Resp + Cardio PST Flashcards
Describe the epicardium of the ventricle.
Outer layer of mesothelium, called visceral pericardium, then epicardial connective tissue containing:
- collagen
- fat
- nerves
- blood vessels
- lymphatics
Describe the myocardium of the ventricle.
Cardiac myocytes with blood vessels and fine connective tissue
Describe the endocardium of the ventricle.
Lined with endothelium, with endocardial connective tissue containing elastin and collagen fibres and some smooth muscle fibres underneath.
Conduction fibres are also found here but are difficult to see on slides.
What is the mitral valve leaflet made of?
Outer layer of endocardium with a dense fibrous connective tissue core, containing collagen and elastin fibres, continuous with the annulus fibrosis.
Annulus fibrosis
Fibrous rings of the heart
What is the difference between the atrial and ventricular surfaces of the mitral valve?
The atrial surface is smooth but irregular which helps the flaps to close and maintain a tight seal. The ventricular surface is a tight weave of collagen strands to prevent regurgitation.
Cells in the mitral valve leaflet
Collagen fibres Elastin fibres Cardiac muscle fibres Myofibroblasts Macrophages
The cardiac muscle of the atrium does not merge with the muscle of the ventricle. What separates the two bodies of muscle?
The fibrous skeleton
What are the chordae tendineae made of?
80% collagen, 20% elastin and endothelial cells
Where would you find purkinje fibres?
Between the endocardium and myocardium (subendocardial layer)
Running through the moderator band
What are some features that are characteristic of purkinje fibres?
Cytoplasm rich in glycogen and mitochondria
Fewer myofibrils, found at the periphery
One or two central nuclei
Where do Purkinje fibres originate?
The atrioventricular node
Which part of the myocardium do purkinje fibres supply first?
The papillary muscles, followed by the ventricular wall.
This is because the papillary muscles need to activate to contract the chordae tendineae which push the inlet valves closed so that the ventricles can go through isovolumetric contraction before ejection, which would utilise the ventricular wall.
What is the main component of the aortic valve leaflet?
Collagen
What is the difference between the ventricular and aortic surfaces of the aortic valve?
The ventricular surface consists of mainly elastin whereas the aortic surface consists of mainly collagen.
This is because the elastin needs to be able to stretch and recoil as the valve opens and closes. The collagen provides structure to the valve and prevents regurgitation.
What are the three layers of the aortic valve and what are they predominantly made of?
Lamina fibrosa - collagen
Lamina spongiosa - GAGs and interstitial cells
Lamina ventricularis - elastin
What would a muscular artery look like on a histological slide?
Very thin tunica intima with even thinner subendothelial layer and a prominent internal elastic lamina.
Thick tunica media with up to 40 layers of prominent smooth mucsle cells, intermingled with a varaible number of elastic lamellae. External elastic lamina may be present in large muscular arteries.
Thinner tunica adventitia consisting of connective tissue, lymphatic capillaries, vasa vasorum and autonomic nerves.
What is the mean blood pressure of a muscular artery in a standing adult?
85 - 95 mmHg
What colour and arrangement do the three fibres in the tunica media have?
Smooth muscle: layered, stained dark pink with very dark nuclei, concentrically arranged
Elastic fibres: sparse and squiggly. In the uni slide they’re stained black, but they often don’t pick up colour.
Collagen fibres: sparse between smooth msucle cells. Both collagen and elastin run longitudinally.
What does the internal elastic lamina look like in a muscular artery?
Prominent and squiggly, forms a border between the thin intima and the thick media. This is only applicable in death, where there is no pressure in the vessel. In life, when the pressure is high, the IEL wouldn’t be squiggly because it would be stretch out.
What is the mean blood pressure of a large vein in a standing adult?
3 mmHg (approx)
IEL in veins
It’s present, but very thin and unlikely to be seen.
How do valves originate?
They are infoldings of the tunica intima that project into the lumen to prevent backflow of blood.
What is the thickest layer in a large vein?
The tunica adventitia, although the tunica intima is also well-developed.