Lecture 3: Thorax & Heart Anatomy: Mediastinum, Heart, Valves, Vessels, Fetal & Conduction

A comprehensive set of question-and-answer flashcards covering key concepts from the mediastinum, cardiac anatomy, heart valves, fetal circulation, conduction system, autonomic innervation, cardiac cycle, and coronary circulation.

Into how many parts is the mediastinum divided and what are they?

Two/Four parts – Superior, Inferior which subdivides into an anterior, middle, and posterior portion

What is common to all compartments of the mediastinum?

They all transmit structures passing from the head/neck into the thorax or abdomen.

What forms the anterior border of the superior mediastinum?

Posterior aspect of the manubrium.

What vertebral levels bound the posterior border of the superior mediastinum?

Anterior aspects of T1–T4 vertebral bodies.

Which landmark forms the inferior border of the superior mediastinum?

Line from the sternal angle to the T4–T5 intervertebral disc.

List the major veins found in the superior mediastinum.

Brachiocephalic veins and the superior vena cava.

Name the three primary branches of the aortic arch located in the superior mediastinum.

Brachiocephalic trunk, left common carotid artery, and left subclavian artery.

Which two ‘tubes’ pass through the superior mediastinum?

Trachea and esophagus.

What are the borders of the inferior mediastinum posteriorly and inferiorly?

Posterior: anterior aspects of T5–T12; Inferior: thoracic surface of the diaphragm.

What are the contents of the anterior (inferior) mediastinum?

Remnants of the thymus, lymph vessels, and fat.

Which structures are considered the “8 great vessels” of the middle mediastinum?

4 pulmonary veins, 1 pulmonary trunk, superior vena cava, inferior vena cava, and the aorta.

Name the three "water fowl" of the posterior mediastinum according to Dalley.

Azygoose (azygos vein), hemiazygoose (hemiazygos vein), and thoracic duck (thoracic duct).

What are the two layers of the heart?

Fibrous pericardium - external layer, and serous pericardium - internal layer

The fibrous pericardium acts as what?

A protective layer that holds the heart in place and prevents overfilling

What are the two layers of the serous pericardium?

Parietal layer and visceral layer

What is the pericardial cavity?

The space between the two layers of serous pericardium

Which valve is located between the right atrium and right ventricle?

Right atrioventricular (tricuspid) valve.

The right side of the heart is responsible for what?

Receiving venous (deoxygenated) blood from the body and delivering it to the lungs

What are the three parts that make up the right side of the heart?

Right atrium, right ventricle, and the pulmonary trunk

What is the left side of the heart responsible for?

Receiving oxygenated blood from the lungs and delivering it to the body (but not to the lungs)

What are the three parts that make up the left side of the heart?

Left atrium, left ventricle, and the aorta

How many leaflets does the tricuspid valve have and what are they called?

Three – septal, anterior, and posterior leaflets.

What does the right ventricle pump?

deoxygenated blood from pulmonary trunk to the lungs via the pulmonary arteries

What does the left atrium receive?

oxygenated blood from the lungs via the pulmonary veins

Which part of the heart forms a more defined apex?

The left ventricle

How many heart valves are there?

4 in total: 2 atrioventricular valves, 2 semilunar valves

Name the two atrioventricular valves

Right atrioventricular (tricuspid) valve and left atrioventricular (bicuspid/mitral) valve

Name the two semilunar valves

Pulmonary semilunar valve and aortic semilunar valve

What structures tether AV valve leaflets and prevent prolapse during systole?

Chordae tendineae attached to papillary muscles.

Which heart valve is the largest of the four

Right atrioventricular

Which valve prevents back-flow from the pulmonary trunk into the right ventricle?

Pulmonary semilunar valve.

During diastole, what causes semilunar valve leaflets to seal tightly?

Back-flow pressure of blood fills the valve pockets, pressing the leaflets together.

Which heart valve has two primary leaflets and is also called the bicuspid valve?

Left atrioventricular (mitral) valve.

Where are the openings of the coronary arteries located?

In the aortic sinuses just superior to the aortic valve leaflets.

Describe the fibrous pericardium’s attachments.

It adheres inferiorly to the diaphragm and superiorly to the roots of the great vessels.

What is Cardiac Tamponade?

Fluid accumulation in the pericardial cavity that limits heart expansion and impairs pumping.

What sound may indicate pericarditis on auscultation?

A pericardial friction rub (rustling sound).

Which fetal shunt enables blood to bypass the lungs by flowing from pulmonary trunk to aorta?

Ductus arteriosus.

What adult structure remains after closure of the ductus arteriosus?

Ligamentum arteriosum.

Which fetal opening allows blood to flow directly from right atrium to left atrium?

Foramen ovale.

After birth the foramen ovale becomes the _______.

Fossa ovalis.

What is the adult remnant of the umbilical vein?

Ligamentum teres (round ligament of the liver).

Name the pacemaker of the heart and its location.

Sinoatrial (SA) node; located in the right atrium near the SVC opening on the upper crista terminalis.

What happens each time the SA node depolarizes?

It causes a heart beat

What is the function of the atrioventricular (AV) node?

Delays the electrical impulse, allowing atrial contraction before ventricular depolarization.

Through which structure do impulses travel from AV node into the ventricles?

Atrioventricular bundle (Bundle of His) that splits into right and left bundle branches.

What fibers distribute electrical impulses throughout ventricular myocardium?

Purkinje fibers.

Define systole and diastole.

Systole – phase of heart contraction; Diastole – phase of heart relaxation and filling.

What is stroke volume and how is it calculated?

The volume of blood ejected per beat; Stroke Volume = End Diastolic Volume – End Systolic Volume.

Provide the formula for cardiac output.

Cardiac Output (CO) = Heart Rate (HR) × Stroke Volume (SV).

Why is the wall of the left ventricle thicker than that of the right ventricle?

It must generate higher pressure to eject blood into the systemic circulation via the aorta.

Which arteries supply the myocardium and from where do they branch?

Right and left coronary arteries; they are the first branches off the ascending aorta.

Which coronary artery gives rise to the left anterior descending (anterior interventricular) artery?

Left coronary artery.

What area does the circumflex branch of the left coronary artery primarily supply?

Left atrium and posterior part of the left ventricle.

Name the two main branches that arise from the right coronary artery.

Right marginal artery and posterior interventricular artery.

What type of blood do pulmonary arteries carry and why are their walls thick?

Deoxygenated blood under relatively high pressure causes thicker walls than pulmonary veins.

List the parasympathetic pathway to the heart.

Preganglionic fibers in the vagus nerve → cardiac plexus → postganglionic neurons in heart wall.

Which spinal levels carry visceral sensory fibers (pain) from the heart?

T1 to T6 via dorsal root ganglia.

During which part of the cardiac cycle do the coronary arteries receive most blood flow?

Early diastole (when aortic back-flow fills the valve pockets and enters the coronaries).

What is the ‘infundibulum’ in the right ventricle?

The smooth-walled outflow tract leading to the pulmonary valve.

Which internal ridge separates smooth from rough parts of the right atrium?

Crista terminalis.

What muscle forms the rough anterior wall of the atria?

Pectinate muscle.

Name the structure in the atria that is the fetal remnant of the foramen ovale.

Fossa ovalis on the interatrial septum.

Why can endurance training lower resting heart rate?

It increases stroke volume, so the heart needs fewer beats per minute to maintain cardiac output.

What makes up the cardiac “base”?

Primarily the posterior surface of the left atrium (with small right atrial contribution).

Which vessels return oxygenated blood to the left atrium?

Four pulmonary veins (two from each lung).