Chap. 19– The Heart (Cardiology)

19-1

Chap. 19 (Heart) Study Guide 1. Critically read Chapter 19 pp. 719-739 before

19.5 “Blood Flow” section2. Comprehend Terminology (those in bold)3. Study-- Figure questions, Think About It

questions, and Before You Go On (section-ending) questions

4. Do Testing Your Recall— 1, 2, 4-8, 11-195. Do True or False– 1-4, 7, 9-106. Do Testing Your Comprehension-- #1

2

What are you going to do with your heart?

♥ “The best and most beautiful things in the world cannot be seen or even touched—they must be felt with the heart.” --Hellen Keller

♥ “Happiness comes only when we push our brains and hearts to the farthest reaches of which we are capable.”--Leo C. Rosten

19-3

I. Overview of cardiovascular system

19-4

§ Introduction

• The circulatory system—

– Three component: the pump, the passageway, and the transport medium

– What are they respectively?

• The pump--

• The passageway--

• The transport medium--

19-5

§ Two circuits in the cardiovascular system (1)

1. Pulmonary circulation—

– Function?

– The route?

• R. ventricle Pulmonary arteries Lungs Pulmonary veins L. atrium

Figure 19.119-6

LungsPulmonarycapillaries

Pulmonarycirculation

Right side ofheart

= O2-rich blood= O2-poor blood

Pulmonaryveins

Pulmonaryarteries

19-7

2. Systemic circulation—

– Functions?

– The route? (Students work on it.)

• Starts which chamber of the heart? Major vessels? Destinations? Two major veins? Ends at which chamber of the heart?

Fig. 19.119-8

§ Two circuits in the cardiovascular system (2)

Left sideof heart

Systemiccirculation

Organsystems

= O2-rich blood= O2-poor blood

Systemicarteries

Systemiccapillaries

Systemicveins

19-9

II. Gross anatomy of the heart

19-10

19-11

§ Shape and size of the heart

• Base – broad superior portion

• Apex - inferior end (a blunt point)

• 3.5 in. wide at base, 5 in. from base to apex, and 2.5 in. anterior to posterior

• weighs 10 oz (300 gram; size of your fist)

Fig. 19.2

Base of heart

Apex of heart

AortaSuperior

vena cava

Diaphragm19-12

Next Topic

§ Heart Position (1)

19-13

§ Heart Position (2)

19-14

§ Heart Position (3)

19-15

16

§ Pericardial sac (pericardium) -1• Def. the double-walled, membranous

covering that encloses the heart

• Function– Friction free

• Peircardial fluid— Figure x

Cardiac Disorders here (Table 19.3):

• Pericarditis– inflammation here

• Pericardial effusion– fluid in pericardial cavity

• Cardiac tamponade– accumulation of fluid here

Figure x

Pericardial cavity

Heart

19-17

19-18

§ Pericardial sac (pericardium) - 2

1. Parietal pericardium– 2 SUBLAYERS– A-outer, tough/fibrous layer (CT) + B-deep thin

serous layer– turns inward . . . forms #2 below

2. Visceral pericardium (a.k.a. epicardium of heart wall)– INNER, thin, smooth, moist serous layer – covers heart surface

3. Pericardial cavity: between 1 + 2 above– filled with ____________________

Fig. 19.3

1

2

3

19-19

Functions?

19-20

§ Heart Wall (from outermost layer)1. Epicardium (a.k.a. visceral pericardium)

– serous membrane covers heart

2. Myocardium– thick muscular layer– fibrous skeleton - network of collagenous and

elastic fibers (special section for this one)

3. Endocardium - smooth inner lining– What type of epi.? Simple _________ epi.– Continuous with endothelium cells . . .

Fig. 19.3

2

1

3

19-21

§ Fibrous skeleton of the heart (1) – What is it? Four CT rings fuse with . . .

– Structure details– Four fibrous rings, surrounds the 4 valves; in sheets of tissue that interconnect these rings

– Location? In the walls between …

Figure 19.819-22

(Rear)Fibrous skeleton including fibrous rings

Left AV valve

Right AV valve

Aortic valve

Ventricularmyocardium

Pulmonary semilunarvalve

(Front) 19-23

§ Fibrous skeleton of the heart (2)

Functions–

– 1. Structure support-- firm base of the heart valves and openings of great vessels

– 2. It anchors the cardiac muscle

– 3. An electrical insulator:• Separate the atria from the ventricles

and direct A.P. to specific pathways

19-24

Checkpoint Questions

1. Does most of the heart lie to the right or left of the median plane?

2. Name, in order, the three layers of the heart wall beginning with the outermost layer.

19-25

19-26

§ Heart Chambers• 4 chambers—

– A. right and left ATRIA– auricles? Ear-like structures . . .

– B. right and left VENTRICLES

• 3 sulci (grooves)— on the surface• Largely fat and coronary blood vessels– A. Atrioventricular (coronary) sulcus-

– B+C. Anterior and posterior interventricular sulci

Figure 19.5 a+b

19-27Anterior viewCoronary sulcus?

19-28Posterior view

19-29

§ Heart Chambers – Internal (Fig. 19.7)

1. Interatrial septum– wall that separates atria

2. Pectinate muscles– internal ridges of myocardium

in right atrium and both auricles; (@ absorber)

3. Interventricular septum– wall that separates ventricles

4. Trabeculae carneae– internal ridges in both

ventricles (@ absorber)

Wave/sound absorber

19-30

Checkpoint Questions

1. Which heart chamber has the thickest walls? What is the significance of this structural difference?

2. Do the atrial pectinate muscles more nearly resemble the ventricular papillary muscles or the trabeculae carneae?

19-31

§ Heart valves (1)1. Two atrioventricular (AV) valves—

– A. Right AV valve– also called the tricuspid valve

– B. Left AV valve– also called . . .

• Function--blood from the atria to ventricles . . .Figure 19.8 (a,b)

19-32

Aorta

Superior vena cava

Pulmonary valve

Pulmonary veins

Right atrium

Right AV valve

Right ventricle

Inferior vena cava

Pulmonary artery

Pulmonary veins

Left atrium

Left AV valveAortic valve

Chordae tendineae

Papillary muscle

Left ventricle

Interventricular septum

19-33Superior views of these valves – next slide

Right AV valve

Left AV valveAortic/pulmonary valve

19-34

Heart valves (2)

2. Chordae tendineae—

– Structure–

• Fibrous cords anchor the cusps to the ventricle walls via papillary muscles

– Function–

• Prevent valves from being _________

Figure 19.7, 19.819-35

Right atrium

Right AV valve

Direction ofbackflow ofblood

Right ventricle

Papillary muscle

Chordae tendineae

Septum

19-36

Right AV valve seen from within the right ventricle

19-37

§ Heart valves (3)

3.Semilunar valves include: One ______ valve and one __________ valveA. Where are they located respectively? • Major arteries leave the ventricles

B. How to prevent them from everting?• Anatomical structure— leakproof “seam”

C. Function– (of all valves)• Ensure unidirectional flow of blood

Figure 19.7 and Fig. Z

19-38

Aorta

Superior vena cava

Pulmonary valve

Pulmonary veins

Right atrium

Right AV valve

Right ventricle

Inferior vena cava

Pulmonary artery

Pulmonary veins

Left atrium

Left AV valve

Aortic valveChordae tendineae

Papillary muscle

Left ventricle

Interventricular septum

19-39

Next slide

Direction of backflow of blood

Leakproof“seam”

Aortic valve

19-40

(Right or Left Ventricle)

(Pulmonary trunk or Aorta)

19-41

§ Valve Mechanics (Fig. 19.9, 19.19)

Ventricles filling & isovolumetric contraction– AV valves open (semilunar valves close);

blood flows from atria to ventricles (v. fillings)

– AV valves open/closed (circle one)—S1– ventricle pressure continues to rise– Momentarily before ventricle ejection

Ventricles ejection & isovolumetric relaxation

– semilunar valves open (AV valves close); – ventricle ejection; ventricle pressure drops– semilunar valves open/closed (circle one)—S2– Isovolumetric relaxation

Operation of Atrioventricular Valves

19-42

S1

19-43

Operation of Semilunar Valves

S2

Before You Go On (p. 730)

• Reminder: Remember to go over each question of Before You Go On in the text.

• P. 730– Trace the flow of blood through the heart, naming each chamber, valve, and the great vessels in order (from the superior vena cava to the aorta). Do it yourself. Fig. 19.9 is a great figure to help you with this.

\ 44

Figure 19.10Fig. 19.9 Pathway of blood flow through the heart

III. The Coronary Circulation

19-46

§ Coronary arteries

Left C.A.Right C.A.19-47

19-48

§ Coronary Arterial Supply• 1. Left coronary artery (LCA)– 2 branches

– 1A--anterior interventricular branch• supplies blood to interventricular septum and

anterior walls of both ventricles

– 1B--circumflex branch (Fig. 19.10 a+b)• passes around left side of heart in coronary sulcus,

supplies left atrium and posterior wall of left ventricle; it gives off a left marginal branch (1C)

• 2. Right coronary artery (RCA)– 2 branches– 2A--right marginal branch

• supplies lateral side of R atrium and ventricle

– 2B--posterior interventricular branch• supplies posterior walls of ventricles

19-49

1A

1B

2A

19-50

1C 2A

2B

1B

19-51

§ Anastomoses of coronary arteries1. Definition (Anastomosis) – a point where

two blood vessels join/merge; this is arterial anastomoses

2. Where? Anterior interventricular branch of LCA joins the posterior interventricular branch of RCA

3. Function– provide collateral (alternative) routes of blood supply to a tissue (the heart)

Fig. x

19-53

Chest pain and Heart Attack

• Angina pectoris--– partial obstruction of coronary blood flow can

cause chest pain – pain caused by ischemia, often activity

dependent

• Myocardial infarction (heart attack)-- – complete obstruction causes death of cardiac

cells in affected area– pain or pressure in chest that often radiates

down left arm

19-54

§ Venous Drainage of Heart• 10% drains directly into right atrium and

ventricle via multiple thebesian veins

• 90% returns to right atrium via: (Fig. 19.10)– A. great cardiac vein

• blood from anterior interventricular sulcus

– B. middle cardiac vein (post. interventricular v.) • from posterior sulcus

– C. left marginal vein

The above three (A, B, C) empty into the coronary sinus before emptying into the ____________ (which chamber of the heart?)

19-55

A

19-56

B

C

A

or posterior interventricular v.

IV. Cardiac conduction system

19-57

19-58

§ 19.3 Cardiac muscle & conduction system

Heart has its own pacemaker, nerves MODIFY the heart rate & contraction strength.

• Beat rhythmically, _________beats per min.– Pacemaker? Where? (next slide)– Myogenic and autorhythmic

– Regulation by autonomic nerve system

19-59

§ Cardiac Conduction System (1)

I. Properties– myogenic - heartbeat originates from within

____________________– Originated from what cells (1% of heart cells)?

cardiac muscles become specialized into autorhythmic cells (cardiac conduction system)

– What do autorhythmic cells do?–regular, spontaneous depolarization

II. Components– next slide

19-60

Cardiac Conduction System (2)– Autorhythmic cells

1. SA (sinoatrial) node: pacemaker, initiates heartbeat, sets heart rate; where?

2. AV node: electrical gateway to ventricles; where?

• fibrous skeleton– insulates atria from ventricle

3. AV bundle: pathway for signals from AV node

4. Right and left bundle branches: divisions of AV bundle that enter interventricular septum

5. Purkinje fibers: upward from apex spread throughout ventricular myocardium

Fig. 19.12 + X

19-61

Cardiac Conduction System

1

2

34

5

1. Sinoatrial(SA) node

Rightatrium

2. Internodalpathway

5a. Rightbranchof bundleof His Right

ventricle

6. Purkinjefibers

Leftventricle

5b. Left branchof bundle of His

4. Bundle of His or AV bundle

3. Atrioventricular(AV) node

Interatrialpathway

19-62

Students-- work on this one at home

Checkpoint Question

Which chamber of the heart is first to receive the electrical signal that induces the heart to contract?

63

V. Cardiac muscle

19-64

§ Cardiac vs. skeletal m.(1)Skeletal M. Cardiac M.

(cardiocyte)Fibers & their control

•Fibers independent•Voluntary

•Interlocking cells; (next)•Involuntary

Nervous control by

•Somatic motor neurons

• Autonomic nervous sys.

Initiation of contraction

•Requires input from motor neurons

• by autorhythmic cells in heart

65

§ Cardiac vs. skeletal m.(2)

66

1. Cardiac myocytes—size, thickness etc.

2. T (transverse) tubules– smaller

3. Presence of intercalated discs– (see next slide)

4. Mitochondria—5. Myoglobin and glycogen--

§ Intercalated discs (of cardiac muscle cells)

• Def. specialized zigzag structures joining cardiac muscle cells end to end

• Containing three distinctive features not found in skeletal muscle; what are they?

Figure 19.11 a-c

67

Figure 19.11a light micrograph

19-68

Next slide

19-69

One myocyte is shown (colored).

1-- interdigitating folds

2—mechanical junctions– two types; fascia adherens and desmosomes

3—electrical (gap) junctions--19-70

Structure of an

intercalated disc

13

2

Plasma membranes of adjacentcardiac muscle fibers

Desmosome

Gap junction

Intercalated disc

Actionpotential 19-71

Fascia adherens

§ Intercalated discs

1. Function of interdigitating folds--

2. Functions of fascia adherens and desmosome –

• Types of adhering junction

• Mechanically, hold cells together

72

§ Intercalated discs

3. Functions of gap junction (connexons):

• Allows action potentials to spread . . .

• Therefore, cardiac cells form functional syncytia— cardiac cells excited and contract as a single unit

Q--Does the atria and the ventricle each form a separate unit?

73

VI. Electrical activity of heart (autorhythmic cells)

19-74

§ 19.4 Heart Autorhythmic Cells1. Two types of cardiac muscle cells:A. 1% are autorhythmic cells (our focus

on this section)– – Function?

• AP— Yes• Contraction– No

B. 99% --contractile cells– Function?

• AP— No initiation of own Action Potential

• Contraction– Yes 19-75

§ Heart autorhythmic cells2.Autorhythmic cells act as pacemaker:

• How? Their m. potential slowly depolarizes (drifts) between AP, until . . . …

Figure 19.13

19-76

Pacemaker potentials & action potentials of the

SA node

19-77

A

BC

§ Heart autorhythmic cells3. Details of pacemaker activity: (vs.

AP in nerve and skeletal m.):

A. Slow depolarization:i. K+ voltage-gated channels slowly closeii. (No voltage-gated Na+ channels),

instead sodium leak channels are used; So, sodium ions move in/out

iii. Transient Ca+2 channels open—Calcium ions move inward

All these make the inside becomes depolarized Thus, pacemaker p. toward threshold 19-78

§ Heart autorhythmic cellsB. Rising phase of the action potential:

• Once, reach threshold p., long-lasting Ca+2 channels open; . . .

• Influx of calcium ions

C. The falling phase:

• as usual, potassium ions efflux

19-79

§ Heart autorhythmic cells4.Autorhythmic cells are self excitable:

– Without nervous stimulation– They initiate AP cyclically, which

trigger rhythmic beating– Each depolarization of SA node sets

off one heartbeat (every 0.8 sec.)

– They form the conduction system of the heart (see Figure 19.12)

– It excites the other components in the system

19-80

§ Heart autorhythmic cells5. The spread of cardiac excitation:

In a coordinated sequence:A-First, atrial excitation– From SA node to

atria; How? through gap junctions; via internodal and interatrial pathways as well; Result– a single smooth contraction of the pair of atria (Fig. Y)

B-Second, from the atria to the ventricles—AV node is the only point of electrical contact

from the atria to the ventriclesC-Finally, ventricular excitation--

from AV node to the bundle of His, . . .Result– a single smooth contraction in ventricles 19-81

Interatrial pathwayRight atrium Left atrium

SA node

Internodalpathway

AV node

Purkinjefibers

Right ventricle Left ventricle

Bundleof His

1st

beat

2nd beat

19-82

VII. contractile activity of heart

19-83

19-84

Our focus

§ Cardiac contractile cells

1. Action potential is initiated by: the pacemaker cells

3 phases: – Rising– Plateau– …

85

§ Cardiac contractile cells2.The detail of action potential: A.Rising phase • Massive sodium ions influx causes

depolarization and AP

B.Plateau phase• Primarily caused by opening of calcium

channels• Also caused by temp. reduction in outflow of

_____________ ions

86

§ Cardiac contractile cellsC.Falling phase

• Primarily caused by ____________ outflow• Closing of calcium channels contribute to

this as well

87

19-88

Review slide— ID A, B, C, D, E below

B

D

C

E

A

§ Cardiac contractile cells

3.Contractile response

Compare to skeletal muscle:

• Longer period of cardiac contraction

• Longer refractory period

How? Why? (next)

89

Action potential

Refractory period

Contractile response

§ Cardiac contractile cellsA.Longer period of cardiac contraction

– 3x longer compared to skeletal m.– Caused by entry of calcium ions which

induce more calcium ions release from the sarcoplasmic reticulum

– Purpose– this increased contractile time ensures emptying blood into ventricles and arteries

Fig. 11.13 (skeletal muscle)

90

Latentperiod

Contractiontime

Relaxationtime

Muscletwitch

Contractileresponse

Actionpotential

Stimulation

In skeletal muscle

19-91

§ Cardiac contractile cellsB.Longer refractory period

• Caused chiefly by inactivation of the sodium ion channels

• Consequences/Purpose– Cardiac muscle cannot be re-stimulated until contraction is almost over, therefore summation and tetanus of cardiac m. is impossible

• This ensures . . .

Compared to Fig. 11.13 (Shown previously; in skeletal m.)

92

§ ECG (Electrocardiogram)1. Def. A record of the overall electrical activity

in all the cardiac muscle cells from the body surface

– NOT a recording of a single action potential in a single cell

– ECG recording represents . . .electrical activity detected by electrodes at 2 different points

Figure 19.15 (ECG) 93

§ ECG (Electrocardiogram)

2.Components of the ECG correlate to cardiac events (Fig. 19.16 in the next slide)

• P wave— atrial depolarization when the electrical impulse spreads across the atria

• QRS complex— • T wave— ventricular repolarization

95

P

Q

R

S

TP

19-96

P

QRS

T