The circulatory system consists of the heart and blood vessels. The heart is a four-chambered muscular pump made of cardiac muscle that is located between the lungs. It has two atria that receive blood and two ventricles that pump blood out. The heart is surrounded by membranes and has three layers: epicardium, myocardium, and endocardium. It receives blood through veins and pumps it through arteries via the pulmonary and systemic circuits. The heart also has valves that ensure one-way blood flow and septa that divide its chambers.

1. CIRCULATORY SYSTEM
CHONA ARAGA, MD.

4. CARDIOVASCULAR SYSTEM
BASIC DIVISIONS OF THE
CARDIOVASCULAR
1. Heart
– a muscular pump consisting two receiving
chamber (atria)two pumping chambers
(ventricles)
2. Two closed circuits of blood vessels:
a. pulmonary circuit
b. systemic circuit

5. Blood vessels
1. Arteries
2.Capillaries
3. Veins

6. HEART
- is a four-chambered, hollow, muscular organ
lying between the lungs in the middle
mediastinum.
- it is about the size of a man’s fist, and in the
normal male weighs approximately 250-300gm/
200-275gm.
- the heart is shaped like an inverted cone, with
its apex pointed downward and to the left base
upwards and to the right
- its apex anteriorly and inferiorly to the left
at 5th ICS,MCL

8. COVERING OF THE HEART
PERICARDIUM
- is an invaginated sac consisting of
1. Fibrous pericardium
- tough covering
- provide protection and anchors the
heart into mediastinum

9. Figure 12.3

10. Figure 12.4

11. 2. Serous pericardium
1. Parietal pericardium
- outer layer of the serous membrane
lines the fibrous coat.
2. Visceral pericardium
– inner layer of the serous membrane

12. Figure 12.12

13. WALLS OF THE HEART
- the wall of the heart consists of three
distinct layers:
1. epicardium
– external layer, the visceral layer of
the serous pericardium
2. myocardium
– middle muscular layer
3. endocardium
– inner layer of the endothelium

15. Chambers of the Heart
1. 2 Atria
3. 2. Ventricle

16. Figure 12.6

17. Valves of the Heart
1. Atrioventricular valves
a. Tricuspid valve
b. Mitral/Bicuspid valve
2. Semilunar valves
a. Aortic valve
b. Pulmonic valve

18. Figure 12.6

19. Septa
- are structures separating the chambers
3.Interatrial septum- separates the right
and left atrium
4.Interventricular septum- separates the
right and the left ventricles

20. Figure 12.6

21. CHAMBERS OF THE HEART
A. RIGHT ATRIUM ( right border of the
heart)
- receives the venous blood from the superior
vena cava, inferior vena cava, anterior cardiac
veins, vena cordis minimae and the coronary
sinus
- larger than left atrium
- with a right auricle on the external surface

23.  musculi pectinati
 crista terminalis
 Fossa ovalis
 Tricuspid opening
 Opening of Superior vena cava and
inferior vena cava

25. B. RIGHT VENTRICLE
(forming most of the anterior surface of the
heart)
- chamber of the heart receiving venous blood
from right atrium and ejecting this to the
pulmonary arteries
- thinner walled than left ventricle
- the infundibulum is the upper most part of the
wall which has no musculur bundles, leads into
pulmonary arteries.
- the lower portion and the rest of the wall of
the right ventricle are rough– trabeculae
carnae, papillary muscles

27. trabeculae carnae
- irregular muscular ridges probably to
hold more blood.
- when the ventricles contract they
arrange themselves to form a smooth
surface and effect a ventricular
evacuation.

29. papillary muscles
- conical in shape with the base attached
to the ventricular
wall and the apices receiving the end of
chordae tendinae

31. chordae tendinae
- thread-like structures connected to
the apices of the papillary muscles and
to the cusps of ventricular valves.

33. Moderator band (septomarginal band)
- a muscular band attached to septal
wall and to the anterior margin of right
ventricle
- prevents overdistention of the right
ventricle
- only present in the right ventricle.

34. C. LEFT ATRIUM ( base of the
heart)
- quadrilateral in shape and its interior
shows the openings of the four
pulmonary veins from the lungs.
- interior of the chamber is smooth
except in its auricular portion where the
musculi pectinati are found.
- blood leaves the left atrium and enters
the left ventricle via the left
atrioventricular orifice or mitral orifice.

36. D. LEFT VENTRICLE (where
apex of heart is found)
- cavity is longer and narrower than the
right and the walls are 3x thicker than
right ventricle
- the lower anterior part forms the apex of
the heart which is at the level of the 5th
left intercostal space midclavicular line
- the inner surface of the walls also
present muscular columns

38. BLOOD SUPPLY
OF THE HEART
- Coronary
arteries

39. Figure 12.4

40. VENOUS DRAINAGE OF THE
HEART
- This coronary sinus is the main venous
drainage of the heart.

41. Figure 12.5c

42. NERVE SUPPLY OF THE HEART
- derived from both the parasympathetic
(vagus)nerve which is inhibitory to the
heart and the sympathetic which is
excitatory to the heart.

44. IMPULSE CONDUCTING SYSTEM
OF THE HEART
1. Sinu-atrial node (Pacemaker of the heart)
- located at the posterior wall in the groove
between the superior vena cava and the right atrium
2. Atrio-ventricular node
- located at the lower part of the interatrial
septum
3. Bundle of His
- a pale bundle about the size of a match stick
located at the interventricular septum
- divides into a right and left bundle branch
4. Subendocardial network of Purkinje /Purkinje fibers

45. Figure 12.15

46. Heart Sounds
S1- first heart sound closure of the AV
valves
S2- closure of the semilunar valves
S3- ventricular gallop
S4- atrial gallop

47. Figure 12.16

48. P wave – represents atrial depolarization which
spreads from the SA node through
the contractible fibers in both atria
- small upward deflection
QRS complex – represents rapid
ventricular depolarization- as action
potential spreads through ventricular
contractile fibers
T wave – represents ventricular repolarization
occurs just as the ventricles are starting
to relax
- dome-shaped upward deflection

49. THANK YOU