Heart and Great Vessels - SDL Worksheet Flashcards
Define the term mediastinum
Mass of tissues and organs separating the sternum in front and the vertebral column behind, containing the heart, its vessels, trachea, oesophagus, thymus, lymph nodes and other structures and tissues
What is the mediastinum divided into?
2 parts by imaginary line –> superior and inferior
Where is mediastinum divided?
By imaginary line from the sternal angle to T4 vertebrae.
Where does superior aspect of mediastinum terminate?
extends upwards, terminates at superior thoracic aperture
Where does inferior aspect of mediastinum terminate?
extends downwards, terminates at the diaphragm
What can the inferior aspect of the mediastinum be divided into?
Anterior, middle and posterior
Describe boundaries of:
- Anterior
- Posterior
- Lateral
- Superior
- Inferior mediastinum
- Pericardium
- Bodies of thoracic vertebrae 5-12
- Mediastinal pleura
- Plane of sternal angle up to superior thoracic aperture
- Sternal angle down to diaph§agm
What is the phrenic nerve?
Bilateral, mixed nerve that originates in the neck and descends through the thorax to reach the diaphragm. As the only source of motor innervation to the diaphragm this nerve has an important role in breathing
What is the motor function of the phrenic nerve?
Innervates the diaphragm
What is the sensory function of the phrenic nerve?
Innervates the central part of diaphragm, the pericardium and mediastinal part of parietal pleura
Where does the right phrenic pass in relation to the subclavian artery and vein?
Passes anteriorly to the 2nd part of subclavian artery, and posteriorly to the subclavian vein.
Enters thorax.
How does the right phrenic pass into the thorax?
Enters thorax via superior thoracic aperture
Where does the right phrenic pass after entering thorax?
Descends anteriorly to the right lung root, down the right side of the pericardium. Reaches the diaphragm and pierces the muscle to supply the underlying surface
Where does the left phrenic pass in relation to the subclavian artery and vein?
Passes anteriorly to the 1st part of subclavian artery and posteriorly to the subclavian vein.
Enters thorax
How does the left phrenic pass into the thorax?
Enters thorax via superior thoracic aperture
Where does the left phrenic pass after entering thorax?
Crosses the aortic arch and vagus nerve, and descends anteriorly to the left lung root, down the left side of the pericardium. Reaches the diaphragm and pieces the muscle to supply the underlying surface
Describe the vagus nerve
- 10th cranial nerve (CN X)
- Longest cranial nerve
Describe the origin of the vagus nerve
Originates from the medulla of the brainstem
How does the vagus nerve exit the cranium?
Via jugular foramen
Where does the auricular branch of the vagus arise?
Within the cranium
Describe the route of the common vagus nerve after leaving the cranium
Passes into carotid sheath, travelling inferiorly with the internal jugular vein and common carotid artery. R and L have different pathways
Describe pathway of left vagus
Passes inferiorly between left common carotid and left subclavian arteries, posterior to the sternoclavicular joint, entering thorax
Describe pathway of right vagus
Passes anterior to the subclavian artery and posterior to the sternoclavicular joint, entering thorax
What branches arise in the neck of the vagus (after it leaves the cranium)?
- Pharyngeal branches
- Superior laryngeal nerve
- Recurrent laryngeal nerve (right side only)
What is function of the pharyngeal branches?
Provides motor innervation for muscles pharynx and soft palate
What does the superior laryngeal nerve split into?
Splits into internal and external branches
What does the external laryngeal nerve innervate?
The cricothyroid muscle of the larynx
What does the internal laryngeal nerve innervate?
Provides sensory innervation to the laryngopharynx and superior part of the larynx.
What does the recurrent laryngeal nerve innervate?
Hooks underneath the right subclavian artery, then ascends towards to the larynx. It innervates the majority of the intrinsic muscles of the larynx.
Describe vagus nerve once it enters thorax
- Forms posterior vagal trunk (right), anterior vagal trunk (left)
Where does left recurrent laryngeal nerve arise? What is its function?
In the thorax
Hooks under arch of aorta, ascending to innervate the majority of intrinsic muscles in larynx), cardiac branches (innervate regulate heart rate and provide visceral sensation to the organ)
How do the vagal trunks terminate?
By dividing into branches that supply the oesophagus, stomach, small and large bowel
What are branches of ascending aorta?
Rises up from the heart. The coronary arteries branch off the ascending aorta to supply the heart with blood
Branches of aortic arch?
- Brachiocephalic trunk
- Left common carotid artery
- Left subclavian artery
What is the ligamentum arteriosum?
Arterial ligament. Small ligament connected to the superior surface of the proximal descending aorta and left pulmonary artery
What is function of ligamentum arteriosum?
It develops about 3 weeks after birth. Prevents mix of deO2 and O2 blood.
Describe function of right and left brachiocephalic veins
Drain deO2 blood from upper limbs, neck and head to the superior vena cava
Left brachiocephalic vein is usually longer than right.
What is the function of the azygos vein?
Transports deo2 blood from posterior walls of the thorax and abdomen into the superior vena cava vein.
Describe route of the azygos vein
Originates from posterior aspect of the inferior vena cava, at the level of the renal veins. It ascends within the posterior mediastinum to the level of T4 before it arches above the right pulmonary hilum. It drains into the superior vena cava just before it pierces the pericardium.
What is the SVC formed by?
The R and L brachiocephalic veins
Describe the sympathetic chain and its function
Is each of the pair of ganglionated longitudinal cords of the sympathetic nervous system, situated on either side of the vertebral column.
It allows nerve fibres to travel to spinal nerves that are superior and inferior to the one in which they originated.
What is the fibrous pericardium?
Outermost layer of the pericardial membranes around the heart. It’s a tough collagenous sheet that is superficial to the parietal layer of the serous pericardium
What is the serous pericardium?
Inner layer of pericardium, composed of 2 layers. The outer layer: parietal layer is completely adhered to the fibrous pericardium. The inner layer: visceral layer, covers and protects the great vessels and heart.
What is the pulmonary trunk?
Major vessel of human heart that originates from right ventricle. Branches into right and left pulmonary arteries, which lead to the lungs
Describe the IVC and its formation
Large vein carries Deo2 blood from lower and middle body into right atrium of the heart. It is formed by joining of L & R common iliac veins, usually at level of 5th lumbar vertebra
What is the atrioventricular groove?
Separates atria from ventricles. Perpendicular to the intraventricular groove.
Why is the atrioventricular groove obscured on the anterior surface of the heart?
Obscured on the anterior (front) surface of the heart by the pulmonary trunk and aorta as they emerge from the heart.
What does the left coronary artery divide into?
Left anterior descending artery and circumflex branch, supplies blood to the heart ventricles and left atrium.
What does the right coronary artery divide into?
Right posterior descending artery and large marginal branch, supplies blood to heart ventricles, right atrium, and SA node.
What is the coronary sinus?
Collection of veins joined together to form a large vessel that collects blood from the heart muscle (myocardium). Delivers deo2 blood to right atrium
What is function of apex of heart?
Responsible for regulating ventricular contraction
What is the majority of the blood from the heart wall drained through?
Most drains into right atrium through coronary sinus which lies in the posterior part of the atrioventricular groove and is a continuation of great cardiac vein. Opens into right atrium to left of IVC. Small and middle cardiac veins are tributaries of coronary sinus.
Function of cardiac veins?
Returns deo2 blood from myocardium to the right atrium (from anterior surfaces of left ventricle)
What is the remainder of the blood from the heart wall drained by?
Anterior cardiac vein and by small veins that open directly into heart chambers
Why might an intrathoracic tumour lead to loss of voice?
Compression of recurrent laryngeal nerve which supplies the larynx.
Does the phrenic nerve carry somatic or autonomic fibres?
Somatic nerve – but it is complicated due to the respiratory centre in the medulla, which means it is activated without conscious thought. This is different to the autonomic nervous system.
Does the vagus nerve carry somatic or autonomic fibres to thoracic organs?
Both
Where do the intercostal nerves originate?
Anterior rami of T1-T11 nerves
Where do intercostal nerves run?
In intercostal spaces between internal and innermost layers of intercostal muscles
What do the intercostal nerves supply?
Muscles in and over intercostal space; lower nerves supply muscles and skin of anterolateral abdominal wall
Where do the subcostal nerves originate?
Anterior ramus of T12 nerve
Where do the subcostal nerves run?
Follows inferior border of 12th rib and passes into abdominal wall
What do subcostal nerves supply?
Abdominal wall and skin of gluteal region
What is effect of parasympathetic/sympathetic fibres on bronchioles?
Parasympathetic fibres constrict bronchioles
Sympathetic fibres dilate them
What are sympathetic ganglia made up of?
Cell bodies of post-ganglionic sympathetic nerve fibres
What is a nerve plexus?
A collection of postganglionic sympathetic and postganglionic parasympathetic nerve fibres
What structures are supplied by the pulmonary plexus of autonomic nerves?
The bronchi and bronchioles of the respiratory tree
Where does the pulmonary plexus lie?
Anterior and posterior to the bifurcation of the trachea
Does the pulmonary plexus contain para or sympathetic fibres?
Both
What is the function of the pericardium?
- Protect the heart
- Provide an environment which allows for the smooth contraction of the atria and ventricles
What is pericardial effusion?
What can it lead to?
- Collection of fluid in the pericardium
- Can lead to cardiac tamponade –> this excess prevents the full dilation (and therefore filling) of the heart chambers during the cardia cycle, limiting cardia output
What structures form:
- The right border
- The left border
- The inferior border
- The apex
- The right atrium
- Left auricle and left ventricle
- Right ventricle
- Mainly left ventricle (some of right)
When do the aortic and pulmonary (SL) valves close?
During ventricular diastole
Where are the aortic sinuses?
The space located behind the cusps of the valve on the pulmonary or aortic surface. There are three associated with each cusp – left, right, posterior (aortic), anterior (pulmonary).
Where do the coronary arteries arise?
Aortic sinuses, left and right for left and right CAs.
Which coronary artery usually gives the greater supply to the SA and AV nodes of the heart?
Right
What is a functional end artery?
The sole artery that supply oxygenated blood to a tissue or an organ. End arteries are critical since any occlusion in those arteries leads a tissue/organ to be completely cut off of oxygenated blood, leading to eventual necrosis.
What is coronary thrombosis?
Interruption/blockage of the blood supply to the heart due to a blocked coronary artery.
What is myocardial infarction?
A heart attack. Loss of blood to the heart preventing it from pumping effectively.
What is angina pectoris?
Chest pain associated with coronary heart disease
Where does the coronary sinus lie?
Lies in the atrioventricular groove on the posterior surface of the heart and opens into the right atrium
Where do nerve fibres that reach the heart come from?
The cardiac autonomic plexus, which lies beneath the arch of the aorta.
Fibres are distributed from the plexus to the SA and AV nodes, the myocardium and the coronary arteries.
Where do the sympathetic fibres in the cardiac plexus come from?
Sympathetic chain
Where do the parasympathetic fibres in the cardiac plexus come from?
Vagus nerves
How is the action of the heart affected by:
(i) sympathetic stimulation?
(ii) parasympathetic stimulation?
(i) Increase in cardiac output via increased stroke volume and heart rate
(ii) The opposite
Pain from the heart e.g in angina pectoris, is commonly experienced over the left side of the chest and medial aspect of the left arm. How is this pattern of “cardiac referred pain” accounted for?
Noxious stimuli travels retrograde along the sympathetic fibres to the spinal cord at the level which it also receives somatic sensation via spinal nerves. As the CNS is not used to feeling pain from the internal viscera it believe the pain is coming from the body wall (which it usually receives sensation from). If you know which spinal cord levels the sympathetic fibres come from to supply the heart, you should know which area of the skin would ‘feel’ this pain by looking a dermatome map.
What is the superior thoracic aperture also known as?
Thoracic inlet
What is the superior thoracic aperture?
The thoracic inlet is essentially a hole surrounded by a bony ring, through which several vital structures pass.
Connects the root of neck to the thorax
