1. 19 PART 1
The Heart
Pages

2. The Heart A muscular double pump
Pulmonary circuit—takes blood to and from the lungs
Systemic circuit—vessels transport blood to and from body tissues
Atria—receive blood from the pulmonary and systemic circuits
Ventricles—the pumping chambers of the heart

3. Figure 19.1 The heart as a double pump.
Pulmonary Circuit
Capillary beds of lungs where gas exchange occurs
Aorta and branches
Pulmonary arteries
Left atrium
Pulmonary veins
Right atrium
Heart
Right ventricle
Left ventricle
Systemic Circuit
Venae cavae
Capillary beds of all body tissues where gas exchange occurs
Oxygen-rich, CO2-poor blood
Oxygen-poor, CO2-rich blood

4. Location and Orientation within the Thorax
Heart—typically weighs 250–350 grams (healthy heart)
Largest organ of the mediastinum
Located between the lungs
Apex lies to the left of the midline
Base is the broad posterior surface

5. Location of the Heart in the Thorax
Superior vena cava
Left lung
Aorta
Parietal pleura (cut)
Pericardium (cut)
Pulmonary trunk
Diaphragm
Apex of heart
Diaphragm
(a)
Rib 2
Midsternal line
Pericardium
(cut)
Fat in
epicardium
Rib 5
Left lung
Aorta
Mediastinum
Apex of
heart
(d)
Right
auricle
of right
atrium
Superior
vena cava
ventricle
Heart
Posterior
Right lung
(b)
Mediastinum
Figure 19.2

6. Structure of the Heart—Coverings
Pericardium—two primary layers
Fibrous pericardium
Strong layer of dense connective tissue
Serous pericardium
Formed from two layers
Parietal layer of the serous pericardium
Visceral layer of the serous pericardium

7. Layers of the Pericardium and of the Heart Wall
Fibrous pericardium
Parietal layer of serous
pericardium
Pericardial cavity
Epicardium (visceral
layer of serous
pericardium)
Myocardium
Endocardium
Pulmonary
trunk
Heart chamber
Heart
wall
Pericardium
Figure 19.3

8. Structure of the Heart—Layers of the Heart Wall
Epicardium
Visceral layer of the serous pericardium
Myocardium
Consists of cardiac muscle
Muscle arranged in circular and spiral patterns
Endocardium
Endothelium resting on a layer of connective tissue
Lines the internal walls of the heart

9. Right and left ventricles Internal divisions
Heart Chambers
Right and left atria
Superior chambers
Right and left ventricles
Inferior chambers
Internal divisions
Interventricular septum
Interatrial septum

10. Heart Chambers Aorta Left pulmonary artery Superior vena cava
Left atrium
Left pulmonary veins
Mitral (bicuspid) valve
Aortic valve
Pulmonary valve
Left ventricle
Papillary muscle
Interventricular septum
Epicardium
Myocardium
Endocardium
(e) Frontal section
Superior vena cava
Right pulmonary artery
Pulmonary trunk
Right atrium
Right pulmonary
veins
Fossa ovalis
Pectinate muscles
Tricuspid valve
Right ventricle
Chordae tendineae
Trabeculae carneae
Inferior vena cava
Figure 19.5e

12. Forms right border of heart Receives blood from systemic circuit
Right Atrium
Forms right border of heart
Receives blood from systemic circuit
Superior vena cava
Inferior vena cava
Coronary sinus
Right auricle projects anteriorly from superior corner of atrium
Opens into right ventricle via tricuspid valve (right atrioventricular valve)

13. Gross Anatomy of the Heart
Left common carotid
artery
Left subclavian artery
Aortic arch
Ligamentum arteriosum
Left pulmonary artery
Left pulmonary veins
Auricle of
left atrium
Circumflex artery
Left coronary artery
(in coronary sulcus)
Left ventricle
Great cardiac vein
Anterior interventricular
artery (in anterior
interventricular sulcus)
Apex
(b) Anterior view
Brachiocephalic trunk
Superior vena cava
Right pulmonary artery
Ascending aorta
Pulmonary trunk
Right pulmonary
veins
Right atrium
Right coronary artery
Anterior cardiac vein
Right ventricle
Right marginal artery
Small cardiac vein
Inferior vena cava
Figure 19.5b

14. Inferior View of the Heart
(d) Inferior view; surface shown rests on the diaphragm.
Aorta
Left pulmonary artery
Left pulmonary veins
Auricle of left atrium
Left atrium
Great cardiac vein
Posterior vein of
left ventricle
Left ventricle
Apex
Superior vena cava
Right pulmonary artery
Right pulmonary veins
Right atrium
Inferior vena cava
Right coronary artery
(in coronary sulcus)
Coronary sinus
Posterior interventricular
artery (in posterior
interventricular sulcus)
Middle cardiac vein
Right ventricle
Figure 19.5d

16. Heart Chambers Aorta Left pulmonary artery Superior vena cava
Left atrium
Left pulmonary veins
Mitral (bicuspid) valve
Aortic valve
Pulmonary valve
Left ventricle
Papillary muscle
Interventricular septum
Epicardium
Myocardium
Endocardium
(e) Frontal section
Superior vena cava
Right pulmonary artery
Pulmonary trunk
Right atrium
Right pulmonary
veins
Fossa ovalis
Pectinate muscles
Tricuspid valve
Right ventricle
Chordae tendineae
Trabeculae carneae
Inferior vena cava
Figure 19.5e

17. Receives blood from right atrium through the tricuspid valve
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
Pulmonary semilunar valve
Located at opening of right ventricle and pulmonary trunk

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

19. Inferior View of the Heart
(d) Inferior view; surface shown rests on the diaphragm.
Aorta
Left pulmonary artery
Left pulmonary veins
Auricle of left atrium
Left atrium
Great cardiac vein
Posterior vein of
left ventricle
Left ventricle
Apex
Superior vena cava
Right pulmonary artery
Right pulmonary veins
Right atrium
Inferior vena cava
Right coronary artery
(in coronary sulcus)
Coronary sinus
Posterior interventricular
artery (in posterior
interventricular sulcus)
Middle cardiac vein
Right ventricle
Figure 19.5d

20. Gross Anatomy of the Heart
Left common carotid
artery
Left subclavian artery
Aortic arch
Ligamentum arteriosum
Left pulmonary artery
Left pulmonary veins
Auricle of
left atrium
Circumflex artery
Left coronary artery
(in coronary sulcus)
Left ventricle
Great cardiac vein
Anterior interventricular
artery (in anterior
interventricular sulcus)
Apex
(b) Anterior view
Brachiocephalic trunk
Superior vena cava
Right pulmonary artery
Ascending aorta
Pulmonary trunk
Right pulmonary
veins
Right atrium
Right coronary artery
Anterior cardiac vein
Right ventricle
Right marginal artery
Small cardiac vein
Inferior vena cava
Figure 19.5b

21. Heart Chambers Aorta Left pulmonary artery Superior vena cava
Left atrium
Left pulmonary veins
Mitral (bicuspid) valve
Aortic valve
Pulmonary valve
Left ventricle
Papillary muscle
Interventricular septum
Epicardium
Myocardium
Endocardium
(e) Frontal section
Superior vena cava
Right pulmonary artery
Pulmonary trunk
Right atrium
Right pulmonary
veins
Fossa ovalis
Pectinate muscles
Tricuspid valve
Right ventricle
Chordae tendineae
Trabeculae carneae
Inferior vena cava
Figure 19.5e

22. Internal walls of 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. Inferior View of the Heart
(d) Inferior view; surface shown rests on the diaphragm.
Aorta
Left pulmonary artery
Left pulmonary veins
Auricle of left atrium
Left atrium
Great cardiac vein
Posterior vein of
left ventricle
Left ventricle
Apex
Superior vena cava
Right pulmonary artery
Right pulmonary veins
Right atrium
Inferior vena cava
Right coronary artery
(in coronary sulcus)
Coronary sinus
Posterior interventricular
artery (in posterior
interventricular sulcus)
Middle cardiac vein
Right ventricle
Figure 19.5d

24. Heart Chambers Aorta Left pulmonary artery Superior vena cava
Left atrium
Left pulmonary veins
Mitral (bicuspid) valve
Aortic valve
Pulmonary valve
Left ventricle
Papillary muscle
Interventricular septum
Epicardium
Myocardium
Endocardium
(e) Frontal section
Superior vena cava
Right pulmonary artery
Pulmonary trunk
Right atrium
Right pulmonary
veins
Fossa ovalis
Pectinate muscles
Tricuspid valve
Right ventricle
Chordae tendineae
Trabeculae carneae
Inferior vena cava
Figure 19.5e

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. Heart Valves—Valve Structure
Pulmonary valve
Aortic valve
Area of cutaway
Mitral valve
Tricuspid valve
Myocardium
Tricuspid
(right atrioventricular)
valve
(a)
Mitral
(left atrioventricular)
Aortic
Pulmonary
Fibrous
skeleton
Anterior
Figure 19.6a

27. Surrounds all four valves
Fibrous Skeleton
Surrounds all four valves
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

28. Function of the Atrioventricular Valves
Blood returning to
the heart fills atria,
putting pressure
against atrioventricular
valves; atrioventricular
valves are forced
open.
As ventricles fill,
atrioventricular
valve flaps hang
limply into
ventricles.
Atria contract,
forcing additional
blood into ventricles.
(a) AV valves open; atrial pressure greater than ventricular pressure
Direction of
blood flow
Atrium
Ventricle
Cusp of
valve (open)
Chordae
tendineae
Papillary
muscle 1 2 3
Figure 19.7a

29. Function of the Atrioventricular Valves
Ventricles contract,
forcing blood against
atrioventricular valve
cusps.
Atrioventricular
valves close.
Papillary muscles
contract and
chordae tendineae
tighten, preventing
valve flaps from
everting into atria.
(b) AV valves closed; atrial pressure less than ventricular pressure
Atrium
Blood in
ventricle
Cusps of
atrioventricular
valve (closed) 1 2 3
Figure 19.7b

30. Function of the Semilunar Valves
As ventricles contract
and intraventricular
pressure rises, blood
is pushed up against
semilunar valves,
forcing them open.
As ventricles relax
pressure falls, blood
flows back from
arteries, filling the
cusps of semilunar
valves and forcing
them to close.
(a) Semilunar valves open
(b) Semilunar valves closed
Aorta
Pulmonary
trunk
Figure 19.8

31. “Lub-dup”—sound of valves closing
Heart Sounds
“Lub-dup”—sound of valves closing
First sound “lub”
The AV valves closing
Second sound “dup”
The semilunar valves closing

32. Heart Sounds Pulmonary valve Aortic valve Area of cutaway Mitral valve
Tricuspid valve
Myocardium
Tricuspid
(right atrioventricular)
valve
(a)
Mitral
(left atrioventricular)
Aortic
Pulmonary
Fibrous
skeleton
Anterior
Figure 19.6a

33. Pathway of Blood Through the Heart
Beginning with oxygen-poor blood in the superior and inferior venae cavae
Go through pulmonary and systemic circuits
A blood drop passes through all structures sequentially
Atria contract together
Ventricles contract together

34. Blood Flow Through the Heart
Right
atrium
Aorta
To body
To heart
To lungs
Mitral
valve
Left
ventricle
Four
pulmonary
veins
Superior vena cava (SVC)
Inferior vena cava (IVC)
Coronary sinus
Pulmonary
trunk
arteries
Aortic
semilunar
Tricuspid
semilunar valve
IVC
SVC
Two pulmonary arteries
carry the blood to the
lungs (pulmonary circuit)
to be oxygenated.
Oxygen-rich blood returns
to the heart via the four
pulmonary veins.
Oxygen-poor blood
returns from the body
tissues back to the heart.
Oxygen-rich blood is
delivered to the body
tissues (systemic circuit).
Oxygen-rich blood
Coronary
sinus
Figure 19.10

35. 70–80 beats per minute at rest
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

36. Structure of Heart Wall
Right
ventricle
Left
Interventricular
septum
Walls differ in thickness
Atria—thin walls
Ventricles—thick walls
Systemic circuit
Longer than pulmonary circuit
Offers greater resistance to blood flow
Left ventricle— three times thicker than right
Exerts more pumping force

37. Forms a thick layer called myocardium
Cardiac Muscle Tissue
Forms a thick layer called myocardium
Striated like skeletal muscle
Contractions pump blood through the heart and into blood vessels
Contracts by sliding filament mechanism
Cardiac muscle cells
Short
Branching
Have one or two nuclei

38. Microscopic Anatomy of Cardiac Muscle
Nucleus
Intercalated discs
Cardiac muscle cell
(a)
Fasciae adherens
Gap junctions
Nucleus
I band
A band
Cardiac
muscle cell
Sarcolemma
Z disc
Mitochondrion
T tubule
Sarcoplasmic
reticulum
Intercalated
disc
(b)
Figure 19.12

39. Cells join at intercalated discs
Cardiac Muscle Tissue
Cells join at intercalated discs
Complex junctions
Form cellular networks
Cells are separated by delicate endomysium
Binds adjacent cardiac fibers
Contains blood vessels and nerves

40. Intercalated discs—complex junctions
Cardiac Muscle Tissue
Intercalated discs—complex junctions
Adjacent sarcolemmas interlock
Possess two distinct regions
Fasciae adherens-bind adjacent cells together & transmit contractile force to them
Gap junctions-allow ions to pass between cells & transmission of signals to adjacent cells

41. Triggered to contract by Ca2+ entering the sarcoplasm
Cardiac Muscle Tissue
Triggered to contract by Ca2+ entering the sarcoplasm
Signals sarcoplasmic reticulum to release Ca2+ ions
Ions diffuse into sarcomeres
Trigger sliding filament mechanism

42. Cardiac muscle tissue has intrinsic ability to
Conducting System
Cardiac muscle tissue has intrinsic ability to
Generate and conduct impulses
Signal these cells to contract rhythmically
Conducting system
A series of specialized cardiac muscle cells
Sinoatrial (SA) node sets the inherent rate of contraction

43. Conducting System The sinoatrial (SA) node (pacemaker)
generates impulses.
Internodal pathway
Superior vena cava
Right atrium
Left atrium
Purkinje
fibers
Inter-
ventricular
septum
The impulses
pause (0.1 sec) at the
atrioventricular
(AV) node.
The atrioventricular
(AV) bundle connects
the atria to the ventricles.
The bundle branches
conduct the impulses
through the interventricular
septum.
The Purkinje fibers
stimulate the contractile
cells of both ventricles. 1 2 3 4 5
Figure 19.14

44. Innervation Heart rate is altered by external controls
Thoracic spinal cord
The vagus nerve
(parasympathetic)
decreases heart rate.
Cardioinhibitory
center
Cardio-
acceleratory
Sympathetic cardiac
nerves increase heart rate
and force of contraction.
Medulla oblongata
Sympathetic
trunk
ganglion
Dorsal motor nucleus
of vagus
Sympathetic trunk
AV node
SA node
Parasympathetic fibers
Sympathetic fibers
Interneurons
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 19.15

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

46. Blood Supply to the Heart
Right
ventricle
coronary
artery
atrium
marginal
Posterior
interventricular
Anterior
Circumflex
Left
Aorta
Anastomosis
(junction of
vessels)
Superior
vena cava
(a) The major coronary arteries
Left atrium
Pulmonary
trunk
cardiac
veins
Small
cardiac vein
Middle cardiac vein
Great
vein
Coronary
sinus
(b) The major cardiac veins
Figure 19.16