THE HEART THE HEART MEDIASTINUM PERICARDIUM HEART THE HEART THE - - PowerPoint PPT Presentation

THE HEART

THE HEART

• MEDIASTINUM
• PERICARDIUM
• HEART

THE MEDIASTINUM The medias5num occupied by the mass of 2ssue between the two pulmonary cavi2es, is the central compartment of the thoracic cavity.

THE HEART

The medias2num is an interpleural space and consists of the superior medias2num and inferior medias2num, which divides into the anterior, middle, and posterior medias2na.

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THE SUPERIOR MEDIASTINUM The superior medias5num contains the SVC, brachiocephalic veins, arch of the aorta, thoracic duct, trachea, esophagus, thymus, vagus, leB recurrent laryngeal, and phrenic nerves. The superior vena cava (SVC) returns blood from all structures superior to the diaphragm, except the lungs and heart. The arch of the aorta (aor5c arch), the curved con2nua2on of the ascending aorta. The arch of the azygos vein occupies a posi2on corresponding to the aorta on the right side of the trachea over the root of the right lung, although the blood is flowing in the opposite direc2on. The ligamentum arteriosum, the remnant of the fetal ductus arteriosus, passes from the root of the leB pulmonary artery to the inferior surface of the arch of the aorta. The brachiocephalic trunk, the first and largest branch of the arch of the aorta, arises posterior to the manubrium, where it is anterior to the trachea and posterior to the leB brachiocephalic vein.

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THE SUPERIOR MEDIASTINUM The leJ common caro5d artery, the second branch of the arch of the aorta, arises posterior to the manubrium, slightly posterior and to the leB of the brachiocephalic trunk. The leJ subclavian artery, the third branch of the arch of the aorta, arises from the posterior part of the arch, just posterior to the leB common caro2d artery. The right vagus nerve (RVN) enters the thorax anterior to the right subclavian artery, where it gives rise to the right recurrent laryngeal nerve. The leJ vagus nerve (LVN) descends in the neck posterior to the leB common caro2d artery

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THE SUPERIOR MEDIASTINUM The leJ vagus nerve (LVN) is separated laterally from the phrenic nerve by the leB superior intercostal vein. As the LVN curves medially at the inferior border of the arch of the aorta, it gives off the leJ recurrent laryngeal nerve. The leB recurrent laryngeal nerve passes inferior to the arch of the aorta, immediately lateral to the ligamentum arteriosum, and ascends to the larynx in the groove between the trachea and the esophagus.

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THE ANTERIOR MEDIASTINUM The anterior medias5num contains the remnants of the thymus gland, lymph nodes, and fat.

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THE MIDDLE MEDIASTINUM The middle medias5num contains the

• heart,
• pericardium,
• phrenic nerves,
• roots of the great vessels,
• arch of the azygos vein, and
• main bronchi.

The posterior medias5num contains the

• esophagus,
• thoracic aorta,
• azygos and hemiazygos veins,
• thoracic duct,
• vagus nerves,
• sympathe2c trunks,
• splanchnic nerves.

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THE POSTERIOR MEDIASTINUM

The middle medias5num includes the pericardium, heart, and roots

• f its great vessels:
• ascending aorta,
• pulmonary trunk,
• SVC.

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THE PERICARDIUM The pericardium is a fibroserous membrane that covers:

• the heart and
• the beginning of its great vessels.

The tough external layer, the fibrous pericardium, is con2nuous with the central tendon of the diaphragm.

The internal surface of the fibrous pericardium is lined with a glistening serous membrane, the parietal layer of serous pericardium.

THE HEART

THE PERICARDIUM The parietal layer of serous pericardium is reflected onto the heart at the great vessels (aorta, pulmonary trunk and veins, and superior and inferior venae cavae) as the visceral layer of serous pericardium.

The fibrous pericardium is:

• con2nuous superiorly with the tunica adven55a of the great

vessels entering and leaving the heart and with the pretracheal layer of deep cervical fascia.

• aOached anteriorly to the posterior surface of the sternum by the

sternopericardial ligaments, which are highly variable in their development.

• bound posteriorly by loose connec2ve 2ssue to structures in the

posterior medias2num.

• con2nuous inferiorly with the central tendon of the diaphragm

THE HEART

THE PERICARDIUM

The inferior wall (floor) of the fibrous pericardial sac is firmly aOached and confluent (par2ally blended) centrally with the central tendon of the diaphragm - the pericardiacophrenic ligament.

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THE PERICARDIUM The pericardium is influenced by movements of the heart and great vessels, the sternum, and the diaphragm.

The pericardial cavity is the poten5al space between opposing layers

• f the parietal and visceral layers of serous pericardium. It normally

contains a thin film of fluid that enables the heart to move and beat in a fric2onless environment.

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THE PERICARDIUM The visceral layer of serous pericardium forms the epicardium, the

• utermost of three layers of the heart wall.

The transverse pericardial sinus is a transversely running passage within the pericardial cavity between these two groups

• f vessels and the reflec2ons of serous pericardium around

them.

A pericardial reflec2on surrounding the veins of the heart forms the

• blique pericardial sinus, a wide pocket-like recess in the pericardial

cavity posterior to the base (posterior aspect) of the heart, formed by the leJ atrium

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THE PERICARDIUM The arterial supply of the pericardium is mainly from a slender branch

• f the internal thoracic artery, the pericardiacophrenic artery.

The nerve supply of the pericardium is from the:

• Phrenic nerves (C3–C5), primary source of sensory fibers; pain

sensa2ons conveyed by these nerves are commonly referred to the skin (C3–C5 dermatomes) of the ipsilateral supraclavicular region (top of the shoulder of the same side).

• Vagus nerves, func2on uncertain.
• Sympathe5c trunks, vasomotor.

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THE PERICARDIUM

The Func5on of the Pericardium:

• Protects and anchors the heart
• Prevents overfilling of the heart with blood
• Allows for the heart to work in a rela2vely fric2on-free

environment

THE HEART

THE PERICARDIUM

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THE HEART

• Center of the cardiovascular system, the heart.
• Connects to blood vessels that transport blood between the

heart and other body 2ssues.

• arteries carry blood away from the heart
• veins carry blood back to the heart
• Arteries carry blood high in oxygen.
• (except for the pulmonary arteries)
• Veins carry blood low in oxygen.
• (except for the pulmonary veins)
• Arteries and veins entering and leaving the heart are called the

great vessels

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THE HEART

• Ensures the unidirec5onal flow of blood through both the heart

and the blood vessels.

• Backflow of blood is prevented by valves within the heart.
• Acts like two independent, side-by-side pumps that work

independently but at the same rate. (double circuit)

• one directs blood to the lungs for gas exchange
• the other directs blood to body 5ssues for nutrient delivery

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THE HEART Vessels returning blood to the heart include: 1. Superior and inferior venae cavae 2. Right and leB pulmonary veins

THE HEART

THE HEART Vessels conveying blood away from the heart include: 1. Pulmonary trunk, which splits into right and leB pulmonary arteries 2. Ascending aorta (three branches) – a. Brachiocephalic b. LeB common caro2d c. Subclavian arteries

THE HEART

THE HEART Vessels returning blood to the heart include: 1. Superior and inferior venae cavae 2. Right and leB pulmonary veins Vessels conveying blood away from the heart include: 1. Pulmonary trunk, which splits into right and leB pulmonary arteries 2. Ascending aorta (three branches) – a. Brachiocephalic b. LeB common caro2d c. Subclavian arteries

THE HEART

ATRIA OF THE HEART

• Atria are the receiving chambers of the heart
• Each atrium has a protruding auricle
• Pec5nate muscles located within the anterior wall of the right

atrium

• Blood enters right atria from superior and inferior venae cavae

and coronary sinus

• Blood enters leJ atria from pulmonary veins

THE HEART

VENTRICULES OF THE HEART

• Ventricles are the discharging chambers of the heart
• Papillary muscles and trabeculae carneae muscles mark

ventricular walls

• Right ventricle pumps blood into the pulmonary trunk
• LeJ ventricle pumps blood into the aorta
• Myocardium of leJ ventricle is much thicker than the right.

THE HEART

PATHWAY OF BLOOD THROUGH THE HEART AND LUNGS

• Right atrium à tricuspid valve à

right ventricle

• Right ventricle à pulmonary

semilunar valve à pulmonary arteries à lungs

• Lungs à pulmonary veins à leB

atrium

• LeB atrium à bicuspid valve à

leB ventricle

• LeB ventricle à aor5c semilunar

valve à aorta

• Aorta à systemic circula2on

The right side of the heart (right heart) receives poorly oxygenated (venous) blood from the body through the SVC and IVC and pumps it through the pulmonary trunk and arteries to the lungs for

• xygena2on.

THE HEART

THE HEART The leJ side of the heart (leJ heart) receives well-oxygenated (arterial) blood from the lungs through the pulmonary veins and pumps it into the aorta for distribu2on to the body.

The heart has four chambers:

• right and leB atria
• right and leB ventricles.

THE HEART

THE HEART The atria are receiving chambers that pump blood into the ventricles (the discharging chambers). The wall of each heart chamber consists of three layers, from superficial to deep:

• 1. Endocardium
• 2. Myocardium
• 3. Epicardium

The wall of each heart chamber consists of three layers, from superficial to deep:

• 1. Endocardium, a thin internal layer (endothelium and

subendothelial connec2ve 2ssue) or lining membrane of the heart that also covers its valves.

• 2. Myocardium, a thick, helical middle layer composed of cardiac

muscle.

• 3. Epicardium, a thin external layer (mesothelium) formed by the

visceral layer of serous pericardium.

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THE HEART The cardiac muscle fibers are anchored to the fibrous skeleton of the heart.

• the apex of the heart
• the base of the heart
• right (acute) border
• leB (obtuse) border

THE HEART

THE HEART The apex of the heart is the blunt rounded extremity of the heart formed by the leB ventricle and lies in the leJ fiJh intercostal space slightly medial to the midclavicular line. This loca2on is useful clinically for determining the leB border of the heart and for ausculta2ng the mitral valve. Its posterior aspect, called the base, is formed primarily by the leB atrium and only partly by the posterior right atrium.

Its right (acute) border is formed by: the SVC, right atrium, and IVC.

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THE HEART Its leJ (obtuse) border is formed by the leB ventricle. (In radiology, the le1 border consists of the aor6c arch, pulmonary trunk, le1 auricle, and le1 ventricle.)

The four surfaces of the heart are the:

• 1. Anterior (sternocostal) surface
• 2. Diaphragma2c (inferior) surface
• 3. Right pulmonary surface
• 4. LeB pulmonary surface

THE HEART

THE HEART

The four surfaces of the heart are the:

• 1. Anterior (sternocostal) surface, formed mainly by the

right ventricle.

• 2. Diaphragma5c (inferior) surface, formed mainly by the leB ventricle

and partly by the right ventricle; it is related mainly to the central tendon of the diaphragm.

• 3. Right pulmonary surface, formed mainly by the right

atrium.

• 4. LeJ pulmonary surface, formed mainly by the leB ventricle;

it forms the cardiac impression in the leB lung.

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The right atrium forms the right border of the heart and receives venous blood from the SVC, IVC, and coronary sinus.

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THE RIGHT ATRIUM The ear-like right auricle is a conical muscular pouch that projects from this chamber like an add-on room, increasing the capacity of the atrium as it overlaps the ascending aorta. The opening of the coronary sinus, a short venous trunk receiving most of the cardiac veins, is between the right AV orifice and the IVC

• rifice.

The interatrial septum separa2ng the atria has an oval, thumbprint- size depression, the oval fossa, which is a remnant of the oval foramen and its valve in the fetus.

The right ventricle forms the largest part of the anterior surface

• f the heart.

THE HEART

THE RIGHT VENTRICLE The inflow part of the ventricle receives blood from the right atrium through the right AV (tricuspid) orifice Tendinous cords aOach to the free edges and ventricular surfaces of the anterior, posterior, and septal cusps, much like the cords aOaching to a parachute. The tendinous cords arise from the apices of papillary muscles The inflow part of the right ventricle is separated from the ou]low part by the supraventricular crest.

Three papillary muscles in the right ventricle correspond to the cusps

• f the tricuspid valve:
• anterior papillary muscle
• posterior papillary muscle
• septal papillary muscle

THE HEART

THE RIGHT VENTRICLE

The leJ atrium forms most of the base of the heart

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THE LEFT ATRIUM The muscular leJ auricle forms the superior part of the leB border of the heart and overlaps the root of the pulmonary trunk Four pulmonary veins (two superior and two inferior) entering its smooth posterior wall

The leJ ventricle forms the apex of the heart, nearly all its leB (pulmonary) surface and border, and most of the diaphragma5c surface.

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THE LEFT VENTRICLE Walls that are two to three 5mes as thick as those of the right ventricle A double-leaflet mitral valve that guards the leB AV orifice The mitral valve has two cusps, anterior and posterior. An aor5c orifice that lies in its right posterosuperior part Tendinous cord in the leB ventricle arise from the apices of the anterior and posterior papillary muscles

Each of three semilunar cusps of the pulmonary valve (anterior, right, leB), like the semilunar cusps of the aor5c valve (posterior, right, leB), is concave when viewed superiorly

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THE SEMILUNAR VALVES

The blood vessels of the heart comprise the coronary arteries and cardiac veins, which carry blood to and from most of the myocardium

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THE VASCULATURE OF HEART The coronary arteries, the first branches of the aorta, supply the myocardium and epicardium. The coronary arteries supply both the atria and the ventricles The right coronary artery (RCA) arises from the right aor2c sinus of the ascending aorta. The leJ coronary artery (LCA) arises from the leB aor2c sinus of the ascending aorta The heart is drained mainly by veins that empty into the coronary sinus and partly by small veins that empty into the right atrium

The conduc5ng system of the heart generates and transmits the impulses that produce the coordinated contrac2ons of the cardiac cycle

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REGULATING SYSTEMS OF HEART The sinu-atrial (SA) node is located anterolaterally just deep to the epicardium at the junc2on of the SVC and right atrium. The SA node is supplied by the sinu-atrial nodal artery, which usually arises as an atrial branch of the RCA (in 60% of people), but it oBen arises from the LCA (in 40%).

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REGULATING SYSTEMS OF HEART The atrioventricular (AV) node is a smaller collec2on of nodal 2ssue than the SA node. The AV node distributes the signal to the ventricles through the AV bundle. The AV bundle divides into right and leB bundles, proceed on each side of the muscular IVS deep to the endocardium and then ramify into subendocardial branches (Purkinje fibers). The atrioventricular (AV) is located in the posteroinferior region of the interatrial septum near the opening of the coronary sinus.

The synchronous pumping ac2ons of the heart’s two atrioventricular (AV) pumps (right and leB chambers) cons2tute the cardiac cycle.

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THE HEART The cycle begins with a period of ventricular elonga2on and filling (diastole) and ends with a period of ventricular shortening and emptying (systole).

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CARDIAL CYCLE The inclusive period of 2me from the start of one heartbeat to the ini5a5on of the next. All chambers within the heart experience alternate periods of contrac5on and relaxa5on. Contrac5on of a heart chamber is called systole.

• forces blood into another chamber (from atrium to ventricle)
• forces blood into a blood vessel (from a ventricle into the

aOached large artery) Relaxa5on phase of a heart chamber is termed diastole.

• myocardium of each chamber relaxes between contrac2on

phases

• and the chamber fills with blood

Two heart sounds are heard with a stethoscope: LUB (1st) sound as the blood is transferred from the atria into the ventricles, DUB (2nd) sound as the ventricles expel blood from the heart.

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THE HEART