1. Chapter 18
THE HEART

2. Approximately the size of the fist Extends:
Heart Anatomy
Approximately the size of the fist
Extends:
From 2nd rib to 5th intercostal space
Location:
Rests on superior surface of diaphragm
Anterior to the vertebral column
Posterior to the sternum
2/3 lies left to the midsternal line
Flanked by left & right lungs

3. Heart Anatomy & Location
Figure 18.1

4. Coverings of the Heart: Anatomy
Pericardium:
A double-walled sac around the heart
Composed of:
A superficial fibrous pericardium
A deep two-layer serous pericardium with:
A parietal layer lining the internal surface of the fibrous pericardium
A visceral layer (epicardium) lining the surface of the heart
A fluid-filled pericardial cavity between the two layers

5. Coverings of the Heart: Physiology
The pericardium:
Protects the heart
Anchors the heart to its surrounding structures
Prevents overfilling of the heart with blood
Allows for a relatively friction-free working environment for the heart

6. Pericardial Layers of the Heart
Figure 18.2

7. Fibrous skeleton of the heart:
Heart Wall Layers
Epicardium:
Visceral layer of the serous pericardium
Myocardium:
Cardiac muscle layer forming the bulk of the heart
Arranged in circular or spiral bundles
Fibrous skeleton of the heart:
Crisscrossing, interlacing layer of connective tissue
A network of collagen & elastic fibers (reinforcement)
Endocardium:
Thin endothelial layer of the inner myocardial surface

8. Cardiac Muscle Bundles
Figure 18.3

9. Major Vessels of the Heart (Anterior View)
Vessels returning blood to the heart include:
Superior vena cava:
Returns venous blood from upper region (above diaphrag.)
Inferior vena cava:
Returns venous blood from lower region (below diaphrag.)
Coronary sinus:
Returns venous blood from the myocardium
Right pulmonary veins:
Returns venous blood from the right lung
Left pulmonary veins:
Returns venous blood from the left lung

10. interventricular artery (in anterior interventricular sulcus) Inferior
Left common
carotid artery
Brachiocephalic
trunk
Left
subclavian artery
Superior
vena cava
Aortic arch
Right
pulmonary artery
Ligamentum
arteriosum
Ascending
aorta
Left pulmonary artery
Left pulmonary veins
Pulmonary trunk
Left atrium
Right
pulmonary veins
Auricle
Right atrium
Circumflex
artery
Right coronary
artery (in coronary
sulcus)
Left coronary
artery (in coronary
sulcus)
Anterior
cardiac vein
Left ventricle
Right ventricle
Great cardiac vein
Marginal artery
Small cardiac vein
Anterior
interventricular artery
(in anterior
interventricular sulcus)
Inferior
vena cava
(b)
Apex
Figure 18.4b

11. Major Vessels of the Heart (Anterior View)
Vessels conveying blood away from the heart:
Pulmonary trunk: splits into two branches:
Right pulmonary artery
Left pulmonary artery
Ascending aorta: gives three branches:
Brachiocephalic artery
Left common carotid artery
Subclavian artery

12. interventricular artery (in anterior interventricular sulcus) Inferior
Left common
carotid artery
Brachiocephalic
trunk
Left
subclavian artery
Superior
vena cava
Aortic arch
Right
pulmonary artery
Ligamentum
arteriosum
Ascending
aorta
Left pulmonary artery
Left pulmonary veins
Pulmonary trunk
Left atrium
Right
pulmonary veins
Auricle
Right atrium
Circumflex
artery
Right coronary
artery (in coronary
sulcus)
Left coronary
artery (in coronary
sulcus)
Anterior
cardiac vein
Left ventricle
Right ventricle
Great cardiac vein
Marginal artery
Small cardiac vein
Anterior
interventricular artery
(in anterior
interventricular sulcus)
Inferior
vena cava
(b)
Apex
Figure 18.4b

13. Vessels that Supply/Drain the Heart (Anterior View)
Arteries: (located in the atrioventricular groove):
Left coronary artery: its major branches:
Anterior interventricular artery
Circumflex artery
Right coronary artery: its major branches:
Posterior interventricular artery
Marginal, artery

14. interventricular artery (in anterior interventricular sulcus) Inferior
Left common
carotid artery
Brachiocephalic
trunk
Left
subclavian artery
Superior
vena cava
Aortic arch
Right
pulmonary artery
Ligamentum
arteriosum
Ascending
aorta
Left pulmonary artery
Left pulmonary veins
Pulmonary trunk
Left atrium
Right
pulmonary veins
Auricle
Right atrium
Circumflex
artery
Right coronary
artery (in coronary
sulcus)
Left coronary
artery (in coronary
sulcus)
Anterior
cardiac vein
Left ventricle
Right ventricle
Great cardiac vein
Marginal artery
Small cardiac vein
Anterior
interventricular artery
(in anterior
interventricular sulcus)
Inferior
vena cava
(b)
Apex
Figure 18.4b

15. Vessels that Supply/Drain the Heart (Anterior View)
Veins: (all empty in the coronary sinus):
Great cardiac
Middle cardiac
Small cardiac
Anterior cardiac veins
Posterior vein of the left ventricle

16. interventricular artery (in posterior interventricular sulcus)
(d)
Superior
vena cava
Right
pulmonary artery
pulmonary veins
Right atrium
Right coronary
artery (in coronary
sulcus)
Right ventricle
Coronary sinus
Middle cardiac vein
Left
Left atrium
Auricle
of left atrium
Left ventricle
Posterior vein
of left ventricle
Posterior
interventricular artery
(in posterior
interventricular sulcus)
Great cardiac vein
Apex
Inferior
Aorta
Figure 18.4d

17. Aorta Superior vena cava Left Right pulmonary artery pulmonary artery
Left atrium
Pulmonary trunk
Left
pulmonary veins
Right atrium
Right
pulmonary veins
Mitral
(bicuspid) valve
Fossa
ovalis
Aortic
valve
Pectinate
muscles
Pulmonary
valve
Tricuspid
valve
Left ventricle
Papillary
muscle
Right ventricle
Chordae
tendineae
Interventricular
septum
Myocardium
Trabeculae
carneae
Visceral
pericardium
Inferior
vena cava
Endocardium
(e)
Figure 18.4e

18. Atria are the receiving chambers of the heart
Atria of the Heart
Atria are the receiving chambers of the heart
Each atrium has a protruding auricle (volume increase )
Pectinate muscles mark right atrial anterior walls
Right atria receive blood from:
Superior vena cava
Inferior vena cava
Coronary sinus
Left atria receive blood from:
pulmonary veins (four)

19. Ventricles of the Heart
Ventricles are the discharging chambers of the heart
Papillary muscles and trabeculae carneae muscles mark ventricular walls
Right ventricle pumps blood into the pulmonary trunk
Left ventricle pumps blood into the aorta

20. Right and Left Ventricles
Figure 18.6

21. Pathway of Blood Through the Heart & Lungs
Right atrium  tricuspid valve  right ventricle
Right ventricle  pulmonary semilunar valve  pulmonary arteries  lungs
Lungs  pulmonary veins  left atrium
Left atrium  bicuspid valve  left ventricle
Left ventricle  aortic semilunar valve  aorta
Aorta  systemic circulation
Aorta  coronary artery  coronary circulation

22. Figure 18.5

23. Coronary circulation:
The functional blood supply to the heart muscle itself
Collateral routes:
Ensure blood delivery to heart
Even if major vessels are occluded
Ex. Bypass surgery

24. Coronary Circulation: Arterial Supply
Figure 18.7a

25. Coronary Circulation: Venous Supply
Figure 18.7b

26. Atrioventricular (AV) valves:
Heart Valves
Heart valves:
Ensure unidirectional blood flow through the heart
Atrioventricular (AV) valves:
Lie between atria and ventricles
Prevent backflow into atria when ventricles contract
Tricuspid (between right atrium & right ventricle)
Bicuspid /Mitral (between leftt atrium & left ventricle)
Chordae tendineae:
Collagenous fibers
Anchor AV valves to papillary muscles

27. Aortic semilunar valve:
Heart Valves
Semilunar valves:
lie between ventricles and major vessels
prevent backflow of blood into the ventricles
Aortic semilunar valve:
lies between the left ventricle and the aorta
Pulmonary semilunar valve:
lies between the right ventricle and pulmonary trunk
No valves in superior & inferior venae cavae

28. Heart Valves
Figure 18.8a, b

29. Heart Valves
Figure 18.8c, d

30. Atrioventricular Valve Function
Figure 18.9

31. Semilunar Valve Function
Figure 18.10

32. Microscopic Anatomy of Heart Muscle
Cardiac muscle is:
Striated, uninucleate
Short & fat
Branched & interconnected
The connective tissue endomysium acts as both tendon and insertion
Intercalated discs:
Anchor cardiac cells together
Allow free passage of ions
Heart muscle behaves as a functional syncytium (unit)
PLAY

33. Microscopic Anatomy of Cardiac Muscle
Figure 18.11