sheet no.30

Arterial Supply Of The Heart:


*Heart is supplied by 2 coronary arteries (right&left) that branch from 1st part of aorta(ascending aorta).

1-Right coronary artery:
-smaller in size
-mainly to the right side of the heart(right atrium&right ventricle)
Less functional-
passing through right side of coronary sulcus (between right atrium&right ventricle)-

2-Left coronary artery:

More functional -
Larger-
mainly to the left side of the heart(left atrium &left -ventricle)

-passing through left side of coronary sulcus(between left atrium and left ventricle)
commonly affected by diseases(eg:thrombus/constriction/embolus/aneurusm/empolus)-

(embolus is caused when an unvaccumed needle is being injected into the coronary artery letting air in &causing stop in the blood flow)

(aneurusm occurs when vessels on both sides are dilated instead of being cylinder
(tube like))

(catheterization/stem/bypass/ballooning…on the left as it is more functional than the right
(empolus is caused when there is extra air in the lung)

Note: both coronary arteies are freely connected (anastomosed:tube with tube) for compensation.

Venous Drainage Of Structures Of The Heart:

*occurs through coronary vein(coronary sinus) which is:

5 cm in length

-draining most structures of the heart by carrying venous blood from the left side to the right side within coronary sulcus(waste) to end into the right atrium (opens/empties there)
directed from left to right-

-located on the posterior side of the waste
Cardiac Conducting System:

*a specialized (modified) myocardial cells that initiates & coordinates atrial & ventricular muscle contraction

Note: muscles in general have 2 main functions:

1-conducting (receiving impulses)
2-contracting (responding to these impulses)
But the myocardial cells that form the cardiac conducting system are modified to only conduct (receive the nerve pulses)& no longer contract

*it is organized into 4 basic components:

1-SAN(Sino-Atrial Node):

-located at superior end of crista terminalis at terminal end of superior vena cava (or close to the opening of superior vena cava)(upper part of right atrium)
-it initiates the impulse (excitation signals) then spread it through the atrial wall to reach the
atrioventicular node (AVN)
it is called the pacemaker of the heart-
-it is autorhythmic as it initiates the impulses of the heart by itself (75 beats/min)
(if the SAN is defected in a way to give a heart beat lower than normal(75) which is not enough to perform any action we use an artificial pacemaker that is replaced in the pectoral region & its wire is descended down to the right ventricle through tricuspid valve &the clampes are replaced on the anterior papllary muscles in the right ventricles because the filling (from atrium to ventricle) there is passive [notice that we didn’t replace it on SAN as it isn’t working efficiently])
(if the heart stopped beating (autorhythm of SAN stopped) or the beat increased to more than
150 "ARHYTHMIA" we returned it to normal by CPR or by DC Shock where SAN stopped for 1,2,3 sec then returned back to its normal rhythm)
(SAN is balanced between sympathetic & parasympathetic nervous systems which are basically related to the habits of eating,place & style of living)

2-AVN(AtrioVenticular Node):

located at inferior end of the interatrial septum (lower part of right atrium)
receives(converge)the impulse from the atrial wall & conducts it to the right & left bundle branches via AV bundle


3-AV Bundle (AtrioVenticular Bundle):

muscular connection acts as a cable transmitting impulses from AVN to RT&LT bundle branches

4-Right & Left Bundle Branches:

Conduct the impulses to the myocardium of the heart especially the papllary muscles through Purkinje Fibers

*RT bundle branch: ends at RT papillary muscle that contracts before contraction of the wall closing the tricuspid valve &allows RT ventricle to contract (systole)

*LT bundle branch: ends at LT papillary muscle that contracts before contraction of the wall closing the bicuspid valve&allows LT ventricle to contract(systoles)

(both systoles occurs at the same time)

5-Purkinje Fibers:

-Its final fibers forms the subendocardial plexus that spreads throughout ventricles to supply ventricular muscles including the papillary muscles
-Note:the myocardial cells that forms the cardiac conduction system are insulated from myocardium by connective tissue& they establish a unidirectional pathway of excitation & contraction.


Mediastinum:

*central portion of the thorax between 2 pleural sac compartments
*located behind sternum / anterior to all thoracic vertebrae
*extend from thoracic inlet to the thoracic outlet
*divided into 2 main parts(superior & inferior)by an imaginary line extending from sternal angle to the intervertebral disk between t4 & t5
*each part has its own boundaries & contents
1-Superior Mediastinum:
Boundaries:Ant:manubrium sterni
Post:4 upper thoracic vertebrae
Sup: thoracic inlet
Inf: imaginary line between sternal angle & IVD between T4&T5
Contents: 1-midline structures(from post to ant):
vertebral column(skeletal)
esophagus(digestive)
trachea(respiratory)
aorta(circular)
thoracic duct
2-bilateral:
2 vagus nerves &2 phrenic nerves
(fraction of T3 will cause bulging on esophagus then trachea then aorta)
2-Inferior Mediastinum:
due to the presence of the heart which is surrounded by the pericardium it is divided into :
a-Anterior mediastinum:
Boundaries:Ant:body of sternum-
Post:anterior wall of pericardium
Sup:imaginary line between sternal angle and IVD of t4-t5
Inf:diaphragm(superior part anterior surface)
Contents:thymus gland-
(thymus gland is large in infants, newborn& children then by growing it starts to shrink(involution)& it is for immunity)
(sometimes you cant listen to the heart well(the sound is ambiguous to you)& by x-ray(lateral view) you find that the heart is shifted back due to the enlargement in thymus gland which is known as "thymomia"-"thymus cancer")
b-Middle mediastinum:
-Boundaries:Ant:anterior mediastinum
Post:posterior mediastinum
Sup:imaginary line
Inf:central tendon of diaphragm
-Contents:pericardium & its contents(heart & root of large vessels)
c-Posterior mediastinum
Pericardium:(resembles pleura of the lungs)
-it is a pyramidal-shaped sac (double-walled fibroseruos conical-shaped sac)
-has a base (inferior) attached to central tendon of diaphragm & apex (superior) attached to roots of large vessels(SVC/aortic arch /pulmonary trunk)
-divided into 2 layers:
1-Parietal layer (outside)
2-Visceral layer (inner): surrounds the heart itself
-there is a space between these 2 layers called "Pericardial Cavity" which is a potential space that contains a thin film of fluid that enables frictionless heart beats
(heart & pericardium forms a pyramid inside a pyramid in converted direction(apex of heart is ant to the lt &apex of pericardium is sup /base of heart is post &base of pericardium is inf)
**********************************************
انا حملنا الحزن أعواما و ما طلع الصباح
والحزن نار تخمد الأيام شهوتها وتوقظها الرياح
والريح عندك كيف تلجمها وما لك من سلاح
الا لقاء الريح والنيران في وطن مباح...
(محمود درويش/الحزن والغضب)
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" ليس المهم أن تحقق فكرتك قبل أن تموت...
المهم أن تجد لنفسك فكرة قبل أن تموت..." غسان كنفاني

eI'd like to thank all my friends at ittihad & med school esp.:

Rasha Jabra, Wala Abushanab, Ala 3bd r2of,Aseel 7oso, Eman Remawi,R2a Samee7,Bayan 5dor,Sherin Alm3ali,Ruba M7taseb,Lama Jamal,Amal 7lo,Sndus 56eb,Ala 7jazi,Nisren Abu39be,Aya Bnyknana,Samar Alr7ma,D3a Abugame3,D3a jara7,Dania Dhmsh,W3d Swelmen,Zein Najada,Rawan Marwan,Samar 68a68a,Muna 6alal,Aseel Abushanab,Elham 8dah,Ala Jabri,Ala 7lesi,Rawan Sale7,D3a Tawfe8,Najd 8r3an , Aseel Sayed,Dima 3bdkreem,Nadia,Heba Mazen,Tala,Shahed 3amer,Rawan Mansour, Esra 3efan,Nouf Abuzeme3,Lara Dndn,Rana Njm,Dina Ba6ayna,Dana Ma6a7en,Shaden Sarayra,Muna N3emi,Yasmen 3bd3zez, ,Lina Taim,Laila D3as,Nansy 7yari,Dima 8nd7,Razan Magali, …


BEST WISHES TO U ALL……………………
*Rawan Ghazal*
Correction for sheet 29-page 4:
-the inflow part of the left ventricle is rough containing same >>>