Cardiovascular anatomy Flashcards
Describe the mediastinum…
Part of the thoracic cavity that lies between the lungs. It contains all thoracic viscera except for the lungs.
What are the boundaries of the mediastinum?
Superior: superior thoracic aperture
Inferior: diaphragm
Anterior: sternum
Posterior: thoracic vertebrae
What does the mediastinum contain:
Heart and pericardium
The great vessels
Veins that drain chest
Trachea and main bronchi
Oesophagus
Nerves
Lymphatics
Thymus gland
Where does the superior and inferior mediastinum meet?
The line runs in the sternal angle anteriorly to the t4/t5 junction posteriorly. This line intersects the point at which the trachea bifurcates and the start and end of the aortic arch.
What are the subdivisions of the inferior mediastinum?
The anterior, middle and posterior mediastinum.
Describe the anterior mediastinum and its constituents…
Lies between the posterior aspect of the sternum and the anterior aspect of the pericardial sac.
A narrow space containing the thymus gland in children and its remnants in adults
Describe the middle mediastinum constituents…
Contains the heart inside the pericardial sac, the pulmonary trunk and the ascending aorta.
Describe the posterior mediastinum…
Lies between the posterior aspect of the pericardial sac and the vertebrae
What are the main continents of the superior mediastinum?
Arch of aorta
Superior vena cava
Trachea
Oesophagus
Phrenic nerves
Thoracic duct
Thymus gland
Describe the 3 parts of the aorta…
The ascending aorta - gives rise to the coronary arteries that supply the myocardium
Arch of the aorta
The descending aorta
What does the arch of the aorta contain?
Aortic bodies containing chemoreceptors which monitor arterial oxygen and carbon dioxide
What are the 3 branches of the arch of the aorta and what do they supply?
The brachiocephalic trunk - the right head, neck and upper limb
The left common carotid - left Side of the head and neck
Left subclavian artery - supplies the left upper limb
What does the brachiocephalic trunk bifurcates into?
Right subclavian - supplies the right upper limb
Right common carotid - supplies the right side of the head and neck
What is the ligamentum arteriosum?
A fibrous cord like connection between the pulmonary trunk and the arch of the aorta. It is the remnant of the ductus arteriosus
What is the ductus arteriosus and what is its function?
It is a foetal circulatory shunt
In a foetus, gas exchange occurs at the placenta and the ductus arteriosus diverts much of the blood entering the pulmonary trunk directly into aortic arch.
When a baby starts to use their lungs at birth, the ductus arteriosus closes and the blood from pulmonary trunk enters the lungs.
What is the function of the superior vena cava?
Returns blood to the heart (right atrium) from the head, neck and the upper limbs.
What is the function of the inferior vena cava?
Returns blood to the heart (right atrium) from all regions inferior to the diaphragm.
Describe the superior vena cava tributaries…
Superior vena cava splits into the right and left brachiocephalic veins.
Each brachiocephalic vein is made up of the corresponding side internal jugular vein and the subclavian vein.
What is the function of the trachea?
Conducts air to and from the left and right main bronchi.
Why is the trachea semi-rigid?
Due to being c-shaped and incomplete rings of cartilage in its walls.
Where is the trachea palpable?
Just superior to the suprasternal notch.
Where does the trachea terminate?
At the level of the sternal angle and junction between the T4 and T5 vertebrae by bifurcating into the left and right main bronchi.
Where does the trachea extend from?
The larynx in the midline of the neck into the superior mediastinum
Describe the oesophagus…
A muscular tube extending from the pharynx in the midline of the neck to the stomach.
What is posterior to the trachea?
Oesophagus
What are the left and right phrenic nerves formed by?
Fibres from the C3, C4, C5 spinal nerves.
Describe phrenic nerves…
Somatic nerves containing motor and sensory fibres.
Formed by fibres from C3, C4, C5 spinal nerves.
The descend through the neck and enter the thorax through the superior thoracic aperture and pierce the diaphragm.
What do the phrenic nerves innervate?
Motor innervation to the diaphragm
What do the vagus nerves innervate?
Structures of the thorax, and abdomen in addition to the head and neck.
Describe the vagus nerves…
The left and right vagus nerves arise from the brainstem and contain somatic sensory and motor and parasympathetic fibres.
What do the vagus nerves give rise to and why?
To a recurrent laryngeal nerve which ascend back upto the neck to innervate the muscles of the larynx apart from the cricothyroid muscle
The left and right recurrent laryngeal nerves descend…
The left recurrent laryngeal nerve loops under the arch of the aorta before descending back up the left side of the neck to the larynx.
The right recurrent laryngeal nerve descends anterior to the right subclavian artery then loops under the inferior border of the artery before ascending back up the right side of the neck to the larynx.
What is the thoracic duct important for?
lymphatic drainage
Describe the thoracic duct…
Ascends through the posterior mediastinum into the superior mediastinum where it empties into the venous system.
Describe the thymus gland…
A lymphoid organ lying anteriorly in the superior mediastinum.
Why is the pericardium loose?
To allow for the movement of the heart within it.
Describe the 2 layers of the pericardium:
A tough outer fibrous layer attached superiorly to the great vessels and inferiorly to the central tendon of the diaphragm
A thin serous layer split into the parietal and visceral layer. The visceral layer is the outer layer.
Describe the pericardial cavity…
A narrow space between the 2 layers of the serous pericardium.
It contains a small amount of pericardial fluid which lubricates the serous membranes and allows them to slide over each other for movement of the heart.
What innervates the fibrous pericardium?
The left and right phrenic nerves give rise to sensory branches which innervate the fibrous pericardium.
What are the surfaces of the heart?
Base: Posterior surface
Inferior: Diaphragmatic surface
Anterior: Sternocostal surface
Pulmonary surfaces
Where does the apex lie?
At the left 5th intercostal space in the midclavicular line and the apex beat is palpable here.
What are the surface landmarks of the right border of the heart?
Lies lateral to the right sternal edge from the right 3rd costal cartilage to the right 6th costal cartilage
What are the surface landmarks of the left border of the heart?
Extends from the left 2nd intercostal space to the left 5th intercostal space in the midclavicular line
What are the surface landmarks of the superior border of the heart?
Lies along the line connecting the superior extends of the right and left borders (from the right 3rd costal cartilage to the left 2nd intercostal space)
What are the surface landmarks of the inferior border of the heart?
Lies along the line connecting the inferior end of the right border with the apex. (mostly formed by the right ventricle)
What are auricles?
Outpoutchings from the walls of the right and left atria.
What does the right coronary artery supply?
the right atrium, right ventricle, parts of the left ventricle and part of the inter-ventricular septum.
What are the branches of the right coronary artery?
Branches to the sinoatrial node and atrioventricular node
Right marginal artery supplies the inferior border of the heart
Posterior inter- ventricular artery : a continuation of the right coronary artery on the inferior surface of the heart. It supplies both ventricles
What are the branches of the left coronary artery?
Anterior inter-ventricular artery: runs in the anterior inter-ventricular sulcus towards the apex and supplies both ventricles
One or 2 diagonal branches from the anterior inter-ventricular artery
Circumflex artery runs around the heart onto the diaphragmatic surface, supplying the left atrium, part of the right ventricle and the left ventricle.
Marginal artery arises from the circumflex and supplies the left ventricle.
What does the left coronary artery supply?
The left atrium
Most of left ventricle
Part of right ventricle
Part of the inter ventricular septum.
What are the 2 large terminal branches of the left coronary artery?
Anterior inter-ventricular artery
Circumflex artery
Where does the posterior inter ventricular artery originate from and what does this determine?
May arise from either left or right coronary artery.
It determines if an individual has a right or left dominant coronary circulation.
What does it mean if a person has right dominant circulation?
The posterior inter ventricular artery arises from the right coronary artery. Both the right and left coronary arteries supply the left ventricle.
What does it mean if a person has left dominant circulation?
The posterior inter ventricular artery arises from the circumflex artery. The left coronary artery supplies the entire left ventricle
Why is dominant circulation important in clinical practice?
Right dominant circulation: blockage to the left main stem would impair blood flow to only part of the left ventricle
Left dominant circulation: blockage of the left main stem would block blood flow to the entire left ventricle.
What are the 3 areas the right atrium receives deoxygenated blood?
Superior vena cava
Inferior vena cava
Coronary sinus - blood from the heart
What are the main internal features of the right atrium?
Interatrial septum - separates it from left atrium
Fossa ovalis - depression in the interatrial septum and a remnant of the foramen ovale.
Crista terminalis - muscular ridge separating the smooth posterior atrial wall from the anterior part.
Pectinate muscles
What is the function of the foramen ovale in foetal circulation?
Shuts oxygenated blood from the right atrium to the left atrium hence, bypassing the lungs.
What are the internal features of the right ventricle?
Interventricular septum - separating it from the left ventricle
Trabeculae carneae - muscular ridges on the internal wall
Papillary muscles - regions of the trabeculae carneae that project into the lumen of the ventricle.
Chordae tendineae - fibrous cords which connect the tips of the papillary muscles to the tricuspid valve.
Moderator band- modified region of the trabeculae carneae connecting the inter ventricular septum to the of the papillary muscles.
What are the internal structures of the left ventricle?
Trabeculae carneae -muscular ridges on the internal wall
Papillary muscles - 2 in the left ventricle
Chordae tendineae - connect the tips of the papillary muscles to the mitral valve.
Why are the papillary muscles and chordae tendineae important?
Important for normal functioning of the atrioventricular valves.
How does the papillary muscles work on the atrioventricular valves?
When the ventricles contract, the papillary muscles also contract and they tense the cords which pull on the valve cusps and prevent them entering the atria.
When do the coronary arteries fill?
During ventricular relaxation (diastole).
What do the right and left coronary arteries arise from?
2 or 3 of the aortic sinuses.
Where is the aortic valve auscultatory area?
2nd intercostal space, just to the right of then sternum
Where is the pulmonary valve auscultatory area?
2nd intercostal space, just to the left of the sternum.
Where is the tricuspid valve auscultatory area?
5th intercostal space, just to the left of the sternum
Where is the mitral valve auscultatory area?
5th intercostal space, left midclavicular line.
What is the rate of the SAN?
70 per minute
Where is the SAN located?
The superior end of the crista terminalis.
What is the anatomical variation of the SAN?
Supplied by RCA in 60% of people
Supplied by LCA in 40% of people.
What is the anatomical variation of the AVN?
The AVN is supplied by the posterior inter-ventricular artery which arises from the RCA in most people
Which artery supplies the bundle of His in most people?
The left coronary artery
How can conduction abnormalities or myocardial ischaemia occur?
The blockage of coronary arteries can cause conduction issues as these supply the SAN and AVN.
What fibres is the heart innervated by?
Sympathetic, parasympathetic and visceral afferent fibres.
Describe the sympathetic and parasympathetic stimulation on the heart:
Sympathetic: Increases the heart rate and force of contraction
Parasympathetic: Decreases the heart rate and force of contraction.
What is the function of the visceral afferent fibres?
They convey sensory information from the heart back to the CNS.
What is the relevance of ischaemic myocardium and the visceral afferent fibres?
If the myocardium is ischaemic, the visceral sensory information is relayed back to our conscious perception and may be perceived as pain, burning, tightness or pressure in the chest. This is called referred pain.
What structures does the posterior mediastinum contain?
Descending aorta
Azygous vein
Oesophagus
Thoracic duct
Sympathetic trunk and splanchnic nerves
Posterior intercostal vessels and nerves
What are the branches that rise when the aorta descends through the posterior mediastinum?
Posterior intercostal arteries which supply the intercostal spaces
Bronchial arteries which supply the lungs
Oesophageal branches which supply the oesophagus
Pericardial branches which supply the pericardium
Phrenic branches which supply the diaphragm
At what level does the aorta pass the diaphragm?
T12
At what level does the azygous system of veins arise in the abdomen?
L1/L2
What is the function of the azygous system?
Drains blood from the posterior intercostal veins, oesophageal veins and the bronchial veins and returns it to the superior vena cava.
Where does the oesophagus lie in the posterior mediastinum?
Lies to the right of the aorta
At what level does the oesophagus pass through the diaphragm?
The oesophagus passes the oesophageal hiatus in the diaphragm at the level of T10.
What supplies the oesophagus?
The oesophageal arteries branching from the descending aorta.
Where does the thoracic duct lie?
Between the azygous vein and the aorta.
What is the cistern chyli?
A sac like swelling that gives rise to the thoracic duct when ascends into the thorax.
Where does the thoracic duct terminate?
By opening into the venous system at the junction between the left internal jugular vein and the left subclavian vein.
From what regions does the thoracic duct receive lymph?
The intercostal spaces and lymph nodes, the left side of the head and the neck and the left upper limb.
How are the right upper limb and right side of head and neck drained?
By lymphatic ducts that enter the venous system at the junction of the right internal jugular and right subclavian veins.
