Cardiovascular Anatomy

Question 1

What is the pathway of the phrenic nerves? And what are its features?

Answer 1

Right Phrenic Nerve
• Passes anteriorlyover the lateral part of the right subclavian artery.
• Enters the thorax via the superior thoracic aperture.
• Descends anteriorly along the right lung root.
• Courses along the pericardium of the right atrium of the heart.
• Pierces the diaphragm at the inferior vena cava opening.
• Innervates the inferior surface of the diaphragm.

Left Phrenic Nerve
• Passes anteriorly over the medial part of the left subclavian artery.
• Enters the thorax via the superior thoracic aperture.
• Descends anterior to the left lung root.
• Crosses the aortic arch and bypasses the vagus nerve.
• Courses along the pericardium of the left ventricle.
• Pierces and innervates the inferior surface of the diaphragm.

Thephrenic nerveis a mixed motor/sensorynervewhich originates from the C3-C5 spinalnervesin the neck. Thenerveis important for breathing because it provides exclusive motor control of the diaphragm, the primary muscle of respiration.

Spinal root C4 provides the main contribution, with lesser contributions fromC3andC5and some communicating fibres from thecervical plexus.

Thephrenic nerveis a bilateral,mixednerve that originates from the cervical nerves in the neck and descends through the thorax to innervate the diaphragm.
It is the only source of motor innervation to thediaphragmand therefore plays a crucial role in breathing.

Question 2

What innervation does the phrenic nerve provide to the diaphragm?

Answer 2

The phrenic nerves pass through the diaphragm and innervate it with both motor and sensory fibres from the abdominal surface.

Question 3

What nerve runs posterior to the phrenic nerve to the left of the aortic arch?

Answer 3

The left vagus nerve

Question 4

What is the pathway and function of the vagus nerve?

Answer 4

The vagus nerve passes behind the root of the lung to join the oesophagus which it follows into the abdomen. As the vagus passes over the aortic arch is divides to give off the left recurrent laryngeal nerve, this important branch can be seen passing under the ligamentum arteriosus

Towards the back of the right brachiocephalic vein, find the right vagus nerve and trace it running posterior to the root of the right lung

Thevagus nerveis the 10thcranial nerve (CN X).
It is a functionally diverse nerve, offering many different modalities of innervation. It is associated with the derivatives of the fourth and sixthpharyngeal arches.

• Sensory:Innervates the skin of the external acoustic meatus and the internal surfaces of the laryngopharynx and larynx. Provides visceral sensation to the heart and abdominal viscera.
• Special Sensory:Provides taste sensation to the epiglottis and root of the tongue.
• Motor:Provides motor innervation to the majority of the muscles of the pharynx, soft palate and larynx.
• Parasympathetic:Innervates the smooth muscle of the trachea, bronchi and gastro-intestinal tract and regulates heart rhythm.

In the thorax,the right vagus nerve forms theposterior vagal trunk, and the left forms theanterior vagal trunk.Branches from the vagal trunks contribute to the formation of the oesophageal plexus, which innervates the smooth muscle of the oesophagus.
Two other branches arise in the thorax:
• Left recurrent laryngeal nerve– ithooks under the arch of the aorta, ascending to innervate the majority of the intrinsic muscles of the larynx.
• Cardiac branches– these innervate regulate heart rate and provide visceral sensation to the organ.
The vagal trunks enter the abdomen via the oesophageal hiatus, an opening in the diaphragm.

Question 5

What are the three branches from the aortic arch?

Answer 5

the brachiocephalic trunk (branching to right common carotid and subclavian vessels), the left common carotid and left subclavian arteries

Question 6

Describe the pericardium?

Answer 6

• The inner surface of the pericardium has a smooth lining, the parietal pericardium. This serous pericardium lines the entire pericardial cavity; where it covers the fibrous pericardium it is the parietal pericardium and where it covers the blood vessels and the heart it is the visceral pericardium.
• This is exactly the same as the parietal and visceral pleura on the chest wall and lungs.
• All the veins entering the heart also pass through the pericardium together and the gap between the arteries and veins is the transverse sinus of the pericardium

Question 7

What would be the effect of a tumour on the left recurrent laryngeal nerve?

Answer 7

A tumour of the left lung can invade the left recurrent laryngeal nerve and cause paralysis of the muscles of the left vocal cords leading to a hoarse voice

Question 8

What is the result of painful stimulation of the diaphragm?

Answer 8

• Any painful stimulation of the diaphragm would be detected by the phrenic nerve. The phrenic nerve passes into the spinal cord through the cervical 3, 4 and 5 nerve roots. Painful sensory input in these nerve roots are felt by the patient in the skin supplied by these roots, the cervical 3, 4 and 5 dermatomes. Therefore, painful stimulation of the diaphragm is felt in the side of the neck and the shoulder, typically in the ‘shoulder tip’

Question 9

What is cardiac tamponade?

Answer 9

\the pericardium is a tough fibrous sac which will only distend over a prolonged period of time. Any pathology which causes fluid to collect in the pericardium will limit ventricular filling (the end diastolic volume) and will reduce the cardiac output. This is called cardiac tamponade

Question 10

What are the four sections of the aorta?

Answer 10

The ascending aorta, the aortic arch, the thoracic (descending) aorta, and the abdominal aorta

Question 11

Describe the ascending aorta?

Answer 11

The ascending aorta arises from theaortic orificefrom the left ventricle and ascends to become the aortic arch. It is 2 inches long in length and travels with the pulmonary trunk in the pericardial sheath.

Question 12

What are the branches of the ascending aorta?

Answer 12

The left and right aorticsinuses are dilations in the ascending aorta, located at the level of the aortic valve.Theygive rise to theleft and right coronary arteriesthat supply the myocardium.

Question 13

What level does the aortic arch start?

Answer 13

begins at the level of the second sternocostal joint. It arches superiorly, posteriorly and to the left before movinginferiorly.
The aortic arch ends at the level of the T4 vertebra. The arch is still connected to the pulmonary trunk by theligamentum arteriosum(remnant of the foetal ductus arteriosus).

Question 14

Describe the structure and pathway of the superior vena cava?

Answer 14

Thesuperior vena cava(SVC) is a large, valveless vein that conveys venous blood from the upper half of the body and returns it to the right atrium.

Thesuperior vena cavais classified as a large vein, with a wide diameter of up to 2cm and a length of approximately 7cm.
It arises from the union of theleftandright brachiocephalic veins, posterior to the first right costal cartilage. It descends vertically through the superior mediastinum, behind the intercostal spaces and to the right of the aorta and trachea.
At the level of the second costal cartilage, the SVC enters themiddle mediastinumand becomes surrounded by the fibrous pericardium. It terminates by emptying into the superior aspect of the right atrium at the level of the third costal cartilage.

At the level of T4, the superior vena cava receives the azygous vein, which drains the upper lumbar region and thoracic wall.
The SVC receives tributaries from several minor vein groups:
• Mediastinal veins
• Oesophageal veins
• Pericardial veins

Question 15

What are the surface markings for the heart borders?

Answer 15

Superior: inferior border of the second left costal cartilage–> superior border of the third right costal cartilage
Right: third right costal cartilage–> sixth right costal cartilage
Inferior: Sixth right costal cartilage–> fifth left intercostal space at the midclavicular line
Left: Fifth left intercostal space at the midclavicular line–> inferior border of the second left costal cartilage

Question 16

What the surface markings for the heart valve projections?

Answer 16

Mitral valve- Posteriorly to the left side of the sternum at the level of the left fourth costal cartilage
Tricuspid valve- Posteriorly to the right side of the sternum at the elvel of the right fourth costal cartilage
Aortic valve- posteriorly to the left side of the sternum at the level of the third intercostal space
Pulmonary valve- At the junction of sternum and left third costal cartilage

Question 17

Heart ascultation points?

Answer 17

Mitral valve- The left fifth intercostal space at the midclavicular line
Tricuspid valve- Left fifth intercostal space, parasternally
Aortic valve- Right second intercostal space, parasternally
Pulmonary valve- left second intercostal space, parasternally

Question 18

What are some key valve clinical points?

Answer 18

Aortic stenosis, aortic regurgitation, mitral stenosis, mitral regurgitation

Question 19

What structure lies between the right atrium and the right ventricle and what does it contain?

Answer 19

right atrioventricular sulcus (sulcus=Latin for furrow). The sulcus contains fat and the right coronary artery and is often called the right coronary sulcus.

Question 20

Where does the right coronary artery run?

Answer 20

right coronary artery runs in the right atrioventricular groove and gives off a branch which often runs along the margin of the ventricle, the marginal branch and then continues onto the diaphragmatic surface of the heart where it turns to run in the interventricular groove in 90 % of hearts, the posterior inter-ventricular branch.

Question 21

What would be found in the left atrioventricular sulcus and what are the branches?

Answer 21

left atrioventricular sulcus to reveal the left coronary artery and follow its branches including the left anterior descending, circumflex, obtuse marginal and diagonals.

Question 22

What is the main venous drainage from the heart and where does it run?

Answer 22

the coronary sinus, this is the major venous drainage of the heart muscle. Follow the coronary sinus round to the posterior aspect of the heart where it drains into the right atrium next to the inferior vena cava.

It is found in the left coronary sulcus

Question 23

What is interesting about the posterior interventricular artery and what are the percentages?

Answer 23

posterior interventricular artery arises from the right coronary (90% of hearts) or from the circumflex branch of the left coronary artery (30% of hearts). In 20% of hearts there are two posterior interventricular arteries one from the right and one from the left coronary artery

Question 24

What is the crista termanalis and what lies within?

Answer 24

a ridge of modified heart muscle which separates the trabeculated auricle from the smooth walled atrium; part of the conducting pathway, the sinoatrial node, is in the upper half of the crista terminalis.

Question 25

What are the musculi pectinati?

Answer 25

They cover the inside of the auricular appendage

Question 26

Why is the right atrium wall smooth?

Answer 26

in embryology, it developed from a blood vessel

Question 27

What is the fossa ovalis?

Answer 27

It is an embryological remnant from the foramen ovalis which shunted blood from the right atrium to the left thus bypassing the pulmonary circulation

Question 28

Where is the tricuspid valve?

Answer 28

In the right atrioventricular orifice

Question 29

Where is the bundle of His?

Answer 29

In the septomarginal trabeculum at the apex of the ventricle, the ‘Bundle of His’ runs across the lumen of the right ventricle.

Question 30

Describe the internal structure of the right ventricle?

Answer 30

Note the nature and distribution of the trabeculae carneae in the cavity of the ventricle and that the cavity becomes smooth approaching the pulmonary valve, this is the infundibulum of the ventricle

Question 31

In what percentage of adults is their patency between the atrial chambers?

Answer 31

region of the fossa ovalis for any patency between the atrial chambers (present in 23% of adults).

Question 32

What is the structure of the mitral valve?

Answer 32

it has two cusps and the same arrangement of cordae tendineae and papillary muscles as the tricuspid valve.

Question 33

What would be the result of papillary muscle death?

Answer 33

Valve failure in the affected valve

Question 34

What are the two regions of the right atrium and what separates them?

Answer 34

• Sinus venarum– located posteriorto thecrista terminalis. This part receives blood from the superior and inferior vena cavae. It has smooth walls and is derived from the embryonic sinus venosus.
• Atrium proper– located anterior to the crista terminalis, and includes the right auricle.It is derived from the primitive atrium, andhas rough, muscular walls formed by pectinate muscles.
Thecoronary sinusreceives blood from the coronary veins. It opens into the right atrium between the inferior vena cava orifice and the right atrioventricular orifice.

They are separated by the crista terminalis

Question 35

What are the two portions of the left atrium?

Answer 35

• Inflow portion– receives blood from the pulmonary veins. Its internal surface is smooth and it is derived from the pulmonary veins themselves.
• Outflow portion– located anteriorly, and includes the left auricle. It is lined bypectinate muscles, and is derived from the embryonic atrium.

Question 36

What are the two portions of the right ventricle and what separates them?

Answer 36

The right ventricle can be divided into an inflow and outflow portion, which are separated by a muscular ridge known as thesupraventricular crest.

The interior of the inflow part of the right ventricle is covered by a series of irregular muscular elevations, calledtrabeculae carnae. They give the ventricle a ‘sponge-like’ appearance, and can be grouped into three main types:
• Ridges– attached along their entire length on one side to form ridges along the interior surface of the ventricle.
• Bridges– attached to the ventricle at both ends, but freein the middle. The most important example of this type is the moderator band, which spansbetween the interventricular septum and the anterior wall of the right ventricle.It has an important conductive function, containing the right bundle branches.
• Pillars(papillary muscles)– anchoredby their base to the ventricles. Their apices are attached tofibrous cords (chordae tendineae),which are in turn attached to the threetricuspid valvecusps. By contracting, the papillary muscles ‘pull’ on the chordae tendineae to prevent prolapseof the valve leaflets during ventricular systole.

Outflow Portion (Conus arteriosus)
The outflow portion(leading to the pulmonary artery) is located in the superior aspect of the ventricle. Itis derived from the embryonicbulbuscordis. It is visibly different from the rest of the right ventricle, with smooth walls and no trabeculae carneae.

Question 37

What are the two portions of the left ventricle?

Answer 37

Inflow Portion
The walls of the inflow portion of the left ventricle are lined bytrabeculae carneae, as described with the right ventricle. There are two papillary muscles present which attach to the cusps of the mitral valve.
Outflow Portion
The outflow part of the left ventricle is known as theaortic vestibule. It is smooth-walled with no trabeculae carneae, and is a derivative of the embryonicbulbus cordis.

Question 38

How many papillary muscles in total and what is their division?

Answer 38

5 in total

3 in right ventricle

2 in left ventricle

Question 39

What are the cusps of the pulmonary valve?

Answer 39

left, right andanterior

Question 40

What are the cusps of the aortic valve?

Answer 40

right, leftandposterior

Question 41

What are the tributaries that drain into the coronary sinus from the heart?

Answer 41

There arefive tributarieswhich drain into the coronary sinus:
• Thegreat cardiac veinis the main tributary. It originates at the apex of the heart and follows the anterior interventricular groove into the coronary sulcus and around the left side of the heart to join the coronary sinus.
• Thesmall cardiac veinis also located on the anterior surface of the heart. This passes around the right side of the heart to join the coronary sinus.

• Another vein which drains the right side of the heart is themiddle cardiac vein.It islocated on the posterior surface of the heart.
The final 2 cardiac veins are also on the posterior surface of the heart:
• On the left posterior side is theleft marginal vein.
• In the centre is theleft posterior ventricular veinwhich runs along the posterior interventricular sulcus to join the coronary sinus.

Question 42

What are the divisions of the mediastinum?

Answer 42

Superior, Inferior (subdivided to Anterior, middle, posterior)

Question 43

What are the borders of the superior mediastinum?

Answer 43

• Superior– Thoracic inlet.
• Inferior– Continuous with the inferior mediastinum at the level of the sternal angle.
• Anterior– Manubrium of the sternum.
• Posterior– Vertebral bodies of T1-4.
• Lateral– Pleurae of the lungs.

Question 44

What blood vessels arise in the superior mediastinum?

Answer 44

Arch of Aorta
The three major branches ofthe aortic arch arise within the superior mediastinum:
• Brachiocephalic artery– supplying the right side of the head & neck and the right upper limb.
• Left Common carotid artery– to the left side of the head & neck.
• Left Subclavian artery– to the left upper limb.
Superior Vena Cava
The following tributaries of the superior vena cava are located within the superior mediastinum:
• Brachiocephalic veins– draining blood from the upper body.
• Left superior intercostal vein– collectsblood from the left 2nd and 3rd intercostal vein. It drains into the left brachiocephalic vein.
• Supreme intercostal vein– drains the vein from first intercostal space directly into the brachiocephalic veins.
• Azygos vein– receiving blood from the right posterior intercostal veins. The left intercostal veins drain first into the hemiazygos and accessory hemiazygos veins before joining the azygos vein around T7-T9.

Question 45

What is the path of the vagus nerve in the superior mediastinum?

Answer 45

In the superior mediastinum, the vagus nerve has two distinctive paths:
• Right vagus nerve– runs parallel to the trachea and passes posteriorly to the superior vena cava and the right primary bronchus.
• Left vagus nerve (Fig 3)– enters the superior mediastinum between the left common carotid and the left subclavian arteries. It descends anteriorly to the aortic arch, before travellingposterior tothe leftbronchus.
The left recurrent laryngeal nervearises from the left vagus nerve as it passes the aortic arch. It loops under the arch, to the left ofligamentum arteriosum, before continuing its journey to the larynx in the tracheal-oesophageal groove.

Question 46

What nervous structures other than the vagus nerve are present in the superior mediastinum?

Answer 46

From the anterior surface of theanterior scalenemuscle, the phrenic nerves (roots C3, C4 and C5) enter the superior mediastinum lateral to the great vessels. They then descend anteriorly into the middle mediastinum, passing anteriorly to thehilumof the lungs.

• Cardiac nerves– originate from the superior, middle and inferior cardiac ganglion and form thesuperficial and deep cardiac plexusesin the superior mediastinum. The superior plexus sits between the aortic arch and right pulmonary artery. The deep plexus lies on the surface of the trachea at the point of bifurcation.
• Sympathetic trunk–runs bilaterally to the vertebral bodies along the entire length of the vertebral column.

Question 47

What are the borders of the anterior mediastinum?

Answer 47

• Lateral borders:Mediastinal pleura (part of the parietal pleural membrane).
• Anterior border: Body of the sternum and the transversus thoracis muscles.
• Posterior border: Pericardium.
• Roof: Continuous with the superior mediastinum at the level of the sternal angle.
Floor: Diaphragm

Question 48

What does the anterior mediastinum contain?

Answer 48

The anterior mediastinum contains no major structures. It accommodates loose connective tissue (including thesternopericardial ligaments, which tether the pericardium to the sternum), fat, some lymphatic vessels, lymph nodes and branches of the internal thoracic vessels.
In infants and children, thethymusextends inferiorly into the anterior mediastinum. However the thymus recedes during puberty and is mostly replaced by adipose tissue in the adult.

Question 49

What are the borders of the middle mediastinum?

Answer 49

• Anterior: Anterior margin of the pericardium.
• Posterior: Posterior border of the pericardium.
• Laterally: Mediastinal pleura of the lungs.
• Superiorly: Imaginary line extending betweenthe sternal angle (the angle formed by the junction of the sternal body and manubrium) and the T4 vertebrae.
• Inferiorly: Superior surface of the diaphragm.

Question 50

What is contained in the middle mediastinum?

Answer 50

Organs
The middle mediastinum contains theheart, and its protective sheath, thepericardium. It also contains thetracheal bifurcationand the left and right main bronchi.
Vessels
The middle mediastinum is associated with the origins of thegreat vesselsthat run to and from the heart:
• Ascending aorta–the first part of the aorta, which arises from theaortic orifice. It moves upwards, exiting thefibrous pericardium and entering thesuperior mediastinum – where itthen becomes the aortic arch. The ascending aorta gives rise to two branches; the left and right coronary arteries.
• Pulmonary trunk–gives rise to theleft and right pulmonary arteries. The trunk itself is relatively short and wide, allowinga large volume of blood to pass through it.
• Superior vena cava– returns deoxygenated blood from the upper half of the body. It is formed by the right and left brachiocephalic veins.

The cardiac plexus and the phrenic nerves are both located within the middle mediastinum.
• Cardiac plexus–a networkof nerves located at the base of the heart, containing sympathetic and parasympathetic fibres. The sympathetic nerves are derived from the T1-T4 segments of the spinal cord, and the parasympathetic innervation is supplied by the vagus nerve.The plexus can be subdivided into superficial and deep components.
• Phrenic nerves(left and right)–mixednerves thatprovides motor innervation to the diaphragm. They arise in the neck, and descendthrough the middle mediastinum to reach the diaphragm.

Thetracheobronchiallymph nodesare located within the middle mediastinum. They are a group of nodes associated with the trachea and bronchi of the respiratory tract – and are characteristically enlarged in certain lung pathologies. They form from the gathering of bronchial nodes within thehilaof the lungs. Individual groups of nodes are connected via fine lymphatic channels.

Question 51

What are the borders of the posterior mediastinum?

Answer 51

• Lateral: Mediastinal pleura (part of the parietal pleural membrane).
• Anterior: Pericardium.
• Posterior: T5-T12 vertebrae.
• Roof: Imaginary line extending betweenthe sternal angle (the angle formed by the junction of the sternal body and manubrium) and the T4 vertebrae.
• Floor: Diaphragm.

Question 52

What are the layers of heart wall?

Answer 52

Endocardium, Myocardium, Pericardium, Epicardium

Question 53

What are the physiological functions of the pericardium?

Answer 53

• Fixes the heartin the mediastinum and limits its motion. Fixation of the heart is possible because the pericardium is attached to the diaphragm, the sternum, and the tunica adventitia (outer layer) of the great vessels
• Prevents overfillingof the heart. The relatively inextensible fibrous layer of the pericardium prevents the heart from increasing in size too rapidly, thus placing a physical limit on the potential size of the organ
• Lubrication. A thin film of fluid between the two layers of the serous pericardium reduces the friction generated by the heart as it moves within the thoracic cavity
Protection from infection. The fibrous pericardium serves as a physical barrier between the muscular body of the heart and adjacent organs prone to infection, such as the lungs.

Question 54

What is the cardio-thoracic ratio?

Answer 54

Cardio-thoracic ratio is a measure of heart size and can be used to investigate various pathologies such as heart failure. It is calculated by measuring the widest part of heart and dividing this by the widest part of lung fields. A value of less than 55% is normal.

Question 55

What is the origin, course, function, and clinical notes for the phrenic nerve?

Answer 55

Origin: Spinal Nerves C3, C4 & C5

Course: Descends between the Subclavian Artery and Vein, then anterior to the hila of the lungs along the lateral aspects of the pericardium bilaterally.

Function: Motor supply to the diaphragm, Sensory supply to the fibrous pericardium and diaphragmatic surfaces of the parietal pleura and peritoneum.

Clinical Notes: When pain is felt in the structures that the Phrenic Nerve provides sensation to, it is often referred to the shoulder because that is the area of the skininnervated by the C3-C5 dermatomes. E.g. a right-sided Subphrenic Abscess may cause referred pain in the right shoulder tip.

Question 56

What is the origin, course, and functionfor the Vagus Nerve?

Answer 56

Origin: Medulla Oblongata (as Cranial Nerve X)

Course:After leaving the skull, descends between the Common Carotid Artery and Internal Jugular Vein, then posterior to the hila of the lungs before entering the
abdomen alongside the oesophagus.

Function:
• Parasympathetic supply to the thoracic and abdominal organs.
• Sensory and motor supply to the larynx and some other head & neck structures.

Question 57

Describe the three great vessels?

Answer 57

Arch of Aorta Gives off 3 main arteries (Brachiocephalic Artery, Left Common Carotid & Left Subclavian) superiorly before continuing inferiorly as the descending aorta.

Superior Vena Cava
• Formed by the merging of the Left and Right Brachiocephalic veins.
• Azygous vein also drains into SVC.

Brachiocephalic Veins
• Formed by the merging of the Internal Jugular and Subclavian veins.
• Inferior Thyroid veins also drain directly into Brachiocephalic veins.

Question 58

Describe the coronary arteries?

Answer 58

Left Anterior Descending(LAD):
• Branch of left main coronary artery, runs anteriorly between the two ventricles.
• Main branches of the LAD are the Diagonal arteries.

Left Circumflex (LCX):
• Branch of left main coronary artery, runs around the left side of the heart,
between the left atrium and left ventricle.
• Main branch of the LCX is the Obtuse Marginal artery.

Right Coronary (RCA):
• Runs around the right side of the heart, between the right atrium and right
ventricle.
• Main branch of the RCA is the Marginal artery.
• It is the most common artery to supply the SA node.

Posterior Descending Artery (PDA):
• Also known as the ‘Posterior Interventricular Artery’.
• Runs posteriorly between the two ventricles.
• Most often, it’s the terminal branch of the Right Coronary artery, but it can
also be the terminal branch of the Left Circumflex instead and sometimes,
both RCA and LCX supply the PDA.
• The PDA supplies the AV node.

Question 59

Describe Chordae Tendinae and Papillary Muscles?

Answer 59

Chordae Tendineae:
• Look like parachute cords.
• Connect the papillary muscles to the Tricuspid and Mitral valve leaflets.

Papillary Muscles:
• Located on the internal ventricular wall.
• Contract to pull on the Chordae Tendineae (and the therefore on the valve leaflets) to prevent valvular regurgitation during ventricular systole.

Question 60

Describe the five key anatomical features of the internal heart?

Answer 60

Fossa Ovalis:
• Remnant of the ‘Foramen Ovale’, which was a hole in the atrial septum that allowed blood to bypass the lungs in the foetus by moving from the right
atrium directly into the left atrium. It closed shortly after birth.
• In adults, it is an oval-shaped indentation in the atrial septum.

Crista Terminalis:

• A small ridge seen from inside the right atrium, near to where the SVC
meets the atrium, and where the atrium meets the atrial appendage.
• It represents the location of the SA node.
• Externally, it is a small groove, called the Sulcus Terminalis.

Pectinate Muscles:
• Muscular wall of the atrial appendages, trabeculated pattern.
• Not seen in the atrium, as walls are smooth in the atrium.

Trabeculae Carneae:
• Trabeculated pattern of the muscular wall of the ventricles.

Moderator Band:
• Muscular band that looks a bit like a papillary muscle, that extends from the septal wall of the right ventricle to the lateral wall of the right ventricle internally.
• Carries part of the right bundle branch to create an electrical shortcut allowing effective contraction of the right ventricle.
• Not found in the left ventricle.

Question 61

What is the ligamentum arteriosum?

Answer 61

Remnant of the ‘Ductus Arteriosus’, which was a passage that allowed blood to bypass the lungs in the foetus by shunting blood from the Pulmonary Trunk to the Aorta.
• Closes shortly after birth and it resembles a ligament in adults.

Question 62

What is the coronary sinus?

Answer 62

• Large ‘vein’ on the back of the heart.

* All cardiac veins drain into this, and then the coronary sinus drains blood into the right atrium

Question 63

Describe pericardium?

Answer 63

Not stretchy.
• If fluid or blood accumulates inside (between the heart and the pericardium), it can compress the heart and restrict ventricular filling.
• This is called Cardiac Tamponade.