1. The Heart
OBJECTIVES:

2. OBJECTIVES Orientation of heart in thorax
Explain the circuits of blood flow
Gross Anatomy of Heart
Blood Flow to the Heart Muscle
Histology of Heart Muscle Tissue
Electrical Conduction System of Heart
Disorders of the Heart

3. Location and Orientation within the Thorax
Heart – typically weighs 250–350 grams (healthy heart)
Largest organ of the mediastinum (area between the lungs, thoracic inlet superiorly and diaphragm inferiorly, sternum anteriorly and vertebral column posteriorly)
Located between the lungs
Apex (pointed part) lies to the left of the midline
Base is the broad posterior surface (facing toward left shoulder)
The heart is a double pump: one pumps blood to the lung and the other to the body

4. Location and Orientation within the Thorax
The heart is in contact with the diaphragm inferiorly, lungs laterally, sternum anteriorly and the spinal column and great vessels posteriorly. Superiorly, the vessels which enter and exit the heart fill much of the superior mediastinum.
Figure 18.2

5. Four “Corners” of the Heart
Superior right
At costal cartilage of third rib and sternum
Inferior right
At costal cartilage of sixth rib lateral to the sternum
Superior left
At costal cartilage of second rib lateral to the sternum
Inferior left
Lies in the fifth intercostal space at the midclavicular line

6. The Pulmonary and Systemic Circuits
There are three separate circuits of blood involving the heart: the pulmonary, the systemic and the coronary.
The pulmonary circuit goes from the right ventricle to the pulmonary arteries to the lungs and back to the left atrium
The sysemic circuit runs from the left ventricle to the aorta and onto the superior and inferior systemic arteries.
The coronary circuit involves the arteries and veins which supply the heart muscle itself. It runs from the right and left coronary arteries arising from the aorta.
Figure 18.1

7. Blood Supply to the Heart
Functional blood supply
Coronary arteries
Arise from the aorta
Located in the coronary sulcus
Main branches
Left and right coronary arteries

8. Coronary Circulation
The left coronary artery (LCA) arises from the left side of the aorta, passes posterior to the pulmonary trunk then divides into two branches: the anterior interventricular and the circumflex arteries. The anterior interventricular artery is referred to as the Left Anterior Descending Artery, or LAD and runs inferiorly down thhe interventricular septum and anterior walls of both ventricles.
The circumflex artery (Cx), follows the coronary sulcus posteriorly and supplies the left atrium and the posterior part of the left ventricle
The Right Coronary Artery (RCA) emerges from the right side of the aorta and descends in the coronary sulcus on the anterior surface of the heart between the right atrium and right ventricle. At the inferior border of the heart, it branches to form the marginal artery. Continuing into the posterior part of the coronary sulcus the right coronary artery gives off a large branch in the posterior interventricular sulcus, the posterior interventricular artery. Clinically this arteries commonly called the posterior descending artery (PDA). The right coronary artery and its branches supply the right atrium and much of the right ventricle
Cardiac veins
Cardiac veins collect blood from the arteries and returns it to the right atrium. The largest vein is the coronary sinus. It occupies the posterior part of the coronary sulcus and returns almost all the venous blood from the heart to the right atrium. Into the coronary sinus drain three large tributaries: the great cardiac vein the middle cardiac vein in the small cardiac vein

9. Blood Supply to the Heart
Know all of these!
Figure 18.16

10. Structure of the Heart – Coverings
Figure 18.3

11. Structure of the Heart – Coverings
Pericardium – two primary layers
Fibrous pericardium
Strong layer of dense connective tissue
Serous pericardium
Formed from two layers
Parietal pericardium – this is the more superficial layer
Visceral pericardium – this layer is in direct contact with the surface of the heart. The function of these layers is to reduce friction while the heart is beating
So in total there are three layers of tissue surrounding the heart. The fibers per cardio and is separated from the serous pericardium and protects the heart.

12. Structure of the Heart – Layers of the Heart Wall
This muscle arrangement is very efficient to squeeze out all of the blood
Figure 18.4

13. Structure of Heart Wall
Left ventricle – three times thicker than right
Exerts more pumping force
Flattens right ventricle into a crescent shape
Figure 18.7

14. Heart Chambers
Must know all of this!
Figure 18.5b

15. Heart Chambers
Must know all of this!
Figure 18.5e

16. Posterior View of the Heart
Must know all of this!
Figure 18.5d

17. The Heart A muscular double pump (left and right)
Pulmonary circuit (right side) – takes blood to and from the lungs
Systemic circuit (left side) – vessels transport blood to and from body tissues
Atria – receive blood from the pulmonary and systemic circuits
Ventricles – the pumping chambers of the heart

18. Heart Chambers Right and left atria Right and left ventricles
Superior chambers
Right and left ventricles
Inferior chambers
Internal divisions
Interventricular septa
Interatrial septa
External markings
Coronary sulcus
posterior interventricular sulcus

19. Right Atrium Forms right border of heart
Receives blood from systemic circuit
Auricle - the auricle is a separate part of the main atrium known as the atrial appendages
Pectinate muscles
Ridges inside anterior of right atrium - associated with auricle
Fossa ovalis
Depression in interatrial septum
Remnant of foramen ovale

20. Right Ventricle
Receives blood from right atrium through the tricuspid valve
Pumps blood into pulmonary circuit via
Pulmonary trunk
Internal walls of right ventricle
Trabeculae carneae
Papillary muscles
Chordae tendineae

21. Left Atrium Makes up heart’s posterior surface
Receives oxygen-rich blood from lungs
Opens into the left ventricle through
Mitral valve (left atrioventricular valve)

22. Left Ventricle Forms apex of the heart
Internal walls of left ventricle
Trabeculae carneae
Papillary muscles
Chordae tendineae
Pumps blood through systemic circuit via
Aortic semilunar valve (aortic valve)

23. Blood Flow Through the Heart
Figure 18.6

24. Heartbeat 70 – 80 beats per minute at rest
Systole – contraction of a heart chamber
Diastole – expansion of a heart chamber
Systole and diastole also refer to
Stage of heartbeat when ventricles contract and expand

25. Heart Valves – Valve Structure
Each valve composed of
Endocardium with connective tissue core
Atrioventricular (AV) valves
Between atria and ventricles
Aortic and pulmonary valves
At junction of ventricles and great arteries

26. Fibrous Skeleton Surrounds all four valves Functions
Composed of dense connective tissue
Functions
Anchors valve cusps
Prevents overdilation of valve openings
Main point of insertion for cardiac muscle
Blocks direct spread of electrical impulses

27. Heart Valves – Valve Structure
Figure 18.8a

28. Function of the Atrioventricular Valves
Figure 18.9a

29. Function of the Atrioventricular Valves
Figure 18.9b

30. Function of the Semilunar Valves
Figure 18.10a, b

31. Microscopic Anatomy of Cardiac Muscle
Figure 18.12a, b

32. Cardiac Muscle Tissue
Figure 18.12c, d

33. Cardiac Muscle Tissue Not all cardiac cells are innervated
Will contract in rhythmic manner without innervation
Inherent rhythmicity
Is the basis for rhythmic heartbeat

34. Conducting System
Cardiac muscle tissue has intrinsic ability to generate and conduct impulses
Conducting system
A series of specialized cardiac muscle cells
Sinoatrial (SA) node sets the inherent rate of contraction (overrides autorhythmicity)

35. Conducting System
Figure 18.14

36. Innervation Heart rate is altered by external controls
Nerves to the heart include
Visceral sensory fibers
Parasympathetic branches of the vagus nerve
Sympathetic fibers – from cervical and upper thoracic chain ganglia
Figure 18.15

37. Heart Sounds “Lub-dub” – sound of valves closing First sound “lub”
The AV valves closing
Second sound “dub”
The semilunar valves closing

38. Heart Sounds
Each valve sound – best heard near a different heart corner
Pulmonary valve – superior left corner
Aortic valve – superior right corner
Mitral (bicuspid) valve– at the apex
Tricuspid valve – inferior right corner

39. Heart Sounds
Figure 18.11

40. Disorders of the Heart
Coronary artery disease – caused by a buildup of fatty plaque called atherosclerosis in the coronary arteries resulting in decreased blood supply to the myocardium of the heart and diminished heart function. The causes of CAD may be lifestyle or genetic. The first step is to make lifestyle changes. If this is insufficient to open the arteries then surgical intervention may be necessary.
Atherosclerosis – fatty deposits
Angina pectoris – chest pain
Myocardial infarction – blocked coronary artery
Heart attack
Silent ischemia – no pain or warning. Loss of blood supply to a portion of the cardiac muscle.

41. Disorders of the Heart Heart failure Congestive heart failure (CHF)
Progressive weakening of the heart
Cannot meet the body’s demands for oxygenated blood
Congestive heart failure (CHF)
Heart enlarges
Pumping efficiency declines
Cor pulmonale
Enlargement and potential failure of right ventricle