1. The Cardiovascular System: The Heart18
P A R T A
The Cardiovascular System: The Heart

2. Approximately the size of your fist Location
Heart Anatomy
Approximately the size of your fist
Location
Superior surface of diaphragm
Left of the midline
Anterior to the vertebral column, posterior to the sternum

3. Heart Anatomy
Figure 18.1

4. Pericardium – a double-walled sac around the heart
Coverings of the Heart
Pericardium – a double-walled sac around the heart
Visceral layer (covers the heart)
Parietal layer (attached to the body wall)
Protects and anchors the heart
Prevents overfilling of the heart with blood
Pericardial cavity
Filled with serous fluid (pericardial fluid)
Allows for the heart to work in a relatively friction-free environment

5. Pericardial Layers of the Heart
Figure 18.2

6. Cardiac Muscle Bundles
Myocardium:
Forms the bulk of the heart wall
Figure 18.3

7. External Heart: Major Vessels of the Heart (Anterior View)
Vessels returning blood to the heart include:
Superior and inferior venae cavae
Right and left pulmonary veins
Vessels conveying blood away from the heart:
Pulmonary trunk, which splits into right and left pulmonary arteries
Ascending aorta (three branches) – brachiocephalic, left common carotid, and subclavian arteries

8. 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

9. External Heart: Major Vessels of the Heart (Posterior View)
Vessels returning blood to the heart include:
Right and left pulmonary veins
Superior and inferior venae cavae
Vessels conveying blood away from the heart include:
Aorta
Right and left pulmonary arteries

10. 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

11. Left anterior coronary artery – widow maker
Coronary Circulation
Coronary circulation is the functional blood supply to the heart muscle itself
Collateral routes ensure blood delivery to heart even if major vessels are occluded (blocked)
Left anterior coronary artery – widow maker
Damage to the left ventricle is most serious
Cardiac muscle is amitotic; cell death is repaired by noncontractile scar tissue

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. Coronary Circulation: Arterial Supply
Figure 18.7a

14. Coronary Circulation: Venous Supply
Figure 18.7b

15. 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

16. Atria of the Heart
Atria are the receiving chambers of the heart
Each atrium has a protruding auricle
Blood enters right atrium from superior and inferior venae cavae and coronary sinus
Blood enters left atrium from pulmonary veins

17. Ventricles of the Heart
Ventricles are the discharging chambers (pumps) of the heart
Right ventricle pumps blood into the pulmonary trunk
Left ventricle pumps blood into the aorta
Left ventricle wall is thicker – does more work

18. Right and Left Ventricles
Note the thickness
Figure 18.6

19. Pathway of Blood Through the Heart and Lungs
Inferior and superior vena cavae →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

20. Figure 18.5

21. Damage to Left Side of the Heart
Left ventricle is too weak to pump blood to the aorta so fluid accumulates in lungs.
Symptoms: dyspnea (shortness of breath) on exertion and in severe cases, dyspnea at rest. Easily fatigued and intolerant to exercise.
"Cardiac asthma" or wheezing may occur.
Treatment: Elevate head with pillows or sleep while sitting up. Also best to sleep on the right side.

22. Damage to Right Side of Heart
Right ventricle too weak to pump blood to the lungs so fluid accumulates in the body causing swelling (edema) in the feet, ankles, legs, liver, and abdomen.
Where the fluid accumulates depends on the amount of excess fluid and the effects of gravity.
Fluid accumulation in the liver or stomach can cause nausea and loss of appetite.
Treatment: Elevate legs

23. Heart Valves
Heart valves ensure unidirectional blood flow through the heart
Atrioventricular (AV) valves lie between the atria and the ventricles
AV valves prevent backflow into the atria when ventricles contract
Chordae tendineae anchor AV valves to papillary muscles

24. Heart Valves
Figure 18.8c, d

25. Atrioventricular Valve Function
Figure 18.9

26. Heart Valves
Aortic semilunar (SL)valve lies between the left ventricle and the aorta
Pulmonary semilunar valve lies between the right ventricle and pulmonary trunk
Semilunar valves prevent backflow of blood into the ventricles

27. Heart Valves
No chordae tendineae
Figure 18.8a, b

28. Semilunar Valve Function
Figure 18.10

29. Microscopic Anatomy of Heart Muscle
Cardiac muscle is striated, short, fat, branched, uninucleate and interconnected
Actin and myosin very greatly in diameter and are branched
25-35% of volume is mitochondria
Less extensive Ca++ ion delivery system: fewer and wider T tubules
Sarcoplasmic reticulum is simpler and lacks large terminal cisternae
Intercalated discs anchor cardiac cells together and allow free passage of electricity and ions between cells
Desmosomes act as door hinges
Gap junctions allow passage of electricity and ions

30. Cardiac Muscle Tissue Contraction
Contracts by the sliding filament mechanism
Absolute refractory period is 250 ms – nearly as long as the contraction to avoid tetany
Muscle cells are stimulated by the nervous system but some cells are self-excitable and can contract on their own (autorhythmicity): to keep a rhythm
Heart muscle behaves as a functional syncytium
The heart either contracts as a unit or not at all

31. Microscopic Anatomy of Cardiac Muscle
Figure 18.11

33. Microscopic Anatomy of Skeletal Muscle
Striated
Long, cylindrical, multinucleate muscle fibers
2% of the volume is mitochondria
Thin actin and thick myosin fibers uniform in size
and not branched
Very extensive Ca++ delivery via T tubules
Sarcoplasmic reticulum contains lg. terminal cisternae

34. Skeletal Muscle Contraction
Contracts by the sliding filament mechanism
Absolute refractory period is 1-2 ms; contraction lasts 15 – 100 ms
Muscle fibers act independently of one another (not interconnected)
Contract as a motor unit; not of an entire muscle
Each muscle fiber is stimulated by a nerve ending; not self-excitable

35. Microscopic Anatomy of Skeletal Muscle: Motor Unit

36. Microscopic Anatomy of Skeletal Muscle