1. The Cardiovascular System: The Heart
Chapter 21 Lecture
Chapter 21
The Cardiovascular System: The Heart
Frederic Martini
Michael Timmons
Robert Tallitsch

2. The blood must stay in motion to maintain homeostasis.
Introduction
The blood must stay in motion to maintain homeostasis.
The heart keeps blood moving.
The volume of blood pumped by the heart can vary widely, between 5 and 30 liters per minute.

3. An Overview of the Cardiovascular System
The heart is a small organ; it is roughly the size of a clenched fist.
The heart has four muscular chambers:
Right and left atria
Right and left ventricles

4. Fig
21.6

5. An Overview of the Cardiovascular System
[Insert fig 21.1]
Figure The Pulmonary and Systemic Circuits

6. Orientation of the Heart
Figure Position of the Heart

7. The Pericardium
Figure 21.2a,b The Location of the Heart in the Thoracic Cavity

8. The Pericardium
Figure 21.2c The Location of the Heart in the Thoracic Cavity

9. The Pericardium
Figure 21.2d The Location of the Heart in the Thoracic Cavity

10. Epicardium/visceral pericardium
The heart wall
Parietal pericardium
Epicardium/visceral pericardium
Myocardium-cardiac muscle tissue
Endocardium-
epithelia tissue
Fig
21.3

11. Intercalated discs & gap junctions
Intercalated discs hold adjacent cardiac muscle cells together
Cells work together during contraction
Mechanically links cells together
Gap junctions allow ions to pass from cell to cell
Electrical stimulation in one cell can pass directly into other cells
Electrically/chemically links cells together
Cardiac muscle cells work as a well organized unit

12. Structure of the Heart Wall
Figure 21.3c-e Cardiac Muscle Tissue

13. Fig
21.5

14. Fig
21.5

15. Fig
21.6

16. Internal Anatomy and Organization of the Heart
Figure 21.6d Horizontal Section of Heart

17. Heart valves allow blood to flow only in one direction thru the heart
Atrioventricular valves (AV)-between an atrium and ventricle
rt. atrium>Rt. AV (tricuspid) valve>rt. ventricle
lt. atrium>Lt. AV (bicuspid/mitral) valve>lt. ventricle

18. The Structure and Function of Heart Valves
Figure 21.7a Valves with Ventricles Relaxed

19. Semilunar valves-between the ventricle & an artery
lt. ventricle>Aortic semilunar valve>aorta
rt. ventricle>Pulmonary semilunar valve>pulmonary artery

20. The Structure and Function of Heart Valves
Figure 21.7b Valves with Ventricles Contracted

22. Coronary Circulation Figure 21.9a Anterior Heart
Figure 21.9b Posterior Heart

23. Pulmonary circuit Systemic circuit - from heart to lungs back to heart
to body
back to heart

24. Atria vs. ventricles
Blood enters the heart via atria
Atria have thinner walls than ventricles
Atria pump blood to the ventricles
Ventricles pump blood thru the pulmonary and the systemic circuit

25. Right vs. Left ventricle
Fig 21.6
The left Ventricle has a much thicker myocardium

26. Heart sounds The two heart sounds are: “Lub”-AV valves closing
“Dub”-semilunar valves closing
Aortic-2nd intercostals space (Right side)
Pulmonary- 2nd ICS (Left side)
Right AV valve- 5th ICS (Right of sternum)
Left AV valve- 5th ICS (inferior to left nipple)

27. Heart Valves and Heart Sounds
Closure of the AV valves create the 1st heart sound (‘lub’).
Closure of the semilunar valves create the 2nd heart sound (‘dub’).
Placement of a stethoscope varies depending on which heart sounds and valves are of interest.

28. The cardiac cycle
A chamber of the heart can be in one of two phases:
Systole-contraction of the muscle, ejecting blood out of the chamber
Diastole-relaxation of the muscle, the chamber fills with blood
The heart pumps by using cycles of systole and diastole

29. Systole: contraction phase Diastole: relaxation phase
Cardiac Cycle
Systole: contraction phase
Diastole: relaxation phase
Mid-to-late diastole .
dub
lub
Cardiac cycle is a complete heartbeat.
Consists of 2 phases: systole and diastole, defined as whether the ventricles are contracting or relaxing.
During the cycle, valves open and close, producing the familiar “lub-dub” sound.
Go to Cardiac Cycle layered slide
Diastole: ventricles relax, blood passively moves in and contraction of atria “tops off” the ventricles.
Systole: ventricles contract-increasing pressure in ventricle closes the atrioventricular valves (lub), and opens the pulmonary and aortic valves.
Ventricles begin to relax: pressure decreases and pul. and aortic valves close (dub).
Pressure in aorta increase during systole, and falls somewhat during diastole: aorta elastically recoils, causing backpressure that closes the aortic valve.
Valve video?
Early diastole
Ventricular
systole

30. Nodal cells spontaneously depolarize causing an action potential
Two groups of nodal cells:
Sinoatrial (SA) node-makes AP/min
Primary pacemaker
Posterior wall of the rt. atrium
Atrioventricular AV node-slower than SA node
Secondary pacemeker
Inferior region of the rt. Atrium wall

31. Figure The Heartbeat
From AV node, action potentials are conducted to ventricles down through fibers called Bundle of His.
The fibers branch to tips of left and right ventricles and spread throughout the ventricles as Purkinje fibers.
Purkinje fibers spread the action potential rapidly and evenly throughout the ventricles.
The AV fires after a short delay to ensure that the atria contract first, so that blood passes progressively from the atria to the ventricles to the arteries.

32. Electrical Conduction System
1. Sino Atrial (SA) Node
2. Atrial Ventricular (AV) Node
3. AV Bundle (Bundle of His)
4. L and R Bundle Branches
5. Purkinje Fibers

33. The Cardiac Cycle
Figure The Cardiac Cycle

34. Fig 21.12
The electrical signal stimulates contraction of the chambers

35. Figure 49.4 The Cardiac Cycle
Right
atrium
Left
atrium
Left
ventricle
Right
ventricle
Ventricle
contracting
Ventricle
relaxing
P (mm Hg)
V (ml)
Pressure in left ventricle
Left ventricular volume
Pressure in aorta

36. EKG-electrocardiogram
Surface electrodes can monitor the depolarization of the nodal and conducting fibers
EKG graph gives electrical and mechanical diagnostic information

37. Figure The ECG

39. The Autonomic Innervation of the Heart
The stimulus for contraction is generated by pacemaker cells of the SA node.
Modified by the ANS
Modified by Hormones

40. Autonomic Control of Heart Rate
Basic rate established by pacemaker cells that inside the heart (myocardium) – called “intrinsic myogenic control”
Modified by ANS
Parasympathetic: ACh decreases rate and contraction force via the Vagus nerve X
Sympathetic: NE increases heart rate and force of contraction via nerve.

41. Cardioaccelatory center
Cardiac Centers in CNS
Cardioaccelatory center
Medulla oblongata (Activates sympathetic neurons)
Cardioinhibitory center
Medulla oblongata (Parasympathetic neurons)
Centers receive input from
Higher centers (cerebrum)
Receptors monitoring blood pressure
Receptors monitoring dissolved gases

42. Superior/Inferior Vena Cava
Rt. Atrium
Rt. Atrioventricular valve
Rt. Ventricle
Pulmonary Semilunar valve
Pulmonary Arteries
Lungs
Pulmonary Veins
Lt. Atrium
Lt. Atrioventricular valve
Lt. Ventricle
Aortic Semilunar valve
Ascending Aorta

44. Normal Functional Heart Anatomy

45. Congenital Heart Defects

46. Congenital Heart Defects