Lecture 1 - The Heart Part 1 Flashcards
Describe the orientation of the heart in the chest
Take your right fist and put it in front of the middle of your chest, rotate it to the left and tilt the top back
The Apex sits in the left 5th intercostal space mid clavicular line (L5icsmcl)
The right atrium sits at the 4 the intercostal space on the right sternal edge (4icsRSE)
How do you know if a heart is enlarged?
The portion of the diaphragm that the heart sits on has to be 50% of the lateral distance of the diaphragm in inspiration
(Yellow must be 50% of the red line)
What is the most posterior part of the cardiac silhouette?
Left atrium
Label this
Describe the location and structure of the atrium proper, musculi pectinati and the sinus of venae cavae
The atrium proper includes the sac like structures on the anterior surface (auricles), these are a portion of the atrial chamber. These structures are derived from the primitive atrium.
Within the atrium proper are the musculi pectinati. This is a mesh work of fibres on the surface, indicating that the muscle fibres of the cardiac wall run in many directions.
The smmoth surface on the inside of the wall of the right atrium is the sinus venae cavae - embryologically derived from sinus venosus.
The atrium proper and the sinus venae cavae are seperated by the crista terminalis - which forms a distinct ine where musculi pectinati muscle stops and then bacomes smooth - use to this to differenatiate between the two regions
What happens in the musculi pectinati if the blood isn’t being pumped properly?
Blood can stagnate in the mesh like structure of musculi pectinati (e.g. in AF)
The clots can break off and embolise into the pulmonary or systemic circuit
Describe the fossa ovalis
The fossa ovalis is an oval shaped structure which is embrylogically derived from the foramen ovale. In utero, this was an opening from the right to left atrium to allow oxygen rich blood arriving from the placenta to get shunted to the left side of the heart. (since oxygenated blood arrives on right side in utero).
During birth the foramen ovali closes over and fibroses due to muscle contraction.
How does blood arrive to the right atrium?
- Superior vena cava: Brings back blood from head, neck and chest
- Inferior vena cava: Brings blood back from structures below the diaphragm
- Coronary sinus: Brings blood back from the coronary circulation of the heart
What three types of cusps make up the tricuspid valve?
And what three make up the pulmonary semilunar valve?
Tricuspid: Anterior, septal and posterior cusp (attached to anterior, septal and posterior papillary muscles via chordae tendineae)
Pulmonary valve: Anterior semilunar cusp, right semilunar cusp, left semilunar cusp
What is the role of the papillary muscles?
For each leaflet there are papillary muscles in the ventricular wall that attach to them via chordae tendineae. Early in ventricular systole these pre-tenion the chordae tendineae, these muscles stop the valves from slamming shut
When the right ventricle contracts, causing the ventricular pressure to be greater than the pulmonary trunk pressure, the semilunar valves are pushed open. When this happens blood rises up and passes through what?
Conus arteriosus/ infundibulum/ RV outflow tract
This is a cone like structure that directs blood towards the pulmonary valves.
Label this
How is blood delivered to the left atrium?
Via 4 pulmonary veins (carrying oxygenated blood)
- on the right there are right superior and right inferior pulmonary veins
- on the left there are left superior and left inferior pulmonary veins
What are the two leaflets of the mitral valve?
Anterior leaflet and posterior leaflet (attached to anterior and posterior papillary muscle)
The bundles of muscles that confer contraction in the right and left ventricles are the trabeculae carnae.
(Musculi pectinati are found in the right atrium and atrial appendages of the heart)
Label this
How can you tell which semilunar valve this is?
This is the pulmonary valve.
There are no coronary arteries comming off. On the aortic valve there are coronary arteries branching off above two of the three leaflets.
Describe the lamina fibrosa, lamina ventricularis and lamina spongiosa
Lamina fibrosa - This is a fibrotic surface made mostly of collagen, this maintains the shape of the leaflet.
Lamina ventricularis - this has alot of elastic tissue. When the leaflets are pushed against the side walls during ejection, the elastic tissue gets stretched, and when the pressure falls the elastic recoils and this helps close the valves.
Lamina spongiosa - This is a soft layer in the middle
At the end of the leaflet there is a large nodule, this is a weighted bit of connective tissue which helps close the valve as it falls to the centre in diastole
Describe how the LCA and RCA branch
The RCA comes from above the right cusp of the aortic semilunar valve.
The LCA comes from above the left cusp of the aortic semilunar valve. The LCA then branches into a vessel that goes to the anterior surface (left anterior descending artery), and one that runs around posteriorly and circumflexes the left margin (circumflex coronary artery).
Once the blood has supplied the heart it drains back into the right atrium from the coronary sinus (delivers venous drainage from heart back into right atrium)
For the innervation of the heart, what is the plexus that forms at the base of the heart, and what fibres are apart of it?
The superior plexus forms at the base of the heart, and consists of both sympathetic and parasymapthetic fibres.
A deep plexus also forms on the trachea
Why do heart attacks/ or other heart associated conditions cause somatic pain in the center of the chest, or left arm?
The cardiac plexus sends visceral sensory fibres through the sympathetic chain at the level of T1 to T4.
The visceral sensory fibres mix with the somatic sensory fibres (Which innervate the dermatones in the pic below). At the dorsal interneuron the signal from the visceral sensory and somatic snesory neurons are mixed together, causing us to percieve heart pain as a somatic sensation.
So, when a patient gets sensory input from the heart, it’s percieved at musclar chest and arm pain - this is referred pain.
How is jaw, neck and shoulder tip pain caused from heart associated problems?
When the visceral input comes from the diaphragm or the pericardial sac, the nerves enter the spinal cord folliwing the path of the phrenic nerve (C3-C5 level) - this causes somatic sensation in the neck, shoulder and jaw
e.g. if someone gets infection/inflammation of their pericardium (pericarditis), they may get referred sensation in their jaw, neck and shoulder tip.
If the heart attack is big enough, they can get referred pain in the three areas stated before, and also centrally in the chest and down the left arm
