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.
What would a large vein look like on a histological slide?
Well-developed tunica intima. Relatively thin tunica media, not many layers of smooth muscle but lots of connective tissue.
Thick adventitia with longitudinal bundles of smooth muscle and thick collagen fibres. Elastin fibres are also present in media and adventitia but they’re not arranged into lamella.
What are blood vessels that supply nerves called?
Vasa nervorum
What are atherosclerotic plaques made of?
Aggregated foam cells (macrophages that have eaten lipids), calcium and fibrin (which can form a cap)
Changes to a vessel wall when an atherosclerotic plaque is present
More rigid intima due to inflammation and invasion of lipoproteins
Thickened media due to scar tissue
Breakdown of IEL as plaque pushes through into the tunica media from the intima
Why is the core of an atherosclerotic lesion empty?
The plaque has a necrotic core because it cuts off blood supply to cells in it, which die and cause more inflammation. There are no longer living cells in the centre of this lesion.
Three ways plaques can cause a stroke
1) Thrombus forms on top of plaque, causing sudden occlusion of artery and ischaemia in the area.
2) Thrombus forms on top of plaque then embolises and lodges in a smaller vessel.
3) IEL and media are weakened causing arterial wall rupture. This can cause subarachnoid haemorrhage.
How does blood pressure vary in a healthy elastic artery?
120 - 80 mmHg
Diameter of aorta
About 22 mm (ascending) and 16 mm (descending)
Proportion of tunica intima in the aorta
20%
How is elastin arranged in the aorta?
Intima: one layer - the internal elastic lamina
Media: both elastic fibres and fenestrated elastic lamellae, concentrically arranged. Also external elastic lamina.
Adventitia: some elastin fibres but relatively underdeveloped
What do fenestrated sheets of elastin (lamellae) and elastic fibres look like on a histological slide?
Fenestrated sheets of elastin look like squiggly lines in longitudinal section and small broken up lines in transverse.
Elastic fibres look like long squiggly or curved lines in longitudinal section and small dots in transverse.
What vessels could be in the coronary sulcus of the heart?
Coronary sinus
Coronary veins
Coronary arteries
What features are characteristic of a lymphatic vessel?
Very thin wall of endothelial cells
Variable in diameter
Will contain proteins and other stain-loving material
Lack a clear cut separation between tunics
Don’t contain red blood cells
What is the epithelium of the anterior laryngeal pharynx?
Pseudostratified ciliated columnar epithelium with mucus glands