Pericardium: Anatomy, Function, and Treatment Question And Answers

Parietal Pericardium

Question 1. Write a short note on the pericardium. 
Answer:

Pericardium is a fibro serous sac in the middle mediastinum. It encloses the heart and roots of the great vessels.

Pericardium consists of two parts:

1. Fibrous pericardium and
2. Serous pericardium.

Read And Learn More: Anatomy Question And Answers

Fibrous pericardium

• The fibrous pericardium is a cone-shaped outer fibrous sac around the heart and roots of great blood vessels. Its apex is narrow and blunt.
• Fibrous pericardium lies at the level of the sternal angle where it fuses with the tunica adventitia of the pulmonary trunk and ascending aorta.
• Fibrous pericardium  base is broad. It blends with the central tendon of the diaphragm.

Serous Pericardium

• The serous pericardium is the inner double-layered sac of the serous membrane. It consists of two layers: an outer parietal layer and an inner visceral layer.
• The parietal layer lining the inner surface of the fibrous pericardium is called the parietal pericardium.
• Visceral layer covering the heart is called the epicardium

Note: The two layers are continuous with each other at the roots of great blood vessels.

The potential space between the two layers is called the pericardial cavity. It contains only a thin film of serous fluid, which lubricates the opposed surfaces of parietal and visceral layers to allow the free movements of the heart.

Question 2. Write a short note on the Transverse Sinus of the Serous Pericardium.
Answer:

In embryonic life, it is a horizontal recess of serous pericardium between the arterial and venous ends of the heart tube. It develops due to degeneration of dorsal mesogastrium.

In adult life, it lies behind the ascending aorta and pulmonary trunk (arterial end of the heart tube) and in front of the superior vena cava and superior pulmonary veins (venous end of the heart tube).

Transverse sinus Boundaries

• Transverse sinus Anterior: Ascending aorta and pulmonary trunk.
• Transverse sinus Posterior: Superior vena cava, upper margin of left atrium, and superior pulmonary veins.
• Transverse sinus On each side: Pericardial cavity.

Transverse Sinus of the Serous Pericardium Applied anatomy:

• During cardiac surgery, a temporary ligature is passed through the transverse sinus.
• The tubes of the heart and lung machine are inserted into great vessels of the heart, and then, the ligature is tightened.

 

Question 3. Write a short note on the oblique sinus of the pericardium. 
Answer:

Oblique Sinus

Oblique Sinus is a narrow cul-de-sac of serous membrane behind the left atrium of the heart.  It is closed on all sides except inferiorly where it communicates with the rest of the pericardial cavity.  It develops due to the absorption of pulmonary veins into the left atrium. It is formed by the reflected part of the parietal pericardium.

Oblique Sinus Pericardium Boundaries:

• Oblique Sinus Pericardium Anterior: Visceral pericardium covering the posterior surface of left atrium.
• Oblique Sinus Pericardium Posterior: Parietal pericardium lining the posterior surface of fibrous pericardium
• Oblique Sinus Pericardium Right side: Pericardial reflection along with the right pulmonary veins and inferior vena cava.
• Oblique Sinus Pericardium Left side: Reflection of pericardium along with the left pulmonary veins.
• Oblique Sinus Pericardium Above: Pericardial reflection along with the upper margin of left atrium.

Oblique Sinus Pericardium Functions:

• Oblique Sinus Pericardium permits the free pulsations of the left atrium.
• Oblique Sinus Pericardium suspends the heart in the pericardial cavity.

Oblique Sinus Applied anatomy

• Oblique Sinus Pericarditis: It is the inflammation of serous pericardium. The pain of pericarditis is referred to the epigastrium.
• Oblique Sinus Pericardial Effusion: It is the collection of fluid in the pericardial cavity.
• Oblique Sinus Cardiac Tamponade: It is a condition, in which there is a rapid accumulation of large volume of fluid (serous fluid or blood) in the pericardial cavity. This leads to compression of the heart from the outside.

The effects of cardiac tamponade are as follows:

• Interferes with the filling of atria during diastole
• Causes decrease in the cardiac output
• Causes an increase in the heart rate and venous pressure

Note: Cardiac tamponade can cause death within a short time; hence immediate aspiration of fluid is necessary to restore the normal cardiac output.

Parietal Pericardium

Question 4. Enumerate the contents of the pericardium.
Answer:

Contents of the Pericardium

These are:

• Heart
• Coronary vessels
• Ascending aorta
• Pulmonary trunk
• Lower half of the superior vena cava
• Terminal part of the inferior vena cava
• Terminal parts of the pulmonary veins

Heart

Question 5. Define the apex of the heart and the apex beat. Discuss the clinical significance of apex
beat.
Answer:

Apex of the heart:

• It is the outermost and lowermost conical part of the heart formed by the left ventricle.
• It is situated in the left 5th intercostal space, 9 cm (3½ “) lateral to the midsternal line/just medial to the midclavicular line.

Apex beat (also called cardiac pulse):

• It is the lowermost and outermost thrust of the heart against the chest wall in the region of left precordium during systole.
• In the adults, it is felt in the left 5th intercostal space, 9 cm (3½ “) lateral to the midsternal line, just medial to the midclavicular line.
• In the children, it is felt in the left 2nd or 3rd intercostal space, just lateral to the midclavicular line.

Question 6. Describe the right atrium of the heart in brief under the following headings:
Answer:

1. Right Atrium Of The Heart External features
2. Right Atrium Of The Heart Internal features and
3. Right Atrium Of The Heart Development.

Answer:

Right Atrium Of The Heart  is the right upper chamber of the heart, which receives venous blood from all parts of the body and pumps it into right ventricle through right atrioventricular orifice.

1. Right Atrium Of The Heart External features

• Right Atrium Of The Heart receives superior vena cava (SVC) from above, inferior vena cava (IVC) from below and coronary sinus on its posterior aspect.
• Presents a small conical projection to the left, from its upper end – the right auricle. Its margins are notched and overlaps ascending aorta.
• Right Atrium Of The Heart right border presents a shallow vertical groove/sulcus, which extends from
• SVC to the inferior IVC. It is produced by a muscular ridge inside called crista terminalis. The atrial wall deep to upper part of sulcus contains SA node.

2. Right Atrium Of The Heart  Internal features (interior of the right atrium):

The interior of the right atrium is divided into 3 parts:

1. The smooth posterior part
2. Rough anterior part and the
3. Septal wall

The smooth posterior part presents the following features:

• Opening of superior vena cava at its upper end.
• Opening of inferior vena cava at its lower end. It is guarded by a rudimentary semilunar valve called the valve of inferior vena cava/Eustachian valve.
• Opening of coronary sinus between the opening of IVC and right atrioventricular (AV) orifice. It is guarded by a valve ofthe coronary sinus.
• Foramina venarum minimum (minute openings of venae cordis minimae, the numerous small veins present in the walls of all the chambers of the heart.
• Intervenous tubercle (lower): a small projection on the posterior wall of atrium just below the opening of SVC.

The rough anterior part presents the following features :

• Crista terminalis: It is an internal muscular ridge extending vertically from right side of SVC to the right side of the IVC.
• Musculi pectinate: These are transverse ridges, which arise from crista terminalis and run forward and downward toward the atrioventricular orifice for insertion. The musculi pectinate resembles the teeth of a comb.

Septal wall: Septal wall i.e. the right side of interatrial septum, presents the following features:

• Fossa ovalis is a shallow oval depression in the lower part near the opening of the inferior vena cava.
• Limbus fossa ovalis is the prominent sickle-shaped sharp margin surroundingm the upper and posterior margins of the fossa ovalis.
• Triangle of Koch is a triangular area bounded in front by the base of the septal leaflet of the tricuspid valve, behind by the anteromedial margin of the opening of the coronary sinus and above by the tendon of Todaro.

The AV node lies in this triangle:

 

3. Right Atrium Of The Heart  Development

• The smooth posterior part (or sinus venarum) develops from right horn of the sinus venosus.
• Rough anterior part (or pectinate part) develops from primitive atrial chamber.

Parietal Pericardium

Question 7. Describe the Sternocostal surface of the heart in brief and discuss its applied anatomy. 
Answer:

The sternocostal surface of the heart faces forward, upward, and to the left. It has 3 borders, i.e., right, inferior, and left, which separate it from the base, diaphragmatic surface, and left surface, respectively.

Sternocostal Surface Formation:

Sternocostal Surface is formed by:

• Anterior surface of the right atrium and right auricle
• Anterior surface of the right ventricle (⅔rd)
• A small strip of the anterior surface of left ventricle and left auricle

Sternocostal Surface Features

• The anterior part of the atrioventricular (coronary) sulcus: Passes downward and to the right from the right of the roots of great vessels to the junction of the right and inferior borders. It contains the trunk of the right coronary artery.
• Anterior interventricular groove passes:  Downward parallel to the left border of the heart and contains the anterior interventricular (left anterior descending) branch of the left coronary artery and great cardiac vein.

Sternocostal Surface Relations

• Covered by pericardium
• Anterior margins of both lungs and pleurae
• The posterior surface of a body of the sternum and the 3rd to 6th costal cartilages of both sides

Sternocostal Surface Applied anatomy:

• Area of superficial cardiac dullness: Most of the sternocostal surface of heart is covered by lungs except the part which lies behind the cardiac notch of the left lung, i.e. below the left 4th costal cartilage where the pericardium comes in direct contact with the sternum. This area is dull on percussion as it is not covered by the lungs, hence it is called as area of superficial cardiac dullness.
• During open-heart surgery: The sternocostal surface is exposed by incising the pericardium.

Question 8. Give a brief account of conducting system of the heart. 
Answer:

Heart is made up of modified cardiomyocytes specialized for initiation and conduction of cardiac impulses.

Conducting System Parts

Heart consists of following parts:

• Sinoatrial node (SA node):
  • It is situated in the right atrium below the opening of SVC in the upper part of sulcus terminalis.
  • I is also known as the ‘pacemaker’ of the heart.
•  Atrioventricular node (AV node): It is situated in the lower and dorsal part of the interatrial septum near the opening of the coronary sinus.
• Atrioventricular bundle (AV bundle): It connects the atrial and ventricular musculature.
• Right and left bundle branches: They pass on respective sides in the interventricular septum.
• Purkinje fibers: They arise from the right and left bundle branches and form the subendocardial plexus.

Conducting System of the Heart Applied anatomy:

Defects of conducting system lead to cardiac arrhythmias.

Parietal Pericardium

Question 9. Describe the Arterial Supply of the Heart in brief.
Answer:

The heart is supplied by two coronary arteries, right and left, which arise from the ascending aorta.

Right coronary artery:

It is smaller than the left coronary artery. It arises from the anterior aortic sinus of ascending aorta and descends in the right anterior part of the coronary sulcus up to the junction of right and inferior margins of the heart.

Here, it gives a marginal branch to the lower margin of the sternocostal surface.

• Then it curves around the lower margin of the heart to reach the diaphragmatic surface where it continues in the right posterior part of the coronary sulcus.
• After crossing the crux of the heart, it terminates by anastomosing with the circumflex branch of the left coronary artery.

Right coronary artery Branches:

Right coronary artery are:

• Larger branches:
  • Marginal artery
  • Posterior interventricular artery
• Smaller branches:
  • SA nodal artery in 60% cases
  • Right conus artery
  • Unnamed branches to the right atrium and left ventricle

Left coronary artery:

It is larger than the right coronary artery. It arises from the left posterior aortic sinus. It passes to the left between the pulmonary trunk and the left auricle.

• Here, it gives the anterior interventricular artery, and then, it curves around the left border of the heart to continue as the circumflex artery in the left posterior coronary sulcus .
• Near the posterior interventricular sulcus, it terminates by anastomosing with the right coronary artery.

Left coronary artery Branches:

These are:

• Larger branches:
  • Anterior interventricular/left anterior descending artery (LAD)
  • Diagonal artery
  • Circumflex artery
• Smaller branches:
  • Left conus artery
  • Unnamed branches to the left atrium and left ventricle

Arterial Supply of the Heart Applied anatomy:

• Angina pectoris:
  • It is pain (moderately severe) felt in the left precordium, which often radiates to the left shoulder, and medial side of the left arm and forearm.
  • It usually occurs on exertion which remains for about 20 min and is relieved on taking rest.
  • The angina pectoris occurs due to the narrowing of coronary arteries, leading to transient ischemia of cardiac muscle.
• Myocardial infarction (MI): A sudden blockage of one of the major branches of coronary arteries leads to myocardial ischemia and myocardial necrosis. It often leads to death. Clinically, it presents as:
  • Sinking pain in the chest for more than 30 min
  • Nausea, vomiting, sweating, shortness of breath, and tachycardia
  • Pain radiates to the left shoulder, left side of arm, and forearm

The arteries commonly blocked in order of frequency are:

• Anterior interventricular artery/left anterior descending artery (LAD) = 40–50%
• Right coronary artery = 30–40%
• Circumflex branch of left coronary artery = 15–20%

Question 10. Give a brief account of Coronary Dominance.
Answer:

• If the posterior interventricular artery arises from the right coronary artery, it is called the right coronary dominance (80%) case.
• On the other hand, if the posterior interventricular artery arises from the left coronary artery, it is called left coronary dominance (20% of cases).
• Thus mostly, there is a right coronary dominance.

Coronary Dominance Note:

In balanced coronary dominance, both coronary arteries give rise to the posterior interventricular artery. Both the posterior interventricular arteries run parallel to each other in posterior interventricular sulcus.

Question 11. What is the Third Coronary Artery?
Answer:

• In 36% cases, the right conus artery arises separately from the anterior aortic sinus and is termed the third coronary artery.
• Note in 64% of cases, it is the first branch of right coronary artery.

Question 12. Describe in brief the venous drainage of the heart.
Answer:

• The venous blood from the heart is drained by the following veins:
• Great cardiac vein, follows the anterior interventricular artery
• The middle cardiac vein follows the posterior interventricular artery
• A small cardiac vein follows the right marginal artery
• Posterior vein of the left ventricle
• Oblique vein of the left atrium (vein of Marshal)
• Right marginal vein
• Anterior cardiac veins
• Venae cordis minimal (Thebesian veins/smallest cardiac veins)

The first 6 veins drain into the right atrium through the coronary sinus.

• The anterior cardiac veins drain directly into the right atrium.
• The venae cordis minimae (Thebesian veins) drain venous blood from the endocardium of all chambers of the heart and open directly into the cavity of the respective chambers.

Question 13. Write a short note on the coronary sinus.
Answer:

Coronary Sinus is a wide venous channel lying in the posterior part of the coronary sulcus between the base and the diaphragmatic surface of the heart. It opens into the posterior wall of the right atrium, left to the opening of the inferior vena cava.

Coronary sinus Tributaries

These are:

• Great cardiac vein
• Small cardiac vein
• Posterior vein of the left ventricle
• Oblique vein of the left atrium (vein of Marshall)
• Right marginal vein

Question 14. Enumerate the embryonic dilatations of the primitive heart tube and name the structures derived from each of them in a tabular form. 
Answer:

The primitive heart tube presents 5 dilatations. From cranial to caudal, these are:

• Truncus arteriosus
• Bulbus cordis
• Primitive ventricle
• Primitive atrium
• Sinus venosus

The derivatives from these dilatations are given in the box below:

Question 15. Write a short note on the dextrocardia. 
Answer:

In this condition, there is a transposition of heart chambers and associated blood vessels like a mirror image. As a result, heartbeat is felt in the right 5th intercostal space instead in the left 5th intercostal space. Dextrocardia is the most common positional anomaly of the heart.

Question 16. Describe the development of the interatrial septum in brief and discuss the congenital anomalies associated with it. 
Answer:

Development of interatrial septum:

• It develops in the 4th week of intrauterine life from the roof of the primitive atrial chamber.
• It develops from two sources: septum primum and septum secundum.
• The upper part of the interatrial septum is formed by the septum secundum and the lower part by the septum primum.

The details are as follows:

• Septum primum:
  • The septum primum is a sickle-shaped/crescent-shaped membrane that grows from the roof of the primitive atrium.
  • It runs downward to reach the atrioventricular cushion (septum intermedium) but falls short of it.
  • The gap between the septum primum and septum intermedium is called foramen (ostium primum).
  • Soon, it grows further and before it fuses with the septum intermedium; its upper part breaks open to form foramen secundum.
•  Septum secundum:
  • The septum secundum is also a crescentic membrane that arises from the roof of the primitive atrium, a little to the right of the origin of the septum primum.
  • It extends downward and overlaps the foramen secundum, but there remains a gap between the septum primum and septum secundum, which is oval in shape; it is called foramen ovale.
  • This foramen appears as an oblique cleft in profile view and allows the blood to pass from right atrium to the left atrium.

Congenital anomalies

Atrial septal defect (ASD): It is a common congenital anomaly that occurs in 0.07% cases and is 2 times more common in female infants.

Types They are of 4 types:

1. Ostium primum defect: In this, the septum primum fails to reach the atrioventricular cushion, or there is a defective formation of the atrioventricular cushion. As a result, foramen primum persists.
2. Ostium secundum defect: In this, the septum secundum fails to develop, or there is excessive resorption of the septum primum. As a result, a large opening exists between the two atria.
3. Cor trilocular biventricular: In this, there is a complete absence of interatrial septum. It is the most severe abnormality of the atrial septal defect and is always associated with other congenital defects of the heart.
4. Patent foramen ovale: In this, there is the failure of proper approximation of septum primum and septum secundum. It is clinically not significant because it does not allow shunting of the blood from right atrium to the left atrium. This defect is also sometimes called probe patency foramen ovale.

Question 17. Write a short note on the development of the interventricular septum and discuss the congenital anomalies associated with it. 
Answer:

Interventricular septum Development:

The interventricular septum develops in the 7th week of IUL. The interventricular septum consists of 3 parts. From below upward, these are: muscular part, membranous part, and bulbar part.

The three parts develop from 3 different sources:

1. Muscular part (major part) develops from the muscular ridge which grows upwards from the floor of primitive ventricle.
2. The membranous part develops from fused atrioventricular cushions.
3. Bulbar part develops from right and left bulbar septa, which is derived from right and left bulbar ridges.

Note: Clinically, both membranous and bulbar parts together are called the membranous part of the interventricular septum.

Congenital anomalies:

Ventricular Septal Defect

• It is the most common congenital anomaly of the heart. This defect commonly occurs in the membranous part, due to failure of fusion of the right and left bulbar ridges with the atrioventricular cushions.
• This leads to the flow of blood from left to right ventricle. As a result, the output from the left ventricle is reduced. Clinically, it presents as excessive fatigue on exertion.

Tetralogy of Fallot

This common congenital anomaly occurs due to unequal division of the conus, leading to the formation of a narrow pulmonary trunk and a wide ascending aorta.

As the name implies, this anomaly includes four cardiac anomalies as follows:

1. Pulmonary stenosis
2. Overriding of aorta
3. Ventricular septal defect
4. Right ventricular hypertrophy

Cardiac Anomalies Clinical Presentation

• Breathlessness on exertion
• Cyanosis

Note:

• Fallot’s tetralogy is the commonest congenital cyanotic heart disease. The child with this anomaly suddenly ceases his activity and assumes the knee-chest position and squatting posture.
• This is because by doing so he gets relief as squatting reduces the venous return by compressing the abdominal veins and increases the systemic vascular resistance by kinking the femoral and popliteal arteries.
• Both these mechanisms reduce the right to left shunting of blood through the ventricular septal defect and improve pulmonary circulation.

Question 18. Discuss the histological features of the cardiac muscle.
Answer:

Cardiac muscle

• The cardiac muscle is the muscle of the heart. It presents the following histological features. It consists of short cylindrical fibers, which branch and anastomose with each other.
• Each fiber contains a single centrally placed large nucleus. These fibers show faint transverse striations and are joined together by the surface specializations called intercalated discs, which appear as zigzag transverse lines.
• In some cells, a perinuclear space is seen.

Note: The conducting system of the heart is made up of specialized cardiac muscle fibers, which are thicker, larger, and contain few myofilaments. These fibers are present just deep to the endocardium.