1. Anatomy and Physiology
Marieb’s Human
Anatomy and Physiology
Ninth Edition
Marieb w Hoehn
Chapter 18
Heart
Lecture 2
Slides 1-15; 80 min (with review of syllabus and Web sites) [Lecture 1]
Slides 16 – 38; 50 min [Lecture 2]
118 min (38 slides plus review of course Web sites and syllabus)

2. Lecture Overview Location of the heart Structure of the heart
Blood flow through the heart
Angina Pectoris and Myocardial Infarction
Cardiac Conduction System

3. Overview of the Cardiovascular System (CVS)
CVS = Heart + Blood Vessels
Figure from: Hole’s Human A&P, 12th edition, 2010

4. Introduction to the Heart
Average Size of Heart
14 cm long
9 cm wide
about 300 g
Cardiology is the study of the heart and the diseases associated with it
Heart pumps enough blood in one day to fill 40, 55-gallon drums!!
Figure from: Hole’s Human A&P, 12th edition, 2010

5. Location of Heart posterior to sternum
medial to lungs (in middle mediastinum
anterior to vertebral column
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

6. Position of heart changes with height/weight
Location of Heart
Figure from: Hole’s Human A&P, 12th edition, 2010
base lies beneath 2nd rib
apex at 5th intercostal space
lies upon (and attached to) diaphragm
Notice that:
- Center of base lies slightly to the left of midline
- Long axis of heart points slightly left
- heart is rotated around long axis to left (more of right side is anterior
Position of heart changes with height/weight

7. Coverings of Heart
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001
Fibrous pericardium = pericardial sac (outermost layer)

8. Wall of Heart Three layers endocardium myocardium epicardium
Figure from: Hole’s Human A&P, 12th edition, 2010
Three layers
endocardium
forms protective inner lining
membrane of epithelial and connective tissues
myocardium
cardiac muscle
contracts to pump blood
epicardium
serous membrane (visceral pericardium)
protective covering
contains capillaries and nerve fibers
Know all the layers depicted in the diagram, and know their correct order.

9. Chambers of Heart
Atria are thin-walled chambers that receive blood passively from large veins
Moderator band = septomarginal trabecula. Its main function is to convey the right branch of the atrioventricular (AV) bundle (of His) of the conducting system.
The septomarginal trabecula forms the anteroinferior border between the superior, smooth outflow tract of the ventricle and the trabeculated inflow tract. At its septal attachment, it may be continuous with the supraventricular crest.
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

10. Heart valves ensure one-way flow of blood through the heart
Atrioventricular (AV) valves
Tricuspid Valve
right A-V valve
between right atrium and right ventricle
Attached to chordae tendineae
Bicuspid (Mitral) Valve
left A-V valve
between left atrium and left ventricle
Attached to chordae tendineae
Semilunar valves
Pulmonary Valve
semilunar valve
between right ventricle and pulmonary trunk
Aortic Valve
semilunar valve
between left ventricle and aorta

11. Heart Valves
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001
About 70% of blood will flow passively into the ventricles before the atria contract

12. Heart Valves
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

13. Heart Valves Which chambers are contracting in this picture? Anterior
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001
Which chambers are contracting in this picture?
Anterior

14. Heart Valves Which chambers are contracting? Anterior
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001
Which chambers are contracting?
Anterior

15. Coronal Sections of Heart
Figure from: Hole’s Human A&P, 12th edition, 2010
Connection between right ventricle and pulmonary trunk

16. Coronal Sections of Heart
Figure from: Hole’s Human A&P, 12th edition, 2010
Connection between left ventricle and aorta

17. Heart Valves Pulmonary and Aortic Valve Tricuspid Valve
Figures from: Hole’s Human A&P, 12th edition, 2010

18. Skeleton of Heart fibrous rings to which the heart valves are attached
masses of dense CT in interventricular septum
Figure from: Hole’s Human A&P, 12th edition, 2010
Skeleton of heart:
Holds valves/vessels in place
Electrically separates the atria from the ventricles
(Bicuspid)

19. Path of Blood Through the Heart
Figure from: Hole’s Human A&P, 12th edition, 2010

20. Pathway of Blood Through Heart
Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007
Know This! (after correcting the one mistake…  )

21. Blood Supply to Heart (Coronary circulation)
Anastamoses = connections between 2 or more branches of arteries that supply the same region with blood.
Give rise to collateral circulation
(LAD)
Blood flow through coronary arteries takes place mainly during relaxation of the ventricles (ventricular diastole)
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

22. Blood Supply to Heart
Cardiac veins join at an enlargement called the coronary sinus that drains into the right atrium
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

23. Coronary Circulation (LAD)
Figure from: Hole’s Human A&P, 12th edition, 2010
(LAD)

24. Angina Pectoris and Myocardial Infarction
Ischemia = reduction of blood flow
Hypoxia = reduced supply of O2
Angina Pectoris = severe pain that accompanies myocardial ischemia
Myocardial Infarction (MI) = heart attack
Reperfusion Damage
Previously hypoxic tissue is re-supplied with O2
O2 free radicals cause tissue damage
Anti-oxidants may defend against this

25. Angiogram of Coronary Arteries
In traditional angiography, we acquire images of blood vessels on films by exposing the area of interest with time-controlled x-ray energy while injecting contrast medium into the blood vessels. The images thus obtained would also record other structure besides blood vessels as the x-ray beam passes through the body. In order to remove these distracting structures to see the vessels better, we need to acquire a mask image for subtraction. The mask image is simply an image of the same area without contrast administration. So, using manual darkroom technique, clear pictures of blood vessels are obtained by taking away the overlying background.
In DSA, the images are acquired in digital format through the computer. With the help of the computer, all images would be recorded into the computer and subtracted automatically. As a result, we can have a near-instantaneous film show of the blood vessels alone after x-ray.
(Digital Subtraction Angiography)
Figures from: Martini, Anatomy & Physiology, Prentice Hall, 2001

26. Systole and Diastole Systole = contraction; Diastole = relaxation
Atrial Systole/Ventricular Diastole
Atrial Diastole/Ventricular Systole
Figure from: Hole’s Human A&P, 12th edition, 2010

27. Systole and Diastole
Atrial Systole/Ventricular Diastole (Contraction of both atria)
before atrial systole, blood flows passively into ventricles (~ 70%)
remaining 30% of blood pushed into ventricles during atrial systole
A-V valves open/semilunar valves close
ventricles are relaxed and are filling with blood
ventricular pressure begins to increase
Ventricular Systole/Atrial Diastole (Contraction of both ventricles)
A-V valves close
chordae tendinae prevent cusps of valves from bulging too far into atria
atria relaxed; low pressure allows blood return from veins
blood flows into atria
ventricular pressure increases and opens both semilunar valves
blood flows into pulmonary trunk and aorta

28. Cardiac Cycle - Overview
Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007
Pressure  Quantity of fluid
Volume of container

29. Cardiac Cycle Filling of coronary vessels occurs mainly here
Figure from: Hole’s Human A&P, 12th edition, 2010
Mercury is used in manometers because it is more dense (13.5 g/cc) than water (1.0 g/cc) so the evacuated column can be shorter. Pressure is there expressed in mm Hg. Normal atmospheric pressure is 760 mm Hg (1034 cm H2O)
Filling of coronary vessels occurs mainly here

30. Cardiac Cycle See Fig. 18.21 in Marieb
S3 normal in children and adolescents but not normally heard in adults (older than about 30). When it’s heard, it is considered pathologic and associated with ventricular dilation and too rapid filling of the ventricles.
S4 may be heard during atrial contraction (vibration of ventricular wall) due to stiffening of ventricles and is commonly present in older individuals. This results from conditions in which the atria have to contract very strongly to inject blood into the ventricles.
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

31. Cardiac Cycle
Figure from: Hole’s Human A&P, 12th edition, 2010

32. Heart Sounds Lubb first heart sound
occurs during ventricular contraction (systole)
A-V valves closing
Dupp
second heart sound
occurs at the end of ventricular contraction (diastole)
semilunar valves closing ♥
Murmur – abnormal heart sound

33. Cardiac Muscle Fibers
Cardiac muscle fibers form functional syncytium - group of cells that function as a unit
atrial syncytium
ventricular syncytium
Separate units that are:
1) separated by the cardiac skeleton
2) connected by fibers of the cardiac conduction system

34. Muscle Fibers in Ventricular Walls
Figure from: Hole’s Human A&P, 12th edition, 2010

35. Cardiac Conduction System
Figure from: Hole’s Human A&P, 12th edition, 2010
Specialized myocardial cells.
Instead of contracting, they initiate and distribute impulses throughout the heart.
S-A node = Pacemaker
Cardiac conduction system allows rapid, organized, near-synchronized depolarization and contraction of cardiac myocytes.
Normally, impulses from SA node are conducted cell-to-cell within the atria (~ 0.5 m/s) through gap junctions in intercalated disks. Since cardiac skeleton separates atria from ventricles, the cell-to-cell propagation does not continue to ventricular cardiocytes; these must be depolarized by the cardiac conduction system (AV node, AV bundle, bundle branches [~ 2 m/s], Purkinje fibers [~ 4 m/s]). A
AV node highly specialized cardiocyte conducting tissue (~ 0.05 m/s), and relies on slow inward Ca flow for depolarization (sensitive to changes in Ca conductance). Slow conduction and delay is important in giving the atria time to empty, the ventricles time to fill more completely, and preventing excessive impulses during atrial flutter and fibrillation that might lead to ventricular tachycardia and reduced CO. Extrinsic factors that can alter conduction: ANS activity, hormones (esp. catecholamines), and drugs (by acting on ion channels or by influencing ANS activity).
Pacemaker firing rates:
SA Node – / min
AV Node – / min
Purkinje – / min

36. Cardiac Conduction Pathway
Figure from: Hole’s Human A&P, 12th edition, 2010
Know the sequence of this pathway
(of His)

37. Review The heart is located in the mediastinum The heart is covered by
Anterior to the vertebral column
Posterior to the sternum
Between the lungs
Between the level of the 2nd (base) and 5th (apex) ribs
More prominent on the left side of the sternum
The heart is covered by
Fibrous pericardium (tough, dense CT)
Parietal pericardium
Visceral pericardium
Pericardial cavity

38. Review The heart wall is composed of three layers
Epicardium (= visceral pericardium)
Myocardium (muscle)
Endocardium (continuous with endothelium of blood vessels)
The heart has four chambers
2 atria (thin-walled, low pressure)
2 ventricles (thicker-walled, higher pressure)
Atria and ventricles have valves between them
Ensure one-way flow of blood through the heart
AV valves = tricuspid and bicuspid (mitral)
Semilunar valves = pulmonary and aortic

39. Review Arteries carry blood away from heart
Pulmonary arteries (low O2, high CO2)
Aorta
Coronary arteries
Veins carry blood to the heart
Superior and inferior vena cava
Pulmonary veins (high O2, low CO2)
Coronary veins/sinus

40. Review Recall pathway of blood (need to know!)
Pulmonary circuit
Systemic circulation
Coronary circulation
Consequences of compromised coronary blood flow
Ischemia
Hypoxia
Angina Pectoris
Myocardial infarction
Reperfusion damage
**Prior to next lecture, STUDY Fig in Martini or Fig in Hole.

41. Review Cardiac conduction system Specialized myocardial cells
Conduct rather than contract
Autorhythmic (self-exciting)
S-A node is pacemaker of heart ( bpm)
A-V node ( bpm)
Delays impulse to allow ventricular filling
Located in interventricular septum
A-V Bundle (Bundle of His)
Only electrical connection between atria and ventricles
Give rise to right and left bundle branches
Purkinje fibers
Large diameter, rapid conduction for ventricles
Causes apex to contract first, then toward base