Sem 1 - F - Anterior & middle (of inferior) mediastinum - external/internal features, shape, blood supply, valves, innervation Flashcards
The thoracic cavity is split into the right hemithorax, the left hemithorax and the mediastinum The mediastinum can be split into superior and inferior mediastinum What is the line drawn that splits the mediastinum?
This would be a line drawn from the sternal angle posteriorly to the T4/5 intervertebral disc - this line is known as the transverse thoracic plane
What are the boundaries of the superior mediastinum?
Superiorly - thoracic inlet Inferiorly - transverse thoracic plane (runs from sternal angle to T4/5 IV disc) Anteriorly - manubrium Posteriorly - Bodies of T1-4 vertebrae Laterally - Pleura of lungs
What can the inferior mediastinum be split into? What structure does the separations of the inferior mediastinum depend upon?
Inferior mediastinum can be split into the anterior, middle and posterior Anterior = anterior to the fibrous pericardium Middle - within the fibrous pericardium Posterior - posterior to the fibrous pericardium
What are the boundaries of the anterior inferior mediastinum? (remember, will have a superior, inferior, anterior and posterior boundary)
Transverse thoracic pane superiorly Diaphargm inferiorly Body of sternum anteriorly Fibrous pericardium posteriorly
What are the contents of the anterior inferior mediastinum? Which structure is only present here in children?
Contents
Loose connective tissue Fat Lymphatics In children the thymus is also present in the anterior inferior mediastinum however this primary lymphoid organ has become fat in the superior mediastinum by the time adulthood is reached
What are the contents of the middle inferior mediastinum and what are the adjacent structures?
Contents Heart and pericardium Roots of the great vessels - aorta, pulmonary trunk, superior vena cava Adjacent structures * Great vessels * Phrenic nerve * Lung root structures
Is the fat covering the fibrous pericardium in the anterior or middle aspect of the inferior mediastinum?
The fat is in the anterior aspect of the inferior mediastinum
What proportion of the heart is to the right and left of the midsternal line? What is the nerve roots of the phrenic nerve and what does the phrenic nerve supply?
1/3rd of the heart is to right of the midsternal line 2/3rds of the heart is to the left of the midsternal line Phrenic nerve - C3,4,5 - supplies motor fibres to diaphragm, sensory fibres to fibrous pericardium, mediastinal pleura, diaphragmatic peritoneum
Where does the phrenic nerve pass in relation to the hilum of the lung? Where does the phrenic nerve pass in relation to the chambers of the heart?
Both right and left phrenic nerves pass anteriorly to the hilum of the lung Right phrenic nerve passes on the pericardium over the right atrium Left phrenic nerve passes on the pericardium over the left atrium and left and ventricle
What does the fibrous pericardium blend with superiorly and inferiorly?
Superiorly - the fibrous pericardium blends with the tunica adventitia of the great vessels (pulmonary trunk, aorta, superior vena cava) Inferiorly - the fibrous pericardium is continous with the central tendon of the diaphragm
Deep to fibrous pericardium is the serous pericardium divided into what? What is often under the deeper layer of serous pericardium?
The serous pericardium is divided in the serous visceral and serous parietal pericardium The serous visceral pericaridum is the deeper layer actually sitting on the heart itself and often has a fatty layer deep to it on the surface of the heart
State the arrangement of the pericardium all the way from the fibrous pericardium to the thin layer that lines the chambers of the heart? What is another name for the serous visceral pericardium?
Fibrous pericardium Serous parietal pericardium Pericardial cavity Serous visceral pericardium (also known as the epicardium) Myocardium Endocardium - thin surface lining of the chambers of the heart
Parietal pericardium reflected over the heart as visceral pericardium aka epicardium (outer layer of the heart) In the serous pericardium there are different sinuses formed by the reflections of the serous pericardium over the vessels exiting/entering the heart What are these two sinuses known as?
These are the oblique and the transverse sinus It is due to the way in which the parietal pericardium is reflected on to the heart as visceral pericardium
Where i the transverse pericardial sinus?
The transverse pericardial sinus runs posterior to the pulmonary trunk and ascending aorta and anterior to the superior vena cava - if sticking a finger in this sinus, it would allow one to separate the arteries and veins
Where is the oblique pericardial sinus and how is it formed? What sits anterior to the oblique pericardial sinus?
The oblique pericardal sinus is formed by the reflection of the serous parietal pericardium onto the pulmonary veins of the heart The oblique pericardial sinus runs in the space underneath and beind the heart between the IVC and 4 pulmonary veins Anterir to the oblqiue pericardial sinus is the left atrium
Transverse pericardial sinus - separates arteries of great vessels from veins - posterior to aorta and pulmonary trunk, anterior to SVC Oblique pericardial sinus - formed by reflection on the pulmonary veins - between IVC and pulmonary veins What shape is the heart said to be? What shape are the lungs said to be?
The heart is said to be trapezoidal shaped The lungs are said to be pyramidal shaped
Important to know the shape and orientation of the heart As said the heart is trapezoidal in shape The heart has a base, right border, inferior border, apex, left border and superior border Where is the base of the heart and what forms it?
The base of the heart is posterior and is mainly the left atrium
What makes up the different borders of the heart? * Right border * Inferior border * Apex * Left border * Superior border
Right border - right atrium Inferior border - right ventricle Apex - left ventricle Left border - left ventricle and left auricle Superior border - right and left atria and auricles
Bit that sticks out from the right atrium is the right auricle – just an expansion from the right atrium Which part of the left atrium is seen on the anterior surface of the heart? Where is the left atrium of the heart?
The left auricle is the part of the left atrium able to be seen on the anterior surface of the heart The left atrium is at the base of the heart (posterior)
There a number of indentations on the surface of the heart Which groove separates the atria from the ventricles (both names)? Which groove separates the ventricles of the heart?
The atrioventricular grooves separate the atria and ventricles of the heart - also known as coronary grooves as the coronary arteries run in these grooves The anterior and posterior interventicular grooves separate the ventricles of the heart
Which great vessel leaves the right ventricle? What does it split into? Which great vessel leaves the left ventricle? What does it branch into? Which great vessels enter the right atrium?
Pulmonary trunk leaves the right ventricle before bifurcating into right and left pulmonary arteries The aorta leaves the left ventricle a the ascending aorta and at the arch of the aorta gives off three branches, from right to left, brachiocephalic trunk, left common carotid artery, left subclavian artery Superior and inferior vena cava enter the right atrium
What are the circles covering here? (they are covering the vessels which the arows are pointing to?
The right and left coronary arteries running
What is the fibrous remnant of the ductus arteriosus known as? What was its function during foetal life? Where does it lie?
The fibrous remnant of the ductus arteriosus is the ligamentum arteriosum During foetal life its function was to allow communication between the pulmonary trunk and aorta therefore bypassing the foetus’s fluid filled lungs It lies just after the three vessels on the inferior surface of the arch of the aorta
What nerve runs posterior to the ligamentum arteriosum?
The left recurrent laryngeal nerve loops around the arch of the aorta posterior to the ligamentum arteriosum in the adult an back up to the neck
What branch does the circumflex artery give and what branches can it give (human variation)?
Circumflex artery gives off the left marginal artery before going to the posterior aspect of the heart in the atrioventricular groove Sometimes gives of a SA node and posterior inteventricular artery branch
Right coronary artery supplies: * R. atrium and most of R. ventricle * SA (usually) and AV nodes * Posterior 1/3 of IV septum * Part of L. ventricle What does the left coronary artery supply?
Left atrium and most of left ventricle Anterior 2/3rds of IV septum AV bundle Part of the right ventricle
Where do all the veins draining the heart drain to? There is one exception
All veins draining the heart technically drain into the coronary sinus which in turn drains into the right atrium of the heart The exception is the anterior cardiac veins which drains the wall of the right atrium directly into the right atrium
Veins of the heart * Great cardiac vein * Middle cardiac vein * Small cardiac vein What are these three veins’ equivalent? (ie which arteries do they run alongside) What are the other veins which drain into the coronary sinus? Remember, anterior cardiac veins drain the wall of the right atrium directly into the right atrium
Great cardiac vein - anterior interventricular artery Middle cardiac vein - posterior interventricular artery Small cardiac vein - right marginal artery Also have the Left marginal vein Left posterior ventricular vein Oblique vein of left atrium
In the wall of the RA separating it from the LA is the fossa ovalis What is this structure? WHat ae the muscular ridges in the anterior walls of the auricles/atria known as? What is the smooth posteiror wall of the RA known as?
Fossa ovalis - remnant of foramen ovale - used to connect the RA to LA to avoid unoxygenated blood going to the fluid filled feotal lungs Muscular ridges in anterior walls - musculi pectinati Smooth posterior wall of RA - sinus venarum
What is the function of the moderator band?
Provides a shortcut for electrical activity in the right ventricle so it does not have to descend down the right bundle branch blocks to purkinje fibres Allows a primary conduction route from the right AV bundle branch block to the anterior papillary muscles of heart causing them to contract
What are the muscular ridges of the LA and LV also known as? Which specific part of the left atrium actually has muscular ridges? What separates the LA from the LV?
The left atrium is mostly smooth walled, it is only the left auricle whih is muscula - the muscular ridges are known as musculi pectinati LV - trabeculae carnae This would be the bicuspid valve (Mitral valve)
Cuspid valves operate essentially on opposite principles from the semilunar valves Valves are open when there is low pressure in the ventricle When do the tricuspid (left) and bicuspid/mitral (right) valves close?
Pressure in the ventricles increases, the pressure in the atrium will decrease & cuspid valves will close The huge spike in pressure due to the ventricle contraction will also cause the papillary muscles to contract meaning the chordae tendinae will become taught preventing the valves opening
What is the difference in the valves during diastole and systole?
During diastole, the ventricles are relaxed and therefore the cuspid valves are open (pressure in atria is greater) & the semilunar valves are closed (coronary arteries fill) During systole, the ventricles are contracted meaning the cuspid valves are closed and the semilunar valves are open
What aspects of the fibrous skeleton provide support for the valves?
Left fibrous ring (supports mitral valve) Right fibrous ring (supports tricuspid valve) Fibrous coronet of pulmonary valve (supports pulmonary valve) Fibrous coronet of aortic valve (supports aortic valve)
Heart muscles cells left to their own devices will depolarise and contract but slowly The SA node ensures that this depolarisation and contraction occurs smoothly – it is the pacemaker for the heart regulating the heart rate * The SA node will spread from the RA to LA as well * The SA node recieves additional input from the ANS What in in the ANS helps innervate the heart? (where is the ganglia)
Heart recieves parasympathetic innervation from the Vagus nerve (X) - intrinsic ganglia Sympathetic innervation from T1-T5/6 spinal levels - cervical and superior thoracic paravertebral ganglia (sympathetic chain)
