0103 10am Anatomy of the Heart and Pericardium

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Learning Objectives:

1. Discern the layers of the pericardium, innervation and associated sinuses

a. The heart is surrounded by the pericardium.

i. The fibrous pericardium is the outermost layer. It is separated from the mediastinal pleura of the lungs by the

phrenic nerve and the pericardiophrenic vessels.

1. Pericarditis or pleuritis may lead to referred pain in dermatomes C3-5 due to inflammation of the phrenic ne

ii. The serous pericardium underlies the fibrous pericardium and consists of two layers, the parietal which directly

derlies the fibrous and the visceral (aka epicardium) which directly overlies the heart. The two serous layers are

vided by the pericardial cavity.

b. Pericardial sinuses are reflections of the parietal serous pericardium around major vessels. There are two - the obliq

sinus which is bounded by the pulmonary veins and superior and inferior vena cavae, and the transverse which is

bounded by the pulmonary trunk/ascending aorta anteriorly and atria posteriorly.

2. Describe the anatomic basis of cardiac tamponade

a. Cardiac tamponade is the compression of the heart due to accumulation of fluid (pericardial effusion) in the pericardi

cavity. It can be caused by pericarditis.i. The compression of the heart muscle minimizes its ability to contract, and is characterized by weak/rapid pulse,

dyspnea, JVD, and reduced cardiac output.

3. Explain the characteristics and relationships of atria and ventricles

a. The heart consists of two atria and two ventricles.

b. The interatrial septum separates the two atria

c. The interventricular (membranous and muscular parts) separates the two ventricles

d. The atrioventricular separates the left ventricle from the right atrium

e. The coronary sulcus is between the atria and ventricles, and contains the coronary sinus, beginnings of the coron

arteries, and the small cardiac vein.

f. The interventricular sulci are between the ventricles. The anterior i.s. contains the left anterior descending (LAD

artery (aka anterior interventricular artery of the left coronary artery) and the great cardiac vein. The posterior i.s. c

tains the posterior interventricular artery of the right coronary artery and the middle cardiac vein.

g. Right atrium

i. Derived from the sinus venarum and primitive atrium which are separated by the crista terminalis that contains

sinuatrial (SA) node.

1. The sinus venosus receives the superior/inferior vena cavae and coronary sinus. It contains the fossa ova

a. The inferior v.c. and coronary sinus openings are guarded by the eustachian and thebesian valves, res

tively.

2. The primitive atrium contains pectinate muscles and right auricle

h. Right ventricle

i. Made up of proper right ventricle (inflow) and pulmonary vestibule (infundibulum) (outflow) separated by su

praventricular crest1. Proper right ventricle: trabeculae carnea; anterior/posterior/septal papillary muscles connected to the tr

cuspid valve (separates right atrium from ventricle) cusps via chordae tendinea; trabeculae septomargin

(transmits right branch of AV bundle)

2. Infundibulum: continues with pulmonary trunk guarded by semilunar pulmonary valve which divides into

right/left pulmonary arteries, the left being connected to the aortic arch via the ligamentum arteriosum

a. Pulmonary hypertension = pulmonary artery wall and its smaller vessels become damaged, resulting in

narrowing of the lumen and hypertrophy of R. ventricle and restricting blood flow to lungs exertional

dyspnea

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Anatomy of the Heart & Pericardium [Arslan]


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i. Left atrium

i. Left auricle; receives pulmonary veins;

ii. Lies anterior to esophagus

1. Mitral stenosis

dilation of left atrium

compression of esophagus (and bronchi)

dysphagia(and dyspnea)

j. Left ventricle

i. Made up of proper left ventricle (inflow) and aortic vestibule (outflow)

1. Proper left ventricle: trabeculae carnea; anterior/posterior papillary muscles connected to mitral (bicuspid) v

(connection to left atrium) via chordae tendineae

a. Mitral stenosis (see above)

b. Mitral valve prolapse

2. Aortic vestibule: leads to ascending aorta guarded by semilunar aortic valve which surrounds the 3 aortic si

nuses (of Valsalva), 2 of which contain ostia for the right/left coronary arteries

a. Aortic stenosis = usually congenital, associated with hypertrophy of L. ventricle and regurgitation of blo

into lungs exertional dyspnea, angina, syncope, cardiac murmur, dec. BP, rising carotid pulse

4. Verify the role of autonomic nervous system in the transmission of cardiac pain

a. Sympathetic segmental contribution is responsible for referred cardiac pain - visceral afferents accompany the symp

thetic fibers (from T1-T4), the somatic afferents and visceral afferents both travel together in the dorsal root and conv

on a single ascending secondary neuron. when the pain travels up the AL tract it is interpreted as originating from the

somatic sensory nerves (because pain felt in the skin is more common) leading to the perception of a diffuse referred

pain in the T1-T4 dermatomes.

5. State the areas of distribution of the coronary arteries

a. Ascending aorta right coronary artery right marginal and posterior interventricular arteries

i. R.C. Artery = dominant; supplies SA and AV nodes, posterior and anterior surface of the heart

b. Ascending aorta

left coronary artery

LAD and circumflexi. LAD supplies anterior surface of ventricles, interventricular septum

ii. Circumflex supplies left atrium and upper left ventricle

1. Gives rise to posterior interventricular artery in left dominant coronary circulation

6. Describe the course, sites of drainage and relationships of the cardiac veins

a. Coronary sulcus: coronary sinus, small cardiac vein

b. Anterior interventricular sulcus: great cardiac vein

c. Posterior interventricular sulcus: middle cardiac vein

7. Outline the location of the elements of the conduction system

a. Sinuatrial (SA) node - adjacent to crista terminalis of right atrium

b. Internodal tracts - connect SA and AV node

c. Atrioventricular (AV) node - right interatrial septum, adjacent to ostium of coronary sinus

d. Bundle of His - along posterior border of membranous interventricular septum

i. Divides into left and right branches that perfuse the ventricles

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Notes:

1. Heart & Pericardium

a. Heart is invested by the pericardium, which con-

sists of fibrous and serous pericardiumi. Fibrous pericardium

1. continues with the adventitia of aorta

and pulmonary trunk

2. connected to the sternum via the ster-

nopericardial ligaments

3. separated from the mediastinal pleura

(medial side of lungs) by the phrenic

nerve and pericardiocophrenic vessels

a. Pain due to pericarditis and pleuritis may project to dermatomes C3, C4 & C5 (due to inflamm

tion of the phrenic nerve)

ii. Serous pericardium

1. Consists of parietal & visceral (epicardium) layers separated by the pericardial cavity

a. Pericardial effusion due to pericarditis --> fills the pericardial cavity --> cardiac tamponade (c

pression of heart due to accumulation of fluid; characterized by weak and rapid pulse, dyspn

JVD (jugular venous distention), reduced cardiac output)

2. Pericadiocentesis

a. Aspiration of pericardial content is accomplished through subcostal or

parasternal route to ensure that damage to the left anterior descending and

right marginal arteries as well as the pleural cavity (pneumothorax) is

avoidedb. In subcostal approach, a needle is introduced through the left xiphisternal

angle (45)

c. In parasternal route, a needle is introduced through the left 3rd or 4th inter-

costal space, lateral to the internal thoracic artery

3. Pericardial Sinuses (contain nothing)

a. Recesses formed by reflections of the parietal layer of the serous pericardium

around major vessels of the heart:

i. Oblique: bounded by the pulmonary veins and superior and inferior vena

cava

ii. Transverse: lies between the ascending aorta and pulmonary trunk anteriorly

and the atria posteriorly

1. used to place a ligature around the pulmonary trunk and aorta to stop

circulation and to insert coronary bypass machine

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4. Heart

a. Located in the middle mediastinum, medial to the lungs,

posterior to the thymus, sternum and 3rd to 5th costae, and

anterior to the esophagus and descending aortab. Consists of atria & ventricles separated by the coronary

sulcus

c. has a base, apex, sternocostal and diaphragmatic surfaces

i. Base- consists of left atrium & small portion of the right

atrium

ii. Apex- left ventricle, lies posterior

to the 5th intercostal space at the

point of intersection with the mid-

clavicular line- Apical pulse (PMI-

point of maximal impulse) below

the nipple

iii. Sternocostal surface- formed

mainly by the right ventricle

with small contribution from

the left ventricle

iv. Diaphragmatic surface-

formed primarily by the left

ventricle with small contribu-

tion from the right ventricle

d. Heart exhibits two sets of sulci

i. coronary sulcus- separatesatria from ventricles

1. contains the coronary

sinus posteriorly, initial

part of coronary arteries, and the small cardiac vein

ii. Interventricular sulci are divisible into:

1. Anterior Interventricular sulcus: contains the anterior interventricular artery and great cardiac vein

2. Posterior interventricular sulcus: contains the posterior interventricular artery and middle cardiac

e. Right atrium

i. Derived embryologically from the sinus venarum and primitive atrium,

which are separated by the crista terminalis - contains the sinuatrial node

ii. Primitive atrium- contains pectinate muscles and auricle (potential site of

thrombi)

iii. Fossa ovalis - remnant of foramen ovale

iv. Sinus venosus receives the superior and inferior vena cavae, and coro-

nary sinus

v. Inferior vena cava and coronary sinus openings are guarded by a primitive (Eustachian &Thebesian)

valves, respectively

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f. Right ventricle

i. Consists of the proper ventricle and the vestibule (infundibulum),

which are separated by the supraventricular crest

1. Proper right ventricle (inflow) contains:a. Trabeculae carnea

b. Ant., post. & septal papillary muscles connected via chor-

dae tendinea to the cusps of tricuspid valve that guards the

right atrioventricular orifice

i. Trabeculae septomarginalis (moderator band)

1. extends from the base of anterior papillary muscle

to the septal wall

2. transmits the right branch of AV bundle

2. Infundibulum (pulmonary vestibule) represents the outflow

part of right ventricle

a. continues with the pulmonary trunk guarded by the semilunar pulmonary valves

b. Pulmonary trunk divides into R & L pulmonary arteries. Left pulmonary artery is connected to

aortic arch via the ligamentum arteriosum (remnant of ductus arteriosus)

g. Pulmonary Hypertension

i. An obliterative condition that affects small and medium pulmonary arteries

ii. Hyperplasia and scar tissue narrowing of the lumen increased pulmonary arterial pressure in

creased resistance to blood flow to the lungs alveolar hypoxia

iii. Associated with hypertrophy of the R-ventricle and shrinkage of the L-ventricle

iv. Exertional dyspnea is common, however syncope and substernal angina may also be seen

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h. Left atrium

i. extends as the left auricle,

which is the potential site of

thrombiii. receives the pulmonary

veins

iii. lies anterior to the

esophagus

1. mitral stenosis results in

dilation of the left atrium,

compression of the

esophagus, and the resultant dysphagia

i. Left ventricle

i. Consists of the proper left

ventricle & aortic vestibule

1. Proper ventricle contains:

a. Trabeculae carnea

b. Anterior and posterior

papillary muscles,

which are connected

to the bicuspid valve

via the chorda tendi-

nea

2. Aortic vestibulea. Located superior to and to the right of the mitral valve- leads to the ascending aorta

i. Ascending aorta- located in the middle mediastinum; contains the aortic (of Valsalva) si-

nuses and valves

j. Aortic Stenosis

i. Congenital except when the valve undergoes sclerosis as a result of

endocarditis

ii. Associated with left ventricular hypertrophy and increase pressure in LV

and regurgitation of blood into the lungs

iii. Patients exhibit dyspnea on exertion (associated with regurgitated

blood in the lung), angina (chest pain- due to insufficient blood in the

heart) and syncope (reduced blood to the brain)

iv. Physical exam reveals cardiac murmur, decrease in blood pressure, and rising carotid pulse also occ

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k. Mitral Valve

i. Left ventricle is connected to the left atrium via the left atrioven-

tricular orifice guarded by the bicuspid mitral valve

ii. Mitral valve stenosis may occur subsequent to rheumatic fever& syphilis dilation of the left atrium and pulmonary veins

compression of esophagus & bronchi dysphagia & dyspnea

iii. Mitral Valve Prolapse

1. Protrusion of the mitral valve into the left atrium

a. familial condition

b. most common cardiac problem (5-25% )

c. Affect all ages; women are predominantly affected

d. patients exhibit chest pain, shortness of breath, anxiety and/or

panic attacks, low exercise tolerance, chronically cold hands

and feet, numbness or tingling of the arms or legs and diffi-

culty swallowing

l. Cardiac Septae (3)

i. Interatrial septum - separates the

atria (contains fossa ovale)

ii. Interventricular septum- separates

the ventricles

1. Membranous part- common site

of VSD

2. Muscular part

iii. Atrioventricular septum- separates

the right atrium from the left ventricle

m. Cardiac Skeleton

i. Maintains patency of the AV and semilunar valves

ii. Provides attachment to cardiac muscles and cusps of the cardiac

valves

iii. Secure independent contraction of the atria and ventricles

iv. Consists of:

1. Fibrous trigones

2. Right and left atrioventricular rings

3. Aortic ring

4. Pulmonary ring

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n. Cardiac Layers

i. Epicardium- composed of mesothelial cells and contains

adipose tissue and cardiac vessels and nerves

ii. Myocardium- consists of specialized skeletal (cardiac)muscles that attach to the skeleton of the heart

iii. Endocardium- lines the heart, consists of endothelial cells

1. thickening of the endocardium contributes to the forma-

tion of the cardiac valves

2. contains elements that mediate cardiac conduction

o. Conduction System

i. Maintains autorhythmicity of the myocardial muscle contraction

ii. Consists of the:

1. Sinuatrial (SA) node located adjacent to the crista terminalis

2. Internodal tracts connect the SA and AV nodes

3. Atrioventricular (AV) node lies in the right interatrial septum, ad-

jacent to the ostium of coronary sinus

4. Atrioventricular (HIS) bundle

a. descends along the posterior border of the membranous

interventricular septum

b. divides into left and right branches

5. Cardiac Plexus

a. Consists of

i. parasympathetic fibers that emanate from the vagus nerveii. sympathetic fibers- that arise from T1-T4(T5)

b. Sympathetic segmental contribution is responsible for referred cardiac pain

6. Coronary Arterial Ischemia

a.Pain associated with ischemia induced coronary artery

occlusion refers to the precordium (angina pectoris), epi-

gastrium, shoulder, jaw, and frequently, left arm

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7. Ascending Aorta

a. Lies on the right side of the

pulmonary trunk

b. Forms a content of the middlemediastinum

c. Constitutes the anterior wall of

the transverse pericardial sinus

d. Gives rise to the right and left

coronary arteries

e. Ascending aorta is guarded by

the aortic semilunar valve that

surround aortic sinuses

f. Two of the aortic sinuses con-

tain ostia (openings) for the right and left coronary arteries

8. Right Coronary Artery

a. Dominant artery

b. Supplies the SA and AV

nodes, posterior (and an-

terior) surface of the heart

c. Gives rise to the right

marginal and posterior

interventricular branches

d. Dominance of a coronary

artery is determined by the origin of the posterior interventricularartery

9. Coronary Arteries

a. Left coronary artery- gives rise to the LAD and circumflex branches

i. Anterior interventricular artery (LAD) supplies the anterior surfaces of

ventricles and interventricular septum

ii. Circumflex artery- supplies the left atrium & upper left ventricle and

gives rise to the posterior interventricular artery in left dominant coro-

nary circulation

0103 10am B3T1

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0103 10am Anatomy of the Heart and Pericardium

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