Slides from our seminar on the CVS module.

1. Regulation of Coronary Blood
Flow

2. OUTLINE
• CORONARY VESSELS
• CORONARY BLOOD FLOW
• AUTONOMIC INNERVATION OF HEART AND
VASCULATURE
• FACTORS AFFECTING CORONARY BLOOD FLOW
• CORONARY AUTOREGULATION
• APPLIED ASPECTS

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ZULFANI ARIANTI ZAKARIA

4. CORONARY BLOOD
SUPPLY
• CONSIST OF
1) Arterial supply
2) Venous drainage

7. 1.ARTERIAL SUPPLY
• The cardiac muscle is supplied by
two coronary arteries
(a) the right and
(b) left coronary arteries.
• Both arteries arises from the sinuses
behind the cusps of the aortic valves
at the root of the aorta.

8. RT. CORONARY ARTERY
• Smaller than left coronary artery.
• Arises from anterior aortic sinus
of ascending aorta.

9. COURSE:
• Emerges from the surface of heart between
pulmonary trunk and right auricle.
• Winds round the inferior border to reach the
diaphragmatic surface to reach the posterior
inter-ventricular sulcus(groove).
• Terminates by anastomising with left
coronary artery

12. BRANCHES OF RCA
– Conus arteriosus br.
– SA Nodal
– Marginal br.
– Posterior interventricular artery
– Right atrial br.
– Anterior ventricular br.
– Posterior ventricular br.

15. LEFT CORONARY ARTERY
• Larger than the right
coronary artery.
• Arises from left posterior
aortic sinus.

16. COURSE
• Runs forward and to the left and emerges
between the pulmonary trunk and the left
auricle.
• Here the anterior inter-ventricular branch is given
.
• The further continuation of the left coronary
artery is sometimes called the circumflex artery.
• After giving off the anterior interventricular
branch it runs to the left in the left anterior
coronary sulcus.
• It winds around the left border and near
posterior interventriular groove it terminates by
anastomosing with the right coronary artery.

17. BRANCHES:
 Anterior interventricular artery
 Left diagonal artery
 Circumflex artery
 Left marginal artery
 Anterior ventricular branch
 Posterior ventricular branch
 Atrial branch

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NURSYAFIKAH MUHAMAD
NASIR

22. RIGHT DOMINANT
LEFT DOMINANT
CARDIAC DOMINANCE

23. VENOUS DRAINAGE OF THE HEART
• The venous drainage of the
heart is by three means:
– Coronary sinus.
– Anterior cardiac veins
– Venae Cordis minimae.

24.  Coronary sinus:
• Largest vein of the
heart
• Length: 3 cm long
• Situation: Coronary
sulcus.
Tributaries of CS:
-Great cardiac vein
-Middle cardiac vein
-Small cardiac vein
-Oblique vein of left atrium
-Right marginal vein
-Posterior vein of left
ventricle.

26. 012014100164
WAN NUR AINI BINTI
MOHAMAD ZAIN

27. CORONARY
BLOOD
FLOW

28. • The cardiovascular system is composed of
two circulatory paths ;
– Pulmonary circulation
The part of blood circulation which carries oxygen-
depleted blood away from the heart, to the lungs,
and returns oxygenated blood back to the heart.
– Systemic circulation
The part of blood circulation that carries
oxygenated blood away from the heart, to the
body, and returns deoxygenated blood back to the
heart.

30. Pulmonary circulation
• Oxygen-depleted blood from the body enters
the RA through the superior and inferior venae
cavae.
• The blood is then pumped through the tricuspid
valve into the RV.
• From the RV, blood is pumped through
the pulmonary valve and into the pulmonary
artery.
• The pulmonary artery splits into the right and
left pulmonary arteries and travel to each lung.

31. • At the lungs, the blood travels through
capillary beds on the alveoli where respiration
occurs
 removing CO2 and adding O2 to the blood.
• The oxygenated blood then leaves the lungs
through pulmonary veins, which returns it to
the LA, completing the pulmonary circuit.

32. Systemic Circulation
• Oxygen-rich blood from the lungs enters the LA
through the pulmonary veins.
• The blood is then pumped through the mitral
valve into the LV.
• From the LV, blood is pumped through the aortic
valve and into the aorta, the body's largest artery.
• The aorta arches and branches into major
arteries to the upper body before passing
through the diaphragm, where it branches
further into arteries which supply the lower parts
of the body.

33. • Waste and CO2 diffuse out of the cell into the blood,
while O2 in the blood diffuses out of the blood and
into the cell.
• The deoxygenated blood continues through the
capillaries which merge into venules, then veins, and
finally the venae cavae, which drain into the RA of the
heart.
• From the RA, the blood will travel through the
pulmonary circulation to be oxygenated before
returning again to the system circulation.
• Coronary circulation, blood supply to the heart muscle
itself, is also part of the systemic circulation.

34. 34
Overview
• The right side receives
oxygen-poor blood from the
body and tissues and then
pumps it to the lungs to pick
up oxygen and dispel carbon
dioxide
• Its left side receives
oxygenated blood returning
from the lungs and pumps
this blood throughout the
body to supply oxygen and
nutrients to the body tissues
The heart=a muscular double pump with 2 functions

35. Characteristics
of coronary circulation

36. NORMAL CORONARY BLOOD FLOW
- Under resting conditions coronary blood flow (CBF) in
the human heart averages 70ml/min/100g heart weight or
about 225ml/min which is about 4-5% of the total cardiac
output.
- In severe muscular exercise, the work of the heart
increased and the CBF may be increased up to 2 liters/
minute.

37. – Coronary Inflow (arterial) occurs mainly during diastole,
because during systole the coronary arteries are
mechanically compressed by the contracting
myocardium, i.e.
 Systole of the heart   coronary inflow
 Diastole of the heart   coronary inflow
- Coronary Outflow (venous) occurs mainly during
systolic due to compression of the coronary veins by the
contracting myocardium. During diastole coronary
outflow  and veins are filled.

38. Blood flow to Heart during Systole &
Diastole

39. • Phasic nature
During systole when heart muscle contracts
it compresses the coronary arteries therefore
blood flow is less to the left ventricle during
systole and more during diastole
• Coronary blood flow to the right side is not
much affected during systole.
Reason---Pressure difference between aorta
and right ventricle is greater during systole than
during diastole, therefore more blood flow to
right ventricle occurs during systole.
39

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NURUL EDDIYA KIEW

41. Autonomic Innervation of Heart
and Vasculature

43. FACTORS REGULATING CORONARY
BL.FLOW
• Physical
• Chemical
• Neural
• Hormonal
• Reflex

44. Physical Factors :
1. Aortic Blood Pressure
CBF is directly proportional to aortic blood
pressure (diastolic)
Diastolic pressure decreases or MAP
decreases
CBF will decreases.

45. 2. Heart Rate
Excessive  in the heart rate
 diastolic period
coronary filling
 CBF

46. 3. Cardiac Output
CBF is directly proportional to COP
Increased cardiac output
 BP in aorta + reflex inhibition of the
vagal vasoconstrictor tone
coronary vasodilatation
 CBF

47. • C.B.F. occurs mainly during diastole due to
- compression of coronary blood vessels during
systole by the contracted muscle fibers.
During diastolic phases :
- C.B.F. is more than that during
systole.
- Maximal blood flow during
iso volumetric relaxation
phase
During systolic phase :
- CBF is less than that
during diastole.
- Minimal blood flow
during iso volumetric
contraction phase.

48. Chemical Factors :
1. Metabolic factors
 cardiac metabolism
 O2tension (local hypoxia)
 CO2
 K+, lactic acid & adenosine in the
cardiac muscle
coronary vasodilatation ->  CBF.

49. 2. Drugs
Nitrites, angised, aminophylline, caffeine
& Khellin (coronary vasodilator)
coronary vasodilatation
 CBF

50. NERVOUS FACTORS

51. Direct effect:
• Parasympathetic:
vagus has very slight distribution to coronary, so its stimulation
has slight dilator effect.
• Sympathetic:
Both alpha and Beta receptors exist in the coronary vessels.
Sympathetic stimulation causes slight direct coronary
constriction.
Indirect effect:
• Plays a far more important role in normal control of coronary
blood flow than the direct.
• Sympathetic stimulation increase both heart rate and
myocardial contractility, as well as its rate of metabolism
leading to dilatation of coronary blood vessels.
• The blood flow increase proportional to the metabolic need of
heart muscle

52. HORMONAL FACTOR
• Thyroxin   cardiac metabolism   coronary
vasodilator   CBF.
• Vasopressin (antidiuretic hormone)  coronary
vasoconst   CBF.

53. REFLEX CONTROL
• Anrep’s reflex:
• Increased venous return causes increased pressure
in right atrium, leading to reflex increase in CBF e.g.
during muscular exercise.
• Gastro-coronary reflex:
• Distention of the stomach with heavy meal causes
reflex vasoconstriction of coronary blood vessels
decreasing CBF.

54. Coronary Autoregulation
• If there is sudden change in aortic pressure,
coronary vascular resistance will adjust itself
proportionally within few seconds; so that a
constant blood flow is maintained.
• Range of autoregulation: 60 – 140 mmHg.
Mechanism:
• Myogenic response:
• an increase in passive stretch, caused by
increased perfusion pressure, causes active
smooth muscle contraction.

55. • Chemical theory:
• Decrease perfusion pressure leads to
Increase adenosine & Decreased oxygen which
causes Vasodilatation and increase CBF
• Endothelium derived relaxation factor (EDRF):
• Hypoxia, ADP, muscular exercise (increase
distention force), stimulate vascular endothelium
to secrete EDRF, which is a potent vasodilator,
that causes coronary dilatation and increase CBF.

57. 012014100146
NURRAH NADZIRAH BINTI
MOHD RAUZIA

58. Applied aspects

59. 2nd Year Pathology 2010
Thrombosis
• Inappropriate activation of haemostatic
mechanisms
– E.g. uninjured vessel or very minor injury
• Definition:
– formation of solid mass of blood constituents within
vascular system in life
• Virchow’s triad:
1. changes in the vessel wall
2. changes in blood flow
3. Hypercoagulable state

60. 2nd Year Pathology 2010
Arterial Thrombi
Occlusive thrombus in wall of atherosclerotic coronary artery

61. Consequences of Thrombosis
• Arterial Thrombosis
– Obstruction:
• Myocardial infarction due to coronary artery thrombosis
• Cerebral infarction (Stroke) due to carotid artery thrombosis
• Acute lower limb ischaemia & infarction due to femoral/popliteal artery
thrombosis
• Venous Thrombosis e.g. deep leg veins
– Obstruction:
• Local congestion, swelling, pain, tenderness
• Oedema and impaired venous drainage
– Infection & varicose ulcers

62. 2nd Year Pathology 2010
Fate of Thrombi
1. Dissolution
– by fibrinolysis
2. Propagation
– along length of vessel  complete vessel occlusion
3. Embolization
4. Recanalization
– capillaries invade thrombus to re-establish blood flow
5. Organization
– Inflammation and fibrosis  replacement by scar, may obliterate
vessel lumen
Recent thrombi may be completely dissolved
Older thrombi more resistent to fibrinolysis
(extensive fibrin polymerization)

63. 2nd Year Pathology 2010
Embolism
• Any intravascular mass (solid, liquid or gas) carried by
blood to site distant from point of origin
• Most derived from thrombi (thromboembolism)
• Lodge in vessels too small to permit further passage
– partial / complete vascular occlusion
– distal tissue ischaemia & infarction
• Arterial Thrombosis
• Cardiac/aortic mural thrombi  emboli to brain, kidneys, spleen

64. Atherosclerosis
• Plaques from atherosclerosis can behave in different ways.
• They can stay within the artery wall. There, the plaque
grows to a certain size and stops. Since this plaque doesn't
block blood flow, it may never cause symptoms.
• Plaque can grow in a slow, controlled way into the path of
blood flow. Eventually, it causes significant blockages. Pain
on exertion (in the chest or legs) is the usual symptom.
• The worst-case scenario consists of plaques that suddenly
rupture, allowing blood to clot inside an artery. In the brain,
this causes a stroke; in the heart, a myocardial infarction