heart and mediastinum Flashcards
Type of circulation in each side of heart
right- pulmonary
left- systemic
resistance and pressure in each side of heart
right- low resistance, pressure= 20mmHg
left- high/variable resistance, pressure= 130mmHg
Brief organisation and passage of blood in heart chambers
right atrium- receives deoxygenated blood from inferior and superior vena cava
blood passes through tricuspid valve into the right ventricle
leaves right ventricle via pulmonary trunk- goes to lungs
oxygenated blood passes into left atrium via pulmonary vein
passes through bicuspid valve into the left venticle
leaves via aorta
mediastinum definition
space between the lungs in the thoracic cavity where the heart is located
How is the heart separated from other mediastinal structures?
separated by a tough membrane known as the pericardium/ pericardial sac
Where does the heart sit?
Within the pericardial cavity, present in the mediastinum
Structure of pericardium
double walled sac, containing the heart and roots of the great vessels
two layers- serous layer and fibrous layer
encloses the pericardial cavity which contains pericardial fluid
structure of fibrous pericardium + function
- most superficial dense, loose connective tissue. Continuous with outer adventitial layer of great blood vessels
- protects the heart, anchors it to surrounding walls, prevents the overfilling with blood
two layers of serous pericardium + overall function
- divided into two layers- parietal and visceral
lubricates the heart to prevent friction during activity
parietal pericardium structure + function
fused to and inseparable from the fibrous pericardium
visceral pericardium structure + function
extends to the beginning of the great vessels- becoming one with the parietal layer- at the aorta and pulmonary trunk and the superior and inferior cavas enter the heart
visceral layer comes into contact with the heart- forming the epicardium. made of connective tissue and functions as a protective layer
consists of a simple squamous epithelium called mesothelium, reinforced with loose, irregular or areolar connective tissue
Where is the pericardial fluid located?
between the parietal and visceral serous pericardium in the pericardial cavity
process of leaving blood to lungs
leaves right ventricle which pumps deoxygenated blood into the pulmonary trunk
bifurcates into left and right pulmonary arteries ( actually 4 in total)
vessels branch many times until they form pulmonary capillaries where gaseous exchange takes place
Process of blood leaving lungs and entering heart
pulmonary capillaries form pulmonary veins
surface features of the heart
auricles, sulci, coronary arteries
structure and functions of auricles
superficial leaf-like extension of the atria near the superior surface of the heart- one on each side
shape resembles a human ear
relatively thin walled structures that can fill with blood and empty into atria or upper chambers of the heart
structures and functions of sulci
series of fat filled grooves along the superior surfaces of the heart
major coronary blood vessels located within the sulcus
Structure and functions of coronary arteries
right and left coronary arteries- with marginal and anterior and posterior interventricular arteries present- supply heart with oxygenated blood
no functional anastomoses
both left and ride originate from the aortic valve at the aortic sinuses
how can the origin of the coronary arteries be viewed?
Dissection
coronary angiogram, where a cannula is inserted with a contrast medium
How is deoxygenated blood leaving the coronary arteries returned to the heart?
coronary sinus- a collection of veins joined together to form a large vessel that collects blood from the myocardium
venae cordis minimae- small vessels that drain directly into the right atrium
coronary sinus structure
starts at junction of the great cardiac vein and the oblique vein of the left atrium- the end of the veins is marked by the Vieussens valve
runs transversely in the left atrioventricular groove on the posterior side of the heart
valve of coronary sinus is on the posterior, inferior surface of the hear, medial to the vena cava opening
Major veins
superior and inferior vena cava, pulmonary veins
What forms the superior vena cava?
formed in superior mediastinum from the right and left brachiocephalic veins
what forms the brachiocephalic veins? + functions
left and right internal jugular vein and left and right subclavian vein
jugular- draining the head
subclavian- draining the upper limb
what forms the inferior vena cava? + FUNCTION
left and right common iliac veins and the azygos vein and venous plexuses next to the spinal cord
deoxygenated blood from abdomen, pelvis and lower limbs
pulmonary veins function + structure
carries oxygenated blood from the lungs to the left atrium
four main pulmonary veins- two right and two left (two from each lung)
major arteries
aorta and pulmonary artery
pulmonary trunk structure and function
carries deoxygenated blood from the right ventricle to the lungs
branches into the right and left pulmonary arteries that each lead to one lobe
function of aorta
carries oxygenated blood from the left ventricle to the whole body
structure of aorta
ascending aorta from left ventricle
aortic arch curving round
descending thoracic aorta
the abdominal aorta
vessel divisions of aorta and functions
right to left:
- brachiocephalic trunk - gives rise to the right subclavian and common carotid
- right subclavian- upper limb
- right common carotid- divides into internal and external carotid artery. Internal supplies brain, external face
- left common carotid
- left subclavian
structure of atria
- no valves at inlets
- rough pectinate muscles and crista terminalis of His
- sinus venarum-
- right atrial appendage
- interatrial septum
- fossa ovalis
pectinate muscles structure, location and function
parallel ridges in the walls of the atria of the heart
Behind the crista terminalis, in front of the smooth muscle
fewer in left atrium
Crista terminalis structure, location and function
represents the junction between the sinus venosus and the heart in the developing embryo
forms sinus venarum
Sinus venarum structure, location and function
smooth part of right atria, separated from the rest of the atria by crista terminalis fibres
fossa ovalis structure, location and function
depression in the right atrium at the level of the interatrial septum
thin fibrous sheet that covered the foramen ovale after fetal development
structure of ventricles
- valves- tricuspid, mitral, pulmonary and aortic
- chordae tendinae
- trabeculae carnae
- interventricular septum
- papillary muscle
chordae tendinae structure, location
colloquially known as the heart strings
tendon resembling fibrous cords of the connective tissue that connect the papillary muscles to the tricuspid and mitral valves
How valves change during circulation of blood?
- during atrial systole, pressure in atria exceed that of ventricles, enabling blood to flow down the gradient
- Chordae tendinae are relaxed as the AV valves are forced open
- when ventricles pf the heart contract during systole, the blood pressure increases- pushing the AV valves close to prevent backflow- chordae tendineae prevent the eversion and prolapse by becoming tense
structure of tricuspid valve
- three leaflets, named anterior, posterior and septal
- each leaflet attached to the anterior, posterior and septal papillary muscles of the right ventricles
base of each cusp anchored to a fibrous ring that surrounds the orifice
structure of pulmonary valve
three cusps- left, right and anterior
structure of mitral valve
two cusps- anterior and posterior. both cusps secured to a fibrous ring at the orifice
structure of aortic valve
right, left and posterior cusp.
sides of each leaflet attached to the walls of the outflow vessel- slightly dilated to form a sinus
free superior edge of each leaflet is thickened to form a lunule and is widest in the midline- nodule
papillary muscle structure, location and function
3 muscles in right ventricle, 2 in left
muscles attach to the AV valves via chordae tendineae
begin to contract shortly before ventricular systole and maintain tension- prevent regurgitation through atrial cavities
trabeculae carnae structure, location and function
rounded, irregular columns of muscle that project from the inner surfaces of the ventricles
Either are attached along the entire length of one side as ridges or are fixed at their extremities but free in the middle, such as the moderator band
prevent suction that would occur with a flat surfaced membrane.
Their contraction also pulls on the chordae tendineae, preventing inversion of the mitral and tricuspid valves
Explain location of heart
dorsal surface- lies near the bodies of vertebrae
anterior surface- deep to the sternum and costal cartilages
base of heart- third intercostal cartilage
apex- lies to the left of the sternum, between the junction of the fourth and fifth ribs
bottom of heart lies against diaphragm
explain base of heart
great veins, superior and inferior vena cavae, arteries attach to the superior surface of the heart
Apex definition
tip of the heart
Cardiac notch definiton
depression in the medial surface of the inferior lobe of the left lung
divisions of the mediastinum
anterior, superior, middle and posterior
what is the mediastinum initially divided into + where?
superior and inferior mediastinum
sternal angle (sternal body and manubrium) and the T4/T5 intervertebral disc
where does the superior mediastinum terminate?
extends upwards, terminate at the superior thoracic aperture
where does the inferior mediastinum terminate?
extends downwards, diaphragm
borders of the superior mediastinum
superior- thoracic inlet
inferior- inferior mediastinum
anterior- manubrium of sternum
posterior- vertebral bodies of T1-T4
lateral- pleurae of lungs
what vessels are present in the superior mediastinum?
arch of aorta, superior vena cava
Left and right brachiocephalic veins
brachiocephalic artery, left common carotid artery and subclavian artery
what nerves are present in superior mediastinum?
right vagus nerve- runs parallel to the trachea and passes posteriorly to the superior vena cava and right primary bronchus
left vagus nerve- enters superior mediastinum between left common carotid and left subclavian arteries, descends anteriorly to the aortic arch, before travelling posterior to the left bronchus
phrenic nerve- enters superior mediastinum lateral to the great vessels
other structures in superior mediastinum
thymus- most anterior structure, sits against posterior surface of sternum and extends into anterior mediastinum
trachea
oesophagus
thoracic duct
middle mediastinum structures
heart and pericardium
tracheal bifurcation
middle mediastinum vesels
ascending aorta
pulmonary trunk
superior vena cava
middle mediastinum nerves
left and right phrenic to diaphragm
middle mediastinum lymphatics
tracheobronchial lymph nodes
borders of middle mediastinum
anterior- anterior margin of pericardium
posterior- posterior margin of pericardium
laterally- mediastinal pleura of the lungs
superiorly- superior mediastinum
inferiorly- diaphragm
posterior mediastinum borders
lateral- mediastinal pleura (parietal pleura)
anterior- pericardium
posterior- T5-T12 vertebrae
roof- superior mediastinum
floor- diaphragm
vessels in posterior mediastinum
thoracic aorta + its divisions such as the superior phrenic arteries
azygos, hemiazygos and accessoryhemiazygos vein
thoracic duct
structures in posterior mediastinum
oesophagus , posterior to the arch of the aorta and heart - deviates to the left as it moves downwards
nerves in posterior mediastinum
thoracic sympathetic trunks
anterior mediastinum borders
lateral- mediastinal pleura
anterior- body of sternum and transversus thoracic muscles
posterior- pericardium
roof- superior mediastinum
floor- diaphragm
contents of anterior mediastinum
no major structures
accomodates loose connective tissue, some lymph vessels, lymph nodes and branches of internal thoracic vessels
what are coronary arteries an example of?
functional end arteries
functional end artery definition
an artery that has ineffectual anastomoses
why is this a problem?
if there is an occlusion in the coronary artery, there is limited ways the blood can perfuse the heart so can lead to a myocardial infarction
when does coronary artery perfusion occur? + why
during heart relaxation- diastole
during systole the subenchocardial coronary vessels are compressed due to high ventricular pressures
2 consequences of coronary artery occlusion + definitions
angina- chest pain or pressure due to a decreased blood flow to the heart
myocardial ischaemia- restricted blood flow to the heart, can lead to death of cardiomyocytes- leading to a heart attack
embryological condition affecting the heart + explanation
situs inversus- major visceral organs are reversed or mirrored from their normal positions - all organs flipped, heart on the right side, everything is normal
lymph node location
bronchopulmonary nodes situated in the hilum of each lung
lymph then travels to trachiobronchial nodes and then to paratracheal
then enters the right lymphatic duct or left thoracic duct
aortic aneurysm explained
enlargement/dilation of the aorta, greater than 1.5 times it normal size
no symptoms unless it ruptures
most commonly found in abdominal aorta, sometimes thoracic
weakens the wall which leads to aortic rupture
