Anatomy of the Heart

Dr. Asma’ HassanAnatomy DepartmentPusat Pengajian Sains

PerubatanUniversiti Sains Malaysia

Objectives

4. Describe the anatomy of the heart with regard to its

4.1. location and external features

4.2. internal features of the chambers

4.5. surface anatomy

Divisions of Mediastinum

Transverse thoracic plane• Anterior - sternal angle • Posterior - lower border of T4

I - Superior mediastinum

II - Inferior mediastinum: Anterior

Middle (pericardium & heart) Posterior

• The heart, pericardium and root of great vessels occupy themiddle mediastinum

Pericardium

Pericardium is a fibroseroussac surrounding the heart andthe root of great vessels

It consists of 2 components:1 - Fibrous pericardium2 - Serous pericardium

Pericardium1 - Fibrous Pericardium• a tough connective tissue • the outer layer which defines

the boundaries of middle mediastinum

• enclose heart & roots of great vessels

• fused with tunica adventitia of great vessels

• fused with central tendon of diaphragm

Blood supply: • internal thoracic artery and

its branches

Pericardium

2 - Serous Pericardium• It is a thin layerConsists of 2 parts:• Parietal layer

– lines the inner surface of fibrous pericardium

• Visceral layer (= epicardium) – lines the heart and forms

its outer covering– also lines the beginnings of

great vessels• Both layers are continuous

around roots of great vessels

Pericardium

2 - Serous Pericardium• Both parietal and visceral

layers are continuous around roots of great vessels

• Reflections of serous pericardium occur in 2 locations:

• Superior – surrounding the arteries, aorta and pulmonary trunk

• Posterior – surrounding the inferior and superior venae cavae and pulmonary veins

Nerve supply to Pericardium

1. Fibrous Pericardium• phrenic nerve

2. Serous pericardium• Parietal layer* – phrenic nerve

(C3, 4, 5) produces the pain in inflammation of pericardium

• Visceral layer – insensitive to pain

• Pain from heart (i.e. from muscle and vessels)

- sympathetic nerves

Pericardial cavity

• The potential space between parietal and visceral layers ofserous pericardium

• It contains a thin film of fluid• The potential space allows the movement of the heart

Pericardial Sinuses• A reflection of serous

pericardium forming recess or sinus

• Located dorsal to the heart

1 - Oblique pericardial sinus 2 - Transverse pericardial sinus

1 - Oblique pericardial sinus • a cul-de-sac between 2 left & 2 right pulmonary veins & IVC• “cardiac bursa”• posteriorly is the oesophagus• can be entered inferiorly

left right

Pericardial Sinuses

2 - Transverse pericardial sinus

• due to dorsal mesentery breaks down during development

• It is anterior to superior vena cava

• It is located posterior to ascending aorta and pulmonary trunk

• There is a communication from right to left sides

- The two sinuses are not continuous

Pulmonary trunk

Pulmonary veins

The Heart• Position – surfaces and margins

• Skeleton of the Heart

• Chambers of the Heart

Surfaces of the Heart

1. Anterior or sternocostal surface• right ventricle • both atria

2. Posterior surface or base• left atrium

3. Inferior / diaphragmatic surface• left ventricle • right ventricle

RV

RA

LA

LV

RV

LV

LA

Borders of the Heart

1. Right border• right atrium

2. Inferior border • right ventricle • left ventricle

3. Left border • left ventricle • auricle of left atrium

4. Apex • left ventricle

Apex Beat of the Heart

• Formed by inferolateral partof left ventricle

• Located slightly medial to surface projection of apex

• Corresponds to the left 5th intercostal space in adults

• A distance of 9 cm from median plane

Sternocostal Projections of Valves of the Heart

• sternocostal projections of valves do not necessarily correspond to the best site of auscultation

• this is due to deep location of heart in the chest

• auscultation is usually performed by listening through a stethoscope

ooo

o

O = sternocostal projectionX = point of auscultationArrows show blood flow

X

X

X

X

Sternocostal Projections of Valves & Auscultation Point

Valve Sternocostal Projection

Point of Auscultation

Pulmonic 3rd c.c., left sternal border

2nd left ICS, just lateral to sternal angle

Aortic 3rd ICS, left sternal border

2nd right ICS, just lateral to sternal angle

Mitral 4th c.c., left sternal border

5th left ICS, 9 cm lateral to midline

Tricuspid 4th ICS, midsternal 4th left ICS, just lateral to sternum

ICS- intercostal spacec.c. – costal cartilage

Layers of the Heart Wall

1. Epicardium (external layer)– Visceral layer of serous

pericardium– Smooth, slippery texture

to outermost surface

2. Myocardium– 95% of heart is cardiac

muscle

3. Endocardium (inner layer)– Smooth lining for

chambers of heart, valves and continuous with lining of large blood vessels

Skeleton of the Heart

• a pair of conjoined fibrous rings• forms a figure of 8• consists of dense connective

tissue• bound the following orifices:

– Atrioventricular orifice: separate muscles of atria

from ventricles

– Pulmonary orifice– Aortic orifice

Provides attachment for:• myocardial tissue • cusps of valvesFunction - keep orifices patent

External features of Right Atrium

• Main cavity• Right auricle

• Right auricle – overlies ascending aorta

• Sulcus terminalis – between right auricle and

right atrium

Internal features of Right Atrium

Crista terminalis• found on the inside which

forms ridge

Rough part: pectinate muscles• located in front • from crista terminalis to

auricle• derived from primitive atrium

Smooth part• derived from sinus venosus• posterior to crista terminalis

Internal features of Right Atrium

Interatrial septum • separate right atrium from left

atrium Fossa ovalis • a shallow depression• site of foramen ovale• floor of fossa is from the

persistent septum primum

Limbus fossa ovalis • upper margin• remnant of septum secundum

*

Interatrial septum

Openings of Right Atrium

1. Superior vena cava• opens in upper part of atrium• at the level of 3rd costal

cartilage

2. Inferior vena cava (IVC)• opens into lower part of

atrium• at level of 5th costal cartilage

Opening of Right Atrium

3. Right atrioventricular (tricuspid) orifice • located anterior to IVC opening• orifice is guarded by tricuspid

valve

4. Opening of coronary sinus• between right atrioventricular &

IVC orifices

Opening of coronary sinus

External features of Right Ventricle

• Atrioventricular groove seen• It forms most of the anterior

surface of heart• Also forms the inferior border

of heart• Superior part tapers to form

the conus arteriosus (or infundibulum)

• Conus arteriosus ends in the pulmonary trunk (arterial)

conus arteriosus

pulmonary trunk

Internal features of Right Ventricle

Trabeculae carneae• irregular muscular elevations

3 Papillary muscles:• Posterior, anterior and septal

papillary muscles

• Papillary muscles in the ventricles are connected to chordae tendineae

Fx: help to stabilise AV valves during ventricular contraction

Papillary

muscle

Trabeculae

carneae

Internal features of Right Ventricle

Septomarginal trabecula(moderator band)• extends from interventricular

septum to the base of anterior papillary muscle

• contain right bundle branch of atrioventricular bundle

Thick interventricularseptum - crescent shapecavity

Septomarginal

trabecula

Chordae tendineae

Internal features of Right Ventricle

Chordae tendineae• fibrous cords which connect

papillary muscle to valve cusps• it is attached to adjacent sides of

2 valve cusps

Conus arteriosus / Infundibulum • the funnel shape part that

leads to pulmonary trunk(arterial)

• It is thin and smooth

pulmonary artery

conus arteriosus

Right atrioventricular valve

• also known as tricuspid valve

• it guards the rightatrioventricular orifice

• located at the 4th intercostalspace

• has 3 valve cusps that isposterior, anterior and septal

Valves in systole

A

SP

Each heart valve has 2 or 3 cusps

Cusps of the Heart valves• The atrial surfaces are smooth• The ventricular surfaces are

irregular and rough

Attachment of valve cusps:• Its base attached to the fibrous

rings of heart skeleton

• The free edges and ventricular surfaces attached to the chordae tendineae

Functions of chorda tendineae:• prevent cusps from being driven

into right atrium when ventriclecontracts

• prevent regurgitation of blood

Chordae tendinae

Valve cusp

Pulmonary valve of Right Ventricle

Pulmonary valve• guards the pulmonary orifice• located at the 3rd costal

cartilage• has 3 semilunar cusps i.e.

– right, anterior and left

Pulmonary sinus • spaces at origin of

pulmonary trunk

SA

Pulmonary artery

pulmonary valve

External features of Left Atrium

• Main cavity• Left auricle – forms the left heart

border

• The size is smaller than right atrium but has thicker wall

• Forms most of the base of heart• Has a large area of smooth–

walled atrium• Has small muscular auricle called

pectinate muscleLA

External features of Left Atrium

• Left atrium forms the anterior wall of oblique sinus

• There are 4 pulmonary veins entering LA:– 2 superior pulmonary veins– 2 inferior pulmonary veins

Internal features• Left atrioventricular orifice is

guarded by the mitral valve• The mitral valve has 2 cusps:

anterior and posterior LA

Pulmonary veins

AP

Internal features of Left Ventricle

• forms the apex of the heart

Compare to right ventricle:• walls are 3x thicker• circular cavity• well-developed & numerous

trabeculae carneae• has 2 large papillary muscles:

anterior and posterior• no septomarginal trabecula

Chordae tendineae• similar to that of right

ventricle

Mitral valve of Left Ventricle

Mitral / bicuspid valve• guards left atrioventricular

orifice (between LA and LV)• located at 4th costal cartilage• has 2 cusps:

– anterior: large– posterior

Valve cusps• similar in structure to

tricuspid valve of rightventricle

AP

Anterior papillary

muscle

Posterior papillary muscle

Internal features of Left Ventricle

Aortic vestibule: • located below aortic orifice• it is a smooth part

3 Aortic sinuses: • superior to each valve• dilations of aortic wall

Right coronary artery• originate from the right

aortic sinus

Left coronary artery• originate from the left

aortic sinus

Aortic sinus

Aortic vestibule

Aortic valve of Left Ventricle

Aortic valve • guards aortic orifice

(between LV and aorta)• located at 3rd intercostal

space• has 3 semilunar cusps:

right, posterior and left

Right ventricle Left ventricle

Papillary muscles

3 2

Smooth wall part

conus arteriosus / infundibulum

aortic vestibule

Septomarginal trabecula

present absent

Shape of cavity crescent circular

Name of valves tricuspid: 4th ICS pulmonary: 3rd c.c.

mitral: 4th c.c. aortic: 3rd ICS

Thickness of wall

thin 3x thicker

Trabeculae carneae

less prominent well-developed, numerous

Difference between Right and Left Ventricles

Tricuspid and Bicuspid Valves

• chordae tendineae are inserted from one papillary muscle always into two free edges adjacent cusps

• the pull of chordae tendineae on cusps approximates their free edges

• this simultaneously prevents cusps to be inverted into atrium

Atrioventricular (AV) valves Semilunar valves

Right AV (tricuspid)- separates the right atrium from the right ventricle- prevent backflow into atrium

Pulmonary valve- separates the right ventricle from the pulmonary arteries- prevents backflow after ventricular contraction

Left AV (bicuspid / mitral)- separates the left atrium from the left ventricle- prevents backflow into atrium

Aortic valve- separates the left ventricle from the aorta- prevents backflow after ventricular contraction

The Heart Valves

References

1. Clinically oriented anatomy - Keith Moore

2. Gray’s anatomy for students- Drake

3. Clinical anatomy - Snell