Week 3 Flashcards
Mediastinum, Pericardium & Heart
Which part of the medistinum encloses the heart (contains it)
The middle inferior mediastinum.
Position of the heart
- behind the body of sternum
- between 2nd and 6th ribs
- lies 1/3 to the right and 2/3 to the left of the median plane.
what is the pericardium?
A fibroserous membrane which covers the heart and great vessels. It is made up of a double layered close sac; the first layer being the fibrous pericardium and the second being the serous pericardium.
What is the fibrous pericardium continuous with?
Continuous with central tendon and serous pericardium - parietal layer they are attached to each other
what does the serous pericardium consist of?
The parietal layer of serous pericardium and visceral layer of serous pericardium (epicardium)
Where is the pericardial cavity found?
Between the parietal and visceral layers, it seperates these layers.
Label this diagram of the heart layers
what does peri and cardium mean?
peri = around
cardium = heart
it essentially means layer around the heart and great vessels, its a very tough layer
What are pericardial sinuses?
When the heart is developing and folding it creates spaces where the surgeon can insert their hands/fingers to lift the heart. There are 2 pericardial sinuses
What are the 2 pericardial sinuses?
Transverse pericardial sinus and oblique pericardial sinus.
Where is the oblique pericardial sinus located?
In between the 4 pulmonary veins that are coming back from the lungs. there are 2 veins on either side so the space in between them is the sinus.
Where is the transverse percardial sinus located?
Underneath the ascending aorta above/superior to the oblique pericardial sinus(where the red dot is and the black arrow)
Which arteries supply the pericardium?
- Pericardiacophrenic artery which is branching off from the internal thoracic artery
-Musculophrenic artery which also branches off from the internal thoracic artery
-Bronchial, oesophargeal and superior phrenic artery branching off from the descending thoracic aorta
-Coronary artery which branches off from the ascending aorta.
*when a structure passes a certain other structure especially when it comes to neurovascular bundles it will give off branches towards that structure. etc the arteries that are going to supply the diaphragm are passing around the pericardial region they will be considered to supply the pericardium.
What veins drain into/ supply the pericardium?
- a lot of the blood will go back to the heart via the pericardiacophrenic veins brancing form the brachiocephalic or internal thoracic veins.
- Then it will go into the azygos venous system in the posterior thoracic region.
What nerves innervate the pericardium?
All of the nerves that pass through and supply the pericardium include:
- phrenic nerve its root values are C3,4,5
- vagus nerve (cranial nerve 10)
- sympathetic trunks
What is the difference between the phrenic and vagus nerve?
- they both run in the same direction.
- the difference is that the vagus lies posterior to the hilum and the phrenic comes anterior to the hilum.
Cardiac cycle (what direction does blood enter heart) (VERY IMPORTANT)
- blood from inferior and superior vena cava will enter through the right atrium.
- it passes through the tricuspid valve through to the right ventricle,
- blood moves upwards through pulmonary semilunar valve into the pulmonary trunk,( a single structure but it will divide into pulmonary arteries when it reaches the arch of the aorta )
- blood then leaves through the left pulmonary artery to enter lungs and become oxygenated and comes back into heart via the pulmonary veins (there are generally 4 altogether but can sometimes be 1 on either side)
5.now enters the left atrium(simpler than right side), them enters the bicuspid valves - Then enters into the left ventricle (most pressured ventricle), which will push the blood through into the ascending aorta which is regulated by the aortic semilunar valve
- then enters into the arch and further backwards into the descending aorta.
8.The arch of the aorta then has 3 branches; the 1st one is brachiocephalic trunk, 2nd is the left common carotid artery and the 3rd one is left subclavian artery.
What is the heart?
- a hollow, fibromuscular organ
- it is pyramidal shaped meaning its apex/edge is on the inferior end, has a base, borders and surfaces
-weight: males usually 280-340g, women usually 230-280g.(your heart is roughly the same size as your clenched fist).
What is the heart wall made up of?
3 layers
Endocardium:
- thin internal layer
- forms lining membrane on the internal part of heart
-has a smooth slippery structure tp allow blood to not coagulate in certain areas
Myocardium:
- thick large helical muscle layer
- middle layer
Epicardium:
- thin external layer
- same thing as visceral layer of serous pericardium
Where does the apex of the heart lie?
– Inferolateral part of left
ventricle
– Lies posterior to left 5th
intercostal space
– Found 9cm from the
median plane therefore why its considered to be mostly on the left side of the body.
where does the base of heart lie?
theres 2 theories:
1. the bit that lies right to the posterior aspect.
2. other sources consider the base of the bottom part where the great vessels leave the heart or enter the heart.
- Left atrium & partly right
atrium
– Face posteriorly towards
bodies of T6-9
How many surfaces does the heart have ?
4; anterior(sternocostal), inferior (diaphragmatic), left pulmonary and right pulmonary.
Where is the diaphragmatic surface of the heart?
- the diaphragm starts below the inferior vena cava, so thats the area known as the diaphragmatic surface.
- mostly left ventricle and partly right ventricle
- central tendon
Where is the anterior(sternocostal) surface of the heart?
right ventricle area
Where is the left pulmonary surface?
left ventricle area
What are the borders of the heart?
- Trapezoidal shaped
There are 4 borders; - right;right atrium extending between SVC n IVC
-inferior;right ventricle and slightly left ventricle
-left; left ventricle and left auricle
-superior; right and left atria & auricles
and forms inferior boundary of transverse pericardial sinus)
where is the right pulmonary surface?
right atrium area
Right atrium basic functions
- forms right border
- receives deoxygenated blood from SVC, IVC and coronary sinus which is the opening of the right atrium basically the venous drainage of the heart muscle itself.
what does the right atrium consist of?
- right auricle; earlike muscular pouch, which si the extension of the rough wall structure. auricle comes from the word earlike structure. this structure is slightly higher than the rest of the chamber
interior;
-sinus venarum; smooth, thin-walled posterior part includes the SVC, IVS and coronary sinus opening
-rough muscular anterior wall; pectinate muscles
-right atrioventricular orifice; right atrio-ventricular valve.
label this diagram (internal right atrium structures) and state whether it is an anterior/posterior view?
What is the crista terminalis and sulcus terminalis ?
- opening up the chamber to reflect the rough wall in this fashion we find that theres a line between the smooth and rough, which is known as the Crista terminalis(an internal vertical ridge seperating rough and smooth walls
- when we close the chamber again on the external surface the crista terminalis is like a dip and it is called the sulcus terminalis which is an external seperation between rough and smooth walls
where is the opening of coronary sinus?
between right AV orifice and IVC orifice
What is the fossa ovalis, and fossa ovale?
On the sina venarum we see a transparent oval like structure that is located in the inferior aspect of the right interatrial septum between the right atrium and the left atrium. A remnant of an interatrial opening, the foramen ovale, which has a significant role in fetal circulation, the fossa ovalis forms by the fusion of the septum primum and septum secundum.
What structures are part of the internal right ventricle?
- conus arteriosus; part of the smooth wall. It is a superior part w a smooth transition of blood leading straight to the pulmonary trunk.
- trabeculae carnae; part of the rough wall. interior irregular muscular elevations which help push blood into the pulmonary trunk towards the lungs.
- supraventricular crest; seperates rough and smooth parts-we wont be asked to identify it.
- right Atrioventricular orifice, Tricuspid valve and orifice – The “Right AV orifice” refers to the opening between the right atrium (RA) and the right ventricle (RV) of the heart. It is also known as the “tricuspid orifice” because it is guarded by the tricuspid valve. The tricuspid valve is a cardiac valve that separates the right atrium from the right ventricle and prevents the backflow of blood from the ventricle into the atrium during ventricular contraction. It is called “tricuspid” because it consists of three leaflets or cusps.(anterior, septal and posterior), with the base of each cusp anchored to a fibrous ring that surrounds the orifice.
What do we call the connections between the cusps and the walls?
Chordae tendineae:
- Part of the right ventricle
– Anterior, posterior & septal
cusps
– Arise from apex of
papillary muscles
What muscles do the tricuspid valves attach to?
Papillary muscles that project from the rough end walls. There is an anterior papillary muscle which is the largest, a posterior papillary muscle which may consist of several parts and a septal papillary muscle; the septal muscles on left side of the interventricular septum anchor the bicuspid valve while the ones on the right side anchor the tricuspid valve
- these muscles regulate the opening and closing of right ventricle -tricuspid valve chamber???
what is the role of the septomarginal band/septomarginal trebecula/moderator band ?
septomarginal band/septomarginal trebecula/moderator band contains the atrioventricular bundle that stimulates the heart muscles.
what is the pulmonary orifice?
The pulmonary valve is a valve of the heart that lies between the right ventricle and the pulmonary trunk (this space is known as the pulmonary orifice)
- valve has has three cusps.
What structures are in the left atrium?
*Left auricle (an extension of the chamber)
– has pectinate muscles within it
* Interior part
– most of the atrium is very large smooth wall part (has Four pulmonary veins)
– Small muscular part
– Left Atrioventricular orifice is the opening from left atrium to Left ventricle
structures in the left ventricle:
- Trabeculae carnae; roughened wall
- Anterior and Posterior Papillary muscles
- Aortic vestibule; opening for aorta
- biscuspid valve/mitral valve
– Left AV orifice
– Two cusps (Anterior & posterior) - Semilunar aortic valve
What are the types of semilunar valves?
We have 2 semilunar valves:
-The pulmonary valve which is where the pulmonary trunk is. Has 3 semilunar cusps.
- and the aortic valve where the aorta is. Also has 3 semilunar cusps.
Location of right coronary artery
- auricle covers the beginning of right coronary artery coming pff the ascending aorta. It then runs in the coronary sulcus, as it passes inferiorly, it then wraps around the heart t then end by giving off a large branch.
-Along its pathway it gives off a number of branches towards the apex. We dont name every branch, but there are certain branches to know: ascending sinoatrial node, right marginal artery, atrioventricular nodal artery and posterior interventricular artery.
Location of left coronary artery (the image is a posterior view; so the left side is non anatomy left)
- Very short 2-3cm long
- Passes between left auricle and left side of pulmonary trunk
- it terminates into 2 branches; 1 running straight to the apex of the heart called the anterior inter-ventricular artery. Another one that follows towards the posterior side called the circumflex (around the heart)
what are coronary artery variations?
- They are not abnormalities, they’re just different pathways that structures have taken and that most of the time is due to development.
the variations are: - right dominant pattern; 67% of population will have equal distribution
-left artery dominant; posterior IV branch of circumflex. - some hearts only have a single coronary artery which supplies the entire heart.
- some have a circumflex that starts from right aortic sinus
-4% of population will have an accessory coronary artery.
-most variations are only found when people will have health issues, when there is a change in heart function. - ## variations are extremely important in surgery, if surgeon wasn’t aware there would be more damage than repair.
What is the conducting system of the heart?
- Heart muscles don’t just work on their own, they have to be stimulated, when these muscles aren’t stimulated, we then put in a pacemaker
-our natural internal pacemaker generates and transmits impulses; coordinated contraction - natural internal pacemaker in the body is a conducting system made up of different nodes; sinoatrial (SA) node, atrioventricular (AV) node.
-These nodes give off branches which eventually stimulate each of the muscles via the Purkinje Fibres to then pump blood through the heart.
What are the Great vessels of the heart?
- Superior Vena Cava
- Inferior Vena Cava
- both vena cavas bring deoxygenated blood to your heart to get oxygen.
- Pulmonary trunk; transporting deoxygenated blood from the heart towards the lungs.
- Pulmonary veins; transfer freshly oxygenated blood from the lungs to the left atria of the heart.
- Aorta
– Ascending
– Arch
– Descending
what structures are talked about in Embryology of heart
- Primitive heart tube
- Cardiac looping
- Atrial septum formation
- Ventricular septum
formation - Fetal blood circulation
what is Primitive heart tube?
- around the End of 3rd week of
embryonic development - Fusion of two seperate endocardial
tubes which then join up and create spaces within them called sacculations.
-these sacculations are important as they create the chambers. - Develops five
sacculations:
– Sinus venosus (bottom)
– Primitive atrium
– Primitive ventricle
– Bulbis cordis;
– Truncus arteriosus (top)
what does each sacculation eventually become?
what is cardiac looping?
During the early phases of its development, the initially straight embryonic heart tube becomes transformed into a helically wound loop that is normally seen with a counterclockwise winding within a certain area, it will start folding.
how does the atrial septum form?
It involves the creation of a barrier between the left and right atria of the heart. Here’s a breakdown of the steps:
1.Septum primum: This is the initial structure that forms during atrial septum development. It grows from the roof of the primitive atrium towards the endocardial cushions, which are specialized structures in the developing heart. As it grows, it creates an opening called the ostium primum.
2.Absorption of Septum primum: Eventually, the septum primum is absorbed in certain areas. This absorption leads to the formation of a new opening called the ostium secundum, while the ostium primum starts closing.
3.Septum secundum: As the ostium primum is closing, another structure, the septum secundum, begins to form. Unlike the septum primum, which grows towards the endocardial cushions, the septum secundum grows independent of them. It grows to cover the ostium secundum but leaves a small opening called the foramen ovale.
4.Foramen ovale: The foramen ovale is a small hole between the two atria that allows blood to pass directly from the right atrium to the left atrium in the developing fetus, bypassing the lungs. This is crucial for fetal circulation. After birth, when the lungs begin functioning, the pressure in the left atrium increases, leading to the closure of the foramen ovale. Eventually, it becomes a depression known as the fossa ovalis.
how does the Ventricular septum form?
- Endocardial cushion
- Right and left bulbar
ridges develop - Membranous
interventricular septum
grows - Interventricular
foramen closed
Fetal blood circulation
Umbilical Vein →ductus
venosus (which is through potential liver, and will close to become a ligamentum venosum) → IVC (then right atrium, some of it)→
( then passes through the shunt)foramen ovale → left
atrium → L.V (instead of going to lungs it goes quicly to the aorta)→ Aorta
→ umbilical artery then back to mother.
SVC & IVC → R.atrium →
R.ventricle →
pulmonary A → ductus
arteriosus (a short vessel that connects the fetal pulmonary artery to the aorta and involutes it following birth)
Circulation after birth
- Umbilical arteries
– becomes the Medial umbilical ligaments - Umbilical vein
– becomes the Ligamentum teres of the liver; the liver ductus closes off as we dont want blood to go through there anymore. - blood goes through to lungs then normal circulation…
- Ductus venosus
– Ligamentum venosum - Ductus arteriosus
– Ligamentum arteriosum - Foramen ovale
– fossa ovalis
what heart structures are found in Superior mediastinum?
- found Superior to transverse
thoracic plane
– at T4/T5 level - these are all the structures that lie in the superior mediastinum(Anterior to posterior):
– Thymus
– Veins
– Arteries
– Airway
– Alimentary tract
– Lymphatic trunks
what is the thymus?
(pic is anterior view)
* a Primary lymphoid organ
– allows for Maturation of T-lymphocytes
* Location
– Inferior part of neck
– Anterior part of superior
mediastinum
– Posterior to manubrium
– Anterior to fibrous
pericardium
* Flat bi-lobed gland
- you can see it better in younger ppl.
* Puberty
– Undergoes gradual involution
– Athrophy (can still be found in adults)
what are the Brachiocephalic veins (BCV)?
- found on Left & right
– Unite to form SVC (superior vena cava on the right side of the upper chest)
– near 1st right costal cartilage - Each BCV formed by
union of
– Internal jugular vein
– Subclavian veins - Left
– Anterior to roots of
branches of aorta - function: Drain blood in head, neck & upper limbs
superior vena cava (svc) function
- Returns blood from
above diaphragm
– Except heart & lungs - Ends at level of 3rd
costal cartilage - Empties into the right
atrium
aorta(ascending, arch and descending) diagram
what are the two types of nerves in the superior mediatinum?
- Vagus
– Left - Left recurrent laryngeal
– Arch of aorta
– Right - Right recurrent laryngeal
– Right subclavian artery - Phrenic
– Passes anterior to roots of
lungs
– Left & right
– Supplies diaphragm from
the inferior surface
what is the Oesophagus?
Fibro-muscular tube
* Extends from pharynx to
stomach
* Enters superior
mediastinum between
trachea & vertebral
column
* Passes through posterior
mediastinum
* Right side of aorta
* Diaphragm
– Level T10
what is the Azygos system of veins, its functions and the different variations?
- Drains the back &
thoracoabdominal walls - Lots of variations
- Azygos vein
– Empties into SVC - Hemi-azygos vein
– Crosses from left to right at
T9 - Accessory azygos vein
– Crosses from left to right at
T7/T8
what is the Thoracic duct, its location, origin and fucntion?
- Largest lymphatic channel
in the body - Location
– Anterior bodies of T6-T12 - Originates from cisterna
chyli
– Abdomen - Conveys lymph to venous
system
– Origin of left
brachiocephalic vein
what are the Nerves of posterior mediastinum?
- Sympathetic trunks &
ganglia
– in Autonomic nervous
system - Thoracic sympathetic
trunks
– Continuous with other
sympathetic trunks
