Cardiovascular System 2014 (Yuni)

8/12/2019 Cardiovascular System 2014 (Yuni)

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Mediastinum occupied by the mass of tissue between the two pulmonarycavities, is the central compartment of the thoracic cavity

Contains all thoracic viscera except the lungs


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The mediastinum extends : from the superior thoracic aperture to the diaphragm inferiorlyfrom the sternum and costal cartilages anteriorly to the bodies of the thoracicvertebrae posteriorly.


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The superior thoracicaperture is bounded :

Posteriorly, by vertebraT1

Laterally, by the 1st pairof ribs and their costalcartilages.

Anteriorly, by thesuperior border of themanubrium


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Unlike the rigid structure observed in the embalmed

cadaver, the mediastinum in living people is a highlymobile region because it consists primarily of hollowvisceral structures united only by loose connectivetissue, often infiltrated with fat.

The major structures in the mediastinum are also

surrounded by blood and lymphatic vessels, lymphnodes, nerves, and fat


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The mediastinum is divided into :

Extends inferiorlyfrom the superiorthoracic aperture tothe horizontal planeOften referred to asthe transversethoracic plane thatincludes the sternalangle anteriorly andpassesapproximatelythrough the

junction (IV disc) of

T4 and T5 vertebraeposteriorly

Superiormediastinum


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Thymus.Great vessels,

brachiocephalic veins andSVC arch aorta and roots of its

major branches thebrachiocephalic trunk, leftcommon carotid artery, andleft subclavian artery Related nerves (vagus andphrenic nerves and the

cardiac plexus of nerves).Trachea anteriorly andesophagus posteriorly andrelated nerves (left recurrentlaryngeal nerve).Thoracic duct and lymphatic

trunks.

From anterior to posterior, the contents of the superiormediastinum are :


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Between the transversethoracic plane and thediaphragm

Is further subdivided by thepericardium into anterior,middle, and posterior parts.

The pericardium and its

contents (heart and roots ofits great vessels) constitutethe middle mediastinum.

Inferiormediastinum


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Lies between : the body of the sternum andthe transversus thoracismuscles anteriorlythe pericardium posteriorly.Inferiorly by the diaphragm.

`The anterior mediastinumconsists of loose connectivetissue, fat, lymphatic vessels, afew lymph nodes, and branches

of the internal thoracic vessels..


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The pericardium and itscontents (heart and roots ofits great vessels ascending aorta, pulmonarytrunk, and SVC passing toand from the heart.)constitute the middlemediastinum


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Is located :inferior to the transversethoracic plane,anterior to the T5-T12vertebraeposterior to the

pericardium anddiaphragmbetween the parietalpleura of the two lungs


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The pericardium is afibroserous

membrane thatcovers the heart andthe beginning of itsgreat vessels

The pericardium is aclosed saccomposed of twolayers :1. Fibrous

pericardium2. Serous

pericardium Parietal layer Visceral layer


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Continuous superiorly with the tunica adventitia ofthe great vessels entering and leaving the heart andwith the pretracheal layer of deep cervical fascia.

Attached anteriorly to the posterior surface of the

sternum by the sternopericardial ligaments, whichare highly variable in their development.

Bound posteriorly by loose connective tissue tostructures in the posterior mediastinum.

Continous inferiorly with the central tendon of thediaphragm


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The serous pericardium is composedmainly of mesothelium, a single layer offlattened cells forming an epithelium thatlines both the internal surface of thefibrous pericardium and the externalsurface of the heart.

The internal surface of the fibrouspericardium is lined with a glisteningserous membrane, the parietal layer ofserous pericardium.

Parietal layer of serous pericardium isreflected onto the heart at the greatvessels (aorta, pulmonary trunk andveins, and superior and inferior venaecavae) as the visceral layer of serouspericardium.


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The pericardial cavity isthe potential spacebetween opposing layersof the parietal and viscerallayers of serouspericardium.

It normally contains a thinfilm of fluid that enables theheart to move and beat in africtionless environment


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It is about 12 cm long, 9 cm wide at its broadest point, and 6 cm thick, withan average mass of 250 g in adult females and 300 g in adult males

About two-thirds of the mass of the heart lies to the left of the bodys midline


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The heart : slightly larger than a clenched fist,is a double,self-adjusting suction and pressure

pumpthe parts of which work in unisonto propel blood to all parts of thebody

The right side of the heart (right

heart) receives poorly oxygenated(venous) blood from the bodythrough the SVC and IVC andpumps it through the pulmonarytrunk and arteries to the lungs foroxygenation.

The left side of the heart (leftheart) receives well-oxygenated(arterial) blood from the lungsthrough the pulmonary veins andpumps it into the aorta fordistribution to the body.


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Apex

Base

Surface

Border


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The pointed apex isformed by the tip ofthe left ventricle andrests on thediaphragm.

It is directedanteriorly, inferiorly,and to the left

Lies posterior to theleft 5th intercostalspace in adults


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Is the heart'sposterior aspect

Is formed mainlyby the left atrium,with a lessercontribution by theright atrium.

Extends superiorlyto the bifurcation ofthe pulmonarytrunk and inferiorlyto the coronarysulcus


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1. Diaphragmatic (inferior) surface ,formed mainly by the leftventricle and partly by the rightventricle; it is related mainly tothe central tendon of thediaphragm.

2. Left pulmonary surface ,formed mainly by the leftventricle; it forms the cardiacimpression in the left lung.


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3. Anterior

(sternocostal)surface , formedmainly by theright ventricle.

4. . Right pulmonarysurface ,formed mainly bythe right atrium.


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1. Right border , formed bythe right atrium andextending between theSVC and the IVC.

2. Inferior border , formedmainly by the rightventricle and slightly by theleft ventricle.

3. Left border , formed mainlyby the left ventricle and

slightly by the left auricle.

4. Superior border , formed bythe right and left atria andauricles in an anterior view


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The heart has four chambers: right and left atria and right and left ventricles

Valves of the heart :A. Atrioventricular valves

- Tricuspid valve- Bicuspid valve

B. Semilunar valves- Aortic valve- Pulmonary valve


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RIGHT ATRIUM :

Pectinate muscle

Right auricle Opening Inferior vena cava Opening superior vena cava Opening coronary sinus Ovale fossa Tricuspid valve Interatrial septum

LEFT ATRIUM :

Pectinate muscle

Left auricle Opening 4 pulmonary vein

(2 superior and 2 inferior) Bicuspid valve Interatrial septum A slightly thicker wall than that of theright atrium


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RIGHT VENTRICLE :

Trabecula carnae

AV Tricuspid valve Chorda tendinae Papillary muscle Semilunar pulmonary valve Interventricular septum

LEFT VENTRICLE :

Trabecula carnae

AV Bicuspid valve Chorda tendinae Papillary muscle Semilunar aortic valve Interventricular septum Walls that are two tothree times as thick as those of the right

ventricle


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a

Right atrium ?? Left atrium??

Right ventricle?? Left ventricle??


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Endocardium , a thin internallayer (endothelium andsubendothelial connectivetissue) or lining membrane of theheart that also covers its valves.

Myocardium , a thick, helicalmiddle layer composed ofcardiac muscle.

Epicardium , a thin externallayer (mesothelium) formed bythe visceral layer of serouspericardium


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Keeps the orifices of the AV and semilunar valves patent and prevents them frombeing overly distended by an increased volume of blood pumping through them.

Provides attachments for the leaflet & cusps of the valves

Provides attachment for the myocardium

Forms an electrical insulator, by separating the myenterically conducted impulsesof the atria and ventricles


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Tricuspid valves Bicuspid valves

Atrioventricularvalves

Aortic valves Pulmonary valves

SemilunarValves


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Operation of the atrioventricular valves

When the ventricles are relaxed the papillary muscles are relaxed, thechordae tendineae are slack, and blood moves from a higher pressure in the

atria to a lower pressure in the ventricles through open AV valves


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Operation of the atrioventricular valves

When the ventricles contract, the pressure of the blood drives the cusps upwarduntil their edges meet and close the opening At the same time, the papillary

muscles contract, which pulls on and tightens the chordae tendineae.This prevents the valve cusps from everting (opening into the atria) in responseto the high ventricular pressure.


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Operation of the semilunar valves

When the ventricles contract, pressure builds up within the chambers. Thesemilunar valves open when pressure in the ventricles exceeds the pressure in

the arteries, permitting ejection of blood from the ventricles into the pulmonarytrunk and aorta


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Operation of the semilunar valves

As the ventricles relax, blood starts to flow back toward the heart. Thisbackflowing blood fills the valve cusps, which causes the semilunar valves to

close tightly


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1 Systemic circulation

2 Pulmonary circulation

3 Coronary circulation


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Right coronary arteryLeft coronary arery

anteriorinterventricular

circumflexbranches

suppliesoxygenatedblood to thewalls of bothventricles To the walls of the

left ventricle andleft atrium.

supplies small branches (atrialbranches) to the right atrium

posteriorinterventricular

marginal branches

To walls ofthe twoventricles

to themyocardium of

the right ventricle


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blood passes through the arteries of the coronary circulation,

flows into capillaries

delivers oxygen and nutrients to the heart muscle and collects carbon dioxide andwaste

moves into coronary veins

coronarysinus

Great cardiacvein

Middle cardiacvein

Small cardiacvein

Anteriorcardiacveins


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While the heart is contracting, little bloodflows in the coronary arteries because they are squeezedshut.

When the heart relaxes, however, the high pressure ofblood in the aorta propels blood through the coronary

arteries, into capillaries, and then into coronary veins


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Cardiovascular System 2014 (Yuni)

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