4.2 heart.copeland.2010

Section 4.2 The Heart
 Chapter 18, pp. 661-687

 Keep an eye on the Forum over the next few days
for a new question

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

Heart Anatomy
 Approximately the size of your fist
 Two side-by-side pumps
 Location
 Superior surface of diaphragm
 Left of the midline, from 2nd rib to 5th intercostal
space
 Anterior to the vertebral column, posterior to the
sternum
 “mediastinum”


Heart Anatomy Broad, flat base points to rt. shoulder
Apex points to lt. hip

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 18.1

3 layers of the heart
 Pericardium
 Outer sac
 Myocardium
 Muscle, bulk of mass
 Endocardium
 Inner lining


Coverings of the Heart: Anatomy
 Pericardium – a double-walled sac around the heart
composed of:
 A superficial fibrous pericardium
 A deep two-layer serous pericardium
 The parietal layer lines the internal surface of
the fibrous pericardium
 The visceral layer or epicardium lines the
surface of the heart
 They are separated by the fluid-filled pericardial
cavity


Coverings of the Heart: Physiology
 The pericardium:
 Protects and anchors the heart
 Prevents overfilling of the heart with blood
 Allows for the heart to work in a relatively friction-
free environment
 Epicardium – visceral layer of the serous
pericardium


Pericardial Layers of the Heart


Heart Wall
 Myocardium – cardiac muscle layer forming the bulk of
the heart
 Branching muscle cells arranged in bundles
 Provides support for great vessels and valves
 Directs spread of action potentials across heart
 Fibrous skeleton of the heart – crisscrossing, interlacing
layer of connective tissue, insulation, supports great vessels
 Endocardium – endothelial layer of the inner myocardial
surface; continuous with vessels leaving and entering the
heart


Cardiac Muscle Bundles


External Heart: Major Vessels of the Heart
(Anterior View)
 Vessels returning blood to the heart include:
 Superior and inferior venae cavae, meaning?
 Right and left pulmonary veins
 Vessels conveying blood away from the heart:
 Pulmonary trunk, which splits into right and left pulmonary
arteries
 Ascending aorta (three branches) – brachiocephalic, left
common carotid, and subclavian arteries


External Heart: Vessels that Supply/Drain the
Heart (Anterior View)

 Arteries – right and left coronary (in
atrioventricular groove), marginal, circumflex, and
anterior interventricular arteries
 Veins – small cardiac, anterior cardiac, and great
cardiac veins


Brachiocephalic Left common
trunk carotid artery
Superior Left
vena cava subclavian artery
Aortic arch
Right
Ligamentum
pulmonary artery
arteriosum
Ascending Left pulmonary artery
aorta
Pulmonary trunk Left pulmonary veins
Left atrium
Right
pulmonary veins Auricle
Right atrium Circumflex
Right coronary artery
artery (in coronary Left coronary
sulcus) artery (in coronary
Anterior sulcus)
cardiac vein Left ventricle
Right ventricle
Marginal artery Great cardiac vein
Small cardiac vein Anterior
Inferior interventricular artery
(in anterior
vena cava interventricular sulcus)
Apex
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 18.4b

External Heart: Major Vessels of the Heart
(Posterior View)
 Vessels returning blood to the heart include:
 Right and left pulmonary veins
 Superior and inferior venae cavae
 Vessels conveying blood away from the heart
include:
 Aorta
 Right and left pulmonary arteries


External Heart: Vessels that Supply/Drain the
Heart (Posterior View)

 Arteries – right coronary artery (in atrioventricular
groove) and the posterior interventricular artery (in
interventricular groove)
 Veins – great cardiac vein, posterior vein to left
ventricle, coronary sinus, and middle cardiac vein


Aorta Superior
vena cava
Left Right
pulmonary artery pulmonary artery
Left
pulmonary veins Right
pulmonary veins
Auricle
of left atrium Right atrium
Left atrium
Inferior
Great cardiac vein vena cava
Right coronary
Posterior vein artery (in coronary
of left ventricle sulcus)
Coronary sinus
Posterior
interventricular artery
Left ventricle (in posterior
interventricular sulcus)
Apex Middle cardiac vein

(d) Right ventricle
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 18.4d

Aorta
Superior vena cava
Left
Right pulmonary artery
pulmonary artery Left atrium
Pulmonary trunk
Left
Right atrium pulmonary veins
Right
pulmonary veins Mitral
Fossa (bicuspid-2 flaps)
ovalis valveAortic
Pectinate valve
Pulmonary
muscles valve
Tricuspid Left ventricle
Valve (3 flaps)
Papillary
Right ventricle
muscle
Chordae Interventricular
tendineae septum
Trabeculae Myocardium
carneae Visceral
Inferior pericardium
vena cava Endocardium
(e)
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 18.4e

Atria of the Heart
 Atria are the receiving chambers of the heart
 Each atrium has a protruding auricle
 Pectinate muscles mark atrial walls
 Blood enters right atria from superior and inferior
venae cavae and coronary sinus
 Blood enters left atria from pulmonary veins


Ventricles of the Heart
 Ventricles are the discharging chambers of the
heart
 Papillary muscles and trabeculae carneae muscles
mark ventricular walls
 Right ventricle pumps blood into the pulmonary
trunk
 Left ventricle pumps blood into the aorta


Right and Left Ventricles


Pathway of Blood Through the Heart and
Lungs
 Right atrium  tricuspid valve  right ventricle
 Right ventricle  pulmonary semilunar valve 
pulmonary arteries  lungs
 Lungs  pulmonary veins  left atrium
 Left atrium  bicuspid valve  left ventricle
 Left ventricle  aortic semilunar valve  aorta
 Aorta  systemic circulation


Aorta
Superior vena cava
Left
Right pulmonary artery
pulmonary artery Left atrium
Pulmonary trunk
Left
Right atrium pulmonary veins
Right
pulmonary veins Mitral
Fossa (bicuspid) valve
ovalis Aortic
Pectinate valve
Pulmonary
muscles valve
Tricuspid Left ventricle
valve
Papillary
Right ventricle
muscle
Chordae Interventricular
tendineae septum
Trabeculae Myocardium
carneae Visceral
Inferior pericardium
vena cava Endocardium
(e)
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 18.4e

Pulmonary circuit:
Shorter, low
pressure

Systemic circuit:
Long pathway, 5x
pressure (more
resistance)


2 side-by-side pumps


Coronary Circulation
 Coronary circulation is the functional blood supply
to the heart muscle itself
 Collateral routes ensure blood delivery to heart
even if major vessels are occluded

Left coronary artery Right coronary artery
anterior circumflex marginal posterior
interventricular artery artery interventricular
artery artery
interventricular left atrium lateral right posterior right
septum & & posterior side of ventricular
anterior walls walls of left heart (incl walls
of both ventricle right atrium
ventricles

Coronary circulation

• many anastomoses, which provide alternate routes for nourishment if a
given artery begins to be occluded - but total occlusion means ????
(1) actively deliver blood when heart is relaxed
(2) largely ineffective when ventricles contracting because??
• heart ~1/200 of body but requires ~1/20 of blood supply (esp. left ventricle)

Coronary venous supply:
from capillaries → cardiac veins (great,
middle & small) → coronary sinus →
right atrium
also some anterior cardiac veins →
directly into right atrium anteriorly


Heart Valves
 Heart valves ensure unidirectional blood flow
through the heart
 Atrioventricular (AV) valves lie between the atria
and the ventricles
 AV valves prevent backflow into the atria when
ventricles contract
 Chordae tendineae anchor AV valves to papillary
muscles


Heart Valves
 Aortic semilunar valve lies between the left
ventricle and the aorta
 Pulmonary semilunar valve lies between the right
ventricle and pulmonary trunk
 Semilunar valves prevent backflow of blood into
the ventricles
 No valves for vena cavae and pulmonary veins!


Atrioventricular Valve Function


Semilunar Valve Function


Microscopic Anatomy of Heart Muscle
 Cardiac muscle is striated, short, fat, branched, and
interconnected
 The connective tissue endomysium acts as both
tendon and insertion
 Intercalated discs anchor cardiac cells together and
allow free passage of ions
 Heart muscle behaves as a functional syncytium

PLAY InterActive Physiology ®:
Anatomy Review: The Heart, pages 3–7


Microscopic Anatomy of Cardiac Muscle

•1 or 2 nuclei/cell

•full of mitochondria
(25% vs 2% skeletal)

•Resist fatigue


4.2 heart.copeland.2010

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