Transcript Pericardium & Heart Thorax Unit Lecture 5 & 6 حيدر جليل األعسم . د

Pericardium & Heart
Thorax Unit
Lecture 5 & 6
‫ حيدر جليل األعسم‬.‫د‬
Pericardium
It is a fibroserous sac enclosing
heart and roots of great vessels.
Pericardium lies within middle
mediastinum, posterior to body of
sternum and 2nd - 6th costal
cartilages and anterior to 5th - 8th
thoracic vertebrae.
It is composed of two layers
A. Fibrous Pericardium
B. Serous Pericardium
Pericardium
Fibrous Pericardium
Fibrous pericardium is strong
fibrous part of the sac. It is
firmly attached below to central
tendon of the diaphragm. It
fuses with outer coats of great
blood vessels passing through it
(aorta, pulmonary trunk,
superior and inferior venae
cavae, and pulmonary veins).
Fibrous pericardium is attached
in front to sternum by
sternopericardial ligaments.
Pericardium
Serous Pericardium
It lines fibrous pericardium and coats heart. It is divided into
parietal & visceral layers. Parietal layer lines fibrous
pericardium & is reflected around roots of great vessels to
become continuous with visceral layer of serous pericardium
that closely covers heart.
Visceral layer is called
epicardium.
Pericardial cavity
is a slit-like space between
parietal & visceral layers that
contains a small amount of
tissue fluid, pericardial fluid
To facilitate heart movements
Pericardium
Pericardial Sinuses
They are recesses in pericardium cavity formed by reflection
of serous pericardium on posterior surface of heart.
Oblique sinus formed around large veins.
Transverse sinus lies between
reflection of serous
pericardium around
aorta and pulmonary
trunk and reflection
around large veins.
Pericardium
Nerve Supply of Pericardium
Fibrous pericardium and parietal layer of serous pericardium
are supplied by phrenic nerves. Visceral layer of the serous
pericardium is innervated by
branches of sympathetic
trunks and vagus nerves.
Heart
hollow muscular & pyramid shaped organ that lies freely within
pericardium in mediastinum and is connected at its base to great blood
vessels.
Heart has apex and 3 surfaces
Apex of heart: is formed by left ventricle, is directed downward,
forward, and to the left. It lies at level of 5th left intercostal space, 9 cm
from midline where apex beat can usually palpated in living patient.
Surfaces of the Heart:
Anterior, Inferior, Posterior
Heart Surfaces
Sternocostal (Anterior) surface: is formed mainly by right atrium and
right ventricle, which are separated from each other by vertical
atrioventricular groove. Right border is formed by right atrium; left
border, by left ventricle and part of left auricle. Right & left ventricles
are separated by anterior interventricular groove.
Heart Surfaces
Diaphragmatic (inferior) surface: is formed mainly by right and left
ventricles separated by posterior interventricular groove. Inferior
surface of right atrium and inferior vena cava also forms part of this
surface.
Heart Surfaces
Base of heart, or (posterior surface): is formed mainly by left atrium,
into which open four pulmonary veins. The base of heart lies opposite
apex.
Heart
Borders of the Heart
Right border is formed by right atrium;
left border by left auricle; and below, by left ventricle.
Lower border mainly by right ventricle but also by right atrium;
apex is formed by left ventricle.
Chambers of the Heart
Heart is divided by vertical septa into four chambers: right & left atria
and right & left ventricles. Right atrium lies anterior to left atrium, and
right ventricle lies anterior to left ventricle.
Walls of the heart are composed of cardiac muscle, myocardium;
covered externally with serous pericardium, epicardium;
and lined internally with a layer of endothelium, endocardium.
Chambers of the Heart
Right Atrium
It consists of a main cavity and a small out-pouching, auricle. There is a
vertical groove on outside of the heart at junction between right atrium
and right auricle called sulcus terminalis, which on the inside forms a
ridge called crista terminalis. Main part of atrium that lies posterior to
this ridge is smooth walled and is derived embryologically from sinus
venosus. Part of atrium in front of this
ridge is roughened or trabeculated by
bundles of muscle fibers, musculi
pectinati, which run from crista
terminalis to auricle. This
anterior part is derived
embryologically from primitive
atrium.
Chambers of the Heart
Openings into the Right Atrium:
Superior vena cava opens into upper part of right atrium; it has no
valve. It returns blood to heart from upper half of body.
Inferior vena cava opens into lower part of right atrium; it is guarded by
a rudimentary, nonfunctioning valve. It returns blood to heart from
lower half of the body.
Coronary sinus, which drains most
of blood from the heart wall, opens
into right atrium between inferior
vena cava and atrioventricular
orifice. It is guarded by a rudimentary,
nonfunctioning valve.
Right Atrioventricular Orifice lies
anterior to inferior vena cava
opening and is guarded by
tricuspid valve.
Chambers of the Heart
Fetal Remnants of right atrium:
Rudimentary valve of inferior vena cava
Fossa ovalis & Anulus ovalis: lie on atrial septum. Fossa ovalis is a
shallow depression, which is site of foramen ovale in fetus. Anulus
ovalis forms upper margin of fossa.
Floor of the fossa represents
persistent septum primum of
heart of embryo, and anulus is
formed from lower edge of
septum secundum.
Chambers of the Heart
Right Ventricle
It communicates with right atrium through atrioventricular orifice and
with pulmonary trunk through pulmonary orifice. Its cavity becomes
funnel shaped near pulmonary orifice called (infundibulum). Walls of
right ventricle are much thicker than
those of right atrium and show several
internal projecting ridges
formed of muscle bundles
trabeculae carneae. One type of
these trabeculae carneae are
Papillary muscles: which
project inward, being attached
by their bases to ventricular
wall; their apices are connected
by fibrous chords
(chordae tendineae)
to cusps of tricuspid valve.
Chambers of the Heart
Tricuspid valve guards atrioventricular orifice and consists of
3 cusps formed by a fold of endocardium with some
connective tissue enclosed:
Anterior, Septal & Inferior (posterior) cusps. Bases of cusps
are attached to fibrous ring of
heart skeleton, whereas their
free edges & ventricular
surfaces are attached to
chordae tendineae. When
ventricle contracts,
papillary muscles contract
and prevent cusps from
being forced into
atrium and turning inside
out as intraventricular
pressure rises. Chordae
tendineae of one papillary
muscle are connected to
adjacent parts of two cusps.
Chambers of the Heart
Pulmonary valve guards pulmonary orifice and consists of 3 semilunar
cusps formed by folds of endocardium with some connective tissue
enclosed. Open mouths of cusps are directed upward into pulmonary
trunk. No chordae or papillary muscles are associated with these cusps;
attachments of sides of cusps to arterial
wall prevent cusps from prolapsing into
ventricle. At root of pulmonary
trunk are 3 dilatations (sinuses)
each one is situated external
to each cusp.
Chambers of the Heart
Left Atrium
It consists of a main cavity and a left auricle. Left atrium is
situated behind right atrium and forms greater part of base
(posterior surface) of heart. Behind it lies oblique sinus of
serous pericardium, and fibrous pericardium separates it from
esophagus. Interior of left atrium is smooth,
but left auricle possesses muscular ridges.
Openings into the Left Atrium:
Four pulmonary veins: two from
each lung, open through posterior
wall with no valves
Left Atrioventricular Orifice: is
guarded by mitral valve.
Chambers of the Heart
Left Ventricle
It communicates with left atrium through atrioventricular orifice and
with aorta through aortic orifice. Walls of left ventricle are three times
thicker than those of right ventricle. In cross section, left ventricle is
circular; right is crescentic because of bulging of
ventricular septum into cavity of right ventricle.
There are well-developed trabeculae
carneae, two large papillary muscles.
Part of ventricle below aortic
orifice is called aortic vestibule.
.
Chambers of the Heart
Mitral valve guards atrioventricular orifice. It consists of two cusps, one
anterior and one posterior, which have a structure similar to that of
tricuspid valve. Anterior cusp is the larger and intervenes between
atrioventricular and aortic orifices.
Aortic valve guards aortic orifice and is similar to pulmonary valve.
Behind each cusp aortic wall bulges to form an
aortic sinus. Anterior aortic sinus gives origin
to right coronary artery, and left posterior
sinus gives origin to left coronary artery
Structure of the Heart
Walls of the heart: are composed of thick layer of cardiac
muscle, myocardium, covered externally by epicardium and
lined internally by endocardium. Atria are thin-walled and
divided by atrial (interatrial) septum into right and left atria.
Ventricles are thick-walled and divided by ventricular
(interventricular) septum
into right and left ventricles.
Septum is placed obliquely,
with one surface facing
forward and to the right
and the other facing
backward and to the left.
Lower part of septum is
thick and formed of muscle
and smaller upper
part of septum is thin
& membranous and
attached to fibrous
skeleton.
Structure of the Heart
Skeleton of the heart: consists of fibrous rings that surround
atrioventricular, pulmonary, and aortic orifices and are continuous with
membranous upper part of ventricular septum. Fibrous rings around
atrioventricular orifices separate muscular walls of atria from those of
ventricles but provide attachment for muscle fibers. Fibrous rings
support bases of valve cusps and prevent valves from stretching and
becoming incompetent. Skeleton of heart forms basis of electrical
discontinuity between atria and ventricles.
Structure of the Heart
Conducting System of the Heart:
Sinuatrial Node: is located in wall of right atrium in upper part of sulcus
terminalis just to right of opening of superior vena cava.
Atrioventricular Node: is strategically placed on lower part of atrial
septum just above attachment of septal cusp of tricuspid valve.
Atrioventricular Bundle of His: It
descends through fibrous skeleton
of heart behind septal cusp of
tricuspid valve to reach upper
border of muscular part of
septum, then divides into two
branches, one for each ventricle.
A. Right bundle branch (RBB)
B. Left bundle branch (LBB)
Subendocardial plexus
of Purkinje fibers:
Arterial Supply of Heart
It is provided by right and left coronary arteries, which arise from
ascending aorta immediately above aortic valve. Coronary arteries and
their major branches are distributed over surface of heart, lying within
subepicardial connective tissue.
Right coronary artery arises from anterior
aortic sinus of ascending aorta & runs
forward between pulmonary trunk &
right auricle. It descends almost
vertically in right atrioventricular
groove, and at inferior border of
heart it continues posteriorly along
atrioventricular groove to
anastomose with left coronary
artery in posterior interventricular
groove. It supplies right atrium and
right ventricle and parts of left
atrium and left ventricle and
atrioventricular septum.
Branches of right coronary artery:
1. Right conus artery: supply pulmonary conus
2. Atrial branches supply anterior and lateral surfaces of right atrium.
One branch supplies posterior surface of both right and left atria.
Artery of sinuatrial node supplies node and right and left atria; in
35% of individuals it arises from left coronary artery.
3. Ventricular Branches:
Anterior ventricular branches: supply anterior surface of right ventricle.
Marginal branch: is the largest & runs
along lower margin of costal surface
to reach apex.
Posterior ventricular branches:
supply diaphragmatic surface
of right ventricle.
Posterior interventricular
(descending) artery: runs in
posterior interventricular
groove. It supply inferior wall &
posterior part of ventricular septum.
Large septal branch supplies
AV node.
Arterial Supply of Heart
Left coronary artery supplies major part of heart, including greater part
of left atrium, left ventricle, and ventricular septum. It arises from left
posterior aortic sinus of ascending aorta and passes forward between
pulmonary trunk and left auricle. It then enters atrioventricular groove
& divides into an anterior interventricular branch & circumflex branch.
Anterior interventricular (descending) branch: runs downward in
anterior interventricular groove. In most
individuals it passes around apex of heart
to enter posterior interventricular
groove & anastomoses with
terminal branches of right coronary
artery. It supplies right & left
ventricles with numerous branches
that also supply anterior part of
ventricular septum. One of these
ventricular branches (left diagonal
artery) may arise directly from trunk
of left coronary artery. A small left
conus artery supplies pulmonary conus.
Arterial Supply of Heart
Circumflex artery: same size as anterior interventricular artery. It winds
around left margin of heart in atrioventricular groove.
Left marginal artery is a large branch supplying left margin of left
ventricle down to apex.
Anterior & posterior ventricular branches supply left ventricle.
Atrial branches supply left atrium.
Coronary Artery Anastomoses
between terminal
branches of right & left coronary
arteries exist, but not large to
provide an adequate blood
supply to cardiac muscle if one
of large branches becomes
blocked. A sudden block of one
of larger branches of either
coronary artery usually leads
to myocardial infarction, although
sometimes collateral circulation is
enough to sustain muscle.
Arterial Supply of Heart
Variations in the Coronary Arteries
Variations in blood supply to heart do occur, and most common
variations affect blood supply to diaphragmatic surface of both
ventricles. Here origin, size, and distribution of posterior interventricular
artery are variable.
In right dominance, posterior
interventricular artery is a large branch
of right coronary artery. Right
dominance is present in
most individuals (90%).
In left dominance, posterior
interventricular artery is a
branch of circumflex branch
of left coronary artery (10%).
Venous Drainage of the Heart
Most blood from heart wall drains into right atrium through coronary
sinus, which lies in posterior part of atrioventricular groove and is a
continuation of great cardiac vein. It opens into right atrium to left of
inferior vena cava. Small and middle cardiac veins are tributaries of
coronary sinus.
Remainder of blood is returned to right
atrium by anterior cardiac vein and by
small veins that open directly into
heart chambers.
Nerve Supply of Heart
Heart is innervated by sympathetic and parasympathetic fibers of
autonomic nervous system via cardiac plexuses situated below arch of
aorta. Sympathetic supply arises from cervical & upper thoracic portions
of sympathetic trunks, and parasympathetic supply comes from vagus
nerves.
Sympathetic fibers terminate on SA & AV nodes, cardiac muscle fibers &
coronary arteries. These nerves results in
cardiac acceleration, increased contraction
of cardiac muscle, and dilatation of
coronary arteries.
Parasympathetic fibers terminate on
SA & AV nodes and on coronary
arteries. These fibers results
in a reduction in rate and force of
contraction of heart and a
constriction of coronary arteries.
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