The cardiovascular system includes the heart and blood vessels. The heart has four chambers and lies within the thoracic cavity. It is surrounded by membranes and has three layers: epicardium, myocardium, and endocardium. The heart has four valves that ensure one-way blood flow. Blood flows from the sinoatrial node through the conduction system. The cardiovascular system is regulated through neural and hormonal mechanisms to control blood pressure and blood flow through the body.

1. THE CARDIOVASCULAR
SYSTEM
REVISION OF CARDIOVASCULAR ANATOMY
AND PHYSIOLOGY
BY. Dr Kifle Alamirew(MD)
1

2. CARDIOVASCULAR ANATOMY AND
PHYSIOLOGY
Cardio Vascular
System: Includes the
heart and blood
vessels( arteries, veins,
arterioles, veinules and
capillaries).
2

3. THE HEART
 rests on the diaphragm
 near the midline of the thoracic cavity
3

4. LAYERS OF THE HEART WALL
4

5. PERICARDIUM
confines heart to the
mediastinum
allows sufficient freedom
of movement.
consists of two layers:the
fibrous and serous.
5

6.  FIBROUS : thin inelastic, dense irregular connective
tissue
---helps in protection, anchors heart to mediastinum
 SEROUS: thinner, more delicate divided into parietal
and visceral
-forms closed sac of the pericardial cavity 6

7.  EPICARDIUM: composed of mesothelium and delicate
connective tissue (imparts a slippery texture to the outer
surface of the heart).
7

8.  MYOCARDIUM:responsible for pumping
 ENDOCARDIUM: thin layer of endothelium which is
continous with the lining of the large blood vessels
attached to the heart.
8

9. CHAMBERS OF THE HEART
9

10. HEART VALVES
 Semilunar valves: pulmonic
and aortic valve
 Atrioventricular valves:
tricuspid and mitral valve
10

11. BLOOD SUPPLY OF THE HEART
11

12. CONDUCTION SYSTEM OF THE HEART
 inherent and rhythmical beat is
due to autorhythmic fibers of the
cardiac muscle.
 these fibers have 2 important
function
- act as pace maker
- form the conduction system
12

13. CONT’D……
 There is a hierarchy of automaticity within
the tissue of the heart.
 The tissue that possesses the greatest
degree of automaticity (e.g., has the fastest
rate of spontaneous depolarization)
functions as the dominant pacemaker; it
generates a spontaneous action potential
 Normally the pacemaker is SA node.
 AV node is the only connection between atrium and
ventricle
 Impulse is delayed at AV node.
13

14. CONT’D…
 SA node would initiates action potential about
every 0.6 sec or 100 times/min
 the ANS alters the strength and timing of heart
beats
 Depolarization from endocardium to epicardium
and for repolarization the reverse is true
 The conduction system of the heart could be
assessed by ECG.
14

15. PHYSIOLOGIC CHARACTERISTICS
OF THE CONDUCTION CELLS
automaticity
excitability
conductivity
rhythmicity
contractility
15

16. PHASE OF ACTION POTENTIAL
 Phase 0: is the up stroke of the action
potential and is caused by a transient increase
in Na+ conductance.
 Phase 1: is a brief period of intial
depolarization and is as a result of movement
of K+ ions out of the cell and a decreased Na+
conductance.
 Phase 2: is the plateau of the action potentia
and is generated by a balance of repolarizing
potassium currents and depolarizing calcium
current.
 Phase 3: repolarization (Ca2+ conductance
decreases and K+ conductance increases)

16

17. PHASES OF ACTION POTENTIAL (VENTRICLES, ATRIA
, BUNDLE OF HIS, BUNDLE BRANCHES AND THE
PURKINJE SYSTEM)
17

18. CARDIAC CYCLE
18

19. HEART SOUNDS
 produced from blood
turbulence caused by closing of
heart valves
 s1 – atrioventricular valve
closure
 s2 – semilunar valve closure
 s3 – rapid ventricular filling
 s4 – atrial systole
19

20. CARDIAC OUTPUT
 CO = SV X HR
 FOR A RESTING ADULT
CO = 70mL/beat x75beats/min
= 5250 mL/min
= 5.25 L/min
mL/min mL/beat (Beats/min)
20

21. REGULATION OF STROKE VOLUME
 three factors regulate stroke volume
-preload
-contractility
-afterload
21

22. PRELOAD
 stretch of cardiac muscle prior to
contraction(length of the muscle at the
end of diastole).
 Frank-Starling’s law , it says with
limit the force of contraction depend
on end diastolic length of the cardiac
muscle.in intact heart the later is
propotional to ventricular end
diastolic volume
 if HR is more than 160 beats/min
stroke volume declines due to short
filling time.
 Increase in preload increases SV
22

23. FACTORS AFFECTING THE
PRELOAD
23

24. CONTRACTILITY
 it is the strength of contraction at any
given preload.
 positive and negative ionotropics.
 stimulation of sympathetic division of
ANS leads to positve ionotropic effect
 inhibition of sympathetic division of ANS
leads to negative ionotropic effect
24

25. CONT’D…..
25

26. AFTERLOAD
 the pressure that must
be overcome before a
semilunar valve can
open is termed the
afterload.
 increase in afterload
cause decrease in
stroke volume
 HTN and
Atherosclerosis
increases the
afterload.
26

27. REGUALTION OF HEART RATE
 SA node initiates 100
beats/min if left to itself.
 tissue require different
volume of blood flow under
different conditions(ex:
exercise)
 ANS and hormones of adrenal
medulla are important in
regulating the heart rate.
27

28. AUTONOMIC REGULATION OF
HEART RATE
INPUT TO
CARDIOVASCULAR
CENTRE
SYMPATHETIC
NEURONS EXTEND
FROM MEDULLA
OBLANGATA
THE SPINAL CORD
(thoracic region)
HIGHER BRAIN CENTER:
cerebral cortex, lymbic system,
hypothalamus
SENSORY RECEPTORS:
Proprioreceptors,
chemoreceptors, baroreceptors.
CARDIAC ACCELERATOR
NERVE EXTENDS TO SA,
AV NODES
TRIGERS NOR-
EPINEPHRINE
28

29. NOR-EPINEPHRINE
has 2 effects
- in SA node, speeds the rate of spontaneous
depolarization
-in AV node, increases contractility
increases stroke volume
29

30. PARASYMPATHETIC EFFECT
parasympathetic nerve reaches the heart via left vagus (x)
nerves
they release acetyl choline,
which decreases the heart rate
at rest parasympathetic stimulation predominates
30

31. CHEMICAL REGULATION OF HEART
RATE
 hormones: epinephrine and norepinephrine,
throid hromone also increases heart rate
 cations: elevated K+ and Na+ decreases heart
rate, moderate increase in interstitial Ca+ levels
speeds heart rate.
31

32. OTHER FACTORS IN HEART RATE
REGULATION
 age
 gender physical fitness
 body temperature
32

33. BLOOD VESSELS
Vascular ultrastructure
Different in different vessels
Trilaminar (three layers)
 Intima(endothelial cells)
 Tunica media
 Adventitia
33

34. HEMODYNAMIC AFFECTING
BLOOD FLOW
 blood pressure
 resistance
 venous return
34

35. BLOOD PRESSURE
 during systemic circulation, blood pressure falls as the
distance from the left ventricle increases
 MAP = diastolic pressure +
1/3 (sys pressure – diastolic pressure)
35

36. VASCULAR RESISTANCE
 it is the oppostion to blood flow due to friction
between blood and the walls of blood vessels.
 Depends on:
 size of the lumen-
R is inversely propotional to 1/d
 blood viscosity
 total blood vessel length
4
36

37. VENOUS RETURN
depends on
 heart contraction
 pressure in the Right atrium
besides this
 skeletal muscle pump
 respiratory pump
37

38. CONTROL OF BLOOD
PRESSURE AND
BLOOD FLOW
38

39. ROLE OF CARDIOVASCULAR
CENTRE
 proprioreceotors
 baroreceptors
 chemoreceptors
39

40. NEURAL REGULATION 0F BLOOD
PRESSURE
 baroreceptors
 chemoreceptors
40

41. BARORECEPTORS pressure sensitive located
in the aorta, internal
carotid and other large
arteries.
 2 important baroreceptor
reflex are
- carotid sinus reflex
- aortic reflex
41

42. CHEMORECEPTOR REFLEX
present close to the
- baroreceptors of carotid sinus and arch of aorta
- they are called carotid bodies and aortic bodies.
42

43. HORMONAL REGULATION OF
BLOOD PRESSURE
 renin angiotensin-aldosterone mechanism
 epinephrine and nor epinephrine
 antidiuretic hormone
 atrial natriuretic peptide
43

44. AUTOREGULATION OF BLOOD
PRESSURE
 abilty of tissue to automatically
adjust its blood flow to match its
metabloic demand
is called autoregulation. mainly during
exercise.
44

45.  two type of stimuli causes autoregulatory changes
- physical changes
- vasodilating and vasoconstricting chemicals
45

46. PHYSICAL CHANGES
 warming and cooling causes vasodilation and
vasoconstriction respectively.
 smooth muscle in arteriole exhibit myogenic response
46

47. VASODILATING AND VASOCONSTRICTING
CHEMICALS
 several cells release a wide variety of chemicals
that alter the blood vessel diameter
 vasodilators - +, H+, Lasctic acid and adenosine
and mainly No
 vasoconstrictors – Thrombaxane A2 , serotonin and
endothelins
47

48. CARDIAC METABOLISM
Heart needs continuous supply energy
Use 15% of that of entire body
Glucose (feeding state and ionotropic agent)
and free fatty acid(fasting state(70%) and
stress)
Ischemia and stress end up with free fatty acid
accumulation
FFAs is arrhythmogenic.
48