Anatomy of the Heart Flashcards
What structure surrounds the heart?
Pericardium
What are the layers of the pericardium?
- Fibrous
- Serous
- parietal
- visceral
What are the functions of the fibrous pericardium?
Tough outer sac that functions to protect the heart from over expanding
e.g. if you went out running, and there is a lot of venous blood returning to the heart this protects it from over expanding)
Describe the two layers of the serous pericardium?
The Serous Pericardium lies internal to this fibrous layer and is made up of 2 layers
The parietal layer (outer) is adherent to the fibrous pericardium and is quite thin.
This is continuous with the second layer known as the visceral layer (as it is in contact with the organ/heart).
What is betweent the serous layers?
Serous fluid
What is the function of serous fluid?
serous fluid enables the heart to beat in a relatively frictionless environment → a lubricant for the heart
What are the 3 layers of the heart wall
- Epicardium
- Myocardium
- Endocardium
What is the epicardium?
Same as the visceral pericardium (the serous pericardium layer on top of the surface of the heart)
What is the myocardium?
The myocardium is the muscular layer of the heart wall
This is the layer of the heart wall that contracts to expel blood from thevarious chambers of the heart
What is the endocardium
The endocardium is the innermost layer of the heart and functions as an internal lining for the heart
This layer is continuous with the endothelium of blood vessels
What are the important features of the Right Atrium?
-
Fosa ovalis
- During foetal development, this fossa was in fact a foramen (an actual hole) that allowed oxygenated blood from the placenta to pass through the vena cava straight into the left atrium to bypass the babies currently non-functioning lungs
-
Coronary Sinus
- This is the opening where the venous blood from the heart cornary veins enters the RA
-
Pectinate muscles
- The muscles of the atrial wall
- Tricuspid Valve
This is an opening that connects the RA to the RV
What are distinguishing features of the Right Ventricle?
-
Trabeculae carnae
- This is the musculature of the right ventricle
-
Tricuspid Valve
- Tri as it has 3 cusps (septal, anterior, posterior
-
Chordae tendineae (tendinous chords)
- Chord like tendons which attach distally form the Tricuspid valve to the papillary muscles.
-
Pulmonary valve
- Lies between the RV and pulmonary trunk
What are distinguishing features of the Left Atrium?
-
Pulmonary veins
- There are 4 of these veins; 2 coming from the left, 2 coming from the right
- These are the vessels through which the oxygenated blood is travelling through on its way back into the heart
-
Bicuspid valve (mitral valve)
- The valve between the left atrium and left ventricle
What are the distinguishing features of the Left Ventricle?
- Bi-cuspid valve (mitral valve)
-
Chordae tendineae
- Attach to the end of the cusps. These attach distally to the papillary muscles
-
Trabeculae carneae
- Musculature of the ventricle
-
Aortic Valve
- Sits at the base of the aorta
What is the function of the septomarginal trabelucae?
The septomarginal trabecula (also referred to as the moderator band) is a special trabeculae carnae that conducts electric currents from the septum to the anterior papillary muscles
More direct route as opposed to going all around the ventricle.
What are the two types of heart valves?
- Atrioventricular (between atria and ventricles)
- Semi lunar (between ventricles and great vessels)
What are the two atriventricular valves?
- Tricuspid (RA/RV)
- Mitral (LA/LV)
- Aka bicuspid
How do the AV valves close?
- Ventricles contract
- Blood pushed backwards into cusps
- Cusps fill and force the valve shut
Why are the AV valves “active”?
When the ventricles contract, the wave of depolarisation travels to the papillary muscles causing them to simultaneously contract
Their contraction tightens the chordae tendineae, ensuring the valves don’t shoot all the way back into the atrium, and the valve is closed and blood is forced out the pulmonary or aortic valves
How do the semilunar valves close?
- Ventricular diastole
- Pressure(ventricle) < Pressure(GreatVessels)
- Blood flows backwards, towards heart
- Sinuses fill
- Forces cusps shut
Unlike AV valves this is passive
What is the difference between Systole and Diastole?
- Systole
- Ventricle contracts
- AV closed
- Semilunar open
- Diastole
- Ventricle relaxed
- AV open
- Semilunar closed
Label the braches of the anterior cornoary arteries
Label the branches of the posterior coronary arteries
Label the coronary veins
Small cardiac vein:
- anterior surface of the heart
- Passes around the right side of the heart to join the coronary sinus
- It accompanies the right coronary artery
The middle cardiac vein:
- Drains the posterior aspect of the heart
- It accompanies the posterior interventricular artery
The great cardiac vein:
- Originates at the apex of the heart
- It accompanies the circumflex branch of the left coronary artery in the anterior interventricular groove
Where do that coronary veins drain?
Coronary sinus → RA
Describe the innervation of the heart
- Parasympathetic - vagus (CN X)
- Sympathetic - T1-5
Describe the lymphatic drainage of the heart?
Lymph drains into the:
- Brachiocephalic nodes
- Tracheobronchial nodes
Ultimately drains to the left brachiocephalic vein
Describe the histology of the epicardium
Epicardium = visceral pericardium
- Comprises of a single layer of cells
- Underlying the epicardium is fat and connective tissue
- Amongst the connective tissue are the coronary vessels
Describe the histology of the myocardium
- Thickest layer consisting of cardiac myocytes
- These fibres will contract to expel blood from the chambers of the heart
- Atrial walls are thin, ventricular walls are thick, but they all have this layer of muscle
What are the 3 layers of blood vessel?
- Tunica intima
- Tunica media
- Tunica adventitia
Name 4 features of cardiac myocytes
- Intercalated discs allow for electrical conduction between adjacent cells
- Branching fibres allow electrical impulses to travel from one cardiomyocytes to 2 or more adjacent cells (arrows)
- Single central nucleus, like smooth muscle cells
- Striated like skeletal muscles (due to precise alignment of A bands and I bands within the sarcomeres)
What is found in the tunica intima?
- Thin endothelial layer
- Few SM fibres
What is found in the tunica media?
- Very thick layer of a lot of smooth muscle cells
- Abundant extracellular matrix- collagen, proteoglycans, elastin
What is found in the tunica adventitia?
- CT, fibroblasts, mast cells etc.
- Nerves and blood vessels
