HEART

1. General

The heart is the central organ of the vascular system. It is a muscle hollowed out of cavities, atria and ventricles, doubled with an endocardium.

The entire myocardium is surrounded by an envelope, the pericardium, consisting of several sheets, delimiting a pericardial cavity. The heart is a muscle with an automaticity ensured by the nodal tissue. This automatism, which ensures operating autonomy, is regulated by the nerves of the heart which play on this automatism, either to increase or to decrease the heart rate, increased by physical exertion, stress, fever.

The heart is divided into four chambers, two systems: the right system and the left, each with an atrium and a ventricle.

Venous blood returns from the body through two veins: the cava veins: VCI, VCS. Blood enters the right atrium, then it passes into the right ventricle through the right atrioventricular opening. From there, it reaches the lungs via the pulmonary arteries, called the pulmonary trunk. At the level of the lung, the blood is purified, enriched in O2, and it leaves by two pulmonary veins, two by lung, and returns in the heart, at the level of the left auricle, the left atrium. Then, the blood passes into the left ventricle from where it will exit via the aorta which, in its initial part, draws a butt. From the horizontal portion will be born the three supra-aortic trunks:

a) brachiocephalic arterial trunk which divides in the upper part of the thorax into two arteries, the right primary carotid artery which rises vertically, and the right subclavian artery which changes direction, becomes horizontal and gives collaterals.

b) the left primary carotid artery, which rises vertically and is located on the left flank of the visceral axis of the neck

c) the left subclavian artery symmetrical to the right.

From the very initial part of the aorta, the aortic bulb, are born the coronary arteries.

The thickness of the myocardium is greater on the left than on the right.

The heart is placed in the thoracic cavity bounded by a wall: the thoracic grill and below by a muscle, the diaphragm.

The heart is a median organ. It is located at the bottom of the thoracic cavity, it extends far beyond the left. On either side will be the pleuropulmonary regions.

The heart is located in the lower mediastinum. The upper mediastinum contains large vessels such as the aorta, supra-aortic trunks, pulmonary arteries, VCS, phrenic, pneumogastric or cranial nerve nerves, then the esophagus and the thoracic duct.

The lower mediastinum contains the heart and vessels, as well as the phrenic nerve.

The mediastinum can be divided into two parts:

• anterior occupied by the heart,

• posterior, occupied by the esophagus, thoracic aorta, thoracic duct

The major axis of the heart is oblique towards the front and towards the left.

The heart has three walls: sterno-costal called anterior, diaphragmatic called inferior, pulmonary which corresponds to its left lateral face.

There is a top, upper, which corresponds to the large vessels that leave the apex. The posterior base is related to the so-called cardiac vertebrae at a distance: Th 6, 7 and 8. Between them is the esophagus immediately behind the base of the heart.

2. External morphology of the heart

The right edge of the heart is represented at the top by the orifice of the VCS in the upper part of the right atrium. Below, the right edge is convex to the right, constituting the lateral limit of the right atrium.

Below, the right edge is convex to the right, constituting the lateral limit of the right atrium which will extend below by the abutment orifice of the IVC.

The right atrium is extended to the left by the right auricle which extends the right atrium and which masks the origin of the aorta. The aorta arises from the apex on the left flank of the VCS. She draws a concave stock down. Its direction is oblique from right to left from front to back from the anterior mediastinum to the posterior mediastinum. The right atrium extends downward through a groove that separates the right atrium from the right ventricle.

From the top of the right ventricle emerges a very short artery trunk, which quickly divides into two: the pulmonary arteries. This bifurcation is done under the arch of the aorta. In between, there is an embryonic vestige which is, the arterial ligament, stretched from the upper part of the bifurcation of the pulmonary arteries to the lower face of the arch.

The right ventricle represents most of the sterno-costal side. It is limited on the left by an anterior ventricular groove which separates it from the left ventricle.

The left ventricle presents on this sterno-costal face an expansion which covers the upper part of the left ventricle: the left auricle.

The tip of the heart is represented essentially and only by the left ventricle.

In the posterior mediastinum, the aorta is arranged on the left flank of the vertebral body.

The left auricle is an evagination of the left atrium.

The left flank of the VCS is masked by the right auricle. The origin of the aorta lies behind the right auricle. The inter ventricular groove separates the right and left ventricles.

The major axis of the right atrium is vertical, it opposes that of the left ventricle which is transverse. The left atrium receives the four pulmonary veins which bring back the purified blood therefore enriched in O2.

The junction point between the posterior inter ventricular sulcus and the inter atrial sulcus is called the cross of the Haas sulci. Above, to the left of the IVC is the aorta. The left atrium is the most posterior part of the heart: it is related to the esophagus.

The aortic opening represents the initial part of the Aorta (the aortic bulb), at the exit of the left ventricle. This orifice is valvulated. The arrangement of the valves is called “pothole”. There are three valves: posterior semi-lunar, right and left.

This aortic orifice is located next to the orifice of the pulmonary artery which is also valvulated, same arrangement, therefore symmetrical as the orifice of the aorta. There are three valves: anterior semi-lunar, right and left.

Starting from the left atrium, there is the coronary sulcus which will make it possible to divide the arterial segments from the venous segments of the heart. This coronary groove extends on the left flank of the pulmonary artery through the left auricle, passes behind the pulmonary artery and behind the aortic orifice.

It will then separate the aortic orifice from that of the VCS. It extends in front of the aortic orifice through the right auricle. It goes forward between the right atrium and the right ventricle.

The opening of the VCS is free of any device.

The coronary sulcus separates the left atrium from the left ventricle. It passes under the left auricle which partly masks the large vessels. It passes in front of the aorta. It extends down to the anterior atrioventricular groove. This describes two systems: forward, the ear system, back, the ventricular system.

3. Anatomy of the Atrial and Ventricular Cavities

3.1. Right atrium or atrium: six walls.

The upper part is occupied by the abutment of the VCS, it is an inverted device.

The posterior part of the right auricle is smooth, without relief.

The internal part forms the partition between the two auricles it is the inter auricular septum, it presents a depression, the oval fossa. In its central part, it is bordered by an arcuate relief: the Vieussens ring.

During embryonic life, there is a system of different pressures, due to the umbilical artery: to normalize the pressures, there is an opening between the right heart and the left. At birth, the pressure reverses, it becomes much more important on the left than on the right, then there is the closure of the inter-atrial septum, that is to say individualization of the two systems, right and left.

The anterior wall is the orifice of communication with the right ventricle, it is the tricuspid orifice.

The external wall has on its surface some muscular swellings linked to the presence of pectineal muscles.

The bottom wall presents the abutment opening of the IVC. This orifice has a single valve, the Eustachi valve. It is a semi-valve, hemodynamically ineffective, which closes the light of the IVC. Another junction orifice is also described at the junction of the underside and the posterior wall: the orifice of the coronary venous sinus, which brings venous blood from the myocardial circulation back into the right atrium. This orifice is partly closed by a semi-valve, symmetrical to that of Eustachi, the valve of Th Bébéius.

In the right atrium, there is the mouth opening of the right atrium which communicates with the cavity of the right atrium. Opposite this orifice, there is in the wall the mouth of small veins which flow directly into the right atrium: the foraminula of Lannelongue, mouth of small veins which complete the coronary venous sinus.

On the outer wall, midway between the orifices of the VCI and the VCS, there is a bulge: the lower tubercle.

3.2. Right Auricle

It is a small cavity that communicates with the right atrium.

3.3. Right ventricle

It is pyramidal, triangular in shape. It represents a good part of the anterior, sternocostal face of the heart. It has 3 reinforcements on its wall, the projections:

• anterior pillar which is placed on the anterior wall of the heart

• internal pillar, on the septal wall which is internal, internal pillar or papillary muscle. It is a strengthening of the wall.

• posterior pillar, which is proportionally less marked.

Stretched between the septum and the anterior pillar, a strip: the ansiform strip. This strip is very concave up and back.

The highest part of the right ventricle is occupied by the pulmonary infundibulum, immediately opposite the initial part of the pulmonary artery which has at its origin a valve device made up of three valves.

Pillars leave the ropes, they are very resistant which will join and strengthen the valves of the tricuspid orifice.

3.4. Left atrium

Its external part presents the opening of the left auricle, same dependence as for the right auricle.

The internal part is the inter atrial septum, or inter auricular. Same relief as for the right atrium: Vieussens ring, which borders the slightly depressed, fibrous oval fossa, which is arranged at the level of the internal wall of the left atrium.

The posterior part is characterized by the orifice of mouth of the four pulmonary veins which arrive in the left auricle by its posterior face.

The upper and lower parts are smooth, narrow, concave. This atrium communicates in front and left with the left ventricle via the left atrioventricular orifice: the mitral orifice. It is occupied by a mitral valve made up of two valves: they are in the left ventricle and asymmetrical: the small mitral valve which is external and the large which it is internal.

3.5. Left ventricle

It is characterized by the thickness of its wall. It is in this part of the heart that activity is important.

There are two walls: inner wall, septal, inter ventricular septum which separates it from the right ventricle and an outer wall, thick.

We can divide the left ventricle into two parts:

• an ear chamber, between the outer wall of the left ventricle and the small mitral valve;

• a wider arterial chamber between the large mitral valve and the inter ventricular septum;

The partitioning is done by means of ropes which start from two pillars which are anterior and posterior. The ropes will go from these pillars to the ends of the two mitral valves. From the arterial chamber, the blood reaches the Aorta, which originally has a valve, made up of three semi-valves.

4. Arterial Vascularization of the Heart

It is provided by two arteries: the right and left coronary arteries. These arteries are susceptible to numerous anatomical variations, both in terms of their origin and in terms of their ramifications.

They arise from the aorta at its origin, the aortic bulb.

4.1. Right Coronary

It arises from the Aorta just above the right semi-lunar valve. His journey breaks down into three parts:

1. It travels in the coronary sulcus, masked at its origin by the right auricle. It appears in the right atrioventricular groove to the underside of the heart.

2. There, it passes under the heart, under the left flank of the VCI. She walks to the cross of the furrows of Haas.

3. It engages in the posterior interventricular groove and becomes the posterior ventricular branch. It is gradually running out.

Its collateral: in the first part of the journey, it gives:

• branches of the arterial cone (which go towards the pulmonary artery), one of which is longer: the right marginal branch

• it leaves some branches for the right atrium and especially a branch of the sinu-atrial node which belongs to the nodal tissue of the heart

in the second part of the path, it gives some collateral for the postero-inferior part of the right ventricle.

in the third part of its path, it gives branches for the right ventricle, and some branches for the left ventricle and the inter ventricular septum. (The twigs provide part of the vascularization of the node and the atrioventricular bundle, which belong to the nodal tissue).

4.2. Left Coronary

In general, it is larger than the right. It arises from the initial part of the aorta with the aortic bulb, opposite the left aortic semi-lunar valve. From there, it travels transversely in the groove coronary, will pass behind the pulmonary artery and on the left flank of the pulmonary artery, it is divided into two terminal branches:

• an anterior branch, the anterior inter ventricular branch which leads forward in the anterior inter ventricular groove. From there, it bypasses the tip of the heart by decreasing in volume to exhaust itself in the posterior inter ventricular groove

• a posterior branch, the circumflex artery. It travels in the coronary sulcus where it is masked at its origin by the left auricle. She heads back towards the cross of the Haas furrows without reaching it.

The two arteries abandon collaterals: for the anterior inter ventricular artery, it gives collaterals for the right ventricle, the left ventricle, and for the inter ventricular septum. For the circumflex artery, it gives branches for the sinu-atrial node, collaterals for the left ventricle and a more important branch: the left marginal branch. There is also an intermediate atrial branch which participates in the vascularization of the left atrium.

The coronary vessels and coronary arteries are most often superficial, but can become deep, and travel in the thickness of the myocardium. The left coronary artery occupies most of the wall and the upper half of the inter ventricular septum. It participates little in the vascularization of the wall of the right ventricle. It supports the left half of the left atrium.

The right coronary artery supplies a part of the heart less important than the left but supports the vascularization of the sinu-atrial node, and also of the node and the atrioventricular bundle.

5. Cardionector fabric

It is the nodal tissue. These are primitive embryonic cells which ensure cardiac automatism and which make it possible to establish all the functional connections which exist between the atrium and the ventricle.

The nodal tissue consists of two distinct portions:

• the pure atrial portion located in the right atrium near the delivery of the VCS, it is the sinus node of Keith and Flack

• the ventricular apparatus, “ventriculonector”, called bundle of His, itself made up of two parts:

– Ashoff Tavara’s knot located in the right atrium in its anterior and lower part

– the His bundle or atrioventricular bundle. Its fibers gather in two centers, the knot of Ashoff Tavara, to which follows the trunk of the bundle of His: the knot of Zann.

The separation between the two hearts is done by an inter ventricular septum, an inter atrial septum, and an atrio ventricular septum.

The bundle of His bundle is divided into two branches, one straight for the right ventricle, which runs through the inter ventricular septum, then the ansiform strip at the tip to join the anterior pillar of the right ventricle, and the other which arises from the trunk. and which travels under the endocardium of the left ventricle to branch into several branches which run along the entire wall of the left ventricle to the left branch of the bundle of His.

The terminal network of the right branch is called the Purkinje network.

Between the nodes of Keith and Flack and Ashoff Tavara, there are three very difficult to individualize beams which make the connection between the nodes and the cardionector system.

This set makes the harmonious character of the contraction / coordination between the right system and the left which gives the heart its automatism.

On this nodal tissue, the cardiac nerves will act:

• sympathetic system which accelerates the heart, strengthens contractility and increases sensitivity;

• and the parasympathetic system which has effects opposite to the previous one.

6. Pericardial cavity

The heart is located in the chest cavity. It rests on the diaphragm. It occupies a relatively middle position, but overflows to the left. It is attached to the diaphragm mainly through the pericardium.

The pericardium consists of two parts:

• external part: the fibrous pericardium which surrounds the heart, adheres below the diaphragm, and which will provide most of the flexibility to the heart inside the fibrous pericardium.

• internal part: the serous pericardium, consisting of two sheets, a parietal lamina which is arranged on the deep face of the fibrous pericardium and which will be reflected to cover the myocardium, constituting the visceral lamina, the epicardium.

These two blades limit the pericardial cavity which contains a liquid, small in volume, but which facilitates cardiac contractility.

The epicardium is the reflection of the parietal lamina.

The line of reflection of the serous pericardium is irregular. The pericardium will constitute two distinct pericardial sleeves: one arterial, which surrounds the aorta and the pulmonary artery, the other, venous.

6.1. Arterial Sleeve

It covers the two arterial elements: – Aorta – pulmonary arteries -.

For the aorta: the line of reflection rises high to the initial part of the aorta. It will bend after having drawn a dead end: Haller’s big horn. The line of reflection then reaches the anterior aspect of the pulmonary artery to the lower part of the left pulmonary artery. Then it goes around the left edge of the pulmonary artery, we find it behind where it ties the posterior face of the pulmonary artery, it draws in front the small Haller’s horn, it is practically horizontal on the posterior face of the pulmonary artery, it goes up on the right edge of the Aorta to join the big horn.

6.2. Venous Sleeve

It is more complex, irregular. This sleeve is above the left atrium, then runs along the upper edge of the left atrium, passing in front of the upper left pulmonary vein. It is then found on the left edge of the left auricle and then in front of the lower left pulmonary vein. From there, it goes up to cover the left edge of the left atrium. It remains at a distance from the upper edge of the left atrium and descends vertically, runs through the right edge of the left atrium and reaches the left edge of the IVC.

There, the line of reflection passes in front of the VCI and is reflected on the right edge to be back again, oblique at the top left. It passes in front of the lower right pulmonary vein then in front of the upper right pulmonary vein and changes direction: it ties the posterior face of the right atrium from bottom to top, from left to right to gain the right edge of the VCS. There, he ties the anterior face of the VCS, joins the upper edge of the left atrium and thus closes the venous reflection zone.

It is a fairly irregular arrangement. There are still two evaginations of the pericardial cavity:

• the oblique sinus of the pericardium which corresponds to the extension of the pericardial cavity located on the posterior surface of the left atrium

• the transverse sinus of the pericardium, between the arterial elements. It is limited between the arterial line of reflection in front and the venous line of reflection behind it. The anterior limit of this sinus is formed on the right by the posterior aspect of the aorta, on the left by the posterior aspect of the pulmonary artery, behind, by the left atrium, below by the coronary sinus. This sinus communicates right and left with the pericardial cavity.

The right communication opening is limited on the right by the VCS and on the left by the aorta. On the left, it communicates with the pericardial cavity; it will be limited by the trunk of the pulmonary artery and the left auricle.

This pericardial cavity is not very extensible because of the fibrous pericardium. Under certain pathological conditions, an abnormal effusion can significantly increase the content of the pericardial cavity, which leads to a narrowing of the myocardium, therefore a decrease in contractility. Only solution: puncture.

7. The aorta

The Aorta arises to the left of the VCS and it draws a curve: the aortic arch. It can be broken down into three parts: initial, ascending part, masked at its origin by the right auricle. It is oblique upwards and to the right. The direction will bend and it becomes horizontal before passing behind the left pulmonary artery. It therefore has a double direction: right to left, front to back. Then after a horizontal part, a descending part.

The aorta abandons collaterals:

• arising from the aortic bulb, the right and left coronary arteries.

• emerging from the horizontal part, the three supra aortic trunks:

• brachio cephalic arterial trunk it goes upwards and to the right to reach the medial flank of the brachiocephalic venous trunk where it will be divided into two: right primitive carotid artery, right subclavian artery.

• downstream, the left primary carotid artery which rises vertically and crosses the brachio cephalic venous trunk from behind

• even further downstream, the left subclavian artery which is vertical in the first part and horizontal in its second part

The arch of the aorta runs from right to left back and forth. It gains the left flank of Th4.

“Cross section” = we cut in Th4, ie a section which passes through the arch of the aorta and through the butt of the azygos vein, just before it enters the VCS through its posterior surface . The aorta surrounds the trachea, it is located immediately in front of the esophagus. The pleura covers these elements and forms the anterior pleural cul-de-sac anteriorly.

On the aorta, at the level of the horizontal part, the pneumogastric nerve or Xth cranial nerve called vagus nerve) passes under the arch, on the left, and abandons its recurrent which rises in the left oesotracheal angle. The Xth right cranial nerve abandons its recurrent under the right subclavian artery, right recurrent which goes up in the right esotracheal angle.

On the left side of the aortic arch, there are the cardiac nerves. The thoracic duct goes back to the left and flows into the left jugulocutaneous trunk.

The aorta descends after its arch to the diaphragm, where it becomes the abdominal aorta

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