ch21 heart

HUMAN ANATOMYFifth Edition

Chapter 1 Lecture

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Chapter 21 Lecture

Frederic MartiniMichael Timmons

Robert Tallitsch

Chapter 21The Cardiovascular System: The Heart

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.

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

Fig

21.6

[Insert fig 21.1]

Figure 21.1 The Pulmonary and Systemic Circuits

An Overview of the Cardiovascular System

Figure 21.4 Position of the Heart

Orientation of the Heart

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

The Pericardium

The Pericardium

Figure 21.2c The Location of the Heart in the Thoracic Cavity

The Pericardium

Figure 21.2d The Location of the Heart in the Thoracic Cavity

The heart wall

• Parietal pericardium

• Epicardium/visceral pericardium

• Myocardium-cardiac muscle tissue

• Endocardium-– epithelia tissue

Fig

21.3

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

Figure 21.3c-e Cardiac Muscle Tissue

Structure of the Heart Wall

Fig

21.5

Fig

21.5

Fig

21.6

Figure 21.6d Horizontal Section of Heart

Internal Anatomy and Organization of the Heart

Heart valves

• 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

Figure 21.7a Valves with Ventricles Relaxed

The Structure and Function of Heart Valves

• Semilunar valves-between the ventricle & an artery

• lt. ventricle>Aortic semilunar valve>aorta

• rt. ventricle>Pulmonary semilunar valve>pulmonary artery

Figure 21.7b Valves with Ventricles Contracted

The Structure and Function of Heart Valves

Figure 21.9a Anterior Heart Figure 21.9b Posterior Heart

Coronary Circulation

Pulmonary circuit - from heart

to lungs

back to heart

Systemic circuit- from heart

to body

back to heart

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

Right vs. Left ventricle

The left Ventricle has a much thicker myocardium

Fig 21.6

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)

Heart Valves and Heart Sounds

• Placement of a stethoscope varies depending on which heart sounds and valves are of interest.

• Closure of the AV valves create the 1st heart sound (‘lub’).

• Closure of the semilunar valves create the 2nd heart sound (‘dub’).

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

Cardiac Cycle

• Systole: contraction phase

• Diastole: relaxation phase

Mid-to-late diastole.

Early diastole Ventricular

systole

lub

dub

Nodal cells

• Nodal cells spontaneously depolarize causing an action potential

• Two groups of nodal cells:– Sinoatrial (SA) node-makes 80-100 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

Figure 49.7 The Heartbeat

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

Figure 21.11 The Cardiac Cycle

The Cardiac Cycle

Fig 21.12

The electrical signal stimulates contraction of the chambers

Pressure in left ventricle

Pressure in aorta

P (

mm

Hg)

Left ventricular volume

V (

ml)

Ventriclecontracting

Rightatrium

Rightventricle Left

ventricle

Left atrium

Ventriclerelaxing

Figure 49.4 The Cardiac Cycle

EKG-electrocardiogram

• Surface electrodes can monitor the depolarization of the nodal and conducting fibers

• EKG graph gives electrical and mechanical diagnostic information

Figure 21.13 The ECG

• The stimulus for contraction is generated by pacemaker cells of the SA node.

The Autonomic Innervation of the Heart

• Modified by the ANS

• Modified by Hormones

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.

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

• 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

Normal Functional Heart Anatomy

Congenital Heart Defects

Congenital Heart Defects