7 structure of the heart Flashcards
Where does the heart lie?
behind the sternum in the mediastinum. behind ribs 2-5.
Where is the apex of the heart located?
Behind the 5th rib along the midclavicular line
What protects the heart?
- ribs
- sternum
- fibrous periacardum
What is the job of the fibrous pericardium
- tough unstretchy bag that stops the heart from over filling
- attached to the diaphragm and fused to the great vessels
- to anchor the heart in place
What is the structure of the fibrous pericardium?
- visceral and parietal pericardium
- parietal attached to the fibrous
- FP made of dense CT
- visceral (epicardium) attached to the heart wall
- serous fluid between the membranes makes movement frictionless
- gap between membranes = parietal cavity
What are the layers of the heart wall?
- epicardium/visceral pericardium
- myocardium
- endocardium
What does the epicardium contain?
lots of fat and blood vessels
What does the myocardium contain?
Lots of muscle - very thick layer
What does the endocardium consist of?
simple squamous endothelial cells for a smooth interior of the heart wall
What is another name for the visceral pericardium?
Epicardium
What is the name of the gap between the visceral and parietal pericardium?
Parietal cavity filled with serous fluid so two pericardial layers can glide on each other with no friction
Where is the bi cuspid valve?
between the left ventricle and atria
Where are the mitral valves?
between the ventricles and atria
Where are the semilunar valves?
Between the ventricles and aorta/pulmonary artery
Where are the atrioventricular valves?
where do you think, stupid?
Where is the tricuspid valve?
between the right ventricle and atrium
Talk about the action of the AV valves…
- conncted to papillary muscles by chordae tendinae
- as atria fills and pressure builds they open into ventricles
- as ventricles fill and pressure builds they are pushed back up and try to open into the atria causing eversion
- papillary muscles tense up and pull chordae tendinae tight preventing them from doing this
Whats eversion?
Flow of blood back into the atria due to backwards valves
Action of the semilunar valves:
- pushed open when ventricular pressure exceed aortic pressure
- during diastole they are pushed shut by blood pooling in the cusps
How are the coronary vessels fed?
- when systole the semilunar valves cover the entrance to them
- during diastole blood pooled on the cusp flows into the vessels to feed heart
- better this way coz otherwise vessels would be all squeezed up
What are the coronary vessels?
LCA -anterior inter ventricular vessel -circumflex RCA -posterior interventricular vessel -marginal
Which artery does the anterior interventricular vessel come off
LCA
Which artery does the posterior interventricular vessel come off
RCA
Where is the circumflex
vessel that wraps from the front of the hear round the back around aorta
Where do the coronary vessels drain to?
either into the coronary sinus and into the right atria or straight into the right atria
What happens if one of the coronary vessels is damaged?
Theres an anastamoses between the anterior and posterior interventricular vessel so they can share blood. otherwise tissue death and potential heart failure
How much blood per minute do the coronary vessels get?
250ml
What is the anterioventricular artery also known as?
The descending artery
What does the conducting system of he heart consist of?
Non contractile elements such as AVN SAN and bundle of his
-However they are adjacent to cells that do contract
Talk about contraction of the heart
- when one cell contracts all the cells around it do too so can cause contraction from a specific point
- starts at SAN –> spreads through atria but conat conduct through fibrous skeleton
- must continue through the AVN and down the R and L bundles of his to the apex
Foetal adaptations in circulatory system:
- Ductous venosus
- Ductus artereosis
- Foreman ovale
Flow of blood through the foetus:
- in through umbilical vein from placenta (o2 rich ish)
- either through the liver or ductous venousus to inferior vena cava (bringing blood from the legs to the heart) - into the heart where it all mixes through DA and FO
- out of the heart to body/lungs - some to feet and bladder but most back to placenta
Where is the Foreman ovale?
hole between right and left atria
Where is the ductous arteriosis?
linking pulmonary trunk to the aorta
What happens to the foreman ovale after birth
-left atrial pressure increases and causes it to slam shut producing the fossa ovale
What happens to the ductus venosus after birth?
it doesn’t get blood from the umbilical vein anymore so it shrivels up and becomes ligamentum venosum
What happens to the ductous arteriosis after birth?
the baby takes its first breath which expands the lungs causing the pressure in them to drop. this draws more oxygenated blood up towards them causing it to constrict and become ligamentum arteriosum
