining in a
ventricle after contraction

39. Factors Affecting Stroke Volume
 Preload – amount ventricles are stretched
by contained blood
 Contractility – cardiac cell contractile force
due to factors other than EDV
 Afterload – back pressure exerted by blood
in the large arteries leaving the heart

40. Preload and Afterload

41. Regulation of Heart Rate
 Positive chronotropic factors increase heart
rate
 Negative chronotropic factors decrease
heart rate
 Autonomic nervous system
 Hormones

42. Blood Pressure & its regulation
 Blood pressure is the force or pressure that the
blood exerts on the walls of the blood vessels
 BP = CO x TPR
 CO= SV x HR
 BP = Blood Pressure
 CO = Cardiac Output
 TPR = Total Peripheral Resistance
 SV = Stroke Volume
 HR = Heart rate

43. Control of Arterial Blood Pressure

44. Control of Blood Pressure
 Short term control :
 Baroreceptors
 Chemoreceptors
 Higher centres in the brain
 Long term control:
RAAS system

45. Summary of the main mechanisms in blood pressure control

46. Baroreceptors
 Located in walls of aortic arch and left and
right carotid sinus
 Mechanical stretch receptors
 Neuronal circuits in brainstem compare
actual value of BP provided by the
baroreceptors with the set point or optimal
value

47. The baroreceptor reflex

48. Chemoreceptor
 Nerve ending situated in the carotid and aortic bodies
 control of respiration
 Sensitive to changes in the levels of Co2 , O2 and
acidity of the blood
The relationship between stimulation of
chemoreceptors and arterial blood pressure

49. Higher centres in the brain
 Fear
 Anxiety
 Pain
 Anger

50. Long term Blood pressure regulation
 Renin-angiotensin-aldosterone system
(RAAS)
 Anti-diuretic harmone (ADH)
 Atrial natriuretic peptide (ANP)
harmone released by heart
sodium and water loss from the kidney
reduces blood pressure

51. RAAS System

52. Disorder of CVS
• Hypertension
• Hypotension
• Congestive heart failure
• Cardiac Arrhythmia
• Angina Pectoris
• Arteriosclerosis
• Myocardial Infarction

53. Hypertension
 Essential hypertension
Benign (chronic ) hypertension
Malignant ( accelerated) hypertension
 Secondary hypertension
Kidney disease
Endocrinal disorders

54. Heart failure
Acute heart failure
Chronic heart failure
Right-sided (congestive) heart failure
Left-sided (left ventricular) heart failure

55. Cardiac arrhythmia
Sinus bradycardia
Sinus tachycardia
Asystole
Fibrillation
Atrial fibrillation
Ventricular fibrillation
Heart block

56. Blood Vessels
Functions:
 Distribution of blood
 Exchange of materials with tissues
 Return of blood to the heart
Structure:
 Most have the same basic structure:
– 3 layers surrounding a hollow lumen

57. General Structure of Blood Vessels
Arteries and veins are composed of three tunics:
 tunica interna
 tunica media
 tunica externa
 Capillaries are composed of endothelium

58. General Structure

59. The Vessels
1. Tunica Intima
 innermost smooth layer
 simple squamous epithelium
 continuous with the endocardium
 present in all vessels

60. The Vessels
2. Tunica Media
 layer of smooth muscle - circular arrangement –
contains elastin
 supplied by sympathetic division of the ANS
 depending on body’s needs – lumen is narrowed
(vasoconstriction) or widened (vasodilation)

61. The Vessels
3. Tunica Externa (Adventitia)
 thin layer of CT
 elastic & collagen fibres

62. The Vessels
Types of Vessels:
 Arteries – carry blood away from the heart
 Veins – carry blood towards the heart
 Capillaries – the most important part of
the vascular system; site of exchange of
materials

63. Types of Blood vessels: Arteries
Elastic Arteries:
 Thick-walled arteries near the heart; the aorta and its
major branches
 Large lumen allows low-resistance conduction of
blood
 Contain lots of elastin in all three tunics
 walls stretch and recoil to propel blood
 Withstand and regulate large blood pressure
fluctuations

64. Types of Blood vessels: Arteries
Muscular (distributing) arteries
 medium sized vessels
 tunica media more smooth muscle;
less elastin
 major area of vaso-constriction &
dilation to regulate blood flow

65. The Vessels
Arterioles (diameter of 0.3 mm or less)
- smallest arteries; lead to capillary beds
- close to capillaries - single layer of
muscle spiralling around the endothelial
lining
- regulates blood flow to capillary

66. The Vessels
Capillaries
 Smallest vessels – diameter just large
enough for a red blood cell
 walls consist of tunica intima only
(i.e. layer of endothelium)
 thinness facilitates exchange of
materials