The Heart Part 1 Slides by Vince Austin and W. Rose. figures from Marieb & Hoehn 8 th and 9 th eds. Portions copyright Pearson Education

The HeartPart 1

Slides by Vince Austin and W. Rose.

figures from Marieb & Hoehn 8th and 9th eds.

Portions copyright Pearson Education

Copyright © 2010 Pearson Education, Inc.

Heart Anatomy

• Approximately the size of a fist

• Location

• In the mediastinum between second rib and fifth intercostal space

• On the superior surface of diaphragm

• Two-thirds to the left of the midsternal line

• Anterior to the vertebral column, posterior to the sternum

• Enclosed in pericardium, a double-walled sac

PLAYPLAY Animation: Rotatable heart

Copyright © 2010 Pearson Education, Inc. Figure 18.1c

(c)

Superiorvena cava

Left lung

AortaParietalpleura (cut)

Pericardium(cut)

Pulmonarytrunk

Diaphragm

Apex ofheart

Pericardium

Two layers

Parietal layer (“pericardium”) a clear fibrous “bag” protecting & anchoring heart. Limits filling beyond a certain volume.

Visceral layer (epicardium) on external surface of the heart

Very thin layer of fluid between the layers - decreases friction

Layers of the heart wall

• Epicardium (visceral pericardium)

• Myocardium (muscle)

• Endocardium (inner lining)

http://dev.biologists.org/content/139/18/3277/F1.large.jpg

Cardiac Chambers: 2 ventricles, 2 atria

Two atria•Separated internally by interatrial septum•Coronary sulcus (atrioventricular groove) encircles junction of atria and ventricles•Auricles increase atrial volume

Two ventricles•Separated by interventricular septum•Anterior & posterior interventricular sulci on external surface suggest location of septum inside

Copyright © 2010 Pearson Education, Inc. Figure 18.4b

(b) Anterior view

Brachiocephalic trunk

Superior vena cava

Right pulmonaryarteryAscending aortaPulmonary trunk

Right pulmonaryveins

Right atrium

Right coronary artery(in coronary sulcus)Anterior cardiac vein

Right ventricle

Right marginal artery

Small cardiac vein

Inferior vena cava

Left common carotidarteryLeft subclavian artery

Ligamentum arteriosum

Left pulmonary artery

Left pulmonary veins

Circumflex artery

Left coronary artery(in coronary sulcus)

Left ventricle

Great cardiac vein

Anterior interventricularartery (in anteriorinterventricular sulcus)

Apex

Aortic arch

Auricle ofleft atrium

Atria: The Receiving Chambers

Vessels entering right atrium•Superior vena cava •Inferior vena cava•Coronary sinus

Vessels entering left atrium•Right and left pulmonary veins

Ventricles: The Discharging Chambers

Walls are ridged by trabeculae carneae

Papillary muscles project into the ventricular cavities

Pulmonary trunk leaves right ventricle

Aorta leaves left ventricle

Copyright © 2010 Pearson Education, Inc. Figure 18.4e

Aorta

Left pulmonaryarteryLeft atriumLeft pulmonaryveins

Mitral (bicuspid)valve

Aortic valve

Pulmonary valveLeft ventricle

Papillary muscleInterventricularseptumEpicardiumMyocardiumEndocardium

(e) Frontal section

Superior vena cava

Right pulmonaryarteryPulmonary trunk

Right atrium

Right pulmonaryveinsFossa ovalisPectinate muscles

Tricuspid valveRight ventricle

Chordae tendineae

Trabeculae carneae

Inferior vena cava

Pathway of Blood Through the Heart

The heart is two side-by-side pumps

Right side pumps blood to & through pulmonary (lung) arteries & veins

Left side pumps blood to & through systemic arteries & veins (everything but lungs)

Copyright © 2010 Pearson Education, Inc. Figure 18.5

Oxygen-rich,CO2-poor bloodOxygen-poor,CO2-rich blood

Capillary bedsof lungs wheregas exchangeoccurs

Capillary beds of allbody tissues wheregas exchange occurs

Pulmonary veinsPulmonary arteries

PulmonaryCircuit

SystemicCircuit

Aorta and branches

Left atrium

Heart

Left ventricleRight atrium

Right ventricle

Venae cavae

Blood pathway through right side of heartSystemic veins Right atrium tricuspid valve right ventricle

Right ventricle pulmonary (semilunar) valve pulmonary trunk pulmonary arteries lung capillaries

Blood pathway through left side of heartPulmonary veins Left atrium mitral valve left ventricle

Left ventricle aortic (semilunar) valve ascending aorta systemic arteries systemic capillaries


Pathway of Blood Through the Heart

• Equal volumes of blood are pumped to the pulmonary and systemic circuits

• Pulmonary circuit is a short, low-pressure circulation

• Systemic circuit blood encounters much resistance in the long pathways

• Anatomy of the ventricles reflects these differences


Rightventricle

Leftventricle

Interventricularseptum


Coronary Circulation

• The functional blood supply to the heart muscle itself

• Arterial supply varies considerably and contains many anastomoses (junctions) among branches

• Collateral routes provide additional routes for blood delivery


Coronary Circulation

• Arteries

• Right and left coronary (in atrioventricular groove), marginal, circumflex, and anterior interventricular arteries

• Veins

• Small cardiac, anterior cardiac, and great cardiac veins

Copyright © 2010 Pearson Education, Inc. Figure 18.7a

Rightventricle

Rightcoronaryartery

Rightatrium

Rightmarginalartery

Posteriorinterventricularartery

Anteriorinterventricularartery

Circumflexartery

Leftcoronaryartery

Aorta

Anastomosis(junction ofvessels)

Leftventricle

Superiorvena cava

(a) The major coronary arteries

Left atrium

Pulmonarytrunk


Superiorvena cava

Anteriorcardiacveins

Small cardiac vein

Middle cardiac vein

Greatcardiacvein

Coronarysinus

(b) The major cardiac veins

Copyright © 2010 Pearson Education, Inc. Figure 18.4d

(d) Posterior surface view

Aorta

Left pulmonaryartery

Left pulmonaryveinsAuricle of leftatriumLeft atrium

Great cardiacvein

Posterior veinof 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

Posteriorinterventricularartery (in posteriorinterventricular sulcus)Middle cardiac veinRight ventricle


Homeostatic Imbalances

• Angina pectoris

• Thoracic pain caused by a fleeting deficiency in blood delivery to the myocardium

• Cells are weakened

• Myocardial infarction (heart attack)

• Prolonged coronary blockage

• Areas of cell death are repaired with noncontractile scar tissue


Heart Valves

• Ensure unidirectional blood flow through the heart

• Atrioventricular (AV) valves

• Prevent backflow into the atria when ventricles contract

• Tricuspid valve (right)

• Mitral valve (left)

• Chordae tendineae anchor AV valve cusps to papillary muscles


Heart Valves

• Semilunar (SL) valves

• Prevent backflow into the ventricles when ventricles relax

• Aortic semilunar valve

• Pulmonary semilunar valve


Pulmonary valveAortic valveArea of cutaway

Mitral valveTricuspid valve

Myocardium

Tricuspid(right atrioventricular)valveMitral(left atrioventricular)valveAorticvalve

Pulmonaryvalve

(b)



Myocardium

Tricuspid(right atrioventricular)valve

(a)

Mitral(left atrioventricular)valveAortic valve

Pulmonaryvalve

Fibrousskeleton

Anterior




Myocardium

Tricuspid(right atrioventricular)valveMitral(left atrioventricular)valveAorticvalve

Pulmonaryvalve

(b)

Copyright © 2010 Pearson Education, Inc. Figure 18.8c

Pulmonaryvalve

AorticvalveArea ofcutawayMitralvalve

Tricuspidvalve

Chordae tendineaeattached to tricuspid valve flap

Papillarymuscle

(c)

Copyright © 2010 Pearson Education, Inc. Figure 18.8d

PulmonaryvalveAortic valveArea of cutawayMitral valveTricuspidvalve

Mitral valve

Chordaetendineae

Interventricularseptum

Myocardiumof left ventricle

Opening of inferiorvena cava

Tricuspid valve

Papillarymuscles

Myocardiumof rightventricle

(d)

The short axis view is a plane perpendicular to a line from the apex of the heart along the interventricular septum to the approximate middle of the base of the heart.“This short axis slice of the specimen beautifully shows the annulus of the mitral valve. Additionally, the left circumflex artery can be seen curving around heart above the mitral annulus and the left anterior descending artery diving down into the myocardium adjacent to the pulmonary valve annulus.” Note how the mitral and aortic valves share parts of their annuli.Source: Atlas of Human Cardiac Anatomy, heart 0053, http://www.vhlab.umn.edu/atlas/cardiac-mri/short-axis-valve/index.shtml, retrieved 20150228.

Cardiac MRI of a preserved human heart. Short axis view at the level of the valves.

http://www.vhlab.umn.edu/atlas/cardiac-mri/short-axis-valve/index.shtml


1 Blood returning to theheart fills atria, puttingpressure againstatrioventricular valves;atrioventricular valves areforced open.

1 Ventricles contract, forcingblood against atrioventricularvalve cusps.

2 As ventricles fill,atrioventricular valve flapshang limply into ventricles.

2 Atrioventricular valvesclose.

3 Atria contract, forcingadditional blood into ventricles.

3 Papillary musclescontract and chordaetendineae tighten,preventing valve flapsfrom everting into atria.

(a) AV valves open; atrial pressure greater than ventricular pressure

(b) AV valves closed; atrial pressure less than ventricular pressure

Direction ofblood flow

Atrium

Ventricle

Cusp ofatrioventricularvalve (open)

Chordaetendineae

Papillarymuscle

Atrium

Blood inventricle

Cusps ofatrioventricularvalve (closed)


As ventriclescontract andintraventricularpressure rises,blood is pushed upagainst semilunarvalves, forcing themopen.

As ventricles relaxand intraventricularpressure falls, bloodflows back fromarteries, filling thecusps of semilunarvalves and forcingthem to close.

(a) Semilunar valves open

(b) Semilunar valves closed

Aorta

Pulmonarytrunk


Microscopic Anatomy of Cardiac Muscle

• Cardiac muscle cells are striated, short, fat, branched, and interconnected

• Connective tissue matrix (endomysium) connects to the fibrous skeleton

• T tubules are wide but less numerous; SR is simpler than in skeletal muscle

• Numerous large mitochondria (25–35% of cell volume)


Nucleus

DesmosomesGap junctions

Intercalated discs Cardiac muscle cell

(a)


Microscopic Anatomy of Cardiac Muscle

• Intercalated discs: junctions between cells anchor cardiac cells

• Desmosomes prevent cells from separating during contraction

• Gap junctions allow ions to pass; electrically couple adjacent cells

• Heart muscle behaves as a functional syncytium


Nucleus

Nucleus

I bandA band

Cardiacmuscle cell

Sarcolemma

Z disc

Mitochondrion

Mitochondrion

T tubule

Sarcoplasmicreticulum

I band

Intercalateddisc

(b)

Documents

The Heart Part 1 Slides by Vince Austin and W. Rose. figures from Marieb & Hoehn 8 th and 9 th eds. Portions copyright Pearson Education