L2 Cardiac Structure

Question 1

Auricle

Answer 1

Appendages of atria. Embryonic remnants with no function. Can be sites of thrombotic formation.

Question 2

Ligamentum arteriosum

Answer 2

Remnant of fetal ductus arteriosusm – attaches aortic arch with pulmonary trunk

Question 3

Aortic knuckle

Answer 3

Aortic arch seen in PA xray

Question 4

Mediastinum - Location/boundaries

Answer 4

Between pleural sacs and within thoracic cavity.
Bound superiorly by the thoracic inlet (consists of T1, first pair of ribs, the costal cartilage of the first ribs and the superior border of the manubrium).
Bound inferiorly by the diaphragm.

Question 5

Mediastinum - Segment division

Answer 5

Divided into the superior/inferior mediastinum by a transverse plane passing from the manubriosternal joint to the inferior margin of T4.
The inferior mediastinum can be further subdivided into the middle, anterior (retrosternal space), and posterior (retrocardiac space) mediastinum.

Question 6

Superior mediastinum contains:

Answer 6

• Trachea, oesophagus, thymus.
• Aortic arch, brachiocephalic trunk, L. common carotid A., subclavian A.
• SVC, brachiocephalic Vs.
• Vagus N., recurrent laryngeal Ns, phrenic Ns, cardiac sympathetic Ns.

Question 7

Middle mediastinum contains:

Answer 7

• Heart and pericardium

* Roots of great vessels

Question 8

Anterior mediastinum contains:

Answer 8

• Super and inferior sternopericardial ligg (anchors heart to back of sternum), internal thoracic vessels, lymph nodes, thymus, fat.

Question 9

Posterior mediastinum contains:

Answer 9

• Oesophagus, descending aorta, trachea, bronchi, thoracic aorta, thoracic duct, azygous and hemiazygous Vs, vagus N., splanchnic Ns, lymph nodes.

Question 10

Pericardium (location, layers, function)

Answer 10

Encloses heart and roots of great vessels. Posterior to body of sternum and 2-6th costal cartilages; lies anterior to T5-T8.
Fibrous pericardium (tough CT outer layer)
- Attaches to roots of great vessels, back of sternum via sternopericardial ligs and central tendon of diaphragm
- Maintains position of heart (firmly anchored in centre of chest)
- Prevents over distension of heart.

Serous Pericardium (inner double membrane layer)

• Lubrication allowing free movement of heart within fibrous pericardium
• Parietal layer of serous pericardium (outer) is attached to fibrous layer
• Epicardium (inner visceral layer of serous pericardium) is attached to myocardium.
• Between parietal and epicardium is pericardial cavity which is filled with pericardia fluid (allowing free movement)

Question 11

Layers of heart wall

Answer 11

Epicardium
Myocardium
Endocardium

Question 12

Location of Heart

Answer 12

Middle mediastinum. T5-8 (or 6-9 when standing). Anterior to body of sternum (2-6th costal cartilages).

Question 13

Apex and Base

Answer 13

Apex: projects left and inferiorly. Positioned deep to the left 5th intercostal space 8-9cm from the midsternal line). Composed of the inferiolateral part of the left ventricle.

Base: quadrilateral surface where the great vessels enter and leave the heart. Composed of the left atrium and posterior part of the right atrium (and the proximal parts of the great veins).

Question 14

Surfaces

Answer 14

• Anterior (Sternocostal) – composed mainly of the right atrium and ventricle, with some contribution from the left ventricle and the auricle of the left atrium
• Inferior (diaphragmatic) – left and right ventricles
• Left (pulmonary) – left ventricle, with some contribution from the left atrium

Question 15

Borders

Answer 15

• Upper border – left and right atria
• Right border – right atrium
• Inferior border – right ventricle (with left ventricle at apex)
• Left border – left ventricle and left auricle

Question 16

Sulcus/Grooves

Also, what is coronary crux.

Answer 16

• Anterior and posterior interventricular sulci - between the left and right ventricles – interventricular arteries sit in this sulcus
• Coronary sulcus between the atria and ventricles (like a crown)– coronary arteries sit in this sulcus
• Posteriorly, an interatrial sulcus is visible
• Sulcus terminalis – external groove extending from the SVC to the IVC down the anterolateral aspect of the right atrium – corresponds to the crista terminalis internally

Coronary crux is where interatrial, coronary and interventricular sulcus meet.

Question 17

Internal structures - 4 Chambers
What vessels enter/exit/drain into what
Separation of RV and LV

Answer 17

RA - coronary sinus drains venous (deoxygenated) blood from myocardium into RA.
- IVC and SVC
LA - pulmonary veins
RV - pulmonary trunk/arteries
LV - aorta

RV and LV internally separated by interventricular septum. It has muscular (anteroinferior) and membranous (posterosuperior) parts. The membranous part lies towards the aortic valve and is partly confluent with the fibrous supports of the right and posterior cusps.

Question 18

Fossa ovalis

Answer 18

A depression on the septal wall of right atrium – remnant of embryonic foramen ovale. Lumbus of fossa ovalis = edge.

Question 19

3 branches off aortic arch

Answer 19

Brachiocephalic trunk
Left common carotid artery
Left subclavian artery

Question 20

Features of Right Atrium

Answer 20

Posteriorly, there is the sinus venarum, a smooth area where the S/IVC enter; it is smooth because tissues from the IVC and SVC are included. It is separated from the atrium proper by the crista terminalis.
Anteriorly, lining wall of atrium proper = musculi pectinate (muscular ridges – bands of muscle). Anterior to crista terminalis.
On the right lateral wall of the atrium, there is a muscular ridge (crista terminalis) which runs between the two caval openings and is continuous with the valve of the IVC. It separates the sinus venarum from the musculi pectinate.

Question 21

Features of Right Ventricle

Answer 21

The outflow tract is called the conus arteriosus (infundibulum) and extends towards the pulmonary semilunar valve.
The inflow and outflow tracts are separated by the supraventricular crest (muscular ridge).
Trabeculae caeneae are the ridges, bridges and papillary muscles that make up the internal surface of the RV.
The septomarginal trabecula (moderator band) (one of the trabeculae caenae), is a bridge than runs from interventricular septum across to the base of the anterior papillary muscle. It joins the septal wall to the base of the anterior papillary muscle.