2sheath of thoracic anatomy for medical students

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Thoracic Anatomy for Medical Students

Lecture Notes

By

Dr Ahmed M.Sulaiman, M.B.B.CH, Msc, DHE, PhD

Ass. Prof. of Anatomy and Embryology

Faculty of Medicine, Tripoli University

Part two

Thoracic Cavity

The cavity of thorax is completely filled laterally by the lungs.

• Each lung surrounded by the pleura in between its two layers is the pleural cavity

• Space between the pleural cavities occupying the centre of the thoracic cavity is

the mediastinum.

Mediastinum

Space between the two pleural sacs, its mobile partition , it extends from

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superiorly : Thoracic inlet and the root of neck ,

Inferiorly : diaphragm ,

anteriorly : sternum.

Posteriorly: The 12 thoracic vertebrae .

Divisions:

For purposes of description it is divided by imaginary plane passing from the sternal angle

anteriorly to the lower border of the body of the 4th thoracic vertebrae into:

• 1. Superior mediastinum

• 2. Inferior mediastinum :( Anterior , middle, posterior)

Superior mediastinum:

• lies above the plane joining the sternal angle and

• lower border of 4th thoracic vertebrae.

• Bounded in front by the manubrium sterni.

• Behind by the first four thoracic vertebrae

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Contents of superior mediastinum:

Trachea, large veins, large arteries. Thymus, esophagus, thoracic duct, sympathetic

trunk .

Inferior mediastinum:

lies below the plane joining the sternal angle and the lower border of the 4th thoracic

vertebrae.

Bounded in front by the body of the sternum.

Behind by the lower eight thoracic vertebrae.

It is subdivided into:

Anterior mediastinum :( space between the pericardium and the sternum ), it contains the

thymus or its remnants , sternopericardial ligaments, few lymph nodes and branches of

internal thoracic vessels.

middle mediastinum which contains:

Pericardium .

Heart.

Posterior mediastinum :

space posterior to the pericardium and the sloping upper part of the diaphragm and

bounded posteriorly by the thoracic vertebrae 5-12 the vertebral column), it contains:

esophagus.

thoracic aorta.

Azygos vein, hemiazygos and accessory

hemiazygos veins.

thoracic duct .

lymph nodes.

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Thymus :

It consists of two lobes ( right and left), closely applied to each other , and may appear as

single organ.

It is the site of T (thymic ) lymphocytes, it has large size in newborn ,and it continues to

grow and in infant it may extends from the level of 4th costal cartilage to the lower pole of

thyroid gland .

after puberty it undergo involution.

Relations of thymus

Anterior Relation :

sternohyoid muscle, sternothyroid muscles, manubrium and upper part of the body of

sternum, and their adjacent costal cartilage.

Posterior Relation :

Pericardium, arch of aorta with its large three branches, left brachiocephalic vein and

Trachea.

Blood supply:

• Inferior thyroid artery

• Internal thoracic artery

Veins corresponding to arteries , but frequently large short thymic vein drain into the left

brachiocephalic vein.

Lymph drainage:

• Efferent into parasternal and tracheobronchial nodes.

• Afferent : thymus does not receive any afferent

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PLEURA AND PLEURAL CAVITY

Pleura:

The pleura is a thin membrane of fibrous tissue surfaced by a single layer of flat cells (

mesothelium) , it clothes each lung and lines the thoracic cavity, it has two layers

Parietal layer:

lines the thoracic wall from which it is separated by loose areolar tissue( endothoracic

fascia).

It is attached to the inferior surface of the suprapleural membrane , and to the

mediastinal surface of the fibrous pericardium.

At the lung root it projected around it , part of it hangs down below as an empty fold(

pulmonary ligament) to allow expansion of vessels in the lung root, especially inferior

pulmonary vein.

Layers of the pleura:

1`.Parietal layer :

it lines the thoracic wall , it separated from it b y the endothoracic fascia, its attached to

inferior surface of the suprapleural membrane.

2.Visceral layer:

Which extends to the depths of the interlobar clefts and is adherent to lung surface.

The two layers are separated by pleural cavity which completely closed spac.

Parts :

1. Diaphragmatic pleura: Part of the pleura covering the diaphragm.

2. Costal pleura : Part of the pleura related to the ribs and intercostal spaces.

3. Mediastinal pleura : part of the pleura covering the mediastinum.

4. Cervical pleura : The dome shaped layer lining part of pleural cavity which

extends into the neck.

Boundaries of the pleural sac

Can be marked on the surface of the body by lines which indicate the limits of the

parietal pleura reflection it is called lines of pleural reflection

Diaphragmatic pleura: Part of the pleura covering the diaphragm.

: Part of the pleura related to the ribs and intercostal spaces.

Mediastinal pleura : part of the pleura covering the mediastinum.

Cervical pleura : The dome shaped layer lining part of pleural cavity which

ral sac( Pleural reflection):


parietal pleura reflection it is called lines of pleural reflection

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: Part of the pleura related to the ribs and intercostal spaces.

Cervical pleura : The dome shaped layer lining part of pleural cavity which


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1. Cervical pleura:

A curved line , convex upward , drawn from the sternoclavicular joint to a point 2.5 cm

above the junction of the medial and intermediate third of the clavicle.

2. Anterior border:

Right pleura:

A line runs down behind the sternoclavicular joint almost reaching the midline behind the

sternal angle , then downward until the xiphisternal joint .

On the left pleura :

similar course , but at level of the 4th costal cartilage it deviates laterally and extends to

the lateral margin of the sternum to form the cardiac notch, then turns sharply downward

to the xiphisternal joint.

3. lower border of the pleura:

on both sides follows curved line, which crosses the 8th rib in the midclavicular line and

the 10th rib at the midaxillay line , and reaches the 12th rib adjacent to vertebral column .

Suprapleural membrane : (Sibson's fascia):

A dense fascia layer , attached to the inner border of the first rib and costal cartilage and

transverse process of the c7 vertebra.

medially it thin out and disappear into the mediastinal pleura.

Cervical dome of the pleura is attached to its under surface.

It gives rigidity to the thoracic inlet .

prevents the neck structures being puffed up and down during respiration.

Applied :

Damaging Suprapleural membrane during dissection in the neck may lead to

pneumothorax.

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Pleural recesses:

Pleural recesses:

The lower margin of the lung cross the 6th rib in midclavicular line , 8th rib in midaxillay

line and tenth rib at the sides of the vertebral column, as the pleura cross the same points

2 ribs below , the distance between two borders corresponds to the costodiaphragmatic

recess.

1. Costodiaphragmatic recesses :

Are slitlike spaces between the costal and diaphragmatic parietal pleura that are

separated by layer of pleural fluid , during inspiration the lower margin of the lung

descends into the recesses.

2. Costomediastinal recesses :

Situated along the anterior margin of the pleura, it is slitlike between the costal and

mediastinal parietal pleura , that are separate by a layer of pleural fluid and during the

inspiration and expiration the anterior border of the lungs slide in and out of the recesses.

Nerve supply of the pleura:

Parietal layer :

Sensitive to pain, pressure ,temperature, touch and, it supplied as follows.

1. Costal pleura: Segmentally supplied by the intercostal nerves.

2. Mediastinal pleura : Supplied by the Phrenic nerve

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3. Diaphragmatic pleura : Supplied over the domes by the Phrenic nerve, and around the

periphery by the lower six intercostal nerves

Visceral pleura : insensitive to common sensation, but receives an autonomic supply

from pulmonary plexus , its sensitive to stretch only.

Trachea :

Trachea:

A mobile cartilaginous and membranous tube of 10-13 cm long and 2.5 cm in diameter , it

has a series of U shaped bars of hyaline cartilage (15-20) embedded in its wall to keep it

patent .

Started below the cricoid cartilage of the larynx at the level of the body of the sixth

cervical vertebrae, 5 cm above the jugular notch , it enters the thoracic inlet in midline .

Ends in the thorax at the level of sternal angle (lower border of 4th thoracic vertebrae), by

dividing into right and left main bronchi, a little to the right of midline, at deep inspiration

the bifurcation may descends to the level of the sixth thoracic vertebrae.

Relation in the superior mediastinum:

Anteriorly.

manubrium, thymus, left brachiocephalic vein, brachiocephalic and left common carotid

arteries diverge on either side.

Posteriorly : Esophagus, left recurrent laryngeal nerve.

Laterally :

on right side:

Azygos vein, right vagus nerve.

On Left side:

Arch of aorta as it curves backwards over the left bronchus, left common carotid, left

subclavian arteries, left vagus, left Phrenic nerve, and the pleura.

Blood supply :

Branches from the inferior thyroid artery and bronchial arteries form rich anastomotic

networks in the tracheal wall.

Veins drain to the inferior thyroid plexus.

Nerve supply:

Branches of vagus, the recurrent laryngeal nerves and sympathetic trunks, they

distributed to the mucous membrane lining the trachea, and the muscles.

Relation in the superior mediastinum:

, thymus, left brachiocephalic vein, brachiocephalic and left common carotid

Esophagus, left recurrent laryngeal nerve.

a as it curves backwards over the left bronchus, left common carotid, left

subclavian arteries, left vagus, left Phrenic nerve, and the pleura.


Veins drain to the inferior thyroid plexus.


distributed to the mucous membrane lining the trachea, and the muscles.

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, thymus, left brachiocephalic vein, brachiocephalic and left common carotid

a as it curves backwards over the left bronchus, left common carotid, left



Principle Bronchi and lung root ( hilum)

The trachea divided at the level of sternal angle into the right and left main bronchi.

Principle Bronchi

1.The right :

About 2.5 cm long and it is wider, but shorter and more vertical than the left, and before

entering the hilum of the right lung , the right principle bronchus gives off the superior

lobar bronchus, and on entering the hilum it divides into a middle and an inferior lobar

bronchus.

2. Left main bronchus:

5 cm long , and its longer, but narrower and more hori

bronchus.

It passes to the left below the arch of the aorta and in front of esophagus.

On entering the hilum of the left lung it divides into a superior and inferior lobar

bronchus.

and lung root ( hilum):



lum of the right lung , the right principle bronchus gives off the superior


5 cm long , and its longer, but narrower and more horizontal than the right main

It passes to the left below the arch of the aorta and in front of esophagus.


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lum of the right lung , the right principle bronchus gives off the superior


zontal than the right main


Root of the lung ( Hilum):

made up of the bronchi, pulmonary artery, pulmonary veins, lymph vessels, bronchial

vessels, and nerves.

These structures are surrounded by a tubular sheath of pleura, which joins the

mediastinal parietal pleura to the visceral pleura covering the lungs.

In left the upper part is occupied by pulmonary artery and lying within the concavity of

the arch of aorta, below it is bronchus , and the two veins are laying one in front and one

behind the bronchus .

On right arrangement is similar except the upper lobe bro

so it lies superior .

Applied:

Inhaled Foreign bodies will go to right main bronchus more frequently than the left ,

because the right is wider and more vertical ( on line with trachea ) than the left one .

up of the bronchi, pulmonary artery, pulmonary veins, lymph vessels, bronchial


mediastinal parietal pleura to the visceral pleura covering the lungs.

eft the upper part is occupied by pulmonary artery and lying within the concavity of


On right arrangement is similar except the upper lobe bronchus originate outside the lung



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up of the bronchi, pulmonary artery, pulmonary veins, lymph vessels, bronchial


eft the upper part is occupied by pulmonary artery and lying within the concavity of


nchus originate outside the lung



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The Lungs:

Healthy lung are pink in colour, soft , spongy and elastic, it becomes dark and mottled due

to inhalation of dust particles.

Each lung is conical in shape and covered by visceral pleura, it is suspended free in its own

pleural cavity , being attached to the mediastinum only by its root. the right lung is slightly

larger than left one.

Each lung has :

1.Apex . Blunt and projects into the neck, 2.5 above the clavicle.

2. Base . Sits on diaphragm.

3. costal surface . Convex, which corresponds to the concave chest wall.

4. mediastinal surface : which moulded by the pericardium and other mediastinal

structures, which also contains the hilum at its middle .

5. Anterior border : Thin, and which contains the cardiac notch on left .

6. posterior border :

Thick and lies beside the vertebral column

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Lobes and fissures :

Right lung :

Divided by the oblique and horizontal fissures into three lobes, the upper , middle and

lower lobes.

Oblique fissure:

Indicated on the surface by a line drawn from the root of the spine of the scapula

obliquely downward , laterally and anteriorly, following the course of the sixth rib to the

sixth costochondral junction.

Horizontal fissure: Represented by a line drawn horizontally along the 4th costal cartilage

to meet the oblique fissure in midaxillay line.

Left lung :

it has only oblique fissure resulting in only two lobes upper and lower lobes.

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Relations of mediastinal surfaces of both left and right Lung

Medistinal surface of right lung related to :

1.Heart. 2.SVC and IVC. 3.Arch of azygos vein

4.Trachea . 5. Esophagus 6. First rib

7.Brachiocephalic vein.

Mediastinal surface of left lung related to :

1. Heart

2. .ascending and arch of aorta, descending thoracic aorta,

3. left first rib,

4. Trachea ,

5. esophagus,

6. left subclavian artery

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Bronchopulmonary Segments:

Bronchopulmonary Segments:

The anatomical, functional , and surgical units of the lungs.

Each lobar bronchus gives off branches called segmental bronchi.

A bronchopulmonary segment has the following characteristics.

1. It is subdivision of a lung lobe.

2. pyramidal in shape with its apex toward the lung root .

3. it has a segmental bronchus, a segmental artery, lymph vessels, and autonomic

nerves.

4. segmental vein lies in between the adjacent Bronchopulmonary segments.

5. Each segment can be removed surgically.

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Names of the main bronchopulmonary segments :

Right lung:

Superior lobe :Apical , anterior and posterior.

Middle lobe : medial, Lateral,

Inferior lobe : Superior( apical), medial basal, lateral basal, anterior basal, posterior basal.

Left lung :

Superior lobe : Apical, Anterior and Posterior.

Superior lingular, inferior lingular

Inferior lobe : Superior, medial basal, anterior basal, lateral basal, posterior basal

Blood supply of the lungs:

Bronchial arteries :

branches of the descending thoracic aorta, it supply the bronchi, connective tissue of

the lungs, visceral pleura.

Bronchial veins drain into the Azygos and hemiazygos, veins.

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Branches of Pulmonary artery:

Cary deoxygenated blood , and oxygenated blood leave the alveolar capillaries and drain

into the pulmonary vein, two from each lung drain the blood back to the left atrium.

Lymph Drainage of the lung:

Lymph drainage :

1. superficial ( subpleural ) plexus:

• Drains the surface of the lungs and pass toward the hilum where the lymph vessels

enter the bronchopulmonary nodes.

2. Deep plexus :

• Travel along bronchial and pulmonary vessels toward the hilum , then pass through

pulmonary nodes located within the lung substance , the lymph then enters the

bronchopulmonary nodes in the hilum

• All the lymph from the lung then drain into the tracheobronchial nodes and then

into the bronchomediastinal lymph trunks.

NERVE SUPPLY OF THE LUNG:

Nerve supply of the lungs:

Pulmonary plexus:

At the hilum formed from branches of sympathetic trunk and receives parasympathetic

fibres from the vagus nerve.

Afferent from the bronchial mucosa and stretch receptors in the alveolar walls pass to

CNS in both sympathetic and parasympathetic nerves.

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Mechanics of Respiration:

Mechanics of Respiration:

Respiration consists of two phases, inspiration and expiration , at rat of 14 -16 per minute.

It accomplished by alternate increase and decrease of the capacity of thoracic cavity by

the following mechanisms.

1. Contraction of diaphragm increase the vertical diameter of thoracic cavity.

2. Raising the ribs at their sternal end will increase the anteroposterior diameter ,and

transverse diameter , this is done by fixing the first rib by the contraction of the scaleni

muscles, and rising the ribs by the contraction of the intercostal muscles .

3. Relaxation abdominal muscles, help to accommodate the abdominal contents as the

diaphragm descend down.

It is contraction help in case of forced expiration.

In cases of forced inspiration all muscles which can rise the ribs are involved include

sternocleidomastoid , scalenus anterior and medius.

In cases of respiratory distress scapulae is fixed by trapezius, levator scapulae, and

rhomdoids muscles, so the serratus anterior and pectoralis minor can pull up the ribs to (

pectoralis major involved to in certain position).

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Types of respiration:

1.Abdominal:

As in children because the ribs are still horizontal , so the increase in the thoracic capacity

is depends mainly on contraction of the diaphragm.

2. Thoracic type :

in adult female tend to depend mainly on the movement of ribs ( male tend to use both

but mainly abdominal type .

PERICARDIUM

Fibrous pericardium

Parietal layer of serous pericardium

Visceral layer

P. cavity

Pericardium

Fibroserous sac that enclose the heart and roots of the great vessels.

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Location :

within the middle mediastinum, posterior to the body of the sternum.

Functions:

1.Protects and anchors the heart to the surrounding.

2.Provide lubricated container in which the heart can contract easily.

3 . To restrict excessive movement and over filling of the heart.

Structure :

Two layers fibrous and serous

1. Fibrous pericardium:

Strong part of the sac, attached

Below to the central tendon of the diaphragm.

Anteriorly to the sternum by the sternopericardial ligament.

fuse with the outer coat of the great blood vessels namely the aorta, pulmonary trunk,

superior and inferior vena cava, and the pulmonary veins.

2. Serous pericardium:

It has two layers, with slit like space in between ( pericardial cavity) which contains a small

amount of fluid the pericardial fluid which acts as lubricants.

1. Parietal layer:

lines the fibrous pericardium and reflected around the roots of the great vessels to

become continuous with

2. Visceral layer : ( epicardium) closely applied to the heart.

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Pericardial sinuses:

sinuses are formed due to the reflection of the serous pericardium around the roots of

great vessels, it lies between parietal and visceral layer.

1. Transverse pericardial sinus :

Passage above the heart results from the reflection of serous pericardium around the

ascending aorta and pulmonary trunk in front and the SVC , left atrium and pulmonary

veins behind .

1.Oblique sinus :

A recess on the posterior surface of the heart ,between the left atrium in front and the

fibrous pericardium behind.

Nerve supply of the pericardium:

Phrenic nerve:

supply Fibrous pericardium and Parietal layer of serous pericardium .

Visceral layer is insensitive to pain.

Blood supply of pericardium : Internal thoracic artery through the pericardiphrenic and

musculophrenic branches.

Bronchial arteries.

Thoracic aorta.

Veins : drain into azygos system

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HEART

Heart:

A hollow muscular organ lies within the pericardium in the mediastinum.

Pyramidal in shape .

Connected at its base to the great blood vessels.

Functions:

Acts as double pump with two functions its right side receives deoxygenated blood and

then pumps it to the lungs and the left side receives the oxygenated blood from the lungs

Position of the heart :

The heart lies obliquely in the thorax, with its long axis passing downward and to the left

to the apex.

The right-sided chambers are mainly anterior to the

left –sided counterparts due to heart rotation during development and pumps it to the

rest of the body.

Surface marks and borders of the heart

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Surface markings and borders of the heart : it has four borders and apex.

1. Superior border :

Formed by the roots of great vessels , and it extends from a point on the second left

costal cartilage 1.3 cm from the edge of the sternum to a point on the third right costal

cartilage 1.3 cm from the edge of the sternum.

2. Right border :

Formed by right atrium, and extends from a point on the third right costal cartilage 1.3 cm

from the edge of sternum downward to a point on the 6th costal cartilage 1.3 cm from the

edge of the sternum.

3. left border :Formed by left auricle and left ventricle , and extends from a point on the

second left costal cartilage 1.3 cm from the edge of sternum to the apex of the heart.

4. Inferior border :Formed by right ventricle, and the apical part of left ventricle , extends

from the 6th right costal cartilage 1.3 cm from the sternum to the apex beat.

Apex formed by left ventricle.

Apex is on left fifth intercostal space 9 cm from midline.

NB These borders are important when examining a radiograph of the heart.

Surfaces of the heart

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Has three surfaces

1.Anteri or (Sternocostal surface ):(

formed mainly by right ventricle with right atrium and narrow strips of left ventricle.

2. Posterior surface( Base ): formed mainly by the left atrium, into which the four

pulmonary veins opens.

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3. Inferior (Diaphragmatic surface) :

one third by right ventricle and two third by left ventricle separated by posterior

interventricular groove.

The apex of the heart :

formed by the left ventricle, it lies at the level of fifth left intercostal space 9cm from the

midline.

NB the heart does not rest on its base ,it rests on its diaphragmatic surface .

Structure of the heart wall :

Structure of heart : The heart wall is composed of a thick layer of cardiac muscle, the

myocardium, covered externally by epicardium ( visceral layer of serous pericardium) and

internally by endocardium

All three layers are richly supplied with blood vessels.

Divided into 4 chambers by septum, the atrial portion has thin walls and divided by

interatrial septum into right and left atrium.

The ventricular portion divided by, interventricular septum is placed oblique , with one

surface facing forward and to the right , and the other backward and to the left, its

positions, is indicated on the surface of the heart by anterior and posterior

interventricular groove, the lower part is thick and formed of muscles , the upper part is

thin and membranous and attached to the fibrous skeleton.

Chambers of the heart:

The heart is divided by vertical septa into four chambers, the right atrium which lies i

front of left atrium, and right ventricle in front of left ventricle .

Functionally, the atria are receiving chambers for blood returning to the heart from the

circulation

Because they need to contract only minimally to push blood into the ventricles, t

are relatively small, thin walled chambers

As a rule they contribute little to the propulsive pumping of the heart

RIGHT ATRIUM:

Right atrium :

Consists of a main smooth cavity and a small out pouching the auricle, which separated by

vertical groove the sulcus terminalis on out side and a ridge the crista terminalis on the

inside.


interatrial septum into right and left atrium.

ventricular portion divided by, interventricular septum is placed oblique , with one


positions, is indicated on the surface of the heart by anterior and posterior

entricular groove, the lower part is thick and formed of muscles , the upper part is

thin and membranous and attached to the fibrous skeleton.

The heart is divided by vertical septa into four chambers, the right atrium which lies i

front of left atrium, and right ventricle in front of left ventricle .


Because they need to contract only minimally to push blood into the ventricles, t

are relatively small, thin walled chambers

As a rule they contribute little to the propulsive pumping of the heart.



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ventricular portion divided by, interventricular septum is placed oblique , with one


entricular groove, the lower part is thick and formed of muscles , the upper part is

The heart is divided by vertical septa into four chambers, the right atrium which lies in


Because they need to contract only minimally to push blood into the ventricles, the atria



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The part of the atrium posterior the ridge is smooth and the part anterior is rough (

derived from primitive atrium).

Openings into the RA:

1.Superior vena cava : Opens into upper part of RA, it returns blood from upper half of

the body.

2. Inferior vena cava : Opens into lower part of the RA, it is guarded by a rudimentary

nonfunctioning valve, it return blood from lower half of the body.

3. Coronary sinus : Drains most of the blood from the heart, it opens into RA between

the IVC and right atrioventricular opening.

4. The right atrioventricular opening: Lies anterior to the IVC opening.

5. Openings of many other small veins.

Right ventricle :

Right ventricle: The walls is much thicker than the RA , and it has ridges formed of muscle

fibres ( trabeculae carneae).

Trabeculae carnaea types:

1. papillary muscles. Two large, anterior and posterior , and third smaller medial.

project inward , but attached to the wall at their bases and to fibrous chords ( chordae

tendineae) at their apices which are attached to the cusps of the tricuspid valve, third

smaller one

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2. Moderator band :Attached at both ends to the wall but free in the middle, so it cross

the ventricular cavity and it conveys the right branch the atrioventricular bundle of the

conducting system

3. simple prominent ridges .

Left atrium :

Similar to RA , it consists of a main cavity and left auricle.

It situated behind RA and forms the greater part of the base , behind it lies the oblique

sinus of the serous pericardium, fibrous pericardium separated it from the esophagus, it is

wall is smooth , but the auricle contains muscular ridges .

Openings:

1. four pulmonary veins. open through the posterior wall.

2. left atrioventricular orifice guarded by the mitral valve .

Left Ventricle :

Walls are three times thicker than that of right side, and in cross section it looks circular(

right is crescent ), it has two large papillary muscles anterior and posterior ,(but no

moderator band), the part just below the aortic orifice is called aortic vestibule.

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Heart valves

Tricuspid

Tricuspid valve:

Guards atrioventricular orifice , it consists of three cusps formed by a fold of endocardium,

and some connective tissue its base are attached to the fibrous ring of the skeleton of the

heart , the chordae tendineae connect the cusps to the papillary muscles, so that when

the interventricular pressure rises it prevent the cusps from being forced into the atrium

and turning the inside out.

The cusps are :

Anterior : lies anterior

Septal : lies on the interventricular septum.

Posterior = lies on inferior wall of the right ventricle.

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Pulmonary valve:

Pulmonary valve:

Guards the pulmonary orifice , and it consists of three semilunar cusps formed of

endocardium and some connective tissue.

The open mouths of the cusps are directed upward , and the margin and sides are

attached to the arterial wall.

There are no chordae or papillary muscles.

There are three dilatation( sinuses), each one is situated external to each cusps.

The cusps are one posterior and two anterior ( R and lt).

During diastole blood flow back enter the sinuses so the valve cusps fill and come into

apposition in the centre of the lumen and close the pulmonary orifice.

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Mitral valve:

Mitral valve :

Bicuspid , named anterior and posterior ,normally admits the tips of two finger, the cusps

are attached to the margin of the fibrous atriventricular ring.

The anterior cusp is thicker than the posterior one, and it lies between the mitral and

aortic orifices( between inflow and outflow).

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Aortic valve:

Aorticvalve

Aortic valve:

Guard the aortic orifice and is precisely similar in structure to pulmonary valve it has

three cusps right and left cusps situated on anterior wall, and posterior situated on the

posterior wall , behind each one is aortic sinus.

From anterior sinus rise the right coronary artery.

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Surface marking of heart Valves:

All the valves lie behind the sternum, making nearly vertical line.

Tricuspid valve:

• lies behind the lower part of sternum in the midline, opposite the 4th intercostal

space.

Mitral valve :

• lies behind the left half of the sternum opposite the 4th costal cartilage.

Aortic valve:

• lies behind the left half of the sternum opposite the 3rd intercostal space

Pulmonary valve :

• lies behind the medial end of the 3rd left costal cartilage and adjoining part of the

sternum.

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Applied :

The Areas of auscultation for heart valves are not corresponding to Surface marking of

heart valves .

Fibrous Skeleton of the heart:

The fibrous skeleton of the heart :

Consists of three fibrous rings that surround the atrioventricular , pulmonary and aortic

orifices and are continuous with the membranous upper part of interventricular septum.

The fibrous rings support the bases of the valve cusps and prevent the valves from

stretching and becoming incompetent.

Functions:

1. Anchors the valves of the cusps.

2. prevents over dilatation of the valve.

3. Blocks direct spread of electrical impulses from

Conducting system of the heart:


Function:

1. To generate rhythmical cardiac impulse.

2. conducting these impulses .

Structure of conducting system:

1. Sino-atrial node (SA) : The pacemaker, situated at the upper part of sulcus terminalis,

just to the right of scv opening, the cardiac impulse spread t

reach, the SA connect to AV node by rapid way called internodal pathway.



s support the bases of the valve cusps and prevent the valves from

stretching and becoming incompetent.

1. Anchors the valves of the cusps.

2. prevents over dilatation of the valve.

3. Blocks direct spread of electrical impulses from atria to ventricles .


Conducting system of the heart: Consists of specialized cardiac muscle.

o generate rhythmical cardiac impulse.

Structure of conducting system:

he pacemaker, situated at the upper part of sulcus terminalis,

just to the right of scv opening, the cardiac impulse spread through the atrial wall to

he SA connect to AV node by rapid way called internodal pathway.

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s support the bases of the valve cusps and prevent the valves from

he pacemaker, situated at the upper part of sulcus terminalis,

hrough the atrial wall to

he SA connect to AV node by rapid way called internodal pathway.

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2. Atrioventricular node: Situated at the lower part of the atrial septum, just above the

Septal attachment of tricuspid valve, from there the impulse reach the.

3. Atrioventricular bundle: Descends behind the Septal cusp of tricuspid valve. to reach

the inferior border of membranous part of ventricular septum, then at its upper muscular

part it divides into two branches, one for each ventricle.

4. Bundle branches:

Right bundle : passes on the right side of the septum to reach the moderator band, by

which crosses the ventricular lumen to reach the anterior wall of RV , and becomes

continuous with the purkinje plexus.

Left bundle : pierces the septum and passes down beneath the endocardium, then

divided into two branches( anterior and posterior) , to become continuous with the

5. purkinje plexus.

Nerve supply of the heart:

Sympathetic nerves travel to the heart from the cervical and upper thoracic chain ganglia

All nerves serving the heart pass through the cardiac plexus on the

entering the heart.

BLOOD Supply of the Heart

Arterial Blood supply of the heart:

Provided by the right and left coronary arteries.,

over the surface of the heart lying within subepicardial connective tissue.

Right coronary artery:

Arises from the anterior ( right) aortic sinus of ascending aorta , runs forward between

pulmonary trunk and the right auricle.

it descends vertically in the right atrioventricular groove, where it gives branches to right

atrium and right ventricle.

At the inferior border of the heart it continues posteriorly along the interventricular

groove to anastomose with left

It gives :

1. Marginal branch : To right ventricle


All nerves serving the heart pass through the cardiac plexus on the trachea before

BLOOD Supply of the Heart

Arterial Blood supply of the heart:

Provided by the right and left coronary arteries., they and their branches are distributed

over the surface of the heart lying within subepicardial connective tissue.


ght auricle.



groove to anastomose with left coronary artery.

1. Marginal branch : To right ventricle

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trachea before

they and their branches are distributed




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2. Posterior interventricular :supplies both ventricles, and anastomoses with anterior

interventricular branch of left coronary in the posterior interventricular groove.

The left coronary artery :

Usually larger than the right coronary artery, arises from the left posterior aortic sinus of

the ascending aorta and passes forward between the pulmonary trunk and the left

auricle.

Enters the atrioventricular groove and divided into an anterior interventricular branch

and circumflex branch.

1.Anterior interventricular : runs downward to the apex of the heart in the anterior

interventricular groove, passes around the apex to anastomose with the posterior

interventricular branch of right coronary artery. it supplies the right and left ventricles and

the ventricular septum.

2. Circumflex branch :

Follows the atrioventricular groove , winds around the left margin of the heart, and ends

by anastomosing with the right coronary artery . It supplies the left atrium and left

ventricle.

Variations:

The origin , size and distribution of the posterior interventricular artery are variable, and it

is a large branch of the right coronary in case of right dominance, in 90% of cases.

In the other 10% the posterior interventricular is a branch left coronary artery ( left

dominance).

NB: Although anastomoses between terminal branches of the coronary arteries do occur,

they are not large enough to provide an adequate supply of blood to cardiac muscles if the

main supply become blocked by disease.

Blood supply to the conducting system:

Right coronary : supplies the SA node ,AV node and atrioventricular bundle.

Left bundle branch supplied by right and left coronary.

Right bundle branch by left coronary .

Veins drainage of the heart:

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1. Coronary sinus: lies in the atrioventricular groove as a continuation of, open into the

right atrium to the left of inferior vena cava.

2. Great cardiac vein.

3. Small cardiac vein.

4. Middle cardiac vein.

5. Anterior cardiac veins: open directly to right atrium.

6. Right marginal vein.

7. Anterior interventricular vein.

Large arteries of the thorax

Aorta:

For purposes of description it divided into the ascending aorta, arch of the aorta ,

descending thoracic aorta, and abdominal aorta.

1. Ascending aorta:

lies within the fibrous pericardium, and enclosed with the pulmonary trunk in a sheath

of serous pericardium.

Begins at the base of the left ventricle and runs upward and forward to lie behind the

right half of the sternum at the level of sternal angle, where it becomes continuous with

the arch of the aorta.

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At its root it has three bulges, the sinuses of the aorta .

Branches : Right and left coronary arteries.

2. Arch of the aorta:

• lies behind the manubrium sterni and arches upward, backward and to the left in

front of the trachea, then it passes downward to the left of the trachea, and at the

level of sternal angle becomes continuous with the descending aorta.

Branches:

1.Brachiocephalic artery:

Arise from the convex surface of the arch, and passes upward and to the right of the

trachea and divided into the right subclavian and right common c

2. left common carotid artery:

Arise also from convex surface , it runs upward and

to the left of the trachea and enters the neck behind

the left sternoclavicular joint.

3. left subclavian artery:

It runs upward along the left side of the trachea and the esophagus to enter the root of

the neck, it arches above the apex of the left lung.

3. Descending thoracic aorta:

lies in the posterior mediastinum , begins as continuation of the arch of aorta on left side

of the lower border of 4th thoracic vertebra, and runs in the posterior mediastinum ,

inclining forward and medially to reach the anterior surface of the vertebral column , at

the level of 12th thoracic vertebra it passes behind the diaphragm in the midline and

becomes continuous with the abdominal aorta.

Branches:

1. posterior intercostal arteries: to the lower nine intercostal spaces on each sides .

2. subcostal arteries and runs on each side along the lower border of 12th ribs to enter the

abdominal wall.

3. pericardial artery.

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4. oesophageal artery.

5. bronchial artery .

Pulmonary trunk :

About 5 cm long, it leaves the upper part of right ventricle , and runs upward and

backward and to the left, and terminates in the concavity of the aortic arch by dividing

into right and left pulmonary arteries , it enclosed in the fibrous pericardium and a sheath

of serous pericardium.

Branches :

1. right pulmonary artery: runs to the right behind the ascending aorta and SVC, to enter

the root of right lung.

2. left pulmonary artery: runs to the left in front of descending aorta.

3. ligamentum arteriosum: fibrous band that connects the bifurcation of the pulmonary

trunk to the lower concave surface of the aortic arch , it is the remains of ductus

arteriosus.

Large veins of the thorax

1. Brachiocephalic veins:

Right brachiocephalic vein:

formed at the root of the neck by the union of the right subclavian and right internal

jugular veins

Left brachiocephalic vein:

formed by union of left subclavian and left internal jugular.

Both join behind the manubrium sterni and in front of large branches of the aortic arch to

form the superior vena cava.

2. Superior vena cava :

formed by union of two brachiocephalic veins , it passes downward to end in the right

atrium, the Azygos vein joins the posterior aspect of the SVC, just before it enters the

pericardium.

3.Azygos veins:

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Consist of the main azygos vein , inferior hemiazygos , and the superior hemiazygos veins.

• They drain blood from posterior part of intercostal spaces, the posterior abdominal

wall, the pericardium, the diaphragm , the bronchi and the esophagus.

Azygos vein:

formed by the union of the right ascending lumber vein and right subcostal vein, then it

ascend through the aortic opening in the diaphragm, on right side of the aorta to the level

of 5th thoracic vertebra, where it arches forward above the root of the right lung to end in

the posterior aspect of SVC.

Tributaries, 8 lower intercostal veins, right superior intercostal vein, the superior and

inferior hemiazygos veins and numerous mediastinal veins

Inferior hemiazygos vein :

Formed by union of the left ascending lumber vein and left subcostal vein, it ascends

through the left crus of diaphragm , and at level of T8 vertebra it turns to the right to joins

the azygos vein, it receives some lower left intercostal veins and mediastinal veins.

Superior hemiazygos vein: formed by union of 4th to eight intercostal veins , it joins the

azygos vein at the level of 7th thoracic vertebra.

Inferior vena cava :

• It pierces the central tendon of the diaphragm opposite to the eight thoracic

vertebra and immediately enters the lower part of the right atrium.

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Esophagus

• Esophagus

A tubular structure about 25 cm long , that is continuous above with laryngeal part of the

pharynx opposite the sixth cervical vertebra, it passes through the diaphragm at the level

of the tenth thoracic vertebra to join the stomach.

Relations:

In the neck:

• Posteriorly the vertebral column.

• Laterally, lobes of thyroid gland

• Anteriorly: trachea and recurrent laryngeal nerves

• In the thorax:

Esophagus passes downward and to the left through the superior and then the posterior

mediastinum, at the level of the sternal angle the aorta pushes the esophagus over the

midline.

Posteriorly : bodies of thoracic vertebra, thoracic duct, azygos vein, right posterior

intercostal arteries, and descending thoracic aorta at its lower end.

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Laterally:

Right side: mediastinal pleura , and terminal part of azygos vein.

Left side : left subclavian artery, aortic arch, thoracic duct, mediastinal pleura.

Anteriorly : trachea, left recurrent laryngeal nerve, left principle bronchus ( constrict it),

pericardium, ( separates it from RA)

Constrictions in the eso.

• 1. At its commencement . Narrowest part

• 2. where it is crossed by aortic arch.

• 3. where it is crossed by left principle bronchus.

• 4.where it passes through the opening in diaphragm.

Blood supply of the esophagus:

1. upper third: inferior thyroid artery

2.middle third: branches of descending thoracic aorta

3. lower third: branches of left gastric artery.

Venous drainage : upper third into inferior thyroid vein, middle third into the azygos

vein, and lower third into left gastric vein ( tributary is of portal ).

Lymph drainage of eso.

• 1. upper third into deep cervical lymph nodes

• 2. middle third into the superior and posterior mediastinal nodes.

• 3. lower third into nodes along the left gastric vessels and to celiac nodes.

Nerve supply of the eso.

• Parasympathetic both afferent and efferent via the vagi.

• Sympathetic . The lower part is surrounded by eso. nerve plexus

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Nerves of the Thorax

Vagus Nerve:

Right vagus: Descends in thorax posterolateral to the brachiocephalic artery, then lateral

to trachea and medial to azygos vein.

Passes behind the root of the right lung and assist in formation of pulmonary plexus.

After leaving the plexus it passes onto the posterior surface of the eso. and take part in

formation of eso. Plexus.

passes through the eso. Opening in the diaphragm to reach posterior surface of the

stomach.

Left vagus: Descends in the thorax between the left common carotid and left subclavian

artery, then crosses the left side of the arch of aorta, turns backward behind the root of

the left lung, assist in formation of the pulmonary plexus , Leave the plexus pass onto the

anterior surface of the esophagus, Take part in formation of oesophageal plexus.

Pass through the oesophageal opening in the diaphragm, to reach anterior surface of the

stomach.

Branches of vagus nerve:

Both supply the lungs, and esophagus.

Left gives the left recurrent laryngeal nerve as the main nerve cross the arch, it hooks

around the ligamentum arteriosum and ascends in groove between the trachea and the

esophagus , to supply the muscles acting on the left vocal cord except the cricothyroid (

tensor to the cord) which supplied by external laryngeal)

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PHRENIC NERVES:

Phrenic nerve :

from the anterior rami C3,4,5, supply the muscle of the diaphragm.

Sensory from the peritoneum covering the central region of the undersurface of the

diaphragm, pleura covering the upper surface, pericardium and mediastinal parietal

pleura.

The right phrenic nerve:

Descends in the thorax along the right side of the right brachiocephalic vein and the

superior vena cava.

Passes in front of the root of the right lung and runs a long the right side of the

pericardium, Then on the right side of IVC to diaphragm.

Its terminal branches passes through caval opening to supply the peritoneal side of the

diaphragm.

Left phrenic nerve:

Descend along the left side of the left subclavian artery.

Crosses the left side of aortic arch, and also crosses the left vagus nerve.

Passes in front of the root of the left lung.

Descends on the left side of the pericardium.

Terminal branches pierce it to supply the central peritoneal surface

•

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Thoracic part of sympathetic trunk

Thoracic part of sympathetic trunk:

Continuous above with the cervical part and below with the lumber parts.

Runs downward on the heads of the ribs as the most laterally placed structures in the

mediastinum.

Leaves the thorax on the side of the body of the 12th vertebra, by passing behind the

medial arcuate ligament.

Branches:

1. gray rami communicantes to all thoracic spinal nerves ( postganglionic distributed

through the spinal nerve to blood vessels, sweat glands, arrector pili muscles of the skin.

2. upper fife : postganglionic to heart, lung, aorta , esophagus .

3. Lower eight give preganglionic as splenic nerves.

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LYMPH DRANAGE OF THE THORAX and Thoracic duct

Thoracic wall :

anterior thoracic wall drain into the anterior axillary lymph nodes .

posterior thoracic wall drain into the posterior axillary lymph nodes .

Intercostal space : anterior part of drain into the internal thoracic nodes.( along the

internal thoracic blood vessels).

posterior part of intercostal space drain into the posterior intercostal nodes, lying near

the heads of the ribs.

Thoracic duct :

Commences at the upper end of cisterna chyli, on level with the body of T12 vertebra

between aorta and azygos vein, it passes up and comes to lie against the right side of

esophagus.

At T5V it inclines to the left and pass behind the esophagus, and it lies to the left of the

esophagus posterior to the aorta and the left subclavian vein in the superior mediastinum.

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As it ascends in the thorax it lies anterior to the right posterior intercostal arteries and

terminal part of hemiazygos vein.

Finally it passes vertically upward and arches forward across the dome of the left pleura

to enter the point of confluence of the left internal jugular and subclavian veins.

Thoracic duct has many valvesAll the above drain into the thoracic duct.

So it drain all the lymph from the body except that from the right arm, right half of the

thorax , right half of head and neck.

The End

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By

Dr Ahmed Mohammed Sulaiman, M.B.B.CH, Msc, DHE, PhD

Ass. Prof. of Anatomy and Embryology, A head of Anatomy Department

Faculty of Medicine, Tripoli University

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GOOOOOOOOOOOOOOOOOOOOOOOOOOOOD LUCK

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Documents

2sheath of thoracic anatomy for medical students