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.