Anatomy 1 Flashcards
Describe surface anatomy
The ability to visualise how anatomical structures in the thorax are related to surface features is fundamental to physical examinations
What structures lie at the sternal angle?
- rib 2
- aortic arch
- tracheal bifurcation (carina)
- pulmonary trunk
- ligamentum arteriosum
- azygous vein drains into SVC
- nerves (cardiac plexus, loop of recurrent laryngeal etc.)
- thoracic duct (right to left movement before exiting thoracic inlet)
Describe the location of the heart
- usually between ribs 2 and 5th intercostal space
- extends from right medial border of sternum to having its apex at the midclavicular line on the left
- vertebral levels T4- T9
- when supine:T4/5 - T8
- when standing:T6 - T9
Why can heart location change?
- pathology e.g. cardiomegaly or displaced by mediastinal or lung conditions
- when displaced, heart moves inferiorly and laterally towards axilla
What is heart attached to diaphragm via?
its pericardium
What is the rough weight of an adult heart and what are the dimensions?
250-350 grams
roughly size of a fist
12cm length, 8cm width, 6cm thickness
Why might heart size vary?
- based on individual factors e.g. fitness
- athletes may have larger hearts due to muscle growth from exercise
What three compartments can the thoracic cavity be divided into and which one is the heart located in?
- right and left pleural cavities
- mediastinum (heart located here)
Where is the mediastinum located and what does it contain? (6)
- in between pleural cavities
- heart
- oesophagus
- trachea
- major nerves
- major blood vessels
- thymus gland
What are the locations of the different parts of the mediastinum?
- anterior to posterior: extends from sternum to the bodies of the vertebrae (T1 - T12)
- superior to inferior: superior thoracic aperture to the diaphragm
- laterally (R & L): mediastinal pleurae
At what location is the mediastinum divided?
- at transverse plane extending from sternal angle to intervertebral disc between T4 and T5 vertebrae
- divides mediastinum into superior and inferior mediastinum
What is the inferior mediastinum further subdivided into and what is it relative to?
- anterior, middle, posterior
- relative to pericardial sac
What is the cardiothoracic ratio (CTR)?
- ratio of maximal horizontal cardiac diameter to maximal horizontal thoracic diameter (inner edge of ribs/ edge of pleura)
- a normal measurement should be <0.5
What is the clinical significance of the CTR?
- aids in detection of enlargement of the heart which is most commonly from cardiomegaly
- could also be due to pericardial effusion
What structures does the superior mediastinum contain? (4)
- thymus gland
- trachea
- oesophagus
- major systemic blood vessels
What structures does the anterior mediastinum contain?
just the thymus gland :(
What structures does the middle mediastinum contain? (4)
- pericardium
- heart
- origins of great blood vessels
- nerves and smaller vessels
What structures does the posterior mediastinum contain? (3)
- oesophagus
- descending aorta
- thoracic duct (major lymphatic vessel)
What is the name of the inferior surface of the heart and what is it in contact with?
- diaphragmatic surface
- in contact with diaphragm via the pericardium
- projects from base of heart towards apex
What is the name of the anterior face of the heart and what is it orientated towards?
- sternocostal
- orientated towards anterior thoracic cage (sternum and ribs) and costal cartilage
- some parts have contact with pleura and lungs
What is the right pulmonary surface of the heart in contact with?
right pleura and lung
What is the left pulmonary surface of the heart in contact with?
left pleura and lung
Where do the base of the heart and the apex face?
- base faces posteriorly
- apex points forwards and downwards to the left
What does the base of the heart contain?
- left atrium
- pulmonary veins
- part of right atrium
- parts of SVC and IVC
What acts as a landmark to divide the base of the heart from the inferior surface?
coronary sinus
What does the anterior surface of the heart consist of? (4)
- right ventricle
- partially the right atrium
- partially the left ventricle
- roots of vessels entering and exiting the heart
What does the inferior surface of the heart consist of? (3)
- left ventricle including apex
- small portion of right ventricle
- coronary vessels (including posterior interventricular groove)
What are the left and right pulmonary surfaces made up of?
LEFT
- mainly left ventricle
- partially left atrium
RIGHT
- mainly right atrium
What does the heart’s pulmonary surface do to the lungs?
forms a cardiac impression on the medial surface of the lungs
What is the apex of the heart a part of and where is it located?
- part of the inferolateral portion of the left ventricle
- lies deep to the 5th intercostal space along the midclavicular line
What is the clinical importance of the apex?
- palpating the apex beat: it is the outermost and lowermost palpable cardiac impulse on the chest wall
- a displaced apex beat may indicate possible pathology e.g. cardiomegaly (enlarged heart) apex beat will be displaced more towards the axilla
What do sulci/ grooves of the heart do?
- structures that separate the chambers of the heart that internally create impressions in the external surface of the heart
- provide external demarcations that correspond to the internal partitions that divide the heart into its chambers
- creates a passageway for the coronary arteries and veins and their main branches
What are the three main sulci?
- coronary sulcus (atrioventricular sulcus)
- anterior interventricular sulcus
- posterior interventricular sulcus
What are the components of the pericardium?
- fibrous pericardium (outer)
- serous pericardium (inner)
- parietal layer (lines the fibrous pericardium)
- visceral layer (or epicardium) lines the heart itself
- these two layers are continuous with one another
What is the function of the pericardial cavity?
- potential space between serous layers which contains approx 25ml of pericardial fluid
- lubricates the layers and allows movement of the heart
Describe the fibrous pericardium and its attachments
- tough, connective tissue layer which is continuous with the outer layer of the blood vessels (tunica adventitia)
- attached anteriorly to the sternum by sternopericardial ligaments
- attached inferiorly to the diaphragm by pericardiacophrenic ligaments
What does the toughness of the fibrous pericardium do?
limits how much the heart can distend (stretch)
What is pericardial effusion?
fluid (including blood) build up in the pericardial sac
the pericardial activity should only contain small amount of serous fluid
What can pericardial effusion arise from?
- aortic aneurysms
- heart attacks
- penetrating injuries (most common)
- puts pressure on heart and hence heart functions impaired
In extreme cases what can pericardial effusion lead to, what are the symptoms and what is the treatment?
- cardiac tamponade
- when fluid accumulates too fast, increases pericardial pressure and compresses heart
- leads to rapid breathing and shortness of breath, sharp stabbing chest pains and cyanosis
- treatment is pericardial tap/ pericardiocentesis
What do the two pumps of the heart do and what are they separated into?
- left pump receives oxygenated blood from lungs and sends it to body
- right pump receives deoxygenated blood from body and sends it to lungs
- divided into atria and ventricles, separated by valves
What are the muscular septa in the heart and what do they separate?
- interatrial septum separates left and right atria
- interventricular septa separates left and right ventricles
How does blood pass through chambers? (simple answer)
veins (pulmonary or vena cava) –> atria –> ventricles
Why do atria have thinner walls than ventricles?
blood is not pumped far
What has a thicker wall out of the ventricles and why?
left ventricle as it must pump blood further than the right
What are the right side of the heart and left side known as?
- right side is pulmonary circuit (deoxygenated blood from body sent to lungs for oxygen)
- left side is systematic circuit (oxygenated blood from lungs sent to rest of body)
How does blood flow through the heart? (long answer)
- right atrium collects deoxygenated blood from body via SVC, IVC and coronary sinus
- right atrium contracts to pass blood through right AV valve/ tricuspid valve into right ventricle
- right ventricle contracts and blood passes through semi lunar valves at the entrance of the pulmonary trunk and goes to lungs to be oxygenated
- left atrium receives oxygenated blood from lungs via the four pulmonary veins
- left atrium contracts to pass blood through the left AV valve/ bicuspid valve into left ventricle
- left ventricle contracts and blood passes through semilunar valves at the entrance of the aorta as it continues towards the rest of the body
